Penicillamine is a beta dimethyl analog of the amino acid cysteine. As a degradation product of penicillin antibiotics, penicillamine chelates with heavy metals and increases their urinary excretion. Possessing antineoplastic properties, penicillamine induces apoptosis by a p53-mediated mechanism and inhibits angiogenesis by chelating with copper, a cofactor for angiogenesis.