An experimental Gilead Sciences cancer drug showed an increased risk of death in a Phase 3 clinical trial, leading the FDA to place all tests of the immunotherapy in two types of blood cancers under a full clinical hold. But rather than working with the regulator to resolve the hold, Gilead will instead discontinue the pivotal study and stop further development of the drug for blood cancers, marking the latest setback to a once promising drug candidate acquired in a $4.9 billion deal.
Gilead said Wednesday that the safety finding came from a planned interim analysis of data from a Phase 3 test in acute myeloid leukemia (AML). This analysis by the study’s independent data monitoring committee found not only that this pivotal test of the drug, magrolimab, was unlikely to succeed, but also that participants face an increased risk of death. That risk was driven primarily by infections and respiratory failure, Gilead said.
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Magrolimab is an immunotherapy. The antibody drug is designed to block CD47, a protein on the surface of cancer cells that sends out a signal to macrophages, a type of immune cell. This signal stops macrophages from recognizing cancer cells cancer cells as a target. Blocking the signal is intended to clear the way for macrophages to recognize and kill cancer cells.
The Phase 3 test in AML evaluated magrolimab alongside azacitidine and venetoclax, two standard therapies for this type of cancer. That combination was compared to placebo with azacitidine and venetoclax. The study enrolled newly diagnosed AML patients who are ineligible for intensive chemotherapy. The main goal was to measure overall survival.
Gilead said its decision to stop work on magrolimab in blood cancers is also informed by two other studies in myelodysplastic syndromes and AML with TP53 mutations. Both studies were placed under a partial clinical hold two years ago. That hold was lifted months later. Gilead did not explain what sparked the safety concern, saying only that the FDA removed the partial hold after reviewing safety data from each trial.
Gilead also provided no additional details about the safety findings from the latest AML study. The company said it will provide a summary of all pivotal tests of magrolimab studies shortly. Patients in the AML study will discontinue treatment with magrolimab and Gilead will talk with study investigators to determine the appropriate next steps for these study participants. Analyses for both safety and efficacy are ongoing, and Gilead said additional details across all of the studies will be shared with regulators and submitted for presentation at an upcoming medical meeting. Those details could also be submitted for publication in a peer-reviewed journal.
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The clinical program for magrolimab includes tests of the immunotherapy in solid tumors. Gilead said it is reviewing the safety of magrolimab in all ongoing solid tumor trials and “will provide an update on this assessment as soon as possible.”
Magrolimab came to Gilead via the 2020 acquisition of Forty Seven, a cancer drug developer that took its name from the protein it targeted. That acquisition paved the way for a series of deals in the CD47 space. AbbVie began a CD47 partnership with I-Mab in 2020, though that alliance ended this past fall. Pfizer paid $2.3 billion to buy CD47 drug developer Trillium Therapeutics in 2021. A drug candidate from this acquisition has reached mid-stage clinical development.
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