Cancer of the prostate is the most common type of cancer in men in many countries. (symbol image)Image: www.imago-images.de
A new drug against prostate cancer shows promising results in an early study: PSA levels fell and the tumor was even shrunk.
February 28, 2026, 2:48 p.mFebruary 28, 2026, 2:48 p.m
Annika Danielmeier / watson.de
Prostate cancer is the most commonly diagnosed cancer among men in many countries. Prostate cancer is considered “immune-cold,” says Prof. Johann de Bono from the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust. Until now it was considered resistant to immunotherapy. The results of a new study could change that.
Accordingly, the immunotherapy VIR-5500 offers hope for advanced prostate cancer: in some patients it has caused the tumor to shrink.
Immunotherapy minimizes side effects
Immunotherapy uses the body’s own immune system to fight disease. The drug VIR-5500 is a so-called T cell engager that connects the immune system’s killer T cells with tumor cells that try to evade the immune system.
“We believe that such treatments could lead to long-term cures,” says Prof. Johann de Bono, who led the study Guardian.
A special feature of VIR-5500 is that the drug was developed so that it is only activated within the tumor. According to de Bono, one advantage of this is that it reduces side effects for the patient – other T cell engagers, however, can trigger severe inflammatory reactions.
In addition, VIR-5500 stays in the bloodstream longer, so the patient may need fewer doses of the drug.
In the Phase 1 trial, 58 men with advanced prostate cancer who had stopped responding to other treatments received the drug. The majority of patients (88 percent) reported only very mild side effects.
Drug shows promising results
The study also delivered promising results with regard to the tumor itself. The researchers examined the PSA levels, which is the prostate-specific antigen in the patients’ blood. An elevated value can indicate prostate problems.
De Bono reports that of 17 men who received the highest dose, 14 of them saw their PSA levels drop by at least half. In nine patients the value fell by at least 90 percent; with five even by at least 99 percent.
Successes were also seen in patients who had already developed a measurable tumor. Eleven of them were given the maximum dose of the drug: in five, the tumor shrank as a result of the immunotherapy.
De Bono explained that further clinical trials are planned. “We still need more data, but the results are amazing,” he says. The results have not yet been peer-reviewed, but experts described the results from this early phase of the study as (potentially) promising, according to the Guardian.