sitaxsentan

sitaxsentan (IPI 1040; Sitax; Sitaxentan; TBC 11251) is a selective endothelin A (ETA) receptor antagonist. Antihypertensive. Sitaxsentan(IPI 1040; Sitax; Sitaxentan; TBC 11251) is Used in treatment of chronic heart failure.

Safety and efficacy of sitaxsentan 50 and 100 mg in patients with pulmonary arterial hypertension.[Pubmed:22079088]

Pulm Pharmacol Ther. 2012 Feb;25(1):33-9.

OBJECTIVE: To assess safety and efficacy of sitaxsentan 50 and 100 mg in patients with pulmonary arterial hypertension (PAH). BACKGROUND: sitaxsentan is a highly selective endothelin-A receptor antagonist that was recently withdrawn by the manufacturer because of a pattern of idiosyncratic liver injury. METHODS: Before sitaxsentan withdrawal, this 18-week double-blind, placebo-controlled study randomized patients with PAH to receive placebo or sitaxsentan 50 or 100 mg once daily. The primary efficacy endpoint was change from baseline in 6-min walk distance (6MWD) at week 18. Changes in World Health Organization (WHO) functional class and time to clinical worsening (TTCW) were secondary endpoints. The primary efficacy analysis was powered for sitaxsentan 100 mg versus placebo. RESULTS: Of 98 randomized patients, 61% were WHO functional class II at baseline. Improvement from baseline to week 18 in 6MWD occurred with sitaxsentan 100 but not 50 mg; a strong placebo effect was observed. At week 18, WHO functional class was improved or maintained in more patients receiving sitaxsentan 100 mg than placebo (P = 0.038); 0% versus 12% of patients deteriorated, respectively. TTCW was not significantly different for 100-mg sitaxsentan patients than placebo (P = 0.090). Adverse events (AEs) occurring more frequently with sitaxsentan (50 or 100 mg) included headache, peripheral edema, dizziness, nausea, extremity pain, and fatigue; most AEs were of mild or moderate severity. CONCLUSION: sitaxsentan 100 mg improved functional class but not 6MWD in PAH patients who were mostly WHO functional class II at baseline. No patient receiving sitaxsentan 100 mg experienced clinical worsening; sitaxsentan was well tolerated.

Randomized, double-blind, placebo-controlled study of sitaxsentan to improve impaired exercise tolerance in patients with heart failure and a preserved ejection fraction.[Pubmed:24720918]

JACC Heart Fail. 2014 Apr;2(2):123-30.

OBJECTIVES: The purpose of this study was to evaluate the efficacy and safety of the selective endothelin type A (ETA) receptor antagonist sitaxsentan in patients who have heart failure with preserved ejection fraction (HFpEF). BACKGROUND: Fifty percent of heart failure (HF) patients have a preserved ejection fraction. No treatment has been shown to improve their clinical outcomes. Previous studies have suggested that ETA receptor antagonists might improve diastolic function and exercise tolerance in some forms of HF. METHODS: In all, 192 HFpEF patients (EF >/=50%) were randomly assigned 2:1 to sitaxsentan 100 mg/day (n = 128) versus placebo (n = 64) for 24 weeks. The primary endpoint was change in treadmill exercise time after 24 weeks of treatment. Secondary objectives included changes in left ventricular mass, transmitral inflow velocity to early diastolic mitral annulus velocity ratio, and Minnesota Living With Heart Failure questionnaire, and New York Heart Association functional class. Subjects were age 65 +/- 11 years, 63% female, 29% non-Caucasian, and in functional class II (56.5%) or III (43.5%). RESULTS: Subjects treated with sitaxsentan had an increase in median treadmill time (90 s) compared with placebo-treated subjects (37 s, p = 0.0302). There was no significant treatment differences in transmitral inflow velocity to early diastolic mitral annulus velocity ratio, left ventricular mass, Minnesota Living With Heart Failure questionnaire, New York Heart Association functional class, deaths, or HF hospital stay. The incidence of adverse events was similar for sitaxsentan and placebo. CONCLUSIONS: In HFpEF patients, treatment with a selective ETA receptor antagonist increased exercise tolerance but did not improve any of the secondary endpoints such as left ventricular mass or diastolic function. Further studies will be necessary to determine whether ETA receptor antagonists may be useful in the treatment of HFpEF. (A Study of the Effectiveness of sitaxsentan Sodium in Patients With Diastolic Heart Failure; NCT00303498).

Sitaxsentan-induced acute severe hepatitis treated with glucocorticoid therapy.[Pubmed:22332138]

Can Respir J. 2012 Jan-Feb;19(1):e1-2.

Endothelin receptor antagonists are commonly used in the treatment of pulmonary hypertension. sitaxsentan, a selective endothelin A receptor blocker, induces a mild transaminitis in approximately 3% to 5% of patients, but rarely an acute severe hepatitis. A case involving a 61-year-old female with sitaxsentan-induced acute severe liver failure is presented. Depite withdrawal of therapy, her liver tests failed to improve. After six weeks of monitoring, the patient was administered high-dose corticosteroids, with a good clinical and biochemical response. While endothelin receptor antagonists are postulated to cause hepatitis by inhibition of a bile salt transporter pump, an immune-mediated or idiosyncratic mechanism should be considered.

Evaluation of the endothelin receptor antagonists ambrisentan, bosentan, macitentan, and sitaxsentan as hepatobiliary transporter inhibitors and substrates in sandwich-cultured human hepatocytes.[Pubmed:24498134]

PLoS One. 2014 Jan 30;9(1):e87548.

BACKGROUND: Inhibition of the transporter-mediated hepatobiliary elimination of bile salts is a putative mechanism for liver toxicity observed with some endothelin receptor antagonists (ERAs). METHODS: Sandwich-cultured human hepatocytes were used to study the hepatobiliary distribution and accumulation of exogenous taurocholate, ERAs and endogenous bile acids. The molecular mechanisms for findings in hepatocytes or clinical observations were further explored using either vesicular assays (efflux transporters) or transfected cell-lines (uptake transporters). Inhibition constants (IC50) were measured for the human hepatobiliary transporters bile salt export pump (BSEP), sodium taurocholate cotransporting polypeptide (NTCP), multidrug resistance protein 2 (MRP2), P-glycoprotein (Pgp), breast cancer resistance protein (BCRP), organic anion-transporting polypeptide 1B1 (OATP1B1) and OATP1B3. RESULTS: The ERAs showed dose-dependent reductions in exogenous taurocholate cellular accumulation in human hepatocytes, with macitentan having the greatest effect. Consistent with their effects on bile acids, the ERAs inhibited bile transporters. IC50 values for OATP1B1 and OATP1B3 ranged from 2 microM for macitentan to 47 microM for ambrisentan. Macitentan and bosentan also inhibited NTCP with IC50 values of 10 and 36 microM, respectively. Similar to previously reported findings with sitaxsentan, BSEP inhibition was observed for bosentan and macitentan with IC50 values of 42 and 12 microM, respectively. In contrast, ambrisentan showed little or no inhibition of these transporters. Other transporters tested were weakly inhibited by the ERAs. Accumulation in hepatocytes was also a factor in the effects on bile transport. Macitentan demonstrated the greatest accumulation in human hepatocytes ( approximately 100x) followed by sitaxsentan ( approximately 40x), bosentan ( approximately 20x) and ambrisentan ( approximately 2x). CONCLUSIONS: Significant differences in the inhibition of hepatic transporters were observed between the evaluated ERAs in vitro. Macitentan had the highest level of cellular accumulation and caused the greatest effects on bile acid distribution in human hepatocytes followed by sitaxsentan and bosentan. Ambrisentan showed a low potential to affect bile acids.