On April 18, 2026 Moderna, Inc. (NASDAQ:MRNA) reported that the Company will present data from a Phase 1/2 study of mRNA-4359, an investigational cancer antigen therapy, at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting in San Diego, CA, on April 17-22, 2026. The presentation reports safety, efficacy and translational data from a Phase 2 dose-expansion cohort of the Phase 1/2 study (NCT05533697), which evaluated mRNA-4359 + pembrolizumab as a first-line therapy in patients with locally advanced or metastatic melanoma.

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Among 12 participants, mRNA-4359 + pembrolizumab resulted in an overall response rate (ORR) of 83% (95% CI: 52%-98%), with two patients achieving a complete response and eight achieving a partial response, as well as a disease control rate (DCR) of 92% (95% CI: 62%-100%). The median time to response was six weeks (range, 5.6-24.0). Responses occurred across baseline tumor PD-L1 expression categories, with an ORR of 88% (95%CI: 47%-100%) among patients with PD-L1+ (TPS≥1%) tumors, and 67% (95%CI: 9%-99%) among patients with PD-L1- (TPS<1%) tumors. Consistent with mRNA-4359’s mechanistic rationale, antigen-specific T-cell responses and novel expanded T-cell receptor (TCR) clonality was observed in all patients (n=7) with evaluable samples. mRNA-4359 + pembrolizumab demonstrated a manageable safety profile, with no new immune-related adverse events (AEs).

"This study evaluating mRNA-4359 + pembrolizumab as a first-line treatment option reflects our ambition to demonstrate the potential of mRNA technology throughout a cancer patient’s journey. While conducted among a small patient population, we are encouraged by the high response rates and mechanistic translational results," said David Berman, M.D., Ph.D., Chief Development Officer of Moderna. "We look forward to further evaluating the potential of mRNA-4359 in patients with melanoma."

"This early data supports the potential activity of the mRNA-4359 + pembrolizumab combination, with promising anti-tumor activity," Dr. Pavlina Spiliopoulou, School of Cancer Sciences, University of Glasgow, the abstract’s lead author and presenter. "The consistent activation of antigen-specific T-cell responses provides important early evidence that mRNA technology could be used to help direct the immune system against melanoma in a multi-targeted manner."

This presentation builds on promising early data presented at the 2025 European Society for Medical Oncology Congress, in which mRNA-4359 + pembrolizumab achieved an ORR of 24% and DCR of 60% among 29 evaluable patients with checkpoint inhibitor-resistant/refractory (CPI-R/R) melanoma. Among those with response-evaluable disease and PD-L1+ (TPS≥1%) tumors, the ORR was 67%.

The U.S. FDA has granted Fast Track designation for mRNA-4359 in combination with pembrolizumab for the treatment of CPI refractory unresectable or metastatic melanoma with PD-L1+ (TPS>1%). Fast Track is designed to facilitate the development and expedite the review of therapies and vaccines for serious conditions and that fill an unmet medical need. Programs with Fast Track designation may benefit from early and frequent communication with the FDA, in addition to a rolling submission of the marketing application.

The details of the presentation are as follows:

Abstract Presentation #CT106: First-Line mRNA-4359 Plus Pembrolizumab (Pembro) in Locally Advanced or Metastatic Melanoma: Results from the Phase 1/2 mRNA-4359-P101 Study

Session Title: Clinical Trials Plenary 3: Cellular Therapies and Complex Immunotherapies

Session Date/Time: Monday, April 20, 10:15AM – 12:15PM PT

Presenter: Dr. Pavlina Spiliopoulou, School of Cancer Sciences, University of Glasgow, UK

About mRNA-4359

mRNA-4359 is an investigational, immune-evasion targeted cancer antigen therapy that encodes broad epitopes of PD-L1 and IDO1. With its dual mechanism of action, it is designed to elicit antigen-specific T-cell responses to simultaneously: (1) kill tumor cells expressing PD-L1 and IDO1, and (2) deplete immunosuppressive cells that shield the tumor from attack. This is hypothesized to rebalance the tumor microenvironment into an immune-permissive state, supporting sustained and durable anti-tumor activity with a manageable safety profile.

(Press release, Moderna Therapeutics, APR 18, 2026, https://feeds.issuerdirect.com/news-release.html?newsid=8054079664924385&symbol=MRNA [SID1234664479])