Pentostatin (2prime prime or minute-Deoxycoformycin): Clinical Pharmacology, Role In Cancer Chemotherapy, and Future Prospects.

Pentostatin (2prime prime or minute-deoxycoformycin, dCF) is a product of the fermentation of Streptomyces antibioticus. It is a tight-binding inhibitor of adenosine deaminase (ADA), an enzyme essential in cellular metabolism of purines. Children with congenital absence of ADA suffer from atrophy of lymphoid tissues and severe combined immune deficiency (SCID) syndrome. It was speculated that pentostatin would be lymphocytotoxic, and this proved to be the case, promoting its investigation in lymphoid neoplasms. It was anticipated that pentostatin would be most active in neoplasms with high intracellular concentrations of ADA---e.g., acute lymphocytic leukemia (ALL), particularly its T cell variety. Although pentostatin proved to be active in ALL, large doses were required and toxic effects outweighted therapeutic benefits. By contrast, pentostatin proved to be exceptionally active in hairy cell leukemia (HCL), a B cell neoplasm with low intracellular concentrations of ADA. Pentostatin has since been shown to possess activity in chronic lymphocytic leukemia, prolymphocytic leukemia, cutaneous T cell lymphomas, adult T cell lymphoma-leukemia, and low-grade non-Hodgkin's lymphomas. It potentiates the activity of vidarabine against viruses and against the cells of acute myeloid leukemia. Pentostatin is inactive in melanoma and renal carcinoma, but has not been adequately evaluated in other solid tumors. The toxic effects of pentostatin include renal failure, central nervous system (CNS) depression, immunosuppression, keratoconjunctivitis, and opportunistic infections. In the absence of pre-existing bone marrow compromise, pentostatin produces only mild myelosuppression. Aside from its use as an antineoplastic agent, pentostatin has potential applications as an immunosuppresive drug, as an antiviral agent, as an antimalarial compound, and in the protection of cells of the CNS from damage induced by ischemia and anoxia.