Moderna Soars 177% After Melanoma Vaccine Clears Late-Stage Trial on August 19

Moderna and Merck announced Wednesday that their experimental personalized cancer vaccine met its primary goal in a Phase 3 trial of over 1,100 melanoma patients. The mRNA-based shot combined with Merck’s immunotherapy Keytruda significantly extended the time patients lived without their cancer returning and reduced the risk of spread. Moderna shares soared 177% to $174.38 while Merck climbed 12% to $152.22, delivering a $5.5 billion blow to short sellers betting against the vaccine maker.

What the trial showed

The INTerpath-001 trial tested intismeran, a personalized neoantigen vaccine, paired with Keytruda in patients with advanced melanoma whose tumors had been surgically removed. The combination met the main study goal of significantly extending recurrence-free survival compared to Keytruda alone. It also reduced the risk of cancer spreading to distant parts of the body. This marks the first positive Phase 3 readout for an individualized neoantigen therapy and the first Phase 3 study to show a clinically meaningful improvement over Keytruda alone in the adjuvant setting for resected melanoma.

Why the stock surge matters

Moderna’s 177% jump reflects years of losses and skepticism about the company’s pipeline beyond COVID vaccines. Short sellers faced $5.5 billion in paper losses, bringing their year-to-date mark-to-market losses to roughly $7.7 billion. Meyka grades Moderna a B with a 12-month forecast of $58.61, suggesting the stock may face headwinds despite the win. Merck’s more modest 12% gain reflects its larger market cap of $376 billion versus Moderna’s $69 billion.

What comes next

The companies plan to present full data at an upcoming international medical meeting and will likely begin talks with regulatory agencies about the treatment “in the next few months,” according to Dr. Dean Li, president of Merck Research Laboratories. The Phase 3 trial will continue to assess overall survival, the ultimate measure of benefit. Neither company has disclosed a timeline for filing for approval in the U.S., though Moderna CEO Stephane Bancel called it “a big moment for medicine, a big moment for patients.”

Why melanoma matters

Melanoma accounts for only about 1% of all skin cancers but causes the vast majority of skin cancer deaths. Most recurrences develop within two to three years of initial treatment. A successful vaccine could offer a new treatment option for patients at high risk of recurrence, potentially extending survival and improving quality of life for thousands of patients annually.

Final Thoughts

Moderna’s 177% surge reflects genuine clinical progress, but Meyka’s B grade and $58.61 forecast suggest caution. Merck’s B+ rating and analyst consensus of 11 buys support the partnership’s long-term value, though regulatory approval remains years away.

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