CTIM-32. IMMUNE CHECKPOINT INHIBITOR NIVOLUMAB IN PEOPLE WITH RECURRENT SELECT RARE CNS CANCERS: RESULTS OF INTERIM ANALYSIS IN A HEAVILY PRETREATED COHORT Free

Standard and experimental therapies for patients with rare CNS tumors are scarce. Nivolumab (PD-1 inhibitor) is approved for several non-CNS cancers. This ongoing Phase II trial (NCT03173950) will determine the efficacy of nivolumab in adults with recurrence/progression of one of 11 selected rare primary CNS tumors. Efficacy is measured by Disease Control Rate (DCR; confirmed CR/PR or durable SD for ≥ 6 months) in 2 cohorts: heavily and non-heavily pretreated patients (heavily pretreated: ≥ 3 prior therapies; non-heavily pretreated: ≤ 2). We report efficacy and safety results of a preplanned interim analysis in the heavily pretreated cohort.

Eligibility includes recurrence/progression of an eligible tumor; age ≥ 18 years; tumor tissue available for histopathology, molecular and immune profiling; KPS ≥ 70; and no steroids at study entry. A total of 150 evaluable patients will be enrolled (75 to each cohort). Prior therapies include radiation and/or standard or investigational drugs. Nivolumab treatment is 240 mg IV every 2 weeks (4 doses); then 480 mg every 4 weeks (14 additional doses). Interim analysis was planned when sample size reached 32 in each cohort.

As of March 10, 2021, DCR exceeded the minimum required for interim analysis in the heavily pretreated cohort. Among 30 patients, 4 achieved SD > 6 months (medulloblastoma, anaplastic ependymoma, myxopapillary ependymoma, metastatic atypical meningioma). Safety profile (related AEs): grade 3 = 7; grade 4 = 1. Most frequent grade 3-5 AEs regardless of attribution: tumor progression (6); anemia, hydrocephalus, lymphopenia (3 each); cerebral edema, headache (2 each).

DCR exceeded the “go” boundary (i.e., > 2) in the heavily pretreated cohort. Nivolumab showed safety profile consistent with other studies. This cohort will continue to stage 2 and complete total accrual of 75 patients. The trial is currently being expanded to 10 additional sites across the BTTC/NCI-CONNECT consortium.