Peldesine (BCX 34) is an effective, competitive, reversible, and orally active inhibitor of purine nucleoside phosphorylase. Peldesine inhibits T-cell proliferation with an IC50 of 800 nM. Peldesine can be used in research on cutaneous T-cell lymphoma, psoriasis and HIV infection.

RBC PNP (mouse):32 nM , RBC PNP (human):36 nM , Proliferation (human T cells):800 nM , PNP (rat red blood cells):5 nM

The IC50s are 36 nM, 5 nM, and 32 nM for human, rat, and mouse red blood cell purine nucleoside phosphorylase, respectively. In Jurkat cells, Peldesine (BCX 34; 0-50 µM; 72 hours) inhibits the T-cell proliferation completely at a concentration of less than 10 μM, in the presence of dGuo (10 μM). In contrast, the B-cell proliferation is not affected by Peldesine[1].

Peldesine demonstrates oral efficacy by elevating plasma inosine levels in rats (2-fold at 30 mg/kg), significantly reducing ex vivo red blood cell (RBC) purine nucleoside phosphorylase (PNP) activity in rats (98% at 3 hours, 100 mg/kg), and moderately suppressing ex vivo skin PNP activity in mice (39% at 3 hours, 100 mg/kg). Additionally, Peldesine exhibits an oral bioavailability of 76% in rats[2].