Adenoviral immunotherapy improves disease-free survival in prostate cancer trial

A gene therapy built from a modified adenovirus has moved a step closer to prostate cancer care, after a large phase 3 trial showed better disease-free survival in men with localized intermediate- or high-risk disease. The result points to a possible new way to keep early prostate cancer under control, but it stops short of proving longer life, fewer side effects over time or a clear place in routine practice.

The treatment, aglatimagene besadenovec, also known as aglatimagene or CAN-2409, was given as an intratumoral adenoviral gene therapy with valacyclovir and standard radiotherapy. In the randomized, double-blind, placebo-controlled multicenter study, 745 men were enrolled at 51 medical centers across the United States and Puerto Rico. The Lancet Oncology published the phase 3 results on June 1, 2026, reporting that the addition of aglatimagene plus valacyclovir improved disease-free survival versus placebo plus valacyclovir without increasing clinically significant toxicity.

That matters because localized prostate cancer still leaves many men facing recurrence even after curative-intent radiotherapy. Trial background cited a recurrence rate of around 30% in that setting, which is why an immune-based strategy aimed at earlier disease has drawn attention. Reuters and Medscape reported the finding on June 18, describing the benefit as about 30% while noting that experts still had reservations about how far the result can be carried.

Those reservations are central. Disease-free survival is an important signal, but it is not the same as showing that men live longer or live better. Larger questions remain about whether the treatment changes metastasis-free survival, overall survival, side-effect burden over longer follow-up, how durable the benefit will be, and where an added immunotherapy would fit alongside surgery, radiation, hormone therapy or other systemic approaches. Cost and access would also matter if the therapy advances toward broad use.

Candel Therapeutics said the data would support a planned Biologics License Application submission in the fourth quarter of 2026. The company also reported extended follow-up in May showing a 39% improvement in prostate cancer-specific disease-free survival at a median follow-up of 58 months. Johns Hopkins researchers involved in the work said the therapy could become the first new treatment for localized prostate cancer in more than 20 years if it is ultimately approved, but the next tests will have to show that the early disease-control signal translates into lasting clinical benefit.