Moderna Presents Promising Early Data for Cancer Antigen Therapy mRNA-4359
Moderna, Inc. (NASDAQ: MRNA) announced promising early clinical and safety data for its investigational cancer antigen therapy, mRNA-4359, in combination with Merck's Keytruda (pembrolizumab). These findings were presented at the 2025 European Society for Medical Oncology (ESMO) Congress, held from October 17-21 in Berlin, Germany. The data suggests potential for mRNA-4359 in treating advanced melanoma patients who have shown resistance to prior checkpoint inhibitor therapies, although the company's stock registered a modest decline following the announcement.
Detailed Clinical Findings from ESMO
The presented data stemmed from a Phase 1/2 study evaluating mRNA-4359 in patients with checkpoint inhibitor-resistant/refractory (CPI-R/R) melanoma. The investigational therapy, an immune-evasion targeted cancer antigen therapy (CAT), is designed to encode epitopes of PD-L1 and IDO1 to stimulate antigen-specific T cell responses. The study included 29 participants with CPI-R/R melanoma who had received at least one prior checkpoint inhibitor therapy. Participants were administered mRNA-4359 at doses of either 400 µg or 1,000 µg intramuscularly every three weeks for up to nine doses.
Across all evaluable patients, the combination therapy demonstrated an objective response rate (ORR) of 24% and a disease control rate (DCR) of 60%. A more pronounced effect was observed in patients with PD-L1+ (TPS≥1%) tumors, where the ORR reached 67% (6 of 9 participants). This subpopulation also showed successful induction of peripheral antigen-specific T cell responses and novel T cell receptor clones. The median duration of response (DOR) had not been reached at the time of the data readout. The safety profile of the combination therapy was reported as manageable, with no new immune-related adverse events.
Market Response and Contextual Factors
Following the announcement of the promising early data, Moderna's stock (MRNA) experienced a decline of approximately 2.54% to 3.5%. This muted, and somewhat negative, market reaction contrasts with the significant rallies seen in other biotech firms on positive clinical news, such as Celcuity's (CELC) over 200% surge on positive Phase III breast cancer trial data, or BeOne Medicines (ONC) receiving Breakthrough Therapy Designation for its BCL2 inhibitor. The market's restraint towards Moderna
