Yongbo Hu

Identification of pyrazolo[1,5-a]pyrimidine-3-carboxylates as B-Raf kinase inhibitors.

B-Raf kinase plays a critical role in the Raf-MEK-ERK signaling pathway and inhibitors of B-Raf could be used in the treatment of melanomas, colorectal cancer, and other Ras related human cancers. We have identified novel small molecule pyrazolo[1,5-a]pyrimidine derivatives as B-Raf kinase inhibitors. Structure-activity relationship was generated for various regions of the scaffold to improve the biochemical profile.

Small molecule inhibitors of HIV RT Ribonuclease H.

Two classes of compounds, thiocarbamates 1 and triazoles 2, have been identified as HIV RT RNase H inhibitors using a novel FRET-based HTS assay. The potent analogs in each series exhibited selectivity and were active in cell-based assays. In addition, saturable, 1:1 stoichiometric binding to target was established and time of addition studies were consistent with inhibition of RT-mediated HIV replication.

Benzo[c][2,7]naphthyridines as inhibitors of PDK-1.

A series of substituted benzo[c][2,7]-naphthyridines were prepared and showed good potency in inhibiting PDK-1. The synthesis and SAR of this series of compounds are presented as well as the X-ray crystal structure of one of these analogs in a complex with PDK-1.

Non-hinge-binding pyrazolo[1,5-a]pyrimidines as potent B-Raf kinase inhibitors.

As part of our research effort to discover B-Raf kinase inhibitors, we prepared a series of C-3 substituted N-(3-(pyrazolo[1,5-a]pyrimidin-7-yl)phenyl)-3-(trifluoromethyl)benzamides. X-ray crystallography studies revealed that one of the more potent inhibitors (10n) bound to B-Raf kinase without forming a hinge-binding hydrogen bond. With basic amine residues appended to C-3 aryl residues, cellular activity and solubility were enhanced over previously described compounds of this class.

Discovery of highly potent and selective type I B-Raf kinase inhibitors

A series of pyrazolo[1,5-alpha]pyrimidine analogs has been prepared and found to be potent and selective B-Raf inhibitors. Molecular modeling suggests they bind to the active conformation of the enzyme.

Novel pyrazolopyrimidines as highly potent B-Raf inhibitors.

A novel series of pyrazolo[1,5-a]pyrimidines bearing a 3-hydroxyphenyl group at C(3) and substituted tropanes at C(7) have been identified as potent B-Raf inhibitors. Exploration of alternative functional groups as a replacement for the C(3) phenol demonstrated indazole to be an effective isostere. Several compounds possessing substituted indazole residues, such as 4e, 4p, and 4r, potently inhibited cell proliferation at submicromolar concentrations in the A375 and WM266 cell lines, and the latter two compounds also exhibited good therapeutic indices in cells.

Design and SAR of macrocyclic Hsp90 inhibitors with increased metabolic stability and potent cell-proliferation activity.

A novel series of macrocyclic ortho-aminobenzamide Hsp90 inhibitors is reported. A basic nitrogen within the tether linking the aniline nitrogen atom to a tetrahydroindolone moiety allowed access to compounds with good physical properties. Important structure-activity relationship information was obtained from this series which led to the discovery of a soluble and stable compound which is potent in an Hsp90 binding and cell-proliferation assay.

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.