GSK's Blenrep Faces FDA Setback Over Eye-Related Side Effects

GlaxoSmithKline's (GSK) blood cancer drug Blenrep has been recommended against approval by the FDA advisory committee due to concerns about eye-related side effects. The setback comes as GSK focuses on expanding its research and development pipeline to counter declining sales of its top drugs and vaccines. The FDA is set to make a formal decision soon, with analysts suggesting it is unlikely to approve the drug. GSK forecasts peak annual sales of Blenrep to exceed £3 billion ($4 billion).

GlaxoSmithKline's (GSK) blood cancer drug Blenrep has faced a setback after the FDA advisory committee recommended against its approval due to concerns about eye-related side effects. The advisory committee, meeting on Thursday, cited serious eye-related side effects as a primary concern, stating that the risks of the drug outweigh its benefits in treating multiple myeloma [1].

The drug, belantamab mafodotin, causes ocular toxicity that is "unique" and not seen with any currently available treatments for multiple myeloma, according to FDA staff reviewers. The reviewers also questioned the company's selected dose, suggesting that lower dosages could offer similar efficacy while reducing the risk of side effects [1].

This recommendation comes at a critical time for GSK, which is focusing on expanding its research and development pipeline to offset declining sales of its top drugs and vaccines. The company's shares fell as much as 7% to 1,315 pence on Friday, making it the biggest loser on the FTSE 100 index [2].

The FDA is expected to make a formal decision on Blenrep by next week. Analysts from Berenberg Bank and JPMorgan suggest that the regulatory body is unlikely to approve the drug, as it typically follows the advisory committee's recommendations [3].

GSK remains confident in Blenrep's benefit-risk profile and plans to continue working closely with the FDA. The company forecasts peak annual sales of the drug to exceed £3 billion ($4 billion). The therapy is currently under review in over 10 countries [3].

References:
[1] https://trial.medpath.com/news/bd736a8ce354f30c/fda-advisory-panel-votes-against-gsk-s-blenrep-for-multiple-myeloma-over-eye-safety-concerns
[2] https://kfgo.com/2025/07/18/gsk-shares-fall-after-blood-cancer-drug-likely-headed-for-u-s-rejection/
[3] https://www.gurufocus.com/news/2986876/gsk-faces-setback-as-fda-advisers-recommend-against-blenrep-approval