Mesoblast Completes Phase 3 Back Pain Dosing, Readout Due 2027

Mesoblast (ASX:MSB) has completed patient treatment in the Phase 3 trial of its cell therapy for chronic low back pain. All 350 participants in the MSB-DR004 study have now received either a single intradiscal injection of rexlemestrocel-L, delivered into the spinal disc, or a sham procedure.

The trial's primary endpoint is pain reduction at 12 months, testing whether one injection can produce durable relief rather than a short-lived effect. Secondary measures cover physical function and quality of life. The study also records whether patients cut back on pain medication, including opioids, and low back pain is among the most common reasons Americans receive opioid prescriptions.

Mesoblast said the 350-patient cohort gives the study enough statistical power to detect a treatment benefit over the sham arm. The sham comparator is there for a reason: pain studies carry a high placebo response, and the design must separate any real effect from that expectation. Rexlemestrocel-L is aimed at inflammatory degenerative disc disease. In that condition, ongoing inflammation sits behind the disc breakdown and the pain signal.

This is the second Phase 3 run for rexlemestrocel-L in the same condition. The earlier MSB-DR003 study met its 12-month primary endpoint, and Mesoblast designed MSB-DR004 to repeat that result at a larger scale. A confirmatory read needs to show an effect of similar size; significance alone is a lower bar. The company frames the coming result as the decision point on whether the therapy advances toward a US regulatory submission.