Gilead Sciences, Inc. (Nasdaq: GILD) today announced updated results from the magrolimab Phase 1b trial. Magrolimab is an investigational, potential first-in-class, anti-CD47 monoclonal antibody being studied in previously untreated acute myeloid leukemia (AML) patients who are ineligible for intensive chemotherapy, including patients with TP53-mutant AML. The study continues to demonstrate high response rates with magrolimab in combination with azacitidine, with an overall response rate of 63% (n=27/43) among the total patient population and 69% (n=20/29) in TP53-mutant patients. The data were presented at the 62nd American Society of Hematology (ASH) Annual Meeting and Exposition (Abstract #330).

“In this ongoing study, treatment with magrolimab and azacitidine continues to achieve promising, durable responses in patients with AML who are ineligible for first-line chemotherapy,” said David Sallman, MD, H. Lee Moffitt Cancer Center and Research Institute, an investigator for the clinical trial. “These findings are especially encouraging for patients with TP53 mutations, which are associated with poor outcomes and limited response to existing treatment options.”

In the study, 64 patients were treated with magrolimab plus azacitidine, including 47 patients with the TP53 mutation, a treatment-refractory and poor-prognosis population. As of November 2020, 63% (n=27/43) of patients evaluable for efficacy achieved an objective response per European LeukemiaNet 2017 criteria, 42% (n=18/43) achieved a complete remission (CR), and 12% (n=5/43) achieved a CR with an incomplete count recovery (CRi). The median duration of response (DOR) was 9.6 months (range: 0.03+ to 18.7 months) and the median time to response was 1.95 months (range: 0.95 to 5.6 months).

For patients with the TP53 mutation, 69% (n=20/29) achieved a response, 45% (n=13/29) achieved a CR and 14% (n=4/29) achieved a CRi. The median DOR was 7.6 months (range: 0.03+ to 15.1+ months) and the minimum residual disease (MRD) negativity in patients with a CR/CRi was 29% (n=5/17).

Preliminary median overall survival (OS) for TP53-wild-type patients (n=16) was 18.9 months (95% CI: 4.34, NE) and for TP53-mutant patients (n=47) was 12.9 months (95% CI: 8.21, 17.28). The median follow-up for TP53-wild-type and TP53-mutant patients was 12.5 months and 4.7 months, respectively. Additional patients and longer follow-up in a comparative trial are needed to further characterize the survival benefit.

Treatment-related adverse events observed with over 15% incidence included anemia, fatigue, blood bilirubin increased, infusion related reaction, neutropenia, thrombocytopenia and ALT increase. Most patients were cytopenic at baseline, and no significant increased cytopenias, infections or immune-related adverse events (AEs) were observed in the study. Thirty-day all-cause mortality was 4.7% (n=3/64), and 60-day mortality was 7.8% (n=5/64). Treatment discontinuation due to drug-related AE occurred in 4.7% of all patients.

“We continue to be encouraged by the response rates seen in this study and are rapidly advancing the development of magrolimab based on its potential to help address significant unmet medical needs,” said Daejin Abidoye, Senior Vice President, Head of Oncology, Gilead Sciences.

Magrolimab is investigational and not approved anywhere globally. Its efficacy and safety have not been established.