On September 30, 2026 Candel Therapeutics, Inc. (Candel or the Company) (Nasdaq: CADL), a clinical-stage biopharmaceutical company focused on developing multimodal immunotherapies to improve disease outcomes for patients with cancer, reported the presentation of new biomarker data from its completed phase 3 clinical trial of aglatimagene besadenovec (aglatimagene) in patients with localized intermediate- to high-risk prostate cancer at the American Society for Radiation Oncology (ASTRO) Annual Meeting 2026.

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The Company used digitized hematoxylin and eosin-stained prostate biopsy samples collected at baseline and after treatment with either aglatimagene or placebo, from patients who had completed the 3-injection course (n=647) in the randomized, placebo-controlled phase 3 study (NCT01436968). AI-enabled digital pathology analysis performed on tumor biopsies evaluable for digital analysis (622 pre-treatment and 427 post-treatment collected more than two years after completion of radiation), demonstrates that aglatimagene plus external beam radiation therapy (EBRT) significantly increased intratumoral lymphocyte infiltration and remodeled the tumor microenvironment compared with placebo plus EBRT. Among those patients with residual tumor, aglatimagene increased lymphocyte infiltration within tumor regions and enhanced lymphocyte-tumor engagement.

Key Highlights from ASTRO 2026 Presentation:

The Company previously reported that two years after treatment, 80% of evaluable aglatimagene patients (n=167) had negative prostate biopsies versus 63% of control patients (n=62) (p=0.0018)
Aglatimagene significantly increased overall lymphocytic fraction compared to control (p=0.048), with both arms showing immune activation from radiation therapy (p<0.001) (calculated in all digital-pathology evaluable biopsies; 622 pre-treatment biopsies and 427 post-treatment biopsies analyzed)
In paired biopsies from patients with residual tumor (n=108; aglatimagene n=62, control n=46), aglatimagene significantly increased intratumoral lymphocyte fraction (p=0.006), lymphocyte-tumor enrichment (p=0.003), and lymphocyte-tumor mixing (p<0.001)

"While radiation therapy alone drives immune infiltration into prostate tumors, these data support that aglatimagene produced a qualitatively distinct immune response," said Francesca Barone, M.D., Ph.D., Chief Scientific Officer of Candel Therapeutics. "The significantly greater lymphocyte infiltration and sustained lymphocyte-tumor engagement which we observed, more than two years after treatment, supports durable immune remodeling rather than transient inflammation. This mechanistic insight may help explain the clinical improvements in disease-free survival and pathologic outcomes we reported in the phase 3 trial."

"These tissue-level findings provide important biological support for the clinical benefit demonstrated in our phase 3 trial," said Paul Peter Tak, M.D., Ph.D., FMedSci, President and Chief Executive Officer of Candel. "We believe the convergence of sustained immune remodeling, improved pathologic response, and a clinically meaningful improvement in disease-free survival provides a compelling and coherent picture of aglatimagene’s activity in localized prostate cancer as we advance toward our planned Biologics License Application submission."

The data was presented by Dr. Barone during the Genitourinary Cancer session at ASTRO 2026 on September 29, 2026, and the poster is titled "Quantitative digital pathology defines immune activation following aglatimagene besadenovec immunotherapy in localized prostate cancer" (Abstract LBA 30).

About aglatimagene besadenovec

Aglatimagene besadenovec (aglatimagene), Candel’s most advanced multimodal biological immunotherapy candidate, is an investigational, off-the-shelf, replication-defective adenovirus designed to deliver the herpes simplex virus thymidine kinase (HSV-tk) gene to a patient’s tumor. After intratumoral administration, HSV-tk enzyme activity results in conversion of prodrug (valacyclovir) into deoxyribonucleic acid (DNA)-incorporating nucleotide analogs, leading to immunogenic cell death in cells exhibiting DNA damage and proliferating cells, with subsequent release of a variety of tumor (neo)antigens in the tumor microenvironment. At the same time, the adenoviral serotype 5 capsid proteins promote inflammation through the induction of expression of pro-inflammatory cytokines, chemokines, and adhesion molecules. Together, this regimen is designed to induce an individualized and specific CD8+ T cell-mediated response against the injected tumor and uninjected distant metastases for broad anti-tumor activity, based on in situ immunization against a variety of tumor antigens. Aglatimagene has the potential to treat a broad range of solid tumors. Encouraging monotherapy activity as well as combination activity with standard of care radiotherapy, surgery, chemotherapy, and immune checkpoint inhibitors have previously been shown in several nonclinical and clinical settings. More than 1,000 patients have been dosed with aglatimagene in clinical trials with a favorable tolerability profile to date, supporting the potential for use with standard of care, when indicated. Aglatimagene is currently not approved by the U.S. Food and Drug Administration (FDA) or any other regulatory authority for any use.

(Press release, Candel Therapeutics, SEP 30, 2026, View Source [SID1234671192])