On April 28, 2025 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 preclinical efficacy of SLS009 in TP53 mutated Acute Myeloid Leukemia (AML) cells are being presented in a poster session at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) taking place from April 25th – 30th at McCormick Place Convention Center, Chicago, IL (Press release, Sellas Life Sciences, APR 28, 2025, View Source [SID1234652247]).

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!

Patients with TP53–mutated AML continue to face extremely poor outcomes, even with intensive chemotherapy or the addition of stem cell transplantation. Preclinical data suggest that SLS009, a highly selective CDK9 inhibitor, can induce apoptosis downstream of p53 by targeting critical proteins such as MCL-1 and survivin, regardless of p53 status. Immunoblot analysis reveals near-complete removal of these proteins in treated cells within 8 hours of exposure to SLS009. Furthermore, the treatment reduced TP53-mutated leukemia cell populations by up to 97% in combination with azacitidine–venetoclax, and by up to 80% as monotherapy.

"These findings are an exciting step forward in addressing one of the most challenging subsets of AML," said Angelos Stergiou, MD, ScD h.c., President and Chief Executive Officer of SELLAS. "The ability of SLS009 to overcome TP-53 driven resistance in preclinical models, combined with the positive data we have seen in our ongoing Phase 2 AML program, including a response in a patient with a TP53 mutation, gives us hope that we may one day offer an effective therapeutic option to patients with AML who have long been underserved."

SLS009 is currently in Phase 2 clinical trials in patients with relapsed or refractory (r/r) AML following venetoclax-based regimens, including patients with TP53-mutated leukemia. Recently announced data revealed that r/r AML patients receiving 30 mg of SLS009 BIW achieved a mOS of 8.8 months for all patients, while the mOS in AML myelodysplasia-related-changes (MRC) patients reached 8.9 months – far surpassing the historical benchmark of 2.5 months. Among patients with mutation ASXL1, 4/6 (67%) responded; among those with RUNX1 3/5 (60%) responded, and among those with TP53 1/3 (33%) responded. In addition, there were 3 patients with adverse karyotypes, and 1 responded.

"Over the past decade we’ve seen significant progress in the treatment of AML, particularly with the introduction of the venetoclax/azacitidine regimen, the use of targeted agents, and safer application of haploidentical stem cell transplants," said Dr Phillip Amrein, MD, Clinical Investigator, Massachusetts General Hospital, Assistant Professor of Medicine Harvard Medical School, the senior author of the study. "Yet, leukemias characterized by TP53 remain a major area of unmet need, with poor outcomes even with bone marrow transplantation. The preclinical findings suggest that CDK9 inhibition might have the potential to overcome this resistance and restore sensitivity to existing therapies, offering a promising new path forward for high-risk patient populations."

Poster presentation details:

Title: CDK9 inhibition enhances apoptosis of TP53 mutated AML when combined with standard chemotherapy

Session Date and Time: Monday, April 28, 20025, 9:00 AM to 12:00 noon

Session Title: CDK9 inhibition enhances apoptosis of TP53 mutated AML when combined with standard chemotherapy

Location: Poster Section 17

Poster Board #: 1626

The poster will be available on SELLAS websites following the session.

SLS009 is currently being investigated in a Phase 2 open-label, single-arm, multi-center study designed to evaluate the safety, tolerability, and efficacy of SLS009 in combination with venetoclax and azacitidine, including AML patients with ASXL1 mutations. Initial clinical safety and efficacy data are available. In addition, the study aims to identify biomarkers for the target patient population and enrichment for further trials. For more information on the study, visit clinicaltrial.gov identifier NCT04588922.