Six Melanoma Specialists Call Moderna-Merck Vaccine Data Clinically Meaningful as Full Presentation Nears in Madrid

Since Moderna and Merck released detailed Phase 3 melanoma results on Thursday, Oct. 22, after embargoed data leaked, the argument has shifted from the stock to the medicine. Six melanoma specialists have described the results as a clinically meaningful advance, even as Moderna shares closed down 17.6% and Merck's ended down 1.7%.

What the trial showed

The vaccine, intismeran autogene, cut the risk of melanoma recurrence or death by 42% when given with Merck's Keytruda, compared with Keytruda alone. The hazard ratio was 0.58.

The combination also cut the risk of the cancer spreading to distant parts of the body, or death, by 38%. The trial enrolled roughly 1,100 patients whose tumors had been removed by surgery.

The benefit was measured after about two years. A hazard ratio in that range is on par with or slightly lower than what Wall Street analysts had expected, and it is similar to the smaller Phase 2 trial.

The leak

The results were scheduled to be unveiled Saturday, Oct. 24, at the European Society for Medical Oncology meeting in Madrid. Oncology Central, a cancer news site operated by publisher Informa, published a story with the embargoed data on Thursday afternoon. The conference lifted the embargo after the leak, and the companies released their detailed results that day.

Oncology Central did not respond to a request for comment from Dow Jones.

What the doctors say

Dr. Sekwon Jang of Inova Schar Cancer, a principal investigator at one of the trial's U.S. sites, said the data could be "a major breakthrough in melanoma treatment and also cancer immunotherapy in general."

Dr. Janice Mehnert of NYU Langone, also a trial investigator, said it is "the first time we're seeing that when you add something to immunotherapy, you actually boost the efficacy of the immunotherapy."

Dr. Michael Postow, chief of the Melanoma Service at Memorial Sloan Kettering Cancer Center and a trial investigator, framed the goal this way: "If we can essentially cure more patients with earlier-stage melanoma and never have to deal with unresectable metastatic disease, that's a wonderful advance."

Dean Li, president of Merck Research Laboratories, called the study "one of the most significant advances in melanoma treatment since the advent of immunotherapy."

The specialists told CNBC the approach could become a standard of care for patients who have surgery first and have not received immunotherapy beforehand. Note who is talking: several of these doctors ran the trial or sit at sites that enrolled patients.

Why the stock fell anyway

The analyst view is more guarded. William Blair's Myles Minter questioned whether the drop was a "sell-the-news reaction" or reflected broader concern that efficacy did not differ markedly across patients with different mutational burdens in their tumors.

Melanoma has a high mutational burden, which is why immunotherapies already work well against it. Much of the hope for the vaccine is that it will also work in cancers with lower mutational burdens. Minter said that question alone is "a reason to wait" for the ESMO presentation this weekend.

An RBC Capital Markets analyst had said a hazard ratio between 0.5 and 0.6 would be "a pretty good result." The reported 0.58 sits inside that range.

What comes next

Moderna CEO Stéphane Bancel said in an interview before the release that the company is finishing a filing with regulators and aims to win full approval next year. "It's a very, very happy moment for the field, for patients," he said.

Several questions remain open: whether the combination extends overall survival, how durable the benefit is over longer follow-up, and which patients gain the most.

The full dataset goes public Saturday in Madrid. The subgroup breakdowns and any overall survival signal there will test whether the oncologists' enthusiasm or the market's caution reads the trial correctly. Moderna has not given a date for the regulatory filing.