Treprostinil Combined With Tadalafil for Pulmonary Hypertension

Background: Many cardiovascular diseases such as essential hypertension, coronary artery disease and congestive heart failure respond better to combinations of vasoactive drugs, than to therapy with a single agent. Three categories of pulmonary anti-hypertensive medications have been developed over the last 20 years, but their effect on management of PAH when used in combination are mostly unknown. Two of the pulmonary arterial hypertension (PAH) drug groups are prostacyclines, and PDE5 inhibitors. Although the effects of prostacyclins are mediated via cAMP (cyclic guanosine monophosphate) and the effects of PDE5 inhibitors are mediated via cGMP, there is considerable cross talk between these nucleotides suggesting that adequate levels of both may be needed to maintain normal pulmonary vascular tone and cellular growth responses. Objective/Hypothesis: This proposal hypothesizes that increasing the levels of both nucleotides (prostacyclines and PDE5 inhibitors), may be more efficacious in the treatment of PAH than increasing either one alone. Specific Aims: The primary objective of this study is to determine if the combination of treprostinil infusion combined with tadalafil is more efficacious than treprostinil alone in improving the change from baseline in the 6 minute walking distance after 16 weeks of therapy. Study Design: The proposed study is a multi-center, randomized, double blind, two cohort, parallel group, and 16-week study with 1-year long-term follow-up. The study aims to compare the efficacy of combination therapy with treprostinil infusion and tadalafil to treprostinil infusion alone. Study Population: All patients who have been newly diagnosed with PAH and who, after consultation with their physician, have elected to be treated with treprostinil infusion will be invited to participate. A total of 66 subjects will be sort to enroll. Treprostinil dosing will follow a 4 week up-titration schedule with a target 4week dose of 8ng/kg/min minimum, followed by a 12 week randomized tadalafil period.