TrkA kinase inhibitors from a library of modified and isosteric Staurosporine aglycone.

An immobilized Staurosporine aglycone isostere where one of the indole nitrogen atoms was replaced by carbon has been sequentially functionalized to generate compounds inhibiting TrkA kinase. In the first phase, initial screening of a library of C13-hydroxymethyl-7-oxo-indenopyrrolocarbazoles resulted in several potent compounds, one of which was further optimized to generate the corresponding carbamates on solid phase. Some of the major carbamate diastereomers were found to be several-fold more potent than their alcohol parents. Synthesis, SAR analysis, kinase selectivity, and anti-tumor properties of a TrkA inhibitor (12a) are discussed.

1,2,3-Thiadiazole substituted pyrazolones as potent KDR/VEGFR-2 kinase inhibitors.

KDR kinase inhibition is considered to play an important role in regulating angiogenesis, which is vital for the survival and proliferation of tumor cells. Recently we disclosed a structure-based kinase inhibitor design strategy which led to the identification of a new class of VEGFR-2/KDR kinase inhibitors bearing heterocyclic substituted pyrazolones as the core template. Instability in a rat S9 preparation and poor iv PK profiles for most of these inhibitors necessitated exploration of new pyrazolones to identify new analogs with improved metabolic stability. Optimization of the heterocyclic moiety led to the identification of the thiadiazole series of pyrazolones (D) as potent VEGFR-2/KDR kinase inhibitors. SAR modifications, kinase selectivity profiling, and structural elements for improved PK properties were explored. Oral bioavailability up to 29% was achieved in the rat. Modeling results based on the Glide XP docking approach supported our postulation regarding the interaction of the lactam segment of the pyrazolones with the hinge region of the KDR kinase.

Structure-guided identification of novel VEGFR-2 kinase inhibitors via solution phase parallel synthesis.

Structural analysis of the essential binding elements of the oxindole-based kinase inhibitor (1) led to the identification of a novel class of heterocyclic-substituted pyrazolones. Knoevenagel condensation of a variety of activated methylene nucleophiles with indole or pyrrole carboxaldehydes provided a focused library of molecules, each containing elements of kinase pharmacophore probe. Initial screening for VEGFR-2 kinase inhibition eliminated several of the probes. Identification of an active pyrazolone motif and further optimization resulted in several highly potent VEGFR-2 inhibitors with cellular efficacy, anti-angiogenic activity ex vivo in rat aortic ring explant cultures, and oral anti-tumor efficacy in nude mice.

Synthesis, modeling, and in vitro activity of (3'S)-epi-K-252a analogues. Elucidating the stereochemical requirements of the 3'-sugar alcohol on trkA tyrosine kinase activity.

Utilizing our recently published semisynthetic approach to the (3'S)-K-252a diastereomer, we report the first synthesis of the (3'R)-10 diastereomer and a set of related epimers, with the goal of defining the stereochemical role of the 3'-sugar hydroxyl group on trkA tyrosine kinase activity and selectivity. (3'R)-10 displayed potent trkA inhibitory activity with an IC50 value of 4 nM. The corresponding deshydroxy epimer (3'S)-14 was 7-fold more potent than its 3'R counterpart (natural stereochemistry) with a trkA IC50 value of 3 nM and demonstrated >280-fold selectivity over PKC (IC50 = 850 nM). In cells, (3'S)-14 displayed potent inhibition of trkA autophosphorylation with an IC50 < 10 nM. Molecular modeling studies revealed that the 3'-OH, due to the inverted geometry, forms significant H-bonding interactions with Glu27 and Arg195, an interaction that is not attainable with the natural isomers.