Why Is Replimune (REPL) Stock Up 127%? An FDA Panel Backed RP1 After Two Rejections, and the Decision Lands This Weekend

TL;DR

• Replimune surged as much as 127% after an FDA advisory panel voted 10-3 that RP1 combined with nivolumab shows a clinically meaningful benefit in advanced melanoma. The stock ran from about $10.86 to above $13 before settling in the low $12s, adding roughly $600 million of equity value.
• This is the third attempt. Replimune received complete response letters in July 2025 and again in April 2026.
• Six days ago the same stock crashed 32%, its worst day in over three months, when FDA staff published briefing documents questioning whether the single-arm IGNYTE study proved anything.
• The panel disagreed with the agency's own scientists, calling the efficacy data "evaluable and clinically meaningful."
• The binary is not resolved. The FDA's decision date is August 2, which is a Sunday. An advisory committee vote is a recommendation, not an approval, and the agency is not bound by it.

Why Is Replimune Stock Up Today?

The short answer: an independent FDA advisory committee voted 10-3 on Thursday that Replimune's RP1, given with nivolumab, produces a clinically meaningful benefit in advanced melanoma. That vote directly contradicted the FDA's own reviewers, who had spent the week arguing the trial could not support approval.

For a company whose drug has been rejected twice, a panel siding with the company over the agency is close to the best possible outcome short of approval itself.

What Actually Happened This Week

The sequence matters more than the percentage, because it tells you how little anyone knows.

Date	Event	Stock
~July 25	FDA staff briefing documents question RP1 efficacy	down 32%, worst day in 3 months
July 30	Advisory panel votes 10-3 in favour	rallies after hours
July 31	Market reprices the approval odds	up as much as 127%
August 2	PDUFA goal date. FDA decides.	to be determined

A stock that falls 32% and then rises 127% inside six sessions is not a stock the market is valuing. It is a coin the market is watching land in slow motion. Each move was a wholesale re-rating of a single probability, and neither move contained any new clinical data. The drug did not change. The odds changed.

The Board

Down 32% on the FDA's doubts, up 127% on the panel's vote. The drug did not change. The odds did.

Why the Panel Vote Matters More Than Usual

Advisory committee votes are often a formality. This one was not, for a specific reason: the panel overruled the agency's own review team in public.

FDA scientists had argued that IGNYTE, a single-arm study without a control group, could not isolate what RP1 contributed. That is a real methodological objection and it is the objection that produced two prior rejections.

The panel heard it and voted 10-3 the other way, concluding the results were evaluable and clinically meaningful. Ten independent experts looked at the same data the FDA reviewers looked at and reached the opposite conclusion.

That does two things. It raises the probability of approval, obviously. But it also raises the cost of a rejection to the agency, which would now have to reject a drug its own advisory committee endorsed by better than three to one, in a disease where the patients in question have run out of options. Regulators are not immune to that arithmetic.

Why This Is Still a Coin Flip You Should Not Trade

Here is the part the 127% is hiding.

The FDA is not bound by its advisory committees. It usually follows them, but "usually" is doing a great deal of work in a company that has already been rejected twice on this exact question. The two prior complete response letters were not about safety or manufacturing, which are fixable. They were about whether the evidence proves the drug works, and a single-arm trial is still a single-arm trial after a favourable vote.

The decision date is August 2, and August 2 is a Sunday.

That is not trivia, it is the whole risk-management problem. The FDA can announce on the Friday before, over the weekend, or after the deadline. If the news lands Saturday or Sunday, there is no market open for you to react in. You will find out what your position is worth at the Monday opening auction, and the gap will be enormous in whichever direction it goes. There is no stop-loss, no hedge and no exit between the announcement and the print.

And the upside is already partly paid for. The stock has already moved 127%. The approval scenario is no longer a surprise; a meaningful share of it is in the price. The rejection scenario, by contrast, is a return to something near the pre-panel level or below, because a third complete response letter on the same question would call the entire regulatory strategy into doubt.

That is the definition of a poor risk-reward: most of the good outcome is priced, and all of the bad outcome is not.

The Options Angle

• Implied volatility in REPL right now is about as high as retail options pricing gets. Buying calls or puts into a PDUFA date two days away means paying the single most expensive premium of the drug's history for the two days when the answer arrives.
• This is the textbook case of being right and losing money. If the FDA approves and the stock gaps up 40%, but you paid for a move of 80%, your calls still lose. Event premium is priced for the full distribution, and the full distribution here is enormous.
• Selling premium is worse. A weekend binary with a two-sided outcome measured in triple digits is exactly the position that ends an account. Do not sell naked options across a PDUFA date.
• A straddle is the structurally honest expression of "I know it moves, I do not know which way." It is also the most expensive it will ever be, right now, which tells you the market has already worked that out.
• If you want exposure, own shares in a size you can watch gap 50% against you and accept there is no way to manage the position over the weekend. That is the only version of this trade with a coherent risk profile.

The Bull Case and the Bear Case

Bull case. A 10-3 vote from independent experts against the FDA's own reviewers is a powerful signal, in an indication where the patients have exhausted alternatives. Approval unlocks a commercial melanoma franchise for a company currently valued as if RP1 may never reach market. The equity value added on Friday, around $600 million, is small relative to what an approved oncology therapy in advanced melanoma is worth.

Bear case. Two complete response letters on the same evidentiary question, from an agency whose scientists publicly restated that objection last week. The advisory panel does not decide. The decision date falls on a weekend, removing any ability to manage risk. And the stock has already repriced most of the good outcome inside a single session.

Our read: no position into August 2. Not because the odds are bad, but because the structure is. You are being asked to take a genuinely uncertain binary, at prices that have already moved 127% in your favour, with a decision landing when the market is shut. The interesting trade in REPL is on August 3, once the answer exists and the volatility has collapsed, in whichever direction that leaves the stock. Wait for the news, then decide. That is the same discipline we applied to SK Hynix's earnings binary, and the reason we did not chase the Korean rebound either.

The One-Line Read

Replimune rose as much as 127% because an FDA advisory panel voted 10-3 that RP1 works in advanced melanoma, overruling the agency's own reviewers six days after their objections knocked 32% off the stock: the drug has now been rejected twice on this same question, the panel only advises, and the actual decision date of August 2 falls on a Sunday, which means the real move happens at Monday's opening auction with nobody able to do anything about it in between.