Replimune · RP1 · Jul 2025 – Aug 2026
What happened to the confirmatory trial Replimune said would not be viable?
Replimune said three times that RP1 would not be viable without accelerated approval. Continued approval may now depend on that Phase 3 trial, whose control arm has been under discussion since the first letter.
EphemerisX Research · Published · 7 source documents · 1 min read
Short answer
From July 2025 to April 2026 the company said RP1's development, including the Phase 3 trial, would not be viable without accelerated approval. The approval in August 2026 may depend on that trial. Its control arm was questioned in the first letter, discussed at the Type A meeting, and, according to the 10-K, revisited in the second letter.
What the evidence shows
July 2025: without which the development of RP1 for advanced cancer patients with limited options will not be viable
8-K · Jul 22, 2025. September 2025: continuation of the RP1 program in advanced melanoma, including the phase 3 confirmatory trial, will not be viable
8-K · Sep 4, 2025. April 2026: As we previously communicated, without timely accelerated approval, the development of RP1 will not be viable
8-K · Apr 13, 2026.
On the control arm, the first FDA letter said the design may not isolate the contribution of vusolimogene oderparepvec due to the inclusion of single-agent chemotherapy options
FDA · Jul 21, 2025 · p. 2. The company's 8-K says the agency later acknowledged that randomizing patients to an anti-PD1 only arm in the confirmatory study was not feasible
8-K · Apr 13, 2026. Its 10-K says the Type A minutes stated that nivolumab with relatlimab may be an acceptable comparator
10-K · Jun 29, 2026, and that in the second CRL we believe the FDA reverted on its position
10-K · Jun 29, 2026.
The second letter invited the company to request a meeting to discuss if the ongoing RP1-104 study with a revised study protocol and statistical analysis plan can address the deficiencies outlined
FDA · Apr 10, 2026 · p. 7. The 10-K: We continue to enroll patients in the I-3 trial
10-K · Jun 29, 2026.
The approval 8-K: Continued approval for this indication may be contingent on verification of clinical benefit in a confirmatory trial(s)
8-K · Aug 7, 2026, and a confirmatory Phase 3 trial, IGNYTE-3, is ongoing
8-K · Aug 7, 2026.
The FDA letters name the Phase 3 trial RP1-104; the company's filings call their Phase 3 trial IGNYTE-3. Both describe a randomized trial against physician's choice of treatment; no document in this record uses both names.
Follow the thread
- What did the FDA's first letter object to?Chemotherapy in the Phase 3 control arm
- How did Replimune describe the first letter?“Will not be viable”
- What was said at the September 2025 Type A meeting?The control arm named in the minutes
- What happened inside Replimune after the second letter?“Will not be viable,” then job cuts
This investigation connects to
- How did two programs move forward after repeat FDA letters without running a new trial?Cross-investigation · Comparable evidence · with Outlook Therapeutics
- When is one trial enough? How the FDA weighed the evidence in three programsCross-investigation · Comparable evidence · with Aldeyra Therapeutics, Outlook Therapeutics
The documents, by date
The passages quoted
FDA Complete Response Letter, July 21, 2025 · page 2
The study design may not isolate the contribution of vusolimogene oderparepvec due to the inclusion of single-agent chemotherapy options in the investigator’s choice control arm.Open at the source →
Replimune Form 8-K, filed July 22, 2025
Replimune plans to urgently interact with the FDA to find a path forward for the timely accelerated approval of RP1 without which the development of RP1 for advanced cancer patients with limited options will not be viable.Open at the source →
Replimune Form 8-K, filed September 4, 2025
We remain steadfastly committed to patient access while we work with the FDA to secure regulatory approval for RP1, however, without accelerated approval based on the current application, continuation of the RP1 program in advanced melanoma, including the phase 3 confirmatory trial, will not be viable.”Open at the source →
FDA Complete Response Letter, April 10, 2026 · page 7
You may request a meeting to discuss if the ongoing RP1-104 study with a revised study protocol and statistical analysis plan can address the deficiencies outlined or propose a new clinical study.Open at the source →
Replimune Form 8-K, filed April 13, 2026
After testimony from melanoma experts, the agency did not raise further concerns about the heterogeneity of the patient population in IGNYTE and acknowledged that randomizing patients to an anti-PD1 only arm in the confirmatory study was not feasible.Open at the source →
Replimune Form 8-K, filed April 13, 2026
As we previously communicated, without timely accelerated approval, the development of RP1 will not be viable. We are devastated for our committed employees who have worked tirelessly for patients but at this point we have no choice but to eliminate jobs, including substantially scaling back our U.S. based manufacturing operations.Open at the source →
Replimune Form 10-K, filed June 29, 2026
In the September 2025 type A meeting minutes following the initial CRL, the FDA stated a control arm of nivolumab in combination with relatlimab (Opdualag (R) ) may be an acceptable comparator for the I-3 randomized controlled trial. However, in the second CRL we believe the FDA reverted on its position in the September 2025 type A meeting. Following the recent collaborative communications with the FDA we plan to continue working with the FDA on a path forward for the I-3 trial. We continue to enroll patients in the I-3 trial.Open at the source →
Replimune Form 8-K, filed August 7, 2026
Continued approval for this indication may be contingent on verification of clinical benefit in a confirmatory trial(s).Open at the source →
Replimune Form 8-K, filed August 7, 2026
To verify the clinical benefit of TUDRIQEV, a confirmatory Phase 3 trial, IGNYTE-3, is ongoing and assessing TUDRIQEV in combination with nivolumab (NCT06264180).Open at the source →