Cancer vaccines move from moonshot to medicine as first Phase 3 trial succeeds

In April 2024, Molly Hones was making peace with dying. The disease — stage 4 fibrolamellar carcinoma, a rare liver cancer — had invaded her bones and entered her bloodstream. Her doctors told her most chemotherapies wouldn't work. She was 31, and she had decided she'd rather spend her remaining six to 24 months living than enduring treatment. Her one concession to medicine was an offer to donate her body to science. Her doctors had a counteroffer: join a trial for an experimental cancer vaccine. She said yes. By the five-month mark, she had achieved full remission. She remains in remission today.

Hones's outcome is no longer an isolated anecdote. In August 2026, Moderna and Merck announced that a personalized mRNA cancer vaccine, combined with the immunotherapy Keytruda, had succeeded in a Phase 3 clinical trial — the final hurdle before a drug can seek FDA approval. No individualized neoantigen therapy had ever produced a positive Phase 3 result before, and no Phase 3 study had previously demonstrated a clinically meaningful benefit over Keytruda alone as post-surgery treatment for melanoma. Separately, a Washington University team reported that a personalized brain cancer vaccine had kept one patient tumor-free for nearly five years against a cancer that typically kills within 15 months.

Taken together, the results represent a shift in what researchers believe is possible. Cancer vaccines work differently from chemotherapy and radiation, which attack tumors directly but can damage healthy cells along the way. Rather than targeting tumors head-on, vaccines train the immune system to identify and eliminate cancer cells on its own — building a durable memory that may allow the body to continue fighting for years after treatment concludes.

I think that this is a moment where we really could make cancer curable by using cancer vaccines in addition to other therapies. I think we're about to change things profoundly for cancer patients.— Kristen Dahlgren, chief external affairs officer, Parker Institute for Cancer Immunotherapy

The Moderna-Merck trial, called INTerpath-001, brought in 1,137 patients who had undergone complete resection of stage 2B to 4 melanoma and had not yet received any systemic treatment. Two-thirds received the personalized vaccine — called intismeran autogene, also known as mRNA-4157 or V940 — alongside Keytruda; one-third received Keytruda alone. The combination met both its primary goal of recurrence-free survival and a key secondary goal of distant metastasis-free survival, with what the companies described as statistically significant and clinically meaningful improvements, according to CURE Today. The full data have yet to appear in a peer-reviewed journal; Merck and Moderna indicated they plan to share the findings at a forthcoming international medical meeting.

This is the first Phase 3 study to show that intismeran, a treatment designed based on the unique mutational 'fingerprint' of a patient's own tumor, given in combination with pembrolizumab can reduce the risk of recurrence or death in patients with completely resected stage IIB-IV melanoma compared to Keytruda alone.— Georgina Long, principal investigator, Melanoma Institute Australia

To build the vaccine, researchers sequence a sample of each patient's tumor, identify mutations specific to that cancer, and then synthesize an mRNA strand encoding up to 34 of those tumor markers — called neoantigens. Training the immune system to seek out and destroy cells bearing those same mutations is the central objective, while Keytruda broadens that immune assault against the cancer more generally, according to CURE Today. Phase 2b data presented at the 2026 ASCO Annual Meeting showed that over five years, the combination reduced the risk of recurrence or death by 49 percent and the risk of distant metastasis or death by 59 percent relative to Keytruda alone.

Among skin cancers, melanoma ranks among the most lethal. More than 330,000 new cases were diagnosed worldwide in 2022, and the U.S. is on track for roughly 112,000 new diagnoses and more than 8,500 deaths from melanoma in 2026, according to CURE Today. Even after successful surgery, patients remain at elevated risk of recurrence, particularly within the first two years.

The brain cancer results, from a Washington University School of Medicine team led by Dr. Tanner M. Johanns, tell a different but equally striking story. The cancer in question — grade four glioblastoma with an active MGMT gene — is among the hardest to treat in all of medicine. The MGMT switch lets the cancer repair the damage chemotherapy is supposed to inflict, leaving doctors with little beyond surgery and radiation for this subtype, according to Earth.com.

The WashU team built a personalized DNA vaccine called GNOS-PV01 from scratch for each of nine patients, sequencing multiple regions of each tumor — because glioblastoma is not uniform, with one corner carrying mutations another corner lacks — and loading in as many as 40 neoantigen targets per person. That doubled the number used in earlier brain cancer vaccines. All but one of the nine patients displayed a clear rise in immune activity following vaccination. At the six-month post-surgery mark, two-thirds of the group had experienced no cancer progression, and the same proportion remained alive at one year. For this subtype, roughly 40 percent of patients typically reach those marks, according to Earth.com. At two years, one-third of the group was still alive — double the rate history would predict.

Among the patients, one stands out: Kim Garland, a retired school nurse who learned at age 62, during the summer of 2021, that a scan had detected a brain mass roughly the size of a small avocado. Close to five years on, there is no indication the cancer has come back. Researchers found that immune cells trained against her tumor kept multiplying long after her shots ended, with a fresh surge arriving about two years out — suggesting the protection deepened over time rather than fading, according to Earth.com. That endurance addresses one of the field's central worries: that immune responses from brain cancer vaccines burn out before doing any lasting good.

The researchers also found that the vaccine appeared to change the tumor environment itself. When they examined tissue from patients whose tumors returned, immune cell levels inside the tumor had climbed sharply after treatment — a sign the vaccine was pulling immune cells into territory that had been nearly empty before. That finding raises the possibility of combining the vaccine with checkpoint inhibitor drugs, which have previously failed against glioblastoma, possibly because the tumor was too immunologically 'cold' for them to grip. Priming the tumor with a vaccine first could create the conditions those drugs need to take hold, according to Earth.com. The researchers caution the trial is too small to prove causation.

Back in the United States, patients like Ari Nakata illustrate both the promise and the current limits of the field. Two years after a breast cancer diagnosis, Nakata had completed chemo and radiation and her tumor marker tests showed no evidence of return — but her back suddenly gave out. Imaging showed the cancer had extended to her back, bones, lungs and liver. Unable to find what she needed online, she went directly to hospitals, met with doctors about clinical trial eligibility, and — because there was no system to transfer tissue samples between hospitals — packed dry ice and transported them herself. She eventually connected with the Parker Institute for Cancer Immunotherapy, which helped her enroll in a Washington University cancer vaccine trial, according to the New York Post.

The access problem is real and structural. For now, cancer vaccines are available only through clinical trials. Personalized vaccines cost over $100,000 each to manufacture, according to the New York Post, and researchers are working to streamline production to make them faster and more affordable. Not every cancer lends itself to the same approach: Hones's vaccine was 'off-the-shelf' — possible because fibrolamellar carcinoma almost always produces a specific abnormality across patients, allowing scientists to develop one vaccine that works for many. Most cancers are far less predictable, requiring the custom, DNA-sequencing approach that drives the cost up.

We're using the vaccines to prevent relapse in those patients at high risk of relapse. We're … trying to prevent the cancer from coming back.— Dr. Cathy Wu, cancer vaccine researcher, Dana-Farber Cancer Institute

Intismeran autogene is currently under investigation across nine Phase 2 and Phase 3 trials covering non-small cell lung, bladder, kidney, pancreatic and gastric cancers, according to CURE Today. If approved for melanoma — which could happen as early as next year, according to the New York Post — it would be the first personalized cancer vaccine to reach the market. For the estimated 18 million Americans living with or having survived cancer, that timeline is no longer abstract.

Why it matters — For the first time, a personalized cancer vaccine has cleared the final clinical trial threshold required for FDA approval, while separate trials show durable remissions in cancers previously considered near-untreatable — putting a new class of therapy within reach of millions of patients.

Reported by nypost.com, curetoday.com, earth.com