Originally developed for psoriasis and gout but later discontinued, the purine nucleoside phosphorylase (PNP) inhibitor Ulodesine now shows promise as an immune checkpoint inhibitor to treat leukemia.

Structural formula of inosine. Inosine is a nucleoside containing hypoxanthine and ribose. It differs from adenosine by the absence of an amino group at the 6 position of the purine ring. (Image: ...