NEW YORK, USA & MELBOURNE, Australia, April 28–29, 2026
Mesoblast Limited has announced that it has achieved the patient recruitment target in its pivotal Phase 3 clinical trial evaluating rexlemestrocel-L for the treatment of chronic low back pain (CLBP) associated with inflammatory degenerative disc disease. This major milestone strengthens the company’s commercialization pathway for its proprietary allogeneic stromal cell therapy, which targets the inflammatory processes underlying disc degeneration. The update is highlighted on page 1 of the uploaded PDF
Phase 3 Trial Advances Toward FDA Filing
The placebo-controlled Phase 3 study (MSB-DR004) will enroll at least 300 patients, randomized to receive either a single intradiscal injection of rexlemestrocel-L or a sham control for 12 months. The study is designed to confirm the positive findings from the earlier MSB-DR003 Phase 3 trial, where a single intradiscal injection demonstrated clinically meaningful reductions in both pain and opioid usage for up to three years.
The trial’s primary endpoint focuses on showing a significant reduction in low back pain at 12 months compared with sham controls. Secondary endpoints include improvements in function, quality of life, and cessation of opioid pain medication, addressing key clinical challenges in long-term CLBP management. According to page 1 of the PDF, top-line results are expected in mid-CY2027, following completion of patient follow-up
RMAT Designation Supports Accelerated Regulatory Pathway
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Mesoblast plans to use the Phase 3 results to support a Q3 CY2027 U.S. FDA filing for approval of rexlemestrocel-L. Importantly, the therapy has already received Regenerative Medicine Advanced Therapy (RMAT) designation from the FDA for CLBP due to degenerative disc disease, providing eligibility for priority review, rolling review, and accelerated approval pathways.
This designation significantly strengthens Mesoblast’s regulatory position and reflects the high unmet medical need in chronic low back pain treatment. CEO Silviu Itescu described this milestone as a major step toward delivering a non-opioid, disease-modifying therapy for patients suffering from chronic back pain, one of the most prevalent and disabling conditions worldwide.
Large Market Opportunity in Non-Opioid Pain Management
According to the PDF, CLBP caused by inflammatory degenerative disc disease affects more than 7 million people in the U.S. alone, with back pain remaining the leading cause of disability in Americans under age 45. The condition is closely associated with reduced quality of life, impaired daily function, and high opioid dependency, accounting for approximately 50% of prescription opioid use in the U.S. as detailed on page 2
Mesoblast estimates the indication could represent a potential blockbuster market exceeding US$10 billion annually, even with single-digit market penetration. This creates strong commercial potential for rexlemestrocel-L as the company expands its regenerative medicine leadership beyond existing products like Ryoncil®, its FDA-approved MSC therapy for pediatric SR-aGVHD.
With successful recruitment completed, strong prior Phase 3 data, and FDA RMAT support, Mesoblast is positioning rexlemestrocel-L as a potentially transformative therapy for chronic low back pain, offering a new non-opioid treatment strategy for millions of patients globally.
Source: Mesoblast press release
