Phase III REGAL study of galinpepimut-S shows extended benefits in acute myeloid leukemia

The primary endpoint of the REGAL study is overall survival (OS).

The trial was originally designed using certain assumptions regarding OS for both the GPS treatment arm and the control arm receiving best available treatment (BAT) which are reflected in the protocol and statistical analysis plan (SAP) for the study. A review of preliminary data to date, which was pooled (i.e., GPS arm plus control arm) and which remains blinded as to treatment arm, suggests that the median OS in the pooled study population is likely considerably longer, by approximately two-fold, than originally anticipated and upon which the SAP was based. Accordingly, the overall duration of the REGAL study is now expected to be longer than initially predicted.

Following consultation with members of the Independent Data Monitoring Committee for the REGAL study and AML key opinion leaders, as well as the recommendations of the Company’s biostatistics experts, SELLAS is implementing changes to the SAP and protocol for the REGAL study as follows: The total targeted enrollment in the study will increase from 116 patients to a range of 125 to no more than 140 patients. The targeted number of events (deaths) for the interim analysis will be reduced to 60 from 80 and is currently expected to occur in late 2023 or early 2024. The targeted number of events (deaths) for the final analysis will be reduced to 80 from 105 and is currently expected to occur by the end of 2024. Statistical significance would be achieved by an estimated hazard ratio (HR) for OS of 0.636, corresponding to an OS of 12.6 months versus eight months for GPS versus BAT, respectively.