'Cancer vaccines are coming': Merck, Moderna clear Phase 3 hurdle as Korean biotech joins the race

The messenger RNA (mRNA) technology that became humanity's frontline defense during the COVID-19 pandemic has now crossed a new threshold — the fight against cancer. A personalized therapeutic cancer vaccine, custom-built by analyzing the genetic profile of each patient's tumor cells, has demonstrated efficacy in a global Phase 3 trial for the first time, opening the door to commercialization. A South Korean biotech company is also adding momentum to the race, publishing preclinical results from its own delivery platform — one designed to overcome the limitations of existing carriers — in an international academic journal.

US pharmaceutical companies Merck (MSD) and Moderna announced Wednesday (local time) that they had obtained positive top-line results from a global Phase 3 trial (INTerpath-001) conducted in high-risk (stage 2B–4) cutaneous melanoma patients who had undergone complete resection surgery.

According to the announcement, the combination of the jointly developed mRNA-based personalized neoantigen therapy "intismeran autogene" (project name mRNA-4157/V940) and Merck's flagship immune checkpoint inhibitor Keytruda (pembrolizumab) produced statistically significant and clinically meaningful improvements over Keytruda alone in the primary endpoint of recurrence-free survival (RFS) and the key secondary endpoint of distant metastasis-free survival (DMFS).

This marks the first time a personalized neoantigen therapy and an mRNA-based cancer treatment has produced successful results in a Phase 3 trial. It is also the first Phase 3 study to demonstrate superiority over Keytruda monotherapy — the current standard of care — in the adjuvant treatment setting following surgery.

The Phase 3 trial enrolled 1,137 high-risk resected melanoma patients with no prior systemic therapy and was conducted as a randomized, double-blind study. The two companies plan to continue evaluating additional secondary endpoints, including overall survival (OS), in line with the clinical protocol, present detailed data at future international medical conferences, and initiate regulatory submissions with authorities in relevant countries.

The word "vaccine" typically calls to mind a preventive agent that blocks viral infection before it occurs. Cancer vaccines are different — they are therapeutic vaccines designed to attack existing cancer cells or eliminate microscopic residual disease after surgery, preventing recurrence and metastasis.

Intismeran is manufactured by genetically analyzing tumor tissue removed during surgery to identify the unique mutational "fingerprint" of that patient's cancer cells, then synthesizing an mRNA strand encoding up to 34 neoantigens specific to that patient. Once injected, the body's cells produce the corresponding neoantigen proteins, and the immune system — specifically T cells — is trained to recognize and target only the cancer cells carrying those neoantigens, leaving healthy tissue unharmed.

The results are particularly significant because they demonstrate, through a large-scale clinical trial, the powerful synergy between an immune checkpoint inhibitor — which releases the "immune evasion brake" cancer cells use — and an mRNA vaccine that trains the body's immune cells to identify and attack those cells.

Earlier data from the Phase 2b trial (KEYNOTE-942), presented by the two companies at the 2026 American Society of Clinical Oncology (ASCO) annual meeting, showed that after five years of follow-up, the combination therapy reduced the risk of recurrence or death by 49 percent (HR=0.51) and the risk of distant metastasis or death by 59 percent (HR=0.411) compared with Keytruda alone. The Phase 3 trial confirmed consistent efficacy and safety in line with those findings.

Georgina Long, a professor at the Melanoma Institute Australia and a leading global authority on melanoma treatment, called it "the first Phase 3 trial to show that the combination of intismeran — designed around each patient's unique tumor mutational fingerprint — and pembrolizumab can reduce the risk of recurrence and death," adding that it "will open a new treatment paradigm that helps patients stay cancer-free for longer."

Moderna CEO Stéphane Bancel said creating an mRNA treatment tailored to each individual patient's cancer "has been a dream for years, and now it has become a reality."

The two companies are rapidly expanding the reach of personalized cancer vaccines through the INTerpath global clinical program, which encompasses nine Phase 2 and Phase 3 trials targeting a range of cancer types and stages — including non-small cell lung cancer (NSCLC), bladder cancer and renal cell carcinoma — beyond the initial melanoma indication.

In line with this global momentum, South Korea's pharmaceutical and biotech sector has also produced a notable research achievement in drug delivery systems (DDS) — a core technology for mRNA cancer vaccines.

Samyang Biopharm announced that a preclinical research paper on its proprietary gene delivery platform NanoReady, developed for use in mRNA cancer vaccines, has been selected as a cover paper in the Journal of Controlled Release, a leading international academic journal in the field of drug delivery and formulation technology.

NanoReady is one of the delivery platforms within SENS (Selectivity Enabling Nano Shell), a nanoparticle-based platform technology Samyang Biopharm developed in-house by combining proprietary lipids with biodegradable polymers. It is designed to selectively deliver mRNA to dendritic cells in the spleen, which play a central role in immune function.

NanoReady's key strengths are rapid manufacturing and high payload capacity. Because the delivery vehicle can be prepared and stored in advance without mRNA, a personalized cancer vaccine can be produced quickly and easily by simply mixing the vehicle with the patient-specific antigen mRNA once it becomes available.

Unlike conventional lipid nanoparticles (LNPs), NanoReady features a multilayered structure that allows it to carry approximately 20 times more mRNA per particle. This substantially amplifies the anticancer immune response of the T cells that attack cancer cells.

Building on this research, Samyang Biopharm plans to pursue publication of SENS delivery platform results for preventive vaccines and treatments for liver and lung diseases, while accelerating the expansion of its next-generation pipeline — including in vivo CAR-T therapies, central nervous system (CNS)-targeted treatments and novel RNA cargo applications.

A Samyang Biopharm official said NanoReady has been validated at the preclinical stage as a platform applicable to a wide range of mRNA drug candidates, going beyond the research phase, and that the company will "move in earnest to expand platform-based business, including developing our own mRNA cancer vaccines as well as global technology transfers and co-development of new drugs."