Moderna Stock Nearly Triples on Cancer Vaccine Trial

Moderna Inc. experienced the largest single-day stock surge in its history on Wednesday, with shares jumping approximately 177% after the company and partner Merck & Co. announced positive Phase 3 trial results for their personalized mRNA cancer vaccine in patients with resected melanoma. The stock closed at $174.38, up from a prior close of $62.96, touching an intraday high of $163.47 — a 52-week high and roughly five times larger than Moderna’s previous record single-day gain of +27.8% on February 25, 2020.

The surge delivered a $5.5 billion blow to short sellers who had bet against the vaccine maker’s continued slump, according to 24/7 Wall St. via Yahoo Finance. The stock’s market capitalization reached approximately $56.18 billion following the rally, bringing its year-to-date gain to 445%.

A First-of-Its-Kind Breakthrough

The Phase 3 INTerpath-001 trial met its primary endpoint of recurrence-free survival (RFS) and key secondary endpoint of distant metastasis-free survival (DMFS) at a pre-specified interim analysis, according to the official press release from Merck and Moderna. This represents the first positive Phase 3 readout for an individualized neoantigen therapy (INT), the first for an mRNA-based cancer therapy, and the first Phase 3 study to demonstrate a clinically meaningful improvement over KEYTRUDA alone in the adjuvant melanoma setting.

The trial enrolled 1,137 patients with completely resected Stage IIB-IV cutaneous melanoma who were randomized 2:1 to receive intismeran autogene — an mRNA-based individualized neoantigen therapy designed from each patient’s unique tumor mutations — plus KEYTRUDA, versus KEYTRUDA alone.

“Today’s results represent a landmark moment for adjuvant melanoma treatment,” said Professor Georgina Long, the study’s principal investigator and chair of Melanoma Medical Oncology and Translational Research at the University of Sydney, as reported by CBS News. “This is the first Phase 3 study to show that intismeran, a treatment designed based on the unique mutational ‘fingerprint’ of a patient’s own tumor, given in combination with pembrolizumab can reduce the risk of recurrence or death in patients with completely resected stage IIB-IV melanoma compared to KEYTRUDA alone.”

A Pivotal Moment for mRNA Cancer Therapy

Stéphane Bancel, CEO of Moderna, called the findings “a pivotal moment for the field of cancer research,” according to Business Insider. “For many years, the idea of creating an mRNA treatment designed specifically for an individual patient’s cancer was aspirational. We are now helping turn that vision into a reality.”

Dr. Dean Y. Li, President of Merck Research Laboratories, emphasized the broader significance: “By intervening earlier in the course of disease, when many cancers are considered most treatable, the goal of adjuvant therapy given after surgery is to increase the possibility of cure for more patients. These first Phase 3 findings for intismeran in combination with KEYTRUDA as adjuvant therapy reinforce the promise of a more personalized approach to cancer treatment.”

The result validates years of research and builds on earlier Phase 2b data. At five years, the combination was associated with a 49% reduction in the risk of recurrence or death and a 59% reduction in the risk of distant metastasis or death, as Ars Technica reported earlier this year.

From COVID Darling to Oncology Pioneer

Moderna became a household name during the COVID-19 pandemic as one of the first companies to develop an effective mRNA vaccine. The stock peaked at $484 per share in August 2021 but subsequently declined more than 90% as demand for COVID vaccines fell post-pandemic, with the stock’s 52-week low reaching $22.28.

The company had been working to diversify beyond infectious disease, and the cancer vaccine success marks a significant strategic shift. Two weeks before the trial announcement, the FDA approved mFLUSIVA (mRNA-1010), the first mRNA-based seasonal influenza vaccine cleared in the US, for adults 50 and older — Moderna’s fourth approved US product.

Alec Stranahan, a Bank of America analyst, called the result “a watershed moment for Moderna, in our view, effectively allowing the company to diversify away from infectious disease and potentially easing persistent capital overhangs,” as noted by BioSpace.

Market Reaction and Analyst Perspectives

The dramatic move reflects the gap between what the trial proved and what the market had been willing to pay for. As Flicker Finance analyzed, Moderna had been priced as a melting COVID asset, with the oncology program valued at close to zero. The Phase 3 readout changed the category the company trades in — from a declining vaccine business to a validated oncology platform.

Analyst targets moved but not uniformly. Morgan Stanley raised its price target to $209 from $170 while keeping an Equal Weight rating, reflecting the debate about whether the stock has already moved too much. Barclays models roughly $3 billion in peak sales for intismeran in melanoma alone by 2035. JPMorgan’s Jessica Fye noted that “success in adj melanoma [is] priced in with the stock sitting at ~$25bn market cap prior to the news,” and that “the read-across to other indications [is] critical.”

On Thursday, Moderna stock pulled back approximately 20% to $130.67 as investors took profits, while BioNTech fell 4% on diminishing read-across enthusiasm, according to Forbes.

What’s Next

Several critical questions remain. The complete intismeran dataset has not been publicly presented — the hazard ratios and magnitude of benefit will be revealed at an upcoming international medical meeting, potentially at ESMO in Madrid from October 23-27, 2026. Overall survival data are immature and the trial continues, an endpoint oncologists and payers care most about.

Both companies said they will “engage with regulatory authorities” but no filing timeline has been announced. The INTerpath program includes nine total Phase 2 and Phase 3 trials across multiple tumor types, including non-small cell lung cancer, bladder cancer, and renal cell carcinoma, and whether the melanoma result extends to other tumor types remains a key question.

As OncoDaily noted, the current Phase 3 result establishes a significant improvement in RFS and DMFS, but it does not yet demonstrate an overall survival benefit. Manufacturing an individualized therapy at commercial scale — where every dose is bespoke — also remains a real constraint.

For now, the landmark trial result has transformed Moderna’s trajectory and validated the promise of personalized mRNA cancer therapy. The full dataset, regulatory path, and read-across to other cancer types will determine whether this historic rally marks the beginning of a new era for the company and for cancer treatment.