Ultragenyx plummets after bone disease drug fails late-stage trials

Shares of Ultragenyx Pharmaceutical RARE.O plunge 42.5% to $19 premarket

RARE says its experimental drug for a type of genetic bone disease did not meet the main goal in late-stage studies

The drug, setrusumab, was being developed for people with osteogenesis imperfecta, a rare genetic disorder that causes brittle bones

While the studies did not achieve statistical significance on fracture reduction, both showed meaningful improvements in bone mineral density, a key indicator of bone strength - RARE

As of last close, stock was down 18.7% YTD