Results from a Phase 1/2 study show that mRNA-4359, an experimental cancer vaccine, can greatly improve the effectiveness of pembrolizumab (Keytruda) in treating advanced melanoma.
In a small group of patients, the combination achieved an 83% response rate and a 92% disease control rate. Patients responded quickly, with tumor shrinkage seen in about six weeks, and many continued to benefit without disease progression at the time of analysis. Even patients with low PD-L1 levels, who usually respond poorly to immunotherapy, showed strong responses.
mRNA-4359 works by training the immune system to recognize and attack cells expressing PD-L1 and IDO1, helping remove cancer’s ability to hide from immune defenses. All evaluated patients developed targeted T-cell responses against these proteins.
Side effects were generally mild, mainly injection site pain, with no serious treatment-related toxicities reported. Researchers plan larger trials to confirm these early but promising results.