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424B5 1 tm267111-4_424b5.htm 424B5 tm267111-4_424b5 - none - 5.6727182s

Filed Pursuant to Rule 424(b)(5)

Registration No. 333-275300

PROSPECTUS SUPPLEMENT
(To Prospectus dated November 3, 2023)

10,345,000 Shares of Common Stock

We are offering 10,345,000 shares of our common stock in this offering.

Our common stock is listed on the Nasdaq Capital Market (“Nasdaq”) under the symbol “CLDX.” The last reported sale price of our common stock on April 1, 2026 was $31.26 per share.

Investing in our common stock involves a high degree of risk. Before buying shares of our common stock, you should carefully consider the risk factors described in “Risk Factors” beginning on page S-8 of this prospectus supplement and in the risks discussed under similar headings in the documents incorporated by reference into this prospectus supplement, the accompanying prospectus and any free writing prospectus that we have authorized for use in connection with this offering.

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 supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

	PER SHARE			TOTAL
Public offering price		$	29.00		$	300,005,000
Underwriting discounts and commissions(1)		$	1.74		$	18,000,300
Proceeds to us, before expenses		$	27.26		$	282,004,700

(1)

See the section entitled “Underwriting” beginning on page S-12 for a description of the compensation payable to the underwriters.

We have granted to the underwriters an option for a period of 30 days to purchase up to an additional 1,551,750 shares of our common stock from us at the public offering price set forth above, less the underwriting discounts and commissions.

The underwriters expect to deliver the shares of common stock against payment on or about April 6, 2026.

Joint Bookrunning Managers

Leerink Partners

TD Cowen

Guggenheim Securities

Cantor

Co-Lead Managers

LifeSci Capital

H.C. Wainwright & Co.

The date of this prospectus supplement is April 1, 2026.

	PAGE
Prospectus Supplement
ABOUT THIS PROSPECTUS SUPPLEMENT		S-1
FORWARD-LOOKING STATEMENTS		S-3
PROSPECTUS SUPPLEMENT SUMMARY		S-5
THE OFFERING		S-7
RISK FACTORS		S-8
USE OF PROCEEDS		S-10
DILUTION		S-11
UNDERWRITING		S-12
LEGAL MATTERS		S-17
EXPERTS		S-17
WHERE YOU CAN FIND MORE INFORMATION		S-17
INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE		S-18
Prospectus
ABOUT THIS PROSPECTUS		1
PROSPECTUS SUMMARY		2
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS		3
RISK FACTORS		4
USE OF PROCEEDS		5
SELLING SECURITYHOLDERS		6
DESCRIPTIONS OF SECURITIES WE MAY OFFER		7
DESCRIPTION OF COMMON STOCK		8
DESCRIPTION OF PREFERRED STOCK		9
DESCRIPTION OF WARRANTS		12
DESCRIPTION OF DEPOSITARY SHARES		14
DESCRIPTION OF UNITS		15
PLAN OF DISTRIBUTION		16
LEGAL MATTERS		18
EXPERTS		18
WHERE YOU CAN FIND MORE INFORMATION		18
INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE		19

Public offering price per share			$	29.00
Net tangible book value per share as of December 31, 2025	$	7.51
Increase in net tangible book value per share attributable to investors purchasing shares of common stock in this offering		2.66
As adjusted net tangible book value per share after giving effect to this offering				10.17
Dilution in net tangible book value per share to new investors purchasing shares of common stock in this offering			$	18.83

UNDERWRITER	NUMBER OF SHARES
Leerink Partners LLC		3,310,400
TD Securities (USA) LLC		3,103,500
Guggenheim Securities, LLC		1,448,300
Cantor Fitzgerald & Co.		1,448,300
LifeSci Capital LLC		827,600
H.C. Wainwright & Co., LLC		206,900
Total		10,345,000

				Total
	PER SHARE			WITHOUT OPTION			WITH OPTION
Initial public offering price		$	29.00		$	300,005,000		$	345,005,750
Underwriting discounts and commissions		$	1.74		$	18,000,300		$	20,700,345
Proceeds, before expenses, to us		$	27.26		$	282,004,700		$	324,305,405

SEC Form 424B5 filed by Celldex Therapeutics Inc.