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A Pharmacokinetic Drug-Drug Interaction (DDI) Study Between Sitaxsentan And Sildenafil, And Between Sitaxsentan And Tadalafil After Multiple Doses

Information source: Pfizer
ClinicalTrials.gov processed this data on August 23, 2015
Link to the current ClinicalTrials.gov record.

Condition(s) targeted: Pulmonary Arterial Hypertension

Intervention: sitaxentan (Drug); tadalafil (Drug); sitaxsentan (Drug); tadalafil (Drug); sitaxsentan (Drug); sildenafil (Drug)

Phase: Phase 1

Status: Terminated

Sponsored by: Pfizer

Official(s) and/or principal investigator(s):
Pfizer CT.gov Call Center, Study Director, Affiliation: Pfizer


Sitaxsentan has a low drug-drug interaction potential and it did not have a clinically relevant effect on pharmacokinetics of sildenafil (a CYP3A sensitive substrate and PDE5 inhibitor). Tadalafil did not have clinically relevant effect on pharmacokinetics of bosentan and ambrisentan. Based on overall clinical drug-drug interaction profiles, and in vitro CYP enzymes and transporter data, a clinically relevant drug-drug interaction between sitaxsentan and tadalafil is not expected. Sildenafil is not expected to affect sitaxsentan pharmacokinetics (PK), as sitaxsentan is a substrate of CYP3A4 and CYP2C9, where sildenafil did not show clinically relevant effect on PK of substrates of CYP3A4 and CYP2C9.

Clinical Details

Official title: A Phase 1, Open Label, Randomized, Four Period, Crossover, Multiple Dose Study To Assess The Pharmacokinetic Interaction Between Sitaxsentan and Tadalafil and The Effect Of Sildenafil On Sitaxsentan PK In Healthy Subjects

Study design: Allocation: Randomized, Endpoint Classification: Pharmacokinetics Study, Intervention Model: Crossover Assignment, Masking: Open Label, Primary Purpose: Treatment

Primary outcome:

Time to Reach Maximum Observed Plasma Concentration (Tmax)

Trough Plasma Concentrations (Ctrough)

Maximum Observed Plasma Concentration (Cmax)

Area Under the Curve of the 24 Hour Dosing Interval (AUC24)

Apparent Oral Clearance (CL/F)

Volume of Distribution at Steady State (Vss)

Secondary outcome: Plasma Decay Half-Life (t1/2)


Minimum age: 21 Years. Maximum age: 55 Years. Gender(s): Both.


Inclusion Criteria:

- Healthy male subjects and women of non-child bearing potential between the ages of 21

and 55 years, inclusive. Healthy is defined as no clinically relevant abnormalities identified by a detailed medical history, full physical examination, including blood pressure and pulse rate measurement, 12-lead ECG and clinical laboratory tests.

- Body Mass Index (BMI) of 17. 5 to 30. 5 kg/m2; and a total body weight >45 kg (99 lbs).

- An informed consent document signed and dated by the subject or a legally acceptable


- Subjects who are willing and able to comply with scheduled visits, treatment plan,

laboratory tests, and other study procedures. Exclusion Criteria:

- Evidence or history of clinically significant hematological, renal, endocrine,

pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at time of dosing) or clinical findings at Screening.

- A positive urine drug screen.

- Subjects with hepatic dysfunction, defined as aspartate aminotransferase (AST) and/or

alanine aminotransferase (ALT) >1. 5 times the upper limit of the normal range at Screening. A retest may be done if AST and/or ALT within 1. 5- to 2- times the upper limit of the normal range at Screening, and the average of the first and repeated test values should be used to decide the eligibility.

Locations and Contacts

Pfizer Investigational Site, Singapore 188770, Singapore
Additional Information

To obtain contact information for a study center near you, click here.

Starting date: November 2010
Last updated: January 18, 2012

Page last updated: August 23, 2015

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