The melanoma vaccine in this week’s headlines will not stop anyone from getting skin cancer. It is a personalized mRNA treatment, made from each patient’s own tumor. It’s for people whose high-risk melanoma a surgeon has already removed. Added to the drug Keytruda, it cut the risk of relapse or death by 42% in a 1,137-patient trial.
That result comes from Merck’s October 22 release on the Phase 3 INTerpath-001 trial, run with Moderna. It matters to patients whose melanoma has already reached stage IIB or beyond. For everyone else, the useful advice is still the old one: find melanoma early.
A custom drug built from one person’s tumor
The drug’s name is intismeran autogene, also known as V940 or mRNA-4157. Doctors sequence the DNA of the tumor a surgeon took out and compare it with the patient’s normal DNA. That comparison picks out mutations found only in the cancer, called neoantigens.
Moderna then makes a single mRNA molecule coding for up to 34 of them, according to Merck. After the injection, the body makes those mutant protein fragments and the immune system learns to hunt cells that carry them. Keytruda, a checkpoint inhibitor, takes the brakes off those immune cells.
So the word “vaccine” describes how it trains the immune system, not what it does for the public. No two patients get the same product. TIME reported that Moderna can build each patient’s version within weeks. The companies haven’t published an exact turnaround.
In the trial, patients got up to nine doses of intismeran, three weeks apart. They also got Keytruda every six weeks for about a year. The comparison group got Keytruda and a placebo injection.
What a 42% lower risk means in real numbers
The 42% comes from a hazard ratio of 0.58. A hazard ratio compares how often bad events happen in each group over the whole follow-up, which here ran a median of 24.6 months.
That gives you the relative difference. It doesn’t tell you how many people that difference spares.
Merck’s release also gives the absolute rates, which are more useful. At two years, 82.2% of patients on the combination were alive with no recurrence, against 70.0% on Keytruda alone. We turned those into groups of 100.
| Out of 100 patients, at two years | Intismeran + Keytruda | Keytruda alone |
|---|---|---|
| Cancer came back, or died | about 18 | about 30 |
| Cancer spread to distant organs, or died | about 12 | about 20 |
That works out to about 12 fewer recurrences or deaths per 100 patients treated, or roughly one avoided for every eight. These are trial estimates at a single time point, and they could shift as follow-up continues.
The timing matters too.
In the first six months, while patients were still getting doses, the two groups fared the same (hazard ratio 0.99). After six months, a pre-specified sensitivity analysis showed a 58% lower risk.
Moderna’s chief development officer, David Berman, told TIME the company thinks the immune system needs time to respond. The headline 42% remains the primary result.
Who was in the trial, and who wasn’t
Everyone enrolled had cutaneous melanoma, the kind that starts in the skin, at stage IIB, IIC, III or IV. Surgeons had removed all visible cancer. No patient had any earlier drug treatment for it, according to the trial’s ClinicalTrials.gov record.
The record also lists who couldn’t join. That includes people with ocular or mucosal melanoma and people whose spread cancer surgeons couldn’t remove. Anyone more than 13 weeks past their final surgery before starting Keytruda was out too. Patients with stage I or IIA melanoma weren’t part of the trial at all.
So the honest answer to “who is this for” is narrow for now. It’s adults with high-risk skin melanoma that surgery fully removed. It isn’t a preventive shot, and it isn’t approved anywhere yet.
The approach isn’t a sure bet in other cancers either. BioNTech’s personalized vaccine recently missed its goal in a mid-stage colorectal cancer trial, BioPharma Dive reported.
Side effects were mostly flu-like. Fever hit 52.2% of patients on the combination and injection-site pain 51.0%. Serious treatment-related events were close between the groups, at 14.2% and 13.4%. About 7% of intismeran patients stopped treatment because of side effects, against 5% on Keytruda alone, per BioPharma Dive.
Why doctors are impressed and investors weren’t
Oncologists have struggled for years to beat Keytruda alone after surgery. “I have led clinical trials. None of them has improved over PD-1,” Hussein Tawbi of MD Anderson, a trial investigator, told BioPharma Dive. “And now we see we can do better.”
Outside researchers were more measured. Jessamy Tiffen of Australia’s Centenary Institute wasn’t involved. She told The Guardian that “a significant portion do not respond to the vaccine”. She added that it’s unclear how well it works beyond two years.
Wall Street wanted more. Screenshots of the results leaked on social media on October 22, forcing an early release. Moderna’s shares fell by nearly a quarter, BioPharma Dive reported.
RBC Capital Markets put the result at the “low end” of expectations. The smaller Phase 2b study had looked slightly stronger. Its five-year update, presented at ASCO in June, showed a 49% lower risk in 157 patients.
The bigger unknowns are survival and cost. Overall survival data are “not yet mature”, Merck says, though it reports a favorable trend. Neither company has named a price.
RBC compared it with giving immunotherapy before surgery, “which produces similar efficacy at potentially much less cost,” BioSpace reported.
Melanoma is rarer than other skin cancers, and deadlier
Melanoma makes up only about 1% of skin cancers but causes most skin cancer deaths. The American Cancer Society estimates about 112,000 new US cases and 8,510 deaths in 2026. The far more common types, such as the basal cell carcinoma Gordon Ramsay had removed, rarely kill.
Catching it early changes the odds more than any drug. Five-year relative survival is above 99% when melanoma stays in the skin, ACS figures show. It drops to 76% once it reaches nearby lymph nodes, and 36% after it spreads to distant organs.
The ACS calls a new or changing spot the most important warning sign. A mole that looks unlike all your others deserves a doctor’s look too. Risk isn’t only about beach days. One study found more radiation-related cancer deaths among pilots and flight attendants, and melanoma was on that list.
Georgina Long, the trial’s lead investigator, presents the full data on Saturday, October 24, at the European Society for Medical Oncology congress in Madrid. The New England Journal of Medicine has accepted the paper. Merck and Moderna say they are “engaging with regulatory authorities”, so an FDA filing comes next. RBC analysts expect a US approval could come in 2027, BioSpace reported.