Abstract
PURPOSE: Magrolimab is a monoclonal antibody directed against the macrophage checkpoint CD47 on myeloid leukemia cells that was preclinically synergistic with azacitidine-venetoclax, warranting further clinical evaluation. PATIENTS AND METHODS: In this phase Ib/II study, the triplet combination of azacitidine, venetoclax, and magrolimab was evaluated in adult patients with first-line (ineligible for intensive chemotherapy) and relapsed/refractory acute myeloid leukemia. Azacitidine was dosed at 75 mg/m2 for 7 days, venetoclax at 400 mg/day for 28 days, and magrolimab (recommended phase II dose) as follows: 1 mg/kg dose on days 1 and 4, 15 mg/kg on day 8, and 30 mg/kg on days 11, 15, and 22 (cycle 1), followed by 30 mg/kg weekly for cycle 2 and then 30 mg/kg every 2 weeks for cycle 3 and beyond. The primary endpoint was the recommended phase II dose for phase Ib and rates of composite complete response (CRc) in phase II. RESULTS: The first-line cohort included 54 patients (median age 70.1 years); 35 (64.8%) were TP53 mutated (TP53mut). CRc was attained in 34 patients (63%)-49% in TP53mut and 90% in the TP53 wild-type patients. At a median follow-up of 27.9 months, the median event-free survival and overall survival (OS) were 6.6 and 9.8 months, respectively; for TP53mut patients, the median event-free survival and OS were 5.9 and 7.6 months, whereas for TP53 wild type, they were 9.6 and 13 months, respectively. CRc in the relapsed/refractory cohort (n = 52) was 29% and the median OS was 3.9 months. The regimen was well tolerated; infections were the most common ≥ grade 3 adverse event (75.4%) with no immune toxicities or deaths related to therapy. Single-cell RNA sequencing was performed on 27 longitudinal samples from 11 TP53mut patients (eight responders). Gene set enrichment analysis revealed enrichment of IFNγ and TNFα signaling in nonresponders at baseline, whereas erythroid differentiation was associated with resistance. Patients at relapse also showed upregulated CD47 expression and elevated leukemia regeneration score. CONCLUSIONS: The triplet regimen was safe but did not lead to promising survival outcomes.