SELLAS Life Sciences Group, Inc. announced topline data from the Phase 2a study of SLS009 and provides an update on Phase 3 REGAL Study of GPS in AML. The REGAL Steering Committee met on March 22, 2024, to discuss the study and believes the high number of patients who completed participation in the study signals that the interim analysis requiring 60 events may be imminent. The first patient who achieved a complete response continues on the study and remains leukemia-free 9 months post-enrollment.

Summary of Topline Data from Phase 2a data of SLS009 in AML Patients Characteristics: As of March 15, 2024 data cutoff, 21 patients were treated; All patients were diagnosed with AML refractory to or relapsed after venetoclax containing regimens; 20 out of 21 (95%) enrolled patients had adverse/high-risk cytogenetics and 1 patient (5%) had intermediate cytogenetics; Median age was 70 and 19/21 (90.5%) of patients were older than 60 Safety: SLS009 in combination with aza/ven has been well-tolerated at all tested dose levels; No dose-limiting toxicities (DLT) at any of the studied dose levels and no treatment-related high-grade (G3) toxicities were observed; Hematologic toxicities profile was consistent with aza/ven standalone treatment. A total of 21 patients were enrolled in the study as of March 15, 2024: 10 in the 45 mg safety cohort, 11 in the 60 mg cohort (2 x 30 mg twice a week or 60 mg once a week); 10% response rate in the 45 mg QW safety cohort (dose level below the recommended Phase 2 dose, RP2D); 20% response rate in the 60 mg QW cohort; 50% response rate in the 60 u, 2 x 30 mg BIW cohort; Observed strong anti-leukemic activity, defined as 50% or more bone marrow blast reduction in 67% of patients across all dose levels; Median survival rate has not been reached in any of the dose levels; The first patient enrolled in the study who achieved a complete response (CR) continues on the study and remains cancer-free 9 months after enrollment. Biomarkers: During the trial the Company identified potential biomarkers currently undergoing testing as predictive markers in the most recent portion of the study.

Patients with the identified biomarkers exhibited significantly higher response rates: 100% response rate at the optimal dose level (30 mg BIW); 57% response rate across all dose levels; Furthermore, the Company has clarified the proposed biological basis and mechanism of action for SLS009 activity in patients with these biomarkers. The relevant biomarkers are present in multiple hematologic and solid cancer indications, with a substantial proportion of patients exhibiting them in additional indications, ranging up to 50% of patients in some indications. The Phase 2a clinical trial of SLS009 is an open-label, single-arm, multi-center study designed to evaluate the safety profile at all Dose levels; and the safety profile at all Dosing levels.

The Phase 2a clinical study of SLS009 is an Open-label, single-center study designed to evaluate The safety profile at all Dose level of safety profile at All Dose levels.