Tony P. Tang

Identification of Benzoxazin-3-one Derivatives as Novel, Potent, and Selective Nonsteroidal Mineralocorticoid Receptor Antagonists

Mineralocorticoid receptor (MR) blockade has come into focus as a promising approach for the treatment of cardiovascular diseases such as hypertension and congestive heart failure. In order to identify a novel class of nonsteroidal MR antagonists that exhibit significant potency and good selectivity over other steroidal hormone receptors, we designed a novel series of benzoxazin-3-one derivatives and synthesized them from 6-(7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-6-yl)-2H-1,4-benzoxazin-3(4H)-one (1a), high-throughput screening (HTS) hit compound. Our design was based on a crystal structure of an MR/compound complex and a docking model. In the course of lead generation from 1a, a 1,2-diaryl framework was characterized as a key structure with high binding affinity. On the basis of scaffold hopping and optimization studies, benzoxazin-3-one derivatives possessing 1-phenyl-3-trifluoromethylpyrazol-5-yl moiety at the 6-position were identified as a novel series of potent and selective MR antagonists. Among these compounds, 6-[1-(4-fluoro-2-methylphenyl)-3-(trifluoromethyl)-1H-pyrazol-5-yl]-2H-1,4-benzoxazin-3(4H)-one (14n) showed highly potent activity and good selectivity and also exhibited a significant antihypertensive effect in deoxycorticosterone acetate-salt hypertensive rats. On the basis of these results, compound 14n was progressed for further pharmacological evaluation.

Design, synthesis, and structure-activity relationships of dihydrofuran-2-one and dihydropyrrol-2-one derivatives as novel benzoxazin-3-one-based mineralocorticoid receptor antagonists.

Dihydrofuran-2-one and dihydropyrrol-2-one derivatives were identified as novel, potent and selective mineralocorticoid receptor (MR) antagonists by the structure-based drug design approach utilizing the crystal structure of MR/compound complex. Introduction of lipophilic substituents directed toward the unfilled spaces of the MR and identification of a new scaffold, dihydropyrrol-2-one ring, led to potent in vitro activity. Among the synthesized compounds, dihydropyrrol-2-one 11i showed an excellent in vitro activity (MR binding IC50=43nM) and high selectivity over closely related steroid receptors such as the androgen receptor (AR), progesterone receptor (PR) and glucocorticoid receptor (GR) (>200-fold for AR and PR, 100-fold for GR).

Discovery of 6-[5-(4-fluorophenyl)-3-methyl-pyrazol-4-yl]-benzoxazin-3-one derivatives as novel selective nonsteroidal mineralocorticoid receptor antagonists

In the course of our study on selective nonsteroidal mineralocorticoid receptor (MR) antagonists, a series of novel benzoxazine derivatives possessing an azole ring as the core scaffold was designed for the purpose of attenuating the partial agonistic activity of the previously reported dihydropyrrol-2-one derivatives. Screening of alternative azole rings identified 1,3-dimethyl pyrazole 6a as a lead compound with reduced partial agonistic activity. Subsequent replacement of the 1-methyl group of the pyrazole ring with larger lipophilic side chains or polar side chains targeting Arg817 and Gln776 increased MR binding activity while maintaining the agonistic response at the lower level. Among these compounds, 6-[1-(2,2-difluoro-3-hydroxypropyl)-5-(4-fluorophenyl)-3-methyl-1H-pyrazol-4-yl]-2H-1,4-benzoxazin-3(4H)-one (37a) showed highly potent in vitro activity, high selectivity versus other steroid hormone receptors, and good pharmacokinetic profiles. Oral administration of 37a in deoxycorticosterone acetate-salt hypertensive rats showed a significant blood pressure-lowering effect with no signs of antiandrogenic effects.

Abstract C196: Identification of first-in-class, highly potent FGFR kinase inhibitors that spare FGFR1

Background: The fibroblast growth factor receptor (FGFR1-4) family of tyrosine kinases plays an important role in normal physiologic processes, including angiogenesis, wound healing and regulation of calcium and phosphate metabolism. In addition, dysregulation of FGFR signaling through genetic alterations or altered expression of individual receptors and their ligands has been frequently observed in human tumors. While tyrosine kinase inhibitors (TKIs) with anti-FGFR activity have produced clinical responses in patients whose tumors harbor FGFR alterations, currently available FGFR TKIs inhibit multiple other kinases, including multiple FGFRs. As a result, dose-limiting toxicities have been frequently observed in patients, including hyperphosphatemia which may arise from the inhibition of FGFR1 in the kidney. These toxicities may ultimately limit the efficacy of pan-FGFR inhibitors. However, the ability to develop inhibitors that spare individual FGFRs has been hampered by the high degree of structural similarity between FGFR1, FGFR2, and FGFR3. The development of these tools to distinguish the functional contributions of the individual FGF receptors not only advances the biological understanding of the individual receptors in the context of their expression but may also provide therapeutic agents that have an improved therapeutic index. Methods: In vitro and in vivo evaluations including both enzyme and cell-based assays, pharmacokinetic (PK) studies, measurement of drug metabolism and non-clinical safety evaluation were conducted using standard methods. Tumor growth inhibition and pharmacodynamics (PD) measurements were carried out using subcutaneous xenografts of RT112/84 (which harbor an FGFR3-TACC fusion) bladder cancer cells in nude mice. Results: We have developed compounds with nanomolar FGFR3 enzyme and cell potency, but relatively spare FGFR1 and have minimal activity against an enzyme panel of >200 diverse kinases. This series was further optimized to provide high oral exposure in rodent species. One representative compound was evaluated in a single dose mouse PK at doses of 10, 30 and 100 mg/kg and provided predicted pharmacokinetic coverage of the FGFR3 cell IC50 for >8, >12 and >24 hrs respectively, which correlated with phospho-FGFR3 reduction. The compound demonstrated greater than 40% and greater than 65% tumor regressions of RT112/84 subcutaneous xenografts at doses of 30 and 45 mg/kg/day x 14 day, respectively. These doses were well tolerated and minimal hyperphosphatemia was observed. Conclusions: We have identified potent and selective FGFR inhibitors that spare FGFR1 and other related kinases, and possess high oral bioavailability and favorable PK properties in animals. This next-generation class of compounds will be able to examine selectively the biology of selective FGFR inhibition. The identification of potent and selective FGFR inhibitors with minimal activity against FGFR1 may improve the efficacy and tolerability compared to the currently available pan-FGFR inhibitors. Citation Format: Shannon Winski, Nisha Nanda, Eric Brown, Tony Tang, Barbara Brandhuber, Robyn Hamor, Brian Tuch, Kevin Ebata, Jennifer Low, Francis Sullivan, Darin Smith, Guy Vigers, Megan Strough, Rob Rieger, James Blake, David Moreno, David Chantry, S. Michael Rothenberg, Steven Andrews. Identification of first-in-class, highly potent FGFR kinase inhibitors that spare FGFR1. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C196.