TLDR
- Merck stock dips 0.67% despite a 42% drop in melanoma recurrence or death risk.
- Merck and Moderna’s mRNA therapy cuts distant metastasis or death risk by 38%.
- Phase 3 melanoma trial reports 82.2% recurrence-free survival at two years.
- MRK falls to $148.87 even as personalized cancer therapy posts strong trial data.
- Merck and Moderna plan regulatory talks after promising melanoma trial results.
Merck & Co. shares declined despite positive Phase 3 results for a melanoma treatment developed with Moderna. MRK fell 0.67% to $148.87, losing $1.01 as midday selling erased earlier gains. The companies reported lower risks of cancer recurrence and distant spread when patients received personalized mRNA therapy alongside KEYTRUDA.
Phase 3 Trial Shows Lower Melanoma Recurrence Risk
Merck and Moderna tested intismeran autogene, an experimental therapy tailored to genetic changes in each patient’s tumor. The treatment uses mRNA technology to help the immune system recognize cancer-related targets. Researchers paired intismeran with Merck’s immunotherapy KEYTRUDA after patients underwent surgery for melanoma.
The INTerpath-001 trial enrolled 1,137 patients with completely removed stage IIB through IV melanoma. Researchers assigned participants to receive either intismeran plus KEYTRUDA or placebo plus KEYTRUDA. After a median 24.6 months, the combination reduced the risk of recurrence or death by 42%.
The treatment also reduced the risk of distant metastasis or death by 38% against KEYTRUDA alone. Both findings met statistical significance, and researchers observed broadly consistent benefits across planned patient subgroups. Overall survival data remain immature, although researchers reported a favorable trend for the combination.
Two-Year Results Detail Benefits and Side Effects
After two years, 82.2% of combination patients remained free from recurrence, compared with 70.0% receiving KEYTRUDA alone. The corresponding rates for remaining free from distant metastasis reached 88.5% and 80.2%. Neither treatment group had reached its median recurrence-free or distant metastasis-free survival point.
During the first six months, researchers found similar recurrence and distant metastasis outcomes across both treatment groups. However, a planned six-month analysis showed a 58% lower recurrence or death risk with the combination. Researchers also recorded a 50% lower risk of distant metastasis or death in that analysis.
Treatment-related side effects affected 95.8% of combination recipients and 90.0% of the comparison group. Grade 3–5 treatment-related events occurred in 14.2% and 13.4% of patients, respectively. Fever, injection-site pain and fatigue were the most common reported reactions among combination recipients.
Merck and Moderna Pursue Broader Cancer Studies
Merck and Moderna plan to discuss the trial findings with regulators as they continue collecting survival data. The companies also intend to present detailed findings at the 2026 European Society for Medical Oncology Congress. The New England Journal of Medicine has accepted the results for publication.
The companies run nine Phase 2 and Phase 3 studies across several cancer types and disease stages. Three Phase 3 trials focus on non-small cell lung cancer, while other studies examine additional treatment settings. Researchers are also studying intismeran in pancreatic and gastric cancers.
Earlier Phase 2b melanoma results supported the companies’ decision to advance the personalized treatment into larger trials. However, the latest trial has not yet established a final overall survival benefit. Merck shares nonetheless ended lower despite the reported clinical progress and continued development plans.
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