Cladribine (Leustatin)'s a drug used to treat hairy cell leukemia (leukemic reticuloendotheliosis) and multiple sclerosis. Its chemical name's 2-chlorodeoxyadenosine (2CDA). As a purine analog, it's a synthetic anti-cancer agent that also suppresses the immune system. Chemically, it mimics the nucleoside adenosine and thus inhibits the enzyme adenosine deaminase, which interferes with the cell's ability to process DNA. It's easily destroyed by normal cells except for blood cells, with the resu… (More on Cladribine)