EMPA

Following the results of the EMPA-REG OUTCOME trial with empagliflozin, is it possible to speak of a class effect?[Pubmed:28144158]

Int J Gen Med. 2017 Jan 13;10:23-26.

BACKGROUND: The recently published cardiovascular outcomes data for the first sodium-glucose cotransporter 2 (SGLT2) inhibitor, EMPAgliflozin, have shown cardiovascular safety and additional benefits in patients with type 2 diabetes and established cardiovascular disease. EMPAgliflozin showed lower rates of death from cardiovascular causes or from any causes and lower hospitalization rates from heart failure compared with placebo, both in addition to standard care. This commentary discusses the existence of a possible class effect considering the available evidence described for other SGLT2 inhibitors. MAIN TEXT: EMPAgliflozin, dapagliflozin and canagliflozin share the same mechanism of action, and it is a plausible hypothesis that some of the benefits of EMPAgliflozin treatment could also be expected from other SGLT2 inhibitors. However, the rapid and persistent occurrence of cardiovascular benefits observed with EMPAgliflozin and the different results shown by the three inhibitors in meta-analyses of some of their respective Phase II and III trials might suggest another possible mechanism of action, perhaps related to the different selectivity to inhibit SGLT-2 and other SGLT family members that these compounds present. CONCLUSION: There is still lack of evidence to answer whether the cardiovascular benefits observed with EMPAgliflozin in the EMPA-REG OUTCOME study could be seen as a "class effect", which is also attributable to dapagliflozin and canagliflozin.

Effects of reducing blood pressure on renal outcomes in patients with type 2 diabetes: Focus on SGLT2 inhibitors and EMPA-REG OUTCOME.[Pubmed:28153377]

Diabetes Metab. 2017 Apr;43(2):99-109.

EMPAgliflozin, a sodium-glucose cotransporter type 2 (SGLT2) inhibitor, has enabled remarkable reductions in cardiovascular and all-cause mortality as well as in renal outcomes in patients with type 2 diabetes (T2D) and a history of cardiovascular disease in the EMPA-REG OUTCOME. These results have been attributed to haemodynamic rather than metabolic effects, in part due to the osmotic/diuretic action of EMPAgliflozin and the reduction in arterial blood pressure (BP). The present narrative review includes the results of meta-analyses of trials evaluating the effects on renal outcomes of lowering BP in patients with T2D, with a special focus on the influence of baseline and achieved systolic BP, and compares the renal outcome results of the EMPA-REG OUTCOME with those of other major trials with inhibitors of the renin-angiotensin system in patients with T2D and the preliminary findings with other SGLT2 inhibitors, and also evaluates post hoc analyses from the EMPA-REG OUTCOME of special interest as regards the BP-lowering hypothesis and renal function. While systemic BP reduction associated to EMPAgliflozin therapy may have contributed to the renal benefits reported in EMPA-REG OUTCOME, other local mechanisms related to kidney homoeostasis most probably also played a role in the overall protection observed in the trial.

Vascular legacy: HOPE ADVANCEs to EMPA-REG and LEADER: A Surprising similarity.[Pubmed:28217527]

Indian J Endocrinol Metab. 2017 Jan-Feb;21(1):245-248.

Recently reported cardiovascular outcome studies on EMPAgliflozin (EMPA-REG) and liraglutide (LEADER) have spurred interest in this field of diabetology. This commentary compares and contrasts these studies with two equally important outcome trials conducted using blood pressure lowering agents. A comparison with MICROHOPE (using ramipril) and ADVANCE (using perindopril + indapamide) blood pressure arms throws up interesting facts. The degree of blood pressure lowering, dissociation between cardiovascular and cerebrovascular benefits, and discordance between renal and retinal outcomes are surprisingly similar in these trials, conducted using disparate molecules. The time taken to achieve such benefits is similar for all drugs except EMPAgliflozin. Such discussion helps inform rational and evidence-based choice of therapy and forms the framework for future research.

Empa's New Clothes: The Untold Story of the Empa-Reg Outcome Trial.[Pubmed:28300428]

Diabetes Technol Ther. 2017 Jun;19(6):324-327.

It is no secret that the diabetes community has been yearning for good news for quite some time. One outstanding issue undermining effective diabetes management has been the lack of demonstrable effects of glycemic interventions on cardiovascular (CV) outcome in people with type 2 diabetes. This, however, seems to have changed recently after the publication of the EMPA-Reg Outcome Trial. The study reported an impressive reduction in CV deaths that was observed within weeks of treatment with the diabetes agent, EMPAgliflozin. The results exceeded all expectations and was quickly embraced by a wide and receptive diabetes audience. Fans and admirers of the study have since set out to accommodate the new findings to reshape our diabetes practice guidelines. However, before everything becomes cast in stone, I believe there's another side to the story of the EMPA-Reg Outcome trial that the diabetes community needs to hear. Here, I debate the merits of the study and present the case as to why I think we might be led down the garden path by accepting this study at mere face value.

Orexin receptor 2 expression in the posterior hypothalamus rescues sleepiness in narcoleptic mice.[Pubmed:21368172]

Proc Natl Acad Sci U S A. 2011 Mar 15;108(11):4471-6.

Narcolepsy is caused by a loss of orexin/hypocretin signaling, resulting in chronic sleepiness, fragmented non-rapid eye movement sleep, and cataplexy. To identify the neuronal circuits underlying narcolepsy, we produced a mouse model in which a loxP-flanked gene cassette disrupts production of the orexin receptor type 2 (OX2R; also known as HCRTR2), but normal OX2R expression can be restored by Cre recombinase. Mice lacking OX2R signaling had poor maintenance of wakefulness indicative of sleepiness and fragmented sleep and lacked any electrophysiological response to orexin-A in the wake-promoting neurons of the tuberomammillary nucleus. These defects were completely recovered by crossing them with mice that express Cre in the female germline, thus globally deleting the transcription-disrupter cassette. Then, by using an adeno-associated viral vector coding for Cre recombinase, we found that focal restoration of OX2R in neurons of the tuberomammillary nucleus and adjacent parts of the posterior hypothalamus completely rescued the sleepiness of these mice, but their fragmented sleep was unimproved. These observations demonstrate that the tuberomammillary region plays an essential role in the wake-promoting effects of orexins, but orexins must stabilize sleep through other targets.

Mapping the binding pocket of dual antagonist almorexant to human orexin 1 and orexin 2 receptors: comparison with the selective OX1 antagonist SB-674042 and the selective OX2 antagonist N-ethyl-2-[(6-methoxy-pyridin-3-yl)-(toluene-2-sulfonyl)-amino]-N-pyridin-3-ylmet hyl-acetamide (EMPA).[Pubmed:20404073]

Mol Pharmacol. 2010 Jul;78(1):81-93.

The orexins and their receptors are involved in the regulation of arousal and sleep-wake cycle. Clinical investigation with almorexant has indicated that this dual OX antagonist is efficacious in inducing and maintaining sleep. Using site-directed mutagenesis, beta(2)-adrenergic-based OX(1) and OX(2) modeling, we have determined important molecular determinants of the ligand-binding pocket of OX(1) and OX(2). The conserved residues Asp(45.51), Trp(45.54), Tyr(5.38), Phe(5.42), Tyr(5.47), Tyr(6.48), and His(7.39) were found to be contributing to both orexin-A-binding sites at OX(1) and OX(2). Among these critical residues, five (positions 45.51, 45.54, 5.38, 5.42, and 7.39) were located on the C-terminal strand of the second extracellular loop (ECL2b) and in the top of TM domains at the interface to the main binding crevice, thereby suggesting superficial OX receptor interactions of orexin-A. We found that the mutations W214A(45.54), Y223A(5.38), F227A(5.42), Y317A(6.48), and H350A(7.39) resulted in the complete loss of both [(3)H]almorexant and [(3)H]N-ethyl-2-[(6-methoxy-pyridin-3-yl)-(toluene-2-sulfonyl)-amino]-N-pyridin-3 -ylmethyl-acetamide (EMPA) binding affinities and also blocked their inhibition of orexin-A-evoked [Ca(2+)](i) response at OX(2). The crucial residues Gln126(3.32), Ala127(3.33), Trp206(45.54), Tyr215(5.38), Phe219(5.42), and His344(7.39) are shared between almorexant and 1-(5-(2-fluoro-phenyl)-2-methyl-thiazol-4-yl)-1-((S)-2-(5-phenyl-(1,3,4)oxadiazol -2-ylmethyl)-pyrrolidin-1-yl)-methanone (SB-674042) binding sites in OX(1). The nonconserved residue at position 3.33 of orexin receptors was identified as occupying a critical position that must be involved in subtype selectivity and also in differentiating two different antagonists for the same receptor. In summary, despite high similarities in the ligand-binding pockets of OX(1) and OX(2) and numerous aromatic/hydrophobic interactions, the local conformation of helix positions 3.32, 3.33, and 3.36 in transmembrane domain 3 and 45.51 in ECL2b provide the structural basis for pharmacologic selectivity between OX(1) and OX(2).

Biochemical and behavioural characterization of EMPA, a novel high-affinity, selective antagonist for the OX(2) receptor.[Pubmed:19751316]

Br J Pharmacol. 2009 Apr;156(8):1326-41.

BACKGROUND AND PURPOSE: The OX(2) receptor is a G-protein-coupled receptor that is abundantly found in the tuberomammillary nucleus, an important site for the regulation of the sleep-wake state. Herein, we describe the in vitro and in vivo properties of a selective OX(2) receptor antagonist, N-ethyl-2-[(6-methoxy-pyridin-3-yl)-(toluene-2-sulphonyl)-amino]-N-pyridin-3-ylme thyl-acetamide (EMPA). EXPERIMENTAL APPROACH: The affinity of [(3)H]EMPA was assessed in membranes from HEK293-hOX(2)-cells using saturation and binding kinetics. The antagonist properties of EMPA were determined by Schild analysis using the orexin-A- or orexin-B-induced accumulation of [(3)H]inositol phosphates (IP). Quantitative autoradiography was used to determine the distribution and abundance of OX(2) receptors in rat brain. The in vivo activity of EMPA was assessed by reversal of [Ala(11),D-Leu(15)]orexin-B-induced hyperlocomotion during the resting phase in mice and the reduction of spontaneous locomotor activity (LMA) during the active phase in rats. KEY RESULTS: [(3)H]EMPA bound to human and rat OX(2)-HEK293 membranes with K(D) values of 1.1 and 1.4 nmol x L(-1) respectively. EMPA competitively antagonized orexin-A- and orexin-B-evoked accumulation of [(3)H]IP at hOX(2) receptors with pA(2) values of 8.6 and 8.8 respectively. Autoradiography of rat brain confirmed the selectivity of [(3)H]EMPA for OX(2) receptors. EMPA significantly reversed [Ala(11),D-Leu(15)]orexin-B-induced hyperlocomotion dose-dependently during the resting phase in mice. EMPA, injected i.p. in rats during the active phase, reduced LMA dose-dependently. EMPA did not impair performance of rats in the rotarod procedure. CONCLUSIONS AND IMPLICATIONS: EMPA is a high-affinity, reversible and selective OX(2) receptor antagonist, active in vivo, which should prove useful for analysis of OX(2) receptor function.

EMPA is a high-affinity, reversible and selective orexin OX2 receptor antagonist. [3H]EMPA binds to human and rat OX2-HEK293 membranes with KD values of 1.1 and 1.4 nM respectively.

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