Aglatimagene Besadenovec Shows Durable Immune Activity in Intermediate-Risk Localized Prostate Cancer

Aglatimagene besadenovec (CAN-2409) plus external beam radiation therapy (EBRT) was associated with improved prostate cancer–specific disease-free survival and evidence of sustained immune activity in patients with intermediate-risk localized prostate cancer, according to clinical and biomarker analyses from the phase 3 PrTK03 trial (NCT01436968) and phase 2 PrTK05 study (NCT07332000).¹

Findings from PrTK03 showed that in patients with intermediate-risk disease, the combination reduced the risk of recurrence or prostate cancer–specific death by 41% vs placebo plus EBRT after a median follow-up of 58.0 months (HR, 0.59; 95% CI, 0.41-0.84; P = .0034). Additionally, exploratory analyses in the intermediate-risk subgroup favored aglatimagene besadenovec in regard to time to biochemical failure (HR, 0.48; 95% CI, 0.22-1.03), time to metastasis (HR, 0.10; 95% CI, 0.01-0.85), and time to salvage anticancer therapy (HR, 0.51; 95% CI, 0.24-1.10).

Among patients enrolled in PrTK03 who had evaluable prostate biopsies obtained 22 to 26 months after treatment (n = 277), 76.6% of patients in the aglatimagene besadenovec arm (n = 188) had negative biopsies vs 60.7% in the control arm (n = 89). Exploratory digital pathology analysis of 98 paired biopsies with detectable tumor after treatment also found a higher intratumoral lymphocyte fraction with aglatimagene besadenovec (P = .002).

In PrTK05, serial blood samples from patients receiving aglatimagene besadenovec plus EBRT (n = 13) and those receiving standard-of-care EBRT alone (n = 6) showed expansion of several circulating CD8-positive T-cell populations in the aglatimagene group, including proliferating and cytotoxic cells.

“The evidence of systemic immune activation in intermediate-risk prostate cancer strengthens the biological rationale for evaluating aglatimagene [besadenovec] in metastatic solid tumor settings where systemic disease control is critical. These findings underscore the broader potential of our multimodal immunotherapy platform,” Paul Peter Tak, MD, PhD, FMedSci, president and chief executive officer of Candel Therapeutics, stated in a news release.

The company plans to present the integrated data at a future scientific meeting. Additionally, data from PrTK05 will be integrated into a biologics license application seeking the approval of aglatimagene besadenovec, which the company intends to submit to the FDA in the fourth quarter of 2026.

What was the design of PrTK03 and who was eligible?

PrTK03 was a randomized, double-blind, placebo-controlled phase 3 trial that enrolled men with newly diagnosed intermediate or high-risk localized prostate cancer.² Eligible patients were at least 18 years of age with histologically confirmed prostate adenocarcinoma meeting intermediate-risk criteria or one high-risk criterion, who had an ECOG performance status of 0 to 2 and planned to undergo prostate-only EBRT. The intermediate-risk subgroup comprised 635 patients, or 85% of the trial’s intention-to-treat population.¹

Patients were randomly assigned 2:1 to receive 3 courses of intraprostatic aglatimagene besadenovec plus oral valacyclovir and EBRT, with or without androgen deprivation therapy (ADT); or placebo plus valacyclovir and EBRT, with or without ADT.²

The primary end point of PrTK03 was disease-free survival (DFS) in the full intention-to-treat population, measured from randomization to prostate cancer recurrence or death from any cause. Secondary end points included prostate cancer–specific DFS, prostate-specific antigen outcomes, overall survival, immune stimulation, and quality of life. The newly reported clinical analysis focused on prostate cancer–specific DFSin the intermediate-risk subgroup; the release describes its additional time-to-event findings as exploratory and descriptive.

References

1. Candel Therapeutics announces integrated clinical and biomarker data that showed durable local and systemic immune activation after aglatimagene besadenovec in intermediate-risk localized prostate cancer. News release. Candel Therapeutics. September 30, 2026. Accessed September 30, 2026. https://ir.candeltx.com/news-releases/news-release-details/candel-therapeutics-announces-integrated-clinical-and-biomarker
2. Phase 3 study of ProstAtak immunotherapy with standard radiation therapy for localized prostate cancer. ClinicalTrials.gov. NCT01436968. Accessed September 30, 2026. https://clinicaltrials.gov/study/NCT01436968