The Discovery of BMS-737 as a Potent, CYP17 Lyase-Selective Inhibitor for the Treatment of Castration-Resistant Prostate Cancer

We report herein, the discovery of BMS-737 (compound 33) as a potent, non-steroidal, reversible small molecule inhibitor demonstrating 11-fold selectivity for CYP17 lyase over CYP17 hydroxylase, as well as a clean xenobiotic CYP profile for the treatment of castration-resistant prostate cancer (CRPC). Extensive SAR studies on the initial lead 1 at three different regions of the molecule resulted in the identification of BMS-737, which demonstrated a robust 83% lowering of testosterone without any significant perturbation of the mineralocorticoid and glucocorticoid levels in cynomologous monkeys in a 1-day PK/PD study.

Discovery of BMS-986202: A Clinical Tyk2 Inhibitor that Binds to Tyk2 JH2

A search for structurally diversified Tyk2 JH2 ligands from 6 (BMS-986165), a pyridazine carboxamide-derived Tyk2 JH2 ligand as a clinical Tyk2 inhibitor currently in late development for the treatment of psoriasis, began with a survey of six-membered heteroaryl groups in place of the N-methyl triazolyl moiety in 6. The X-ray co-crystal structure of an early lead (12) revealed a potential new binding pocket. Exploration of the new pocket resulted in two frontrunners for a clinical candidate. The potential hydrogen bonding interaction with Thr599 in the pocket was achieved with a tertiary amide moiety, confirmed by the X-ray co-crystal structure of 29. When the diversity search was extended to nicotinamides, a single fluorine atom addition was found to significantly enhance the permeability, which directly led to the discovery of 7 (BMS-986202) as a clinical Tyk2 inhibitor that binds to Tyk2 JH2. The preclinical studies of 7, including efficacy studies in mouse models of IL-23-driven acanthosis, anti-CD40-induced colitis, and spontaneous lupus, will also be presented.

Discovery of the Selective CYP17A1 Lyase Inhibitor BMS-351 for the Treatment of Prostate Cancer

Efforts to identify a potent, reversible, nonsteroidal CYP17A1 lyase inhibitor with good selectivity over CYP17A1 hydroxylase and CYPs 11B1 and 21A2 for the treatment of castration-resistant prostate cancer (CRPC) culminated in the discovery of BMS-351 (compound 18), a pyridyl biaryl benzimidazole with an excellent in vivo profile. Biological evaluation of BMS-351 at a dose of 1.5 mg in castrated cynomolgus monkeys revealed a remarkable reduction in testosterone levels with minimal glucocorticoid and mineralcorticoid perturbation. Based on a favorable profile, BMS-351 was selected as a candidate for further preclinical evaluation.

Abstract 5395: Anti-tumor activity of BMS-595, a novel CK2 kinase inhibitor

The CK2 protein kinases are a small family of two highly related serine/threonine kinases composed of two catalytic subunits, α and α’, and a single β subunit. Numerous substrates have been reported for CK2 and these proteins are known to participate in diverse cellular processes, including cell signaling, transcription, DNA repair, apoptosis regulation and tumor suppression. Elevated CK2 expression and kinase activity has been observed in many cancer types. Further, mRNA knockdown and enzyme inhibition studies have demonstrated that many cancer cell lines are dependent on CK2 for growth and survival. To further evaluate CK2 kinases as targets for therapeutic intervention in cancer, we identified BMS-595, a potent and selective, ATP-competitive CK2 inhibitor. BMS-595 inhibits the in vitro proliferation of human colorectal and lung cancer cell lines with IC50s ranging from less than 10 nM to greater than 1 μM. In sensitive cell lines, anti-proliferative effects of BMS-595 and structurally related analogs strongly correlated with cellular CK2 kinase inhibition. Oral administration of BMS-595 to mice bearing colorectal cancer and lung cancer xenografts demonstrated pharmacodynamic effects and robust efficacy at tolerated doses. These studies confirm the dependence of a subset of human colon and lung cancer cell lines on CK2 activity for growth and demonstrate that pharmacologic inhibition of CK2 can produce anti-tumor efficacy at tolerated doses.

Citation Format: Brent A. Rupnow, Chiang Yu, Jonathan G. Pabalan, Urvashi V. Roongta, Jonathan S. Lippy, Ashok R. Dongre, Mary T. Obermeier, Aberra Fura, Paul A. Elzinga, Benjamin J. Henley, Joseph Fargnoli, Francis Y. Lee, William R. Foster, Christine M. Tarby, Brian E. Fink, John S. Tokarski, Ashvinikumar V. Gavai, Tai W. Wong, John T. Hunt, Gregory D. Vite, Ashok V. Purandare. Anti-tumor activity of BMS-595, a novel CK2 kinase inhibitor. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5395. doi:10.1158/1538-7445.AM2015-5395

Rapid throughput screening of apparent KSP values for weakly basic drugs using 96-well format

A rapid-throughput screening assay was developed to estimate the salt solubility parameter, K(SP), with a minimal quantity of drug. This assay allows for early evaluation of salt limited solubility with a large number of counter-ions and biologically promising drug leads. Drugs dissolved (typically 10 mM) in DMSO are robotically distributed to a 96-well plate. DMSO is evaporated, and drugs are equilibrated with various acids at different concentrations (typically <1 M) to yield final total drug concentrations around 2.5 mM. The plate is checked for precipitation. Filtrates from only those precipitated wells were subjected to rapid gradient HPLC analysis. An iterative procedure is employed to calculate all species concentrations based on mass and charge balance equations. The apparent K(SP) values assuming 1:1 stoichiometry are determined from counter-ion and ionized drug activities. A correlation coefficient >0.975 for eight drugs totaling 16 salts is reported. Intra-day and inter-day reproducibility was <10%. Conventional apparent K(SP) measurements were translated to 96-well format for increased throughput and minimal drug consumption (typically 10 mg) to evaluate at least eight different counter-ions. Although the current protocol estimates K(SP) from 10(-3) to 10(-7) M, the dynamic range of the assay could be expanded by adjusting drug and counter-ion concentrations.

Rapid throughput solubility screening method for BCS class II drugs in animal GI fluids and simulated human GI fluids using a 96-well format

A rapid solubility-screening assay was developed with a focus on Biopharmaceutic Classification Scheme (BCS) class II drug solubility in animal and simulated human gastrointestinal (GI) fluids. The assay enables biologically promising drug leads to be evaluated for solubility limitations earlier in the drug development process, minimizes GI fluid needs, and produces in vitro solubility information with potential in vivo implications. A number of BCS II drugs were dissolved in DMSO at approximately 40 mM, and robotically distributed to a 96-well plate. The DMSO was evaporated and drugs were equilibrated with selected GI fluids, both fed and fasted states. After equilibration, precipitated wells were subjected to HPLC analysis. A spreadsheet calculated solubility automatically from HPLC output. Intra-day, inter-day, and inter-plate reproducibility were within 15% RSTD for the tested drugs with the primary source of variability being injection precision of our injector system. The reported solubility from screening assays was well correlated with literature data (r(2) = 0.80) with a slope of 0.86 and (r(2) = 0.99) with a slope of 0.89. This screening assay converts conventional solubility measurements to a 96-well format for increased throughput (>12 samples/h), reduces fluid needs, and minimizes drug consumption.

Fluorescence quenching studies of bovine growth hormone in several conformational states

The use of steady-state fluorescence quenching methods is reported as a probe of the accessibility of the single fluorescent tryptophan residue of bovine growth hormone (bGH, bovine somatotropin, bSt) in four solution-state conformations. Different bGH conformations were prepared by using previous knowledge of the multi-state nature of the equilibrium unfolding pathway for bGH: alterations in denaturant and protein concentration yielded different bGH conformations (native, monomeric intermediate, associated intermediate and unfolded). Because the intramolecular fluorescence quenching which occurs in the native state is reduced when the protein unfolds to any of the other conformations, steady-state fluorescence intensity measurements can be used to monitor bGH unfolding as well as the formation of the associated intermediate. These steady-state intensity changes have been confirmed with fluorescence lifetime measurements for the different conformational states of bGH. Fluorescence quenching results were obtained using the quenchers iodide (ionic), acrylamide (polar) and trichloroethanol (non-polar). Analysis of the results for native-state bGH reveals that the tryptophan environment is slightly non-polar (in agreement with the emission maximum of 335 nm) and the tryptophan is more exposed to acrylamide than most native-state tryptophan residues which have been studied. The tryptophan is most accessible to all quenchers in the unfolded state, because no steric restrictions inhibit quencher interaction with the tryptophan residue. The iodide quenching results indicate that the associated intermediate tryptophan is not accessible to iodide, probably due to negative charges inhibiting iodide penetration. The associated intermediate tryptophan is less accessible to all three quenchers than the monomeric intermediate tryptophan, due to tight packing of molecules in the associated intermediate state.

Pump/probe method for fast analysis of visible spectral signatures utilizing asynchronous optical sampling

We report the results from a new pump/probe spectrometer for potential use in combustion diagnostics that employs asynchronous optical sampling. The instrument consists of two frequency-doubled mode-locked Nd:YAG lasers operating at slightly different repetition rates, synchronously pumping two dye lasers (rhodamine 6G) to generate the pump and probe beams. The spectral and temporal capabilities of the instrument are examined by obtaining a spectrum and an excited state decay of rhodamine B. The instrument response is shown to be proportional to pump power, probe power, and sample absorptance. Different frequency synthesizers and different modes of triggering are used to study their effect on signal stability.