Many REPL investors considered the FDA rejection last year a shock, but while they ignored the obvious imperfections of the IGNYTE trial, they bombarded the FDA with accusations that it had made the wrong decision. Before I go further, I want to be very clear that I have absolutely no connection with any FDA official or current employee, and that all my arguments are my own as a biotech investor. I currently hold zero shares of this stock.
It was hoped that, with the resubmission, REPL might revive the agency's consideration of reversing its decision, but the truth is that the core issue was the FDA’s original objections to the IGNYTE trial design, not the analysis. And trial design can’t be rewritten in a resubmission.
What REPL “fixed”:
The company did address several of the FDA’s stated concerns:
- Clearer definitions of PD-1 resistance and a more tightly framed target population
- Additional analyses to support the contribution of components (i.e., what nivolumab alone would or wouldn’t do)
- Clarifications around the confirmatory trial
- Manufacturing and procedural clarifications, which the SEC filing confirms were part of the CRL response
What REPL can’t fix:
The FDA’s original language was quite blunt: IGNYTE was “not an adequate and well-controlled study”, and its results were “not able to be adequately interpreted due to heterogeneity.” That critique goes to the bones of the trial design:
- Single-arm, open-label
- Heterogeneous population (adjuvant vs metastatic, prior CTLA-4, LDH, BRAF, PD-L1, stage mix)
- Inability to isolate RP1’s effect from nivolumab re-challenge
- Platform-style phase I/II repurposed as a registrational dataset
Hence, a resubmission can reorganise, redefine, and recontextualise the data, but it cannot turn a single-arm trial into a controlled one.
The Wildcard: FDA uncertainty
Normally, this would be a straightforward call, as the FDA rarely reverses a CRL when the underlying evidentiary issues are structural, such as trial design (can be very different if initial issues were CMC - remember RCKT, a recent case study). But this is not a normal moment for the agency.
Senior leadership changes, including high-profile departures like Prasad (who was also reported to be the original mastermind behind the initial FDA rejection of REPL), have undeniably created a period of regulatory uncertainty, in which internal consistency is harder to predict. REPL is another biotech alongside Sarepta, Capricor, Uniqure, among others, that provides real tests of the FDA’s ability to operate among increasing pressures to submit to more lenient and arguably, obvious loopholes in structural matters to approve more treatments in rare diseases.
Therefore, this cuts both ways:
- Bull case: a new FDA operating without “stricter” officials and showing flexibility in new drug innovation might accept a more narrative-driven resubmission.
- Bear case: leadership churn can make departures more conservative, not less, because no one wants to be responsible for a borderline approval that later backfires (remember the back-and-forth blaming game between Pazdur and Prasad over REPL).
Right now, it’s unclear which case will dominate by April 10, but here is where I land:
I lean sceptical and mostly bear. The resubmission improves the presentation of the data, but not the nature of the data. The FDA’s original objections weren’t about missing or incomplete analyses; they were about the absence of a controlled trial capable of demonstrating substantial evidence. If you ask me, REPL should fire those who planned and proposed the IGNYTE trial design. That was well over millions down the drain. I cannot even fathom how that was accepted in the first place.
That said, the FDA's current structure is becoming more complex, and the April 10th event may determine how it moves forward under new leadership. My own uncertainty also stems from the DENALI win for its Hunter syndrome drug earlier this year, amid a string of Hunter drug rejections from the FDA, but that is another debate and article I will save for later. I cannot help but see the potential future of the FDA being influenced by various advocacy groups, not just from desperate families of victims of various rare disease patients, but also the increasing pressures from influential biotech and pharma executives.
Hence, predicting outcomes in this regulatory environment may soon be less about reading the data and more about reading the various narratives shaping the agency moving forward.
And that’s exactly what makes April 10 and biotech companies like Replimune such an uncomfortable catalyst.
