Shares of Replimune crashed nearly 32% on Tuesday after its lead skin cancer therapy came under fresh scrutiny, with FDA staff reviewers stating the company has not provided clear evidence that the drug works as claimed.

Briefing documents released ahead of an advisory committee meeting on July 30 outlined the concerns, with a final FDA decision targeted for August 2.¹ The company’s shares have been under heavy selling pressure and are on track for a fifth straight day of losses, down about 47% during that stretch. The stock also fell below its 100-day moving average for the first time in nearly two months and is down 32% so far this year.¹

What Does the FDA take issue with?

Replimune is seeking approval for RP1 in combination with Bristol Myers Squibb's immunotherapy Opdivo for patients with advanced melanoma.¹ The company based its application on the Ignyte study, which reported an objective response rate of 33.6% and a median duration of response of 24.8 months. According to Replimune, some patients achieved complete disappearance of their tumors.

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

Why is the single-arm design a concern?

Another issue for FDA is that Ignyte was a single-arm trial, meaning all patients received the combination of RP1 and Opdivo with no comparison group receiving Opdivo alone.¹ Without a control group, reviewers say they cannot determine whether RP1 contributed anything meaningful to the observed responses. FDA also says 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 (CRL), before reaching an agreement with Replimune in May 2026.² The agreement allows Replimmune to resubmit a marketing application for its lead skin cancer therapy.² Following the agreement, the agency has agreed to prioritize the review because of the significant unmet need in advanced melanoma

What's next for Replimune?

The advisory committee meeting on July 30 is expected to give outside experts a chance to weigh in on the data before the FDA's targeted decision date of August 2.¹ The core tension reviewers have flagged, that a single-arm, intratumoral injection trial makes it difficult to separate a genuine systemic anti-cancer effect from a local injection effect, sits at the center of what the committee will be asked to evaluate. For Replimune, the outcome will determine whether RP1 becomes the company's first approved therapy after two prior CRL’s, or whether the FDA's concerns about trial design and interpretability prove serious enough to prompt a third rejection.

Sources

1. FDA Staff Raise Concerns On Replimune’s Skin Cancer Drug – REPL Stock Crashes 32% Today Ahead Of Advisory Meeting This Week Yahoo Finance July 28, 2026 https://finance.yahoo.com/healthcare/articles/fda-staff-raise-concerns-replimune-145512447.html?guccounter=1&guce_referrer=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8&guce_referrer_sig=AQAAAGL4IO2QD5GBfXSk48MWTERNenfGe-gH2ZOAOs4ZdJu8RV-G9GSLFqyzcuzOZvHjQgTxi6VEsr55YM9pwFr-7xMZrXjodRwW83ANbC8QXQhLiuGSfw6awaDkLt34LrIfXh_GhFqW7UN_RyB71OLPvvvj0VsQwUfMl_3ZkAzMlCP3
2. REPL Stock Shot Up 80% Today – What’s The Deal With FDA? StockWits May 29, 2026, https://stocktwits.com/news-articles/markets/equity/repl-stock-surge-bla-agreement-fda-melanoma-drug/cZgSpMJReMf