Athersys, Inc. announced that the independent data safety monitoring board (DSMB) has completed a pre-planned interim analysis of the Company?s ongoing Phase 3 MASTERS-2 pivotal clinical trial evaluating MultiStem® for the treatment of acute moderate-to-severe ischemic stroke, and concluded that the current sample size of 300 patients is insufficiently powered to achieve the primary endpoint of mRS Shift analysis at Day 365. There were no safety issues identified. Because the sample size required to achieve statistical significance is considerably larger, Athersys intends to conduct additional data analysis with independent statisticians.

The Company plans to pause enrollment of new patients while this analysis is being conducted.