Discovery, Optimization,
and in Vivo Evaluation of
Benzimidazole Derivatives AM-8508 and AM-9635 as Potent and Selective
PI3Kδ Inhibitors
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Abstract
Lead
optimization efforts resulted in the discovery of two potent,
selective, and orally bioavailable PI3Kδ inhibitors, <b>1</b> (AM-8508) and <b>2</b> (AM-9635), with good pharmacokinetic
properties. The compounds inhibit B cell receptor (BCR)-mediated AKT
phosphorylation (pAKT) in PI3Kδ-dependent in vitro cell based
assays. These compounds which share a benzimidazole bicycle are effective
when administered in vivo at unbound concentrations consistent with
their in vitro cell potency as a consequence of improved unbound drug
concentration with lower unbound clearance. Furthermore, the compounds
demonstrated efficacy in a Keyhole Limpet Hemocyanin (KLH) study in
rats, where the blockade of PI3Kδ activity by inbibitors <b>1</b> and <b>2</b> led to effective inhibition of antigen-specific
IgG and IgM formation after immunization with KLH