Sequencing Results Utilizing a Proteus Prototype System Exceeds Platinum® Pro

Quantum-Si Incorporated (NASDAQ:QSI) ("Quantum-Si," "QSI" or the "Company"), a proteomics technology company redefining protein analysis through single-molecule protein sequencing, today announced that the Company has completed the sequencing of multiple samples provided by an existing Platinum Pro customer on a Proteus prototype system.

The testing included sequencing the samples on both Platinum Pro and a Proteus prototype system. For Platinum Pro, the Company used the commercially available Version 3 Library Preparation Kit and Version 4 Sequencing Kit. For the Proteus prototype, the Company used the Version 3 Library Preparation Kit and a developmental sequencing kit that contains the latest amino acid recognizer set.

The sequencing results were consistent with the information that the Company shared at the November 2025 Investor and Analyst Day demonstrating that Proteus was far exceeding Platinum Pro performance across all relevant metrics. Specifically, the Proteus prototype and developmental sequencing kit demonstrated significantly improved amino acid coverage, longer read lengths, more peptides identified and greater sequencing output even when normalized for the difference in the number of nanowells on a Platinum Pro chip versus the Proteus KinetIQ™ array.

"We are very excited to have successfully completed the sequencing of our first customer samples on the Proteus prototype system," said Jeff Hawkins, President and Chief Executive Officer of Quantum-Si. "Being able to demonstrate that the Proteus prototype system exceeds Platinum performance across all metrics on real world samples is an important milestone in the development of this new platform. We expect sequencing performance to continue to increase from here as we work to further optimize the Proteus system into our final commercial offering."

Hawkins continued, "This is just one of many customers who have indicated interest in providing samples for sequencing on the Proteus prototype. We are working closely with our manufacturing partners to increase the rate of delivery of integrated Proteus systems to meet both internal R&D demand and provide additional capacity to be able to offer customer sample testing to the market through a formal pre-launch sample evaluation program. We look forward to providing more updates on this program on our next earnings call."

About Quantum-Si Incorporated

Quantum-Si is transforming proteomics with a benchtop platform that brings single-molecule protein analysis to every lab, everywhere. The Company's platform enables real-time kinetic-based detection and allows researchers to move beyond traditional, multistep workflows and directly access dynamic, functional protein insights with unparalleled resolution. By making protein analysis simpler, faster, and more informative, Quantum-Si is accelerating proteomic discoveries to improve the way we live. Learn more at quantum-si.com or follow us on LinkedIn or X.

Forward Looking Statements

This press release includes "forward-looking statements" within the meaning of the "safe harbor" provisions of the United States Private Securities Litigation Reform Act of 1995. The actual results of the Company may differ from its expectations, estimates, and projections and, consequently, you should not rely on these forward-looking statements as predictions of future events. Words such as "expect," "estimate," "project," "budget," "forecast," "anticipate," "intend," "plan," "may," "will," "could," "should," "believes," "predicts," "potential," "continue," and similar expressions (or the negative versions of such words or expressions) are intended to identify such forward-looking statements. These forward-looking statements include, without limitation, the Company's expectations with respect to future performance and development and commercialization of products, services and applications, its anticipated cash runway, the anticipated timing of product launches and product capabilities (including Proteus), investor confidence in Quantum-Si and our strategic roadmap, and any financial guidance. These forward-looking statements involve significant risks and uncertainties that could cause the actual results to differ materially from those discussed in the forward-looking statements. Many of these factors are outside the Company's control and are difficult to predict. Factors that may cause such differences include, but are not limited to: the inability to maintain the listing of the Company's Class A common stock on The Nasdaq Stock Market; the ability of the Company to grow and manage growth and retain its key employees; the Company's ongoing leadership transitions and succession planning; changes in applicable laws or regulations; the ability of the Company to raise financing in the future; the success, cost and timing of the Company's product development and commercialization activities, including the use and benefit of artificial intelligence in these and other activities; the commercialization and adoption of the Company's existing products and the success of any product the Company may offer in the future, including Proteus; the potential attributes and benefits of the Company's commercialized Platinum protein sequencing instruments and kits and the Company's other products (including Proteus) once commercialized; the Company's ability to obtain and maintain regulatory approval for its products, and any related restrictions and limitations of any approved product; the Company's ability to identify, in-license or acquire additional technology; the Company's ability to maintain its existing lease, license, manufacture and supply agreements; the Company's ability to compete with other companies currently marketing or engaged in the development or commercialization of products and services that serve customers engaged in proteomic analysis, many of which have greater financial and marketing resources than the Company; the size and growth potential of the markets for the Company's products and services, and its ability to serve those markets once commercialized, either alone or in partnership with others; the Company's estimates regarding future expenses, future revenue, capital requirements and needs for additional financing; the Company's financial performance; the Company's defense and initiation of litigation matters; and other risks and uncertainties described under "Risk Factors" in the Company's most recent Annual Report on Form 10-K and Quarterly Reports on Form 10-Q and in the Company's other filings with the SEC. The Company cautions that the foregoing list of factors is not exclusive. The Company cautions readers not to place undue reliance upon any forward-looking statements, which speak only as of the date made. The Company does not undertake or accept any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements to reflect any change in its expectations or any change in events, conditions, or circumstances on which any such statement is based.

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Investor and Media

Jeff Keyes

Chief Financial Officer

ir@quantum-si.com

Quantum-Si Announces First Customer Samples Tested on the Proteus™ Prototype System