Mesoblast finishes dosing in Phase 3 trial of rexlemestrocel-L for chronic low back pain

Mesoblast Limited said on August 17, 2026 that it has finished dosing all patients in its pivotal randomized controlled Phase 3 study, called MSB-DR004, testing rexlemestrocel-L in chronic low back pain linked to inflammatory degenerative disc disease.¹

The trial ultimately treated 350 patients, randomized to receive either an intra-discal injection of rexlemestrocel-L or a sham injection.¹ That figure grew from an original target, as enrollment rose from 300 to 350 patients after investigators pushed to add more participants to the program.¹

The study's main goal is to verify that a single intra-discal dose of rexlemestrocel-L produces lasting pain relief at the 12-month mark, replicating results from the earlier MSB-DR003 trial.¹ Mesoblast said the larger patient count gives the trial more statistical power to detect a treatment effect versus controls.¹ Beyond pain, the study is also tracking functional improvement, quality-of-life changes, and whether patients are able to stop taking pain medications, including opioids.¹

CEO Silviu Itescu called the milestone "a momentous milestone for the company as we now count down to the 12-month read-out for what we hope will be the basis of our first blockbuster product."¹

Mesoblast noted that rexlemestrocel-L holds RMAT designation from the FDA for this indication, which would make it eligible for priority review once a Biologics License Application is submitted.¹ Top-line data are expected in mid-2027, once the last patient dosed completes the 12-month follow-up period.¹