Individualized mRNA Therapy Cut Melanoma Recurrence 42 Percent in Phase 3. The Benefit Started After Six Months.
In INTerpath-001, adding intismeran autogene to adjuvant pembrolizumab lowered the risk of recurrence or death in resected stage IIB-IV melanoma (HR 0.58). Overall survival is immature, and the curves did not separate until after month six.
Idea in Brief
The News
Full phase 3 INTerpath-001 results, presented Oct. 24 at the European Society for Medical Oncology Congress, showed a recurrence-free survival hazard ratio of 0.58 for intismeran autogene plus pembrolizumab versus pembrolizumab alone.
The Evidence
Two-year recurrence-free survival was 82.2 percent versus 70.0 percent in 1,137 patients with completely resected stage IIB-IV melanoma, at a median follow-up of 24.6 months.
The Caveats
Overall survival is immature (HR 0.77, not significant), there was no separation in the first six months, and the therapy is not approved.
Adding intismeran autogene, an individualized mRNA neoantigen therapy, to adjuvant pembrolizumab cut the risk of melanoma recurrence or death by 42 percent (HR 0.58) in the phase 3 INTerpath-001 trial, according to full results presented Oct. 24.
Georgina V. Long, M.D., Ph.D., of Melanoma Institute Australia presented the data as late-breaking abstract LBA1 in Presidential Symposium I at the European Society for Medical Oncology (ESMO) Congress in Madrid, Targeted Oncology reported. Merck and Moderna, which are developing the therapy, said in their Oct. 22 announcement that the results have been accepted for publication in the New England Journal of Medicine. Our preview of what to look for ran Oct. 22.
What did the trial show?
The combination met its primary endpoint of recurrence-free survival and its key secondary endpoint of distant metastasis-free survival. INTerpath-001 is a double-blind trial that randomized 1,137 patients with completely resected stage IIB to IV cutaneous melanoma 2:1 to intismeran plus pembrolizumab or placebo plus pembrolizumab. Intismeran was given at 1 mg every three weeks for up to nine doses, and pembrolizumab at 400 mg every six weeks for up to nine cycles.
At a median follow-up of 24.6 months, the recurrence-free survival HR was 0.58 (95% CI, 0.45-0.75; two-sided P<.001). Two-year recurrence-free survival was 82.2 percent versus 70.0 percent, and median recurrence-free survival was not reached in either arm, according to the companies.
Distant metastasis-free survival had an HR of 0.62 (95% CI, 0.45-0.85; P=.002), with two-year rates of 88.5 percent versus 80.2 percent. A modified intent-to-treat sensitivity analysis, which excluded participants who did not receive at least one dose of intismeran or placebo as planned, gave a recurrence-free survival HR of 0.51 (95% CI, 0.39-0.67).
The benefit held across stage groups. CancerNetwork reported recurrence-free survival HRs of 0.60 (95% CI, 0.41-0.88) in stage IIB to IIIB disease and 0.57 (95% CI, 0.41-0.79) in stage IIIC to IV. Confidence intervals crossed 1 in several smaller subgroups.
Why does the six-month pattern matter?
The curves did not separate until after month six. In a prespecified piecewise analysis, the recurrence-free survival HR was 0.99 (95% CI, 0.66-1.49) from months 0 to 6 and 0.42 (95% CI, 0.30-0.58) afterward; distant metastasis-free survival followed the same pattern (HR 1.01, then 0.50).
The presented data do not explain the delay, and CancerNetwork noted only that the benefit emerged after the first six months. Whatever the mechanism, in practice it means early recurrences should not be expected to fall with the added therapy.
The primary endpoint is clear. Survival is not yet, and the first six months on the combination looked the same as pembrolizumab alone.
Clinical Pearls
- Primary endpoint: recurrence-free survival, HR 0.58 (95% CI, 0.45-0.75; P<.001).
- Distant metastasis-free survival, a key secondary endpoint, had an HR of 0.62 (95% CI, 0.45-0.85; P=.002).
- Piecewise analysis: HR 0.99 from months 0 to 6, and 0.42 beyond month 6.
- Overall survival HR was 0.77 (95% CI, 0.45-1.31; P=.33) and did not meet its prespecified boundary.
- Grade 3-5 treatment-related adverse events were 14.2 percent with the combination and 13.4 percent with pembrolizumab alone.
- Pyrexia (52.2 percent) and injection site pain (51.0 percent) were the most common events in the combination arm.
What about survival and safety?
Overall survival is immature. The HR was 0.77 (95% CI, 0.45-1.31; P=.33) and did not reach the prespecified significance boundary, Targeted Oncology reported; the companies describe a favorable trend and say follow-up continues.
Grade 3 to 5 treatment-related adverse events occurred in 14.2 percent of patients on the combination and 13.4 percent on pembrolizumab alone. Treatment-related events led to discontinuation of any study drug in 14.0 percent versus 8.7 percent. Pyrexia (52.2 percent versus 8.2 percent), injection site pain (51.0 percent versus 9.5 percent) and influenza-like illness (25.4 percent versus 9.2 percent) were more common with the combination and were described by investigators as low grade and transient. Immune-mediated events were similar (36.0 percent versus 34.7 percent), and the two treatment-related deaths in the combination arm were attributed to pembrolizumab, according to CancerNetwork.
How is the result being read?
Dean Y. Li, president of Merck Research Laboratories, called the result "one of the most significant advances in melanoma treatment since the advent of immunotherapy" in the companies' announcement. The market response was cooler. After the data leaked on Oct. 22, Moderna shares fell 21 percent, BioSpace reported. The phase 2 study had shown an HR of 0.51, and RBC Capital Markets said investors had hoped for 0.50 to 0.59, putting 0.58 "at the low end of expectations." RBC still expects the result to clear regulators, according to BioSpace.
BMO Capital Markets raised a design question, according to BioSpace: pembrolizumab given before surgery reached a similar hazard ratio in earlier phase 2 trials, raising "questions on the need for added intismeran therapy." RBC made a related point about neoadjuvant immunotherapy, "which produces similar efficacy at potentially much less cost." INTerpath-001 compared against adjuvant pembrolizumab only.
What it means in clinic
Intismeran autogene is not approved, and no submission date has been announced; the companies say they are engaging with regulatory authorities, and BioSpace reported an FDA approval could come in 2027. Until then, access is through trials.
Patients with resected high-risk melanoma who read the headlines may ask about it this week. The accurate answer is that it lowered recurrence when added to standard adjuvant pembrolizumab, that survival benefit is not yet shown and that it is not available outside trials. For melanoma teams, the practical next step is the NEJM paper, which should give the full subgroup and stage data needed to judge which patients the result applies to.
Reported, fact-checked and edited by The Script Pad's editorial staff. See How we use AI.
This article is for professional education and does not replace clinical judgment. Treatment decisions should be based on the individual patient and current guidelines.
