In cardiac myocytes, regulation of mitochondrial Ca2+ is important for cellular signaling and cardiac contraction. Ca2+ entry into the mitochondria is mediated by a highly selective Ca2+ channel called the mitochondrial calcium uniporter, which consists of a pore-forming subunit MCU and regulatory subunits such as MICU1. Although pharmacological regulation of the mitochondrial Ca2+ influx is a promising approach to controlling the cellular functions, a cell-permeable and specific inhibitor of the mitochondrial calcium uniporter has not yet been developed. Here, we identify a novel cell-permeable inhibitor of the uniporter by a high-throughput screening of 120 000 small-molecule compounds. In our study, DS16570511 dose-dependently inhibited serum-induced mitochondrial Ca2+ influx in HEK293A cells with an IC50 of 7 μM. DS16570511 inhibited Ca2+ uptake of isolated mitochondria from human cells, rat heart and pig heart. Overexpression of hMCU or hMICU1 in HEK293A cells increased mitochondrial Ca2+ influx, and the increases were completely suppressed by the pretreatment with DS16570511. DS16570511 also blocks mitochondrial Ca2+ overload in a Langendorff perfused beating rat heart. Interestingly, DS16570511 increased cardiac contractility without affecting heart rate in the perfused heart. These results show that DS16570511 is a novel cell-permeable inhibitor of the mitochondrial calcium uniporter and applicable for control of the cardiac functions.

GPR142 is a G protein-coupled receptor that is predominantly expressed in pancreatic β-cells. GPR142 agonists stimulate insulin secretion in the presence of high glucose concentration, so that they could be novel insulin secretagogues with reduced or no risk of hypoglycemia. We report here the optimization of HTS hit compound 1 toward a proof of concept compound 33, which showed potent glucose lowering effects during an oral glucose tolerance test in mice and monkeys.

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Herein, we report the lead optimization of amrinone−phenylalanine based GPR142 agonists. Structure− activity relationship studies led to the discovery of aminopyrazole−phenylalanine carboxylic acid 22, which exhibited good agonistic activity, high target selectivity, desirable pharmacokinetic properties, and no cytochrome P450 or hERG liability. Compound 22, together with its orally bioavailable ethyl ester prodrug 23, were found to be suitable for in vivo proof-of-concept studies. Compound 23 displayed good efficacy in a mouse oral glucose tolerance test (OGTT). Compound 22 showed GPR142 dependent stimulation of insulin secretion in isolated mouse islets and demonstrated a statistically significant glucose lowering effect in a mouse model bearing transplanted human islets. KEYWORDS: GPR142 agonist, type 2 diabetes, aminopyrazole−phenylalanine, insulin secretagogue, prodrug, oral glucose tolerance test, human islet transplant G PR142, a new member in the super family of seventransmembrane G-protein-coupled receptors (GPCRs), was first reported in 2003 by Schioth and colleagues, 1 and further characterized by Schaller in 2006. 2 GPR142 is a G qcoupled receptor that was expressed predominantly in pancreatic β-cells. Activation of this receptor triggers an intracellular signal transduction pathway, which ultimately leads to β-cell insulin secretion. Tryptophan was recently identified as an endogenous ligand for GPR142. 3 Activation of the receptor by tryptophan was found to stimulate insulin secretion in isolated mouse islets in both a dose-and a glucosedependent manner and was associated with improved glucose tolerance. 3 These findings suggested that GPR142 plays an important role in regulating insulin secretion and glucose homeostasis. This target was therefore deemed suitable for the discovery of agents for the treatment of type II diabetes with a low associated risk of hypoglycemia.We recently reported the discovery of amrinone−phenylalanine GPR142 agonist 1 4 and the subsequent optimization campaign, which provided 2 for preliminary proof-of-concept studies in rodents. 5 While these compounds were both highly potent in a human inositol phosphate (IP) accumulation assay 6 (EC 50 = 0.090 μM for 1 and EC 50 = 0.058 μM for 2), they both suffered from high in vivo clearance, with rat IV clearance of 3.4 and 5.1 L/h/kg, respectively (Figure 1). Compound 2 was also found to be a strong CYP inhibitor. While replacing the pyridone moiety of 1 with a thiadiazole ring was later discovered to reduce rat clearance, 5 this heterocyclic compound was found to be chemically unstable at physiological pH conditions. Further investigation of this chemical series was therefore warranted to address the above issues and to provide a better tool compound for in vivo proof-of-concept studies.We first investigated the role of the central aromatic ring on potency as summarized in Table 1. The strategy employed was to incorporate different heterocyclic rings at the center of the molecule in order to modulate the overall shape ...