Moderna Shares Surge After mRNA Cancer Treatment Passes Key Trial
Moderna’s stock more than doubled on Wednesday after the company and partner Merck announced that their experimental mRNA-based cancer treatment passed a critical Phase 3 clinical trial, marking the first positive late-stage readout for a personalized cancer vaccine. The treatment, called intismeran autogene, showed statistically significant improvements in recurrence-free survival and distant metastasis-free survival when combined with Merck’s immunotherapy drug Keytruda in patients with completely resected stage IIB-IV melanoma, according to AP News.
A First-of-Its-Kind Breakthrough
The INTerpath-001 trial met its primary endpoint of recurrence-free survival (RFS) and a key secondary endpoint of distant metastasis-free survival (DMFS) at a pre-specified interim analysis, the companies announced. This represents the first positive Phase 3 readout for an individualized neoantigen therapy (INT) and for an mRNA-based cancer therapy, as well as the first Phase 3 study to demonstrate a clinically meaningful improvement over Keytruda alone in the adjuvant setting for patients with resected melanoma, per the Merck press release.
The trial enrolled 1,137 patients with completely resected stage IIB, IIC, III or IV cutaneous melanoma who had not undergone prior systemic therapy. Patients were randomized 2:1 to receive intismeran plus Keytruda versus Keytruda alone, according to the trial registry.
“Today’s results represent a landmark moment for adjuvant melanoma treatment,” said Professor Georgina Long, the study’s principal investigator and medical director of Melanoma Institute Australia. “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.”
How the Therapy Works
Intismeran autogene is a novel, potential first-in-class investigational mRNA-based individualized neoantigen therapy jointly developed by Merck and Moderna. Each therapy is designed and produced using a patient’s tumor sample to identify the unique mutational signature, or “fingerprint,” of their cancer. The treatment consists of a synthetic mRNA coding for up to 34 neoantigens tailored to the unique biology of an individual patient’s tumor, training the immune system to recognize and fight cancer cells.
Keytruda, an anti-PD-1 therapy first approved to treat melanoma in 2014, works by removing the brakes on the immune system, allowing T cells to attack tumors. The combination approach uses intismeran to teach the immune system to recognize cancer-specific mutations while Keytruda activates the immune response.
“What we’re trying to do here is to tell the immune system that it missed the signature of the tumor cell if you have cancer,” Moderna CEO Stéphane Bancel told TIME. “This product basically allows us to teach the immune system about the mutation in your cancer that allows the cancer to grow.”
Market Reaction
Investors responded dramatically to the news. Moderna shares rose more than 120% to $140.12 per share, while Merck shares gained about 11%, AP News reported. Business Insider noted that Moderna stock surged as much as 160% to $163.47 at its peak on Wednesday.
The surge comes after a difficult period for Moderna, which had seen its stock drop from COVID-era highs. Even after Wednesday’s rally, shares remain roughly two-thirds below the peak of $484 reached in August 2021, according to Business Insider.
Building on Earlier Evidence
The Phase 3 results build on previously reported Phase 2b findings from the KEYNOTE-942/mRNA-4157-P201 trial. Five-year follow-up data presented at the 2026 ASCO Annual Meeting showed a 49% reduction in the risk of recurrence or death and a 59% reduction in the risk of distant metastasis or death compared to Keytruda alone, according to the Moderna press release.
So-called “neoantigen” vaccines have long been seen as having potential as cancer treatments, but this is the first randomized Phase 3 clinical trial aimed at definitively proving their benefit, STAT News reported. If the results hold up, they could deliver new hope and potentially longer lives for patients with melanoma.
“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,” said Dr. Dean Y. Li, president of Merck Research Laboratories. “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.”
Regulatory Path and Future Development
The companies plan to present the data at an upcoming international medical meeting and will engage with regulators on filing submissions. The vaccine could potentially receive approval as early as 2027, depending on the regulatory review, ZeroHedge reported.
The INTerpath program currently consists of nine total Phase 2 and Phase 3 clinical trials across multiple tumor types, including melanoma, non-small cell lung cancer, bladder cancer, and renal cell carcinoma. Moderna is also studying intismeran in earlier-stage cancers, including stage 1 lung cancer, according to TIME.
“These Phase 3 findings represent a pivotal moment for the field of cancer research,” Bancel said. “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.”
Significance for Patients
Melanoma, one of the deadliest forms of skin cancer, accounts for about 112,000 new cases diagnosed annually in the U.S., with over 8,500 deaths resulting from the disease in 2026 alone. More than 330,000 new cases were diagnosed worldwide in 2022. Despite advances in treatment, patients with resected melanoma remain at risk of disease recurrence, which most often occurs within the first two years.
“Therapeutic vaccines have been something of a holy grail in cancer,” Jane Healy, head of oncology early development at Merck, told ZeroHedge. “People have been trying to do this for, you know, over 100 years in one way or another.”
The safety profiles of intismeran and Keytruda in this trial were consistent with those observed in previously reported studies, with no new safety signals observed, according to the companies.
What’s Next
The companies did not disclose specific figures on how much the therapy improved recurrence-free survival, noting that the study will continue to evaluate other key secondary endpoints, including overall survival. Full data will be presented at an upcoming international medical meeting.
Bancel expressed optimism about the broader potential of the technology. “I think it will be transformational,” he told TIME. “Think about if you get a screening X-ray and find stage 1 lung cancer. Then you get intismeran, which is like a vaccine so you have no severe toxicity like with other immunotherapy. Think about getting this product on your way to work, or even [potentially] at your local pharmacy—that would be an incredible change in care.”
As the companies move toward regulatory submissions, the oncology community will be watching closely to see whether this first positive Phase 3 result for an mRNA-based cancer therapy opens the door to a new era of personalized cancer treatment.