On December 9, 2024 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 additional data from the expansion cohorts in the Phase 2 trial of SLS009, a highly selective CDK9 inhibitor, in relapsed/refractory acute myeloid leukemia (r/r AML) (Press release, Sellas Life Sciences, DEC 9, 2024, View Source [SID1234648913]).

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"We are highly encouraged by the emerging data, which continue to show the potential of SLS009 to transform outcomes of these heavily pretreated AML patients," said Angelos Stergiou, MD, ScD h.c., President and Chief Executive Officer of SELLAS. "In the Cohort 3, the optimal dosing regimen of 30 mg BIW, in patients relapsed or refractory to venetoclax-based regimens, the median overall survival has not been reached but exceeds 7.7 months at latest follow-up, marking a significant milestone for patients in this setting, where the expected mOS is historically around 2.5 months. In addition, we are seeing more than 50% ORR to date in our expansion cohorts in patients with AML-myelodysplasia-related changes (AML-MRC) with ASXL1 mutation and mutations and cytogenic changes other than ASXL1, similar to the previously reported ORR in Cohort 3. We set up an aggressive threshold of 33% response rate before the trial started, and to date we achieved 56% in 5/9 evaluable patients. The rapid enrollment in the expansion cohorts further highlight the critical need for new treatments for our target patient population. These results support the potential of SLS009 to become an important new therapeutic option for this underserved patient population."

Key Highlights from the updated topline data:

As of December 4, 2024, data cutoff, 14 patients were enrolled in Cohort 3 and 14 in Cohort 4 and 5, of which 9 were evaluable at the time of analysis.
At latest follow-up, the mOS has not been reached yet but has exceeded 7.7 months in Cohort 3. This is particularly significant as the expected mOS for patients in this setting is typically 2.5 months.
In expansion cohorts 4 and 5, in patients with AML-myelodysplasia-related changes (AML-MRC) with ASXL1 mutation (cohort 4) and mutations and cytogenic changes other than ASXL1 (cohort 5) the ORR was 56% in 9 evaluable for efficacy patients.
SLS009 was well-tolerated with no new safety signals observed to date as the regimen remains safe in additional patients enrolled to date.
The Phase 2 clinical trial of SLS009 is an open-label, single-arm, multi-center study designed to evaluate the safety, tolerability, and efficacy of SLS009 in combination with venetoclax and azacitidine at two dose levels, 45 and 60 mg. In the 60 mg dose cohort patients were randomized into either a 60 mg dose once per week or a 30 mg dose two times per week. The trial was expanded to include two additional cohorts, one with ASXL1 mutated AML patients and one with patients with myelodysplasia-related molecular abnormalities other than ASXL1. In addition to response and survival analyses, 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.