Forty Seven, Inc. announced the presentation of updated clinical data from its ongoing trial evaluating magrolimab in combination with azacitidine for the treatment of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). The new results, which will be shared in an oral presentation at the 61stAmerican Society of Hematology (ASH) Annual Meeting in Orlando, Florida, show that the combination of magrolimab and azacitidine is highly active and well-tolerated in patients with MDS and AML. Forty Seven’s Phase 1b trial, which is being funded in part by the California Institute of Regenerative Medicine (CIRM), is designed to evaluate magrolimab in combination with azacitidine in untreated patients with higher risk MDS and untreated patients with AML, who are ineligible for induction chemotherapy. All patients received a 1 mg/kg priming dose of magrolimab, coupled with intrapatient dose escalation, to mitigate on-target anemia. Patients were then treated with full doses of azacitidine and a magrolimab maintenance dose of 30 mg/kg once weekly. As of the data cutoff of November 18, 2019, 62 patients had been treated with the combination in the Phase 1b portion of the trial, including 35 patients with MDS and 27 patients with AML. As of the data cutoff, 46 patients were evaluable for response assessment, including 24 patients with untreated higher-risk MDS and 22 patients with untreated AML, who are ineligible for induction chemotherapy. In higher-risk MDS, the overall response rate (ORR) was 92%, with 12 patients (50%) achieving a complete response (CR), eight patients (33%) achieving a marrow CR and two patients (8%) achieving hematologic improvement. Additionally, two patients (8%) achieved stable disease. In untreated AML, the ORR was 64%, with nine patients (41%) achieving a CR, three patients (14%) achieving a CR with complete blood count recovery (CRi) and one patient (5%) achieving a morphologic leukemia-free state (MLFS). Additionally, seven patients (32%) achieved stable disease (SD) and one patient (5%) had progressive disease. The median time to response among MDS and AML patients treated with the combination was 1.9 months. No median duration of response or overall survival has been reached for either MDS or AML patients, with a median follow-up of 6.4 months (range 2.0 to 14.4 months) for MDS and 8.8 months (range 1.9 to 16.9 months) for AML. Additionally, mutational analyses are ongoing to correlate subgroups with response. Seven of nine (78%) evaluable TP53 mutant AML patients achieved an objective response, with 44% achieving CR and 33% achieving CRi. TP53 mutations are often associated with a poor prognosis and patients with TP53 mutant disease are refractory to existing therapies. Lastly, in AML patients who achieved an objective response, a significant increase in CD4 and CD8 T cell infiltration was observed in the bone marrow while on therapy, demonstrating that magrolimab and azacitidine can induce an adaptive T cell response.