A personalized messenger RNA (mRNA) vaccine, intismeran, lowered the chance of melanoma returning or the patient dying by 42% when used together with the immunotherapy drug pembrolizumab, according to results from a phase III trial. The data were released after a leak on 22 October and will be formally presented at the European Society for Medical Oncology meeting in Madrid on 24 October.
Trial Design and Results
The study enrolled 1,137 adults with moderate to advanced melanoma across 157 centres. Participants were randomly assigned to receive either intismeran plus pembrolizumab or pembrolizumab with an inactive placebo. Median follow‑up time to date is about 25 months, with plans for several more years of monitoring to assess overall survival. Trial leader Georgina Long, an oncologist at Melanoma Institute Australia, noted that the combination did not produce any major safety concerns.
Long explained that the vaccine is not intended to prevent melanoma from developing initially; rather, it targets patients who have already undergone surgical removal of tumors and are at risk of recurrence. The vaccine is customized for each patient by sequencing DNA from their tumor, identifying mutations that generate neoantigens, and then formulating a vaccine that trains the immune system to recognize those unique markers.
Implications and Market Reaction
Oncologists consider a 10% risk reduction substantial. Kristen Radford, an immunotherapist at Mater Research in Brisbane, called such a reduction “substantial,” while geneticist Seth Cheetham of the University of Queensland said a reduction exceeding 40% would “send many researchers over the Moon.” The results therefore represent a notable advance for personalized cancer vaccines, a field that has awaited a clear efficacy signal.
Financial markets reacted sharply. Moderna’s share price, which had risen since the August announcement of earlier positive data, fell roughly 25% after the October leak. BMO Capital Markets analyst Evan Seigerman suggested the drop reflected “inflated expectation into the full data release, rather than a true indictment on the efficacy of the combo therapy.”
Future Outlook
Experts caution that longer‑term data are needed. Cancer geneticist Jessamy Tiffen of the Centenary Institute noted that while the findings are exciting, “only time will tell how effective the treatment is beyond two years,” and that some patients did not respond to the vaccine. Long’s team plans a statistical analysis to identify which subgroups benefit most.
Historically, advanced melanoma patients survived only months, but today nearly 55% achieve durable remission with targeted drugs or immunotherapies. The intismeran‑pembrolizumab regimen aims to address the subset whose disease may recur after surgery and who do not respond adequately to immunotherapy alone. If subsequent data confirm the early benefit, the therapy could become the first approved mRNA vaccine for cancer, opening a new commercial avenue for Moderna and its partner Merck.
Mitchell Landsberg is a Senior Technology Correspondent at News Raise. He covers consumer electronics, artificial intelligence, software developments, and digital privacy trends.
