Exploration of the Application of Methotrexate-loaded Drug Vesicles in Intrathecal Injection for Meningeal Metastasis of Lung Cancer

This is a phase I/II, single-arm, open-label, single-center clinical trial to evaluate the safety, tolerability, and preliminary efficacy of intrathecal injection of methotrexate-loaded autologous tumor cell-derived microparticles (MTX-MPs) in patients with leptomeningeal metastasis from lung cancer who have failed standard of care. The study consists of two phases: Phase I employs an accelerated titration combined with a "3+3" dose-escalation design to determine the maximum tolerated dose (MTD) and the recommended phase II dose (RP2D). Phase II further assesses the objective response rate (ORR) at the RP2D. Key secondary endpoints include progression-free survival (PFS), overall survival (OS), and safety profile. Approximately 10-20 patients with cytologically confirmed leptomeningeal metastasis (age ≥18 years, ECOG PS 0-3) will be enrolled. Participants will receive intrathecal MTX-MPs on days 1, 3, and 5 of the first cycle, followed by once every 3 weeks (Q3W) until disease progression, unacceptable toxicity, or death. Tumor response will be evaluated using the Response Assessment in Neuro-Oncology (RANO) criteria for leptomeningeal metastasis, and adverse events will be graded according to CTCAE version 5.0. This exploratory study may provide a novel local therapeutic approach for leptomeningeal metastasis from lung cancer.