IDMC Recommends Continuation of REGAL Trial of Galinpepimut-S in AML

Angelos Stergiou, MD, ScD hc

An independent data monitoring committee (IDMC) has recommended that the phase 3 REGAL trial (NCT04229979) examining galinpepimut-S (GPS) in patients with acute myeloid leukemia (AML) continue as planned without modifications.¹

The recommendation follows a positive prespecified risk-benefit assessment of unblinded data from the study. The IDMC proposed meeting again in the third quarter of 2023, and the group also endorsed all clinical trial initiatives of REGAL, including the addition of sites in China.

“This positive IDMC review marks another significant milestone in GPS development and builds on the favorable profile of our study drug, GPS,” Angelos Stergiou, MD, ScD hc, president and chief executive officer of SELLAS Life Sciences Group, stated in a news release. “Enrollment continues in our global phase 3 REGAL registrational study, which currently remains on track for interim analysis by the end of 2023 or early 2024.”

The open-label REGAL study is enrolling patients with AML who have achieved complete remission following second-line salvage therapy, defined as having less than 5% myeloblasts in bone marrow, absence of Auer rods, the absence of circulating peripheral blasts, a peripheral blood absolute neutrophil count of more than 1000 cells/µL, a peripheral blood platelet count of more than 20,000/µL, and the absence of extramedullary disease.² Patients are also required to have more than 300 lymphocytes/µL, an ECOG performance status of 0 to 3, and a life expectancy of more than 6 months.

Patients must not be candidates for allogeneic stem cell transplant due to intercurrent medical conditions, patient preference, or lack of an available donor.

Enrolled patients are being randomly assigned to receive GPS or best available therapy consisting of observation where palliative management with hydroxyurea (Hydrea) is permitted, or decitabine or azacitidine (Vidaza), and/or venetoclax (Venclexta), and/or low-dose ara-C.

For patients in the experimental arm, GPS is administered for a maximum of 15 total injections. The first 6 injections are given once every 2 weeks from weeks 0 to 10, followed by a 4-week period of no treatment. Injections 7 to 12 are then administered once every 4 weeks, followed by a 6-week, treatment-free period. The final 3 injections are given once every 6 weeks between weeks 40 and 52.

The primary end point is overall survival (OS). Secondary end points include leukemia-free survival (LFS) up to 156 weeks; OS and LFS rates at 6, 9, and 12 months; and minimal residual disease up to 91 weeks.

In November 2022, SELLAS announced modifications to the study based on consultation with the IDMC, AML experts, and the company’s biostatistics experts.³

The changes included:

1. An increase in the total targeted enrollment for the study from 116 patients to a range of 125 to 140 patients.
2. A reduction in the targeted number of fatal events for the interim analysis from 80 to 60, which is currently expected to occur in late 2023 or early 2024.
3. A reduction in the targeted number of fatal events for the final analysis from 105 to 80, which is currently expected to occur by the end of 2024.
4. Statistical significance would be achieved by an estimated hazard ratio for OS of 0.636, corresponding to an OS of 12.6 months for GPS vs 8 months for best available therapy.

In December 2022, the IDMC recommended the study continue as planned with those modifications.⁴

References

1. SELLAS Life Sciences independent data monitoring committee recommends galinpepimut-S REGAL trial to continue as planned. News release. SELLAS Life Sciences. April 18, 2023. Accessed April 19, 2023. https://www.sellaslifesciences.com/investors/news/News-Details/2023/
2. Galinpepimut-S versus investigator's choice of best available therapy for maintenance in AML CR2/CRp2 (REGAL). ClinicalTrials.gov. Updated February 1, 2023. Accessed April 19, 2023. https://clinicaltrials.gov/ct2/show/NCT04229979
3. SELLAS Life Sciences announces update on phase 3 REGAL clinical trial evaluating lead asset, galinpepimut-S, in acute myeloid leukemia. News release. Sellas Life Sciences Group, Inc. November 14, 2022. Accessed April 19, 2023. https://www.sellaslifesciences.com/investors/news/News-Details/2022/
4. SELLAS Life Sciences’ independent data monitoring committee recommends galinpepimut-S REGAL trial to continue as planned. News release. SELLAS Life Sciences. December 8, 2022. Accessed April 19, 2023. https://www.sellaslifesciences.com/investors/news/News-Details/2022/