NEW YORK, NY — 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 clinical data from its ongoing Phase 2 study of SLS009, a highly selective CDK9 inhibitor, in combination with azacitidine (AZA) and venetoclax (VEN) for the treatment of patients with relapsed or refractory (R/R) acute myeloid leukemia (AML) with myelodysplastic syndrome-related changes (AML-MR) after prior VEN-based treatment were presented today at the 67th American Society of Hematology (ASH) Annual Meeting and Exposition, being held December 6 – 9, 2025, in Orlando, Florida.
In this Phase 2 expansion study, R/R AML-MR patients (N = 35 evaluable) were studied in three separate cohorts (cohorts 3-5) who were previously treated with VEN-based regimens and either relapsed and/or were refractory to VEN and were then treated with SLS009 plus AZA/VEN. The median age of participating patients was 69 years, and 98% of patients had ELN adverse-risk AML, with the most frequent mutations being ASXL1, RUNX1, TP53, and SRSF2.
SLS009 in combination with AZA/VEN demonstrated clinically meaningful activity in patients with R/R AML-MR, and among the 35 evaluable patients, the overall response rate (CR+CRi+MLFS) was 46%, including 29% achieving CR/CRi. Patients harboring ASXL1 or TP53 mutations achieved response rates of 48% (19% CR/CRi) and 57% (29% CR/CRi), respectively. The median overall survival (mOS) was exceedingly higher than the expected 2.6 months in this R/R AML patient population, and in the least pretreated cohort, mOS reached 8.9 months. Across all cohorts, patients with one prior line of therapy experienced the greatest benefit, with a 58% response rate and mOS not yet reached. No dose-limiting toxicities (DLTs) or treatment-related deaths were observed, and the combination was well tolerated.
“These results further reinforce the therapeutic potential of SLS009 to overcome resistance to venetoclax-based regimens by suppressing the expression of MCL-1, a key mechanism of resistance to BCL-2 inhibition in AML,” said Dr. Dragan Cicic, Senior Vice President and Chief Development Officer of SELLAS. “The combination of SLS009 with azacitidine and venetoclax demonstrates encouraging activity in a heavily pretreated population with adverse-risk AML-MR, including those harboring ASXL1 and TP53 mutations. We are particularly encouraged by the strong responses in patients with limited prior therapy and look forward to expanding this combination regimen into newly diagnosed AML with high-risk features.”
Presentation Details:
Title: Phase 2 Study of SLS009 in Combination with Azacitidine and Venetoclax for Relapsed/Refractory AML with MDS-Related Changes (AML-MR) After Prior Venetoclax Treatment
Session Date and Presentation Time: Sunday, December 7, 2025, 6:00 – 8:00 PM EST
Session Title: 616. Acute Myeloid Leukemias: Investigational Drug and Cellular Therapies: Poster II
Location: Orange County Convention Center (OCCC) – West Halls B3-B4
Lead Author: Joshua F. Zeidner, MD, University of North Carolina, Lineberger Comprehensive Cancer Center, Chapel Hill, NC
Publication Number: 3423
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 www.sellaslifesciences.com.
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