A vaccine manufacturer has said it is terminating a clinical trial testing an experimental vaccine against cancer.
The vaccine, which utilizes messenger ribonucleic acid (mRNA) technology, is made by BioNTech in partnership with Genentech. The vaccine was being tested in patients with colorectal cancer in a phase 2 clinical trial.
Experts on a board monitoring the trial recommended the trial be halted because there was “a numerical imbalance in overall survival between treatment arms,” BioNTech said in an Aug. 28 statement.
Signs of trial failure became evident in October 2025, but the experts said that at the time the “data were not were not sufficiently mature to support reliable conclusions regarding efficacy, and that follow-up time was insufficient to evaluate the trial’s primary endpoint,” according to BioNTech, so the trial continued.
Continuing the trial further is unlikely to change the outcome, the experts assessed. BioNTech, after consulting with Genentech, agreed to end the trial and discontinue treatment of the patients. It said it has updated regulators.
“Any decision concerning clinical trials is made with utmost care, keeping patients as our highest priority,” Dr. Ozlem Tureci, BioNTech’s chief medical officer and a co-founder of the company, said in a statement.
“While this outcome is not what we had envisioned for mRNA as a monotherapy in colorectal cancer, it provides scientific insight into the challenges of treating immunotherapy-insensitive tumor types with immune-suppressive microenvironments and will help inform the further development of investigational mRNA cancer immunotherapies.
“We remain committed to mRNA as a key pillar in our oncology strategy and our novel-novel combination approaches. We are deeply grateful to the patients, families, investigators and site teams whose participation has made this important research possible.”
The open-label trial was estimated to enroll about 327 patients.
The post-trial procedure will include evaluating how patients were selected, with an eye toward influencing BioNTech’s approach to potential additional mRNA cancer vaccines, according to BioNTech.
A second trial investigating the safety and efficacy of the vaccine, autogene cevumeran, in combination with another drug regimen and involving patients with pancreatic cancer, has an estimated enrollment of 260 patients and is ongoing.
Several COVID-19 vaccines—one from BioNTech and Pfizer and one from Moderna—in 2020 became the first mRNA vaccines cleared by regulators in various countries. Since then, mRNA vaccines against multiple other viruses, such as respiratory syncytial virus, have been approved.
Moderna and Merck announced earlier in August that data from a phase 3 trial of a skin cancer vaccine they developed showed it performed well. The companies said they would pursue regulatory clearance for the shot.