Not an 'excellent outcome' for Athersys stock as stem cell therapy misses endpoint in Japanese trial

Athersys’ shares nosedived over 60% to 30 cents as the markets opened today after the company revealed its stem cell therapy for stroke patients failed to meet the primary endpoint of a phase 2/3 trial.

Results from a trial by Athersys’ Japanese partner Healios showed that patients with ischemic stroke who received a single dose of the MultiStem therapy did not show a statistically significant achievement of the primary endpoint of an “excellent outcome” at 90 days.

MultiStem is designed as an off-the-shelf cell therapy to promote tissue repair and healing in a variety of ways, such as in response to signals of inflammation and tissue damage. The therapy has received both the fast-track and regenerative medicine advanced therapy designations from the FDA.

The randomized, double-blind trial, dubbed TREASURE, enrolled 206 patients across 48 sites in Japan. Patients received either the stem cell treatment, also known as invimestrocel, or placebo within 18-36 hours of their moderate or moderate-severe ischemic stroke.

The patient population of the TREASURE study had an average age of 78 years, making it substantially older than the average of 63 years for participants in Athersys’ previous study for the therapy, called MASTERS-1. The population for an ongoing phase 3 study called MASTERS-2 is also supposed to be younger with lower average stroke severity, the company said.

Due to the older demographic, a slower and less robust recovery among patients in the TREASURE study was to be expected, Athersys claimed. That means measures such as the modified Rankin Score (mRS) and the Barthel Index were more clinically relevant than the primary endpoint of “excellent outcome” when assessing the trial’s findings, the company argued. 

The therapy scored less than or equal to 2 on the mRS, a seven-point scale of disability, and more than or equal to 95 on the Barthel Index, which evaluates a patient’s ability to perform specific activities of daily living on a 100-point scale. Both scales are typically used to assess clinical outcomes after stroke.

Nevertheless, without a win on the primary endpoint, the study was unsuccessful. 

There were no material differences in safety outcomes, including mortality and life-threatening adverse events, between the treatment and placebo groups in the TREASURE study, the company said.

“We are enthusiastic about the topline results from the TREASURE ischemic stroke trial in Japan,” Athersys CEO Dan Camardo said in a statement. “The preliminary data analyses suggest a path forward for our partner, Healios, in Japan, and gives us further confidence in our MASTERS-2 phase 3 ischemic stroke study being conducted in the U.S., Europe and the Asia-Pacific region. We look forward to continued collaboration with Healios in working to bring this important therapy to the market in Japan.”