Moderna vaccine cuts relapse risk 42% in Phase 3 skin cancer trial
Key Facts
Phase 3 results showed that Moderna’s intismeran vaccine, when combined with Merck’s Keytruda, reduced the risk of skin cancer recurrence or death by 42% compared with Keytruda alone. The study met both primary endpoints: relapse-free survival and distant metastasis-free survival. At 24 months of follow-up, the relapse-free survival rate was 82.2% in the combination-therapy group, versus 70.0% in the Keytruda-alone group, according to data reported by Fierce Biotech. The results put the combination’s efficacy against an active comparator, rather than against no treatment. But the market reaction was sharp after the details were published, with Moderna shares falling during Thursday’s session.
On the other measure, distant metastasis-free survival at 24 months was 88.5% among those who received the combination therapy, versus 80.2% in the Keytruda-alone group. Fierce Biotech said the combination therapy reduced the risk of distant metastasis or death by 38%. A comparison with Phase 2 results helps explain why investors focused on this measure: the reduction recorded in Phase 3 was below estimates from earlier follow-up. Even so, meeting the distant metastasis-free survival endpoint remains part of the positive result announced, alongside improved relapse-free survival. The difference between the two measures matters in assessing the treatment profile because they measure separate clinical outcomes.
Moderna shares fell 25.2% during Thursday’s session on October 22, reaching $183.88, in a decline Reuters said was on track to become the largest percentage drop in the company’s history in a single day. Merck shares also fell about 1% in the same session. The selloff followed a wave of anticipation before the results announcement: EL7 published a story on October 5 about the stock rising 8% as investors awaited skin cancer vaccine data. It then published a story on October 16 about the stock falling 10% as profit-taking began after the vaccine-related rally. EL7 data showed Moderna closed at $200.1 on October 23, after closing at $245.81 on October 21; these are dated closing prices and do not represent the stock price during the session in which it fell.
UBS analyst Michael Yee said the relapse-free survival results represented “strong data” and described the decline as an expected “sell the news” reaction. That interpretation reflects a gap between clinical figures showing improvement over the control group and investor expectations, which had risen before the details were released. Reuters reported that the two companies said overall survival data were not yet mature, but showed a “positive trend.” Dr. Hussein Tawbi of MD Anderson Cancer Center described the result as significant, saying the field had been looking for a success. The medical assessment places the results among important advances in developing a therapeutic cancer vaccine, while judgment on its effect on overall survival remains tied to the maturation of the data.
The INTERPATH-001 trial included 1,137 patients with high-risk melanoma after complete tumor resection, randomly assigning them in a 2-to-1 ratio to intismeran with Keytruda or Keytruda alone. Participants received intismeran at a dose of 1 mg every three weeks, for up to nine doses, alongside Keytruda at a dose of 400 mg every six weeks, for up to nine cycles. The comparison group provides a direct basis for measuring what the vaccine doses add to immunotherapy used alone. On safety, treatment-related adverse events occurred in 95.8% with the combination, versus 90% with Keytruda alone. The companies said they observed no new safety signals in the trial.
Merck and Moderna said they would present the data at an international medical meeting and engage with regulators on applications to register intismeran with Keytruda. The announced information did not specify the meeting date or a timeline for filing applications. Additional overall survival data remain immature, according to what the companies told Reuters, despite the positive trend they noted. The regulatory steps and scientific presentation are the next milestones in evaluating the treatment after the Phase 3 results. A registration decision will follow review of the data and the full treatment dossier by the relevant authorities.