First personalised cancer vaccine cuts risk of disease returning in major trial

A personalized mRNA cancer vaccine has demonstrated a substantial reduction in the risk of melanoma returning in a major clinical trial, according to results announced on October 22. The experimental therapy, known as intismeran, cut the likelihood of disease recurrence or death by 42 percent over two years when administered alongside standard immunotherapy. This marks the first time such a tailored vaccine has shown efficacy in a large-scale phase III study involving more than 1,130 adults with advanced skin cancer. All participants in the trial had previously undergone surgical removal of their tumors. The study enrolled individuals diagnosed with Stage 2B to Stage 4 melanoma. Approximately two-thirds of the cohort received the experimental vaccine, while the remainder were assigned to a placebo group. Both groups also received Keytruda, an established checkpoint inhibitor that helps the immune system identify and attack cancer cells. Patients in the active arm received intismeran injections every three weeks for up to nine doses, paired with Keytruda every six weeks for up to nine cycles, spanning roughly one year. The vaccine utilizes mRNA technology similar to certain coronavirus vaccines, encapsulating genetic instructions for 34 specific proteins found on tumor cells within lipid particles. This process trains the immune system to recognize these unique markers as threats. Developed jointly by Moderna and Merck, the therapy aims to prime the body’s defenses before cancer cells can resurface. Data indicated that the protective effect began appearing approximately six months into the treatment regimen. While the results did not match the magnitude seen in an earlier, smaller phase II trial, which reported a 49 percent reduction in recurrence or death over five years, the consistency of the findings surprised researchers. Dr. David Berman, chief development officer at Moderna, noted that the replication of phase II results in a broader population exceeded expectations, given initial skepticism that the effect might diminish in a larger, more diverse group. Market reaction to the announcement was mixed. Shares in both pharmaceutical companies surged following early hints of success in the summer. However, stocks declined on Thursday after financial analysts observed that the final figures were slightly weaker than those from the preliminary studies. Despite this, both firms stated they are engaging with regulatory authorities, signaling potential filings for approval as early as next year. Widespread adoption within the National Health Service in the United Kingdom will hinge on cost considerations, as each patient requires individual genetic analysis of their tumor to manufacture a bespoke vaccine. Independent experts viewed the findings cautiously. Professor Alan Melcher of the Institute of Cancer Research in London, who was not involved in the study, described the results as very impressive but warned against extrapolating success to all cancer types. He emphasized that longer follow-up is necessary to determine impact on overall survival. Similarly, Professor Pippa Corrie, a consultant medical oncologist at Addenbrooke's Hospital in Cambridge who participated in the trial, called personalization an exciting technological advancement and a crucial proof of principle. The full dataset is scheduled for presentation at the European Society of Medical Oncology conference in Madrid on Saturday. The findings have not yet been published in a peer-reviewed journal, meaning independent scientific scrutiny is still pending. The trial will continue to monitor long-term outcomes and survival rates.