In a single-arm phase 1/2 clinical trial involving patients with EGFR-mutant NSCLC and leptomeningeal metastases who had previously failed tyrosine kinase inhibitors, the administration of intrathecal (IT) Pemetrexed with dexamethasone demonstrated a noteworthy clinical response rate of 84.6%. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.