Keith T. Demarest

Effect of canagliflozin on renal threshold for glucose, glycemia, and body weight in normal and diabetic animal models.

Background Canagliflozin is a sodium glucose co-transporter (SGLT) 2 inhibitor in clinical development for the treatment of type 2 diabetes mellitus (T2DM). Methods 14C-alpha-methylglucoside uptake in Chinese hamster ovary-K cells expressing human, rat, or mouse SGLT2 or SGLT1; 3H-2-deoxy-d-glucose uptake in L6 myoblasts; and 2-electrode voltage clamp recording of oocytes expressing human SGLT3 were analyzed. Graded glucose infusions were performed to determine rate of urinary glucose excretion (UGE) at different blood glucose (BG) concentrations and the renal threshold for glucose excretion (RTG) in vehicle or canagliflozin-treated Zucker diabetic fatty (ZDF) rats. This study aimed to characterize the pharmacodynamic effects of canagliflozin in vitro and in preclinical models of T2DM and obesity. Results Treatment with canagliflozin 1 mg/kg lowered RTG from 415±12 mg/dl to 94±10 mg/dl in ZDF rats while maintaining a threshold relationship between BG and UGE with virtually no UGE observed when BG was below RTG. Canagliflozin dose-dependently decreased BG concentrations in db/db mice treated acutely. In ZDF rats treated for 4 weeks, canagliflozin decreased glycated hemoglobin (HbA1c) and improved measures of insulin secretion. In obese animal models, canagliflozin increased UGE and decreased BG, body weight gain, epididymal fat, liver weight, and the respiratory exchange ratio. Conclusions Canagliflozin lowered RTG and increased UGE, improved glycemic control and beta-cell function in rodent models of T2DM, and reduced body weight gain in rodent models of obesity.

Human cardiomyocytes express high level of Na+/glucose cotransporter 1 (SGLT1)

We have quantitatively measured gene expression for the sodium‐dependent glucose cotransporters 1 and 2 (SGLT1 and SGLT2) in 23 human tissues using the method of real time PCR. As predicted, our results revealed that the expression of SGLT1 was very high in the small intestine (1.2Eu2009+u20096 molecules/μg total RNA) relative to that in the kidney (3Eu2009+u20094 molecules/μg total RNA). Surprisingly, we observed that the expression of SGLT1 in human heart was unexpectedly high (3.4Eu2009+u20095 molecules/μg total RNA), approximately 10‐fold higher than that observed in kidney tissue. DNA sequencing confirmed that the PCR amplified fragment was indeed the human SGLT1 gene. Moreover, in situ hybridization studies using a digoxigenin (DIG)‐labeled antisense cRNA probe corresponding to human SGLT1 cDNA confirm that human cardiomyocytes express SGLT1 mRNA. In contrast, the expression of SGLT2 in human tissues appears to be ubiquitous, with levels ranging from 6.7Eu2009+u20094 molecules/μg total RNA (in skeletal muscle) to 3.2Eu2009+u20096 molecules/μg total RNA (in kidney), levels 10–100‐fold higher than the expression of SGLT1 in the same tissues. Our finding that human cardiomyocytes express high levels of SGLT1 RNA suggests that SGLT1 may have a functional role in cardiac glucose transport. Since several SGLT inhibitors are currently in development as potential anti‐diabetic agents, it may be important to assess the functional consequences of inhibition of SGLT1 in the heart. J. Cell. Biochem. 90: 339–346, 2003.

Discovery of fused bicyclic agonists of the orphan G-protein coupled receptor GPR119 with in vivo activity in rodent models of glucose control.

We herein outline the design of a new series of agonists of the pancreatic and GI-expressed orphan G-protein coupled receptor GPR119, a target that has been of significant recent interest in the field of metabolism, starting from our prototypical agonist AR231453. A number of key parameters were improved first by incorporation of a pyrazolopyrimidine core to create a new structural series and secondly by the introduction of a piperidine ether group capped with a carbamate. Chronic treatment with one compound from the series, 3k, showed for the first time that blood glucose and glycated hemoglobin (HbA1c) levels could be significantly reduced in Zucker Diabetic Fatty (ZDF) rats over several weeks of dosing. As a result of these and other data described here, 3k (APD668, JNJ-28630368) was the first compound with this mechanism of action to be progressed into clinical development for the treatment of diabetes.

Design and synthesis of potent inhibitors of cholesteryl ester transfer protein (CETP) exploiting a 1,2,3,4-tetrahydroquinoline platform.

Tetrahydroquinoline A is a potent inhibitor of the cholesterol ester transfer protein (CETP), a target for the treatment of low HDL-C and atherosclerosis. Low HDL-C has been identified as a key risk factor for cardiovascular disease in addition to high LDL-C, the target of the statin drugs. Tetrahydroquinoline A inhibits partially purified CETP with an IC(50) of 39nM. The preparation of a series of potent inhibitors of CETP designed around a 1,2,3,4-tetrahydroquinoline platform will be discussed.

Macrocyclic bisindolylmaleimides as inhibitors of protein kinase C and glycogen synthase kinase-3

Efficient methods were developed to synthesize a novel series of macrocyclic bisindolylmaleimides containing linkers with multiple heteroatoms. Potent inhibitors (single digit nanomolar IC(50)) for PKC-beta and GSK-3beta were identified, and compounds showed good selectivity over PKC-alpha, -gamma, -delta, -epsilon, and -zeta. Representative compound 5a also had high selectivity in a screening panel of 10 other protein kinases. In cell-based functional assays, several compounds effectively blocked interleukin-8 release induced by PKC-betaII and increased glycogen synthase activity by inhibiting GSK-3beta.

Discovery of a second generation agonist of the orphan G-protein coupled receptor GPR119 with an improved profile

The design and synthesis of a second generation GPR119-agonist clinical candidate for the treatment of diabetes is described. Compound 16 (APD597, JNJ-38431055) was selected for preclinical development based on a good balance between agonist potency, intrinsic activity and in particular on its good solubility and reduced drug-drug interaction potential. In addition, extensive in vivo studies showed a more favorable metabolic profile that may avoid the generation of long lasting metabolites with the potential to accumulate in clinical studies.

Topiramate ameliorates hyperglycaemia and improves glucose-stimulated insulin release in ZDF rats and db/db mice

Topiramate (TPM) is a novel neurotherapeutic agent. Clinical studies reported that TPM treatment reduced body weight and decreased fasting blood glucose levels in obese patients with or without type 2 diabetes. It is unclear whether the blood glucose‐normalizing phenomenon observed during TPM treatment is a primary effect or the consequence of reduced food intake and weight loss. In the present studies, we chronically treated female Zucker diabetic fatty (ZDF) rats (fed with a diabetogenic diet) and db/db mice with TPM (30–300u2003mg/kg/day) to examine the effect of TPM on hyperglycaemia and its relationship with food intake and body weight gain. Our data showed that TPM treatment markedly reduced blood glucose levels in both ZDF rats and db/db mice without a significant reduction in body weight gain. Pair‐fed db/db mice treated with the vehicle alone did not exhibit a significant decrease in blood glucose levels compared with mice fed ad libitum. TPM treatment increased glucose‐stimulated insulin release by 2–3‐fold during an oral glucose tolerance test in both ZDF rats and db/db mice. We also observed a 1.4‐fold increase of pancreatic insulin content and heightened insulin immunostaining in pancreatic β cells in db/db mice treated with TPM. Our data suggest that the antidiabetic effect of TPM is independent of the changes in body weight gain and food intake. Improved glucose‐induced insulin release may, in part, underlie the mechanisms by which TPM ameliorates the hyperglycaemia.

Synthesis and biological evaluation of novel indoloazepine derivatives as non-peptide vasopressin V2 receptor antagonists.

A series of novel 3,4,5,6-tetrahydro-1H-azepino[4,3,2-cd]indoles was synthesized and tested for vasopressin receptor antagonist activity. We identified compounds with high affinity for the human V2 receptor and good selectivity over the human V1a receptor. Compound 6c bound to V2 receptors with an IC(50) value of 20 nM, had >100-fold selectivity over V1a receptors, and inhibited cAMP formation in a cellular V2 functional assay with an IC(50) value of 70 nM.

Synthesis and discovery of 2,3-dihydro-3,8-diphenylbenzo[1,4]oxazines as a novel class of potent cholesteryl ester transfer protein inhibitors.

2,3-Dihydro-3,8-diphenylbenzo[1,4]oxazines were identified as a new class of potent cholesteryl ester transfer protein inhibitors. The most potent compound 6a (IC50=26 nM) possessed a favorable pharmacokinetic profile with good oral bioavailability in rat (F=53%) and long human liver microsome stability (t(1/2)=62 min). It increased HDL-C in human CETP transgenic mice and high-fat fed hamsters. The structure and activity relationship of this series will be described in this Letter.

Improvement of dyslipidemia, insulin sensitivity, and energy balance by a peroxisome proliferator–activated receptor α agonist

Peroxisome proliferator-activated receptor alpha (PPARalpha) is a member of the nuclear receptor family of ligand-activated transcription factors. It plays an important role in the regulation of genes involved in lipid metabolism and transport. Compound A is a potent and orally active PPARalpha agonist that activated both human and rat PPARalpha receptors. The compound induced the expression of genes involved in fatty acid metabolism in a rodent hepatoma cell line and in the liver of db/db mouse. The ability of compound A to stimulate fatty acid beta-oxidation was demonstrated in human hepatocytes and human skeletal muscle cells, which confirmed a functional activation of PPARalpha-mediated activities. Compound A was shown to be a more potent and efficacious antidyslipidemic agent in atherogenic rat and db/db mouse models as compared with fenofibrate. The increase in high-density lipoprotein cholesterol levels by compound A was at least partially due to an increase in serum apolipoprotein A-I protein concentrations in human PPARalpha transgenic mouse. The triglyceride-lowering effect was further confirmed in a higher species, obese dog models. In addition, compound A dose-dependently ameliorated hyperglycemia and hyperinsulinemia, and improved glucose tolerance in db/db mice. In a diet-induced obesity mouse model, compound A decreased body weight mainly by increasing energy expenditure and reducing fat deposition. In conclusion, the novel and potent PPARalpha agonist improves lipid profile, insulin sensitivity, and energy balance in animal models.