Discovery of GSK251: A Highly Potent, Highly Selective, Orally Bioavailable Inhibitor of PI3Kδ with a Novel Binding Mode.

Optimization of a previously reported lead series of PI3Kδ inhibitors with a novel binding mode led to the identification of a clinical candidate compound 31 (GSK251). Removal of an embedded Ames-positive heteroaromatic amine by reversing a sulfonamide followed by locating an interaction with Trp760 led to a highly selective compound 9. Further optimization to avoid glutathione trapping, to enhance potency and selectivity, and to optimize an oral pharmacokinetic profile led to the discovery of compound 31 (GSK215) that had a low predicted daily dose (45 mg, b.i.d) and a rat toxicity profile suitable for further development.

Design and Development of a Macrocyclic Series Targeting Phosphoinositide 3-Kinase δ.

A macrocyclization approach has been explored on a series of benzoxazine phosphoinositide 3-kinase δ inhibitors, resulting in compounds with improved potency, permeability, and in vivo clearance while maintaining good solubility. The thermodynamics of binding was explored via surface plasmon resonance, and the binding of lead macrocycle 19 was found to be almost exclusively entropically driven compared with progenitor 18, which demonstrated both enthalpic and entropic contributions. The pharmacokinetics of macrocycle 19 was also explored in vivo, where it showed reduced clearance when compared with the progenitor 18. This work adds to the growing body of evidence that macrocyclization could provide an alternative and complementary approach to the design of small-molecule inhibitors, with the potential to deliver differentiated properties.

p38alpha mitogen-activated protein kinase inhibitors: optimization of a series of biphenylamides to give a molecule suitable for clinical progression.

p38alpha MAP kinase is a key anti-inflammatory target for rheumatoid arthritis, influencing biosynthesis of pro-inflammatory cytokines TNFalpha and IL-1beta at a translational and transcriptional level. In this paper, we describe how we have optimized a series of novel p38alpha/beta inhibitors using crystal structures of our inhibitors bound to p38alpha, classical medicinal chemistry, and modeling of virtual libraries to derive a molecule suitable for progression into clinical development.