On November 4, 2026 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, reported that data from its completed Phase 2 study of SLS009 (tambiciclib) for the treatment of relapsed or refractory acute myeloid leukemia (r/r AML) will be presented at the 68th American Society of Hematology (ASH) (Free ASH Whitepaper) Annual Meeting and Exposition, being held December 12–15, 2026 in New Orleans. This Phase 2 trial evaluated SLS009, a highly selective CDK9 inhibitor, in combination with azacitidine (AZA) and venetoclax (VEN) for the treatment of patients with r/r AML after prior VEN-based treatment.

Schedule your 30 min Free 1stOncology Demo!
Discover why more than 1,500 members use 1stOncology™ to excel in:

Early/Late Stage Pipeline Development - Target Scouting - Clinical Biomarkers - Indication Selection & Expansion - BD&L Contacts - Conference Reports - Combinatorial Drug Settings - Companion Diagnostics - Drug Repositioning - First-in-class Analysis - Competitive Analysis - Deals & Licensing

                  Schedule Your 30 min Free Demo!

"There is an urgent need in AML to address the growing number of patients who have either relapsed or become refractory to treatment with venetoclax," said Angelos Stergiou, MD, ScD h.c., President and Chief Executive Officer of SELLAS Life Sciences. "Our participation at this year’s ASH (Free ASH Whitepaper) Annual Meeting reflects our continued focus on addressing this population by evaluating SLS009 in patients who have failed venetoclax therapy. We look forward to sharing these Phase 2 results with the hematology community and the continued advancement of our SLS009 program, which is currently being studied in newly diagnosed AML patients."

"Furthermore, we are excited and hopeful with our galinpepimut-S (GPS) clinical program, as we anticipate reporting the topline primary endpoint data in the Phase 3 REGAL study soon. Overall, we expect to have a strong presence at this year’s ASH (Free ASH Whitepaper) meeting as we continue our mission to develop medicines with the potential to advance the standard of care for patients with AML," added Dr. Stergiou.

Key outcomes of the SLS009 dose-ranging study in combination with azacitidine and venetoclax:

Population: 62 heavily pretreated patients whose AML relapsed or did not respond after venetoclax-based therapy. Median age was 70, and median number of prior lines was 2, with up to 8. High-risk mutations were common: ASXL1 41%, RUNX1 33%, TP53 29%.

Successfully Overcomes Venetoclax Resistance: SLS009 targets two primary drivers of venetoclax resistance: TP53 mutations and MCL-1 reliance. The combination demonstrates robust anti-leukemic activity in difficult-to-treat genetic and phenotypic populations following venetoclax failure.

Efficacy, All Doses (n=59): ORR 34% (12 CR/CRi, 8 MLFS) — 38% in AML-MR, 44% in monocytic AML and 36% in TP53-mutated AML.

Efficacy at the Selected Dose (30 mg twice weekly): Patients with monocytic AML achieved a 54% ORR with a median overall survival (mOS) of 5.8 months and patients with TP53-mutated AML achieved a 57% ORR and a mOS of 8.8 months, comparing favorably to historical outcomes in these adverse-risk settings of ~2.5 months.

Safety: Adding SLS009 to Aza/Ven was well tolerated with limited additive toxicities or treatment-related deaths. Non-hematologic treatment-related adverse events were predominantly mild (Grade 1/2) nausea and diarrhea.

"AML patients who progress after venetoclax-based therapy have very limited treatment options. Venetoclax resistance is largely driven by MCL-1 dependence," said Joshua Zeidner, MD, Principal Investigator and Professor of Medicine at University of North Carolina, Lineberger Comprehensive Cancer Center. "Furthermore, AML patients with TP53 mutations have poor outcomes with venetoclax-based therapy. The response rates of 57% in relapsed TP53-mutated and 54% in relapsed monocytic AML are encouraging and suggest that SLS009 acts on the biology that drives resistance. Continued investigation of SLS009 in combination with azacitidine and venetoclax in the frontline setting is now a natural development course for this therapy."

Enrollment and dosing continue in the ongoing 80-patient Phase 2 trial in newly diagnosed AML patients, including those who become refractory early to AZA/VEN treatment identified through extensive transcriptomics, genomics, and proteomics models. Early topline data are expected in Q4 2026. Additional information about the trial can be found at clinicaltrials.gov (NCT04588922).

"These results show that adding SLS009 can restore responses in this setting, including in TP53-mutated disease, without adding meaningful toxicity, which matters most for patients who have struggled to remain on venetoclax-based treatments due to poor tolerability," said Dragan Cicic, MD, Senior Vice President and Chief Development Officer of SELLAS Life Sciences. "We have now taken SLS009 into the frontline setting, guided by precision medicine. Our extensive biological and multi-omics analyses, including genomics and single-cell profiling, help us identify which patients could benefit most and when to add SLS009 to azacitidine and venetoclax. We expect first topline data from the Phase 2 frontline trial in Q4 2026, and we believe moving SLS009 into earlier lines of treatment will give it the best chance to change the course of this disease."

SLS009 (tambiciclib) Abstract Presentation Details:

Title: Tambiciclib (SLS009), a highly selective CDK9 inhibitor, in combination with azacitidine and venetoclax in relapsed/refractory AML after prior venetoclax: Results from a Phase 2 study
Session Date and Presentation Time: Monday, December 14, 2026, 6:00 – 8:00 PM CST
Session: 616. Acute Myeloid Leukemias: Investigational Drug and Cellular Therapies (Poster III)
Location: Ernest N. Morial Convention Center (MCCNO) – Hall F
Lead Author: Joshua F. Zeidner, MD, Professor of Medicine, Chief of Leukemia Research, The University of North Carolina School of Medicine
Abstract Number: 5155

(Press release, Sellas Life Sciences, NOV 4, 2026, View Source [SID1234674214])