Phase 3 melanoma vaccine cuts recurrence or death risk by 42%

By Sophie Lindqvist

In the phase 3 INTerpath-001 trial, adding intismeran to pembrolizumab reduced the risk of recurrence or death by 42% in patients with advanced melanoma.

Pharmaceutical developers Merck and Moderna released the phase 3 results early, and the sponsor-reported analysis exceeded expectations for the primary endpoint of recurrence-free survival.

Amy Walker, molecular biologist, chief executive officer of synthetic DNA supplier 4basebio and European chair of the Alliance for mRNA Medicines, called the late-stage data impressive and incredible. She said the evidence brought conviction across the field that the science works.

INTerpath-001 enrolled more than 1,000 patients with advanced melanoma. Investigators surgically resected their tumors before patients received either intismeran plus pembrolizumab, the current standard-of-care immunotherapy, or pembrolizumab alone.

The primary recurrence-free survival result was statistically significant and clinically meaningful. The secondary endpoint also favored combination treatment: the risk of distant metastasis or death fell by 38%. The company analysis put two-year recurrence-free survival at 82% with the combination, compared with 70% on pembrolizumab alone.

What does this change for melanoma care?

INTerpath-001 is the first phase 3 trial to show that a new drug combined with pembrolizumab performs better than pembrolizumab alone. For melanoma teams, the practical change is a phase 3-tested postoperative treatment strategy built around each tumor’s mutations, rather than pembrolizumab alone. The finding does not establish the same effect in other cancers.

“The Phase 3 INTerpath-001 data is a real milestone for personalized cancer vaccines,” Walker wrote. “A 42 percent reduction in the risk of recurrence or death is meaningful, alongside raising two-year recurrence-free survival from 70 percent to 82 percent against [pembrolizumab] alone.”

She called the findings the strongest evidence yet that mRNA neoantigen vaccines can improve melanoma outcomes. She also expected the sponsors’ expanding dataset to make the vaccines more potent by improving the algorithms that identify neoantigens.

From tumor DNA to a patient-specific vaccine

Each intismeran treatment starts with the patient’s own tumor DNA rather than a fixed antigen shared across patients. The process has three distinct steps:

• Scientists sequence the DNA of each patient’s cancer.
• They identify mutations in the tumor genome that code for neoantigens, new proteins that appear on the tumor surface because of those specific mutations.
• They design an mRNA sequence that produces those neoantigens as a vaccine, training the patient’s immune system to recognize the cancer as non-self and eliminate it.

Walker said melanoma was a sensible indication because its tumors vary substantially. She reasoned that this variability creates a high likelihood of finding immunogenic tumor targets, unlike a “cold” solid tumor that may provoke a weaker immune response.

Why mRNA may scale more easily

Manufacturing problems and lackluster clinical results have held cancer vaccines back, Walker said. Vaccines based on DNA, peptides and viruses can involve convoluted production and high costs, whereas she sees mRNA as a more practical route for personalized medicines.

Her argument rests on speed and definition: mRNA production takes a couple of enzymatic steps over a couple of hours. She described the process as straightforward, well defined from a critical-quality-attribute standpoint, higher throughput and, in her view, potentially cheaper than other personalized vaccine platforms.

Why the BioNTech result is not a direct comparison

A separate, more recent BioNTech announcement supplies a counterpoint: its mRNA vaccine for head and neck squamous cell carcinoma missed the primary progression-free survival endpoint in a phase 2/3 trial. Walker cautioned against treating that outcome as a direct counterexample to intismeran.

She said head and neck cancer is not an easy malignancy and that the BioNTech product was not personalized, so the trials do not offer an apples-to-apples comparison. The distinction matters because intismeran targets mutations found in an individual tumor.

What happens next

Walker expects the intismeran findings to draw funding from biotech and academic groups and to sustain momentum for mRNA cancer vaccines. She also reported significantly increased interest in 4basebio’s synthetic DNA templates designed for personalized cancer vaccines.

Longer term, accumulating data may support less bespoke products aimed at the most common neoantigens. Such off-the-shelf treatments would simplify manufacturing compared with producing a separate therapy for every patient.

“We, collectively as an industry, don't need to think about how we need to make the science work [anymore],” Walker remarked. “It's actually how we scale such individualized therapies to be able to treat the masses.”

For melanoma clinicians, INTerpath-001 now provides phase 3 efficacy evidence for an individualized mRNA vaccine. The next constraints are manufacturing scale, development of common-target products and whether the approach reproduces its benefit in other cancers.