Mast Therapeutics (MSTX) Announces Publication of Positive Interim Data from AIR001 Phase 2 in PH-HFpEF

November 3, 2016 9:16 AM EDT

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Mast Therapeutics, Inc. (NYSE: MSTX), announced that the Journal of Clinical Investigation (JCI) published positive interim results from an ongoing 50-patient Phase 2 study of AIR001 in patients with pulmonary hypertension (PH), including a cohort with PH associated with heart failure with preserved ejection fraction (PH-HFpEF). In the Phase 2 study, AIR001 significantly lowered pulmonary, right atrial, and pulmonary capillary wedge pressures, with a substantial increase in pulmonary artery compliance, which was most pronounced in patients with PH-HFpEF.

In the 36 patients studied to date, administration of nebulized inhaled nitrite (AIR001) significantly decreased pulmonary, right atrial, and pulmonary capillary wedge pressures, and was most pronounced in patients with PH-HFpEF. AIR001 administration also led to a substantial increase in pulmonary artery compliance, which was most pronounced in patients with PH-HFpEF. AIR001 was generally well-tolerated and no significant safety concerns were identified, satisfying the primary safety outcome of the study. In addition, there were no significant decreases in peripheral oxygen saturation nor increases in methemoglobin levels above the stopping criteria of 5%.

"The results observed to date are important as they demonstrate that AIR001 can significantly lower right atrial pressures, pulmonary artery pressures, and pulmonary artery occlusion pressures, as well as improve pulmonary artery compliance," stated Edwin L. Parsley, D.O, Chief Medical Officer of Mast Therapeutics, Inc. "In the study, AIR001 administration appears to be safe in Groups 1-3 PH and may be efficacious in Groups 2 and 3 PH with further study in non-Group 1 PH warranted."

"These data are consistent with results we saw in a separate investigator-sponsored Phase 2 study of AIR001 in HFpEF earlier this year and serve as a further step in validating AIR001 and establishing its potential clinical utility in HFpEF," stated Brian M. Culley, Chief Executive Officer of Mast Therapeutics. "We look forward to advancing AIR001 in this area of high unmet medical need for which there is no FDA-approved therapy available. In addition to full results from this 50-patient study, the 100-patient 'INDIE-HFpEF' study of AIR001 also is expected to complete enrollment and announce top-line results next year. We believe these are important value-creating studies which convincingly demonstrate the potential for clinical utility of AIR001 in HFpEF and potentially other settings."

Of the 36 patients enrolled, 10 were diagnosed with PH-HFpEF, 20 were diagnosed with World Health Organization (WHO) Group 1 pulmonary arterial hypertension (PAH) on background PAH specific therapy, and 6 were diagnosed with WHO Group 3 PH. In the 10 patients enrolled with PH-HFpEF, AIR001 administration resulted in significant overall decreases in right atrial pressure, pulmonary capillary wedge pressure, right ventricular systolic and diastolic, and pulmonary artery systolic, diastolic and mean pressures. Of note, pulmonary capillary wedge pressure and mean pulmonary artery pressure markedly decreased by 7.5 mm Hg (95%CI: -9.0, -6.0) and 7.9 mm Hg (95%CI: -9.4, -6.3), respectively (baseline median values 18 and 34 mm Hg, respectively). With significant lowering of all pressures, there was no significant change in transpulmonary gradient and a modest but significant increase in PVR. Pulmonary artery compliance increased by 35% (+0.97 mL/mm Hg, 95%CI: +0.25, +1.68; P = 0.008).

Further analysis of the dose effect of AIR001 found that most hemodynamics were affected in a dose dependent manner with the exception of pulmonary artery compliance. There was a significant dose effect on right atrial pressure, mean pulmonary artery pressure, and pulmonary capillary wedge pressure. Cardiac index decreased in a dose-dependent manner. The increase in pulmonary artery compliance was not dose related.

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