Phase 3 Trial Marks First Success for Personalized mRNA Cancer Therapy in Resected Melanoma

Merck and Moderna announced that the phase 3 INTerpath-001 trial (NCT05933577) met its primary and key secondary efficacy end points, potentially establishing the first individualized mRNA-based cancer therapy as part of adjuvant treatment for patients with completely resected, high-risk melanoma.¹

The investigational regimen combined intismeran autogene (V940; mRNA-4157), an individualized neoantigen therapy, with pembrolizumab (Keytruda; Merck). At a prespecified interim analysis, the combination produced statistically significant and clinically meaningful improvements in recurrence-free survival (RFS) and distant metastasis-free survival (DMFS) compared with pembrolizumab alone.¹

The findings represent the first positive phase 3 readout for an individualized neoantigen therapy and an mRNA-based cancer treatment. However, the companies have not yet disclosed the magnitude of benefit, hazard ratios, event rates, or detailed safety findings. These data are expected to be presented at an upcoming international medical meeting and shared with regulatory authorities.¹

INTerpath-001 Evaluates Treatment After Complete Resection

INTerpath-001 is a global, randomized, double-blind, placebo- and active-comparator-controlled phase 3 trial enrolling approximately 1089 patients with completely resected stage IIB, IIC, III, or IV cutaneous melanoma. Patients had not received prior systemic therapy for their melanoma.¹^,²

The study compared intismeran plus pembrolizumab with placebo plus pembrolizumab in the adjuvant setting. Pembrolizumab is already an established standard of care following complete resection of high-risk melanoma and is FDA approved as adjuvant treatment for patients 12 years or older with stage IIB, IIC, or III disease.³

Although surgery may remove all detectable disease, patients with high-risk melanoma remain vulnerable to recurrence or distant metastasis from residual microscopic cancer. Notably, patients with resected stage IIB or IIC melanoma can face risks of recurrence and melanoma-specific mortality similar to those observed in stage III disease.⁴

The trial will continue to evaluate additional key secondary end points, including overall survival. Investigators reported that the safety profiles of the combination and pembrolizumab were consistent with previously reported findings, with no new safety signals identified.¹

Individualized Therapy Targets Each Tumor’s Mutations

Intismeran differs from preventive vaccines used against infectious diseases. The investigational treatment is created specifically for an individual patient using the unique mutational profile of that patient’s tumor.

Following tumor sequencing, selected mutations are encoded into an mRNA therapy intended to stimulate T cells against as many as 34 patient-specific neoantigens. Pembrolizumab blocks the programmed death receptor-1 pathway, helping restore antitumor immune activity. The therapeutic strategy therefore combines generation of a highly individualized immune response with checkpoint inhibition intended to sustain the immune system’s ability to recognize and attack malignant cells.¹,⁵

If approved, this model would introduce operational considerations extending beyond those associated with conventional off-the-shelf oncology therapies. Treatment would require coordination among surgical teams, pathology and genomic laboratories, manufacturers, oncology practices, infusion centers, and pharmacy departments. Adequate tumor-tissue acquisition, chain-of-custody processes, manufacturing turnaround time, treatment scheduling, and management of pembrolizumab-related immune-mediated toxicities could all affect implementation.

Phase 2b Findings Supported Phase 3 Development

The phase 3 success is supported by mature findings from the randomized phase 2b KEYNOTE-942 trial (NCT03897881). At a median follow-up of approximately 5 years, intismeran plus pembrolizumab reduced the risk of recurrence or death by 49% compared with pembrolizumab alone (HR, 0.51; 95% CI, 0.294-0.887). The combination also reduced the risk of distant metastasis or death by 59% (HR, 0.411; 95% CI, 0.200-0.843).⁵

In that analysis, commonly reported adverse events attributed to intismeran included fatigue, injection-site pain, and chills. Most were grade 1 or 2, and the addition of intismeran did not appear to increase immune-related adverse events relative to pembrolizumab alone.⁵

The phase 3 topline results provide important validation, but several questions remain. Detailed results will be necessary to determine the absolute RFS and DMFS benefits, outcomes across disease stages and biomarker subgroups, treatment discontinuation rates, manufacturing feasibility, and the full toxicity profile. Overall survival data also remain immature.

Beyond melanoma, intismeran is being studied in a broader development program involving non–small cell lung cancer, bladder cancer, renal cell carcinoma, and other disease settings.¹ If the INTerpath-001 findings support regulatory approval, the trial may represent not only an advance in adjuvant melanoma therapy but also the first clinical validation of a scalable, individualized mRNA treatment platform for cancer.

References

1. Merck and Moderna announce phase 3 INTerpath-001 trial of intismeran autogene plus Keytruda met endpoints of recurrence-free survival and distant metastasis-free survival in patients with completely resected stage IIB-IV melanoma. News release. Merck; August 19, 2026. Accessed August 19, 2026. https://www.merck.com/news/merck-and-moderna-announce-phase-3-interpath-001-trial-of-intismeran-autogene-plus-keytruda-met-endpoints-of-recurrence-free-survival-rfs-and-distant-metastasis-free-survival-dmfs-in-patient/

2. A clinical study of intismeran autogene (V940) plus pembrolizumab in people with high-risk melanoma (V940-001). ClinicalTrials.gov. Updated September 24, 2025. Accessed August 19, 2026. https://clinicaltrials.gov/study/NCT05933577

3. Keytruda Qlex (pembrolizumab and berahyaluronidase alfa-pmph) prescribing information. Merck; 2026. Accessed August 19, 2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/761467s007lbl.pdf

4. PDQ Adult Treatment Editorial Board. Melanoma Treatment (PDQ®): Health Professional Version. In: PDQ Cancer Information Summaries. Bethesda (MD): National Cancer Institute (US); May 2, 2025.

5. Khattak A, Carlino MS, Meniawy T, et al. Intismeran Autogene Plus Pembrolizumab Versus Pembrolizumab Alone in High-Risk Resected Melanoma: 5-Year Update of the Randomized Phase IIb KEYNOTE-942 Study. J Clin Oncol. Published online June 1, 2026. doi:10.1200/JCO-26-00835