Mast Therapeutics Reports Update on Epic Study Enrollment, Offers '15 Milestones

Mast Therapeutics, Inc. MSTX, a clinical-stage biopharmaceutical company, today reported that enrollment in its pivotal EPIC study of its lead product candidate vepoloxamer (MST-188) in sickle cell disease surpassed the one-third enrollment milestone, ahead of internal projections. The Company remains on-track to complete enrollment by the end of 2015 and, consistent with prior guidance, anticipates reporting top line results in the first quarter of 2016. "We are extremely pleased to report that, as of today, 130 patients have been randomized to the EPIC study, which is ahead of the enrollment projections we set for ourselves more than a year ago," stated Brian M. Culley, Chief Executive Officer. "We now have opened almost 70 sites in ten countries, with more than 50 of those sites located in the U.S. I am pleased to affirm that we remain on-track to complete enrollment this year, which means we expect to announce top line data in the first quarter of 2016. As there has never been a drug approved for sickle cell patients to treat an ongoing crisis, we are both hopeful and excited for a positive outcome from the EPIC study." "We have built a sense of camaraderie with the sickle cell medical community and are enjoying a groundswell of momentum that is helping to drive enrollment," added Edwin L. Parsley, D.O., Chief Medical Officer. "Of note, approximately 60% of the sites we have opened in EPIC have enrolled at least one subject and two-thirds of those sites have enrolled two or more subjects. This broad activity indicates that investigators worldwide are excited about the study and are encouraging their patients to participate." "I am also pleased to highlight that the EPIC study's independent Data and Safety Monitoring Board ("DSMB") has held multiple pre-planned meetings and recommended that the study proceed without any changes," added Dr. Parsley. Additional milestones anticipated from the Company in 2015 include: o Reporting data from a repeat-dose nonclinical study of vepoloxamer in heart failure; o Initiating a Phase 2 clinical study of vepoloxamer in acute decompensated heart failure; o Initiating enrollment in an open-label EPIC extension study, referred to as EPIC-E, to expand the Company's existing safety database regarding repeat exposure to vepoloxamer; o Reporting data from a nonclinical study of vepoloxamer in embolic stroke; and o Reporting data from one or more of the Phase 2a studies of AIR001 in patients suffering heart failure with preserved ejection fraction (HFpEF). Conference Call Information Interested parties may access the conference call on Tuesday, January 6, 2015 by dialing (877) 870-4263 from the U.S. and (412) 317-0790 from outside the U.S. and should request the Mast Therapeutics, Inc. Corporate Update Call. The webcast will be available live via the Internet by accessing the Investors section of Mast's website at http://www.masttherapeutics.com/investors/events/. Replays of the webcast will be available on the Company's website for 30 days and a phone replay will be available through January 15, 2015 by dialing (877) 344-7529 from the U.S. and (412) 317-0088 from outside the U.S. and entering conference reference number 10057420.