SELLAS Life Sciences to be Added to Russell 3000® and Russell 2000® Indexes

NEW YORK, June 24, 2025 (GLOBE NEWSWIRE) -- SELLAS Life Sciences Group, Inc. (NASDAQ: SLS) (“SELLAS” or the “Company”), a late-stage clinical biopharmaceutical company focused on the development of novel therapies for a broad range of cancer indications, today announced that the Company will be added to the Russell 3000^® and Russell 2000^® Indexes, effective after the U.S. market close on June 27, as part of the 2025 Russell indexes annual reconstitution.

The Russell 3000^® Index tracks the performance of the largest 3,000 publicly traded U.S. companies and serves as a broad benchmark for the U.S. equity market. The Russell 2000^® Index, a subset of the Russell 3000^®, measures the performance of the small-cap stocks and represents approximately 10% of the total market capitalization of the U.S. equity market.

Membership in the indexes lasts for one year and results in automatic inclusion in appropriate growth and value style indexes. The Russell indexes are used by investment managers and institutional investors for index funds and as benchmarks for active investment strategies.

“Being added to the Russell 3000^® and Russell 2000^® Indexes marks an important corporate milestone for SELLAS and reflects the strong progress we continue to make advancing our pipeline and building long-term shareholder value,” said John Burns, Senior Vice President and Chief Financial Officer of SELLAS. “Inclusion in these indexes increases our visibility with institutional investors as we approach the readout of full topline Phase 2 data of SLS009 in acute myeloid leukemia (AML) and the final analysis of our Phase 3 pivotal REGAL trial of GPS in AML.”

For further information on the Russell 3000^® and Russell 2000^® Indexes and the Russell indexes reconstitution, go to the “Russell Reconstitution” section on the .

About SELLAS 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 .

Forward-Looking Statements

This press release contains forward-looking statements. All statements other than statements of historical facts are “forward-looking statements,” including those relating to future events. In some cases, forward-looking statements can be identified by terminology such as “plan,” “expect,” “anticipate,” “may,” “might,” “will,” “should,” “project,” “believe,” “estimate,” “predict,” “potential,” “intend,” or “continue” and other words or terms of similar meaning. These statements include, without limitation, statements related to the GPS clinical development program, including the REGAL study and the timing of future milestones related thereto. These forward-looking statements are based on current plans, objectives, estimates, expectations, and intentions, and inherently involve significant risks and uncertainties. Actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include, without limitation, risks and uncertainties with oncology product development and clinical success thereof, the uncertainty of regulatory approval, and other risks and uncertainties affecting SELLAS and its development programs as set forth under the caption “Risk Factors” in SELLAS’ Annual Report on Form 10-K filed on March 20, 2025 and in its other SEC filings. Other risks and uncertainties of which SELLAS is not currently aware may also affect SELLAS’ forward-looking statements and may cause actual results and the timing of events to differ materially from those anticipated. The forward-looking statements herein are made only as of the date hereof. SELLAS undertakes no obligation to update or supplement any forward-looking statements to reflect actual results, new information, future events, changes in its expectations, or other circumstances that exist after the date as of which the forward-looking statements were made.

Investor Contact

John Fraunces

Managing Director

LifeSci Advisors, LLC