FDA Delays Decision on GSK's Blenrep, Extending Review Period

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 treatment of relapsed or refractory multiple myeloma in patients who have received at least one prior line of therapy.

Regulatory Hurdles and Clinical Data

GSK's efforts to bring Blenrep back to the U.S. market have faced significant challenges. The drug was initially granted accelerated approval in August 2020 but was voluntarily withdrawn in November 2022 after failing its confirmatory Phase III DREAMM-3 study. The company has since presented new data from two late-stage trials, DREAMM-7 and DREAMM-8, in an attempt to build a case for Blenrep's clinical comeback as a second-line treatment option.

The DREAMM-7 study demonstrated that Blenrep, when combined with bortezomib and dexamethasone, reduced the risk of death or disease progression by 59% compared to a Darzalex-based combination. Similarly, DREAMM-8 showed Blenrep's superiority over Takeda's Velcade in patients who had undergone at least one prior line of therapy.

Despite these positive results, the FDA has expressed concerns about the drug's safety profile. In a briefing document, agency reviewers highlighted "high rates of ocular toxicity and dose modifications" observed in the DREAMM-7 and DREAMM-8 trials, suggesting that GSK had not optimized the dosing regimen for Blenrep.

Advisory Committee Feedback and Global Approvals

The FDA's Oncologic Drugs Advisory Committee (ODAC) echoed these concerns in a recent meeting, voting 7-1 against the use of Blenrep in combination with pomalidomide and dexamethasone. The committee was split 5-3 against Blenrep with bortezomib and dexamethasone. While the FDA is not required to follow the recommendations of its advisory panels, it often does.

In contrast to the FDA's cautious approach, Health Canada has endorsed both Blenrep combinations based on the "superior efficacy results" demonstrated in the DREAMM trials. The drug has also received approvals in other markets, including the United Kingdom and Japan.

Implications for GSK and the Multiple Myeloma Treatment Landscape

The delayed FDA decision represents a critical moment for GSK's oncology portfolio. The company has estimated Blenrep's peak sales potential at more than £3 billion (approximately $4 billion) and views the drug as key to achieving its goal of generating total sales exceeding £40 billion by 2031.

GSK remains confident in the data supporting Blenrep combinations and looks forward to ongoing discussions with the FDA. The company is also exploring Blenrep's potential in the first-line setting, with a trial expected to read out by the end of 2027.

As the pharmaceutical industry awaits the FDA's final decision, the outcome will likely have significant implications for the treatment landscape of multiple myeloma and GSK's position in the oncology market.