Key Moments
- mRNA vaccine intismeran autogene plus Keytruda reduced the risk of melanoma death or recurrence by 42% in a Phase 3 trial of more than 1,100 patients.
- The combination also cut the risk of melanoma spreading by 38%, with 82.2% of patients on the combo cancer-free at two years versus 70% on Keytruda alone.
- Despite positive data, Moderna shares fell more than 17% and Merck shares slipped about 1.8% after results leaked ahead of a scheduled conference presentation.
Trial Results Point to Significant Reduction in Melanoma Risk
Moderna and Merck reported that their personalized mRNA cancer vaccine, when used with Merck & Co’s widely prescribed immunotherapy Keytruda, reduced the risk of melanoma-related death or disease recurrence by 42% in a large Phase 3 study. The trial enrolled more than 1,100 patients and is being viewed as a potential milestone in personalized oncology.
The study also found that the vaccine-Keytruda combination lowered the likelihood of melanoma spreading by 38%. The vaccine, called intismeran autogene, is tailored to tumor-specific mutations in each individual patient and was evaluated alongside Keytruda, one of the world’s top-selling cancer therapies.
Market Reaction and Investor Sentiment
Moderna’s stock had surged since August, when the companies first disclosed that the trial had succeeded but did not share detailed results. By Wednesday’s close, Moderna shares had almost quadrupled. On Thursday, however, the stock ended more than 17% lower after the trial data appeared on an oncology website ahead of the formal release. Merck shares finished the session down about 1.8%.
Some analysts indicated that, while the data are positive, they may temper expectations about how broadly this personalized mRNA vaccine approach could be applied across multiple cancer types.
How the Combination Therapy Works
Keytruda is designed to lift a natural brake that cancer cells exploit to evade immune detection, thereby allowing the immune system to attack tumors more effectively. Intismeran autogene is an mRNA vaccine that directs a patient’s cells to generate copies of specific tumor mutations, training the immune system to recognize and destroy those cancer cells.
Moderna CEO Stephane Bancel described the results as an inflection point for cancer care.
“With this ability to create new T cells that are specific to your tumor… the clinical impact is very profound, and as we saw in the Phase 2 (trial), very lasting,” Bancel said in an interview.
Regulatory Plans and Development Outlook
The companies are preparing to seek U.S. regulatory approval, and Bancel said they expect to introduce the cancer vaccine in 2027, assuming a successful review process. The combination of intismeran and Keytruda is already under evaluation in several additional tumor types, including kidney, bladder, and lung cancers.
Bancel said he expects the vaccine to enhance outcomes “everywhere that Keytruda works,” although the magnitude of benefit remains uncertain. Keytruda currently has approvals in 19 different cancers. He also said that intismeran may have potential as a standalone therapy in early-stage disease.
Detailed Efficacy Metrics
The Phase 3 melanoma data reflect outcomes during the first two years following treatment. Among patients receiving the vaccine in addition to Keytruda, 82.2% remained free of cancer at the two-year mark, compared with 70% of those treated with Keytruda alone.
Dr. Hussein Tawbi, a melanoma specialist and trial investigator at the University of Texas MD Anderson Cancer Center, emphasized the robustness of the findings.
“This is highly statistically significant. It is not by chance,” Dr. Tawbi said of the results.
| Measure | Intismeran + Keytruda | Keytruda Alone |
|---|---|---|
| Risk of death or recurrence | 42% reduction vs. Keytruda alone | Reference group |
| Risk of cancer spread | 38% reduction vs. Keytruda alone | Reference group |
| Patients cancer-free at 2 years | 82.2% | 70% |
Conference Presentation and Trial Design
The melanoma Phase 3 results, covering the first two years of patient follow-up, are scheduled to be presented on Saturday at the European Society for Medical Oncology meeting in Madrid.
In the study, patients received nine doses of intismeran in combination with Keytruda, beginning 13 weeks after surgery to remove melanoma lesions. Outcomes from this group were compared with those of patients treated with Keytruda alone, which is a standard therapy in melanoma.
Analyst Views and Commercial Implications
Several Wall Street analysts had anticipated that investors would look for at least a 40% reduction in recurrence risk from the combination regimen ahead of the data presentation.
“We see optimism waning on pricing in multibillion-dollar (intismeran) franchises across oncology,” wrote RBC analyst Trung Huynh. “This data makes us less optimistic as melanoma was supposed to be the best case.”
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