Structural Superimposition

Abstact

Bruton's Tyrosine Kinase (BTK) is a validated target for hematological malignancies, with numerous FDA-approved inhibitors on the market. Current therapies target the highly conserved ATP binding site and hence limit the therapeutic index given the site's highly conserved nature across the kinome. We explore a novel approach for BTK inhibition by targeting the PH domain-mediated membrane recruitment and activation of BTK. We have identified a fragment which covalently modifies a lysine in the inositol phosphate (PIP3) binding site and inhibits the binding of a soluble PIP3 headgroup analog to the PH domain. Fragment growth and an extensive structure-binding relationship study uncovered 27 crystal structures and a best-in-class analog, 24. Evaluation of pK(a) values of the targeted lysine in BTK and other PH domains suggests this as a more general approach to PH domain inhibition.