New York, USA / Melbourne, Australia
August 17, 2026: Mesoblast Limited has completed patient treatment in its pivotal Phase 3 MSB-DR004 clinical trial evaluating rexlemestrocel-L for chronic low back pain (CLBP) associated with inflammatory degenerative disc disease. The milestone follows the randomization and treatment of 350 patients, who received either a single intradiscal injection of rexlemestrocel-L or a sham injection. The enrollment target was increased from 300 to 350 patients following strong demand from investigators, strengthening the clinical dataset for the pivotal study. The trial is designed to evaluate whether rexlemestrocel-L can provide durable pain reduction at 12 months following a single injection, building on findings from the earlier MSB-DR003 Phase 3 study. The program represents an important development in cell-based therapy for chronic low back pain, an area with substantial unmet medical need and limited disease-modifying treatment options.
Phase 3 Trial Reaches Key Treatment Milestone
The MSB-DR004 Phase 3 trial is a randomized, controlled study designed to confirm the efficacy of rexlemestrocel-L in patients with chronic low back pain caused by inflammatory degenerative disc disease. The primary endpoint focuses on pain reduction at 12 months, while secondary measures include changes in physical function, quality of life and pain medication use, including opioids. Mesoblast has worked with the U.S. FDA on the pivotal trial design and the 12-month primary endpoint. The company expects the expanded enrollment of 350 treated patients to provide a robust dataset for evaluating the treatment effect against the sham-control group. Top-line results are expected in mid-2027, after the final treated patient completes the required 12-month follow-up. Rexlemestrocel-L has also received Regenerative Medicine Advanced Therapy (RMAT) designation from the FDA, potentially supporting an expedited regulatory pathway if the pivotal study produces positive results.
Rexlemestrocel-L Targets Inflammatory Disc Disease
Rexlemestrocel-L is a second-generation allogeneic stromal cell therapy developed using Mesoblast’s STRO3-immunoselected technology and industrial-scale manufacturing platform. The candidate is designed to address the inflammatory component of degenerative disc disease, rather than simply managing pain symptoms. Chronic low back pain associated with degenerative disc disease affects more than 7 million people in the United States, creating a significant medical and socioeconomic burden. The condition can impair mobility, daily activities, employment and quality of life, while also contributing substantially to prescription opioid use. Mesoblast is therefore evaluating whether a single intradiscal administration of rexlemestrocel-L could provide sustained clinical benefits. The company is particularly focused on whether successful treatment could reduce pain while improving function and potentially decreasing reliance on pain medications. The completion of treatment in all 350 participants now moves the program toward its next major clinical milestone: the 12-month efficacy readout in 2027.
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Mesoblast Advances Cellular Medicine Pipeline
The completion of MSB-DR004 represents another significant step in Mesoblast’s allogeneic cellular medicine pipeline, which is focused on inflammatory and degenerative diseases. The company’s proprietary mesenchymal lineage cell technology is designed to release anti-inflammatory factors capable of modulating multiple components of the immune response. Alongside rexlemestrocel-L for chronic low back pain, Mesoblast is developing the cell therapy for additional indications, including heart failure, while its remestemcel-L platform supports development programs in inflammatory diseases. Mesoblast’s Ryoncil became the first FDA-approved mesenchymal stromal cell therapy for pediatric steroid-refractory acute graft-versus-host disease, providing clinical and regulatory experience for the company’s broader cellular medicine strategy. With treatment now completed in the pivotal low back pain trial, investor and industry attention will increasingly focus on the mid-2027 topline results and their potential implications for the future development and regulatory strategy of rexlemestrocel-L in degenerative disc disease.
Source: Mesoblast press relese
