On October 12, 2025 Moderna, Inc. (NASDAQ:MRNA) reported that clinical, safety and translational data from its Phase 1/2 study evaluating mRNA-4359 in combination with pembrolizumab in checkpoint inhibitor-resistant/refractory(CPI-R/R) melanoma patients will be presented at the 2025 European Society for Medical Oncology (ESMO) (Free ESMO Whitepaper) Congress, October 17-21, 2025, in Berlin, Germany (Press release, Moderna Therapeutics, OCT 12, 2025, https://feeds.issuerdirect.com/news-release.html?newsid=5823943357532273&symbol=MRNA [SID1234656588]). mRNA-4359 is an investigational immune-evasion targeted cancer antigen therapy (CAT) that encodes epitopes of two common immune escape pathways, PD-L1 and IDO1, to elicit antigen-specific T cell responses that may directly kill tumor cells and deplete tumor suppressor cells.

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The presentation includes data from 29 participants with CPI-R/R melanoma who have had ≥1 prior checkpoint inhibitor (CPI) therapy. Participants received the combination therapy at 400 µg (n=14) or 1,000 µg (n=15), given intramuscularly every three weeks for up to nine doses. Across all evaluable patients, the objective response rate (ORR) was 24% and disease control rate (DCR), or the combination of patients achieving tumor response and stable disease, was 60%. Among those with response-evaluable disease and PD-L1+ (TPS≥1%) tumors, the ORR was 67% (6 of 9 participants), with treatment successfully inducing peripheral antigen-specific T cell responses and novel T cell receptor clones. The median duration of response (DOR) was not reached. The improved efficacy in PD-L1+ patients supports PD-L1 as a potential predictive biomarker in this high unmet need population.

"While early, today’s mRNA-4359 melanoma data in highly CPI-refractory metastatic patients are unique in the field and incredibly promising for future development options. We are encouraged by its potential to address such a high unmet need for many patients," said Dr. Kyle Holen, Head of Development, Therapeutics and Oncology, Moderna. "Where other checkpoint inhibitors restore non-specific T cell activity, mRNA-4359 encodes two critical immune escape pathways to help generate new, target-directed T cells. This could enable broader and more durable immune responses for patients who have not had success with prior lines of therapy. We are proud to present these data and to demonstrate the role our mRNA-based therapies could play in transforming the lives of those affected by cancer."

mRNA-4359 in combination with pembrolizumab demonstrated a consistently manageable safety profile, with no new immune-related adverse events (AEs). mRNA-4359 continues to be evaluated in an ongoing phase 1/2 study (NCT05533697) as a monotherapy and in combination with pembrolizumab in patients with advanced melanoma and non-small cell lung cancer (NSCLC).

"After failing to respond to first-line immunotherapy, existing options for PD-L1+ patients are limited, underscoring a clear need for effective, tolerable therapies," said Prof. David J. Pinato, Clinical Professor of Experimental Cancer Therapeutics at Imperial College London and Consultant Medical Oncologist at Imperial College Healthcare NHS Trust and lead author and presenter of the abstract. "mRNA-4359 has the potential to rebalance the tumor microenvironment to overcome this immunotherapy resistance. These data are encouraging as we continue to investigate the potential of mRNA-4359."

The details of the presentation are as follows:

Mini Oral Presentation #1515MO: Clinical Outcomes and PD-L1 Expression Analyses from a Trial of mRNA-4359 Plus Pembrolizumab in Checkpoint Inhibitor-Resistant/Refractory (CPI-R/R) Melanoma

Time: Friday, October 17, 2025, 2:00 – 3:30 PM CET

Location: Nuremberg Auditorium – Hall 5.2

Presenter: David J. Pinato

Moderna’s Oncology Investor & Analyst Event

Moderna will host a live webcast for investors and analysts on Friday, October 17, 2025, at 6:00 PM CET (12:00 PM ET), which will be available under "Events and Presentations" in the Investors section of the Moderna website at investors.modernatx.com. A replay of the webcast will be archived on Moderna’s website for at least 30 days following the presentation.

About mRNA-4359

mRNA-4359 is an immune-evasion targeted cancer antigen therapy that encodes broad epitopes of PD-L1 and IDO1. With its dual mechanism of action, it elicits 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.