SAN DIEGO, July 23, 2013 /PRNewswire/ -- Mast Therapeutics, Inc. (NYSE MKT: MSTX) today announced results of its thorough QT/QTc study of MST-188, an investigational agent being developed to treat serious or life-threatening diseases with significant unmet needs, such as sickle cell disease and acute limb ischemia. The study met its primary endpoint and demonstrated that, based on analysis of electrocardiograms, MST-188 did not have an adverse effect on cardiac repolarization, as measured by prolongation of the QT interval. MST-188 was generally well-tolerated at both therapeutic and supratherapeutic doses. Brian M. Culley, Chief Executive Officer, said: "I congratulate our clinical operations team for successfully executing the first clinical study of MST-188 since we acquired the program. The results from this trial augment the safety data supporting MST-188 and our belief that MST-188 will demonstrate a favorable risk/benefit profile in our on-going Phase 3 study in sickle cell disease, as well as our planned Phase 2 study in acute limb ischemia." Details of the Thorough QT/QTc Study The study was a single center, four-period, four-way cross-over, placebo- and positive-controlled, double-blind, randomized clinical trial in healthy volunteers that compared the effects of MST-188 at therapeutic and supratherapeutic doses to placebo and moxifloxacin (an antibiotic known to prolong the QT interval) on cardiac ventricular repolarization, specifically, Fridericia's corrected QT-Interval (QTcF) from the surface electrocardiogram. The primary endpoint was to confirm a lack of effect of MST‑188 on QTcF. The QT interval represents the time required for the heart to repolarize after each beat. As prolongation of the QT interval may increase the risk for cardiac arrhythmias, the FDA requires a QT study for most new drugs. A QT study is a specialized clinical trial designed to assess whether an investigational medication has the potential to prolong the QT interval.