Opening a New Line of Attack Against Prostate Cancer
A new treatment that activates the body’s own immune system to attack prostate tumors is showing promise in early clinical trials, representing a major step forward in treating some of the most difficult forms of prostate cancer.
The findings, presented at the 2025 American Society of Clinical Oncology (ASCO) annual meeting and published in the Journal of Clinical Oncology, suggest the treatment could help patients with advanced prostate cancer that no longer responds to standard therapies.
“The study started as a dose escalation study, to try and find the right dose for future clinical trials,” says Mark Stein, MD, associate professor of medical oncology at Columbia University Vagelos College of Physicians and Surgeons and member of the Herbert Irving Comprehensive Cancer Center (HICCC). He and a large international team of collaborators were primarily looking for signs of toxicity and side effects of the treatment. “However,” he adds “what we saw was very encouraging signs of effectiveness—even at lower doses”
The trial enrolled patients with metastatic castration-resistant prostate cancer, a particularly aggressive form of cancer, which earlier treatments had failed to stop. On the new drug, pasritamig, many of these late-stage patients saw their tumors shrink and had a median progression-free survival of nearly eight months.
Pasritamig works by bridging the body’s T cells—immune cells that fight infections and cancer—to prostate cancer cells. It does this using a specially designed antibody that binds to a protein found only on prostate cancer cells and a receptor on T cells, helping the immune system recognize and attack tumors.
Researchers were also surprised to find that the most effective dose wasn’t the highest one. “With immune therapies like this, more is not always better,” says Stein. “Too high a dose can overstimulate the immune system, which may reduce effectiveness.” In this study, the best approach turned out to be a moderate dose given as an IV infusion every six weeks.
Immune-stimulating drugs often have side effects, and pasritamig is no exception. Stein and his colleagues were especially watching for a phenomenon called cytokine release syndrome, which can cause a concerning loss of blood pressure. But in this case, the drug caused only minimal side effects. “When we gave it IV, the cytokine release was what we call grade one—minimally bothersome,” says Dr. Stein. No patients stopped treatment because of side effects, and at the recommended dose for phase II trials, the only sign of cytokine release was a mild fever. In fact, 40% of patients didn’t experience any side effects at all.
This, combined with the six-week dosing schedule, could make the new treatment much easier on patients. “This could be delivered in an outpatient setting, sparing patients frequent hospital visits and precious time away from family” says Stein. He adds that “it also means that you can give this not only in a big academic medical center, but potentially in more places.”
The research team, in collaboration with the drug’s manufacturer Johnson & Johnson, is now enrolling patients in a larger clinical trial to further evaluate the drug’s effectiveness and safety.
They also plan to look at ways to improve the treatment. Stein says future studies may explore using it earlier in the disease course or combining it with other treatments. “We’re just at the beginning of what might be possible with this type of approach,” he says.
