FDA Staff Raise Concerns On Replimune’s Skin Cancer Drug – REPL Stock Crashes 32% Today Ahead Of Advisory Meeting This Week

• FDA reviewers said the tumor assessment method may have overstated both the response rate and the duration of response.
• The agency reviewers also highlighted the challenges due to Replimune’s IGNYTE study being a single-arm trial.
• In May 2026, the FDA agreed to prioritize the review because of the significant unmet need in advanced melanoma.

Shares of Replimune (REPL) crashed nearly 32% on Tuesday after its lead skin cancer therapy came under fresh scrutiny, with U.S. Food and Drug Administration staff reviewers stating the company has not provided clear evidence that the drug works as claimed.

The concerns were outlined in briefing documents released ahead of an advisory committee meeting on July 30. A Final FDA decision is targeted for August 2. 

REPL shares have been under heavy selling pressure and are on track for a fifth straight day of losses, with the stock down about 47% during that stretch. The stock also fell below the 100-day (100-DMA) for the first time in nearly two months.

FDA Says Trial Design Makes Results Hard To Interpret

Replimune is seeking approval for RP1 in combination with Bristol Myers Squibb’s immunotherapy Opdivo for patients with advanced melanoma. The company based its application on the IGNYTE study, which reported an objective response rate (ORR) of 33.6% and a median duration of response of 24.8 months. According to Replimune, some patients achieved complete disappearance of their tumors.

However, FDA reviewers said the way tumor responses were measured using RECIST v1.1 criteria may have artificially inflated both the response rate and the duration of response. Because RP1 is injected directly into tumors, the agency said the shrinkage seen in treated tumors could reflect a local injection effect rather than a broader anti-cancer effect throughout the body.

Single-Arm Trial A Concern

Another issue for the FDA is that IGNYTE was a single-arm trial, meaning all patients received the combination of RP1 and Opdivo and there was no comparison group receiving Opdivo alone.

Without a control group, reviewers said they cannot determine whether RP1 contributed anything meaningful to the observed responses. The FDA also said the overall survival data submitted by Replimune cannot be reliably interpreted to show a treatment benefit.

The latest review adds to a difficult regulatory history for Replimune. The FDA previously rejected the RP1 application in July 2025 and again in April 2026 through Complete Response Letters, before reaching an agreement with Replimune in May 2026. The agency had agreed to prioritize the review because of the significant unmet need in advanced melanoma.

Retail’s Take On FDA Response  

Meanwhile, retail sentiment surrounding REPL on Stocktwits turned ‘extremely bullish’ from ‘bullish’ a day earlier, amid a 1,100% increase in message volumes.

One user opined that swift FDA acceptance of an application is not an endorsement.

Another user highlighted the FDA’s response and added that the same criticism had surrounded the company “for a long time.”

The stock is down 32% so far this year.

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