Discovery of 3,5-disubstituted-1H-pyrrolo[2,3-b]pyridines as potent inhibitors of the insulin-like growth factor-1 receptor (IGF-1R) tyrosine kinase.

Exploration of the SAR around a series of 3,5-disubstituted-1H-pyrrolo[2,3-b]pyridines led to the discovery of novel pyrrolopyridine inhibitors of the IGF-1R tyrosine kinase. Several compounds demonstrated nanomolar potency in enzyme and cellular mechanistic assays.

Discovery and optimization of imidazo[1,2-a]pyridine inhibitors of insulin-like growth factor-1 receptor (IGF-1R).

The optimization of imidazo[1,2-a]pyridine inhibitors as potent and selective inhibitors of IGF-1R is presented. Further optimization of oral exposure in mice is also discussed. Detailed selectivity, in vitro activity, and in vivo PK profiles of an optimized compound is also highlighted.

Discovery of 4,6-bis-anilino-1H-pyrrolo[2,3-d]pyrimidines: potent inhibitors of the IGF-1R receptor tyrosine kinase.

The evaluation of a series of 4,6-bis-anilino-1H-pyrrolo[2,3-d]pyrimidines as inhibitors of the IGF-1R (IGF-IR) receptor tyrosine kinase is reported. Examples demonstrate nanomolar potencies in in vitro enzyme and mechanistic cellular assays as well as promising in vivo pharmacokinetics in rat.

Optimization of 4,6-bis-anilino-1H-pyrrolo[2,3-d]pyrimidine IGF-1R tyrosine kinase inhibitors towards JNK selectivity.

The SAR of C5' functional groups with terminal basic amines at the C6 aniline of 4,6-bis-anilino-1H-pyrrolo[2,3-d]pyrimidines is reported. Examples demonstrate potent inhibition of IGF-1R with 1000-fold selectivity over JNK1 and 3 in enzymatic assays.

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.

X-ray crystal structure of the novel enhanced-affinity glucocorticoid agonist fluticasone furoate in the glucocorticoid receptor-ligand binding domain.

An X-ray crystal structure is reported for the novel enhanced-affinity glucocorticoid agonist fluticasone furoate (FF) in the ligand binding domain of the glucocorticoid receptor. Comparison of this structure with those of dexamethasone and fluticasone propionate shows the 17 alpha furoate ester to occupy more fully the lipophilic 17 alpha pocket on the receptor, which may account for the enhanced glucocorticoid receptor binding of FF.

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.

Crystallization of protein-ligand complexes.

Obtaining diffraction-quality crystals has long been a bottleneck in solving the three-dimensional structures of proteins. Often proteins may be stabilized when they are complexed with a substrate, nucleic acid, cofactor or small molecule. These ligands, on the other hand, have the potential to induce significant conformational changes to the protein and ab initio screening may be required to find a new crystal form. This paper presents an overview of strategies in the following areas for obtaining crystals of protein-ligand complexes: (i) co-expression of the protein with the ligands of interest, (ii) use of the ligands during protein purification, (iii) cocrystallization and (iv) soaks.

Novel, potent P2-P3 pyrrolidine derivatives of ketoamide-based cathepsin K inhibitors.

Starting from a potent pantolactone ketoamide cathepsin K inhibitor discovered from structural screening, conversion of the lactone scaffold to a pyrrolidine scaffold allowed exploration of the S(3) subsite of cathepsin K. Manipulation of P3 and P1' groups afforded potent inhibitors with drug-like properties.

Semicarbazone-based inhibitors of cathepsin K, are they prodrugs for aldehyde inhibitors?

Starting from potent aldehyde inhibitors with poor drug properties, derivatization to semicarbazones led to the identification of a series of semicarbazone-based cathepsin K inhibitors with greater solubility and better pharmacokinetic profiles than their parent aldehydes. Furthermore, a representative semicarbazone inhibitor attenuated bone resorption in an ex vivo rat calvarial bone resorption model. However, based on enzyme inhibition comparisons at neutral pH, semicarbazone hydrolysis rates, and 13C NMR experiments, these semicarbazones probably function as prodrugs of aldehydes.

P2-P3 conformationally constrained ketoamide-based inhibitors of cathepsin K.

An orally bioavailable series of ketoamide-based cathepsin K inhibitors with good pharmacokinetic properties has been identified. Starting from a potent inhibitor endowed with poor drug properties, conformational constraint of the P(2)-P(3) linker and modifications to P(1') elements led to an enhancement in potency, solubility, clearance, and bioavailability. These optimized inhibitors attenuated bone resorption in a rat TPTX hypocalcemic bone resorption model.

Acyclic cyanamide-based inhibitors of cathepsin K.

Conversion of the proline-derived cyanamide lead to an acyclic cyanamide capable of forming an additional hydrogen bond with cathepsin K resulted in a large increase in inhibitory activity. An X-ray structure of a co-crystal of a cyanamide with cathepsin K confirmed the enzyme interaction. Furthermore, a representative acyclic cyanamide inhibitor 6r was able to attenuate bone resorption in the rat calvarial model.

Novel and potent cyclic cyanamide-based cathepsin K inhibitors.

Starting from a PDE IV inhibitor hit derived from high throughput screening of the compound collection, a key pyrrolidine cyanamide pharmacophore was identified. Modifications of the pyrrolidine ring produced enhancements in cathepsin K inhibition. An X-ray co-crystal structure of a cyanamide with cathepsin K confirmed the mode of inhibition.

Potent and selective P2-P3 ketoamide inhibitors of cathepsin K with good pharmacokinetic properties via favorable P1', P1, and/or P3 substitutions.

A series of ketoamides were synthesized and evaluated for inhibitory activity against cathepsin K. Exploration of the interactions between achiral P(2) substituents and the cysteine protease based on molecular modelling suggestions resulted in potent cathepsin K inhibitors that demonstrated high selectivity versus cathepsins B, H, and L. Subsequent modifications of the P(3), P(1), and P(1') moieties afforded orally bioavailable inhibitors.

Exploration of the P2-P3 SAR of aldehyde cathepsin K inhibitors.

The synthesis and biological activity of a series of aldehyde inhibitors of cathepsin K are reported. Exploration of the properties of the S2 and S3 subsites with a series of carbamate derivatized norleucine aldehydes substituted at the P2 and P3 positions afforded analogs with cathepsin K IC50s between 600 nM and 130 pM.

Design of potent, selective, and orally bioavailable inhibitors of cysteine protease cathepsin k.

Osteoclast-mediated bone matrix resorption has been attributed to cathepsin K, a cysteine protease of the papain family that is abundantly and selectively expressed in osteoclast. Inhibition of cathepsin K could potentially be an effective method to prevent osteoporosis. Structure-activity studies on a series of reversible ketoamides based inhibitors of cathepsin K have led to identification of potent and selective compounds. Crystallographic studies have given insights into the mode of binding of these inhibitors. A series of ketoamides with varying P1 moieties were first synthesized to find an optimum group that would fit into the S1 subsite of the cysteine protease, cathepsin K. With a desired P1 group in place a variety of heterocyclic analogues in the P' region were synthesized to study their steric and electronic effects. In the process of exploring these P' heterocyclic variations, excellent selectivity was gained over other highly homologous cysteine proteases, including cathepsins L, S, and V. The favorable pharmacokinetic properties of some of these cathepsin K inhibitors in rats make them suitable for evaluation in rodent osteoporosis models. A representative cathepsin K inhibitor was shown to attenuate PTH-stimulated hypercalcemia in the TPTX rat model. These inhibitors provide a viable lead series in the discovery of new therapies for the prevention and treatment of osteoporosis