Carbon Monoxide Therapy for Severe Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) remains an uncommon debilitating and fatal disease, and is clinically marked by a progressive increase in pulmonary vascular resistance leading to right heart failure and ultimately death. Currently the treatment options available for those suffering from PAH target cellular dysfunction that leads to constriction of the vasculature. Although there is some evidence that available therapies have secondary effects on vascular remodeling there are currently no therapies that target abnormal cell proliferation in PAH. Carbon monoxide (CO) is a gaseous molecule with known toxicity and lethality to living organisms when exposed to high concentrations for sustained periods. However, CO has shown promise in preclinical models of pulmonary hypertension. Recent studies have shown that mammalian cells have the ability to generate endogenous CO primarily through the catalysis of heme by the heme oxygenase enzymatic system and there is ample evidence demonstrating that CO behaves as a signaling molecule in cellular and biological processes. Furthermore, CO has been demonstrated to exert key physiological and protective functions in various models of tissue inflammation and injury. This study will evaluate the safety and potential efficacy of inhaled CO in subjects with severe PAH. Over forty subjects with severe PAH despite best available therapy will be screened from the UIC pulmonary vascular disease clinic, of which twenty subjects will be recruited for participation in the trial. The trial will consist of an initial screening period to determine subjects' eligibility for the study. This will be based on a previous echocardiogram, a six minute walk test and right heart catheterization done as part of standard care for subjects with pulmonary arterial hypertension. Following the initial screening, the trial will last sixteen weeks, during which subjects will receive inhaled carbon monoxide up to three times weekly at the University of Illinois at Chicago.