Mast Therapeutics Reports Top-Line Results from Phase 2 Study for AIR001

Mast Therapeutics, Inc. (NYSE: MSTX) today reported top-line results from a Phase 2 study of AIR001 (sodiumnitrite) inhalation solution for the treatment of pulmonary arterialhypertension (PAH).  Mast obtained the rights to the AIR001 program throughits acquisition of privately-held Aires Pharmaceuticals, Inc. earlier thisyear. In the primary efficacy analysis of the Phase 2 study, all doses showedimprovement in median pulmonary vascular resistance (PVR). In the secondaryefficacy analysis, all doses showed improvements in the median distancesobtained in the 6-minute walk test, including clinically-meaningfulimprovements at the highest dose level.  Additionally, AIR001 waswell-tolerated, with no treatment related serious adverse events. Inparticular, methemoglobin levels remained normal (< 1.5%), which distinguishesAIR001 from safety concerns associated with intravenously-administerednitrite. Edwin L. Parsley, D.O., interim Chief Medical Officer, stated: "These resultsare promising and consistent with earlier findings of AIR001 as an agent thatcan have a positive effect on hemodynamic parameters in a PH population. Todate, more than 120 individuals have received AIR001, including patients whohave received repeat administration for as long as 12 months, patients whowere treatment naive, and patients on PAH disease-specific backgroundtherapy.  Given the hemodynamic improvements observed, we feel AIR001 may beuniquely suited to address the serious unmet need facing the large number ofpatients with pulmonary hypertension associated with left heartdisease. Consequently, we will be pursuing clinical development of AIR001 inthat indication and plan to support multiple, institution-sponsored Phase 2astudies that will evaluate 1) acute hemodynamic effects, 2) acute effectsversus placebo on maximum oxygen consumption and exercise hemodynamics, and3) inhaled versus intravenous administration of nitrite, as well as the safetyof multiple doses of AIR001, in patients with PH associated with left heartdisease."Brian M. Culley, Chief Executive Officer, stated: "We are encouraged by theresults seen in the Phase 2 study of AIR001 and believe they further validateour acquisition of Aires. The data from the study show benefits consistentwith prior studies and support further development of AIR001. We look forwardto proceeding with the Phase 2a studies in PH associated with left heartdisease and anticipate reporting preliminary study results as early as thesecond half of 2015."About the Phase 2 Study (AIR001-CS05)The Phase 2 study was a multi-center, open-label, randomized, parallel-dosestudy to determine the safety and efficacy of AIR001 in subjects with PAH. Subjects were randomized into one of three treatment arms and treated withAIR001 for 16 weeks: 80 mg once daily after a 2-week "run-in" period of 46 mgonce daily; 46 mg four times daily after a 2-week run-in period of 46 mg fourtimes daily; or 80 mg four times daily after a 2-week run-in period of 46 mgfour times daily.  The primary objective of the study was to evaluate theefficacy of inhaled nebulized AIR001 as determined by change in pulmonaryvascular resistance (PVR) from baseline to week 16, measured immediatelypost-completion of AIR001 nebulization.  Secondary endpoints included changefrom baseline to week 16 in: 6‑Minute Walk Distance (6MWD) assessedimmediately post-completion of AIR001 nebulization (peak), but no more than 40minutes after completion of AIR001 nebulization; hemodynamic measurements ofcardiac output, mean right atrial pressure and pulmonary capillary wedgepressure at peak; N-Terminal Pro-Brain Natriuretic Peptide (NT-proBNP);hemodynamics and 6MWD at trough; and quality of life measures.The study was powered to enroll 90 patients, however, prior to its acquisitionby Mast, Aires discontinued the study due to capital constraints.  Data isavailable from 29 patients who enrolled in the study.