Magrolimab plus azacitidine (AZA) improved outcomes in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) patients according to the results of a phase 1b study (NCT03248479) presented at the virtual ASCO meeting. The combo especially was promising for the underserved patient population that have the TP53 (p53) mutation.
Magrolimab is a first-in-kind IgG anti-CD47 monoclonal antibody that promotes the elimination of tumor cells through macrophage phagocytosis. CD47 is a “do not eat me” signal on cancer cells that allows the cells to evade macrophages. Its increased expression is predictive of a worse outcome in AML patients, according to David A. Sallman, MD, of the Moffitt Cancer Center, Tampa, Fla., and colleagues.
Dr. Sallman presented the results of a study examining whether magrolimab would provide a synergistic benefit when combined with AZA (which induces other prophagocytic “eat me” signals such as calreticulin on cancer cells). The primary objectives of the study were to examine the safety of magrolimab alone or with AZA, and to assess the efficacy of the magrolimab/AZA combo in 29 untreated AML patients and 39 untreated MDS patients. The majority of both the MDS and AML patients were poor cytogenetic risk at 64% and 72%, respectively. Mutant p53 was present in 13% of the MDS patients and 45% of the AML patients.
No deaths occurred in the first 60 days of the study among either the MDS or AML patients and discontinuation of treatment because of drug-related adverse events was seen in only one of the patients (1.5%) treated with magrolimab/AZA. There was no significant neutropenia or thrombocytopenia caused by the therapy seen, and the majority of the patients improved their neutrophil and platelet counts while on therapy.
Anemia from CD47 blockade was mitigated by the use of a priming dose of magrolimab coupled to a maintenance-dose regimen, resulting in a mild hemoglobin drop on the first dose, which returned to baseline with a majority of patients experiencing significant hemoglobin improvement and a decrease in transfusion frequency over time, according to Dr. Sallman and his colleagues.
The results showed that magrolimab/AZA induced a 91% overall response rate (ORR), with a 42% complete remission (CR) that increased to 56% at 6 months, in the MDS patients. AML patients experienced a 64% ORR (56% CR/CRi [CR with incomplete hematological remission]). These results compare favorably with the CR rate of 6%-17% rate seen for AZA monotherapy, according to Dr. Sallman.
Red blood cell transfusion independence was achieved in 58% of the MDS patients and 64% of the AML patients, and a complete cytogenetic response was seen in 35% and 50% of the MDS and AML patients, respectively.
The combined treatment was especially effective in the patients with p53 mutations, with an overall response rate of 75% for both MDS and AML, and a complete response of 42% and 50%, respectively. During the reported time of the study, the median survival was not reached, which compares favorably with current therapies, according to Dr. Sallman.
“Specifically looking at a very-high-risk p53-mutant subset, complete remissions have been observed in the majority of patients. And again, these have been durable. Based on all of these data, expansion cohorts both in MDS and p53 and AML continue to accrue with registrational studies in progress for MDS and planned for p53-mutant AML,” Dr. Sallman concluded.
The trial was sponsored by Gilead Sciences, and funding was obtained from the California Institute for Regenerative Medicine. Dr. Sallman disclosed that he received research funding from Celgene and has acted in a consulting or advisory role for Agios, argenx, and Celyad. He was also on the speaker’s bureau for a variety of pharmaceutical/biotech companies.
SOURCE: Sallman DA et al. ASCO 2020, Abstract 7507.