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Systematic (IUPAC) name
CAS number 210421-64-0
ATC code C02KX03
PubChem 216235
Chemical data
Formula C18H15ClN2O6S2 
Mol. mass 454.906 g/mol
SMILES search in eMolecules, PubChem
Pharmacokinetic data
Bioavailability 70 to 100%
Protein binding >99%
Metabolism Hepatic (CYP2C9- and CYP3A4-mediated)
Half life 10 hours
Excretion Renal (50 to 60%)
Fecal (40 to 50%)
Therapeutic considerations
Licence data


Pregnancy cat.


Legal status
Routes Oral

Sitaxsentan or sitaxsentan sodium (actual INN: sitaxentan) (marketed as Thelin® by Encysive Pharmaceuticals) is a small molecule sodium salt that blocks the action of endothelin (ET) on the endothelin-A (ETA) receptor selectively (by a factor of 6000 compared to the ETB). It is a sulfonamide class endothelin receptor antagonist (ERA) and is undergoing Food and Drug Administration (FDA) review for treating pulmonary hypertension. The rationale for benefit compared to bosentan, a nonselective ET blocker, is negligible inhibition of the beneficial effects of ETB stimulation, such as nitric oxide production and clearance of ET from circulation. However, in clinical trials, the efficacy of sitaxsentan has been much the same as bosentan, but the liver toxicity has been better. Therefore sitaxsentan is expected to be marketed as a safer drug than bosentan, but not necessarily more effective.

Regulatory status

Thelin has been approved for marketing in both the European Union (on 10 August, 2006), in Canada[1] and in Australia (on 7 March, 2007). By December 2007 it had been launched commercially in Germany, The Netherlands, the United Kingdom, Ireland, France, Spain and Italy.

On the Prescription Drug User Fee Act (PDUFA) target action date of 24 March 2006 the United States' FDA recommended an approvable status to Thelin® but said it would not yet approve the product. On July 24, 2006 Thelin received a second approvable letter stating that efficacy outcome issues raised in the context of the STRIDE-2 study were still unresolved. In July 2007, Encysive commenced a formal dispute resolution process in a preliminary meeting with the FDA. However, in September 2007 the company announced that it was making preparations for another phase III clinical trial (STRIDE-5) to overcome the FDA's deficiency claims concerning the New Drug Application, and that it would not pursue the dispute resolution process [2].

Adverse effects

Adverse effects observed with Thelin® are class effects of endothelin receptor antagonists, and include :

Because Thelin® inhibits metabolism of warfarin, a decreased dose of warfarin is needed when co-administered with thelin. This is because warfarin acts to prevent blood from clotting, and if it remains unmetabolized, it can continue to thin the blood.


  1. ^ UPDATE 1-Encysive gets Canadian approval for hypertension drug. Reuters (May 30, 2007). Retrieved on 2007-07-08.
  2. ^ Encysive Pharmaceuticals to Conduct Phase III Study With Thelin (Sitaxsentan Sodium) in Pulmonary Arterial Hypertension. PrimeNewswire via COMTEX News Network (September 29, 2007). Retrieved on 2007-12-12.
  • Girgis RE, Frost AE, Hill NS, Horn EM, Langleben D, Mc Laughlin VV, Oudiz RJ, Robbins IM, Seibold JR, Shapiro S, Tapson VF, Barst RJ. 'Selective endothelinA receptor antagonism with sitaxsentan for pulmonary arterial hypertension associated with connective tissue disease' ARD 2007 [0: ard.2007.069609v2]
  • ATS 2005. The International Conference of the American Thoracic Society. 20 May - 25 May 2005. San Diego, CA.
  • American Heart Association. Primary or Unexplained Pulmonary Hypertension
  • Barst RJ, Langleben D, Frost A et al. Sitaxsentan therapy for pulmonary arterial hypertension. American Journal of Respiratory Critical Care Medicine 2004 15 February 2004 ;169(4):441-7. Electronic publication 20 November 2003.
  • Robyn J. Barst, MD; Stuart Rich, MD, FCCP; Allison Widlitz, MS, PA; Evelyn M. Horn, MD; Vallerie McLaughlin, MD and Joyce McFarlin, RN : Clinical Efficacy of Sitaxsentan, an Endothelin-A Receptor Antagonist, in Patients With Pulmonary Arterial Hypertension Chest. 2002;121:1860-1868.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Sitaxsentan". A list of authors is available in Wikipedia.
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