A Study Investigating the Safety, Tolerability and Efficacy of ASP7517 in Subjects With Relapsed/Refractory Acute Myeloid Leukemia (AML) and Relapsed/Refractory Higher Risk Myelodysplastic Syndrome (MDS)

The purpose of this study was to evaluate the safety and tolerability and to determine the recommended phase 2 dose (RP2D) and/or the maximum tolerated dose (MTD) of ASP7517. This study also evaluated the clinical response of ASP7517 as well as other measures of anticancer activity of ASP7517.

This study consisted of 2 parts: phase 1 dose escalation and phase 2 dose expansion. Phase 1 Dose Escalation: Approximately 18 subjects with either relapsed/refractory (R/R) AML or R/R higher risk MDS were enrolled. Participants received 2 single doses of ASP7517 via intravenous infusion. Dosing occured on day 1 of each cycle. Each cycle was defined as 28 days with a total of 2 treatment cycles. Participants were managed under hospitalization for at least 7 days during the first cycle of the dose escalation phase. In addition, prior to hospital discharge, participant safety was ensured by performing medical tests and procedures listed on day 7 of cycle 1 and tests considered clinically necessary to evaluate the participant's general condition and adverse event (AE) resolution. The participant was also followed on an outpatient basis on planned visits during cycles 1 and 2 after hospital discharge during the dose limiting toxicity (DLT) assessment period to closely monitor any AEs. Participants were hospitalized days 1 to 7 during cycle 2. Phase 2 Dose Expansion: Approximately 104 participants per dose level were enrolled. Each dose level enrolled up to 52 R/R AML participants and up to 52 R/R higher risk MDS participants. Both groups of participants were enrolled in parallel and independently. The number of dose levels investigated during phase 2 were based upon the data from phase 1. When escalation and expansion cohorts were both open for enrollment, enrollment into escalation cohorts took priority such that participants who were eligible for both were preferentially enrolled in the escalation cohorts.