Mesoblast finishes dosing its Phase 3 disc-injection cell therapy

Mesoblast said on 17 August 2026 that every patient in MSB-DR004 has now been treated. The trial randomised 350 people with chronic low back pain from inflammatory degenerative disc disease of less than five years’ standing, each receiving a single injection into the disc of either rexlemestrocel-L or a sham.

Rexlemestrocel-L is an allogeneic cell therapy: mesenchymal stromal cells selected on the STRO-3 marker from a donor, manufactured in batches and given off the shelf rather than made per patient. The primary endpoint is durable pain reduction at twelve months from that one injection, with function, quality of life and opioid cessation as secondary measures. Because the last patient must complete a year of follow-up, results are expected around mid-2027.

The endpoint has been met once before, in the predecessor trial MSB-DR003, and the therapy holds Regenerative Medicine Advanced Therapy designation from the FDA, which would make it eligible for priority review on a filing.

Finishing dosing is a scheduling milestone, not a finding, and it is worth logging for a specific reason: the endpoint here is durability. A single injection asked to hold pain down for a year is a different claim from a drug taken daily, and it is the claim that decides whether degenerative disc disease becomes a condition treated once rather than managed indefinitely.