Merck and Moderna Plan Wider Tests of Personalized mRNA Cancer Vaccine

This article is based on STAT's report from its Boston summit. The underlying trial results were not reviewed, and the paper itself was not read.

According to STAT, Merck and Moderna announced in August that a large Phase 3 trial of their personalized mRNA vaccine, known as intismeran autogene, significantly delayed both cancer recurrence and the spread of the disease in melanoma patients. STAT's report gives no figures for how large the benefit was. It says the companies are preparing to file the vaccine for approval.

The vaccine is used together with Keytruda, Merck's immunotherapy drug. Keytruda helps the immune system attack cancer. According to STAT, each vaccine is made by examining an individual patient's tumor. An algorithm then picks up to 34 mutated proteins from it. The aim is to show those proteins to the immune system as a "wanted sign," in STAT's wording, so it can recognize and attack cancer cells that carry them.

The setting matters. STAT reports that the work so far has focused on use after surgery, as an add-on treatment, for melanoma patients whose visible tumors have already been removed. Some melanomas return aggressively after surgery, which is why doctors look for added protection at that stage.

STAT describes one patient, Gary Keblish, a public school teacher diagnosed with melanoma in 2019. After surgery, his doctors referred him to an early trial of the vaccine. Speaking by video at the summit, he compared the journey, in all its physical and emotional turbulence, to a trip on the Magic School Bus, quoting the line "Seatbelts, everyone!" He is still teaching, and STAT says he is glad he went. One patient's account is not evidence of how the vaccine works for others.

Next, the companies plan to test it in other cancers. According to STAT, trials are already running after surgery in lung, kidney and bladder cancer. Small tests are underway in adjuvant, meaning post-surgery, pancreatic and gastric cancer. Merck R&D chief Dean Li also floated using the vaccine in patients whose metastatic tumors have already been shrunk by other treatments.

Li said the companies are choosing places where Keytruda is known to work best. He contrasted this with "other people" who have gone after cold or metastatic tumors. STAT notes that Keytruda works less well in cold tumors, and reads Li's remark as an apparent reference to rival BioNTech, which has had some promising early data and some notable failures.

Moderna President Stephen Hoge was candid about the road ahead. "We have a lot of exploring to do and need to prioritize where we explore," he said. He also pointed to a longer-term goal of using immunotherapy earlier, to "intercept cancer" before it reaches stage 3 or 4. STAT describes that early-stage work as just beginning.

For now, the clear message is limited. Benefit has been reported in melanoma after surgery. Whether it extends to other cancers is unknown. The algorithm is imperfect, STAT notes, and the companies hope data from several thousand people in the Phase 3 program will help improve it.

What to watch next

Whether regulators accept the melanoma filing, and whether the lung, kidney and bladder trials show similar benefit.

Yale Study: Single-Clock Biological Age Reversal Claims Failed Multi-Clock Checks Merck and Moderna Plan Wider Tests of Personalized mRNA Cancer Vaccine 35-Year Study Links Cannabis Use to More Fragmented Sleep in Midlife Ovaries Keep Changing for Decades After Menopause, Northwestern-Buck Study Finds Large NIH Study Finds No Overall Ultra-Processed Food Link to Colorectal Cancer