NEW YORK, December 31, 2025, 09:15 ET — Premarket
Ultragenyx Pharmaceutical (RARE.O) shares edged down 0.2% to $22.74 in premarket trading on Wednesday, after finishing Tuesday up 15.5% at $22.78. The stock’s 52-week range is $18.41 to $46.50. 1
The rare-disease drugmaker is trying to find its footing after a sharp two-day repricing driven by a late-stage clinical setback that hit one of its higher-profile pipeline programs.
The next question for investors is whether Ultragenyx can quickly shift attention from a failed bone-disease readout to nearer-term regulatory milestones in gene therapy, while cutting costs to protect cash.
Ultragenyx said on Monday that two Phase 3 studies of setrusumab (UX143) in osteogenesis imperfecta missed their primary endpoint of reducing annualized clinical fracture rate — the number of fractures per year — versus placebo or bisphosphonates, a class of drugs used to treat low bone density. The company said both trials met secondary goals on bone mineral density and it plans significant expense reductions as it continues to analyze the data, while pointing to other upcoming pipeline catalysts. 2
The trial miss sent the stock down 43.5% on Monday to a record low, Reuters reported. Truist analyst Joon Lee said his firm had been skeptical of setrusumab in the indication and said the company’s cost-cut language implied it may sunset the osteogenesis imperfecta program; Ultragenyx ran the studies with U.K. partner Mereo BioPharma, according to the report. 3
Ultragenyx on Tuesday said it completed a rolling Biologics License Application, or BLA — the FDA filing needed to market a biologic in the United States — for its DTX401 gene therapy in glycogen storage disease type Ia (GSDIa). “The completion of our rolling submission of the BLA for DTX401 is a significant step,” Chief Medical Officer Eric Crombez said, as the company pointed to Phase 3 data showing reductions in daily cornstarch intake — a cornerstone of current disease management — and said there are no approved pharmacologic therapies for GSDIa. 4
The filing gives Ultragenyx a concrete regulatory marker after a week where the market punished uncertainty around setrusumab’s commercial path and any follow-on investment required to keep the program alive.
Traders are also watching whether the stock’s rebound holds once regular trading opens, after heavy selling and fast repositioning around the trial data.
A separate SEC filing showed Senior Vice President and Chief Accounting Officer Theodore Alan Huizenga sold 85 shares on Dec. 29 at $34.38 in a transaction marked as a sale to cover tax withholding tied to vesting restricted stock units. 5
Ultragenyx has said it is digging deeper into the Phase 3 dataset for other clinical endpoints beyond fractures, and investors will be looking for clarity on the scope and timing of expense cuts.
On the gene-therapy side, the focus shifts to the FDA’s next steps on DTX401 — including whether the agency accepts the application for review and what timeline emerges — a process that can hinge on manufacturing details as much as clinical data.
