Doctors Call Moderna-Merck Cancer Vaccine Data a Major Advance Despite Stock Selloff

The trial enrolled about 1,100 patients whose tumors had been removed by surgery. The combination also reduced the risk of cancer spreading to distant parts of the body or death by 38% compared with the immunotherapy alone, according to the companies. The vaccine is called intismeran autogene.

The stock reaction contrasted with the doctors’ assessment. Moderna shares fell as much as 25% on Thursday before regaining some ground after partial data leaked on social media, CNBC reported. The sell-off came despite the positive results and highlighted the gap between the treatment’s clinical promise and investor expectations for its commercial potential. Moderna shares are up nearly 600% this year on optimism about the cancer shot, leaving more room for a Wall Street letdown.

Keytruda is an immunotherapy that wakes up the immune system to detect and attack cancer cells. Unlike preventive vaccines, which protect against infections that can cause cancer, the Moderna-Merck treatment is designed to train the immune system to recognize and hunt residual cancer cells based on mutations in an individual patient’s tumor.

Doctors said the significance goes beyond delaying recurrence. Melanoma becomes harder to treat when it returns after surgery and spreads to distant organs such as the lungs, brain or liver. Patients with advanced disease may need additional immunotherapy, radiation or surgery, and those methods are not guaranteed to work. Preventing the cancer from returning could spare patients the risks and complexities of metastatic disease.

“This has the potential to be a major breakthrough in melanoma treatment and also cancer immunotherapy in general that will open the door to greater outcomes for patients,” said Dr. Sekwon Jang, a melanoma specialist at Inova Schar Cancer and a principal investigator at one of the trial’s U.S. sites. Dr. Janice Mehnert, a skin cancer specialist at NYU Langone and a trial investigator, said: “This 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, said preventing unresectable metastatic disease would be “a wonderful advance.” Ideally, Postow told CNBC, patients in the future may be able to undergo surgery and receive the vaccine and Keytruda without needing further melanoma treatment.

Moderna CEO Stéphane Bancel said in an interview ahead of the results that the company is finishing a filing with regulators and aims to get the drug fully approved next year. “It’s a very, very happy moment for the field, for patients,” he said, according to CNBC.

Questions remain. The trial has not yet shown whether the combination helps patients live longer, what the benefit looks like over longer periods or which patients benefit most. The results also leave open where the vaccine would fit in a changing melanoma treatment landscape, some experts said. The trial tested the vaccine after surgery with Keytruda, rather than against immunotherapy given before surgery, an approach increasingly used for eligible patients with resectable melanoma, where the primary tumor can be removed. The data do not show whether the vaccine approach is more or less effective than receiving immunotherapy before surgery.

Moderna and Merck plan to present detailed results at the European Society for Medical Oncology conference on Saturday. Investors had hoped the vaccine and Keytruda would replicate an earlier Phase 2 trial, which showed a roughly 49% reduction in the risk of recurrence or death at five years, RBC Capital Markets analyst Trung Huynh wrote in a note Thursday, according to CNBC. Huynh described the Phase 3 results as clinically meaningful.