Ultragenyx and Mereo's genetic bone disease treatment cuts fractures by 67%

Six months after biomarker data lifted the prospects of Ultragenyx’s brittle bone disease treatment, newly released fracture figures are solidifying the hype.

The rare disease biotech, alongside its partner Mereo BioPharma, reported over the weekend that setrusumab reduced bone fractures by 67% across 24 patients with osteogenesis imperfecta that had at least six months of follow-up. The annualized fracture rate of 0.72 was reduced to zero within the nine-month average treatment duration period, during the phase 2 portion of the phase 2/3 trial. Ultragenyx's shares were up more than 11% as of noon ET, from $33.57 to $37.35. 

All told, 20 out of 24 patients reported no “​​radiographic-confirmed fractures,” while four patients reported seven confirmed fractures across five events. The genetic condition causes patients’ bones to fracture easily, often without any real cause. Gary Gottesman, M.D., Professor of Pediatrics and Medicine at Washington University School of Medicine, said in Saturday’s release that none of his patients have experienced a fracture yet. 

“Some of the kids feel well enough they are participating in activities that they might normally avoid and have suffered some relatively minor fractures,” he added. The fractures reported in the study excluded finger, toe, skull and face breaks. 

The new data follow previous interim results posted in June showing that setrusumab spurred a 9.4% increase in bone density three months after treatment, better than the 8.97% improvement previously seen in a phase 1/2 study. The two companies now have six-month follow-up data detailing further improvements.

Eleven patients given the 20mg dose had a 13% improvement in lumbar spine bone mineral density, while eight patients treated with 40mg reported a 16% improvement. No treatment-related serious adverse events have been reported to date, and the most common side effects have been infusion-related events and headaches. 

So far so good for Ultragenyx after it scooped up the ex-Europe rights to the drug nearly three years ago, by paying $50 million upfront and offering $254 million in biobucks. Recruitment for the phase 3 portion of the trial continues to chug along, with the pair of companies hoping to enroll 195 patients across 50 sites.