New drugs introduced to the market are privileged structures having affinities for biological targets implicated in human diseases and conditions. These new chemical entities (NCEs), particularly small molecules and antibody–drug conjugates, provide insight into molecular recognition and simultaneously function as leads for the design of future medicines. This review is part of a continuing series presenting the most likely process-scale synthetic approaches to 40 NCEs approved for the first time anywhere in the world in 2019.

Oral delivery of previously disclosed purine and benzimidazole fructose-1,6-bisphosphatase (FBPase) inhibitors via prodrugs failed, which was likely due to their high molecular weight (>600). Therefore, a smaller scaffold was desired, and a series of phosphonic acid-containing thiazoles, which exhibited high potency against human liver FBPase (IC(50) of 10-30 nM) and high selectivity relative to other 5'-adenosinemonophosphate (AMP)-binding enzymes, were discovered using a structure-guided drug design approach. The initial lead compound (30j) produced profound glucose lowering in rodent models of type 2 diabetes mellitus (T2DM) after parenteral administration. Various phosphonate prodrugs were explored without success, until a novel phosphonic diamide prodrug approach was implemented, which delivered compound 30j with good oral bioavailability (OBAV) (22-47%). Extensive lead optimization of both the thiazole FBPase inhibitors and their prodrugs culminated in the discovery of compound 35n (MB06322) as the first oral FBPase inhibitor advancing to human clinical trials as a potential treatment for T2DM.

Efforts to enhance the inhibitory potency of the initial purine series of fructose-1,6-bisphosphatase (FBPase) inhibitors led to the discovery of a series of benzimidazole analogues with human FBPase IC(50)s < 100 nM. Inhibitor 4.4 emerged as a lead compound based on its potent inhibition of human liver FBPase (IC(50) = 55 nM) and significant glucose lowering in normal fasted rats. Intravenous administration of 4.4 to Zucker diabetic fatty rats led to rapid and robust glucose lowering, thereby providing the first evidence that FBPase inhibitors could improve glycemia in animal models of type 2 diabetes.

Apoptosis signal-regulating kinase 1 (ASK1/ MAP3K) is a mitogen-activated protein kinase family member shown to contribute to acute ischemia/reperfusion injury. Using structure-based drug design, deconstruction, and reoptimization of a known ASK1 inhibitor, a lead compound was identified. This compound displayed robust MAP3K pathway inhibition and reduction of infarct size in an isolated perfused heart model of cardiac injury. KEYWORDS:Apoptosis signal-regulating kinase 1 (ASK1), structure-based drug design (SBDD), cardiac injury A poptosis signal-regulating kinase 1 (ASK1) is a mitogenactivated protein kinase kinase kinase (MAP3K) family member residing upstream of both Jun N-terminal kinase (JNK) and p38. ASK1 is capable of activating JNK and P38 via the phosphorylation of intermediate kinases. ASK1 plays a role in the mammalian cell stress response and the induction of apoptotic cell death. It also contributes to a range of systemic diseases including heart failure 1 and acute ischemia/reperfusion injury, by reducing structural and functional integrity of the mitochondria in cardiac cells. 2−4 ASK1-deficient mice display reduced levels of cardiomyocyte apoptosis, hypertrophy, and interstitial fibrosis. 5 Thus, selective inhibition of ASK1 represents an attractive strategy for slowing or potentially reversing harmful tissue changes associated with various forms of heart failure.Using ASK1 structural information and deconstruction of known ASK1 inhibitors such as 1 and 2 (Figure 1), our research team generated a novel, potent, and orally bioavailable ASK1 inhibitor with favorable physicochemical properties to help further elucidate the role of ASK1 in cardiac injury. Compound 1 was an early lead for Takeda's ASK1 inhibitor program. 6 Compound 2 (GS-4997, Gilead Sciences) is a clinical stage ASK1 inhibitor, which has been evaluated as an experimental treatment for diabetic nephropathy and kidney fibrosis. 7 Key structural features with respect to ligand interactions within the ATP binding site were identified using our internal database as well as public domain crystal structures of small molecules in ASK1 and published pharmacophore models. 8,9 Figure 1 illustrates the cocrystal structure of 1 in hASK1 (PDB: 3VW6) and highlights the key interactions between 1 and the ASK1 ATP binding pocket. Binding to the kinase hinge is characterized by a hydrogen bonding interaction with the

Background: 5-HT 4 receptor (5-HT 4 R) agonists exert prokinetic actions in the GI tract, but non-selective actions and potential for stimulation of non-target 5-HT 4 Rs have limited their use. Since 5-HT 4 Rs are expressed in the colonic epithelium and their stimulation accelerates colonic propulsion in vitro, we tested whether luminally acting 5-HT 4 R agonists promote intestinal motility. Methods: Non-absorbed 5-HT 4 R agonists, based on prucalopride and naronapride, were assessed for potency at the 5-HT 4 R in vitro, and for tissue and serum distribution in vivo in mice. In vivo assessment of prokinetic potential included whole gut transit, colonic motility, fecal output, and fecal water content. Colonic motility was also studied ex vivo in mice treated in vivo. Immunofluorescence was used to evaluate receptor distribution in human intestinal mucosa. Key Results: Pharmacological screening demonstrated selectivity and potency of test agonists for 5-HT 4 R. Bioavailability studies showed negligible serum detection. Gavage of agonists caused faster whole gut transit and colonic motility, increased fecal output, and elevated fecal water content. Prokinetic actions were blocked by a 5-HT 4 R antagonist and were not detected in 5-HT 4 R knockout mice. Agonist administration promoted motility in models of constipation. Evaluation of motility patterns ex vivo revealed enhanced contractility in the middle and distal colon. Immunoreactivity for 5-HT 4 R is present in the epithelial layer of the human small and large intestines. Conclusions and Inferences: These findings demonstrated that stimulation of epithelial 5-HT 4 Rs can potentiate propulsive motility and support the concept that mucosal 5-HT 4 Rs could represent a safe and effective therapeutic target for the treatment of constipation.