Discovery of a series of 8-(1-phenylpyrrolidin-2-yl)-6-carboxamide-2-morpholino-4H-chromen-4-one as PI3Kβ/δ inhibitors for the treatment of PTEN-deficient tumours

Attempts to lock the active conformation of compound 4, a PI3Kβ/δ inhibitor (PI3Kβ cell IC₅₀ 0.015μM), led to the discovery of a series of 8-(1-phenylpyrrolidin-2-yl)-6-carboxamide-2-morpholino-4H-chromen-4-ones, which showed high levels of potency and selectivity as PI3Kβ/δ inhibitors. Compound 10 proved exquisitely potent and selective: PI3Kβ cell IC₅₀ 0.0011μM in PTEN null MDA-MB-468 cell and PI3Kδ cell IC₅₀ 0.014μM in Jeko-1 B-cell, and exhibited suitable physical properties for oral administration. In vivo, compound 10 showed profound pharmacodynamic modulation of Akt phosphorylation in a mouse PTEN-null PC3 prostate tumour xenograft after a single oral dose and gave excellent tumour growth inhibition in the same model after chronic oral dosing. Based on these results, compound 10 was selected as one of our PI3Kβ/δ preclinical candidates.