John L. Buchanan

Identification of a potent, state-dependent inhibitor of Nav1.7 with oral efficacy in the formalin model of persistent pain.

Clinical human genetic studies have recently identified the tetrodotoxin (TTX) sensitive neuronal voltage gated sodium channel Nav1.7 (SCN9A) as a critical mediator of pain sensitization. Herein, we report structure-activity relationships for a novel series of 2,4-diaminotriazines that inhibit hNav1.7. Optimization efforts culminated in compound 52, which demonstrated pharmacokinetic properties appropriate for in vivo testing in rats. The binding site of compound 52 on Nav1.7 was determined to be distinct from that of local anesthetics. Compound 52 inhibited tetrodotoxin-sensitive sodium channels recorded from rat sensory neurons and exhibited modest selectivity against the hERG potassium channel and against cloned and native tetrodotoxin-resistant sodium channels. Upon oral administration to rats, compound 52 produced dose- and exposure-dependent efficacy in the formalin model of pain.

Discovery and Optimization of a Novel Series of N-Arylamide Oxadiazoles as Potent, Highly Selective and Orally Bioavailable Cannabinoid Receptor 2 (CB2) Agonists

The CB2 receptor is an attractive therapeutic target for analgesic and anti-inflammatory agents. Herein we describe the discovery of a novel class of oxadiazole derivatives from which potent and selective CB2 agonist leads were developed. Initial hit 7 was identified from a cannabinoid target-biased library generated by virtual screening of sample collections using a pharmacophore model in combination with a series of physicochemical filters. 7 was demonstrated to be a selective CB2 agonist (CB2 EC50 = 93 nM, Emax = 98%, CB1 EC50 > 10 microM). However, this compound exhibited poor solubility and relatively high clearance in rat, resulting in low oral bioavailability. In this paper, we report detailed SAR studies on 7 en route toward improving potency, physicochemical properties, and solubility. This effort resulted in identification of 63 that is a potent and selective agonist at CB2 (EC50 = 2 nM, Emax = 110%) with excellent pharmacokinetic properties.

Development of Novel Dual Binders as Potent, Selective, and Orally Bioavailable Tankyrase Inhibitors

Tankyrases (TNKS1 and TNKS2) are proteins in the poly ADP-ribose polymerase (PARP) family. They have been shown to directly bind to axin proteins, which negatively regulate the Wnt pathway by promoting β-catenin degradation. Inhibition of tankyrases may offer a novel approach to the treatment of APC-mutant colorectal cancer. Hit compound 8 was identified as an inhibitor of tankyrases through a combination of substructure searching of the Amgen compound collection based on a minimal binding pharmacophore hypothesis and high-throughput screening. Herein we report the structure- and property-based optimization of compound 8 leading to the identification of more potent and selective tankyrase inhibitors 22 and 49 with improved pharmacokinetic properties in rodents, which are well suited as tool compounds for further in vivo validation studies.

Discovery and hit-to-lead optimization of pyrrolopyrimidines as potent, state-dependent Nav1.7 antagonists

Herein we describe the discovery, optimization, and structure-activity relationships of novel potent pyrrolopyrimidine Na(v)1.7 antagonists. Hit-to-lead SAR studies of the pyrrolopyrimidine core, head, and tail groups of the molecule led to the identification of pyrrolopyrimidine 48 as exceptionally potent Na(v)1.7 blocker with good selectivity over hERG and improved microsomal stability relative to our hit molecule and pyrazolopyrimidine 8 as a promising starting point for future optimization efforts.

Structural modifications of N-arylamide oxadiazoles : Identification of N-arylpiperidine oxadiazoles as potent and selective agonists of CB2

Structural modifications to the central portion of the N-arylamide oxadiazole scaffold led to the identification of N-arylpiperidine oxadiazoles as conformationally constrained analogs that offered improved stability and comparable potency and selectivity. The simple, modular scaffold allowed for the use of expeditious and divergent synthetic routes, which provided two-directional SAR in parallel. Several potent and selective agonists from this novel ligand class are described.

Discovery of 2,4-bis-arylamino-1,3-pyrimidines as insulin-like growth factor-1 receptor (IGF-1R) inhibitors

The insulin-like growth factor-1 receptor (IGF-1R) plays an important role in the regulation of cell growth and differentiation, and in protection from apoptosis. IGF-1R has been shown to be an appealing target for the treatment of human cancer. Herein, we report the synthesis, structure-activity relationships (SAR), X-ray cocrystal structure and in vivo tumor study results for a series of 2,4-bis-arylamino-1,3-pyrimidines.

Discovery and optimization of aminopyrimidinones as potent and state-dependent Nav1.7 antagonists

Clinical genetic data have shown that the product of the SCN9A gene, voltage-gated sodium ion channel Nav1.7, is a key control point for pain perception and a possible target for a next generation of analgesics. Sodium channels, however, historically have been difficult drug targets, and many of the existing structure-activity relationships (SAR) have been defined on pharmacologically modified channels with indirect reporter assays. Herein we describe the discovery, optimization, and SAR of potent aminopyrimidinone Nav1.7 antagonists using electrophysiology-based assays that measure the ligand-receptor interaction directly. Within this series, rapid functionalization at the polysubstituted aminopyrimidinone head group enabled exploration of SAR and of pharmacokinetic properties. Lead optimized N-Me-aminopyrimidinone 9 exhibited improved Nav1.7 potency, minimal off-target hERG liability, and improved rat PK properties.

Abstract 1621: Discovery of pyridyl pyrrolopyridinones as potent and selective CK1γ inhibitors

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA The canonical Wnt pathway regulates the ability of β-catenin to activate specific target genes. Aberrant activation of the Wnt pathway is believed to drive the development and growth of many cancers; for example, APC mutations were observed in >80% of the sporadic colorectal cancers. The casein kinase 1 (CK1) family of serine/threonine protein kinases is highly conserved. Multiple members of the CK1 family are shown to regulate the Wnt pathway through interactions with various proteins. The central role of CK1γ in Wnt signal transduction makes it an attractive target for the treatment of Wnt-pathway dependent cancers. We employed a structure-based approach and identified a series of pyridyl pyrrolopyridinones as potent and selective CK1γ inhibitors. These compounds exhibited good enzyme and cell potency, as well as selectivity against other CK1 isoforms, and favorable rodent PK profiles. Oral dosing of optimized lead compounds resulted in significant inhibition of LRP6 phosphorylation in a mouse tumor PD model. Citation Format: Hongbing Huang, Lisa Acquaviva, Howard Bregman, John Buchanan, Nagasree Chakka, Erin F. DiMauro, Jennifer Dovey, Hakan Gunaydin, Zihao Hua, Xin Huang, Liyue Huang, Vinod F. Patel, Matthew W. Martin, Randy Serafino, Cindy Wilson. Discovery of pyridyl pyrrolopyridinones as potent and selective CK1γ inhibitors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1621. doi:10.1158/1538-7445.AM2014-1621