Athersys, Inc. provided an update on ongoing clinical trials with MultiStem for the treatment of patients following hemorrhagic trauma (MATRICS-1) and for the treatment of ischemic stroke (MASTERS-2). MultiStem is a proprietary off-the-shelf stem cell product in late-stage clinical trials for acute ischemic stroke, as well as trauma and other inflammatory conditions. MATRICS-1 is an investigator-initiated Phase 1/2 randomized, double-blind, placebo-controlled trial evaluating MultiStem in patients following resuscitation from hemorrhagic trauma that is underway at the University of Texas-Houston and the Memorial Hermann Hospital, the busiest Level 1 Trauma Center in the U.S. Athersys announces that complete enrollment has been reached in the second cohort in which patients were dosed with MultiStem cells manufactured under Athersys' new 3D manufacturing process.

This will provide Athersys with safety data for 3D-treated patients and comparability against 2D-treated patients in the first cohort. This trial aims to enroll 156 patients in total, and enrollment in the third and final cohort is expected to begin later in 2023. This trial is being supported in part by MTEC (Medical Technology Enterprise Consortium) in partnership with the Department of Defense.

MASTERS-2 is a company-sponsored Phase 3 randomized, double-blind, placebo-controlled trial evaluating MultiStem for the treatment of acute ischemic stroke. Athersys announces that more than half of the 300 expected patients have now been enrolled in this multinational, multicenter trial. The rate of patient enrollment significantly increased during 2022 due in part to the opening of new sites across more geographies.

More sites are expected to be activated throughout 2023. MultiStem cells deliver benefit through distinct mechanisms including reducing inflammatory damage, protecting at-risk tissue at the site of injury and upregulating reparative aspects of the local and systemic immune system in a more timely way. Data in multiple animal models of acute neurological injury led to the development of this hypothesis regarding the cell mediated mechanism of action and is supported by 2 human clinical trials evaluating the MultiStem cell product following acute ischemic stroke that leads to increased recovery benefit over time.

In November 2022, Athersys convened a meeting of stroke Key Opinion Leaders (KOLs) to discuss potential changes to the MASTERS-2 trial design, given clinical findings from Healios' TREASURE trial in Japan as well as from the MASTERS-1 study. Following input from these KOLs, Athersys is considering possible protocol adjustments in support of the overall goal of de-risking the program, while also reflecting evolving best standard-of-care. Because any protocol changes would need to be submitted to the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) prior to being implemented, it is premature to discuss what, if any, modifications might be made.