Cladribine anti-cancer drug molecule. Tubular model of a molecule of the anti-cancer drug cladribine, also known as leustatin. It is mainly used to treat hairy cell leukaemia, but is also used in patients with multiple sclerosis. The chemical formula is C10.H12.Cl.N5.O3. The atoms are represented here as colour-coded rods: carbon (grey), hydrogen (white), chlorine (green), nitrogen (blue) and oxygen (red).