Melanoma Vaccine Paired With Keytruda Keeps Cancer Away Longer, Trial Data Shows

Moderna and Merck announced Aug. 19 that a large clinical trial found patients with high-risk melanoma, a type of skin cancer, given an experimental cancer vaccine alongside the approved immunotherapy drug Keytruda were cancer-free for longer than patients who received Keytruda alone. The companies have not yet released the trial data. Neither the vaccine nor the combination has been approved by regulators; the companies say that if approved, the personalized approach could become a new treatment option for patients. An earlier trial of the same combination had shown it cut the risk of the cancer returning or death in half compared with Keytruda alone.

The vaccine, called intismeran, uses mRNA — the same technology used in COVID-19 vaccines and a recently approved flu shot — to deliver genetic material from a patient's own tumor. It is a therapeutic vaccine, meaning it does not prevent melanoma from developing; instead, it trains the immune system to recognize a patient's specific tumor cells using pieces of proteins called neoantigens. Because each vaccine is built from an individual patient's cancer cells, researchers can create a custom treatment for each person.

Keytruda is a checkpoint inhibitor already approved to treat cancers including lung, colon and breast cancer. Leslie Fecher, a medical oncologist at the University of Michigan who was not involved in developing the treatment, described Keytruda as blocking PD-1, a protein that otherwise acts as a brake on the immune system. Together, the vaccine and Keytruda aim to get the body to attack cancer cells left behind after a tumor is surgically removed.

The trial included patients whose melanoma had been surgically removed, ranging from high-risk stage II, where the tumor is still confined to the skin, through stage III, where it has spread to nearby lymph nodes, to stage IV, where a single tumor had spread to another organ such as the lung and was then removed. Skin cancer is the most common cancer in the United States, and melanoma causes most skin cancer deaths; more than 100,000 people are diagnosed with melanoma each year and about 8,500 die from it, according to the American Cancer Society.