Replimune Group Stock Plummets After FDA Rejects Cancer Drug RP1

Hagens Berman is investigating a securities class action against Replimune Group, alleging the company misled investors by overstating trial data and failing to disclose regulatory risks. The lawsuit covers investors who bought Replimune securities between November 22, 2024, and July 21, 2025. The FDA rejected Replimune's cancer drug, RP1, causing its stock to plummet.

Title: Replimune Faces Investor Lawsuit Following FDA Rejection of Key Cancer Drug

SAN FRANCISCO, Sept. 02, 2025 — Hagens Berman, a global plaintiffs’ rights law firm, is investigating a securities class action lawsuit against Replimune Group, Inc. (NASDAQ: REPL). The lawsuit alleges that Replimune misled investors by overstating the trial data for its leading cancer drug, RP1, and failing to disclose critical regulatory risks. The class action covers investors who bought Replimune securities between November 22, 2024, and July 21, 2025 [1].

The lawsuit, filed as Jboor v. Replimune Group, Inc., et al., alleges that Replimune gave investors a false sense of security by highlighting the FDA’s prior Breakthrough Therapy and Accelerated Approval designations and touting “durable response” data from its IGNYTE trial [1]. However, the company allegedly failed to disclose that the FDA was likely to find the trial's design and data inadequate for approval [1].

On July 22, 2025, Replimune publicly announced that the U.S. Food and Drug Administration (FDA) had issued a “Complete Response Letter” (CRL) for its Biologics License Application (BLA) for RP1. The CRL effectively halted the approval process for the investigational drug, which was intended to treat advanced melanoma [1]. The news triggered a massive sell-off, causing Replimune's stock to plummet by 77% in a single day, wiping out billions in market value [1].

The FDA's rejection was rooted in specific issues with the IGNYTE trial's methodology that were not previously disclosed to the public. These issues included patient heterogeneity and flaws in the design of the planned confirmatory trial [1]. The FDA found the patient population in the study to be too varied, making it difficult to draw reliable conclusions about the drug’s effectiveness. Additionally, the agency flagged issues with how the individual contributions of each drug in the combination therapy could be properly evaluated [1].

Hagens Berman is actively investigating whether Replimune misled its investors. The firm is urging investors who suffered substantial losses to submit their losses now. The lead plaintiff deadline is September 22, 2025 [1].

Investors who have knowledge that may assist the firm’s investigation are encouraged to contact Hagens Berman. The firm also reminds investors that whistleblowers who provide original information may receive rewards totaling up to 30 percent of any successful recovery made by the SEC [1].

Replimune investors are advised to carefully review the details of the class action lawsuit and consider their options. For more information, visit www.hbsslaw.com/investor-fraud/repl or contact Hagens Berman at REPL@hbsslaw.com or 844-916-0895 [1].

References
[1] https://www.globenewswire.com/news-release/2025/09/02/3142779/32716/en/Replimune-REPL-Faces-Investor-Lawsuit-Following-77-Stock-Crash-After-FDA-Rejects-Key-Drug-Hagens-Berman.html