Current Report · Items 5.07 · 8-K

SELLAS Life Sciences Group, Inc.

SLSNASDAQEQUITYCurrent

Submission of Matters to a Vote of Security Holders

Filed Jun 18, 2026Accepted Jun 18, 2026, 4:30 PM EDTCIK 1390478Accession 0001104659-26-075775

Company context

Life Sciences Group, Inc. SELLAS is a late-stage clinical biopharmaceutical company focused on the development of novel therapeutics for a broad range of cancer indications. SELLAS’ lead product candidate, GPS, is licensed from Memorial Sloan Kettering Cancer Center and targets the WT1 protein, which is present in an array of tumor types. GPS has the potential as a monotherapy and combination with other therapies to address a broad spectrum of hematologic malignancies and solid tumor indications. The Company is also developing SLS009 (tambiciclib) - potentially the first and best-in-class differentiated small molecule CDK9 inhibitor with reduced toxicity and increased potency compared to other CDK9 inhibitors. Data suggests that SLS009 demonstrated a high response rate in AML patients with unfavorable prognostic factors including ASXL1 mutation, commonly associated with poor prognosis in various myeloid diseases. For more information on SELLAS, please visit www.sellaslifesciences.com

Current securities

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Recent company filings

Disclosure sections

Items 5.07

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Item 5.07Item 5.07 - Submission of Matters to Vote

Item 5.07 Submission of Matters to a Vote of Security Holders. Annual Meeting of Stockholders On June 16, 2026, SELLAS Life Sciences Group, Inc. (the “Company”) held its Annual Meeting of Stockholders (“Annual Meeting”). There were 115,511,771 shares of common stock, or approximately 62.59% of all outstanding shares, present in person or represented by proxy. At the Annual Meeting, the stockholders voted on the following five proposals and cast their votes as described below. Proposal 1 The Company’s stockholders re-elected each of the following nominees as a Class I director to the Board of the Company to hold office until the 2029 Annual Meeting of Stockholders and until their respective successors have been duly elected and qualified. NAME FOR WITHHELD BROKER NON-VOTES ──────────────────────────────────────────────────────────────────────────── Robert Van Nostrand 66,490,143 4,544,035 44,477,593 Jane Wasman 65,928,448 5,105,730 44,477,593 Proposal 2 The Company’s stockholders ratified the appointment of Baker Tilly US, LLP (as the successor to Moss Adams LLP) as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2026. FOR AGAINST ABSTAIN BROKER NON-VOTES ─────────────────────────────────────────────────────────────────── 112,103,701 2,126,460 1,281,610 - Proposal 3 The Company’s stockholders approved an amendment to the Company’s 2023 Amended and Restated Equity Incentive Plan (the “2023 Equity Plan”) to increase the number of shares of common stock available for sale under the 2023 Equity Plan by 20,000,000. FOR AGAINST ABSTAIN BROKER NON-VOTES ───────────────────────────────────────────────────────────────── 42,906,271 27,310,386 817,521 44,477,593 Proposal 4 The Company’s stockholders approved the non-binding, advisory resolution on the executive compensation of the Company’s named executive officers. FOR AGAINST ABSTAIN BROKER NON-VOTES ─────────────────────────────────────────────────────────────────── 52,930,792 15,906,732 2,196,654 44,477,593 Proposal 5 The Company’s stockholders approved an adjournment of the Annual Meeting, if necessary, to solicit additional proxies in favor of proposals 1, 2, 3 and 4. FOR AGAINST ABSTAIN BROKER NON-VOTES ─────────────────────────────────────────────────────────────────── 90,571,992 22,200,030 2,739,749 - No other matters were submitted to or voted on by the Company’s stockholders at the Annual Meeting.