[8-K] SELLAS Life Sciences Group, Inc. Reports Material Event

Rhea-AI Filing Summary

SELLAS Life Sciences Group, Inc. reported a material event on Form 8-K disclosing the company has entered into a Letter Agreement with Times Square Tower Associates LLC. The filing lists Item 1.01 (Entry into a Material Definitive Agreement) and Item 9.01 (Financial Statements and Exhibits) and identifies Exhibit 10.1 as the Letter Agreement. The document record includes an embedded Inline XBRL cover page and is signed by the company’s Senior Vice President, Chief Financial Officer with a reference date in early October 2025. The filing text provided does not specify the Letter Agreement’s commercial terms, purpose, or financial impact.

Positive

• Company disclosed execution of a material agreement, meeting SEC Form 8-K requirements
• Exhibit 10.1 (Letter Agreement) is identified, enabling investors to locate the full document when filed

Negative

• None.

Insights

Corporate Counsel / SEC Filings Specialist

Material agreement disclosed; key terms not provided.

The Form 8-K confirms execution of a material definitive document — the Letter Agreement with Times Square Tower Associates LLC — and identifies it as Exhibit 10.1. This satisfies disclosure obligations under Item 1.01 and Item 9.01.

Because the filing excerpt does not include the agreement text or financial terms, investors cannot assess obligations, payment amounts, or timelines from the provided content. The full exhibit will be needed to evaluate legal commitments.

Investor Relations / Transaction Analyst

Event is potentially material but impact is unknown without terms.

The company flagged the agreement as material on Form 8-K, which implies potential investor significance. However, the excerpt lacks revenue, expense, lease, or other quantitative terms, so the filing itself does not allow measuring near-term financial impact.

Review of Exhibit 10.1 is required to determine whether the agreement affects cash flows, liabilities, or operations.

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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): October 1, 2025

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 1.01 Entry into a Material Definitive Agreement.

On October 1, 2025, SELLAS Life Sciences Group, Inc. (the “Company”), as subtenant, entered into a Letter Agreement with Times Square Tower Associates LLC (the “Sublandlord”) relating to a certain sublease (as amended) of certain premises located at Times Square Tower, 7 Times Square, New York, New York (the “Sublease”). The Letter Agreement provides for the extension of the expiration date of the Sublease from September 30, 2026 to September 30, 2027. The annual rent remains unchanged.

The foregoing description of the Letter Agreement is qualified in its entirety by reference to the Letter Agreement, which is filed as Exhibit 10.1 hereto and incorporated herein by reference.

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Item 9.01. Financial Statements and Exhibits.

(d)       Exhibits

Exhibit Number		Description
10.1		Letter Agreement by and between SELLAS Life Sciences Group, Inc. and Times Square Tower Associates LLC
104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

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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:	October 3, 2025	By:	/s/ John T. Burns
			Name:	John T. Burns
			Title:	Senior Vice President, Chief Financial Officer

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FAQ

What did SELLAS (SLS) disclose in the 8-K?

The 8-K discloses entry into a Letter Agreement with Times Square Tower Associates LLC and lists it as Exhibit 10.1 under Item 1.01 and Item 9.01.

Does the filing state the financial terms of the Letter Agreement?

No. The provided excerpt does not include any financial terms, payment amounts, or obligations; only the existence of the Letter Agreement is disclosed.

Where can investors find the full agreement text?

The filing identifies the Letter Agreement as Exhibit 10.1; investors should review the full Form 8-K on the SEC EDGAR system to access that exhibit.

When was the 8-K signed by SELLAS’ CFO?

The signature block in the excerpt references a date in early October 2025 and is signed by the company’s Senior Vice President, Chief Financial Officer.

Does the excerpt indicate the agreement’s purpose (e.g., lease, service, settlement)?

No. The excerpt names the counterparty but does not describe the nature or purpose of the Letter Agreement.