On March 26, 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 topline data from the Phase 2a study of SLS009 and provides an update on Phase 3 REGAL Study of GPS in AML (Press release, Sellas Life Sciences, MAR 26, 2024, View Source [SID1234641452]). The Company will host a webinar to discuss the data and the REGAL update today at 8:15 am ET.

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!

"Completion of enrollment in the Phase 3 REGAL trial represents an important milestone in our goal to deliver GPS to AML patients," said Angelos Stergiou, MD, ScD h.c., President and Chief Executive Officer of SELLAS. "We are extremely grateful to the patients, their families, and investigators who have helped us achieve this significant milestone. Additionally, we are pleased to share that the Steering Committee has reviewed the study as of the March 1, 2024, cutoff date. As of this evaluation, 123 patients were enrolled with 66 of them discontinuing the treatment. In the trial, patients are recorded as having stopped the study treatment in cases of death for any reason, relapse, intolerable toxicity, or treatment completion. Regarding the GPS arm, we are pleased to report that we have not observed any intolerable toxicities in any patient population across all our clinical studies thus far, although toxicities are commonly observed with therapies used in the control arm. Therefore, almost all patients who are off treatment may have most likely either relapsed or passed away. The most frequent cause of death in this patient population is relapse. As the study sponsors, we lack specific information on the outcomes of these 66 patients, hindering our ability to confirm whether the required number of events for interim analysis – 60 – has been reached. The determination of such outcomes, the primary endpoint of the trial, lies within the purview of the IDMC, which is now scheduled to meet by the end of April."

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 Committee also expressed its satisfaction with SELLAS’ overall clinical study conduct and complimented SELLAS for addressing such a debilitating and high unmet medical need as no drugs are approved in the AML CR2 maintenance setting.

Dr. Stergiou continued: "We are extremely excited to share positive topline data from the Phase 2a trial of SLS009 in AML patients resistant to venetoclax combination therapies. In the selected optimal dose regimen of 30 mg BIW a 50% response rate was achieved, far surpassing the targeted 20% rate. Notably, we identified promising biomarkers and observed a 100% response rate at the optimal dose level and a 57% response rate across all the levels tested in patients with those biomarkers. The SLS009 aza-ven treatment was well-tolerated and evoked anti-leukemic effects in 67% of patients across all levels dosed. The first patient who achieved a complete response continues on the study and remains leukemia-free 9 months post-enrollment. These compelling results from the Phase 2a reinforce our belief that SLS009 represents a potential breakthrough for relapsed and/or refractory AML patients, addressing one of the most urgent unmet medical needs."

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

Efficacy

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 mg, 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 leukemia-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, tolerability, and efficacy of SLS009 in combination with aza/ven 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 target response rate at the optimal dose level is 20% with a target median survival over 3 months. In addition, the study aims to identify biomarkers for the target patient population and enrichment for further trials.