TRLS-11. PNOC005: ONCOLYTIC MEASLES VIRUS FOR THE TREATMENT OF CHILDREN AND YOUNG ADULTS WITH RECURRENT MEDULLOBLASTOMA OR ATYPICAL TERATOID RHABDOID TUMOR

Abstract BACKGROUND PNOC005 is a phase 1 clinical trial investigating the safety and tolerability of intratumoral or intrathecal administration of oncolytic measles virus (MV-NIS) in children and young adults with recurrent medulloblastoma (MB) or atypical teratoid/rhabdoid tumor (ATRT). METHODS Patients with recurrence of MB or ATRT were stratified into Stratum A (local recurrence) or B (disseminated recurrence). Stratum A patients received MV-NIS directly into the tumor bed at time of surgical resection. Stratum B patients received a single dose of MV-NIS via lumbar puncture. After safety was demonstrated in Stratum A and B, Stratum C was added with repeat dosing on Day 0 and 7 for patients with recurrent disseminated MB. Specimens for viral shedding were collected. Blood was collected on days 0, 4, 7, 14, and 28. RNA-sequencing deconvolution and time-series analysis were performed to estimate the composition and phenotypes of peripheral blood mononuclear cells (PBMCs). RESULTS Thirty-four patients (median age 8.5, range 2-31) enrolled between February 2017 and April 2021, with 23 evaluable patients with MB and 4 with ATRT. One patient experienced a dose-limiting toxicity (grade 3 alanine aminotransferase increase). There were four MV-NIS-related adverse events grade 3 or greater across all strata. Viral shedding was detected in 5 patients, all of which cleared by end-of-treatment. We found a similar gene-expression program in PMBCs that correlated across patients (n=18), which was upregulated at days 4-7 post treatment and consistent with an antiviral response. Concomitant changes in B, T, and natural-killer cell composition and activation were consistent with this interpretation. CONCLUSION This is the first trial investigating intratumoral as well as repeated intrathecal delivery of MV-NIS in children with MB and ATRT. We show that therapy is safe and well-tolerated with minimal adverse effects. Immune markers and biologic correlates preliminarily indicate anti-viral effects in tumors.