Safely Change From Bosentan to Ambrisentan in Pulmonary Hypertension

Phase 4

Completed

Brief Summary: The primary objective of this study is to assess the safety and tolerance of changing patients currently on bosentan to ambrisentan for the treatment of pulmonary arterial hypertension.

Detailed Description: The therapy of pulmonary arterial hypertension (PAH) has been revolutionized with the development and subsequent instruction of oral endothelin receptor antagonists (ERA). The first approved ERA, bosentan (Tracleer, Actelion, Inc.) is an effective drug widely used throughout the world in the therapy of PAH. Newer ERA's, with purported advantages over the first approved drug have since been tested and subsequently been approved for the therapy of PAH in the USA and other countries including ambrisentan (Letairis, Gilead Sciences, Inc.). However, there is little data available on the efficacy, safety and tolerability of the elective change from oral bosentan to oral ambrisentan in PAH.

Recruitment & Eligibility

Inclusion Criteria

Patients followed routinely in the pulmonary vascular disease clinic at the University of Alabama in Birmingham, greater than or equal to 19 years of age.
World Health Organization (WHO) PAH Type I
WHO class I-IV symptoms (no functional class exclusion).
On bosentan, twice a day, with a maximum daily dose of 250mg, on a stable dose for 3 months with no clinical indication to discontinue the drug (i.e., increased liver function studies or other intolerance). Patients may be on other drug therapies for PAH, and also may be on oxygen therapy (intermittent or continuous).

Exclusion Criteria

Known intolerance or allergy to ambrisentan.
Prior therapy with ambrisentan.
Current therapy with two phosphodiesterase-5 inhibitors.
Change in other approved therapy for PAH (including phosphodiesterase-5 inhibitors and prostanoids) within 4 weeks of baseline study visit.
Planned addition of prostanoid for clinical reasons within 3 months of baseline study visit.
Active participation in another clinical study involving the medical therapy of PAH.
Uncontrolled systemic hypertension or angina pectoris
Serum creatinine greater than 2.5 at or within 4 weeks of baseline.
Serum liver function studies greater than 3 x normal at or within 4 weeks of baseline study visit.
In the opinion of the investigator, a change in PAH therapy would present significant risk to the subject.
In the opinion of the investigator, the participant is unlikely to survive for 12 weeks after study entry.
In the opinion of the investigator, the participant is likely to undergo lung or heart-lung transplantation within 12 weeks of study entry.
A woman of childbearing potential who is not using an acceptable form of contraception.
Pregnancy.
In the opinion of the investigator, a participant who is not capable or willing to follow the study procedures.

Arm && Interventions

Group	Intervention	Description
Ambrisentan	ambrisentan	patients currently on bosentan to ambrisentan for the treatment of pulmonary arterial hypertension.

Primary Outcome Measures

Name	Time	Method
Number of Subjects Not Able to Tolerate Ambrisentan	baseline to 12 weeks	If a subject was not able tolerate ambrisentan, subject was returned to use of bosentan and ambrisentan was withdrawn within first 12 weeks of start. A subject was considered to not be able to tolerate ambrisentan if they experienced an adverse event or side effect that was not acceptable to the subject.

Secondary Outcome Measures

Name	Time	Method
Mean Change in Distance for a Six Minute Walk at 12 Weeks Post Start of Ambrisentan	baseline to 12 weeks	Evaluate the change in exercise tolerance. Measured the distance a subject was capable of walking in 6 minutes at basline compared to the distance at 12 weeks. The distance was measured in meters. A postive result reflects the distance increased at 12 weeks, a negative result reflects how much shorter the distance was.