Dual FLT3/PIM inhibitor dapolsertib in acute myeloid leukemia: results from the phase 1/2 DIAMOND-01 trial

Acute myeloid leukemia (AML) is an aggressive hematopoietic cancer with poor survival outcomes. Despite improvements with recent FMS-like tyrosine kinase 3 (FLT3) inhibitors, resistance is common, and responses are short. Dapolsertib (MEN1703) is a novel, first-in-class dual inhibitor of PIM (proviral integration site for Moloney murine leukemia virus) and FLT3 kinases, with activity in both FLT3-mutated and wild-type cells. A phase 1/2 open-label, multicenter, dose-escalation study (DIAMOND-01) investigated the maximum tolerated dose (MTD) of single-agent dapolsertib and assessed its safety, efficacy, pharmacokinetic (PK) profile, pharmacodynamic biomarkers, and genomics in patients with AML with no standard therapeutic options available. Seventy-three patients received oral doses of dapolsertib ranging from 25 to 150 mg per day (14 consecutive days over 21-day cycles). In the dose-escalation phase, the MTD was 125 mg and was selected for dose expansion. The most common grade ≥3 adverse events in patients receiving 125 mg were pneumonia (38%), thrombocytopenia (30%), and anemia (27%); most of these events were deemed not treatment related. For patients receiving 125 mg dapolsertib (n = 55), the overall response rate was 9%, with a median 2.07-month duration of response, and 4 of 5 responses were observed in patients with isocitrate dehydrogenase 1 (IDH1)/IDH2 mutations. PK analysis indicated rapid absorption of oral dapolsertib, an elimination half-life suitable for once daily dosing and a PK independent of formulation and IDH mutational status. Pharmacodynamic activity was confirmed in 50% of evaluable patients. Overall, dapolsertib demonstrated modest single-agent activity in patients with AML. This trial was registered at www.clinicaltrials.gov as #NCT03008187.