Ultragenyx Tumbles After Setrusumab Fails Two Clinical Trials

Ultragenyx Pharmaceutical Inc. sank after the company’s experimental drug for a rare genetic bone disease failed to meet the primary endpoints in two phase 3 clinical trials.

Ultragenyx dropped 43% at 9:42 a.m. in New York Monday. Its shares had fallen 19% year to date through the close on Dec. 26.

The medicine, setrusumab, was being studied to treat osteogenesis imperfecta, a condition that makes people more prone to bone fractures. The drug did not reduce the annualized fracture rate compared with a placebo group in one trial, nor did it statistically significantly reduce the annualized fracture rate compared with ...