FDA Delays Decision on GSK's Blenrep, Extending Review Period for Multiple Myeloma Treatment

The U.S. Food and Drug Administration (FDA) has extended its review period for GSK's antibody-drug conjugate Blenrep, pushing the target decision date from July 23 to October 23, 2025. This delay comes as GSK seeks to reintroduce Blenrep to the U.S. market for the second-line treatment of relapsed or refractory multiple myeloma.

FDA Concerns and Advisory Committee Feedback

The FDA's decision to extend the review period follows a series of challenges for Blenrep. In a briefing document released earlier this month, FDA reviewers highlighted concerns about the high rates of ocular toxicity and dose modifications observed in the DREAMM-7 and DREAMM-8 clinical trials. The agency questioned whether GSK had optimized the dosing regimen for the antibody-drug conjugate.

Additionally, the FDA's Oncologic Drugs Advisory Committee (ODAC) recently voted against recommending Blenrep's approval in two proposed combinations. The panel voted 7-1 against the use of Blenrep plus pomalidomide and dexamethasone, and was split 5-3 against Blenrep with bortezomib and dexamethasone.

Clinical Trial Results and GSK's Comeback Strategy

Despite these setbacks, GSK remains confident in Blenrep's potential. The company has presented data from two late-stage clinical trials to support its case for the drug's reintroduction:

1. The Phase III DREAMM-7 trial demonstrated that Blenrep, when combined with bortezomib and dexamethasone, significantly reduced the risk of death or disease progression by 59% compared to a Darzalex-based combination.

2. The DREAMM-8 trial showed Blenrep's superiority over Takeda's Velcade in patients who had undergone at least one prior line of therapy.

GSK views these results as evidence of Blenrep's "multi-blockbuster" potential in the second-line treatment setting. The company has estimated peak sales for Blenrep at more than £3 billion (approximately $4 billion) and hopes to challenge Johnson & Johnson's Darzalex in the second-line multiple myeloma market.

Global Regulatory Landscape

While Blenrep faces challenges in the United States, it has gained approval in other markets. Health Canada recently endorsed both Blenrep combinations based on the "superior efficacy results" demonstrated in the DREAMM trials. The drug has also been cleared for use in the United Kingdom and Japan.

As the FDA continues its review, the pharmaceutical industry will be closely watching the outcome, which could have significant implications for GSK's oncology portfolio and the treatment landscape for multiple myeloma patients.