Cladribine is primarily used in the treatment of certain types of cancer and autoimmune diseases. It is particularly effective in managing hairy cell leukemia, a rare form of blood cancer, where it works by selectively targeting and destroying cancerous B-cells. Additionally, cladribine is used in treating relapsing forms of multiple sclerosis (MS) to reduce the frequency of clinical relapses and delay the progression of disability. Its mechanism involves suppressing the immune system to prevent the immune cells from attacking the nervous system. The drug is administered orally or intravenously, depending on the condition being treated. Due to its potent effects, careful monitoring of patients is essential to manage potential side effects and ensure optimal therapeutic outcomes.