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Side effects don’t stop FDA panel from backing GSK blood cancer drug

  • Outside experts urged the Food and Drug Administration to approve GlaxoSmithKline’s experimental multiple myeloma therapy belantamab mafodotin, voting 12-0 in an advisory committee meeting Tuesday that the drug’s benefits outweigh its risks.
  • FDA reviewers had raised questions about the drug, pointing to an eye-related side effect that led to declines in visual acuity. GSK has proposed dose modifications to counter that risk, but FDA reviewers pointed out that some patients in clinical trials still had unresolved eye problems even with the modifications.
  • Belantamab mafodotin is one of a group of experimental agents seeking to treat multiple myeloma by targeting a protein called BCMA that’s commonly found on cancerous plasma cells. If the FDA approves it on time this month, it would be the first of its type to launch.

The BCMA protein has emerged as a target of interest in multiple myeloma because it is expressed on malignant cells but not on normal tissue. As a result, drugmakers have developed several different approaches to home in on BCMA-expressing cells, including CAR-T cell therapy, which has been successful in treating other blood cancers like leukemia and lymphoma.

Belantamab mafodotin links a BCMA-targeting antibody to a chemotherapy payload. The combined drug binds to diseased cells and releases the chemotherapy into the diseased cells while sparing healthy tissue. GSK is asking FDA to approve it in very sick patients whose disease has progressed following four previous rounds of multiple myeloma therapy.

In the trial GSK submitted when it sought FDA approval, treatment led to remission in 31% of patients, although only 3% experienced complete remission. Patients taking the dose GSK selected went about three months before their disease progressed or they died.

But at that dose, 71% of patients suffered a side effect called keratopathy, a buildup of tissue in the eye that can cause vision loss or a decline in acuity. Severe, disabling keratopathy was reported in 44% of patients, and at the time of the trial’s primary analysis, roughly one quarter of patients had unresolved keratopathy.

GSK proposed a risk-management plan that would involve an eye exam before every dose of belantamab mafodotin, which occur every three weeks. Those eye exams would then be used to guide treatment.

Although the agency is not bound by the advisory committee’s decision, the 12-0 vote in favor of the drug’s approval will make it more difficult for top FDA officials to reject the drug.

While approval would make belantamab mafodotin the first BCMA-targeting agent to reach patients, others are progressing. The most immediate competitive threat is Bristol-Myers Squibb and Bluebird bio’s CAR-T idecabtagene vicleucel, or ide-cel, which the FDA knocked back in May.

Another CAR-T from Johnson & Johnson could be submitted to regulators this year, and Regeneron is advancing a type of antibody that is designed to draw cancer fighting T cells to diseased cells by binding with BCMA.