For a third time, Replimune will submit its experimental cancer therapy for approval, following what the Massachusetts-based biotechnology company described as “productive” talks with the Food and Drug Administration.
According to a Friday announcement from Replimune, the two parties are aligned on a path forward for the therapy, which is codenamed RP1 and has been tested in combination with Bristol Myers Squibb’s Opdivo as a treatment for skin cancer. Replimune plans to file another marketing application “in the coming days,” and claims the FDA views this case as an urgent matter and intends to prioritize its review.
"We are grateful to the FDA leadership for their willingness to engage in a collaborative dialogue towards finding a meaningful path forward for RP1," said Replimune CEO Sushil Patel in a statement.
Replimune’s update is the latest curve in a what’s become a winding, highly unusual journey to approval. The company first submitted RP1 to the FDA in late 2024, based on data from a mid-stage clinical trial titled “IGNYTE.” The experiment enrolled 140 people with advanced melanoma, whose disease continued to progress even after receiving a kind of cancer-fighting, immune system-triggering drug known as a “PD-1 inhibitor.” Results showed that RP1 plus Opdivo — which is itself a PD-1 blocker — shrank tumors in a third of the participants. And in 15%, treatment wiped out all visible traces of the cancer.
Having met with the FDA throughout the development process, Patel was therefore surprised when the agency spurned his company’s application last July. Replimune said that, among the issues detailed in their rejection letter, FDA staff didn’t believe IGNYTE provided adequate evidence of RP1’s effectiveness. Such concerns had not been raised in prior meetings, according to Patel.
Replimune gathered additional data and analyses and resubmitted its application in October, only for the FDA to reject it again by April.
RP1 came to symbolize a widening disconnect between drug developers and an FDA that, amid major staff cuts and a revolving door of agency leaders, was seen as increasingly mercurial. Moderna, UniQure, Regenxbio, Biohaven, Vanda Pharmaceuticals and Capricor Therapeutics are among the companies that detailed conflicting or goalpost-moving feedback from the FDA when their applications were delayed or knocked down.
By late 2025, this rift had unnerved biotech investors so much that, in a survey conducted by RBC Capital Markets, nearly half of responders felt FDA volatility was the “biggest headwind.” The “multiple instances of reported regulatory flip-flopping” raise concerns that “may continue to pose a challenge to perceived investability,” wrote RBC analyst Brian Abrahams.
“Really the broader takeaway here for us is that FDA — and our ability to predict the FDA — is about as uncertain as it’s been in the past decade or longer,” Stifel analyst Paul Matteis wrote, after the agency turned against UniQure’s gene therapy for Huntington’s disease.
With Replimune, it’s “obvious [the company] got caught in a changing FDA regulatory landscape,” wrote Li Watsek, an analyst at Cantor Fitzgerald, in a note to cleints.
Yet recent resignation — or firing — of top FDA officials like Marty Makary, Vinay Prasad and Tracy Beth Høeg signals the FDA may again be shifting course, this time in a way drug developers and their investors prefer.
Shares of Replimune spiked nearly 80% by late Friday morning. Biohaven and UniQure also saw their stock price lift by mid-single digits to low-double digits.
