Development and Characterization of Treprostinil Palmitil Inhalation Aerosol for the Investigational Treatment of Pulmonary Arterial Hypertension.

Treprostinil palmitil (TP) is a prodrug of treprostinil (TRE), a pulmonary vasodilator that has been previously formulated for inhaled administration via a nebulizer. TP demonstrates a sustained presence in the lungs with reduced systemic exposure and prolonged inhibition of hypoxia-induced pulmonary vasoconstriction in vivo. Here, we report on re-formulation efforts to develop a more convenient solution-based metered-dose inhaler (MDI) formulation of TP, a treprostinil palmitil inhalation aerosol (TPIA) that matches the pharmacokinetic (PK) and efficacy profile of a nebulized TP formulation, treprostinil palmitil inhalation suspension (TPIS). MDI canisters were manufactured using a two-stage filling method. Aerosol performance, formulation solubility, and chemical stability assays were utilized for in vitro evaluation. For in vivo studies, TPIA formulations were delivered to rodents using an inhalation tower modified for MDI delivery. Using an iterative process involving evaluation of formulation performance in vitro (TP and excipient solubility, chemical stability, physical stability, and aerosol properties) and confirmatory testing in vivo (rat PK and efficacy, guinea pig cough), a promising formulation was identified. The optimized formulation, TPIA-W, demonstrates uniform in vitro drug delivery, a PK profile suitable for a once-daily administration, efficacy lasting at least 12 h in a hypoxic challenge model, and a significantly higher cough threshold than the parent drug treprostinil.

Novel Toxicology Program to Support the Development of Inhaled VentaProst.

Currently, off-label continuous administration of inhaled epoprostenol is used to manage hemodynamics during mitral valve surgery. A toxicology program was developed to support the use of inhaled epoprostenol during mechanical ventilation as well as pre- and postsurgery via nasal prongs. To support use in patients using nasal prongs, a Good Laboratory Practice (GLP), 14-day rat, nose-only inhalation study was performed. No adverse findings were observed at ∼50× the dose rate received by patient during off-label use. To simulate up to 48 hours continuous aerosol exposure during mechanical ventilation, a GLP toxicology study was performed using anesthetized, intubated, mechanically ventilated dogs. Dogs inhaled epoprostenol at approximately 6× and 13× the dose rate reported in off-label human studies. This novel animal model required establishment of a dog intensive care unit providing sedation, multisystem support, partial parenteral nutrition, and management of the intubated mechanically ventilated dogs for the 48-hour duration of study. Aerosol was generated by a vibrating mesh nebulizer with novel methods required to determine dose and particle size in-vitro. Continuous pH 10.5 epoprostenol was anticipated to be associated with lung injury; however, no adverse findings were observed. As no toxicity at pH 10.5 was observed with a formulation that required refrigeration, a room temperature stable formulation at pH 12 was evaluated in the same ventilated dog model. Again, there were no adverse findings. In conclusion, current toxicology findings support the evaluation of inhaled epoprostenol at pH 12 in surgical patients with pulmonary hypertension for up to 48 hours continuous exposure.

Compatibility of treprostinil sodium and dopamine hydrochloride during simulated Y-site administration.

PURPOSE: To evaluate the physical and chemical compatibilities of treprostinil sodium and dopamine hydrochloride. METHODS: Treprostinil sodium (4,000, 76,000, and 500,000 ng/mL) were mixed with dopamine hydrochloride (0.6, 3.2, 6, and 40 mg/mL). Samples were obtained at hours 0, 1, 2, and 4 for physical compatibility and chemical stability testing. Physical compatibility was assessed by visual examination and measurements of turbidity and pH. Drug concentrations were assessed using stability-indicating liquid chromatography mass spectrophotometry (LCMS) for treprostinil sodium and stability-indicating high-performance liquid chromatography (HPLC) for dopamine hydrochloride. RESULTS: Treprostinil sodium 4,000 and 76,000 ng/mL, when mixed with dopamine hydrochloride 0.6, 3.2, 6, and 40 mg/mL, were stable for 4 hours. Treprostinil sodium 500,000 ng/mL was stable when mixed with dopamine hydrochloride 0.6 mg/mL for 4 hours, but when mixed with dopamine hydrochloride 3.2, 6, and 40 mg/mL, significant precipitation was seen. CONCLUSION: Treprostinil sodium 4,000 and 76,000 ng/mL were stable for 4 hours during simulated Y-site coadministration with dopamine hydrochloride 0.6, 3.2, 6, and 40 mg/mL. Treprostinil sodium 500,000 ng/mL is stable when mixed with dopamine hydrochloride 0.6 mg/mL.

Pharmacology of the single isomer, esuberaprost (beraprost-314d) on pulmonary vascular tone, IP receptors and human smooth muscle proliferation in pulmonary hypertension.

BACKGROUND AND PURPOSE: Beraprost is a prostacyclin analogue and IP receptor agonist which is approved to treat pulmonary arterial hypertension (PAH) in Asia. The beraprost-314d isomer (esuberaprost) is one of four stereoisomers contained within the racemic mixture of beraprost. The pharmacological profile of esuberaprost is now evaluated to determine how stereoisomer separation affects its potency and mode of action in functional assays. EXPERIMENTAL APPROACH: Vascular tone was assessed using wire myography in rat and human distal pulmonary arteries (PAs) pre-contracted with U46619 (100 nM). HEK-293 cells stably expressing the human IP receptor (HEK-293-IP) and pulmonary arterial smooth muscle cells (PASMCs) derived from PAH patients were used to assess cyclic AMP (cAMP) generation and cell proliferation, respectively. KEY RESULTS: Esuberaprost relaxed rat PAs with a 5-fold greater potency compared with beraprost, and effects were strongly inhibited by RO3244794 (IP receptor antagonist) or L-NAME (NO synthase inhibitor). Esuberaprost caused EP3 receptor-dependent vasoconstriction at high concentrations ≥ 1000 nM, but contractions were 50% lower compared to beraprost. In HEK-293-IP cells, esuberaprost was 26-fold more potent (EC50 0.4 nM) at increasing cAMP than beraprost. In human PASMCs, esuberaprost was 40-fold more potent than beraprost at inhibiting cell proliferation (EC50 3 nM versus 120 nM), contrasting the 5-fold potency difference for cAMP elevation. Antiproliferative effects of esuberaprost appeared more dependent on NO than on the IP receptor. In PAs from patients with pulmonary hypertension, esuberaprost, caused some relaxation whereas beraprost instead produced a weak contraction. CONCLUSIONS AND IMPLICATIONS: Stereoisomer separation of beraprost has a significant effect on the pharmacology of the individual isomer, esuberaprost, identified in vitro as a highly potent prostanoid IP receptor agonist.

Ligand binding to human prostaglandin E receptor EP4 at the lipid-bilayer interface.

Prostaglandin E receptor EP4, a G-protein-coupled receptor, is involved in disorders such as cancer and autoimmune disease. Here, we report the crystal structure of human EP4 in complex with its antagonist ONO-AE3-208 and an inhibitory antibody at 3.2 Å resolution. The structure reveals that the extracellular surface is occluded by the extracellular loops and that the antagonist lies at the interface with the lipid bilayer, proximal to the highly conserved Arg316 residue in the seventh transmembrane domain. Functional and docking studies demonstrate that the natural agonist PGE2 binds in a similar manner. This structural information also provides insight into the ligand entry pathway from the membrane bilayer to the EP4 binding pocket. Furthermore, the structure reveals that the antibody allosterically affects the ligand binding of EP4. These results should facilitate the design of new therapeutic drugs targeting both orthosteric and allosteric sites in this receptor family.

Study on bioequivalence of beraprost in healthy volunteers by liquid chromatography with tandem mass spectrometry.

Beraprost sodium is an oral prostacyclin analog that was first approved in 1992 (Japan) for the treatment of peripheral vascular disorders. It is administered orally as a tablet available in strength 20 µg. In this paper, we described a liquid chromatography tandem mass spectrometry method that was developed for the quantification of beraprost in human plasma with high sensitivity at picogram per milliliter concentration. The method had been validated in terms of selectivity, sensitivity, accuracy and precision, matrix effect, linearity, recovery and carry-over according to the Guideline on Bioanalytical Validation from the European Medicines Agency. The standard calibration curve for beraprost was 9.5-1419 pg/mL. This method has been applied successfully to a bioequivalence study with 60 µg of beraprost (three tablets) in 29 healthy volunteers. The results showed that the two formulations of beraprost are bioequivalent.

Synthetic approaches to isocarbacyclin and analogues as potential neuroprotective agents against ischemic stroke.

Isocarbacyclin is a valuable synthetic analogue of prostacyclin with potential neuroprotective effects for the treatment of ischemic stroke. Herein, we describe the synthesis of isocarbacyclin and bicyclic analogues in only 7-10 steps, with the ω-side chain diversified at a late stage. A combination of new reaction design, function-oriented synthesis, and late-stage diversification led to a series of compounds that were tested for their neuroprotective activities. Efforts toward the synthesis of tricyclic analogues of isocarbacyclin, using the same combination of metal-catalyzed reactions, is also described.

Investigation of safety and efficacy of the new more thermostable formulation of Flolan (epoprostenol) in Japanese patients with pulmonary arterial hypertension (PAH)-An open-label, single-arm study.

OBJECTIVE: This study was conducted to evaluate the safety and efficacy of a new more thermostable Flolan (epoprostenol) solution prepared with the reformulated pH 12.0 diluent in Japanese patients with pulmonary arterial hypertension (PAH) receiving higher doses of Flolan than those typically administered in Western countries. METHODS: This open-label, single-arm study was conducted in 10 Japanese PAH patients. During the run-in period, patients were intravenously infused with Flolan (45 ng/kg/min or higher doses) solution prepared with the existing pH 10.5 diluent. The patients were then switched to a new more thermostable Flolan solution prepared with the reformulated pH 12.0 diluent and observed for a 4-week treatment period. As a primary endpoint, safety after switching to the new Flolan solution was evaluated. Secondary endpoints included hemodynamics and the necessity for dose adjustment of Flolan in these patients. RESULTS: All 10 patients completed the study period. Observed adverse events were nausea and hepatic function abnormal in 1 patient each, and both events were mild. No patients required dose adjustment due to the change from baseline in mean pulmonary artery pressure (mPAP) measured 3 hrs after switching to Flolan solution prepared with the reformulated diluent. No major changes from baseline in mPAP, pulmonary vascular resistance, or right atrial pressure were observed at 24 hrs and at 4 weeks after switching to the Flolan solution prepared with pH 12.0 diluent. Although some patients showed increases in cardiac output (CO) from baseline at 24 hrs and 4 weeks, no patients required dose reduction as a result of an increase in CO. CONCLUSION: Neither safety/efficacy concerns nor any dose adjustments of Flolan after switching to a more thermostable Flolan solution prepared with the reformulated pH 12.0 diluent could be required in Japanese patients with PAH receiving higher doses of Flolan. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02705807.

Selective Prostacyclin Receptor Agonist Selexipag, in Contrast to Prostacyclin Analogs, Does Not Evoke Paradoxical Vasoconstriction of the Rat Femoral Artery.

Selexipag [2-{4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}-N-(methylsulfonyl)acetamide] is a selective nonprostanoid prostacyclin (PGI2) receptor (IP receptor) agonist that is approved for the treatment of pulmonary arterial hypertension (PAH). In contrast to selexipag, PGI2 analogs used in the clinic are nonselective agonists at prostanoid receptors and can also activate contractile prostaglandin E receptor 3 (EP3) receptors. Leg pain is a common side effect in patients receiving treatment with PGI2 analogs and peripheral vasoconstriction can be responsible for side effects related to muscular ischemia. This study tested the hypothesis that PGI2 analogs could cause paradoxical vasoconstriction of the femoral artery via EP3 receptor activation but that only vasorelaxation would be observed in response to selexipag and its active metabolite ACT-333679 [{4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}acetic acid]. Selexipag and ACT-333679 relaxed rings of the isolated rat femoral artery contracted with either prostaglandin F2α (PGF2α ) or the α1 adrenoceptor (α1AR) agonist phenylephrine. ACT-333679 also inhibited contraction of the femoral artery to sympathetic nerve stimulation. In contrast, PGI2 analogs (iloprost, beraprost, and treprostinil) caused additional contraction of arterial rings precontracted with phenylephrine, which was reverted to relaxation by antagonism of EP3 receptors. Treprostinil augmented contraction of the femoral artery to sympathetic nerve stimulation in an EP3 receptor-dependent manner. Mechanistically, concomitant EP3 and α1AR receptor activation synergistically constricted femoral arteries. It is concluded that selexipag and ACT-333679 are vasorelaxants of the rat femoral artery and, unlike PGI2 analogs, do not cause paradoxical vasoconstriction via activation of EP3 receptors. EP3 receptor-mediated vasoconstriction may contribute to the well documented peripheral muscle pain reported in patients with PAH receiving PGI2 analogs. Leg pain may be less in patients treated with selexipag.

Hydroboration-Oxidation of (±)-(1α,3α,3aß,6aß)-1,2,3,3a,4,6a-Hexahydro-1,3-pentalenedimethanol and Its O-Protected Derivatives: Synthesis of New Compounds Useful for Obtaining (iso)Carbacyclin Analogues and X-ray Analysis of the Products.

Hydroboration-oxidation of 2α,4α-dimethanol-1ß,5ß-bicyclo[3.3.0]oct-6-en dibenzoate (1) gave alcohols 2 (symmetric) and 3 (unsymmetric) in ~60% yield, together with the monobenzoate diol 4a (37%), resulting from the reduction of the closer benzoate by the intermediate alkylborane. The corresponding alkene and dialdehyde gave only the triols 8 and 9 in ~1:1 ratio. By increasing the reaction time and the temperature, the isomerization of alkylboranes favours the un-symmetrical triol 9. The PDC oxidation of the alcohols gave cleanly the corresponding ketones 5 and 6 and the deprotection of the benzoate groups gave the symmetrical ketone 14, and the cyclic hemiketal 15, all in high yields. The ethylene ketals of the symmetrical ketones 11 and 13 were also obtained. The compounds 5, 6, 11, 13, 14 could be used for synthesis of new (iso)carbacyclin analogues. The structure of the compounds was established by NMR spectroscopy and confirmed by X-ray crystallography.

Microbial challenge test of a novel epoprostenol sodium formulation.

AIM: The aim of the current study was to present a comprehensive display of antimicrobial activity of a novel epoprostenol sodium formulation with respect to seven different microorganisms, two levels of inoculation (102-103 colony forming units [CFU]/mL and 105-106 CFU/mL), two diluents (sterile water for injection [SWI] and sterile saline [sodium chloride 0.9%] for injection [SSI]), two concentrations (3,000 ng/mL and 15,000 ng/mL), and seven different storage time points at two temperatures (up to 10 days at 2°C-8°C and 20°C-25°C). MATERIALS AND METHODS: Antimicrobial activity was evaluated for, 1) solutions at 3,000 ng/mL inoculated with 102-103 CFU/mL and 105-106 CFU/mL; and 2) solutions at 15,000 ng/mL inoculated with 102-103 CFU/mL and 105-106 CFU/mL. All solutions were stored for up to 10 days at 2°C-8°C and 20°C-25°C. Solutions were prepared by reconstitution and further dilution of an epoprostenol sodium formulation using SWI or SSI. Antimicrobial activity was measured after inoculation with seven species of bacteria, yeast, and mold. RESULTS: For all solutions, after 10 days, no microbial growth with respect to initial inoculum was observed, with the exception of a few early time points when using SWI as diluent. Some microorganisms died off completely, whereas others remained stable overall or returned to initial levels. Prior to decreasing, some microorganisms displayed a slight initial increase, presumed to be caused by breakup of clusters. Storage temperature had a negligible influence on the results, whereas choice of diluent (SSI or SWI) impacted growth kinetics in that SSI had a greater antimicrobial effect than SWI. CONCLUSION: Upon reconstitution and further dilution of the novel epoprostenol formulation to concentrations of 3,000 ng/mL and 15,000 ng/mL with SWI or SSI, the resulting solutions did not support growth of the tested microorganisms when stored at 2°C-8°C or 20°C-25°C for up to 10 days.

A practical synthesis of chiral tricyclic cyclopenta[b]benzofuran, a key intermediate of Beraprost.

A novel formal synthesis of Beraprost (1) is described. The tricyclic cyclopent[b]benzofuran core is efficiently prepared from (-)-Corey lactone diol in 12 steps with an overall yield of 37.4%. Key features of the strategy include a ring-closing metathesis reaction and aromatization to form the tricyclic cyclopenta[b]benzofuran framework, and selective halogenation/formylation to install the butyrate side-chain.

In silico modelling of prostacyclin and other lipid mediators to nuclear receptors reveal novel thyroid hormone receptor antagonist properties.

Prostacyclin (PGI2) is a key mediator involved in cardiovascular homeostasis, acting predominantly on two receptor types; cell surface IP receptor and cytosolic peroxisome proliferator activated receptor (PPAR) ß/δ. Having a very short half-life, direct methods to determine its long term effects on cells is difficult, and little is known of its interactions with nuclear receptors. Here we used computational chemistry methods to investigate the potential for PGI2, beraprost (IP receptor agonist), and GW0742 (PPARß/δ agonist), to bind to nuclear receptors, confirmed with pharmacological methods. In silico screening predicted that PGI2, beraprost, and GW0742 have the potential to bind to different nuclear receptors, in particular thyroid hormone ß receptor (TRß) and thyroid hormone α receptor (TRα). Docking analysis predicts a binding profile to residues thought to have allosteric control on the TR ligand binding site. Luciferase reporter assays confirmed that beraprost and GW0742 display TRß and TRα antagonistic properties; beraprost IC50 6.3 × 10(-5)mol/L and GW0742 IC50 4.9 × 10(-6) mol/L. Changes to triiodothyronine (T3) induced vasodilation of rat mesenteric arteries measured on the wire myograph were measured in the presence of the TR antagonist MLS000389544 (10(-5) mol/L), beraprost (10(-5) mol/L) and GW0742 (10(-5) mol/L); all significantly inhibited T3 induced vasodilation compared to controls. We have shown that both beraprost and GW0742 exhibit TRß and TRα antagonist behaviour, and suggests that PGI2 has the ability to affect the long term function of cells through binding to and inactivating thyroid hormone receptors.

N2 extenuates experimental ischemic stroke through platelet aggregation inhibition.

INTRODUCTION: Thromboxane A2 (TXA2) can induce the platelet aggregation and lead to thrombosis. This will cause the low-reflow phenomenon after ischemic stroke and aggravate the damage of brain issues. Therefore, it is potential to develop the drugs inhibiting TXA2 pathway to treat cerebral ischemia. AIM: This study aims to prove the protective effect of N2 (4-(2-(1H-imidazol-1-yl) ethoxy)-3-methoxybenzoic acid) on focal cerebral ischemia and reperfusion injury through platelet aggregation inhibition. MATERIALS AND METHODS: Middle cerebral artery occlusion/reperfusion (MCAO/R) is used as the animal model. Neurological deficit score, Morris water maze, postural reflex test, Limb-use asymmetry test, infarct volume, and water content were performed to evaluate the protective effect of N2 in MCAO/R rats. 9, 11-dieoxy-11α, 9α-methanoepoxyprostaglandin F2α (U46619) or adenosine diphosphate (ADP) was used as the inducer of platelet aggregation. RESULTS AND CONCLUSIONS: N2 can improve the motor function, learning and memory ability in MCAO/R rats while reducing the infarct volume. N2 can inhibit TXA2 formation but promote PGI2, and can inhibit platelet aggregation induced by U46619 and ADP. Further, N2 inhibits thrombosis with a minor adverse effect of bleeding than Clopidogrel. In conclusion, N2 can produce the protective effect on MCAO/R brain injury through inhibiting TXA2 formation, platelet aggregation and thrombosis.

Prostanoids regulate angiogenesis acting primarily on IP and EP4 receptors.

Angiogenesis is regulated by numerous activators and inhibitors, including prostanoids. Although many studies have identified their roles in inflammation, regulatory functions of prostanoids in angiogenesis are poorly understood. Here, we compared the activation of angiogenesis in vitro by two prostanoids with important vascular roles: prostaglandin E2 (PGE2) - thought to be the most important prostanoid activator of angiogenesis - and prostaglandin I2 (prostacyclin or PGI2), whose receptors are predominantly expressed in endothelial cells. Both of these prostanoids activate G-protein coupled receptors: EP1, EP2, EP3 and EP4 by PGE2 and IP by prostacyclin. Human umbilical vein endothelial cells (HUVECs) were used to characterize two pivotal pro-angiogenic processes in vitro: cell migration (using the matrigel droplet assay developed in our laboratory) and "tube formation" (a widely accepted method of assessing formation of blood vessel precursors). The suppression of cell migration and tube formation by the IP-specific antagonist CAY10441 was more extensive (~80%) than by the EP4-specific antagonist L-161,982 (~20%). AH6809, an antagonist of EP1, EP2 and EP3 receptors did not significantly suppress angiogenesis. Expression of the pro-angiogenic receptors KDR and Tie-2 in HUVECs was preferentially suppressed by antagonism of IP and EP4 receptors, respectively. EP4 and IP receptor agonists elicited biphasic actions on angiogenic processes in which there was activation at low concentration, and rapid desensitization at high concentrations - a characteristic common to many G-protein coupled receptors. Together these findings suggest that the prostacyclin-IP pathway plays a major role in the regulation of pro-angiogenic processes in HUVECs.

Regio- and Stereocontrolled Dieckmann Approach to Treprostinil-Inspired, Polycyclic Scaffold For Building Macrocyclic Diversity.

We developed a regio- and stereocontrolled Dieckmann cyclization approach to the synthesis of a novel, natural-product-like scaffold that was inspired from treprostinil (UT-15). This was further utilized in a diversity-based, 15-membered macrocyclic synthesis of two different sets of hybrid compounds. The amino acid moiety embedded in the macrocyclic skeleton allow exploring various chiral side chain groups within the ring.

Encapsulation of beraprost sodium in nanoparticles: analysis of sustained release properties, targeting abilities and pharmacological activities in animal models of pulmonary arterial hypertension.

Prostaglandin I2 (PGI2) and its analogues (such as beraprost sodium, BPS) are beneficial for the treatment of pulmonary arterial hypertension (PAH). The encapsulation of BPS in nanoparticles to provide sustained release and targeting abilities would improve both the therapeutic effect of BPS on PAH and the quality of life of patients treated with this drug. BPS was encapsulated into nanoparticles prepared from a poly(lactic acid) homopolymer and monomethoxy poly(ethyleneglycol)-poly(lactide) block copolymer. The accumulation of nanoparticles in damaged pulmonary arteries was examined using fluorescence-emitting rhodamine S-encapsulated nanoparticles. The monocrotaline-induced PAH rat model and the hypoxia-induced mouse model were used to examine the pharmacological activity of BPS-encapsulated nanoparticles. A nanoparticle, named BPS-NP, was selected among various types of BPS-encapsulated nanoparticles tested; this was based on the sustained release profile in vitro and blood clearance profile in vivo. Fluorescence-emitting rhodamine S-encapsulated nanoparticles were prepared in a similar manner to that of BPS-NP, and showed accumulation and prolonged residence in monocrotaline-damaged pulmonary peripheral arteries. Intravenous administration of BPS-NP (once per week, 20µg/kg) protected against monocrotaline-induced pulmonary arterial remodeling and right ventricular hypertrophy. The extent of this protection was similar to that observed with oral administration (once per day, 100µg/kg) of BPS alone. The once per week intravenous administration of BPS-NP (20µg/kg) also exhibited an ameliorative effect on hypoxia-induced pulmonary arterial remodeling and right ventricular hypertrophy. The beneficial effects of BPS-NP on PAH animal models seem to be mediated by its sustained release and tissue targeting profiles. BPS-NP may be useful for the treatment of PAH patients due to reduced dosages and frequency of BPS administration.

Assessing the agonist profiles of the prostacyclin analogues treprostinil and naxaprostene, particularly their DP1 activity.

In this study, the inhibitory profiles of the prostacyclin analogues treprostinil and naxaprostene on several isolated smooth muscle preparations have been investigated. Treprostinil was an agonist for prostanoid DP1, EP2 and IP receptors, but not EP4 receptors; its DP1 potency was only 3-4 times less than PGD2 itself. Naxaprostene was much more selective for IP receptors and tended towards partial agonism. Treprostinil is a 13,14-dihydro analogue and the role of conformation around C12-15 in controlling agonist specificity is debated; the synthesis of new analogues is proposed and possible clinical usage discussed. In terms of selective prostanoid antagonists employed, BW-A868C/MK-0524 (DP1), ACA-23 (EP2) and GW-627368 (EP4) were found fit for purpose. However, the IP antagonist RO-1138452 was compromised by α1 and α2-adrenoceptor-mediated contractile activity on rat tail artery and anti-muscarinic activity on mouse trachea. There is a need for IP receptor antagonists with better selectivity and higher affinity.

A multinational phase IIb/III trial of beraprost sodium, an orally active prostacyclin analogue, in patients with primary glomerular disease or nephrosclerosis (CASSIOPEIR trial), rationale and study design.

BACKGROUND: Chronic kidney disease (CKD) is public health concern even in Asian countries. TRK-100STP, a sustained release tablet of an orally-active prostacyclin analogue, beraprost sodium, is suggested to suppress worsening of some parameters of renal filtration function, containing in slope of 1/serum creatinine (1/SCr) vs. time in a phase II clinical trial. METHODS/DESIGN: We describe the design of the phase IIb/III trial of TRK-100STP, CASSIOPEIR (CRF Asian Study with Oral PGI2 derivative for Evaluating Improvement of Renal function) conducted in approximately 160 centers in China, Hong Kong, Japan, Malaysia, Republic of Korea, Taiwan, and Thailand. A total of 750 patients (n = 250 per group) with primary glomerular disease or nephrosclerosis were planned to be enrolled. Patients were randomized into one of three treatment groups in a double-bind, placebo-controlled manner: TRK-100STP 60 µg b.i.d.; TRK-100STP 120 µg b.i.d.; or placebo. The treatment period is planned to last 2 to 4 years. The primary efficacy endpoint is the renal composite endpoint including doubling of SCr and ESRD (dialysis induction, renal transplantation, or increase in SCr to ≥ 6.0 mg/dL). DISCUSSION: This trial targeting CKD patients is designed to (a) demonstrate the superiority of TRK-100STP over placebo using renal composite endpoints, (b) determine the recommended clinical dose, and (c) assess the safety of TRK-100STP in this population and setting. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01090037.