SELLAS Life Sciences Group, Inc. announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track Designation to SLS009 (formerly GFH009), its novel and highly selective CDK9 inhibitor, for the treatment of relapsed/refractory (r/r) acute myeloid leukemia (AML). The Fast Track Designation is intended to facilitate the development and review of drugs to treat serious conditions and fill an unmet medical need. A total of nine patients have been enrolled at the 45 mg safety dose level.

Eight patients (89%) remain alive (one patient succumbed to sepsis having previously contracted COVID 19) and six continue treatment. The first enrolled patient achieved a complete response and continues on the study in the seventh month with full blood recovery and the second enrolled patient is in the sixth month of treatment. The follow-up duration for the patients who are alive ranges from two to seven months and median OS has not been reached.

Significant anti-leukemic effects (=50% decrease in bone marrow blasts) were observed during treatment in seven out of eight (87.5%) assessable patients with no significant safety issues to date. No dose limiting toxicities were observed in any of the patients. In the Phase 1 study of SLS009 as monotherapy, a durable CR with no minimal residual disease (MRD) was observed in one patient with AML who had failed prior aza/ven therapy.

The patient continues to be alive 16 months following commencement of treatment per last follow-up. Patients with AML that fail venetoclax-based therapies have limited treatment options and a poor prognosis with a median OS of approximately 2.5 months. The Phase 2a clinical trial of SLS009 is an open label, single arm, multi-center study that is designed to evaluate safety, tolerability, and efficacy at two dose levels, 45 mg and 60 mg, in combination with aza/ven.

In the 60 mg dose cohort, patients are being randomized to one of two groups, 60 mg flat (fixed) dose once per week and 30 mg fixed dose two times per week. Each group will enroll 5 ? 10 patients.

In addition to safety and tolerability of SLS009 in combination with aza/ven, the primary endpoints are composite complete response rate (CRc) and duration of response (DOR). Additional endpoints include event free survival (EFS), OS, and pharmacokinetic (PK) and pharmacodynamic (PD) assessments. Venetoclax combinations with hypomethylating agents are a commonly used regimen in this target population but despite high efficacy (up to approx. 67% complete response rate), approximately one-third to one-half of patients do not respond to venetoclax based regimens, and among those who respond almost all eventually relapse.

The Company expects to report additional data from the fully enrolled 45 mg (safety dose level) cohort and initial data from the 60 mg (recommended Phase 2 dose level) cohort in the first quarter of 2024 and expects the 60 mg cohort to be analyzed in the second quarter of 2024.