FDA staff flags eye safety risks for GSK’s blood cancer drug

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By Sneha S K and Sriparna Roy

(Reuters) -The U.S. Food and Drug Administration’s staff reviewers on Tuesday raised safety concerns that GSK’s blood cancer drug Blenrep, when used in combination with other treatments, may cause eye damage in patients.

In briefing documents released on the health regulator’s website, staff reviewers said the benefit-risk profile of Blenrep remains unclear, citing concerns about safety, tolerability and appropriate dosages.

The agency noted incidents of ocular toxicity such as blurred vision, photophobia, and dry eye in patients receiving the combination treatment. Blenrep’s initial approval already carried a warning about ocular side effects.

The assessment comes ahead of an independent expert panel meeting on Thursday. The FDA is set to decide on the drug next week.

The questions and briefing documents were less negative than feared, with no direct concerns raised about patient enrollment — a key investor worry — according to at least two analysts.

However, “the focus on dosing and benefit-risk indicates this will still be a tricky meeting (and potentially) launch”, said Barclays analyst Emily Field. Shares of the company were volatile after the publication of the documents.

The panel will discuss if an appropriate dosage has been identified and will vote on the overall benefit-risk profile of the drug in combination with other treatments.

The ocular toxicity observed “is a unique toxicity not seen with any currently available treatments for multiple myeloma,” staff reviewers said.

The agency noted that the dose adjustment protocols and ophthalmic monitoring schedules implemented in the trials may be difficult to reproduce in routine clinical practice, raising concerns about the drug’s use outside tightly controlled study settings.

Blenrep belongs to a class of targeted cancer therapies called antibody drug conjugates that work like “guided missiles,” killing tumor cells while leaving healthy ones unharmed.

The British drugmaker is seeking approval for Blenrep in combination with bortezomib plus dexamethasone and pomalidomide plus dexamethasone for the treatment of patients with multiple myeloma who have received at least previous therapy.

Both bortezomib and pomalidomide are established cancer therapies, while dexamethasone is a widely used generic steroid drug.

(Reporting by Sriparna Roy and Sneha S K in Bengaluru; Editing by Tasim Zahid)