Epithelial tissue hyperplasia induced by the RAF inhibitor PF-04880594 is attenuated by a clinically well-tolerated dose of the MEK inhibitor PD-0325901.

Clinical trials of selective RAF inhibitors in patients with melanoma tumors harboring activated BRAFV600E have produced very promising results, and a RAF inhibitor has been approved for treatment of advanced melanoma. However, about a third of patients developed resectable skin tumors during the course of trials. This is likely related to observations that RAF inhibitors activate extracellular signal-regulated kinase (ERK) signaling, stimulate proliferation, and induce epithelial hyperplasia in preclinical models.

Structure-based design of isoindoline-1,3-diones and 2,3-dihydrophthalazine-1,4-diones as novel B-Raf inhibitors.

Structure-guided design led to the discovery of novel chemical scaffolds for B-Raf inhibitors. Both type I and type II kinase inhibitors have been explored and lead compounds with good potency and excellent selectivity have been identified.

Indazolylpyrazolopyrimidine as highly potent B-Raf inhibitors with in vivo activity.

Novel indazolylpyrazolo[1,5-a]pyrimidine analogues have been prepared and found to be extremely potent type I B-Raf inhibitors. The lead compound shows good selectivity against a panel of 60 kinases, possesses a desirable pharmacokinetic profile, and demonstrates excellent in vivo antitumor efficacy in B-Raf mutant xenograft models.

B-Raf kinase inhibitors: hit enrichment through scaffold hopping.

In continuation of our efforts toward hit identification and optimization for a B-Raf kinase project, we have employed a scaffold hopping strategy. The original HTS hit scaffold pyrazolo[1,5-a]pyrimidine was replaced with different thienopyrimidine and thienopyridine scaffolds to append the optimal pharmacophore moieties in order to generate novel B-raf kinase inhibitors with desirable potency and properties. This strategy led to the identification of additional lead compound 11b which had good enzyme and cell potency, while maintaining selectivity over a number of kinases.

Hit to lead optimization of pyrazolo[1,5-a]pyrimidines as B-Raf kinase inhibitors.

Our continued effort towards optimization of the pyrazolo[1,5-a]pyrimidine scaffold as B-Raf kinase inhibitors is described. Structure guided design was utilized to introduce kinase hinge region interacting groups in the 2-position of the scaffold. This strategy led to the identification of lead compound 9 with enhanced enzyme and cellular potency, while maintaining good selectivity over a number of kinases.