Discovery of a Potent, Selective, and Orally Available PI3Kδ Inhibitor for the Treatment of Inflammatory Diseases

The delta isoform of the phosphatidylinositol 3-kinase (PI3K delta) has been shown to have an essential role in specific immune cell functions and thus represents a potential therapeutic target for autoimmune and inflammatory diseases. Herein, the optimization of a series of pyrrolotriazinones as potent and selective PI3K delta inhibitors is described. The main challenge of the optimization process was to identify an orally available compound with a good pharmacokinetic profile in preclinical species that predicted a suitable dosing regimen in humans. Structure activity relationships and structure property relationships are discussed. This medicinal chemistry exercise led to the identification of LAS191954 as a candidate for clinical development.