After its COVID success, Moderna endured years of falling vaccine sales, a plummeting stock price and attacks on its science. Now, its melanoma vaccine data notched a much-needed win for the company.

Moderna experienced a significant turnaround in investor confidence after its personalized mRNA cancer vaccine, intismeran, developed in partnership with Merck & Co., succeeded in a highly anticipated Phase 3 trial for melanoma. This news led to Moderna's stock price rocketing by over 170%, adding nearly $45 billion to its market value in a single day. This surge brought the company's stock to levels not seen since 2024, following years of decline from its COVID-era highs.

The company had faced a challenging period marked by sputtering sales, slashed revenue projections, and difficulty in finding another lucrative product after the success of its COVID-19 vaccine. For much of 2025, shares once valued at over $400 were trading at less than $30. The positive trial results for intismeran, which trains the immune system to recognize and fight cancer cells, have been hailed as a "major win" and a "landmark moment" by analysts like Trung Huynh of RBC Capital Markets and Tyler Van Buren of TD Cowen.

The intismeran vaccine is designed to trigger immune responses against 34 unique protein flags found on a patient's tumor. It was tested alongside Merck's immunotherapy Keytruda in patients with high-risk melanoma following surgical removal of the tumor. While specific data from the Phase 3 trial were not disclosed, the findings suggest that the combination could delay cancer recurrence longer than Keytruda alone and may become a multibillion-dollar melanoma treatment, with potential applications for other tumor types. The massive stock surges, which also saw Merck and rival BioNTech's shares spike, indicate Wall Street's belief in intismeran becoming a cornerstone of melanoma care.

Analysts have revised revenue projections, with William Blair's Myles Minter upgrading Moderna's stock and projecting peak annual sales of $5.4 billion in melanoma alone for Moderna's 50-50 revenue split with Merck. Barclays estimates the therapy could reach about $3 billion in melanoma sales by 2035. However, some analysts, such as Evercore ISI's Cory Kasimov and Leerink Partners' Daina Graybosch, cautioned that the market's euphoric response might have overshot intismeran's actual sales potential and set expectations that will be difficult to meet. Graybosch also noted that melanoma is "uniquely suited to a vaccine," and success in other indications might be a flawed assumption.

The trial results build on positive Phase 2 data and met key goals by significantly extending the time patients lived without their melanoma returning and reducing the risk of the cancer spreading. This marks the first positive late-stage trial result for an mRNA cancer vaccine. Moderna President Stephen Hoge indicated that thousands of patients could benefit as early as next year if regulators approve the vaccine.