Discovery of (S)-2-(1-(4-Amino-3-(3-fluoro-4-methoxyphenyl)-1H-pyrazolo[3,4-d]pyrimidin-1-yl)propyl)-3-cyclopropyl-5-fluoroquinazolin-4(3H)-one (IHMT-PI3Kδ-372) as a Potent and Selective PI3Kδ Inhibitor for the Treatment of Chronic Obstructive Pulmonary Disease.

Accumulated pieces of evidence have shown that PI3Kδ plays a critical role in chronic obstructive pulmonary disease (COPD). Using a fragment-hybrid approach, we discovered a potent and selective PI3Kδ inhibitor (S)-18. In the biochemical assay, (S)-18 inhibits PI3Kδ (IC50 = 14 nM) with high selectivity over other class I PI3Ks (56∼83 fold). (S)-18 also achieves good selectivity over other protein kinases in the kinome (S-score (35) = 0.015). In the cell, (S)-18 selectively and potently inhibits the PI3Kδ-mediated phosphorylation of AKT T308 but not other class I PI3K-mediated signaling. Additionally, (S)-18 exhibits no apparent inhibitory effect on CYP isoforms except for a moderate effect on CYP2C9. Furthermore, it shows no apparent inhibitory activity against hERG (IC50 > 10 μM). In vivo, (S)-18 displays favorable PK properties for inhaled delivery and improves lung function in a rodent model of pulmonary inflammation. These results suggest that (S)-18 might be a new potential therapeutic candidate for COPD.