SLS009 in combination with AZA/VEN achieved a 46% overall response rate across all cohorts, a 58% overall response rate in patients with one prior line of therapy, and encouraging survival outcomes in heavily-pretreated AML-MR following prior VEN-based treatment
Median overall survival (mOS) of 8.9 months in the least pretreated patient cohort; across all cohorts, mOS was not yet reached in patients with one prior line of therapy vs historical benchmark of approximately 2.5 months
SLS009 30 mg IV twice weekly added to AZA/VEN was safe and feasible, with no dose-limiting toxicities (DLTs) observed
Study expansion to evaluate SLS009 plus AZA/VEN in newly diagnosed AML with high-risk features is planned for Q1 2026
SELLAS Life Sciences Group, Inc. (NASDAQ: SLS) , 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
