2-{4-[(5,6-Diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}-N-(methylsulfonyl)acetamide (NS-304), an Orally Available and Long-Acting Prostacyclin Receptor Agonist Prodrug

Abstract

Prostacyclin (PGI 2 ) and its analogs are useful for the treatment of various vascular disorders, but their half-lives are too short for widespread clinical application. To overcome this drawback, we have synthesized a novel diphenylpyrazine derivative, 2-{4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}-N-(methylsulfonyl)acetamide (NS-304), a prodrug of the active form {4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}ac-etic acid (MRE-269). NS-304 is an orally available and potent agonist for the PGI 2 receptor (IP receptor). The inhibition constant (K i ) of MRE-269 for the human IP receptor was 20 nM; in contrast, the K i values for other prostanoid receptors were Ͼ2.6 M. MRE-269 was therefore a highly selective agonist for the IP receptor. The plasma concentrations of MRE-269 remained near peak levels for more than 8 h after oral administration of NS-304 to rats and dogs, and NS-304 increased femoral skin blood flow in rats in a long-lasting manner without affecting the hemodynamics. These findings indicate that NS-304 acts as a long-acting IP receptor agonist in vivo. The continuous vasodilation evoked by NS-304 was not attenuated by repeated treatment, indicating that NS-304 is unlikely to cause severe desensitization of the IP receptor in rats. Moreover, a microdose pharmacokinetic study in which NS-304 was orally administered to healthy male volunteers showed conversion of NS-304 to MRE-269 and a long plasma elimination half-life for MRE-269 (7.9 h). In conclusion, NS-304 is an orally available and long-acting IP receptor agonist prodrug, and its active form, MRE-269, is highly selective for the IP receptor. Therefore, NS-304 is a promising drug candidate for various vascular diseases, especially pulmonary arterial hypertension and arteriosclerosis obliterans.Five prostanoids, prostaglandin (PG) D 2 , PGE 2 , PGF 2␣ , prostacyclin (PGI 2 ), and thromboxane A 2 (TXA 2 ), are cyclooxygenase metabolites of arachidonic acid. These lipid mediators interact with specific G protein-coupled receptors (DP, EP 1 , EP 2 , EP 3 , EP 4 , FP, IP, and TP) and activate the corresponding intracellular signaling cascade (Narumiya et al., 1999;Breyer et al., 2001). PGI 2 , which is mainly produced in vascular endothelial cells (Moncada et al., 1976;Moncada and Vane, 1978), acts via the PGI 2 receptor (IP receptor) as a potent vasodilator and inhibitor of platelet aggregation (Namba et al., 1994), and it counteracts the actions of TXA 2 , a potent vasoconstrictor and initiator of platelet aggregation. Activation of the IP receptor leads to stimulation of adenylate cyclase through coupling to G s protein, with a resulting increase in intracellular cAMP levels (Adie et al., 1992), and to activation of phospholipase C through coupling to G q protein leading to elevation of cytosolic Ca 2ϩ concentrations (Vassaux et al., 1992).The expression of IP receptor mRNA has been observed in various organs, including the heart, lung, thymus, spleen, and kidney (Oida et al., 1995

Prostaglandin I2 Receptor Agonism Preserves β-Cell Function and Attenuates Albuminuria Through Nephrin-Dependent Mechanisms

“…It plays an important role in the regulation of renal hemodynamics, tubule transport, and renin secretion (47), whereas PGI 2 analog therapy may reduce renal fibrosis and inflammation (48). Selexipag treatment improved endothelial dysfunction in a rat model of pulmonary hypertension (14), and endothelial dysfunction is a common occurrence in people with diabetic kidney disease (49). These alternative actions represent possible additional advantages of IP receptor-directed therapies for diabetic kidney disease, and they cannot be excluded as contributing to the anti-albuminuric effect of selexipag observed in the current study.…”

“…The effects of selexipag (14,15) on pancreatic b-cell function were assessed in nondiabetic and streptozotocin (STZ)-induced diabetic male C57BL/6 mice (The Jackson Laboratory, Bar Harbor, ME) aged 8 weeks (n = 8-10 per group). Diabetes was induced by administering a daily intraperitoneal injection of STZ (55 mg/kg) in 0.1 mol/L citrate buffer (pH 4.5) (or citrate buffer control) after a 4-h fast for 5 consecutive days.…”

“…MIN6 C3 cells were provided by Dr. Philippe Halban (University of Geneva, Switzerland) with permission from Dr. Jun-ichi Miyazaki, University of Osaka, who produced the maternal MIN6 cell line (19). Cells were treated with MRE-269 (Cayman Chemical, Ann Arbor, MI) in 0.1% DMSO at a concentration of 10 mmol/L (14,20), with or without preincubation for 30 min with the PKA inhibitor H89 (10 mmol/L) (Sigma-Aldrich, Oakville, Ontario, Canada) (21), or with the IP receptor inhibitor RO1138452 10 mmol/L (Cayman Chemical), 100 nmol/L insulin (Eli Lilly, Toronto, Ontario, Canada), or 10 mmol/L forskolin (Tocris Bioscience, Bristol, U.K.) for 1 h. IP receptor expression was determined in MIN6 B1 cells, human podocytes, and conditionally immortalized mouse podocytes (22).…”

“…Diabetes was induced by administering a daily intraperitoneal injection of STZ (55 mg/kg) in 0.1 mol/L citrate buffer (pH 4.5) (or citrate buffer control) after a 4-h fast for 5 consecutive days. Mice were randomized to receive the IP receptor prodrug selexipag (3 mg/kg in 0.9% saline containing 12% DMSO by twice daily gavage; Cayman Chemical) (14) or vehicle beginning with the first intraperitoneal injection of STZ. After 2 weeks, fasting blood glucose levels (OneTouch UltraMini; LifeScan Canada Ltd., Burnaby, British Columbia, Canada) were determined, and GSIS was determined by administering an intraperitoneal glucose load (3 g/kg) after a 15-h fast, with blood collected from the saphenous vein 30 min after the injection (23).…”

Stimulation of fat storage by prostacyclin and selective agonists of prostanoid IP receptor during the maturation phase of cultured adipocytes

“…We then investigated effects of selective agonists for the IP receptor or PPARc on the storage of fats attenuated by the addition of aspirin. The supplementation with selective agonists for the IP receptor including carbaprostacyclin (Whittle et al 1980), MRE-269 (Kuwano et al 2007), and treprostinil (Olschewski et al 2004) at different concentrations of 0.1 and 0.5 lM were found to be effective in appreciably stimulating adipogenesis in cultured adipocytes during the maturation phase as can be seen with 0.1 and 1 lM troglitazone (Willson et al 2000), an activator of PPARc (Fig. 2a).…”