SELLAS Life Sciences Presents Poster at 2022 SOHO Meeting Highlighting Bioequivalence Data for GFH009 Formulations

• GFH009 Formulation is Near Physiological pH, While Still Achieving Desired Effect –
• GFH009 at pH 6.0 Decreased Potential for Infusion Reaction and Made Dosing Better Tolerated After Multiple Doses or Long-time Infusion –

NEW YORK, Sept. 29, 2022 (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, announced today data from a bioequivalence study for GFH009, its potent, highly selective, clinical-stage small molecule that inhibits cyclin-dependent kinase 9 (CDK9). In the ongoing Phase 1 clinical trial of GFH009 monotherapy in patients with relapsed/refractory hematologic conditions, including acute myeloid leukemia and lymphoma, GFH009 is administered intravenously as a solution. The bioequivalence study was performed to evaluate the effect of different formulations on GFH009’s preclinical pharmacokinetic (PK) profile. Dr. Dragan Cicic, MD, Senior Vice President, Clinical Development, of SELLAS, presented the findings at this year’s Meeting of the Society of Hematologic Oncology (SOHO) in a poster titled “Pharmacokinetics and Bioequivalence of Two Formulations of GFH009 Maleate Injection in Sprague Dawley Rats.”

The solution for GFH009 was originally developed with the pH of 4.5 (acidic). Human blood has a physiological pH of around 7.35 to 7.45. The closer a drug is to this physiological state, the less acidic and irritating it is for patients. In a four-week rat study, GFH009 was tested at 2.0 mg/kg, 4.0 mg/kg and 8.0 mg/kg. At 4.0 mg/kg, drug exposure approached efficacy, which formed the rationale for the dose selection for the presented PK study. Rats were randomly assigned to group one (pH 4.5) or group two (pH 6.0) and matched by sex and body weight. Each rat received a single dose of GFH009 (4.0 mg/kg) at pH 4.5 or pH 6.0 intravenously in the tail vein at a volume of 5.0 mL/kg. The PK profiles of both GFH009 formulations (pH 4.5 and pH 6.0) were found to be comparable, supporting the application of the pH 6.0 formulation in the ongoing Phase 1 clinical trial.

“At pH 6.0, GFH009 is closer to the physiological pH – thus, it is less acidic – and the drug’s behavior remains comparable to that at pH 4.5,” said Dr. Cicic. “As a result, this study allowed us to explore a range of dosing strategies for patients, which helped with dose preparation and administration. The improved formulation also decreased the potential for the infusion reaction and made dosing more well-tolerated after multiple doses or long-time infusion.”

About SELLAS Life Sciences Group, Inc.
SELLAS Life Sciences Group, Inc. (NASDAQ: SLS) 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, galinpepimut-S (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 potential as a monotherapy or in combination with other therapies to address a broad spectrum of hematologic malignancies and solid tumor indications. The Company is also developing GFH009, a small molecule, highly selective CDK9 inhibitor, which is licensed from GenFleet Therapeutics (Shanghai), Inc., for all therapeutic and diagnostic uses in the world outside of Greater China.

For more information on SELLAS, please visit www.sellaslifesciences.com.

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 preclinical data for GFH009, plans for further development of GFH009, and the potential for GFH009 as a drug development candidate. 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 associated with the COVID-19 pandemic and its impact on the Company’s clinical plans and business strategy, risks and uncertainties associated 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 31, 2022 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
Allison Soss
KCSA Strategic Communications
Email: SELLAS@kcsa.com
Phone: 212.896.1267

Media Contacts
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KCSA Strategic Communications
Email: SELLAS@kcsa.com
Phone: 212.896.1276