Abstract BACKGROUND Neoplastic meningitis (NM) is an increasingly frequent, profoundly morbid, and almost invariably fatal complication of solid and hematologic malignancies. Despite multimodal therapy, median survival in randomized trials is approximately 4 months. Biologic agents are widely utilized in management of extra-CSF disease, but often have limited ability to penetrate the CSF. Intra-CSF administration of biologic agents has not been widely investigated. We describe the safety and efficacy of tumor-specific, intra-CSF biologic therapy in a large group of patients with neoplastic meningitis. MATERIAL AND METHODS We queried the database of a large, international neoplastic meningitis registry (NeMeRe) to identify patients with neoplastic meningitis who received at least one dose of neoplastic meningitis-directed therapy with a biologic agent. Detailed patient demographic, treatment, toxicity and outcome data was extracted and analyzed for the first 140 consecutive patients treated at our institution. RESULTS These 140 patients received an intrathecal biologic agent as part of a histology- and molecular profile-directed intraventricular chemotherapy treatment approach. Agents included rituximab (58 patients with lymphoma, 224 cycles), trastuzumab (42 patients with malignant primary brain tumors, 211 cycles; 15 patients with breast cancer, 149 cycles; 1 patient with esophageal cancer, 9 cycles), panitumumab (4 patients with lung cancer, 9 cycles), nivolumab (1 patient with melanoma, 5 cycles; 2 patients with breast cancer, 2 cycles; 2 patients with GBM 12 cycles; 2 patients with lung cancer, 4 cycles; 2 patients with gastric adenocarcinoma, 17 cycles; 2 patients with renal clear cell carcinoma, 17 cycles; 1 patient with AML, 2 cycles; 1 patient with multiple myeloma, 8 cycles) and alpha-interferon (10 patients with melanoma, 31 cycles; 2 patients with renal clear cell carcinoma, 18 cycles). Grade I/II toxicity occurred in 5.8% of rituximab, 3.2% of trastuzumab, 0% of panitumumab, 16.3% of nivolumab, and 3.2% of alpha-interferon containing cycles. There was no grade III toxicity. Median survivals in patients with lymphomatous meningitis (304 days), solid tumor NM from primary brain tumors (243 days), HER2 -positive breast cancer (not reached, >315 days), lung cancer (192 days), and melanoma (307 days) were encouraging. No difference in survival was seen between patients with and without treatment-related toxicity in any histologic group. CONCLUSION This large registry-based cohort study suggests that rituximab, trastuzumab, panitumumab, nivolumab, and alpha interferon may be safely administered into the CSF as part of a multi-agent intra-CSF treatment regimen. Survival, while very tentative, is encouraging. A prospective, multi-center evaluation of these agents in patients with neoplastic meningitis is warranted.