Purine Nucleoside Phosphorylase Inhibition as a Novel Therapeutic Approach for B-Cell Lymphoid Malignancies

Purine nucleoside phosphorylase (PNP) catalyzes the reversible phosphorolysis of ribonucleosides and 2′-deoxyribonucleosides to their respective bases. Endogenous PNP deficiency leads to specific T-cell immunodeficiency, a genetic disease that has prompted the development of PNP inhibitors as potential therapies for T-cell–mediated diseases. PNP inhibition leads to the elevation of 2′-deoxyguanosine levels and accumulation of intracellular deoxyguanosine 5′-triphosphate, inducing cellular apoptosis. Forodesine is a highly potent, orally active, rationally designed PNP inhibitor that has shown activity in preclinical studies with malignant cells and clinical utility against T-cell acute lymphoblastic leukemia and cutaneous T-cell lymphoma. Additional preliminary findings support its use for the management of some B-cell malignancies.