A phase 1/2a trial of Bone Therapeutics’ cell therapy treatment for delayed-union fractures has met its primary endpoint. Bone wants to move the therapy, ALLOB, into phase 2b on the strength of the data, but that plan is on hold as it adopts an industrialized manufacturing process.

ALLOB is an allogeneic osteoblastic cell therapy derived from the bone marrow cells of healthy adult volunteers. As osteoblasts are the cells that form new bone, the Belgian biotech thinks ALLOB will accelerate the healing process in patients whose fractures are taking a long time to heal. The phase 1/2a is the most thorough clinical test of that idea to date.

Investigators enrolled 21 patients with fractures that were yet to consolidate three to seven months after the original trauma. The participants received a single injection of ALLOB into the site of the fracture.

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Six months later, all of the patients had improved on either a radiological or clinical score, resulting in the trial meeting its primary endpoint. About three-quarters of patients experienced a two-point or greater improvement on the radiological tomographic union score. On average, the scores improved by 3.84 points. The same proportion of patients experienced at least a 25% improvement on the clinical global disease evaluation. On average, patients’ clinical scores improved by 48%.

With ALLOB hitting a secondary endpoint related to fracture-site pain and emerging from the trial with a clean safety profile, Bone thinks it has the data to support the start of a phase 2b. However, the company is holding off on filing to run that key larger study until the second half of next year.

The gap between the two trials relates to the optimization of Bone’s manufacturing process. During preclinical and early-phase testing, cell therapies are often made using processes that are ill-suited to the demands of commercial-scale production. These methods are fine for producing small quantities of high-quality cells but lack the consistency and efficiency required of commercial processes.

With ALLOB set to progress into phase 2b, Bone has decided now is the time to pause and make sure its manufacturing process is suitable for large-scale use. Bone has designed an improved process that it thinks will increase yield and make it easier to ship the cells to sites. But it needs to generate nonclinical data on cells made using the process before filing to run the phase 2b.