RARE is the biggest single-name drop on the board this morning. Ultragenyx plunged more than 46% to an all-time low on Thursday amid multiple downgrades after the Phase 3 Aspire trial for apazunersen (GTX-102), its experimental therapy for Angelman syndrome, failed to meet its key endpoints.
The study did not achieve the primary endpoint of change from baseline in Bayley-4 cognitive raw score, nor the key secondary endpoint of net response in the Multidomain Responder Index. The randomized groups were comparable at baseline, and no efficacy differences were observed between treated and control groups on Bayley cognition scores or the MDRI, including all five individual MDRI components. A clean safety profile was cold comfort: the drug simply showed no benefit against a sham control in nearly 130 patients.
The failure has forced Ultragenyx to assess its planned operations, with the company saying it intends to focus on its growing commercial business. Significant expense reductions are coming, though the company has not specified what those will entail. Layoffs have not been ruled out.
Why the Drop Is This Severe
Interim Phase 1/2 results in April 2024 had shown rapid and clinically significant improvement in cognition on Bayley-4 relative to natural history data, alongside behavioral gains, a signal strong enough to justify a pivotal program. That history matters. The market had priced apazunersen as a genuine commercial opportunity, not a long shot. The Phase 3 failure does not mean the earlier data were wrong, but it illustrates how profoundly Angelman syndrome resists translation from open-label, smaller cohorts to randomized, controlled trials.
The analyst reaction has been swift and broad. Wells Fargo downgraded RARE from overweight to equal weight and set an $18 price target. JPMorgan lowered its rating from overweight to neutral with a $36 target. Robert W. Baird cut its rating from outperform to neutral and slashed its price target from $40 to $16. Canaccord Genuity dropped its target from $83 to $37. Shares were trading near $14.87 at midday Thursday on volume of more than 7.3 million shares, against an average of roughly 2.2 million.
What Remains
The company is not without assets. Ultragenyx has a handful of approved therapies, including the gene therapy GENGLYCOS, approved on August 19, 2026 for glycogen storage disease type Ia. In Q2 2026, the company posted the highest quarterly revenue in its history. Management’s 2027 profitability target is now the load-bearing claim holding the thesis together.
The more immediate pressure point is UX111, the Sanfilippo syndrome gene therapy. The FDA has a PDUFA date of September 19, 2026 for the resubmitted BLA, which follows a complete response letter issued on July 11, 2025 over CMC and manufacturing inspection observations. If approved, UX111 would be the first approved therapy for MPS IIIA in the U.S. That decision now carries the weight of a company that just lost half its market cap and is restructuring around whatever is left standing.
What to Watch
- RARE price action around $14-15, watch for institutional selling or stabilization as the dust settles.
- UX111 PDUFA (September 19): approval would provide meaningful commercial offset; a second rejection would compound the damage severely.
- Expense reduction details: the scope of cost cuts and any workforce announcements will define the new operating baseline.
- Apazunersen program decision: Ultragenyx has not yet released detailed statistical data or specified next steps, and has not disclosed whether it plans additional analyses, regulatory discussions, or discontinuation.