SAFETY, EFFICACY, AND SURVIVAL RESULTS FROM A PHASE 1 STUDY OF THE ONCOLYTIC ADENOVIRUS DNX-2401 FOLLOWED BY STANDARD OF CARE RADIOTHERAPY FOR NEWLY DIAGNOSED DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)

Abstract BACKGROUND Diffuse intrinsic pontine glioma (DIPG) is the most lethal pediatric brain tumor. Median overall survival (OS) with standard of care radiation therapy (RT) is approximately 8-10 months and 2-year survival is < 10%. A Phase 1 single-center study was conducted to evaluate the oncolytic adenovirus, DNX-2401 (tasadenoturev), followed by RT for DIPG. METHODS Newly-diagnosed DIPG patients 1-18 years old received a tumor biopsy through the cerebellar peduncle followed by intratumoral injection of 1e10 – 5e10 vp DNX-2401 and conventional RT 1-3 weeks later. RESULTS Subjects were enrolled (n=12) from December 2017 to January 2020 and had a median age of 9 years (range 3-18) and Lansky/Karnofsky performance scores of 90-100 (n=4; 33%) or 70-80 (n=8; 67%). Genetic assessment was completed for 11 subjects (92%) and histone 3 K27M mutations were identified in 10 subjects, including H3F3A (n=8), HIST2H3C (n=1), and HIST1H3B (n=1); 1 subject was H3 wildtype (n=1). TP53 mutations were identified in 5 subjects (42%). DNX-2401 was administered followed by RT (n=11; 92%). No dose-limiting toxicities were observed and the treatment regimen was well-tolerated. The most commonly reported adverse events (≥ 5 subjects), regardless of study drug relationship, include asthenia, headache, vomiting, pyrexia, and neurological deterioration. Three serious adverse events were reported including grade 3 abdominal pain, grade 3 lymphopenia, and grade 3 clinical deterioration. Tumor reductions were reported for 9 subjects (75%), including 2 confirmed (17%) and 2 unconfirmed (17%) responses per RAPNO criteria. As of the data cutoff, median OS is 19.7 months and OS-24 is 32% with follow-up ongoing for 3 subjects (26.9, 25.6, 13.7 months). CONCLUSIONS DNX-2401 followed by RT can be safely administered to DIPG. Survival outcomes are encouraging, thus warranting further evaluation in a Phase 2 study.