Aglatimagene besadenovec (CAN-2409) combined with the oral prodrug valacyclovir and standard-of-care (SOC) external beam radiation therapy (EBRT) produced a statistically significant improvement in prostate cancer-specific disease-free survival (DFS) vs placebo plus prodrug and EBRT in patients with intermediate- to high-risk localized prostate cancer, with benefits continuing to accumulate through extended follow-up, according to data from the phase 3 PrTK03 trial (NCT01436968) presented during the 2026 American Urological Association (AUA) Annual Meeting.1
At a median follow-up of 58.0 months (95% CI, 56.6-60.2), the prostate cancer-specific DFS HR in the intention-to-treat (ITT) population (n = 745) was 0.61 (95% CI, 0.44-0.85; P = .0031), representing a 39% improvement in prostate cancer–specific DFS with aglatimagene besadenovec compared with placebo plus SOC. Two deaths due to prostate cancer, 1 in each arm, were reported.
“The most notable [outcome from this study] was that that there was an [approximately] 40% lower chance of having cancer at follow-up if a patient was treated with aglatimagene besadenovec compared with placebo. That number translates into real-world benefits for these patients,” Mark Garzotto, MD, a professor of urology in the School of Medicine at Oregon Health & Science University in Portland, said in an exclusive interview with OncLive®.
Key Takeaways From the Extended Follow-Up of PrTK03
- At a median follow-up of 58.0 months (95% CI, 56.6-60.2), the prostate cancer-specific DFS HR in the ITT population (n = 745) was 0.61 (95% CI, 0.44-0.85; P = .0031), representing a 39% improvement in prostate cancer–specific DFS with aglatimagene besadenovec compared with placebo plus SOC.
- The HR for time to new anticancer therapy was 0.72 (95% CI, 0.39-1.31), and for time to biochemical failure (nadir +2), the HR was 0.72 (95% CI, 0.40-1.31), both favoring the aglatimagene arm.
- No grade 4 or higher treatment-related AEs occurred in either arm.
How was PrTK03 designed?
The randomized, placebo-controlled phase 3 trial enrolled 745 patients with newly diagnosed, intermediate- or high-risk localized prostate cancer.1,2 Patients were randomly assigned 2:1 to aglatimagene besadenovec plus valacyclovir (n = 496) or placebo plus valacyclovir (n = 249), each in combination with EBRT with or without short-course androgen deprivation therapy (ADT). The trial was conducted under a Special Protocol Assessment agreement with the FDA. Random assignment was stratified by NCCN risk group and planned short-course ADT use.
The primary end point was DFS. Key secondary end points included PSA freedom from biochemical failure, prostate cancer-specific outcomes, and overall survival (OS).1
At baseline in the ITT population, median age was 69 years. The majority of patients had intermediate-risk disease (85.2%), Gleason score of 7 (85.1%), and a median PSA of 6.7 ng/mL (range, 0.8–63.3). Approximately half of patients in each arm had planned ADT (49.1% overall).
What did the extended follow-up efficacy data show?
In terms of time to new anticancer therapy, the HR was 0.72 (95% CI, 0.39-1.31), and for time to biochemical failure (nadir +2), the HR was 0.72 (95% CI, 0.40-1.31), both favoring the aglatimagene arm. Time to metastasis showed an HR of 0.58 (95% CI, 0.21-1.59), with a lower rate of metastatic events in the aglatimagene arm (1.6%) compared with placebo (2.8%).
In the prespecified intermediate-risk subgroup (n = 635), the prostate cancer-specific DFS benefit was 41% (HR, 0.59; 95% CI, 0.41-0.84; P = .0034). Time to new anticancer therapy (HR, 0.51; 95% CI, 0.24-1.1) and time to biochemical failure (HR, 0.48; 95% CI, 0.22-1.03) trended in favor of aglatimagene. The time-to-metastasis benefit was most striking in this subgroup, with an HR of 0.10 (95% CI, 0.01-0.85) and absolute rates of 0.24% (n = 1 of 422) vs 2.35% (n = 5 of 213) in the aglatimagene and placebo arms, respectively.
What were the safety data?
The most common adverse effects (AEs) in the aglatimagene arm included chills (33.4%), influenza-like illness (30.5%), and fever (25.1%). No grade 4 or higher treatment-related AEs occurred in either arm. Serious AEs (5.8% vs 7.3%) and AEs leading to treatment discontinuation (5.4% vs 6.0%) were reported in the investigational and placebo arms. Treatment related serious AEs occurred at respective rates of 1.7% and 2.2%.
“The AEs that were noted were mostly low-grade and self-limited, including fever, chills, and flu-like symptoms, but there were no new safety signals, and there was no grade 4 or higher treatment-related AEs,” Garzotto said.
Disclosures: Garzotto has served as a clinical trial investigator for Astellas Pharma, Candel Therapeutics, Merck & Co., and Pfizer. He also served as a consultant to Candel Therapeutics.
References
- Garzotto M, Sylvester J, Wheeler T, et al. Extended follow-up shows accumulating benefit for patients treated with CAN-2409+prodrug in combination with standard of care external beam radiation (EBRT) in men with localized prostate cancer: update from a randomized placebo-controlled phase 3 clinical trial. J Urol. 2026;215(552):e1. doi:10.1097/01.JU.0001192572.07890.f8.01
- Phase 3 study of ProstAtak immunotherapy with standard radiation therapy for localized prostate cancer (PrTK03). ClinicalTrials.gov. Updated July 30, 2025. Accessed June 4, 2026. https://clinicaltrials.gov/study/NCT01436968
