IP Receptor (Ki = 260 nM)

The long-acting oral prodrug selexipag (NS-304) is an IP receptor agonist whose active form, MRE-269, is very selective for IP receptors. [3H]Iloprost binding to human and rat IP receptors is inhibited by selexipag (NS-304) in a concentration-dependent manner. The rat IP receptor has a Ki of 2100 nM and the human IP receptor has a Ki of 260 nM. With an EC50 of 177nM, intracellular cAMP levels in hIP-CHO cells rose in a concentration-dependent manner upon treatment with selenium (NS-304). With IC50 values of 5.5 and 3.4 μM, respectively, selexipag (NS-304) similarly prevents platelet aggregation in humans and monkeys, but not in dogs (IC50 > 100 μM) [1].

After NS-304 was given orally to rats, the Cmax of MRE-269 (active form of Selelexipag/NS-304) was 1.1 μg/mL and in dogs, it was 9.0 μg/mL. In anesthetized rats, selexipag (NS-304) administered intradually at doses of 1 or 3 mg/kg enhances FSBF during a 4-hour period. Specifically, Selelexipag (NS-304) at 3 mg/kg increased FSBF over time, reaching a maximal rise of 93% in FSBF within an hour of dosing [1].

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The plasma concentrations of MRE-269 (active form of Selelexipag/NS-304) 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.[1]

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In a Sugen 5416/hypoxia rat model of PAH, selexipag significantly improved pulmonary artery obstruction, decreased right ventricular systolic pressure, decreased right ventricular hypertrophy and improved survival rate.[3]

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 (Ki) of MRE-269 for the human IP receptor was 20 nM; in contrast, the Ki values for other prostanoid receptors were >2.6 μM. MRE-269 was therefore a highly selective agonist for the IP receptor[1].

CHO cells expressing the human IP receptor (hIP-CHO cells) are seeded at 1×105 cells/well in a 24-well plate and cultured for 48 h. The cells are washed with Dulbecco's phosphate-buffered saline without divalent cations, preincubated in the medium for 1 h at 37°C, and then incubated for 15 min at 37°C with medium containing each drug in the presence of 500 μM 3-isobutyl-1-methylxanthine. The medium is removed, and perchloric acid solution is added to terminate the reaction. Intracellular cAMP levels are measured by enzymelinked immunosorbent assay[1].

Pregnant Sprague-Dawley rats received either 100 mg nitrofen dissolved in 1 ml olive oil or just olive oil by gavage on gestational age day (E) 9.5. Administration of nitrofen at exactly this time point induces mainly left-sided CDH in ~70% of the offspring, whereas all pups have PH. This study included only pups with an observable diaphragmatic defect. Pregnant rats were divided into eight groups: control, nitrofen (CDH), control + sildenafil, nitrofen + sildenafil (CDH+sildenafil), control + NS-304 , nitrofen + NS-304 (CDH+NS-304), control + sildenafil/NS-304, and nitrofen + sildenafil/NS-304 (CDH+sildenafil/NS-304). Sildenafil (100 mg·kg−1·day−1) and NS-304 (1 mg·kg−1·day−1) were dissolved in 0.8% ethanol in water and administered via oral gavage for 4 consecutive days from E17.5 to E20.5. At E21 pups were delivered by caesarean section and euthanized by lethal injection of pentobarbital (Fig. 1). The dosage of sildenafil was based on our previous study, whereas for NS-304 a dose study was performed.[2]

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Male Sprague-Dawley rats, cynomolgus monkeys, and male beagle dogs are used. Selexipag (NS-304) is orally administered to rats at 10 mg/kg and to dogs at 3 mg/kg, and blood samples are collected at various times and centrifuged to obtain plasma. The plasma concentrations of Selexipag (NS-304) and MRE-269 after oral administration of Selexipag (NS-304) to each animal are determined by high performance liquid chromatography coupled to mass spectrometry (LC/MS), and their pharmacokinetic parameters are calculated.Rats are orally administered Selexipag (NS-304) at 3 mg/kg twice daily for 1, 2, 3, or 4 weeks as a pretreatment. On the day after the final administration in the pretreatment, rats are anesthetized with urethane, and the FSBF is measured with a laser Doppler flowmeter after intraduodenal administration of Selexipag (NS-304) at 3 mg/kg[1].

Absorption, Distribution and Excretion
After oral administration, maximum concentrations of selexipag and its metabolite were observed to be reached at 1-3 and 3-4 hours, respectively. Absorption was impaired in the presence of food, resulting in delayed time to maximum concentration as well as ~30% lower peak plasma concentration. However, exposure was not found to be significantly affected by food.
93% in feces, 12% in urine.
On average, 35 L/hour.

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Metabolism / Metabolites
Selexipag yields its active metabolite by hydrolysis of the acylsulfonamide by the enzyme hepatic carboxylesterase 1. Oxidative metabolism catalyzed by CYP3A4 and CYP2C8 results in hydroxylated and dealkylated products. UGT1A3 and UGT2B7 are involved in the glucuronidation of the active metabolite. Other than active metabolite, other metabolites in circulation do not exceed 3% of the total drug-related material.

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Biological Half-Life
Selexipag's terminal half life is 0.8-2.5 hours. The active metabolite's terminal half life is 6.2-13.5 hours.

Hepatotoxicity
Selexipag is associated with a low rate of serum aminotransferase elevations (0% to 3%) that in clinical trials was similar to the rate among placebo recipients. These elevations were usually mild (rarely above 3 times ULN), transient and not associated with symptoms. There were no cases of serum enzyme elevations with jaundice in these preregistration clinical trials. Since licensure and more wide scale use, there have been no published reports of clinically apparent liver injury with jaundice associated with selexipag, but it has had limited general use.
Likelihood score: E (unlikely cause of clinically apparent liver injury).

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Protein Binding
Both selexipag and its active metabolite are highly protein bound, approximately 99%.

[1]. 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. J Pharmacol Exp Ther. 2007 Sep;322(3):1181-8.

[2]. Treatment of rat congenital diaphragmatic hernia with sildenafil and NS-304, selexipag's active compound, at the pseudoglandular stage improves lung vasculature. Am J Physiol Lung Cell Mol Physiol. 2018 May 10.

Selexipag is a member of the class of pyrazines that is N-(methanesulfonyl)-2-{4-[(propan-2-yl)(pyrazin-2-yl)amino]butoxy}acetamide carrying two additional phenyl substituents at positions 5 and 6 on the pyrazine ring. An orphan drug used for the treatment of pulmonary arterial hypertension. It is a prodrug for ACT-333679 (the free carboxylic acid). It has a role as an orphan drug, a prostacyclin receptor agonist, a platelet aggregation inhibitor, a vasodilator agent and a prodrug. It is a monocarboxylic acid amide, an ether, a member of pyrazines, an aromatic amine, a tertiary amino compound and a N-sulfonylcarboxamide. It is functionally related to an ACT-333679.
Selexipag was approved by the United States FDA on December 22, 2015 for the treatment of pulmonary arterial hypertension (PAH) to delay disease progression and reduce risk of hospitalization. PAH is a relatively rare disease with usually a poor prognosis requiring more treatment options to prolong long-term outcomes. Marketed by Actelion Pharmaceuticals under brand name Uptravi, selexipag and its active metabolite, ACT-333679 (MRE-269), act as agonists of the prostacyclin receptor to increase vasodilation in the pulmonary circulation and decrease elevated pressure in the blood vessels supplying blood to the lungs.
Selexipag is a Prostacyclin Receptor Agonist. The mechanism of action of selexipag is as a Prostacyclin Receptor Agonist.
Selexipag is prostacyclin receptor agonist that causes vasodilation in pulmonary vasculature and is used in the therapy of pulmonary arterial hypertension (PAH). Selexipag has been associated with a low rate of serum enzyme elevations during therapy, but has yet to be implicated in cases of clinically apparent acute liver injury.

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Drug Indication
Selexipag is indicated for the treatment of pulmonary arterial hypertension (PAH) to delay disease progression and reduce risk of hospitalization.
FDA Label
Uptravi is indicated for the long-term treatment of pulmonary arterial hypertension (PAH) in adult patients with WHO functional class (FC) II–III, either as combination therapy in patients insufficiently controlled with an endothelin receptor antagonist (ERA) and/or a phosphodiesterase type 5 (PDE-5) inhibitor, or as monotherapy in patients who are not candidates for these therapies. , , Efficacy has been shown in a PAH population including idiopathic and heritable PAH, PAH associated with connective tissue disorders, and PAH associated with corrected simple congenital heart disease. ,
Treatment of pulmonary arterial hypertension

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Mechanism of Action
Selexipag is a selective prostacyclin (IP, also called PGI2) receptor agonist. The key features of pulmonary arterial hypertension include a decrease in prostacyclin and prostacyclin synthase (enzyme that helps produce prostacyclin) in the lung. Prostacyclin is a potent vasodilator with anti-proliferative, anti-inflammatory, and anti-thrombotic effects; therefore, there is strong rationale for treatment with IP receptor agonists. Selexipag is chemically distinct as it is not PGI2 or a PGI2 analogue and has high selectivity for the IP receptor. It is metabolized by carboxylesterase 1 to yield an active metabolite (ACT-333679) that is approximately 37 times more potent than selexipag. Both selexipag and its metabolite are selective for the IP receptor over other prostanoid receptors.

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Pharmacodynamics
At the maximum tolerated dose of 1600 mcg twice per day, selexipag was not found to prolong the QT interval to a clinically relevant extent. Both selexipag and its metabolite caused concentration-dependent inhibition of platelet aggregation in vitro with IC50 of 5.5 µM and 0.21 µM, respectively. However, at clinically relevant concentrations, there was no effect on platelet aggregation test parameters following multiple dose administration of selexipag in healthy patients.

C26H32N4O4S

496.62

496.214

C, 62.88; H, 6.50; N, 11.28; O, 12.89; S, 6.46

475086-01-2

Selexipag-d7;1265295-21-3;Selexipag-d6;1265295-92-8

9913767

Typically exists as White to yellow solids at room temperature

1.2±0.1 g/cm3

1.579

4.56

1

7

12

35

730

0

S(C([H])([H])[H])(N([H])C(C([H])([H])OC([H])([H])C([H])([H])C([H])([H])C([H])([H])N(C1=C([H])N=C(C2C([H])=C([H])C([H])=C([H])C=2[H])C(C2C([H])=C([H])C([H])=C([H])C=2[H])=N1)C([H])(C([H])([H])[H])C([H])([H])[H])=O)(=O)=O

QXWZQTURMXZVHJ-UHFFFAOYSA-N

InChI=1S/C26H32N4O4S/c1-20(2)30(16-10-11-17-34-19-24(31)29-35(3,32)33)23-18-27-25(21-12-6-4-7-13-21)26(28-23)22-14-8-5-9-15-22/h4-9,12-15,18,20H,10-11,16-17,19H2,1-3H3,(H,29,31)

2-[4-[(5,6-diphenylpyrazin-2-yl)-propan-2-ylamino]butoxy]-N-methylsulfonylacetamide

NS 304; ACT293987; NS-304; ACT 293987; NS304; Uptravi; ACT-293987; Selexipag; 475086-01-2; NS-304; Uptravi; ACT-293987; NS 304; ACT 293987; 2-(4-((5,6-diphenylpyrazin-2-yl)(isopropyl)amino)butoxy)-N-(methylsulfonyl)acetamide;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ≥ 50 mg/mL (~100.68 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (5.03 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: 2.5 mg/mL (5.03 mM) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (5.03 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)