Bone Therapeutics halts phase 3 for futility, sinking stock

A bone marrow harvest in progress
The harvesting of bone marrow. (Wikipedia/public domain/Navy news service)

Bone Therapeutics has stopped a phase 3 trial of its autologous cell therapy early for futility. The data committee ruled Preob is unlikely to improve outcomes in patients with osteonecrosis, wiping 25% off Bone Therapeutics’ stock price.

Preob is an autologous osteoblastic cell therapy derived from the bone marrow of patients. Belgium’s Bone Therapeutics thought the cells could help patients with osteonecrosis, a disease arising from loss of blood to the bone. The phase 3 tested this hypothesis by randomizing patients to receive an injection of 20 million Preob cells or placebo on top of the surgical treatment for osteonecrosis. 

Bone Therapeutics’ hypothesis is now in tatters. Looking at data at the halfway point of the two-year trial, an independent committee recommended stopping the study due to overwhelming evidence of the futility of the treatment. Bone Therapeutics has stopped enrollment in the study.

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The setback sent shares in Bone Therapeutics spiraling downward and wiped out a near-term sales opportunity. However, the situation could have been worse. Bone Therapeutics had planned to run a phase 2b/3 trial of Preob in the U.S. but scrapped that idea two years ago as part of a partial pivot toward allogeneic cell therapy Allob. By then, Allob had already superseded Preob in osteoporosis.

With Preob floundering in phase 3, off-the-shelf cell therapy Allob is now taking center stage at Bone Therapeutics. Allob successfully completed a phase 1/2a delayed-union fracture trial in September but progress into phase 2b is on hold while Bone Therapeutics industrializes its production process. 

The manufacturing changes have pushed back the start of the phase 2b until the second half of next year. By then, Bone Therapeutics should have published phase 2a data on Allob in spinal fusion. Bone Therapeutics is due to run out of money at the end of the third quarter of 2019.