SELLAS Outlines 2025 Objectives: Phase 3 REGAL Interim Analysis In January, Phase 2 SLS009 Topline Data And FDA Review Expected 1H 2025, Tambiciclib Named As INN For SLS009, Non-Dilutive Grant Funding Application Submitted For AML Expansion, And Pediatric Program Development Underway

Expected Milestones in 2025:

Galinpepimut-S (GPS): Wilms Tumor-1 (WT1) targeting immunotherapeutic

• Phase 3 REGAL study in AML:
  
   

The interim analysis from the ongoing REGAL global Phase 3 registrational clinical trial of GPS in patients with AML who have achieved complete remission following second-line salvage therapy (CR2 patients) is expected in January 2025. Based on the results of this analysis, the IDMC will provide recommendations to either stop the trial early for efficacy, stop for futility, or continue the study without modification. If the recommendation is to continue without modification, the next and final analysis will take place upon reaching a total of 80 events, as predefined in the study protocol.

SLS009: highly selective CDK9 inhibitor

• Phase 2 clinical trial in AML: Full topline data from expansion cohorts which include AML-MRC patients with ASXL1 mutation (cohort 4) and mutations and cytogenic changes other than ASXL1 (cohort 5) are expected in 1H 2025.
• FDA feedback on regulatory path for r/r AML study expected in 1H 2025.

2024 Key Achievements:

Galinpepimut-S (GPS): Wilms Tumor-1 (WT1) targeting immunotherapeutic

• Phase 3 REGAL study of GPS in AML reached pre-specified threshold of 60 events (deaths) initiating the interim analysis being conducted by the Independent Data Monitoring Committee (IDMC).
  
   

SLS009: highly selective CDK9 inhibitor

• The World Health Organization (WHO) has approved "tambiciclib" as the recommended International Nonproprietary Name (INN) for SLS009
• Reported positive data from the ongoing Phase 2 trial of SLS009 in r/r AML in Q4 2024. The median overall survival (mOS) has not been reached but exceeds 7.7 months at the latest follow-up, marking a significant milestone for patients in this setting, where the expected mOS is historically around 2.5 months. In expansion cohorts in patients with AML-myelodysplasia-related changes (AML-MRC) with ASXL1 mutation and mutations and cytogenic changes other than ASXL1, the ORR was 56% in 9 evaluable for efficacy patients, exceeding pre-specified target response rate of 33%.
• Presented data from Phase 2a trial of SLS009 in r/r AML at the 66th American Society of Hematology (ASH) Annual Meeting & Exposition 2024. Treatment with SLS009 in combination with azacitidine and venetoclax was well tolerated and led to a 50% response rate in the selected optimal dose level of 30 mg twice a week. Clinical activity was even higher in patients with AML-MRC and in particular, those with ASXL1 mutations, suggesting that this subset of patients may exhibit preferential sensitivity to SLS009. In the safety dose of 45mg once a week, SLS009 showed a mOS of 5.5 months.
• Completed enrollment in Phase 2a Trial of SLS009 in r/r AML: 30 patients relapsed after or refractory to venetoclax-based regiments were enrolled ahead of schedule in 5 centers across the US. Except for one, all patients in the Phase 2a trial had adverse risk AML (97%) and were treated with continued venetoclax–azacytidine combination therapy after having failed it or similar venetoclax-based combinations, often more than once.
• Opened enrollment in additional Phase 2 cohorts in venetoclax combinations in r/r AML. Development of SLS009 continues with the opening of two new cohorts - AML MRC with ASXL1 mutations and AML with myelodysplasia related changes other than ASXL1 mutations. These new cohorts are also open for enrollment of certain pediatric patients.
• Announced positive preclinical data indicating ASXL1 mutations as predictors of response to SLS009 in solid cancers.
• Published in Oncotarget, revealing the underlying mechanisms of action behind the anti-proliferative effects of SLS009 in various hematologic malignancies.
• Continued National Cancer Institute (NCI) Pediatric Preclinical in Vivo Testing (PIVOT) Program in pediatric tumor.

Regulatory:

• Received multiple regulatory designations: for GPS: FDA Rare Pediatric Disease Designation (RPDD) for pediatric AML, for SLS009: RPDD for pediatric AML, pediatric acute lymphoblastic leukemia (ALL), FDA Fast Track Designation for AML, and EMA orphan drug designation (ODD) for AML and peripheral T-cell lymphoma (PTCL).