6-Ethynylthieno[3,2-d]- and 6-ethynylthieno[2,3-d]pyrimidin-4-anilines as tunable covalent modifiers of ErbB kinases.

Analysis of the x-ray crystal structure of mono-substituted acetylenic thienopyrimidine 6 complexed with the ErbB family enzyme ErbB-4 revealed a covalent bond between the terminal carbon of the acetylene moiety and the sulfhydryl group of Cys-803 at the solvent interface. The identification of this covalent adduct suggested that acetylenic thienopyrimidine 6 and related analogs might also be capable of forming an analogous covalent adduct with EGFR, which has a conserved cysteine (797) near the ATP binding pocket. To test this hypothesis, we treated a truncated, catalytically competent form of EGFR (678-1020) with a structurally related propargylic amine (8). An investigation of the resulting complex by mass spectrometry revealed the formation of a covalent complex of thienopyrimidine 8 with Cys-797 of EGFR. This finding enabled us to readily assess the irreversibility of various inhibitors and also facilitated a structure-activity relationship understanding of the covalent modifying potential and biological activity of a series of acetylenic thienopyrimidine compounds with potent antitumor activity. Several ErbB family enzyme and cell potent 6-ethynyl thienopyrimidine kinase inhibitors were found to form covalent adducts with EGFR.

Synthesis and stereochemical effects of pyrrolidinyl-acetylenic thieno[3,2-d]pyrimidines as EGFR and ErbB-2 inhibitors.

A novel class of pyrrolidinyl-acetyleneic thieno[3,2-d]pyrimidines has been identified which potently inhibit the EGFR and ErbB-2 receptor tyrosine kinases. Synthetic modifications of the pyrrolidine carbamate moiety result in a range of effects on enzyme and cellular potency. In addition, the impact of the absolute stereochemical configuration on cellular potency and oral mouse pharmacokinetics is described.

Dual EGFR/ErbB-2 inhibitors from novel pyrrolidinyl-acetylenic thieno[3,2-d]pyrimidines.

A novel class of substituted pyrrolidinyl-acetylenic thieno[3,2-d]pyrimidines has been identified that are potent and selective inhibitors of both EGFR/ErbB-2 receptor tyrosine kinases. The inhibitors are found to display a range of enzyme and cellular potency and also to display a varying level of covalent modification of the kinase targets. Selected molecules, including compound 15h, were found to be potent in enzymatic and cellular assays while also demonstrating exposure in the mouse from an oral dose.

Synthesis and evaluation of pyrazolo[1,5-b]pyridazines as selective cyclin dependent kinase inhibitors.

A novel series of pyrazolo[1,5-b]pyridazines have been synthesized and identified as cyclin dependant kinase inhibitors potentially useful for the treatment of solid tumors. Modification of the hinge-binding amine or the C(2)- and C(6)-substitutions on the pyrazolopyridazine core provided potent inhibitors of CDK4 and demonstrated enzyme selectivity against VEGFR-2 and GSK3beta.

Kinase-targeted library design through the application of the PharmPrint methodology.

The PharmPrint methodology, as modified and implemented by Deanda and Stewart, was prospectively evaluated for use as a virtual high-throughput screening tool by applying it to the design of target-focused arrays. To this end, PharmPrint quantitative structure-activity relationship (QSAR) models for the prediction of AKT1, Aurora-A, and ROCK1 inhibition were constructed and used to virtually screen two large combinatorial libraries. Based on predicted activities, an Aurora-A targeted array and a ROCK1 targeted array were designed and synthesized. One control group per designed array was also synthesized to assess the enrichment levels achieved by the QSAR models. For the Aurora-A targeted array, the hit rate, against the intended target, was 42.9%, whereas that of the control group was 0%. Thus, the enrichment level achieved by the Aurora-A QSAR model was incalculable. For the ROCK1 targeted array, the hit rate against the intended target was 30.6%, whereas that of the control group was 5.10%, making the enrichment level achieved by the ROCK1 QSAR model 6-fold above control. Clearly, these results support the use of the PharmPrint methodology as a virtual screening tool for the design of kinase-targeted arrays.

Alkynyl pyrimidines as dual EGFR/ErbB2 kinase inhibitors.

Anilinoalkynylpyrimidines were prepared and evaluated as dual EGFR/ErbB2 kinase inhibitors. A preference was found for substituted phenyl and heteroaromatic rings attached to the alkyne. In addition, the presence of a potential hydrogen bond donor appended to this ring was favored. Selected molecules in the series demonstrated some activity against human tumor cell lines.