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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of report (Date of earliest event reported): January 7, 2026

SELLAS Life Sciences Group, Inc.

(Exact name of registrant as specified in its charter)

Delaware	001-33958	20-8099512
(State or other jurisdiction of incorporation or organization)	(Commission File Number)	(I.R.S. Employer Identification No.)

	7 Times Square, Suite 2503 New York, NY 10036
	(Address of Principal Executive Offices) (Zip Code)

Registrant’s telephone number, including area code: (646) 200-5278

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligations of the registrant under any of the following provisions:

¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading symbol(s)	Name of each exchange on which registered
Common Stock, $0.0001 par value per share	SLS	The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 2.02.

Results of Operations and Financial Condition.

As of December 31, 2025, SELLAS Life Sciences Group, Inc. (the “Company”) estimates that its unaudited cash and cash equivalents position was $71.8 million. This amount is unaudited and preliminary and is subject to the completion of financial closing procedures, including management’s reviews. As a result, this amount may differ materially from the amount that will be reflected in the Company’s financial statements as of and for the year ended December 31, 2025.

Item 8.01

Other Events

Subsequent to December 31, 2025, the Company received approximately $26.5 million in proceeds from the exercise of common stock warrants.

As of January 7, 2026, the Company had 170,282,026 shares of common stock outstanding.

Item 9.01.

Financial Statements and Exhibits.

(d) Exhibits

Exhibit Number		Description
104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

		SELLAS Life Sciences Group, Inc.

Date:	January 8, 2026	By:	/s/ John T. Burns
			Name:	John T. Burns
			Title:	Senior Vice President, Chief Financial Officer