Phase IIa: Safety, PK, & Tolerability of Sodium Nitrite in Patients With Peripheral Arterial Disease-SONIC

Peripheral artery disease (PAD) is a manifestation of systemic atherosclerosis and a strong predictor of cardiovascular (CV) mortality. The systemic disease of atherosclerosis in these patients results in arterial stenoses in the arteries supplying the muscles of the lower extremities. During exercise, the stenoses limit the ability to increase blood flow, which leads to an oxygen supply/metabolic demand mismatch, a bio-energetic deficit, and subsequent muscle contractile dysfunction. Thus, the primary pathophysiology of PAD is related to the limitation in blood flow and abnormal hemodynamics (reduced tissue perfusion pressure and blood flow) of the lower limbs during exercise. Patients with PAD commonly present with symptoms of intermittent claudication (IC), often described by patients as a cramping, aching, or fatigue sensation in the calf muscles of the legs that occurs during physical activity. Notably, the symptom of claudication pain is due to exercise-induced ischemia in the muscles of the leg, causing a significant limitation of functional exercise capacity and adversely affecting quality of life. Sodium nitrite is being investigated as a potential new therapy for improving function in patients with PAD. The overall goal of this dose-ranging study is to evaluate the safety, pharmacokinetics, tolerability, and potential biological activity of multiple doses of oral sodium nitrite in patients with PAD. As described above, the primary pathophysiology of PAD is related to the limitation in blood flow of the lower extremities, resulting in limited exercise tolerance and decreased quality of life. PAD is highly prevalent in patients with diabetes, leading to poor outcomes and accelerated disease progression compared with non-diabetic counter-parts. A common feature of both patient groups is endothelial dysfunction, decreased NO bioavailability, and depletion of NO stores, a finding that may be compounded when PAD and diabetic conditions coexist. Sodium nitrite is an inorganic salt that is found and metabolized in vivo. At physiological concentrations, sodium nitrite is known to cause vasodilation, a feature which is enhanced in hypoxic or ischemic environments. The nitrite anion acts a NO reservoir and can be readily converted to active NO by a non-enzymatic reaction with deoxyhemoglobin, making it a unique candidate for potential therapeutic effect in ischemic tissues. Accordingly, this study is designed to assess the safety and tolerability of sodium nitrite as well as the pharmacokinetic and pharmacodynamic relationship of sodium nitrite at two different doses versus placebo. Sodium nitrite's effects on endothelial function, a marker of NO bioactivity, and measures of functional walking capacity will also be assessed.