Document

424B5 1 cmps-2025prosuppfinal.htm 424B5 Document

Filed pursuant to Rule 424(b)(5)

Registration No. 333-285297

PROSPECTUS SUPPLEMENT

(To Prospectus dated May 7, 2025)

American Depositary Shares Representing 17,500,000 Ordinary Shares

Pre-Funded Warrants to Purchase up to 1,250,000 American Depositary Shares Representing 1,250,000 Ordinary Shares

American Depositary Shares Issuable Upon Exercise of the Pre-Funded Warrants

We are offering 17,500,000 American Depositary Shares, or ADSs, representing 17,500,000 ordinary shares, nominal value £0.008 per ordinary share and in lieu of ADSs, to certain institutional investors, pre-funded warrants to purchase 1,250,000 ADSs. Each pre-funded warrant is exercisable for one ADS representing one ordinary share at an exercise price of $0.0001 per share. Each ADS will be sold at a price of $8.00. Each pre-funded warrant will be sold at a price of $7.9999. The pre-funded warrants are immediately exercisable, subject to the limitations described in the section “Description of Securities We Are Offering”.

We refer to the ADSs and the pre-funded warrants representing ordinary shares issued in this offering, collectively, as the securities. This prospectus supplement also relates to the offering of the ADSs representing ordinary shares issuable upon exercise of the pre-funded warrants sold in this offering.

The ADSs may be evidenced by American Depositary Receipts, or ADRs. Our ADSs are listed on the Nasdaq Global Select Market under the symbol “CMPS.” On February 18, 2026, the last reported sale price of our ADSs on the Nasdaq Global Select Market was $8.45 per ADS. There is no established trading market for the pre-funded warrants, and we do not expect a market to develop. We do not intend to apply to list the pre-funded warrants on any securities exchange or other nationally recognized trading system. Without an active trading market, the liquidity of the pre-funded warrants will be limited.

Investing in our securities involves significant risks. These risks are described under the caption “Risk Factors” beginning on page S-9 of this prospectus supplement, as well as in the documents incorporated or deemed to be incorporated by reference into this prospectus supplement and the accompanying base prospectus.

We are a “smaller reporting company” as defined under the federal securities laws and, as such, have elected to comply with certain reduced public company reporting requirements for this prospectus supplement and the documents incorporated by reference herein and may elect to comply with reduced public company reporting requirements in future filings. See “Prospectus Supplement Summary-Implications of Being a Smaller Reporting Company.”


	PER ADS		PER PRE-FUNDED WARRANT		TOTAL
Offering price	$	8.0000	$	7.9999	$	149,999,875
Underwriting discounts and commissions(1)	$	0.4800	$	0.4800	$	8,999,993
Proceeds, before expenses, to COMPASS Pathways plc(2)	$	7.5200	$	7.5199	$	140,999,883

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(1)See the section titled “Underwriting” for additional information regarding compensation payable to the underwriters. We have agreed to reimburse the underwriters for certain expenses in connection with the offering.

(2)The above summary of offering proceeds does not give effect to any proceeds from the exercise of the pre-funded warrants being issued in this offering.

We granted the underwriters an option for a period of up to 30 days from the date of this prospectus supplement to purchase up to an additional 2,812,500 ADSs at the public offering price, less the underwriting discounts and commissions.

Neither the U.S. Securities and Exchange Commission nor any state securities commission or other regulatory body has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying base prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the securities against payment therefor on or about February 20, 2026.

Book Runners


Jefferies			TD Cowen			Cantor			Stifel

Lead Manager

H.C. Wainwright & Co.

The date of this prospectus supplement is February 18, 2026.

TABLE OF CONTENTS

Prospectus Supplement


			Page
ABOUT THIS PROSPECTUS SUPPLEMENT			S-1
PROSPECTUS SUPPLEMENT SUMMARY			S-3
THE OFFERING			S-7
RISK FACTORS			S-9
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS			S-16
USE OF PROCEEDS			S-19
DILUTION			S-20
DESCRIPTION OF SECURITIES WE ARE OFFERING			S-22
UNDERWRITING			S-24
MATERIAL TAX CONSIDERATIONS			S-32
LEGAL MATTERS			S-44
EXPERTS			S-44
WHERE YOU CAN FIND MORE INFORMATION			S-44
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE			S-45

Prospectus


			Page
ABOUT THIS PROSPECTUS			1
PROSPECTUS SUMMARY			3
RISK FACTORS			5
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS			6
SECURITIES WE MAY OFFER			9
DESCRIPTION OF SHARE CAPITAL AND ARTICLES OF ASSOCIATION			10
DIFFERENCES IN CORPORATE LAW			23
DESCRIPTION OF AMERICAN DEPOSITARY SHARES			31
DESCRIPTION OF DEBT SECURITIES			42
DESCRIPTION OF WARRANTS			55
DESCRIPTION OF UNITS			56
TAXATION			57
USE OF PROCEEDS			61
DIVIDEND POLICY			62
SELLING SECURITY HOLDERS			63
PLAN OF DISTRIBUTION			64
LEGAL MATTERS			67
EXPERTS			67
SERVICE OF PROCESS AND ENFORCEMENT OF LIABILITIES			68
WHERE YOU CAN FIND MORE INFORMATION			70
INCORPORATION BY REFERENCE			71

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ABOUT THIS PROSPECTUS SUPPLEMENT

This document is part of a “shelf” registration statement on Form S-3 (File No. 333-285297) that we filed with the Securities and Exchange Commission, or the SEC, which became effective on May 7, 2025 and is in two parts: (1) this prospectus supplement, including the documents incorporated by reference, which describes the specific details regarding this offering; and (2) the accompanying base prospectus dated May 7, 2025, including the documents incorporated by reference, which provides general information, some of which may apply to this offering. Generally, when we refer to this “prospectus,” we are referring to both documents combined. This prospectus supplement describes the terms of this offering of securities and also adds to and updates information contained in the accompanying base prospectus and the documents incorporated by reference into the accompanying base prospectus. If information in this prospectus supplement is inconsistent with the accompanying base prospectus, you should rely on this prospectus supplement.

This prospectus supplement relates to the offering of our securities. Before buying any of the securities that we are offering, we urge you to carefully read this prospectus supplement and the accompanying base prospectus, together with the information incorporated by reference herein and therein, as well as the additional information described under the headings “Where You Can Find More Information” and “Incorporation of Certain Information by Reference” and any free writing prospectus that we may authorize for use in connection with this offering. These documents contain important information that you should consider when making your investment decision.

We and the underwriters have not authorized anyone to provide any information or to make any representations other than those contained or incorporated by reference in this prospectus supplement, the base prospectus or in any free writing prospectus prepared by or on behalf of us or to which we have referred you to. We and the underwriters take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. This prospectus supplement and the base prospectus is an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference herein or in the accompanying base prospectus were made solely for the benefit of the parties to such agreement, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

You should assume that the information appearing in this prospectus supplement, the base prospectus, any documents incorporated by reference, and in any free writing prospectus that we have authorized for use in connection with this offering, is accurate only as of the date of those respective documents. Our business, financial condition, results of operations and prospects may have changed since those dates. You should read this prospectus supplement, the accompanying base prospectus, any documents incorporated by reference, and any free writing prospectus that we have authorized for use in connection with this offering, in their entirety before making an investment decision.

Unless otherwise stated, all references in this prospectus supplement or the accompanying base prospectus to the “Company,” “Compass,” “Compass Pathways,” “we,” “us,” and “our,” except where the context requires otherwise, refer to COMPASS Pathways plc and its consolidated subsidiaries.

We own various trademark registrations and applications, and unregistered trademarks, including Compass, Compass Pathways, COMPASS and COMPASS PATHWAYS and our corporate logo. All other trade names, trademarks and service marks of other companies appearing in this prospectus supplement are the property of their respective holders. Solely for convenience, the trademarks and trade names in this prospectus supplement may be referred to without the ®, ™ or RTM symbols, but such references should not be construed as any indicator that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto. We do not intend to use or display other companies’ trademarks and trade names to imply a relationship with, or endorsement or sponsorship of us by, any other companies.

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This prospectus supplement contains or incorporates industry, market and competitive position data that are based on general and industry publications, surveys and studies conducted by third parties, some of which may not be publicly available, and our own internal estimates and research. We have obtained these third-party publications, surveys and studies from sources that we believe to be reliable, and we are responsible for the accuracy of such sources, but we do not guarantee the accuracy and completeness of such information. These data involve a number of assumptions and limitations and contain projections and estimates of the future performance of the industries in which we operate that are subject to a high degree of uncertainty. We caution you not to give undue weight to such projections, assumptions and estimates.

No action is being taken in any jurisdiction outside the United States to permit a public offering of the securities or possession or distribution of this prospectus supplement or the accompanying base prospectus in that jurisdiction. Persons who come into possession of this prospectus supplement or the accompanying base prospectus in jurisdictions outside the United States are required to inform themselves about and to observe any restrictions as to this offering and the distribution of this prospectus supplement or the accompanying base prospectus applicable to that jurisdiction.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights certain information about us, this offering and selected information contained elsewhere in this prospectus supplement and in the documents incorporated by reference herein or therein. This summary does not contain all of the information that you should consider before making an investment in our securities. You should read this entire prospectus supplement and the accompanying base prospectus carefully, especially the risks of investing in our securities discussed under “Risk Factors” beginning on page S-9 of this prospectus supplement, along with our consolidated financial statements and notes to those consolidated financial statements and the other information incorporated by reference in this prospectus supplement, the accompanying base prospectus and any related free writing prospectus, before making an investment decision. This prospectus supplement may add to, update or change information in the accompanying base prospectus.

Overview

We are a biotechnology company dedicated to accelerating patient access to evidence-based innovation in mental health. We are motivated by the need to find better ways to help and empower people with serious mental health conditions who are not helped by existing treatments. We are pioneering a new paradigm for treating mental health conditions focused on rapid and durable responses through the development of our investigational COMP360 psilocybin treatment, potentially a first in class treatment. COMP360 is our proprietary psilocybin formulation that includes our pharmaceutical-grade polymorphic crystalline psilocybin, optimized for stability and purity.

We believe that our COMP360 psilocybin treatment could offer a new approach to treatment of serious mental health conditions, including treatment-resistant depression, or TRD, which is a subset of major depressive disorder, post-traumatic stress disorder, or PTSD, and potentially many other serious mental health conditions.

Our initial focus is on TRD, comprising patients who are inadequately served by current treatment options. In 2018, we received Breakthrough Therapy designation from the U.S. Food and Drug Administration, the FDA, for COMP360 for the treatment of TRD. In November 2021, we announced positive top-line results from our Phase 2b clinical trial evaluating COMP360 for the treatment of TRD. On November 3, 2022, The New England Journal of Medicine published the positive results from our Phase 2b trial. This is the largest, randomized, controlled, double-blind psilocybin treatment clinical trial completed to date. The objective of the Phase 2b study was to evaluate the efficacy and safety of a single dose of investigational COMP360 psilocybin (25mg or 10mg), compared to 1mg, in patients with TRD. The trial achieved its primary endpoint for the 25mg dose, with a 25mg dose of COMP360 demonstrating a statistically significant and clinically relevant treatment difference against the 1mg dose of COMP360 in reducing depressive symptom severity after three weeks.

In 2025, we completed enrollment for each of the two pivotal trials in our Phase 3 program evaluating our COMP360 psilocybin treatment in TRD. Each of the two pivotal trials has a long-term follow-up component. The pivotal program design is as follows:

•Pivotal trial 1 (COMP005) (n=258): a single dose (25mg) monotherapy compared with placebo.

•Pivotal trial 2 (COMP006) (n= 581): a fixed repeat dose monotherapy using three dose arms: 25mg, 10mg and 1mg. This trial is designed to investigate whether a second dose can increase therapeutic response.

•The primary endpoint in both pivotal trials is the change from baseline in the MADRS (Montgomery-Åsberg Depression Rating Scale) total score at week 6.

In June 2025, we reported that the first pivotal trial, the COMP005 trial, achieved its primary endpoint, with a single 25mg dose of COMP360 versus placebo demonstrating a highly statistically significant reduction in symptom severity as measured by MADRS with a p-value of p<0.001 and a clinically meaningful difference of -3.6 in change at six weeks. The COMP005 trial is on-going and is comprised of three parts: Part A, which concluded during the second quarter of 2025, and was blinded through 6 weeks; Part B, which remains blinded through week 26; and Part C, which contains an open-label treatment part from week 26 to 52.

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In September 2025, we met with the FDA, and as part of that meeting discussed our NDA submission strategy. Based on such discussions, we plan to submit a proposal for rolling submission and formal request for rolling review of our NDA to the FDA.

Beyond TRD, we have been exploring other indications, including PTSD. In May 2024, we completed and announced top-line results from our open label Phase 2 study to assess the safety and tolerability of COMP360 psilocybin treatment in participants with PTSD, as a result of trauma experienced as adults. In line with the study design, the study enrolled 22 participants who were monitored for a 12-week period post dosing. The study met its primary safety endpoint and available secondary efficacy endpoints. Study observations included meaningful and sustained symptom improvement from baseline in mean CAPS-5 total score, a measure of disease severity, and in Sheehan Disability Scale (SDS) score, a measure of functional impairment in daily life. Administration of COMP360 was well-tolerated, with a safety profile consistent with previous studies of COMP360. In September 2025, the results of this study were published in the Journal of Psychopharmacology.

Based on the data from this trial, we determined to advance development of COMP360 for PTSD and finalized the design of a Phase 2b/3 clinical trial in PTSD. In January 2026, the FDA accepted our IND application for COMP360 in PTSD, enabling the initiation of a Phase 2b/3 (COMP202) clinical trial in patients living with PTSD.

Recent Developments

Phase 3 Program Data Read-Out

On February 17, 2026, we announced the successful achievement of the primary endpoint in our ongoing Phase 3 COMP006 trial, the second of two Phase 3 trials, which is evaluating two fixed doses of COMP360, a synthetic, proprietary formulation of psilocybin, for TRD. The primary endpoint was the difference in change from baseline in the MADRS scores between the 25 mg and 1 mg groups at Week 6. Two fixed doses – administered 3 weeks apart – of COMP360 25 mg versus 1 mg demonstrated a highly statistically significant reduction in symptom severity with a p-value of <0.001 and a clinically meaningful difference of -3.8 points in change at the primary endpoint.

Across COMP005 and COMP006 to date, COMP360 is demonstrating a generally well-tolerated and safe profile, with treatment-emergent adverse events (TEAEs) being mild or moderate in severity, and the vast majority resolving within 24 hours. The data confirms a statistically significant rapid onset from the day following administration and maintained at all measured timepoints through Week 6 in both clinical trials in the 25 mg arm. COMP005 suggests that participants who demonstrated a clinically meaningful reduction in MADRS maintained durable treatment effect at least through Week 26, after just one or two doses. Retreatment with a second dose was well-tolerated, with a consistent safety profile.

We have submitted a request for a meeting with the FDA, to discuss a rolling submission and review.

Key Findings

Efficacy Profile

COMP005

•Primary endpoint of Part A (previously disclosed in June 2025): Single dose of COMP360 25 mg versus placebo with a mean treatment difference of -3.6 points, 95% CI [-5.7, -1.5]; p<0.001 at Week 64

•For participants who had a clinically meaningful reduction in MADRS (≥ 25%), a statistically significant rapid onset from the day following administration was maintained at all measured timepoints through Week 6 in the 25 mg arm

•25% of participants in the 25 mg arm achieved a clinically meaningful reduction in MADRS (≥ 25%) at Week 6 with durability lasting out through 26 weeks after just one or two doses of 25 mg

•Over 40% of those who achieved a clinically meaningful reduction in MADRS but had not remitted by 6 weeks went into remission after the second dose in Part B

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COMP006

•Primary endpoint of Part A: Two doses of COMP360 25 mg versus 1 mg with a mean treatment difference of -3.8 points, 95% CI [-5.8, -1.8]; p<0.001 at Week 6

•39% of participants in the 25 mg arm achieved a clinically meaningful reduction in MADRS (≥ 25%) at Week 6

•For participants who achieved a clinically meaningful reduction in MADRS (≥ 25%), a statistically significant rapid onset from the day following administration was maintained at all measured timepoints through Week 6 in the 25 mg arm

•The 26-week data (Part B) from COMP006 is expected in early Q3 2026

Safety Profile

COMP005

In the 25 mg arm, (Part A and B):

•Most TEAEs occurred on the days of study drug administration (66%), with the vast majority (88%) resolving within a day

•Most common TEAEs reported were headache, nausea and visual hallucination

•There were 11 treatment-emergent serious adverse events (SAEs) from 8 participants (5%) overall

COMP006

In the 25 mg arm (Part A):

•Most TEAEs occurred on the days of study drug administration (73%) with the vast majority (83%) resolving within a day

•Most common TEAEs were headache, nausea, anxiety and visual hallucination

•There were 6 treatment-emergent serious adverse events (SAEs) from 6 participants (2%) overall

Across both trials, for the data available to date, the rate for SAE suicidal ideation was less than 1%. There was only one event of SAE suicidal behavior, which occurred in the 1 mg arm in COMP006.

The COMP360 program aims to evaluate the safety and efficacy of COMP360 psilocybin, a synthetic, proprietary formulation of psilocybin under investigation for difficult-to-treat mental health conditions. There are two pivotal Phase 3 trials, COMP005 and COMP006, evaluating the efficacy of COMP360 for TRD.

Certain Unaudited Preliminary Financial Results

We estimate that our cash and cash equivalents were approximately $149.6 million as of December 31, 2025. The foregoing information is based on preliminary unaudited information and management estimates as of and for the year ended December 31, 2025, is not a comprehensive statement of our financial results, and is subject to completion of our financial closing procedures. During our financial closing process our estimates can differ materially from our initial estimates presented herein based on our receipt of updated information. See the sections entitled “Risk Factors” and “Special Note Regarding Forward-Looking Statements” in this prospectus supplement and the documents incorporated by reference herein, for a discussion of certain factors that could result in differences between these preliminary unaudited estimates and the actual results.

These preliminary unaudited estimates of our cash, and cash equivalents as of December 31, 2025 have been prepared by and are the responsibility of management. PricewaterhouseCoopers LLP has not audited, reviewed, examined, compiled, nor applied agreed-upon procedures with respect to such preliminary estimates and accordingly

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does not express an opinion or any other form of assurance with respect thereto. The report of our independent registered public accounting firm incorporated by reference into this document relates to our previously issued financial statements. It does not extend to the preliminary financial information and should not be read to do so. It is possible that we or our independent registered public accounting firm may identify items that require us to make adjustments to the financial information set forth above. These estimates should not be viewed as a substitute for financial statements prepared in accordance with accounting principles generally accepted in the United States and they are not necessarily indicative of the results to be achieved in any future period. Accordingly, you should not draw any conclusions based on the foregoing estimates and should not place undue reliance on these preliminary estimates. We assume no duty to update these preliminary estimates, except as required by law. Complete results as of December 31, 2025 will be included in our Annual Report on Form 10-K for the year ended December 31, 2025, the 2025 Form 10-K.

Company Information

Our principal executive office is located at 33 Broadwick Street, London W1F 0DQ, United Kingdom, and our telephone number is +1 (716) 676-6461. Our website address is www.compasspathways.com. We do not incorporate the information on or accessible through our website into this prospectus supplement, and you should not consider any information on, or that can be accessed through, our website as part of this prospectus supplement.

Implications of Being a Smaller Reporting Company

We are a “smaller reporting company” as defined in the Securities Exchange Act of 1934, as amended, or the Exchange Act. As a result, we may take advantage of certain of the scaled disclosures available to smaller reporting companies. These include, but are not limited to, reduced disclosure obligations regarding executive compensation and an exemption from the requirement to provide a compensation discussion and analysis describing compensation practices and procedures. As a smaller reporting company with annual revenues of less than $100.0 million and a non-accelerated filer, we are also not required to provide an attestation report on internal control over financial reporting issued by our independent registered public accounting firm. We will be able to take advantage of these scaled disclosures and exemptions for so long as (i) our voting and non-voting shares held by non-affiliates is less than $250.0 million measured on the last business day of our most recent second fiscal quarter or (ii) our annual revenue is less than $100.0 million during the most recently completed fiscal year and our voting and non-voting shares held by non-affiliates is less than $700.0 million measured on the last business day of our most recent second fiscal quarter.

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THE OFFERING


ADSs offered by us						17,500,000 ADSs representing 17,500,000 ordinary shares

Pre-funded warrants offered by us						We are also offering pre-funded warrants to purchase 1,250,000 ADSs representing 1,250,000 ordinary shares, in lieu of ADSs. Each pre-funded warrant is exercisable for one ADS representing one ordinary share. The purchase price of each pre-funded warrant is equal to the price at which an ADS is being sold in this offering, minus $0.0001 per share, and the exercise price of each pre-funded warrant is $0.0001 per share. The pre-funded warrants are exercisable immediately and may be exercised at any time until all of the pre-funded warrants are exercised in full. For additional information regarding the prefunded warrants, see “Description of Securities We Are Offering- Pre-Funded Warrants” below.

ADSs to be outstanding immediately after this offering						113,502,044 ADSs, assuming no exercise of any pre-funded warrants to be issued in this offering (or 116,314,544 ADSs if the underwriters exercise in full their option to purchase additional ADSs). Assuming all of the pre-funded warrants were immediately exercised, there would be 114,752,044 ADSs outstanding after this offering (or 117,564,544 ADSs if the underwriters exercise in full their option to purchase additional shares).

Ordinary shares (including ordinary shares represented by ADSs) to be outstanding immediately after this offering						113,502,044 ordinary shares, assuming no exercise of any pre-funded warrants to be issued in this offering (or 116,314,544 ordinary shares if the underwriters exercise in full their option to purchase additional ADSs). Assuming all of the pre-funded warrants were immediately exercised, there would be 114,752,044 ordinary shares outstanding after this offering (or 117,564,544 ordinary shares if the underwriters exercise in full their option to purchase additional ADSs).

Underwriters’ option						We have granted the underwriters a 30-day option to purchase up to an additional 2,812,500 ADSs from us at the public offering price, less underwriting discounts and commissions.

The ADSs						Each ADS represents one ordinary share, nominal value £0.008 per share. The depositary will be the holder of the ordinary shares represented by the ADSs, and purchasers in this offering will have the rights of an ADS holder or beneficial owner (as applicable) as provided in the Deposit Agreement, dated as of September 22, 2020, among us, the depositary and all holders and beneficial owners of ADSs issued thereunder, or the Deposit Agreement. To better understand the terms of our ADSs, you should carefully read the section in the accompanying base prospectus titled “Description of American Depositary Shares.” We also encourage you to read the Deposit Agreement, which is filed as an exhibit to our Annual Report on Form 10-K for the year ended December 31, 2024, or the Annual Report on Form 10-K, which is incorporated by reference into this prospectus supplement.

ADS depositary						Citibank, N.A.

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Custodian						Citibank, N.A. (London Branch)

Use of proceeds						We estimate that the net proceeds from this offering, after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us and excluding the proceeds, if any, from the exercise of the pre-funded warrants issued in this offering, will be approximately $140.5 We intend to use the net proceeds from this offering to fund our ongoing COMP005 and COMP006 Phase 3 trials, our Phase 2b/3 trial of COMP360 in post-traumatic stress disorder, acceleration of our commercial readiness activities, and for working capital and general corporate purposes. See “Use of Proceeds” for a more complete description of the intended use of proceeds from this offering.

Lock-ups						We and our executive officers and directors have agreed, subject to specified exceptions, not to sell, transfer or dispose of any ADSs, ordinary shares or similar securities for a period of 60 days after the date of this prospectus supplement. See “Underwriting” for more information.

Risk factors						Investing in our securities involves significant risks. You should read the section titled “Risk Factors” beginning on page S-9 of this prospectus supplement and other information included or incorporated by reference into this prospectus supplement and the accompanying base prospectus for a discussion of the factors you should carefully consider before deciding to purchase our securities.

The Nasdaq Global Select Market symbol						Our ADSs are listed under the symbol “CMPS.” We do not intend to list the pre-funded warrants on the Nasdaq Global Select Market, any other securities exchange or other nationally recognized trading system.

The total number of our ordinary shares (including ordinary shares represented by ADSs) to be outstanding after this offering is based on 96,002,044 of our ordinary shares outstanding as of September 30, 2025, and excludes:

•12,324,700 ordinary shares issuable upon exercise of warrants outstanding as of September 30, 2025, with an exercise price of $9.93 per share, or the PIPE Warrants;

•35,059,448 ordinary shares issuable upon exercise of warrants outstanding as of September 30, 2025, with an exercise price of $5.796 per share, or the ADS Warrants;

•8,700,000 ordinary shares issuable upon exercise of pre-funded warrants outstanding as of September 30, 2025, with an exercise price of $0.0001 per share, or the Pre-Funded Warrants;

•94,222 ordinary shares issuable upon exercise of warrants outstanding as of September 30, 2025, with an exercise price of $7.96 per share;

•7,991,809 ordinary shares issuable upon the exercise of options for ordinary shares outstanding as of September 30, 2025, with a weighted-average exercise price of $11.07 per share;

•770,652 ordinary shares issuable upon the vesting of unvested restricted share units outstanding as of September 30, 2025;

•an additional 2,697,219 ordinary shares that were available for future issuance under our 2020 Share Option and Incentive Plan, or 2020 Option Plan as of September 30, 2025; and

•an additional 546,402 ordinary shares that were available for future issuance under our Employee Share Purchase Plan, or ESPP, as of September 30, 2025.

Unless otherwise indicated, all information in this prospectus supplement reflects or assumes the following:

•no exercise of the outstanding stock options, warrants or pre-funded warrants described above;

•no settlement of the unvested restricted share units described above;

•no issuance of shares under our 2020 Option Plan or ESPP after September 30, 2025; and

•no exercise by the underwriters of their option to purchase additional ADSs in this offering.

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RISK FACTORS

Investing in our securities involves a high degree of risk. You should carefully consider the risks and uncertainties described below and the other information contained in this prospectus supplement, the accompanying base prospectus and documents incorporated by reference herein before making an investment decision, including the risks discussed in the section titled “Risk Factors” contained in our Quarterly Report on Form 10-Q for the three and nine months ended September 30, 2025 as filed with the SEC. The risks and uncertainties described below and incorporated by reference are not the only ones we face. Additional risks and uncertainties not presently known to us may also adversely affect our business. Our business, financial condition and/or results of operations could be materially and adversely affected if any of these risks occur, and as a result the trading price of our ADSs could decline and you could lose all or part of your investment.

This prospectus supplement also contains forward-looking statements that involve risks and uncertainties. See “Special Note Regarding Forward-Looking Statements.” Our actual results could differ materially and adversely from those anticipated in these forward-looking statements as a result of certain factors.

Risks Related to this Offering

If you purchase securities in the offering, you will experience substantial and immediate dilution.

If you purchase ADSs (or pre-funded warrants in lieu thereof) representing ordinary shares in this offering, you will experience immediate dilution in an amount equal to the difference between the purchase price for the ADS (or pre-funded warrant in lieu thereof) and our net tangible book value per ADS after giving effect to this offering. Based on the ADS offering price of $8.00 per ADS (or $7.9999 per pre-funded warrant in lieu thereof), after giving effect to this offering and after deducting underwriting discounts and commissions and estimated offering expenses payable by us, you will experience immediate dilution of $6.43 per ADS, representing the difference between the offering price and our as adjusted net tangible book value as of September 30, 2025. The exercise of the pre-funded warrants issued in this offering, outstanding warrants, outstanding options or vesting of restricted units will result in further dilution. For a further description of the dilution that you will experience immediately after the offering, see “Dilution.”

Future sales of our ADSs in the public market, or the perception that such sales could occur, could cause our ADSs price to fall.

The sale of a substantial number of our ADSs or other equity-related securities in the public markets, or the perception that such sales could occur, could depress the market price of ADSs and impair our ability to raise capital through the sale of additional equity securities. We may sell large quantities of our securities at any time pursuant to this prospectus supplement or in one or more separate offerings. For example, in February 2025, we entered into the Sales Agreement for an “at the market” offering with TD Securities (USA) LLC relating to ADSs having an aggregate offering price of up to $150.0 million. As of the date of this prospectus supplement, $150.0 million of ADSs remain available for sale under the Sales Agreement. We cannot predict the effect that future sales of ADSs or other equity-related securities would have on the market price of our ADSs. In addition, we have outstanding warrants to purchase an aggregate of 12,324,700 ADSs with an exercise price of $9.93 that are currently exercisable, warrants to purchase an aggregate of 94,222 ADSs with an exercise price of $7.96 that are currently exercisable, warrants to purchase an aggregate of 35,059,448 ADSs with an exercise price of $5.796 per ADS, which we may elect to force the exercise of if the closing price of our ADSs is above the warrant exercise price of $5.796 per ADS for at least three consecutive trading days, outstanding pre-funded warrants to purchase an aggregate of 8,700,000 ADSs with an exercise price of $0.0001 per ADS that are exercisable, outstanding options under our equity plans exercisable for and outstanding restricted share units settleable for our ordinary shares. To the extent that outstanding warrants, options or restricted share units have been or may be exercised or settled, as applicable, investors purchasing our securities in this offering may experience further dilution in the future. Furthermore, a significant portion of our total ordinary shares are eligible to be sold into the market, which could cause the market price of our ADS to drop significantly, even if our business is doing well.

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The market price of our ADSs has been and will likely continue to be volatile and you could lose all or part of your investment.

The market price of our ADSs has been and may continue to be highly volatile and could be subject to large fluctuations in response to the risk factors discussed in this section, and others beyond our control, including the following:

•positive or negative results of testing and clinical trials by us, strategic partners or competitors;

•positive or negative developments in the regulatory approval process for psychedelic-based compounds developed by us, strategic partners or competitors;

•timing of completion of our Phase 3 program and the time period during which results of our Phase 3 trials will become available;

•delays in entering into strategic relationships with respect to development or commercialization of our investigational COMP360 psilocybin treatment or any future therapeutic candidates;

•changes in our strategic focus and research and development priorities;

•entry into strategic relationships on terms that are not deemed to be favorable to us;

•technological innovations or commercial therapeutic introductions by competitors;

•changes in government regulations and healthcare payment systems;

•developments concerning proprietary rights, including patent and litigation matters;

•public concern relating to the commercial value or safety of our investigational COMP360 psilocybin treatment or any future therapeutic candidates;

•negative publicity or public perception of the use of psilocybin as a treatment for mental health conditions;

•reorganizations, restructurings, financings or other corporate transactions;

•publication of research reports or comments by securities or industry analysts;

•the trading volume of our ADSs on the Nasdaq Global Select Market;

•the exercise of the ADS Warrants and/or the PIPE Warrants, and the sale of the ADSs issuable upon exercise thereof;

•sales of our ADSs by us (including through the Sales Agreement), members of our senior management and directors or our significant shareholders or the anticipation that such sales may occur in the future;

•general market conditions in the pharmaceutical industry or in the economy as a whole;

•general economic, political, geopolitical and market conditions, including the recent fluctuations in inflation in the U.S., UK and Europe, the effects of announced or future tariff increases, and overall market volatility in the U.S. or the UK as a result of, among other factors, macroeconomic conditions and the ongoing war between Russia and Ukraine, conflict in the Middle East, significant changes in U.S. policies or regulatory environment or similar events; and

•other events and factors, many of which are beyond our control.

In recent years, the stock markets, and particularly the stock of pharmaceutical and biotechnology companies, at times have experienced price and volume fluctuations that have often been unrelated or disproportionate to the operating performance of affected companies. In addition, if the market for pharmaceutical and biotechnology stocks or the broader stock market continues to experience a loss of investor confidence, the trading price of our ADSs

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could decline for reasons unrelated to our business, financial condition or results of operations. If the market price of our ADSs does not exceed the price at which you acquired them, you may not realize any return on your investment in us and may lose some or all of your investment.

We have broad discretion in the use of the net proceeds from this offering and may not use them effectively.

Our board of directors and management will have broad discretion in the application of the net proceeds from the securities we are selling in this offering and could spend the proceeds in ways that do not improve our results of operations or enhance the value of our ADSs. The failure by our board of directors and management to apply these funds effectively could result in financial losses that could have a material adverse effect on our business, cause the price of our ADSs to decline and delay the development of our investigational COMP360 psilocybin treatment or any future therapeutic candidates. Pending the use of the proceeds from this offering, we may invest the net proceeds in short-term, interest bearing obligations and investment-grade instruments. These investments may not yield a favorable return to our shareholders.

Holders of our ADSs are not treated as holders of our ordinary shares.

By participating in this offering you will become a holder of ADSs with underlying ordinary shares in a company incorporated under English law. Holders of ADSs are not treated as holders of our ordinary shares, unless they withdraw the ordinary shares underlying their ADSs in accordance with the Deposit Agreement and applicable laws and regulations. The depositary is the holder of the ordinary shares underlying our ADSs. Holders of ADSs therefore do not have any rights as holders of our ordinary shares, other than the rights that they have pursuant to the Deposit Agreement.

Holders of our ADSs will not have the same voting rights as the holders of our ordinary shares, and may not receive voting materials or any other documents that would need to be provided to our shareholders pursuant to English law, including the UK Companies Act 2006, in time to be able to exercise their right to vote.

Except as described in the Deposit Agreement, holders of the ADSs will not be able to exercise voting rights attached to the ordinary shares represented by the ADSs. The Deposit Agreement provides that, upon receipt of notice of any meeting of holders of our ordinary shares, the depositary will fix a record date for the determination of ADS holders who shall be entitled to give instructions for the exercise of voting rights. Upon our request, the depositary shall distribute to the holders as of the record date (i) the notice of the meeting or solicitation of consent or proxy sent by us and (ii) a statement as to the manner in which instructions may be given by the holders. We cannot guarantee that ADS holders will receive the voting materials in time to ensure that they can instruct the depositary to vote the ordinary shares underlying their ADSs.

Otherwise, ADS holders will not be able to exercise their right to vote, unless they withdraw the ordinary shares underlying the ADSs they hold. However, ADS holders may not know about the applicable shareholder meeting far enough in advance to withdraw those ordinary shares. In addition, the depositary and its agents are not responsible for failing to carry out voting instructions or for the manner of carrying out voting instructions. As a result, ADS holders may not be able to exercise their right to vote, and there may be nothing they can do if the ordinary shares underlying their ADSs are not voted as they requested or if their shares cannot be voted.

There is no public market for the pre-funded warrants being offered in this offering.

There is no established public trading market for the pre-funded warrants being offered in this offering, and we do not expect a market to develop. In addition, we do not intend to apply to list these warrants on any securities exchange or nationally recognized trading system, including the Nasdaq Global Select Market. Without an active market, the liquidity of these warrants will be limited.

Holders of pre-funded warrants purchased in this offering will have no rights as a holder of ADSs until such holders exercise their pre-funded warrants and acquire ADSs representing ordinary shares.

Until holders of the pre-funded warrants acquire ADSs upon exercise of such pre-funded warrants, the holders will have no rights with respect to the ADSs representing ordinary shares underlying such pre-funded warrants.

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Upon exercise of the pre-funded warrants for ADSs representing ordinary shares, the holders will be entitled to exercise the rights of an ADS holder only as to matters for which the record date occurs after the exercise.

Significant holders or beneficial holders of our ADSs may not be permitted to exercise pre-funded warrants that they hold.

A purchaser of the pre-funded warrants sold in this offering will not be entitled to exercise any portion of any warrant which, upon giving effect to such exercise, would cause the aggregate number of ADSs representing ordinary shares beneficially owned by the holder (together with its affiliates) to exceed a specified percentage of the number of ordinary shares outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the pre-funded warrants. As a result, you may not be able to exercise your pre-funded warrants for ADSs representing ordinary shares at a time when it would be financially beneficial for you to do so. In such circumstances, you could seek to sell your pre-funded warrants to realize value, but you may be unable to do so in the absence of an established trading market for the pre-funded warrants.

Provisions of the pre-funded warrants could discourage an acquisition of us by a third party.

Certain provisions of the pre-funded warrants could make it more difficult or expensive for a third party to acquire us. The pre-funded warrants require the pre-funded warrants to be automatically exercised on a cashless basis in certain transactions constituting “fundamental transactions” (as defined in the pre-funded warrant). These and other provisions of the pre-funded warrants could prevent or deter a third party from acquiring us even where the acquisition could be beneficial to the holders of our ADSs.

We will not receive any meaningful amount of additional funds upon the exercise of the pre-funded warrants; however, any exercise would increase the number of ADSs representing ordinary shares eligible for future resale in the public market and result in dilution to our existing shareholders.

Each pre-funded warrant will be exercisable until it is fully exercised and by means of payment of the nominal cash purchase price upon exercise or by way of a cashless exercise, meaning that the holder may not pay a cash purchase price upon exercise, but instead would receive upon such exercise the net number of ADSs representing ordinary shares determined according to the formula set forth in the pre-funded warrant. Accordingly, we will not receive any meaningful, or potentially any, additional funds upon the exercise of the pre-funded warrants. To the extent such pre-funded warrants are exercised, additional ADSs representing ordinary shares will be issued for nominal or no additional consideration, which will result in dilution to the then existing holders of our ordinary shares and ADSs and will increase the number of ADSs representing ordinary shares eligible for resale in the public market.

Fluctuations in the exchange rate between the U.S. dollar and the pound sterling may increase the risk of holding our ADSs.

Our ADSs trade on the Nasdaq Global Select Market in U.S. dollars. Fluctuations in the exchange rate between the U.S. dollar and the pound sterling have occurred in the past and may continue in the future. Such fluctuations may result in temporary differences between the value of our ADSs and the value of our ordinary shares, which may result in heavy trading by investors seeking to exploit such differences.

In addition, as a result of fluctuations in the exchange rate between the U.S. dollar and the pound sterling, the U.S. dollar equivalent of the proceeds that a holder of ADSs would receive upon the sale in the UK of any ordinary shares withdrawn from the depositary and the U.S. dollar equivalent of any cash dividends paid in pounds sterling on our ordinary shares represented by ADSs could also decline.

Holders of ADSs may not be able to participate in equity offerings we may conduct from time to time.

Under English law, holders of our ordinary shares (or ADS representing those ordinary shares) are entitled to benefit from statutory pre-emption rights relating to the issue of new securities, unless those rights are otherwise disapplied by our shareholders from time to time. Where disapplied, holders of our ordinary shares (or ADS representing those ordinary shares) will not benefit from these statutory pre-emption rights and will not be entitled to

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participate in future offerings we may conduct. There are no other contractual or statutory rights which entitle investors to participate in future offerings, and the statutory pre-emption provisions under English law do not apply to warrants. As a result, there is the risk that investors may suffer dilution of their holdings should they not be permitted to participate in any equity or other offerings that we may conduct on a non-preemptive basis in the future.

Holders of ADSs may be subject to limitations on the transfer of their ADSs and the withdrawal of the underlying ordinary shares.

ADSs are transferable on the books of the depositary. However, the depositary may close its books at any time or from time to time when it deems expedient in connection with the performance of its duties. The depositary may refuse to deliver, transfer or register transfers of ADSs generally when our books or the books of the depositary are closed, or at any time if we or the depositary think it is advisable to do so because of any requirement of law, government or governmental body, or under any provision of the Deposit Agreement, or for any other reason, subject to the right of ADS holders to cancel their ADSs and withdraw the underlying ordinary shares. Temporary delays in the cancellation of your ADSs and withdrawal of the underlying ordinary shares may arise because the depositary has closed its transfer books or we have closed our transfer books, the transfer of ordinary shares is blocked to permit voting at a shareholders meeting or we are paying a dividend on our ordinary shares. In addition, ADS holders may not be able to cancel their ADSs and withdraw the underlying ordinary shares when they owe money for fees, taxes and similar charges and when it is necessary to prohibit withdrawals in order to comply with any laws or governmental regulations that apply to ADSs or to the withdrawal of ordinary shares or other deposited securities.

Our classification as a passive foreign investment company in any period would result in adverse U.S. federal income tax consequences to U.S. holders.

Under the Internal Revenue Code of 1968, as amended, or the Code, we will be a passive foreign investment company, or PFIC, for any taxable year in which (i) 75% or more of our gross income consists of passive income or (ii) 50% or more of the average quarterly value of our assets consists of assets that produce, or are held for the production of, passive income. For purposes of these tests, passive income includes dividends, interest, gains from the sale or exchange of investment property and certain rents and royalties. In addition, for purposes of the above calculations, a non-U.S. corporation that directly or indirectly owns at least 25% by value of the shares of another corporation is treated as holding and receiving directly its proportionate share of assets and income of such corporation. If we are a PFIC for any taxable year during which a U.S. Holder (as defined below in the section entitled “U.S. Federal Income Tax Considerations for U.S. holders” in Part II, Item 9B. “Other Information”) holds our ordinary shares or ADSs, the U.S. Holder may be subject to adverse tax consequences regardless of whether we continue to qualify as a PFIC, including ineligibility for any preferred tax rates on capital gains or on actual or deemed dividends, interest charges on certain taxes treated as deferred and additional reporting requirements. Based on the composition of our income and assets and the value of our assets, we believe that we were not a PFIC for U.S. federal income tax purposes for our taxable year ended December 31, 2025. However, no assurances regarding the determination of our PFIC status can be provided for the 2025 taxable year, the current taxable year or any future taxable years. The determination of whether we are a PFIC is a fact-intensive determination made on an annual basis applying principles and methodologies that in some circumstances are unclear and subject to varying interpretation. Under the income test, our status as a PFIC depends on the composition of our income which will depend on the transactions we enter into in the future and our corporate structure. The composition of our income and assets is also affected by the spending of the cash we raise in any offering.

For further discussion of the PFIC rules and adverse U.S. federal income tax consequences in the event we are classified as a PFIC, see “Material Tax Considerations-U.S. federal income tax considerations for U.S. holders” in this prospectus supplement. Each U.S. Holder should consult its tax advisors with respect to the potential adverse U.S. tax consequences to it if we are or were to become a PFIC.

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If we are a controlled foreign corporation, there could be adverse U.S. federal income tax consequences to certain U.S. Holders

Each “Ten Percent Shareholder” (as defined below) in a non-U.S. corporation that is classified as a “controlled foreign corporation,” or a CFC, for U.S. federal income tax purposes generally is required to include in income for U.S. federal tax purposes such Ten Percent Shareholder’s pro rata share of the CFC’s “Subpart F income,” “global intangible low-taxed income” (for tax years beginning prior to January 1, 2026), “net CFC tested income” (for tax years beginning after December 31, 2025) and investment of earnings in U.S. property, even if the CFC has made no distributions to its shareholders. In addition, if a non-U.S. corporation owns at least one U.S. subsidiary, under current law, any current non-U.S. subsidiaries and any future newly formed or acquired non-U.S. subsidiaries of the non-U.S. corporation will generally be treated as CFCs of such U.S. subsidiary, regardless of whether the non-U.S. corporation is treated as a CFC. Subpart F income generally includes dividends, interest, rents, royalties, gains from the sale of securities and income from certain transactions with related parties. In addition, a Ten Percent Shareholder that realizes gain from the sale or exchange of shares in a CFC may be required to classify a portion of such gain as dividend income rather than capital gain. A non-U.S. corporation generally will be classified as a CFC for U.S. federal income tax purposes if Ten Percent Shareholders own, directly or indirectly, more than 50% of either the total combined voting power of all classes of stock of such corporation entitled to vote or of the total value of the stock of such corporation. A “Ten Percent Shareholder” is a United States person (as defined by the Code) who owns or is considered to own 10% or more of the value or total combined voting power of all classes of stock entitled to vote of such corporation.

Based on our review of beneficial ownership reports filed with the SEC, we do not believe that we were classified as a CFC for the 2025 taxable year. However, no assurances regarding the determination of our CFC status can be provided for the 2025 taxable year or any future taxable years. Moreover, the determination of CFC status is complex and includes attribution rules, the application of which is not entirely certain. An individual that is a Ten Percent Shareholder with respect to a CFC generally would not be allowed certain tax deductions or foreign tax credits that would be allowed to a Ten Percent Shareholder that is a U.S. corporation. Failure to comply with CFC reporting obligations may subject a United States shareholder to significant monetary penalties. We cannot provide any assurances that we will furnish to any Ten Percent Shareholder information that may be necessary to comply with the reporting and tax paying obligations applicable under the CFC rules of the Code.

Each U.S. Holder should consult its own tax advisors with respect to the potential adverse U.S. tax consequences of becoming a Ten Percent Shareholder in a CFC.

We have a history of losses and expect to incur substantial future losses. If this offering is not completed prior to the filing of our 2025 Annual Report, or if we do not raise sufficient funds by other means, the opinion from our independent registered public accounting firm will express, substantial doubt about our ability to continue as a going concern.

As of December 31, 2025, we estimate that our cash and cash equivalents were approximately $149.6 million. The estimated cash and cash equivalents is based on preliminary unaudited information and management estimates as of December 31, 2025, is not a comprehensive consolidated statement of our financial position, and is subject to completion of our financial closing procedures and external audit. This preliminary estimated financial information does not present all necessary information for a complete understanding of our financial position as of December 31, 2025, or our results of operations for the year ended December 31, 2025. During our financial closing process our estimates can differ materially from our initial estimates presented herein based on our receipt of updated information. The actual financial results may differ materially from the preliminary estimated financial information.

We have incurred significant net losses since inception and also expect to incur substantial losses in future periods. Our estimated cash and cash equivalents as of December 31, 2025 will not be sufficient to fund our operations, as currently planned, for more than one year if this offering is not completed, and as a result we have determined that there is substantial doubt regarding our ability to continue as a going concern. Our continuation as a going concern is dependent on our ability to generate sufficient cash flows from public and private equity offerings, debt financings, strategic partnerships and alliances and licensing arrangements, or other sources. If this offering is not completed prior to the filing of our 2025 Annual Report or if we do not raise sufficient funds through other

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means, then we expect that we will disclose in our 2025 Annual Report that we would have substantial doubt about our ability to fund our operations, as currently planned, for more than one year beyond the filing date of the 2025 Annual Report. We would also expect that the opinion from our independent registered public accounting firm on such annual financial statements contained in our 2025 Annual Report would contain an explanatory paragraph about such substantial doubt about our ability to continue as a going concern. There is no assurance that we will be successful in closing this offering or raising sufficient funding through other means. If we are unable to obtain sufficient funding when needed and/or on acceptable terms, we may be required to significantly curtail, delay or discontinue one or more of our research and development programs or commercial readiness activities, which could adversely affect our business prospects, or we may be unable to continue operations.

If we are unable to obtain additional capital, we may not be able to continue our operations on the scope or scale as currently planned, and that could have a material adverse effect on our business, results of operations and financial condition.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying base prospectus and the information incorporated by reference herein and therein contain statements that are not historical facts and are considered forward-looking statements within the meaning of the Private Securities Litigation Reform Act, Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Exchange Act that involve substantial risks and uncertainties. Forward-looking statements generally relate to future events or our future financial or operating performance. All statements other than statements of historical fact, including statements regarding our strategy, future operations, financial position, estimated revenues and losses, projected costs, prospects, plans and objectives of management, are forward-looking statements. In some cases, you can identify forward-looking statements because they contain words such as “may,” “might,” “will,” “could,” “would,” “should,” “expect,” “intend,” “plan,” “objective,” “anticipate,” “believe,” “contemplate,” “estimate,” “predict,” “potential,” “continue” and “ongoing,” or the negative of these words or other similar terms or expressions, although not all forward-looking statements contain these identifying words. Forward-looking statements include, but are not limited to, statements about:

•the timing, progress and results of our Phase 3 program for TRD, and our other clinical trials of investigational COMP360 psilocybin treatment, including statements regarding the preliminary top-line primary endpoint data from the first of our two Phase 3 trials for TRD, the timing of initiation and completion of trials or studies and related preparatory work, our expectations regarding the periods during which the results of our Phase 3 trials for TRD will become available, and our expectations regarding discussions with the FDA, including discussions regarding plans for rolling submission of a new drug application, or NDA, for COMP360 psilocybin treatment in TRD;

•the timing, progress and results of our Phase2b/3 clinical trial in PTSD, including statements regarding our trial designs and our expectations regarding discussions with FDA, including discussions regarding our trial design;

•our estimates regarding our expenses, capital requirements, the sufficiency of our cash resources and our expected cash runway;

•our ability to raise additional capital or secure other financing to fund our operations;

•the potential for outstanding warrants to purchase American Depositary Shares, or ADSs, to be exercised in full for cash and any expected proceeds from the exercise of our outstanding warrants, including with respect to those outstanding warrants to purchase ADSs, or the 2025 ADS Warrants, issued in our registered financing in January 2025, our ability to achieve the specified data milestone and to achieve sufficient appreciation in the trading price of our ADSs, such that the closing price of our ADSs is above the exercise price for the 2025 ADS Warrants, for three consecutive trading days to allow us to force the cash exercise of the 2025 ADS Warrants;

•our reliance on the success of our investigational COMP360 psilocybin treatment;

•the timing, scope or likelihood of regulatory filings and approvals, including an NDA for COMP360 psilocybin treatment in TRD;

•our expectations regarding the size of the eligible patient populations for COMP360 psilocybin treatment, if approved for commercial use;

•our ability to identify third-party clinical sites to conduct our trials and our ability to identify and train appropriately qualified healthcare professionals to monitor and safeguard participants receiving COMP360 psilocybin treatment in our clinical trials;

•our ability to implement our business model and our strategic plans for our business and our investigational COMP360 psilocybin treatment;

•our ability to identify new indications for COMP360 beyond our current primary focus on TRD and PTSD;

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•our commercialization, marketing and manufacturing capabilities and strategy, including our ability to accelerate our commercial launch planning;

•the pricing, coverage and reimbursement of our investigational COMP360 psilocybin treatment, if approved;

•the scalability and commercial viability of our manufacturing methods and processes, including our ability to add commercial manufacturing capacity in the U.S.;

•the rate and degree of market acceptance and clinical utility of our investigational COMP360 psilocybin treatment, in particular, and psilocybin-based treatments, in general;

•our ability to establish or maintain collaborations or strategic relationships;

•our expectations regarding potential benefits of our investigational COMP360 psilocybin treatment and our treatment approach generally;

•our expectations around feedback from, and discussions with regulators, regulatory development paths and with respect to Controlled Substances Act designation, including potential impacts of regulatory agency staffing cuts and policy changes on regulatory feedback and timing thereof;

•the scope of protection we and any current or future licensors or collaboration partners are able to establish and maintain for intellectual property rights covering COMP360;

•our ability to operate our business without infringing, misappropriating, or otherwise violating the intellectual property rights and proprietary technology of third parties;

•our ability to identify, maintain, utilize, acquire or purchase digital technologies to enhance the administration of our investigational COMP360 psilocybin treatment in the conduct of our clinical trials;

•regulatory developments in the United States, or U.S., under the laws and regulations of England and Wales, and other jurisdictions;

•developments and projections relating to our competitors and our industry;

•the effectiveness of our internal control over financial reporting;

•our ability to attract and retain qualified employees and key personnel, including our ability to grow our commercial team;

•our ability to achieve specified clinical, regulatory and commercial milestones,and in the case of the final tranche to secure approval from lenders’ investment committees, to draw down additional amounts up to $100.0 million in accordance with the terms of our Loan and Security Agreement, as amended by the third amendment dated January 5, 2026, or the Loan Agreement, with Hercules Capital, Inc., or Hercules, and our ability to comply with the operating and financial covenants, including the minimum cash covenant, in our Loan Agreement;

•the effect of global financial and economic conditions and geopolitical events, including fluctuating interest rates and inflation, foreign exchange fluctuations (particularly the Pound Sterling to U.S. Dollar), the risk of an economic slowdown or recession in the U.S., instability in the banking system, overall market volatility in the U.S. or the UK, including as a result of, among other factors, geopolitical conflict (such as, the war between Russia and Ukraine and conflict in the Middle East), international tensions or instability (including from the effects of announced or future tariff increases), significant changes in U.S. policies or regulatory environment or the disruption to U.S. government agencies or similar events, on our business;

•the effect of public health crises, pandemics or epidemics and any future mitigation efforts, and current or future economic effects, on any of the foregoing or other aspects of our business or operations;

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•whether we are classified as a CFC or a PFIC for current and future periods;

•the future trading price of the ADSs and impact of securities analysts’ reports on these prices; and

•the anticipated uses of proceeds from the securities we are selling in this offering; and

•other risks and uncertainties, including those listed in the section titled “Risk Factors” in this prospectus supplement, or included in any document incorporated by reference herein.

We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. We have included important factors in the cautionary statements included in this prospectus supplement, the accompanying base prospectus, and documents incorporated by reference herein, particularly in the section titled “Risk Factors,” that we believe may cause our actual results or events to differ materially from those expressed or implied by our forward-looking statements. Moreover, we operate in a competitive and rapidly changing environment. New risks and uncertainties emerge from time to time, and it is not possible for us to predict all risks and uncertainties that could have an impact on the forward-looking statements contained in this prospectus supplement. As a result of these factors, we cannot assure you that the forward-looking statements in this prospectus supplement will prove to be accurate. Furthermore, if our forward-looking statements prove to be inaccurate, the inaccuracy may be material. In light of the significant uncertainties in these forward-looking statements, you should not regard these statements as a representation or warranty by us or any other person that we will achieve our objectives and plans in any specified time frame, or at all.

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this prospectus supplement, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely upon these statements.

You should read this prospectus supplement, the accompanying base prospectus and the documents incorporated by reference herein and therein, as well as the documents that we have filed as exhibits to the registration statement of which this prospectus supplement forms a part, completely and with the understanding that our actual future results, performance or achievements may be materially different from what we expect. Except as required by law, we assume no obligation to update or revise these forward-looking statements for any reason, even if new information becomes available in the future.

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USE OF PROCEEDS

We estimate that the net proceeds from the sale of securities in this offering will be approximately $140.5 million, or $161.7 million if the underwriters exercise in full their option to purchase additional 2,812,500 ADSs, in each case after deducting underwriting discounts and commissions and estimated offering expenses payable by us, and excluding the proceeds, if any, from the exercise of the pre-funded warrants in this offering.

We expect to use the net proceeds from this offering, together with our existing cash and cash equivalents, to fund ongoing COMP005 and COMP006 Phase 3 trials, our Phase 2b/3 trial of COMP360 in PTSD, acceleration of our commercial readiness activities, and for working capital and general corporate purposes. Based on our planned use of the net proceeds from this offering and our existing cash and cash equivalents (which does not include any proceeds from the exercise of our outstanding 2025 ADS Warrants which if exercised in full would provide us with approximately $200 million in gross proceeds), we estimate that the net proceeds from the sale of securities in this offering will be sufficient to allow us to accelerate investment in our commercial readiness activities and to fund our operating expenses and capital expenditure requirements into the second quarter of 2027. We have based this estimate on assumptions, including our expectations with respect to the timing of our NDA submission and the timing for regulatory review and approval, including our expectations regarding a rolling submission process, and our future clinical development in PTSD, that may prove to be wrong, and we could use our available capital resources sooner than we expect. Even with the expected net proceeds from the sale of securities in this offering, we expect we will need to raise additional capital to fully fund our commercial launch plans for COMP360 psilocybin treatment in TRD, if approved, and complete our Phase 2b/3 trial of COMP360 in PTSD.

This expected use of net proceeds from this offering represents our intentions based upon our current plans and business conditions, which could change in the future as our plans and business conditions evolve. We may also use a portion of the net proceeds to in-license, acquire, or invest in additional businesses, technologies, products or assets. We cannot predict with certainty all of the particular uses for the net proceeds to be received upon the completion of this offering or the amounts that we will actually spend on the uses set forth above. Predicting the cost necessary to develop product candidates and commercialize approved products can be difficult and the amounts and timing of our actual expenditures may vary significantly depending on numerous factors, including the progress of our development, the status of and results from clinical trials, any collaborations that we may enter into with third parties for our therapeutic candidate and any unforeseen cash needs. Our management will retain broad discretion over the allocation of the net proceeds from this offering.

Pending our use of proceeds from this offering, we plan to invest these net proceeds in a variety of capital preservation instruments, including short-term, interest bearing obligations and investment-grade instruments.

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DILUTION

If you invest in our ADSs (or pre-funded warrants in lieu thereof) in this offering, your ownership interest will be diluted to the extent of the difference between the price per ADS (or pre-funded warrants in lieu thereof) you pay in this offering and the as adjusted net tangible book value per ADS immediately after this offering.

As of September 30, 2025, our net tangible book value was $37.1 million, or $0.39 per ordinary share (equivalent to $0.39 per ADS). Our net tangible book value per ADS represents total tangible assets (excluding investments) less total liabilities, divided by the aggregate number of ordinary shares outstanding as of September 30, 2025. Dilution in net tangible book value per ADS represents the difference between the amount per share paid by purchasers of ADSs (or pre-funded warrant in lieu thereof) in this offering and the as adjusted net tangible book value per ADS of our ordinary shares immediately after giving effect to this offering.

After giving effect to the sale of (i) 17,500,000 ADSs at an offering price of $8.00 per ADS and (ii) pre-funded warrants to purchase up to 1,250,000 ADSs at an offering price of $7.9999 per pre-funded warrant, in each case excluding ADSs representing ordinary shares issued, and any proceeds received, upon exercise of the pre-funded warrants and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us, our as adjusted net tangible book value as of September 30, 2025 would have been $1.57 per ordinary share (equivalent to $1.57 per ADS). This represents an immediate increase in as adjusted net tangible book value of $1.18 per ADS to our existing shareholders and an immediate dilution of $6.43 per ADS to investors purchasing securities in this offering. The following table illustrates this dilution on a per ADS basis to new investors purchasing securities in this offering:


Public offering price per ADS (or pre-funded warrant at the offering price less $0.0001)			$	8.00
Historical net tangible book value per ADS as of September 30, 2025	$	0.39
Increase in net tangible book value per ADS attributable to new investors purchasing securities in this offering	1.18
As adjusted net tangible book value per ADS after this offering			1.57
Dilution per ADS to new investors purchasing securities in this offering			$	6.43

If the underwriters exercise in full their option to purchase 2,812,500 additional ADSs in full, our as adjusted net tangible book value as of September 30, 2025 would increase to approximately $198.8 million, or approximately $1.71 per ADS, representing an immediate increase in as adjusted net tangible book value to $1.32 per ADS to our existing stockholders, and an immediate dilution of $6.29 per ADS to investors participating in this offering.

The discussion and table above assume no exercise of the pre-funded warrants sold in this offering.

After giving effect to the offering and assuming the pre-funded warrants sold in this offering were immediately and fully exercised, our as adjusted net tangible book value after this offering would be $1.55 per ADS, representing an immediate increase in as adjusted net tangible book value of $1.16 per ADS to existing stockholders and immediate dilution of $6.45 per ADS to new investors in this offering.

•12,324,700 ordinary shares issuable upon exercise of the PIPE Warrants outstanding as of September 30, 2025, with an exercise price of $9.93 per share;

•35,059,448 ordinary shares issuable upon exercise of the ADS Warrants outstanding as of September 30, 2025, with an exercise price of $5.796 per share;

•8,700,000 ordinary shares issuable upon exercise of Pre-Funded Warrants outstanding as of September 30, 2025, with an exercise price of $0.0001 per share;

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•94,222 ordinary shares issuable upon exercise of warrants outstanding as of September 30, 2025, with an exercise price of $7.96 per share;

•7,991,809 ordinary shares issuable upon the exercise of options for ordinary shares outstanding as of September 30, 2025, with a weighted-average exercise price of $11.07 per share;

•770,652 ordinary shares issuable upon the vesting of unvested restricted share units outstanding as of September 30, 2025;

•an additional 2,697,219 ordinary shares that were available for future issuance under our 2020 Option Plan as of September 30, 2025; and

•an additional 546,402 ordinary shares that were available for future issuance under our ESPP as of September 30, 2025.

To the extent that options or restricted share awards are issued under our 2020 Option Plan or shares are issued under our ESPP, there will be further dilution to investors participating in this offering.

In addition, we may choose to raise additional capital due to market conditions or strategic considerations, even if we believe we have sufficient funds for our current or future operating plans. To the extent that additional capital is raised through the sale of equity or convertible debt securities, the issuance of these securities could result in further dilution to our shareholders.

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DESCRIPTION OF SECURITIES WE ARE OFFERING

American Depositary Shares

We are offering ADSs in this offering. See “Description of American Depositary Shares” in the accompanying base prospectus for more information regarding our ADSs.

Pre-Funded Warrants

The following is a summary of the material terms and provisions of the pre-funded warrants that are being offered hereby. This summary is subject to and qualified in its entirety by the form of pre-funded warrant, which has been provided to the investors in this offering and which will be filed with the SEC as an exhibit to a Current Report on Form 8-K in connection with this offering and incorporated by reference into the registration statement of which this prospectus supplement and the accompanying base prospectus form a part. Prospective investors should carefully review the terms and provisions of the form of pre-funded warrant for a complete description of the terms and conditions of the pre-funded warrants.

Duration and Exercise Price

The pre-funded warrants offered hereby will have an exercise price of $0.0001 per share. The pre-funded warrants will be exercisable immediately upon the closing of this offering. The exercise price of the pre-funded warrants and the number of ADSs representing ordinary shares issuable upon exercise of the pre-funded warrants are subject to appropriate adjustment in the event of stock dividends, stock splits, reorganizations or similar events affecting our ordinary shares and ADSs and any adjustment to the ADS ratio of ordinary shares per ADS. The pre-funded warrants will not expire until they are fully exercised.

Exercisability

The pre-funded warrants will be exercisable, at the option of each holder, in whole or in part, by delivering to us a duly executed exercise notice accompanied by payment in full for the number of ADSs representing ordinary shares purchased upon such exercise (except in the case of a cashless exercise as discussed below). A holder (together with its affiliates) may not exercise any portion of such holder’s pre-funded warrants to the extent that the holder would own more than the Beneficial Ownership Limitation.

The holder of a pre-funded warrant, upon notice to the Company, may increase or decrease the Beneficial Ownership Limitation, provided that the Beneficial Ownership Limitation in no event exceeds 19.99% of the number of ordinary shares outstanding immediately after giving effect to the issuance of ordinary shares upon exercise. Any increase in the Beneficial Ownership Limitation will not be effective until the 61st day after such notice is delivered to us.

Cashless Exercise

The pre-funded warrants may be exercised by delivery of the aggregate exercise price or by means of a cashless exercise.

Transferability

The pre-funded warrants may be transferred at the option of the holder upon surrender of the pre-funded warrant to us together with a written assignment of the pre-funded warrant and funds sufficient to pay any transfer taxes payable upon making such transfer.

Fractional Shares

No fractional ADSs will be issued upon the exercise of the pre-funded warrants. Rather, the number of shares of ADSs to be issued will, at our election, either pay a cash adjustment in respect of such final fraction in an amount equal to such fraction multiplied by the exercise price or rounded down to the next whole ADS.

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Trading Market

We do not intend to list the pre-funded warrants on the Nasdaq Global Select Market, any other national securities exchange or any other nationally recognized trading system.

Rights as an ADS Holder

Except as otherwise provided in the pre-funded warrants or by virtue of the holders’ ownership of ADSs, the holders of pre-funded warrants do not have the rights or privileges of holders of our ADSs until such pre-funded warrant holders exercise their pre-funded warrants.

Fundamental Transactions

In the event of a fundamental transaction, as described in the pre-funded warrants and generally including any reorganization, recapitalization or reclassification of our ordinary shares (including ordinary shares underlying ADSs) or any compulsory share exchange where the ordinary shares are converted or exchanged for other securities, cash or properties, the sale, transfer or other disposition of all or substantially all of our assets, our consolidation or merger with or into another person, any purchase offer, tender offer or exchange offer pursuant to which holders of 50% or more of our ordinary shares (including any ordinary shares underlying ADSs) sell, tender or exchange their shares for other securities, cash or property, or any share purchase agreement or other business combination whereby any person or group becoming the beneficial owner of greater than 50% of the voting power of our ordinary shares, the pre-funded warrants will be automatically exercised through a cashless exercise. However, if the automatic exercise would result in the holder receiving ADSs in excess of the Beneficial Ownership Limitation, or the Excess Warrant ADSs, we will additionally purchase the ADS pre-funded warrant with respect to the Excess Warrant ADSs from the holder by paying to the holder an amount of cash equal to the Black-Scholes Value on the date of the consummation of such fundamental transaction.

Waivers and Amendments

No term of the pre-funded warrants may be amended or waived without the written consent of the holder of such pre-funded warrant.

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UNDERWRITING

We and the underwriters for the offering named below have entered into an underwriting agreement with respect to the ADSs and pre-funded warrants being offered. Subject to the terms and conditions of the underwriting agreement, each underwriter has severally agreed to purchase from us the number of our ADSs and pre-funded warrants set forth opposite its name below. Jefferies LLC, TD Securities (USA) LLC, Cantor Fitzgerald & Co., and Stifel, Nicolaus & Company, Incorporated are the representatives of the underwriters.


Underwriter	Number of ADSs	Number of Pre-Funded Warrants
Jefferies LLC	5,687,500	406,250
TD Securities (USA) LLC	4,375,000	312,500
Cantor Fitzgerald & Co.	3,500,000	250,000
Stifel, Nicolaus & Company, Incorporated	3,500,000	250,000
H.C. Wainwright & Co., LLC	437,500	31,250
Total	17,500,000	1,250,000

The underwriting agreement provides that the obligations of the several underwriters are subject to certain conditions precedent such as the receipt by the underwriters of officers’ certificates and legal opinions and approval of certain legal matters by their counsel. The underwriting agreement provides that the underwriters will purchase all of the ADSs and pre-funded warrants if any of them are purchased. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the nondefaulting underwriters may be increased or the underwriting agreement may be terminated.

We have agreed to indemnify the underwriters and certain of their controlling persons against certain liabilities, including liabilities under the Securities Act, and to contribute to payments that the underwriters may be required to make in respect of those liabilities.

The underwriters have advised us that, following the completion of this offering, they currently intend to make a market in the ADSs as permitted by applicable laws and regulations. However, the underwriters are not obligated to do so, and the underwriters may discontinue any market-making activities at any time without notice in their sole discretion. Accordingly, no assurance can be given as to the liquidity of the trading market for the ADSs, that you will be able to sell any of the ADSs held by you at a particular time or that the prices that you receive when you sell will be favorable.

The underwriters are offering ADSs and pre-funded warrants subject to their acceptance of the ADSs and pre-funded warrants from us and subject to prior sale. The underwriters reserve the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part.

Commission and Expenses

The underwriters have advised us that they propose to offer the ADSs and pre-funded warrants to the public at the initial public offering price set forth on the cover page of this prospectus supplement and to certain dealers, which may include the underwriters, at that price less a concession not in excess of $0.288 per ADS or pre-funded warrant. After the offering, the initial public offering price and concession may be reduced by the representatives. No such reduction will change the amount of proceeds to be received by us as set forth on the cover page of this prospectus supplement.

The following table shows the public offering price, the underwriting discounts and commissions that we are to pay the underwriters and the proceeds, before expenses, to us in connection with this offering. Such amounts are shown assuming both no exercise and full exercise of the underwriters’ option to purchase additional ADSs.

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			Total
	Per ADS	Per Pre-Funded Warrant	Without Option to Purchase Additional ADSs	With Option to Purchase Additional ADSs
Public offering price	$8.00	$7.9999	$149,999,875	$172,499,875
Underwriting discounts and commissions	$0.48	$0.4800	$8,999,993	$10,349,993
Proceeds, before expenses, to COMPASS Pathways plc	$7.52	$7.5199	$140,999,883	$162,149,883

We estimate expenses payable by us in connection with this offering, other than the underwriting discounts and commissions referred to above, will be approximately $500,000. We have agreed to reimburse the underwriters for up to $20,000 of expenses incurred in connection with this offering. The underwriters have agreed to reimburse us for certain expenses incurred by us in connection with this offering.

Listing

The ADSs representing our ordinary shares are listed on the Nasdaq Global Select Market under the symbol “CMPS”. We do not intend to list the pre-funded warrants on the Nasdaq Global Select Market or any other national securities exchange or nationally recognized trading system.

Option to Purchase Additional ADSs

We have granted to the underwriters an option, exercisable for 30 days from the date of this prospectus supplement, to purchase, from time to time, in whole or in part, up to an aggregate of 2,812,500 ADSs from us at the public offering price set forth on the cover page of this prospectus supplement, less underwriting discounts and commissions. If the underwriters exercise this option, each underwriter will be obligated, subject to specified conditions, to purchase a number of ADSs proportionate to that underwriter’s initial purchase commitment as indicated in the table above.

No Sale of Similar Securities

Pursuant to certain “lock-up” agreements, we and our executive officers and directors, have agreed, subject to certain exceptions, not to and will not cause or direct any affiliates to offer, sell, assign, transfer, pledge, contract to sell, lend or otherwise dispose of or announce the intention to otherwise dispose of, or enter into, or announce the intention to enter into any swap, hedge or similar agreement or arrangement (including, without limitation, the purchase or sale of, or entry into, any put or call option, or combination thereof, forward, swap or any other derivative transaction or instrument, however described or defined) that transfers, is designed to transfer or reasonably could be expected to transfer (whether by the securityholder or someone other than the securityholder) in whole or in part, the economic risk of ownership of, directly or indirectly, or engage in, or announce the intention to engage in, any short selling, or make any demand or request or exercise any right with respect to the registration of, or file with the SEC a registration statement under the Securities Act relating to, any ordinary shares, ADSs or securities convertible into or exchangeable or exercisable for any ordinary shares or ADSs (other than as contemplated by the underwriting agreement with respect to ordinary shares represented by ADSs issuable upon exercise of the pre-funded warrants sold in this offering) without the prior written consent of the representatives, for a period of 60 days after the date of this prospectus supplement.

This lock-up provision applies to ordinary shares and ADSs owned now or acquired later by the person executing the agreement or for which the person executing the agreement later acquires the power of disposition. The exceptions permit us, among other things and subject to restrictions, to: (a) issue ordinary shares and options to subscribe for ordinary shares pursuant to any director or employee incentive plan, share ownership plan or dividend reinvestment plan in effect as of the date of the underwriting agreement and described in this prospectus supplement; (b) issue ordinary shares pursuant to the conversion of securities or the exercise of warrants outstanding as of the date of the underwriting agreement and described in this prospectus supplement; or (c) adopt a new equity incentive plan and file a registration statement on Form S-8 under the Securities Act to register the offer and sale of securities to be issued pursuant to such new equity incentive plan, and the issuance of securities pursuant to such new equity

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incentive plan (including, without limitation, the issuance of ordinary shares upon the exercise of options or other securities issued pursuant to such new equity incentive plan).

The lock-up provision does not apply to parties to the “lock-up” agreements, with respect to and subject to restrictions: (a) if the lock-up party is a natural person, transfers of locked-up securities: (i) as a bona fide gift to any member of the immediate family (as defined in the lock-up agreement) of the lock-up party or to a trust the beneficiaries of which are exclusively the lock-up party or members of the lock-up party’s immediate family, (ii) by will or intestate succession upon the death of the lock-up party or (iii) as a bona fide gift to a charity or educational institution; (b) if the lock-up party is a corporation, partnership, limited liability company or other business entity, transfers of locked-up securities to any securityholder, partner or member of, or owner of a similar equity interest in, the lock-up party, as the case may be, if, in any such case, such transfer is not for value; (c) if the lock-up party is a trust, distributions of locked-up securities or any security directly or indirectly convertible into lock-up securities to its beneficiaries in a transaction not involving a disposition of value; (d) if the lock-up party is a corporation, partnership, limited liability company or other business, corporate or similar legal entity in its place of incorporation, transfers of locked-up securities (i) in connection with the sale or other bona fide transfer in a single transaction of all or substantially all of the lock-up party’s share capital, partnership interests, membership interests or other similar equity interests, as the case may be, or all or substantially all of the lock-up party’s assets, in any such case not undertaken for the purpose of avoiding the restrictions imposed by the lock-up agreement or (ii) to another corporation, partnership, limited liability company or other business entity so long as the transferee is an affiliate (as defined in Rule 405 under the Securities Act) of the lock-up party and such transfer is not for value; (e) transfers of locked-up securities solely by operation of law, such as pursuant to a qualified domestic order or in connection with a divorce settlement; (f) transfers of locked-up securities to us pursuant to agreements in effect as of the date of this prospectus supplement under which we have the option to repurchase such locked-up securities upon termination of the lock-up party’s service to us; (g) transfers of locked-up securities solely in connection with the surrender or forfeiture of locked-up securities to us in partial or full settlement of any withholding tax obligation of the lock-up party accruing upon the exercise or vesting of any equity award granted pursuant to our equity incentive plans or arrangements as disclosed in this prospectus supplement; (h) transfers of locked-up securities pursuant to a bona fide third-party tender offer, merger, consolidation or other similar transaction made to all holders of locked-up securities involving a change of control of us in which the acquiring party, or a group of parties, other than us, becomes the beneficial owner (as defined in Rules 13d-3 and 13d-5 of the Exchange Act) of a majority of total voting power of the voting shares of us, provided that in the event that the tender offer, merger, consolidation or other such transaction is not completed, the locked-up securities owned by the lock-up party shall remain subject to the restrictions of the lock-up agreement; (i) transactions relating to ordinary shares, ADSs or other securities convertible into or exercisable or exchangeable for ordinary shares or ADSs acquired in open market transactions after the completion of this offering, provided that no such transaction is required to be, or is, publicly announced during the lock-up period; and (j) the entry into, by the lock-up party, at any time on or after the date of this prospectus supplement, of any trading plan providing for the sale of locked-up securities by the lock-up party, which trading plan meets the requirements of Rule 10b5-1(c) under the Exchange Act, provided, however, that (i) such plan does not provide for, or permit, the sale of any locked-up securities during the lock-up period and (ii) no public announcement or filing is voluntarily made during the lock-up period, and any required announcement or filing under the Exchange Act includes a statement to the effect that no transfer of Ordinary Shares or ADSs shall be made under such plan during the lock-up period. In addition, the lock-up provision will not restrict broker-dealers from engaging in market making and similar activities conducted in the ordinary course of their business.

The representatives, in their sole discretion, may release our ordinary shares, ADSs and other securities subject to the lock-up agreements described above in whole or in part at any time. When determining whether or not to release our securities from lock-up agreements, the representatives will consider, among other factors, the holder’s reasons for requesting the release, the number of securities for which the release is being requested and market conditions at the time of the request.

Stabilization

The underwriters have advised us that they may engage in short sale transactions, stabilizing transactions, syndicate covering transactions or the imposition of penalty bids in connection with this offering. These activities may have the effect of stabilizing or maintaining the market price of our ADSs at a level above that which might

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otherwise prevail in the open market. Establishing short sales positions may involve either “covered” short sales or “naked” short sales.

“Covered” short sales are sales made in an amount not greater than the underwriters’ option to purchase additional ADSs in this offering. The underwriters may close out any covered short position by either exercising their option to purchase additional ADSs or purchasing ADSs in the open market. In determining the source of ADSs to close out the covered short position, the underwriters will consider, among other things, the price of ADSs available for purchase in the open market as compared to the price at which they may purchase ADSs through the option to purchase additional ADSs.

“Naked” short sales are sales in excess of the option to purchase additional ADSs. The underwriters must close out any naked short position by purchasing ADSs in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the ADSs in the open market after pricing that could adversely affect investors who purchase in this offering.

A stabilizing bid is a bid for the purchase of ADSs on behalf of the underwriters for the purpose of fixing or maintaining the price of ADSs. A syndicate covering transaction is the bid for or the purchase of ADSs on behalf of the underwriters to reduce a short position incurred by the underwriters in connection with the offering. Similar to other purchase transactions, the underwriters’ purchases to cover the syndicate short sales may have the effect of raising or maintaining the market price of our ADSs or preventing or retarding a decline in the market price of our ADSs. As a result, the price of our ADSs may be higher than the price that might otherwise exist in the open market. A penalty bid is an arrangement permitting the underwriters to reclaim the selling concession otherwise accruing to a syndicate member in connection with the offering if the ADSs originally sold by such syndicate member are purchased in a syndicate covering transaction and therefore have not been effectively placed by such syndicate member.

Neither we, nor any of the underwriters make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of our ADSs. The underwriters are not obligated to engage in these activities and, if commenced, any of the activities may be discontinued at any time.

The underwriters may also engage in passive market making transactions in our ADSs on The Nasdaq Global Select Market in accordance with Rule 103 of Regulation M during a period before the commencement of offers or sales of our ADSs in this offering and extending through the completion of distribution. A passive market maker must display its bid at a price not in excess of the highest independent bid of that security. However, if all independent bids are lowered below the passive market maker’s bid, that bid must then be lowered when specified purchase limits are exceeded.

Electronic Distribution

A prospectus supplement in electronic format may be made available by e-mail or on the web sites or through online services maintained by one or more of the underwriters or their affiliates. In those cases, prospective investors may view offering terms online and may be allowed to place orders online. The underwriters may agree with us to allocate a specific number of ADSs for sale to online brokerage account holders. Any such allocation for online distributions will be made by the underwriters on the same basis as other allocations. Other than the prospectus in electronic format, the information on the underwriters’ web sites and any information contained in any other web site maintained by any of the underwriters is not part of this prospectus supplement, has not been approved and/or endorsed by us or the underwriters and should not be relied upon by investors.

Other Activities and Relationships

The underwriters and certain of their affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. The underwriters and certain of their affiliates have, from time to time, performed, and may in the future perform, various commercial and investment banking and financial advisory services for us and our affiliates, for which they received or will receive customary fees and expenses. For example, we are a party to an sales agreement, dated

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February 27, 2025, with TD Securities (USA) LLC, pursuant to which we may offer and sell an aggregate of up to $150,000,000 of our ADSs from time to time through TD Securities (USA) LLC, acting as sales agent, under an “at the market offering” program.

In the ordinary course of their various business activities, the underwriters and certain of its affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers, and such investment and securities activities may involve securities and/or instruments issued by us and our affiliates. If the underwriters or their respective affiliates have a lending relationship with us, they routinely hedge their credit exposure to us consistent with their customary risk management policies. The underwriters and their respective affiliates may hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities or the securities of our affiliates, including potentially the ADSs offered hereby. Any such short positions could adversely affect future trading prices of the ADSs offered hereby. The underwriters and certain of their respective affiliates may also communicate independent investment recommendations, market color or trading ideas and/or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

Selling Restrictions

Canada. The securities may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the securities must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

Switzerland. The securities will not be offered, directly or indirectly, to the public in Switzerland and this prospectus does not constitute a public offering prospectus as that term is understood pursuant to article 652a or 1156 of the Swiss Federal Code of Obligations.

European Economic Area. In relation to each Member State of the European Economic Area (each, a “Member State”), no securities have been offered or will be offered pursuant to the offering to the public in that Member State prior to the publication of a prospectus in relation to the securities which has been approved by the competent authority in that Member State or, where appropriate, approved in another Member State and notified to the competent authority in that Member State, all in accordance with the Prospectus Regulation, except that securities may be offered to the public in that Member State at any time:

A.to any legal entity which is a qualified investor as defined under Article 2 the Prospectus Regulation;

B.to fewer than 150 natural or legal persons (other than qualified investors as defined under Article 2 the Prospectus Regulation), subject to obtaining the prior consent of the representatives for any such offer; or

C.in any other circumstances falling within Article 1(4) of the Prospectus Regulation,

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provided that no such offer of the securities shall require us or any of the representatives to publish a prospectus pursuant to Article 3 of the Prospectus Regulation or supplement a prospectus pursuant to Article 23 of the Prospectus Regulation.

For the purposes of this provision, the expression an “offer to the public” in relation to securities in any Member State means the communication in any form and by any means of sufficient information on the terms of the offer and any securities to be offered so as to enable an investor to decide to purchase or subscribe for any securities, and the expression “Prospectus Regulation” means Regulation (EU) 2017/1129.

United Kingdom. No securities have been offered or will be offered pursuant to the offering to the public in the United Kingdom prior to the publication of a prospectus in relation to the securities which has been approved by the Financial Conduct Authority, except that the securities may be offered to the public in the United Kingdom at any time:

A.to any legal entity which is a qualified investor as defined under Article 2 of the UK Prospectus Regulation;

B.to fewer than 150 natural or legal persons (other than qualified investors as defined under Article 2 of the UK Prospectus Regulation), subject to obtaining the prior consent of the representatives for any such offer; or

C.in any other circumstances falling within Section 86 of the FSMA,

provided that no such offer of the securities shall require the Issuer or any Manager to publish a prospectus pursuant to Section 85 of the FSMA or supplement a prospectus pursuant to Article 23 of the UK Prospectus Regulation. For the purposes of this provision, the expression an “offer to the public” in relation to the securities in the United Kingdom means the communication in any form and by any means of sufficient information on the terms of the offer and any securities to be offered so as to enable an investor to decide to purchase or subscribe for any securities and the expression “UK Prospectus Regulation” means Regulation (EU) 2017/1129 as it forms part of domestic law by virtue of the European Union (Withdrawal) Act 2018.

Hong Kong. The securities have not been offered or sold and will not be offered or sold in Hong Kong, by means of any document, other than (a) to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571 of the Laws of Hong Kong) (the “SFO”) of Hong Kong and any rules made thereunder; or (b) in other circumstances which do not result in the document being a “prospectus” as defined in the Companies (Winding Up and Miscellaneous Provisions) Ordinance (Cap. 32) of Hong Kong (the “CO”), or which do not constitute an offer to the public within the meaning of the CO. No advertisement, invitation or document relating to the securities has been or may be issued or has been or may be in the possession of any person for the purposes of issue, whether in Hong Kong or elsewhere, which is directed at, or the contents of which are likely to be accessed or read by, the public of Hong Kong (except if permitted to do so under the securities laws of Hong Kong) other than with respect to securities which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” as defined in the SFO and any rules made thereunder.

Singapore. Each underwriter has acknowledged that this prospectus supplement has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, each underwriter has represented and agreed that it has not offered or sold any securities or caused the securities to be made the subject of an invitation for subscription or purchase and will not offer or sell any securities or cause the securities to be made the subject of an invitation for subscription or purchase, and has not circulated or distributed, nor will it circulate or distribute, this prospectus supplement or any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the securities, whether directly or indirectly, to any person in Singapore other than:

A.to an institutional investor (as defined in Section 4A of the Securities and Futures Act (Chapter 289) of Singapore, as modified or amended from time to time (the “SFA”)) pursuant to Section 274 of the SFA;

B.to a relevant person (as defined in Section 275(2) of the SFA) pursuant to Section 275(1) of the SFA, or any person pursuant to Section 275(1A) of the SFA, and in accordance with the conditions specified in Section 275 of the SFA; or

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C.otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA.

Where the securities are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

A.a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or

B.a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary of the trust is an individual who is an accredited investor,

securities or securities-based derivatives contracts (each term as defined in Section 2(1) of the SFA) of that corporation or the beneficiaries’ rights and interest (however described) in that trust shall not be transferred within six months after that corporation or that trust has acquired the securities pursuant to an offer made under Section 275 of the SFA except:

(i)to an institutional investor or to a relevant person, or to any person arising from an offer referred to in Section 275(1A) or Section 276(4)(i)(B) of the SFA;

(ii)where no consideration is or will be given for the transfer;

(iii)where the transfer is by operation of law;

(iv)as specified in Section 276(7) of the SFA; or

(v)as specified in Regulation 37A of the Securities and Futures (Offers of Investments) (Securities and Securities-based Derivatives Contracts) Regulations 2018.

Singapore SFA Product Classification — In connection with Section 309B of the SFA and the CMP Regulations 2018, unless otherwise specified before an offer of shares, we have determined, and hereby notify all relevant persons (as defined in Section 309A(1) of the SFA), that the securities are “prescribed capital markets products” (as defined in the CMP Regulations 2018) and Excluded Investment Products (as defined in MAS Notice SFA 04-N12: Notice on the Sale of Investment Products and MAS Notice FAA-N16: Notice on Recommendations on Investment Products).

Israel. In the State of Israel this prospectus supplement shall not be regarded as an offer to the public to purchase securities under the Israeli Securities Law, 5728 – 1968, which requires a prospectus to be published and authorized by the Israel Securities Authority, if it complies with certain provisions of Section 15 of the Israeli Securities Law, 5728–1968, including, inter alia, if: (i) the offer is made, distributed or directed to not more than 35 investors, subject to certain conditions (the “Addressed Investors”); or (ii) the offer is made, distributed or directed to certain qualified investors defined in the First Addendum of the Israeli Securities Law, 5728 – 1968, subject to certain conditions (the “Qualified Investors”). The Qualified Investors shall not be taken into account in the count of the Addressed Investors and may be offered to purchase securities in addition to the 35 Addressed Investors. The company has not and will not take any action that would require it to publish a prospectus in accordance with and subject to the Israeli Securities Law, 5728 – 1968. We have not and will not distribute this prospectus supplement or make, distribute or direct an offer to subscribe for our securities to any person within the State of Israel, other than to Qualified Investors and up to 35 Addressed Investors.

Qualified Investors may have to submit written evidence that they meet the definitions set out in of the First Addendum to the Israeli Securities Law, 5728 – 1968. In particular, we may request, as a condition to be offered securities, that Qualified Investors will each represent, warrant and certify to us and/or to anyone acting on our behalf: (i) that it is an investor falling within one of the categories listed in the First Addendum to the Israeli Securities Law, 5728 – 1968; (ii) which of the categories listed in the First Addendum to the Israeli Securities Law, 5728 – 1968 regarding Qualified Investors is applicable to it; (iii) that it will abide by all provisions set forth in the Israeli Securities Law, 5728 – 1968 and the regulations promulgated thereunder in connection with the offer to be issued securities; (iv) that the securities that it will be issued are, subject to exemptions available under the Israeli Securities Law, 5728 – 1968: (a) for its own account; (b) for investment purposes only; and (c) not issued with a

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view to resale within the State of Israel, other than in accordance with the provisions of the Israeli Securities Law, 5728 – 1968; and (v) that it is willing to provide further evidence of its Qualified Investor status. Addressed Investors may have to submit written evidence in respect of their identity and may have to sign and submit a declaration containing, inter alia, the Addressed Investor’s name, address and passport number or Israeli identification number.

We have not authorized and do not authorize the making of any offer of securities through any financial intermediary on our behalf, other than offers made by the underwriters and their respective affiliates, with a view to the final placement of the securities as contemplated in this document. Accordingly, no purchaser of the securities, other than the underwriters, is authorized to make any further offer of securities on our behalf or on behalf of the underwriters.

Electronic Offer, Sale and Distribution of ADSs. A prospectus in electronic format may be made available on the websites maintained by one or more of the underwriters or selling group members, if any, participating in this offering and one or more of the underwriters participating in this offering may distribute prospectuses electronically. The representatives may agree to allocate a number of ADSs and pre-funded warrants to underwriters and selling group members for sale to their online brokerage account holders. Internet distributions will be allocated by the underwriters and selling group members that will make internet distributions on the same basis as other allocations. Other than the prospectus in electronic format, the information on these websites is not part of this prospectus supplement or the registration statement of which this prospectus supplement forms a part, has not been approved or endorsed by us or any underwriter in its capacity as underwriter, and should not be relied upon by investors.

Other Relationships. Certain of the underwriters and their affiliates have provided, and may in the future provide, various investment banking, commercial banking and other financial services for us and our affiliates for which they have received, and may in the future receive, customary fees. For example, TD Securities (USA) LLC is the sales agent under our Sales Agreement, pursuant to which we may offer and sell from time to time up to $150.0 million of ADSs through them in “at-the-market” offerings.

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MATERIAL TAX CONSIDERATIONS

U.S. federal income tax considerations for U.S. holders

The following is a description of the material U.S. federal income tax consequences to the U.S. Holders described below of (i) owning and disposing of our ordinary shares or ADSs and (ii) owning and disposing of the pre-funded warrants issued pursuant to this offering. The ordinary shares, ADSs and pre-funded warrants are referred to collectively herein as our securities. This discussion is not a comprehensive description of all tax considerations that may be relevant to a particular person’s decision to acquire our securities. This discussion applies only to a U.S. Holder holding our securities as a capital asset for tax purposes (generally, property held for investment). In addition, it does not describe all of the tax consequences that may be relevant in light of a U.S. Holder’s particular circumstances, including state and local tax consequences, estate tax consequences, alternative minimum tax consequences, the special tax accounting rules under Section 451(b) of the Code, the potential application of the Medicare contribution tax, and tax consequences applicable to U.S. Holders subject to special rules, such as:

•banks, insurance companies, and certain other financial institutions;

•U.S. expatriates and certain former citizens or long-term residents of the United States;

•dealers or traders in securities who use a mark-to-market method of tax accounting;

•persons holding our securities as part of a hedging transaction, “straddle,” wash sale, conversion transaction or integrated transaction or persons entering into a constructive sale with respect to our securities;

•persons whose “functional currency” for U.S. federal income tax purposes is not the U.S. dollar;

•brokers, dealers or traders in securities, commodities or currencies;

•tax-exempt entities or government organizations;

•S corporations, partnerships, or other entities or arrangements classified as partnerships for U.S. federal income tax purposes;

•regulated investment companies or real estate investment trusts;

•persons that own or are deemed to own 10% or more of the voting power or value of our securities;

•persons who acquired our securities pursuant to the exercise of any employee share option or otherwise as compensation;

•persons holding our securities in connection with a trade or business, permanent establishment, or fixed base outside the United States; and

•persons who own (directly or through attribution) 10% or more (by vote or value) of our outstanding securities.

If an entity that is classified as a partnership for U.S. federal income tax purposes holds our securities, the U.S. federal income tax treatment of a partner will generally depend on the status of the partner and the activities of the partnership. Partnerships holding our securities and partners in such partnerships are encouraged to consult their tax advisers as to the particular U.S. federal income tax consequences of holding and disposing of our securities.

The discussion is based on the Code, administrative pronouncements, judicial decisions, final, temporary and proposed Treasury Regulations, and the income tax treaty between the UK and the United States, all as of the date of this prospectus supplement, changes to any of which may affect the tax consequences described herein-possibly with retroactive effect.

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A “U.S. Holder” is a holder who, for U.S. federal income tax purposes, is a beneficial owner of ordinary shares, ADSs or pre-funded warrants and is:

(i)An individual who is a citizen or individual resident of the United States;

(ii)a corporation, or other entity taxable as a corporation, created or organized in or under the laws of the United States, any state therein or the District of Columbia;

(iii)an estate the income of which is subject to U.S. federal income taxation regardless of its source; or

(iv)a trust if (1) a U.S. court is able to exercise primary supervision over the administration of the trust and one or more U.S. persons have authority to control all substantial decisions of the trust or (2) the trust has a valid election to be treated as a U.S. person under applicable U.S. Treasury Regulations.

Generally, a U.S. Holder of an ADS should be treated for U.S. federal income tax purposes as holding the ordinary shares represented by our ADS. Accordingly, no gain or loss will be recognized upon an exchange of ADSs for ordinary shares. The U.S. Treasury has expressed concerns that intermediaries in the chain of ownership between the holder of an ADS and the issuer of the security underlying our ADS may be taking actions that are inconsistent with the beneficial ownership of the underlying security. Accordingly the creditability of foreign taxes, if any, as described below, could be affected by actions taken by intermediaries in the chain of ownership between the holders of ADSs and our company if as a result of such actions the holders of ADSs are not properly treated as beneficial owners of the underlying ordinary shares. These actions would also be inconsistent with the claiming of the reduced tax rate, described below, applicable to dividends received by certain non-corporate holders.

PERSONS CONSIDERING AN INVESTMENT IN OUR SECURITIES SHOULD CONSULT THEIR TAX ADVISORS AS TO THE PARTICULAR TAX CONSEQUENCES APPLICABLE TO THEM RELATING TO THE ACQUISITION, OWNERSHIP AND DISPOSITION OF THE ORDINARY SHARES OR ADSs, INCLUDING THE APPLICABILITY OF U.S. FEDERAL, STATE AND LOCAL TAX LAWS.

Treatment of Pre-Funded Warrants

Although it is not entirely free from doubt, a pre-funded warrant should be treated as an ADS for U.S. federal income tax purposes and a U.S. Holder of a pre-funded warrant should generally be taxed in the same manner as a U.S. Holder of such ADS, as described below. Accordingly, no gain or loss should be recognized upon the exercise of a pre-funded warrant and, upon exercise, the holding period of a pre-funded warrant should carry over to the ADS representing ordinary shares received. Similarly, the tax basis of the pre-funded warrant should carry over to the ADS representing ordinary shares received upon exercise, increased by the exercise price of $0.0001 per share. If a pre-funded warrant expires without being exercised, the U.S. Holder should recognize a capital loss in an amount equal to such U.S. Holder’s tax basis in the pre-funded warrant. This loss will be long-term capital loss if, at the time of the expiration, the U.S. Holder’s holding period in the pre-funded warrant is more than one year. The deductibility of capital losses is subject to limitations.

Our characterization is not binding on the Internal Revenue Service, or the IRS, and the IRS may treat our pre-funded warrants as warrants to acquire ADSs representing ordinary shares. In that case, the amount and character of your gain with respect to an investment in our pre-funded warrants could be materially different than the discussion set forth below. Accordingly, each U.S. Holder should consult its tax advisors regarding the risks associated with the acquisition of pre-funded warrants pursuant to this offering (including potential alternative characterizations). The balance of this discussion generally assumes that a pre-funded warrant is treated as an ADS for U.S. federal income tax purposes.

Allocation of Purchase Price

Each U.S. Holder must allocate its purchase price for the securities it purchases between each ADS or pre-funded warrant based on the respective relative fair market values of each at the time of issuance. This allocation of the purchase price will establish the U.S. Holder’s initial tax basis for U.S. federal income tax purposes for each ADS and pre-funded warrant. A U.S. Holder’s allocation of the purchase price among the ADSs and pre-funded

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warrants is not binding on the IRS or the courts, and no assurance can be given that the IRS or the courts will agree with a U.S. Holder’s allocation. Each U.S. Holder should consult its tax advisor regarding the allocation of the purchase price among the ADSs and pre-funded warrants.

Passive Foreign Investment Company Rules

If we are classified as a PFIC in any taxable year, a U.S. Holder of ordinary shares or ADSs will be subject to special rules generally intended to reduce or eliminate any benefits from the deferral of U.S. federal income tax that such U.S. Holder could derive from investing in a non-U.S. company that does not distribute all of its earnings on a current basis.

A non-U.S. corporation will be classified as a PFIC for any taxable year in which, after applying certain look-through rules, either:

•at least 75% of its gross income is passive income (such as interest income); or

•at least 50% of its gross assets (determined on the basis of a quarterly average) is attributable to assets that produce passive income or are held for the production of passive income.

We do not believe that we were a PFIC for U.S. federal income tax purposes for our taxable year ended December 31, 2025. However, no assurances regarding our PFIC status can be provided for the 2025 taxable year. Based on the current and expected composition of our income and assets and the value of our assets, even if we will not be a considered a PFIC in the 2025 taxable year, we believe that we may be a PFIC for U.S. federal income tax purposes for our current taxable year. However, no assurances regarding our PFIC status can be provided for any past taxable years (including the 2025 taxable year), the current taxable year or any future taxable years. The determination of whether we are a PFIC is a fact-intensive determination made on an annual basis applying principles and methodologies that in some circumstances are unclear and subject to varying interpretation. If we are treated as a non-publicly traded CFC for the year being tested for purposes of the PFIC rules, the value of our assets will be measured by the adjusted tax basis of our assets. If we are a publicly traded CFC or not a CFC for such year, the value of our assets generally will be determined by reference to the market price of our ordinary shares or ADSs from time to time, which may fluctuate considerably. Under the income test, our status as a PFIC depends on the composition of our income which will depend on the transactions we enter into in the future and our corporate structure. The composition of our income and assets is also affected by the spending of the cash we raise in any offering.

If we are classified as a PFIC in any year with respect to which a U.S. Holder owns the ordinary shares or ADSs, we will continue to be treated as a PFIC with respect to such U.S. Holder in all succeeding years during which the U.S. Holder owns the ordinary shares or ADSs, regardless of whether we continue to meet the tests described above unless (i) we cease to be a PFIC and the U.S. Holder has made a “deemed sale” election under the PFIC rules, or (ii) the U.S. Holder makes a Qualified Electing Fund Election, or QEF Election, with respect to all taxable years during such U.S. Holders holding period in which we are a PFIC. If the “deemed sale” election is made, a U.S. Holder will be deemed to have sold the ordinary shares or ADSs the U.S. Holder holds at their fair market value and any gain from such deemed sale would be subject to the rules described below. After the deemed sale election, so long as we do not become a PFIC in a subsequent taxable year, the U.S. Holder’s ordinary shares or ADSs with respect to which such election was made will not be treated as shares in a PFIC and the U.S. Holder will not be subject to the rules described below with respect to any “excess distribution” the U.S. Holder receives from us or any gain from an actual sale or other disposition of the ordinary shares or ADSs. U.S. Holders should consult their tax advisors as to the possibility and consequences of making a deemed sale election if we cease to be a PFIC and such election becomes available.

For each taxable year that we are treated as a PFIC with respect to a U.S. Holder that owns ordinary shares or ADSs, such U.S. Holder will be subject to special tax rules with respect to any “excess distribution” such U.S. Holder receives and any gain such U.S. Holder recognizes from a sale or other disposition (including, under certain circumstances, a pledge) of ordinary shares or ADSs, unless (i) such U.S. Holder makes a QEF Election or (ii) our ordinary shares or ADSs constitute “marketable” securities, and such U.S. Holder makes a mark-to-market election as discussed below. Distributions that such a U.S. Holder receives in a taxable year that are greater than 125% of the

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average annual distributions such U.S. Holder received during the shorter of the three preceding taxable years or the U.S. Holder’s holding period for the ordinary shares or ADSs will be treated as an excess distribution. Under these special tax rules:

•the excess distribution or gain will be allocated ratably over a U.S. Holder’s holding period for the ordinary shares or ADSs;

•the amount allocated to the taxable year of disposition or distribution, and any taxable year prior to the first taxable year in which we became a PFIC, will be treated as ordinary income; and

•the amount allocated to each other year will be subject to the highest tax rate in effect for that year for individuals or corporations, as appropriate, and the interest charge generally applicable to underpayments of tax will be imposed on the resulting tax attributable to each such year.

The tax liability for amounts allocated to years prior to the year of disposition or “excess distribution” cannot be offset by any net operating losses for such years, and gains (but not losses) realized on the sale of the ordinary shares or ADSs cannot be treated as capital, even if a U.S. Holder holds the ordinary shares or ADSs as capital assets.

If we are a PFIC, a U.S. Holder of ordinary shares or ADSs will generally be subject to similar rules with respect to distributions we receive from, and our dispositions of the stock of, any of our direct or indirect subsidiaries that also are PFICs, as if such distributions were indirectly received by, and/or dispositions were indirectly carried out by, such U.S. Holder. U.S. Holders should consult their tax advisors regarding the application of the PFIC rules to our subsidiaries.

U.S. Holders can avoid the interest charge on excess distributions or gain relating to the ordinary shares or ADSs by making a mark-to-market election with respect to the ordinary shares or ADSs, provided that the ordinary shares or ADSs are “marketable.” Ordinary shares or ADSs will be marketable if they are “regularly traded” on certain U.S. stock exchanges or on a foreign stock exchange that meets certain conditions. For these purposes, the ordinary shares or ADSs will be considered regularly traded during any calendar year during which they are traded, other than in de minimis quantities, on at least 15 days during each calendar quarter. Any trades that have as their principal purpose meeting this requirement will be disregarded. Our ADSs have been listed on Nasdaq, which is a qualified exchange for these purposes. Consequently, if our ADSs remain listed on Nasdaq and are regularly traded, and you are a holder of ADSs, we expect the mark-to-market election would be available to you if we are a PFIC. Each U.S. Holder should consult its tax advisor as to the whether a mark-to-market election is available or advisable with respect to the ordinary shares or ADSs.

A U.S. Holder that makes a mark-to-market election must include in ordinary income for each year an amount equal to the excess, if any, of the fair market value of the ordinary shares or ADSs at the close of the taxable year over the U.S. Holder’s adjusted tax basis in the ordinary shares or ADSs. An electing holder may also claim an ordinary loss deduction for the excess, if any, of the U.S. Holder’s adjusted basis in the ordinary shares or ADSs over the fair market value of the ordinary shares or ADSs at the close of the taxable year, but this deduction is allowable only to the extent of any net mark-to-market gains for prior years. Gains from an actual sale or other disposition of the ordinary shares or ADSs will be treated as ordinary income, and any losses incurred on a sale or other disposition of the ordinary shares or ADSs will be treated as an ordinary loss to the extent of any net mark-to-market gains for prior years. Once made, the election cannot be revoked without the consent of the IRS unless the ordinary shares or ADSs cease to be marketable.

However, a mark-to-market election generally cannot be made for equity interests in any lower-tier PFICs that we own, unless shares of such lower-tier PFIC are themselves “marketable.” As a result, even if a U.S. Holder validly makes a mark-to-market election with respect to our ordinary shares or ADSs, the U.S. Holder may continue to be subject to the PFIC rules (described above) with respect to its indirect interest in any of our investments that are treated as an equity interest in a PFIC for U.S. federal income tax purposes. U.S. Holders should consult their tax advisors to determine whether any of these elections would be available and if so, what the consequences of the alternative treatments would be in their particular circumstances.

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We do not intend to provide information necessary for U.S. Holders to make QEF elections which, if available, would result in tax treatment different from the general tax treatment for PFICs described above.

Unless otherwise provided by the U.S. Treasury, each U.S. shareholder of a PFIC is required to file an annual report containing such information as the U.S. Treasury may require. A U.S. Holder’s failure to file the annual report will cause the statute of limitations for such U.S. Holder’s U.S. federal income tax return to remain open with regard to the items required to be included in such report until three years after the U.S. Holder files the annual report, and, unless such failure is due to reasonable cause and not willful neglect, the statute of limitations for the U.S. Holder’s entire U.S. federal income tax return will remain open during such period. U.S. Holders should consult their tax advisors regarding the requirements of filing such information returns under these rules.

WE STRONGLY URGE YOU TO CONSULT YOUR TAX ADVISOR REGARDING THE APPLICATION OF THE PFIC RULES TO YOUR INVESTMENT IN OUR SECURITIES.

Taxation of Distributions

Subject to the discussion above under “Passive Foreign Investment Company Rules,” distributions paid on ordinary shares or ADSs, other than certain pro rata distributions of ordinary shares or ADSs, will generally be treated as dividends to the extent paid out of our current or accumulated earnings and profits (as determined under U.S. federal income tax principles). Because we may not calculate our earnings and profits under U.S. federal income tax principles, we expect that distributions generally will be reported to U.S. Holders as dividends. Subject to applicable limitations and the discussions above regarding concerns expressed by the U.S. Treasury, dividends paid to certain non-corporate U.S. Holders may be taxable at preferential rates applicable to “qualified dividend income” if we are a “qualified foreign corporation” and certain other requirements are met. However, the qualified dividend income treatment will not apply if we are treated as a PFIC with respect to the U.S. Holder. The amount of the dividend will be treated as foreign-source dividend income to U.S. Holders and will not be eligible for the dividends-received deduction generally available to U.S. corporations under the Code. Dividends will generally be included in a U.S. Holder’s income on the date of the U.S. Holder’s receipt of the dividend. The amount of any dividend income paid in foreign currency will be the U.S. dollar amount calculated by reference to the exchange rate in effect on the date of actual or constructive receipt, regardless of whether the payment is in fact converted into U.S. dollars. If the dividend is converted into U.S. dollars on the date of receipt, a U.S. Holder should not be required to recognize foreign currency gain or loss in respect of the dividend income. A U.S. Holder may have foreign currency gain or loss if the dividend is converted into U.S. dollars after the date of receipt. Such gain or loss would generally be treated as U.S.-source ordinary income or loss. The amount of any distribution of property other than cash (and other than certain pro rata distributions of ordinary shares or ADSs or rights to acquire ordinary shares or ADSs) will be the fair market value of such property on the date of distribution.

For foreign tax credit limitation purposes, our dividends will generally be treated as passive category income. Because no UK income taxes will be withheld from dividends on ordinary shares or ADSs, there will be no creditable foreign taxes associated with any dividends that a U.S. Holder will receive. The rules governing foreign tax credits are complex and U.S. Holders should therefore consult their tax advisers regarding the effect of the receipt of dividends for foreign tax credit limitation purposes.

Constructive Dividends on Pre-Funded Warrants

Under Section 305 of the Code, an adjustment to (or failure to adjust) the number of ADSs representing ordinary shares that will be issued on the exercise of the pre-funded warrants, or an adjustment to (or failure to adjust) the exercise price of the pre-funded warrants, may be treated as a constructive distribution to a U.S. Holder of the pre-funded warrants, if, and to the extent that, such adjustment (or failure to adjust) has the effect of increasing such U.S. Holder’s proportionate interest in our assets or earnings and profits as determined under U.S. federal income tax principles, depending on the circumstances of such adjustment (for example, if such adjustment is to compensate for a distribution of cash or other property to our shareholders). U.S. Holders should consult their tax advisors as to (i) whether a constructive dividend deemed paid to a non-corporate U.S. Holder would be eligible for the preferential rates of U.S. federal income tax applicable in respect of certain dividends received, (ii) whether a corporate Non-U.S. Holder would be entitled to claim the dividends received deduction with respect to any such

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constructive dividends, and (iii) the general treatment of constructive distributions under their particular circumstances. Because a constructive dividend deemed received by a U.S. Holder would not give rise to any cash from which any applicable withholding could be satisfied, if backup withholding is paid on behalf of a U.S. Holder (because such U.S. Holder failed to establish an exemption from backup withholding), such backup withholding may be set off against payments on the ordinary shares or ADSs or offset against other assets of such U.S. Holder. Generally, a U.S. Holder’s adjusted tax basis in a pre-funded warrant should be increased to the extent any such constructive distribution is treated as a dividend. U.S. Holders should consult their tax advisors on the impact a constructive distribution may have on their holding period in the securities.

Exercise, Lapse, or Redemption of a Pre-Funded Warrant

Except as discussed below with respect to the cashless exercise of a pre-funded warrant, a U.S. Holder generally will not recognize gain or loss upon the exercise of a pre-funded warrant. A U.S. Holder’s tax basis in an ADS received upon exercise of the pre-funded warrant generally will be an amount equal to the sum of the U.S. Holder’s initial investment in the pre-funded warrant and the exercise price. The U.S. Holder’s holding period for the ADS received upon exercise of the pre-funded warrant generally will commence on the date of exercise of the pre-funded warrant or the date following the date of exercise of the pre-funded warrant; however, in either case the holding period will not include the period during which the U.S. Holder held the pre-funded warrant. If a pre-funded warrant is allowed to lapse unexercised, a U.S. Holder generally will recognize a capital loss equal to such U.S. Holder’s tax basis in the pre-funded warrant.

The tax consequences of a cashless exercise of a pre-funded warrant are not clear under current tax law. A cashless exercise may be tax-free, either because the exercise is not a gain realization event or because the exercise is treated as a recapitalization for U.S. federal income tax purposes. In either tax-free situation, a U.S. Holder’s basis in the ADSs received would equal the holder’s basis in the pre-funded warrants used to effect the cashless exercise. If the cashless exercise is not treated as a gain realization event, a U.S. Holder’s holding period in the ADSs generally would be treated as commencing on the date of exercise of the pre-funded warrant or the date following the date of exercise of the pre-funded warrant; however, in either case the holding period will not include the period during which the U.S. Holder held the pre-funded warrant. If the cashless exercise were treated as a recapitalization, the holding period of the ADSs would include the holding period of the pre-funded warrant.

It is also possible that a cashless exercise could be treated in part as a taxable exchange in which gain or loss would be recognized. In such event, a portion of the pre-funded warrants to be exercised on a cashless basis could, for U.S. federal income tax purposes, be deemed to have been surrendered in consideration for the exercise price of the remaining pre-funded warrants, which would be deemed to be exercised. For this purpose, a U.S. Holder could be deemed to have surrendered pre-funded warrants having an aggregate fair market value equal to the exercise price for the total number of pre-funded warrants to be deemed exercised. The U.S. Holder would recognize capital gain or loss in an amount equal to the difference between the fair market value of the pre-funded warrants deemed surrendered and the U.S. Holder’s tax basis in such pre-funded warrants. In this case, a U.S. Holder’s tax basis in the ADSs received would equal the sum of the U.S. Holder’s initial investment in the pre-funded warrants deemed exercised and the exercise price of such pre-funded warrants. A U.S. Holder’s holding period for the ADSs in such case generally would commence on the date following the date of exercise (or possibly the date of exercise) of the pre-funded warrant.

Due to the absence of authority on the U.S. federal income tax treatment of a cashless exercise, there can be no assurance which, if any, of the alternative tax consequences and holding periods described above would be adopted by the IRS or a court of law. Accordingly, U.S. Holders should consult their tax advisors regarding the tax consequences of a cashless exercise.

Sale or Other Taxable Disposition of Securities

Subject to the discussion above under “Passive Foreign Investment Company Rules,” gain or loss realized on the sale or other taxable disposition of our securities (other than the disposition of warrants by exercise) will be capital gain or loss, and will be long-term capital gain or loss if the U.S. Holder held such securities for more than one year at the time of sale or other taxable disposition. The amount of the gain or loss will equal the difference

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between the U.S. Holder’s tax basis in the securities disposed of and the amount realized on the disposition, in each case as determined in U.S. dollars. This gain or loss will generally be U.S.-source gain or loss for foreign tax credit purposes. Subject to the PFIC rules described above, long-term capital gains recognized by certain non-corporate U.S. Holders (including individuals) will be, under current law, subject to reduced rates of U.S. federal income tax. The deductibility of capital losses is subject to limitations.

If the consideration received by a U.S. Holder is not paid in U.S. dollars, the amount realized will be the U.S. dollar value of the payment received determined by reference to the spot rate of exchange on the date of the sale or other disposition. However, if the securities disposed of are treated as traded on an “established securities market” and you are either a cash basis taxpayer or an accrual basis taxpayer that has made a special election (which must be applied consistently from year to year and cannot be changed without the consent of the IRS), you will determine the U.S. dollar value of the amount realized in a non-U.S. dollar currency by translating the amount received at the spot rate of exchange on the settlement date of the sale. If you are an accrual basis taxpayer that is not eligible to or does not elect to determine the amount realized using the spot rate on the settlement date, you will recognize foreign currency gain or loss to the extent of any difference between the U.S. dollar amount realized on the date of sale or disposition and the U.S. dollar value of the currency received at the spot rate on the settlement date.

WE STRONGLY URGE YOU TO CONSULT YOUR TAX ADVISOR REGARDING THE PARTICULAR TAX CONSEQUENCES APPLICABLE TO YOU RELATING TO THE ACQUISITION, OWNERSHIP AND DISPOSITION OF OUR SECURITIES, INCLUDING THE APPLICABILITY OF U.S. FEDERAL, STATE AND LOCAL TAX LAWS AND THE CONSEQUENCES OF ANY PROPOSED CHANGE IN APPLICABLE LAWS.

Information Reporting and Backup Withholding

Payments of dividends (including constructive dividends) and sales proceeds that are made within the United States or through certain U.S.-related financial intermediaries generally are subject to information reporting, and may be subject to backup withholding, unless (i) the U.S. Holder is a corporation or other exempt recipient or (ii) in the case of backup withholding, the U.S. Holder provides a correct taxpayer identification number and certifies that it is not subject to backup withholding on a duly executed IRS Form W-9 or otherwise establishes an exemption.

The amount of any backup withholding from a payment to a U.S. Holder may be allowed as a credit against the U.S. Holder’s U.S. federal income tax liability and may entitle the U.S. Holder to a refund, provided that the required information is timely furnished to the IRS.

Information with Respect to Foreign Financial Assets

Certain U.S. Holders who are individuals (and, under regulations, certain entities) may be required to report information relating to the ordinary shares or ADSs, subject to certain exceptions (including an exception for ordinary shares or ADSs held in accounts maintained by certain U.S. financial institutions), by filing IRS Form 8938 (Statement of Specified Foreign Financial Assets) with their federal income tax return. Such U.S. Holders who fail to timely furnish the required information may be subject to a penalty. Additionally, if a U.S. Holder does not file the required information, the statute of limitations with respect to tax returns of the U.S. Holder to which the information relates may not close until three years after such information is filed. U.S. Holders should consult their tax advisers regarding their reporting obligations with respect to their ownership and disposition of the ordinary shares or ADSs.

UK taxation

The following is intended as a general guide to current UK tax law and HM Revenue & Customs, or HMRC, published practice (which is not binding) applying as at the date of this prospectus (both of which are subject to change at any time, possibly with retrospective effect) relating to the holding of ADSs and pre-funded warrants. It does not constitute legal or tax advice and does not purport to be a complete analysis of all UK tax considerations relating to the holding of ADSs or warrants, or all of the circumstances in which holders of ADSs or pre-funded warrants may benefit from an exemption or relief from UK taxation. It is written on the basis that we do not (and will not) directly or indirectly derive 75% or more of our qualifying asset value from UK land, and that we are and

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will remain solely resident in the UK for tax purposes and will therefore be subject to the UK tax regime and not the U.S. tax regime save as set out above under “-U.S. federal income tax considerations for U.S. holders.”

Except to the extent that the position of non-UK resident persons is expressly referred to, this guide relates only to persons who are resident (and in the case of individuals, domiciled or deemed domiciled) for tax purposes solely in the UK and who do not have a permanent establishment, branch or agency (or equivalent) in any other jurisdiction with which the holding of our ADSs is connected, or UK Holders, who are absolute beneficial owners of our ADSs (and do not hold our ADSs through an Individual Savings Account or a Self-Invested Personal Pension).

This guide may not relate to certain classes of UK Holders, such as (but not limited to):

•persons who are connected with us;

•financial institutions;

•insurance companies;

•charities or tax-exempt organizations;

•collective investment schemes;

•pension schemes;

•market makers, intermediaries, brokers or dealers in securities or persons who hold ADSs otherwise than as an investment;

•persons who have (or are deemed to have) acquired their ADSs or warrants by virtue of an office or employment or who are or have been our officers or employees or of any of our affiliates; and

•individuals who are subject to UK taxation on a remittance basis or to whom split-year treatment applies.

The decision of the First-tier Tribunal (Tax Chamber) in HSBC Holdings PLC and The Bank of New York Mellon Corporation v HMRC (2012) cast some doubt on whether a holder of a depositary receipt is the beneficial owner of the underlying shares. However, based on published HMRC guidance we would expect that HMRC will regard a holder of ADSs as holding the beneficial interest in the underlying shares and therefore these paragraphs assume that a holder of ADSs is the beneficial owner of the underlying ordinary shares and any dividends paid in respect of the underlying ordinary shares (where the dividends are regarded for UK purposes as that person’s own income) for UK direct tax purposes.

THESE PARAGRAPHS ARE A SUMMARY OF CERTAIN UK TAX CONSIDERATIONS AND ARE INTENDED AS A GENERAL GUIDE ONLY. IT IS RECOMMENDED THAT ALL HOLDERS OF ADSs OR WARRANTS OBTAIN ADVICE AS TO THE CONSEQUENCES OF THE ACQUISITION, OWNERSHIP AND DISPOSAL OF OUR ADSs OR PRE-FUNDED WARRANTS IN THEIR OWN PARTICULAR CIRCUMSTANCES FROM THEIR TAX ADVISORS. IN PARTICULAR, NON-UK RESIDENT OR DOMICILED PERSONS OR PERSONS SUBJECT TO TAXATION IN ANY JURISDICTION OTHER THAN THE UK ARE ADVISED TO CONSIDER THE POTENTIAL IMPACT OF ANY RELEVANT DOUBLE TAXATION AGREEMENTS.

Dividends

Withholding Tax

Dividends that we pay will not be subject to any withholding or deduction for or on account of UK tax.

Income Tax

An individual UK Holder may, depending on his or her particular circumstances, be subject to UK tax on dividends received from us. An individual holder of ADSs who is not resident for tax purposes in the UK should not

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be chargeable to UK income tax on dividends received from us unless he or she carries on (whether solely or in partnership) a trade, profession or vocation in the UK through a permanent establishment, branch or agency to which our ADSs are attributable. There are certain exceptions for trading in the UK through independent agents, such as some brokers and investment managers.

Dividend income is treated as the top slice of the total income chargeable to UK income tax for an individual UK Holder. An individual UK Holder who receives a dividend in the 2024/2025 tax year will be entitled to a tax-free allowance of £500. Income within the dividend allowance counts towards an individual’s basic or higher rate limits and may, therefore, affect the level of personal allowance to which they are entitled. Dividend income in excess of this tax-free allowance will (subject to the availability of any income tax personal allowance) be taxed at 8.75% (for the tax year 2024/2025) to the extent the excess amount falls within the basic rate band, 33.75% (for the tax year 2024/2025) to the extent the excess amount falls within the higher rate band, and 39.35% (for the tax year 2024/2025) to the extent the excess amount falls within the additional rate band.

Corporation Tax

A corporate holder of ADSs who is not resident for tax purposes in the UK should not be chargeable to UK corporation tax on dividends received from us unless it carries on (whether solely or in partnership) a trade in the UK through a permanent establishment to which our ADSs are attributable.

Corporate UK Holders should not be subject to UK corporation tax on any dividend received from us so long as the dividends qualify for exemption, which should be the case, although certain conditions must be met. It should be noted that the exemptions, whilst of wide application, are not comprehensive and are subject to anti-avoidance rules in relation to a dividend. If the conditions for the exemption are not satisfied, or such anti-avoidance provisions apply or such UK Holder elects for an otherwise exempt dividend to be taxable, UK corporation tax will be chargeable on the amount of any dividends (at the rate of 25% for the tax year 2024/2025 for companies with profits of more than £250,000 whilst the prior rate of 19% will apply to companies with profits not exceeding £50,000 with a tapered rate applying to profits between £50,000 and £250,000).

Chargeable Gains and ADSs

A disposal or deemed disposal of ADSs by a UK Holder may, depending on the UK Holder’s circumstances and subject to any available exemptions or reliefs (such as the annual exemption), give rise to a chargeable gain or an allowable loss for the purposes of UK capital gains tax and corporation tax on chargeable gains.

If an individual UK Holder who is subject to UK income tax at either the higher or the additional rate is liable to UK capital gains tax on the disposal of ADSs, the current applicable rate will be 24% (for the period from 30 October 2024 to the end of the 2024/2025 tax year). For an individual UK Holder who is subject to UK income tax at the basic rate and liable to UK capital gains tax on such disposal, the current applicable rate would be 18% (for the period from 30 October 2024 to the end of the 2024/2025 tax year), save to the extent that any capital gains when aggregated with the UK Holder’s other taxable income and gains in the relevant tax year exceed the unused basic rate tax band. In that case, the rate currently applicable to the excess would be 24% (for the period from 30 October 2024 to the end of the 2024/2025 tax year).

If a corporate UK Holder becomes liable to UK corporation tax on the disposal (or deemed disposal) of ADSs, the main rate of UK corporation tax would apply (at 25% for the tax year 2024/2025 for companies with profits of more than £50,000 whilst the prior rate of 19% will apply to companies with profits not exceeding £250,000 with a tapered rate applying to profits between £50,000 and £250,000).

A holder of ADSs that is not resident for tax purposes in the UK should not normally be liable to UK capital gains tax or corporation tax on chargeable gains on a disposal (or deemed disposal) of ADSs, unless the person is carrying on (whether solely or in partnership) a trade, profession or vocation in the UK through a branch or agency (or, in the case of a corporate holder of ADSs, through a permanent establishment) to which our ADSs are attributable. However, an individual holder of ADSs who has ceased to be resident for tax purposes in the UK or is treated as resident outside the UK for the purposes of a double taxation treaty for a period of five years or less and who disposes of ADSs during that period of temporary non-residence may be liable on his or her return to the UK

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(or upon ceasing to be regarded as resident outside the UK for the purposes of double taxation treaty) to UK tax on any capital gain realized (subject to any available exemption or relief) despite the fact that the individual may not be resident in the UK at the time of the disposal.

Chargeable Gains and Pre-Funded Warrants

For UK corporate holders of pre-funded warrants, the precise UK corporation tax treatment of pre-funded warrants is dependent on the accounting treatment applied to the pre-funded warrants including whether or not the pre-funded warrants are considered to constitute derivative contracts for UK tax purposes. UK corporate holders of pre-funded warrants who consider that any of the pre-funded warrants may constitute derivative contracts for UK tax purposes should consult with their tax advisors and accountants as to the tax implications of such treatment.

UK non-corporate holders, and pre-funded warrants not treated as derivative contracts for UK tax purposes

Where (for UK corporate holders of warrants) a warrant does not constitute a derivative contract for UK tax purposes, or for UK non-corporate holders of pre-funded warrants, then (depending on the circumstances) neither the grant nor the exercise of a pre-funded warrant should generally give rise to a UK chargeable gains / capital gains tax charge, and the relevant UK holder’s base cost in the pre-funded warrant, or (following exercise) the asset which was the subject of the pre-funded warrant should broadly comprise, in the case of the pre-funded warrant, any amounts paid by the relevant UK holder for the acquisition of the pre-funded warrant, and in the case of the asset which was the subject of the pre-funded warrant, any such amounts, together with any amounts paid for the exercise of the relevant pre-funded warrant.

A disposal or deemed disposal of a pre-funded warrant or (following the exercise of a pre-funded warrant) the asset underlying the warrant by a UK Holder may, depending on the UK Holder’s circumstances and subject to any available exemptions or reliefs (such as the annual capital gains tax exemption for UK tax resident individuals), give rise to a chargeable gain or an allowable loss for the purposes of UK corporation tax on chargeable gains and/or UK capital gains tax.

If an individual UK Holder who is subject to UK income tax at either the higher or the additional rate is liable to UK capital gains tax on the disposal of our pre-funded warrants or (following exercise of a pre-funded warrant) the underlying assets, the current applicable rate would be 24% (for the period from 30 October 2024 to the end of the 2024/2025 tax year). For an individual UK Holder who is subject to UK income tax at the basic rate and liable to UK capital gains tax on such disposal, the current applicable rate would be 18% (for the period from 30 October 2024 to the end of the 2024/2025 tax year), save to the extent that any capital gains when aggregated with the UK Holder’s other taxable income and gains in the relevant tax year exceed the unused basic rate tax band. In that case, the rate currently applicable to the excess would be 24% (for the period from 30 October 2024 to the end of the 2024/2025 tax year).

If a corporate UK Holder becomes liable to UK corporation tax on the disposal (or deemed disposal) of a warrant or (following the exercise of a warrant) the asset underlying the pre-funded warrant, the main rate of UK corporation tax should apply (at 25% for the tax year 2024/2025 for companies with profits of more than £50,000 whilst the prior rate of 19% will apply to companies with profits not exceeding £250,000 with a tapered rate applying to profits between £50,000 and £250,000).

A holder of pre-funded warrants (or the underlying asset thereof) that is not resident for tax purposes in the UK should not normally be liable to UK capital gains tax or corporation tax on chargeable gains on a disposal (or deemed disposal) of a pre-funded warrant or (following exercise) the asset underlying the warrant, unless the person is carrying on (whether solely or in partnership) a trade, profession or vocation in the UK through a branch or agency (or, in the case of a corporate holder of warrants or (following exercise) the underlying assets, through a permanent establishment) to which our pre-funded warrants (or, following an exercise, the underlying assets) are attributable. However, an individual holder of pre-funded warrants who has ceased to be resident for tax purposes in the UK or is treated as resident outside the UK for the purposes of a double taxation treaty for a period of five years or less and who disposes of pre-funded warrants (or, following exercise, the underlying asset) during that period of temporary non-residence may be liable on his or her return to the UK (or upon ceasing to be regarded as resident outside the UK for the purposes of double taxation treaty) to UK tax on any capital gain realized (subject to any

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available exemption or relief) despite the fact that the individual may not be resident in the UK at the time of the disposal.

The UK corporation tax, capital gains tax and income tax position in respect of pre-funded warrants is complex, this is not tax advice and, as stated above, reference should always be made to specific advice from your tax advisor.

Stamp Duty and Stamp Duty Reserve Tax – ADRs

The discussion below relates to the holders of our ordinary shares or ADSs wherever resident, however it should be noted that special rules may apply to certain persons such as market makers, brokers, dealers or intermediaries.

Issue of Ordinary Shares

No UK stamp duty or stamp duty reserve tax, or SDRT, is generally payable on the issue of the ordinary shares underlying our ADSs.

Transfers of Ordinary Shares

An unconditional agreement to transfer ordinary shares will normally give rise to a charge to SDRT at the rate of 0.5% of the amount or value of the consideration payable for the transfer. The purchaser of the shares is liable for the SDRT. Transfers of ordinary shares in certificated form are generally also subject to stamp duty at the rate of 0.5% of the amount or value of the consideration given for the transfer (or, in certain circumstances and if it is higher, the market value of the ordinary shares (in each case, rounded up to the next £5.00)). Stamp duty is normally paid by the purchaser. The charge to SDRT will be cancelled or, if already paid, repaid (generally with interest), where a transfer instrument has been duly stamped within six years of the charge arising, (either by paying the stamp duty or by claiming an appropriate relief) or if the instrument is otherwise exempt from stamp duty.

Clearance Services and Depositary Receipts

Under current UK tax law and published HMRC practice, no SDRT (and, where the transfer is effected by a written instrument, stamp duty) is generally payable where an issue or transfer of ordinary shares (including an unconditional agreement to transfer ordinary shares to a clearance service or a depositary receipt system (including to a nominee or agent for, a person whose business is or includes the issue of depositary receipts or the provision of clearance services)) is an integral part of an issue of share capital, unless the clearance service has made and maintained an election under section 97A of the UK Finance Act 1986, or a section 97A election. It is understood that HMRC regards the facilities of DTC as a clearance service for these purposes and we are not aware of any section 97A election having been made by DTC.

Any stamp duty or SDRT payable on a transfer of ordinary shares to a depositary receipt system or clearance service, or in respect of a transfer within a depositary receipt system or clearance service, will strictly be accountable by the clearance service or depositary receipt system operator or their nominee, as the case may be, but will in practice generally be paid by the transferors or participants in the clearance service or depositary receipt system. Specific professional advice should be sought before incurring or reimbursing the costs of a 1.5% stamp duty or SDRT charge in any circumstance.

Issue of ADSs

No UK stamp duty or SDRT is payable on the issue of our ADSs.

Transfers of ADSs

No UK SDRT should be required to be paid in respect of a paperless transfer of ADSs through the facilities of DTC, provided that no section 97A election has been made by DTC, and such ADSs are held through DTC at the time of any agreement for their transfer.

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No UK stamp duty will in practice be payable on a written instrument transferring an ADS provided that the instrument of transfer is executed and remains at all times outside the United Kingdom. Where these conditions are not met, the transfer of, or agreement to transfer, an ADS could, depending on the circumstances, attract a charge to UK stamp duty at the rate of 0.5% of the amount or value of the consideration. If it is necessary to pay stamp duty, it may also be necessary to pay interest and penalties.

Issue or Transfers of ADRs

On the basis of current published HMRC guidance, an ADR is not regarded as stock or marketable security for the purposes of UK stamp duty or a chargeable security for the purposes of UK SDRT. As such, no UK stamp duty or SDRT should be required to be paid on the issue or transfer of (including an agreement to transfer) ADRs in the Company.

Stamp Duty and Stamp Duty Reserve Tax – Pre-Funded Warrants

The UK stamp duty and UK stamp duty reserve tax implications of both the issue, the exercise and the transfer of pre-funded warrants is complex. Specific professional advice should be sought before incurring or reimbursing the costs of a UK stamp duty or UK SDRT charge in any circumstances relating to a warranty (including the issuance, exercise or transfer of any pre-funded warrant).

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LEGAL MATTERS

The validity of the securities being sold in this offering and certain other matters of U.S. federal law and English law will be passed upon for us by Goodwin Procter LLP, New York, New York and Goodwin Procter (UK) LLP, London, United Kingdom, respectively. The underwriters are being represented by Paul Hastings LLP, New York, New York with respect to U.S. federal law.

EXPERTS

The financial statements incorporated in this prospectus supplement by reference to the Annual Report on Form 10-K for the year ended December 31, 2024 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

The registered business address of PricewaterhouseCoopers LLP is 1 Embankment Place, London, WC2N 6RH, United Kingdom.

WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a registration statement (including amendments and exhibits to the registration statement) on Form S-3 (File No. 333-285297) under the Securities Act. We have also filed related registration statements on Form F-6 (File No. 333-248514) and Form F-6EF (File No. 333-279431) with the SEC to register our ADSs. This prospectus supplement does not contain all of the information included in the registration statement and the exhibits and schedules to the registration statement. Certain information is omitted and you should refer to the registration statement and its exhibits and schedules for that information. If a document has been filed as an exhibit to the registration statement, we refer you to the copy of the document that has been filed. Each statement in this prospectus supplement relating to a document filed as an exhibit is qualified in all respects by the filed exhibit.

We file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public at the SEC’s website at http://www.sec.gov. We maintain a corporate website at www.compasspathways.com. Information contained in, or that can be accessed through, our website is not a part of, and shall not be incorporated by reference into, this prospectus supplement. We have included our website address in this prospectus supplement solely as an inactive textual reference.

We will send the depositary a copy of all notices of shareholders meetings and other reports, communications and information that are made generally available to shareholders. The depositary has agreed to mail to all holders of ADSs a notice containing the information (or a summary of the information) contained in any notice of a meeting of our shareholders received by the depositary and will make available to all holders of ADSs such notices and all such other reports and communications received by the depositary.

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INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

We have elected to incorporate the following documents into this prospectus supplement, together with all exhibits filed therewith or incorporated therein by reference, to the extent not otherwise amended or superseded by the contents of this prospectus supplement:

•Our Annual Report on Form 10-K for the year ended December 31, 2024, filed with the SEC on February 27, 2025;

•Our Quarterly Reports on Form 10-Q for the periods ended March 31, 2025, June 30, 2025 and September 30, 2025, filed with the SEC on May 8, 2025, July 31, 2025, and November 4, 2025, respectively;

•Our Definitive Proxy Statement on Schedule 14A filed with the SEC on April 28, 2025 (solely to the extent specifically incorporated by reference into the Annual Report on Form 10-K for the year ended December 31, 2024);

•Our Current Reports on Form 8-K (other than information furnished rather than filed) filed on January 10, 2025, April 16, 2025, June 13, 2025, June 23, 2025, July 29, 2025, October 29, 2025, January 7, 2026 and February 17, 2026; and

•The description of our ordinary shares and ADSs contained in our Registration Statement on Form 8-A, as filed with the SEC under Section 12(b) of the Exchange Act on September 15, 2020, including any amendment or report filed for the purpose of updating such description.

The information incorporated by reference is an important part of this prospectus supplement. In addition, all documents we file with the SEC (File No. 001-39522) pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, except as to any portion of any report or documents that is not deemed filed under such provisions, on or after the date of this prospectus supplement until the earlier of the date on which all of the securities registered hereunder have been sold or all offerings under this prospectus supplement are terminated, shall be deemed incorporated by reference in this prospectus supplement.

Any statement contained in a document incorporated by reference herein shall be deemed to be modified or superseded for all purposes to the extent that a statement contained in this prospectus supplement or in any other subsequently filed document which is also incorporated or deemed to be incorporated by reference, modifies or supersedes such statement. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement. You may request a copy of these filings (other than an exhibit to a filing unless that exhibit is specifically incorporated by reference into that filing) at no cost by writing to us at the following address: COMPASS Pathways plc, Attention: Investor Relations, 3rd Floor, 1 Ashley Road, Altrincham, Cheshire, United Kingdom, WA14 2DT or calling +1 (716) 676-6461. In addition, copies of the documents incorporated herein by reference may be accessed, free of charge, on the SEC’s website at www.sec.gov, or on our website at www.compasspathways.com. Information contained on our website is not incorporated by reference into this prospectus supplement, and you should not consider any information on, or that can be accessed from, our website as part of this prospectus supplement or the accompanying base prospectus.

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PROSPECTUS

$400,000,000

Ordinary Shares

American Depositary Shares representing Ordinary Shares

Debt Securities

Warrants

Units

Offered by the Registrant and

5,951,024 Ordinary Shares Offered by Selling Security Holders

We may offer and sell from time to time up to $400,000,000 in aggregate principal amount of our: ordinary shares, each of which may be represented by one American Depositary Share; senior or subordinated debt securities; warrants to purchase any securities that may be sold under this prospectus; units or any combination of these securities as described in this prospectus. This prospectus may also be used to offer up to 5,951,024 ordinary shares for the accounts of existing security holders, which we refer to in this prospectus as the “selling security holders.” We will describe in a prospectus supplement the securities we and/or our selling security holders are offering and selling, as well as the specific terms of the securities. We may also authorize one or more free writing prospectuses to be provided to you in connection with each offering of the securities. Any prospectus supplement and related free writing prospectuses may also add to, update or change information contained in this prospectus. For more detailed information, see "Plan of Distribution" on page 64. We will not receive any proceeds from the sale of securities by our selling security holders.

We and/or our selling security holders may offer these securities in amounts, at prices and on terms determined at the time of offering. We and/or our selling security holders may sell the securities through public or private transactions directly to you, through agents, or through underwriters and dealers on or off the Nasdaq Global Select Market, or Nasdaq. If we and/or our selling security holders use agents, underwriters or dealers to sell the securities, we will name them and describe their compensation in a prospectus supplement. You should read this prospectus and the accompanying prospectus supplement and any free writing prospectus, as well as the documents incorporated by reference, or deemed incorporated by reference into this prospectus, carefully before you invest.

Our American Depositary Shares representing ordinary shares are traded on Nasdaq under the symbol “CMPS”. Separate registration statements on Form F-6, as amended, for the registration of American Depositary Shares issuable upon deposit of the ordinary shares were previously filed with the Securities and Exchange Commission and were effective on September 17, 2020 (File No. 333-248514) and May 15, 2024 (File No. 333-279431). If we decide to list any of these other securities on a national securities exchange upon issuance, the applicable prospectus supplement to this prospectus will identify the exchange and the date when we expect trading to begin. On February 25, 2025, the closing price of our American Depositary Shares on Nasdaq was $3.65 per ADS.

Investing in our securities involves risks. See “Risk Factors” beginning on page 5 of this prospectus and in the applicable prospectus supplement and any related free writing prospectus and in the documents incorporated by reference or deemed to be incorporated by reference into this prospectus or the applicable prospectus supplement for certain risks you should consider. You should read the entire prospectus carefully before you make your investment decision.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is May 7, 2025.

Table of Contents


			Page
ABOUT THIS PROSPECTUS			1
PROSPECTUS SUMMARY			3
RISK FACTORS			5
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS			6
SECURITIES WE MAY OFFER			9
DESCRIPTION OF SHARE CAPITAL AND ARTICLES OF ASSOCIATION			10
DIFFERENCES IN CORPORATE LAW			23
DESCRIPTION OF AMERICAN DEPOSITARY SHARES			31
DESCRIPTION OF DEBT SECURITIES			42
DESCRIPTION OF WARRANTS			55
DESCRIPTION OF UNITS			56
TAXATION			57
USE OF PROCEEDS			61
DIVIDEND POLICY			62
SELLING SECURITY HOLDERS			63
PLAN OF DISTRIBUTION			64
LEGAL MATTERS			67
EXPERTS			67
SERVICE OF PROCESS AND ENFORCEMENT OF LIABILITIES			68
WHERE YOU CAN FIND MORE INFORMATION			70
INCORPORATION BY REFERENCE			71


Service						Fees
•Issuance of ADSs (e.g., an issuance of ADS upon a deposit of ordinary shares or upon a change in the ADS(s)-to-ordinary shares ratio), excluding ADS issuances as a result of distributions of ordinary shares						Up to $0.05 per ADS issued

•Cancellation of ADSs (e.g., a cancellation of ADSs for delivery of deposited property or upon a change in the ADS(s)-to-ordinary shares ratio)						Up to $0.05 per ADS cancelled

•Distribution of cash dividends or other cash distributions (e.g., upon a sale of rights and other entitlements)						Up to $0.05 per ADS held

•Distribution of ADSs pursuant to (i) share dividends or other free share distributions, or (ii) exercise of rights to purchase additional ADSs						Up to $0.05 per ADS held

•Distribution of securities other than ADSs or rights to purchase additional ADSs (e.g., upon a spin-off)						Up to $0.05 per ADS held

•ADS Services						Up to $0.05 per ADS held on the applicable record date(s) established by the depositary

•Registration of ADS transfers (i.e., upon a registration of the transfer of registered ownership of ADSs, upon a transfer of ADSs into DTC and vice versa, or for any other reason)						Up to $0.05 per ADS (or fraction thereof) transferred

•Conversion of ADSs of one series for ADSs of another series (i.e., upon conversion of Partial Entitlement ADSs for Full Entitlement ADSs, or upon conversion of Restricted ADSs (each as defined in the Deposit Agreement) into freely transferable ADSs, and vice versa)						Up to $0.05 per ADS (or fraction thereof) converted

SEC Form 424B5 filed by COMPASS Pathways Plc