RecruitingPhase 1Drug trialIntrathecal Application of PD1 Antibody in Metastatic Solid Tumors With Leptomeningeal Disease (IT-PD1/ NOA 26)To determine the safety of intrathecal (IT) PD1 antibody for Intrathecal application of PD1 antibody in metastatic solid tumors with leptomeningeal disease of solid tumors.