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CARDIOVASCULAR

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

Discovery Research Laboratories (Kei.K., A.H., T.A., T.H., T.Y., Ken.K.) and Clinical Development Department (K.O.), Nippon Shinyaku Co., Ltd., Kyoto, Japan

Prostacyclin (PGI₂) 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}acetic acid (MRE-269). NS-304 is an orally available and potent agonist for the PGI₂ 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 >2.6 µM. 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.

Address correspondence to: Dr. Keiichi Kuwano, Discovery Research Laboratories, Nippon Shinyaku Co., Ltd., 14 Nishinosho-Monguchi-Cho, Kisshoin, Minami-Ku, Kyoto 601-8550, Japan. E-mail: k.kuwano{at}po.nippon-shinyaku.co.jp

This article has been cited by other articles:

				K. Kuwano, A. Hashino, K. Noda, K. Kosugi, and K. Kuwabara A Long-Acting and Highly Selective Prostacyclin Receptor Agonist Prodrug, 2-{4-[(5,6-Diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}-N-(methylsulfonyl)acetamide (NS-304), Ameliorates Rat Pulmonary Hypertension with Unique Relaxant Responses of Its Active Form, {4-[(5,6-Diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}acetic Acid (MRE-269), on Rat Pulmonary Artery J. Pharmacol. Exp. Ther., September 1, 2008; 326(3): 691 - 699. [Abstract] [Full Text] [PDF]