The U.S. Food and Drug Administration (FDA) staff has raised concerns about the safety of GSK's blood cancer drug Blenrep, particularly regarding eye damage when used in combination with other treatments. The concerns were highlighted in briefing documents released by the FDA ahead of an independent expert panel meeting.

Key highlights

FDA safety concerns

• FDA staff raised concerns over the ocular toxicity associated with Blenrep, especially when used in combination treatments.

• Incidents of blurred vision, photophobia (light sensitivity), and dry eye were reported in patients.

• The FDA emphasized that the benefit-risk profile of Blenrep remains unclear, with concerns about safety, tolerability, and appropriate dosages.

Ocular toxicity

• The FDA noted that the ocular toxicity observed with Blenrep is unique and not seen with other treatments for multiple myeloma.

• There were concerns that the dose adjustment protocols and ophthalmic monitoring schedules used in clinical trials may be difficult to replicate in real-world clinical settings.

FDA review and panel discussion

• The FDA will decide on the drug's approval after an expert panel meeting.

• The panel will discuss if an appropriate dosage has been identified and vote on the overall benefit-risk profile of Blenrep when used in combination with other treatments like bortezomib and pomalidomide.

Blenrep's potential in cancer treatment

• Blenrep is a targeted cancer therapy in the antibody-drug conjugate class, designed to kill tumor cells while leaving healthy cells unharmed.

• GSK is seeking approval for Blenrep in combination with bortezomib and dexamethasone, and pomalidomide and dexamethasone for treating multiple myeloma patients who have received at least one prior therapy.

Market impact and investor concerns

• Following the release of FDA documents, GSK’s shares experienced volatility, with investor concerns about patient enrollment and drug launch continuing to linger.

• Analysts note that while the briefing documents were less negative than expected, the focus on dosing and safety still makes the upcoming panel meeting critical.

The FDA's concerns over eye safety and the potential challenges of administering Blenrep outside controlled settings underline the uncertainty surrounding the drug's use in broader clinical practice. The outcome of the expert panel meeting will likely play a crucial role in determining whether Blenrep becomes a widely available treatment for multiple myeloma.