Replimune falls after FDA staff flags efficacy concerns about skin cancer therapy

Shares of drug developer Replimune REPL.O fell 32% to $5.86 after U.S. FDA staff said the clinical trial conducted for Replimune's therapy, RP1, did not provide substantial evidence that it works when combined with Bristol Myers Squibb's BMY.N nivolumab in advanced melanoma.

The staff's findings were published in briefing documents released ahead of an advisory committee meeting on Thursday, where a panel of outside experts will discuss the therapy's benefits.

FDA staff reviewers said results from a trial lacking a randomized control group could not establish whether longer survival was due to the treatment rather than patient selection or other factors. The staff also said the trial could not determine whether RP1, rather than nivolumab alone, drove the observed benefit.

In April, the health regulator declined to approve the drug for a second time, citing insufficient data from studies.

Including session's move, the stock was down 40% year to date.