Ultragenyx, Mereo drug lessens fractures in bone disorder study

Ultragenyx Pharmaceutical and Mereo BioPharma have reported promising early results from their experimental treatment for osteogenesis imperfecta, a rare bone disorder. The disorder affects bone metabolism, increasing susceptibility to fractures and deformities. Their new drug, setrusumab, aims to inhibit sclerostin, a protein known to impair bone formation.

In October 2023, Ultragenyx and Mereo revealed that setrusumab significantly reduced fractures and increased lumbar spine bone mineral density in patients monitored for at least six months. Recent findings indicate these beneficial effects continued for up to 14 months, with ongoing improvement in bone density.

These results provide optimism for investors ahead of the first readout of the Phase 3 component of the companies' Orbit trial, expected by the end of this year or early next year. Safety data is also reassuring, as there have been no serious treatment-related side effects. The most common adverse events were headaches and reactions to infusions.

The Phase 2 part of the study involved 24 patients aged 5 to 25, all of whom had experienced at least one fracture in the two years before the trial. Participants received one of two doses of setrusumab, resulting in a 67% reduction in the annualized fracture rate. Following these initial successes, researchers moved on to Phase 3, which includes an additional 158 patients randomized in a 2:1 ratio to either receive the drug or a placebo. Additionally, a separate Phase 3 trial, called Cosmic, is being conducted in patients under the age of seven.

Ultragenyx and Mereo began their collaboration on setrusumab in December 2020. The latest results add to a series of successes for Ultragenyx, including a positive Phase 3 trial for a gene therapy aimed at glycogen storage disease announced in May. Following the new findings, Ultragenyx shares rose by nearly 2%, while Mereo's stock saw a nearly 10% increase.