mRNA Cancer Vaccines and Neoantigens: What Did the KEYNOTE-942 Trial Show in Melanoma?

Summary: mRNA-4157 (V940) is an experimental mRNA cancer vaccine developed by Moderna and Merck that targets patient-specific neoantigens. Its combination with pembrolizumab (Keytruda) yielded statistically significant results in the Phase 2b KEYNOTE-942 trial conducted in patients with high-risk resected melanoma, reducing the risk of recurrence and distant metastasis. This approach has not yet been approved by the FDA; multicenter Phase 3 trials (the INTerpath program) are currently ongoing.

What Is a Neoantigen, and Why Is It Important?

Neoantigens are protein fragments that arise from mutations specific to cancer cells and are not found in normal cells. The immune system can recognize these structures as “foreign.” Patient-specific neoantigens can be identified through RNA-seq analysis of the tumor; this information is used to design a synthetic mRNA vaccine tailored to that specific patient.

KEYNOTE-942 (mRNA-4157-P201) Study

In this Phase 2b, randomized study, patients with completely resected, high-risk stage III/IV melanoma were treated with mRNA-4157/V940 in the adjuvant (post-surgical) setting, either in combination with pembrolizumab or with pembrolizumab alone. The combination arm demonstrated a statistically significant reduction in the risk of recurrence or death compared to pembrolizumab alone; subsequent analyses also reported a significant reduction in the risk of distant metastasis. Based on these results, the U.S. FDA and the European Medicines Agency (EMA) have granted this combination Breakthrough Therapy designation and PRIME program support, respectively—which does not imply approval, but means that clinical development can be accelerated.

Phase 3 Process: The INTerpath Program

Following positive Phase 2b data, Merck and Moderna launched a broad Phase 3 clinical development program called INTerpath. Under this program:

• INTerpath-001: Adjuvant therapy in high-risk resected melanoma.
• INTerpath-002: Adjuvant therapy in resected non-small cell lung cancer (NSCLC).
• INTerpath-007: Neoadjuvant/adjuvant use in resectable cutaneous squamous cell carcinoma.
• INTerpath-009: Adjuvant use in patients with resected NSCLC who did not achieve a complete pathological response to neoadjuvant therapy.

These studies are still ongoing; this approach cannot become the standard of care until the results are finalized.

What Does This Mean for Potential Patients?

mRNA neoantigen vaccines are one of the most actively researched areas in science, particularly for tumors with a high mutation burden (melanoma, NSCLC). However, at this time:

• This approach is considered experimental and is not part of routine clinical practice.
• Results are specific to the patient groups participating in the study; the same response cannot be expected in every patient.
• If an evaluation of this nature is being conducted at any center, the patient must be clearly informed of the study’s phase and approval status.

Frequently Asked Questions

Is mRNA-4157/V940 an approved treatment?

No. It is currently in the research (Phase 3) stage and has not been approved as a routine treatment in any country.

Is this vaccine the same as the COVID-19 mRNA vaccines?

The underlying technology is similar (mRNA that instructs cells to produce a protein), but the content is entirely different and is tailored specifically for each patient.

Is it being studied only for melanoma?

No, Phase 2/3 studies are also ongoing for various tumor types, including NSCLC and cutaneous squamous cell carcinoma.

This content is for informational purposes only; it does not diagnose, recommend treatment, or guarantee results. Be sure to consult a doctor for a personalized evaluation.