This page aggregates RARE's FDA catalysts from pdufa.bio's own calendar and decision archive. Each item links to its source page. Facts and dates only; verify against primary FDA / SEC / company filings.
Computed from this stock's own daily closing prices, on the same T-120 basis as the run-up study: the baseline is the close 120 trading sessions before the eve of the decision. These are measurements of what already happened, not predictions.
| Decision | Outcome | T-120 to eve | T-120 to peak |
|---|---|---|---|
| 2026-08-19 | APPROVAL | +11.3% | +56.6% |
| 2025-07-11 | CRL | -24.3% | +11.7% |
| 2022-05-19 | CRL | -38.5% | +13.3% |
| 2020-06-30 | APPROVAL | +65.0% | +75.2% |
| 2020-06-18 | APPROVAL | +56.0% | +63.8% |
Both are one-time gene therapies given as a single infusion into a vein. DTX401 treats a liver disease in which the body cannot release its stored sugar, so patients must eat raw cornstarch around the clock, including waking at night, to stop their blood sugar crashing. UX111 treats Sanfilippo syndrome type A, a fatal childhood brain disease with no approved treatment, where a missing enzyme lets waste build up and destroy brain cells. In both cases the therapy delivers a working copy of the missing gene and the aim is to slow the disease, not to cure it.
In clinical terms. DTX401: AAV8-vectored liver-directed gene therapy delivering the G6PC gene under its native promoter to restore glucose-6-phosphatase activity in hepatocytes; single IV infusion at 1.0 x 10^13 GC/kg. UX111: self-complementary AAV9 delivering the SGSH gene to restore sulfamidase; transduced cells secrete functional enzyme taken up by neighbouring neurons, single IV infusion at 3 x 10^13 vg/kg. Source
This is the stronger of the two datasets, because it is randomised, blinded and placebo-controlled, which is the most reliable design available. Patients on the gene therapy cut their daily cornstarch by 41% against 10% for placebo, and by week 96 the reduction had deepened to about 61%. Two thirds dropped at least one nighttime dose. The honest qualification is what was measured: the main endpoint is treatment burden, meaning how much cornstarch someone has to eat, not a hard health outcome like fewer hypoglycaemic emergencies. Blood sugar control was shown to be maintained rather than improved, and the quality-of-life measure at week 48 favoured the drug but did not reach statistical significance.
The numbers. Primary endpoint, percent reduction in daily cornstarch intake at week 48: -41.3% (n=20) against -10.3% for placebo (n=24), p<0.0001. Reduction in doses per day -1.1 against -0.2, p=0.0011. Glucose control non-inferiority established, p<0.0001. Patient Global Impression of Change at week 48 median 2.0 against 1.0, p=0.132, not significant. Responders at 30% or greater reduction: 68% against 13%. Week 96 open-label extension: mean 61% reduction from baseline in both original and crossover groups. 48-week randomised, double-blind, placebo-controlled, ages 8 and over. Safety: liver enzyme elevations managed with prophylactic corticosteroids, and hypertriglyceridaemia more frequent after treatment. No dorsal root ganglion toxicity, thrombotic microangiopathy or malignancy through week 96. Source
The effects reported here are large and the follow-up is unusually long for a gene therapy, out to eight and a half years. But there was no control group. Every child received the drug, and the comparison is against records of how untreated children with the same disease normally decline. That method can overstate a benefit if the two groups differ in ways nobody accounted for. The numbers are also very small, seventeen children in the main analysis. One of the five developmental measures, gross motor skills, did not reach statistical significance. Because this is an accelerated approval filing, the primary basis is a laboratory marker rather than a confirmed clinical outcome, which by design carries an obligation to confirm the benefit later.
The numbers. Open-label, single-arm, non-randomised, assessed against external natural-history controls. Surrogate endpoint, cerebrospinal fluid heparan sulfate exposure: median -63.98%, p<0.001. Bayley-III cognitive raw score against natural history, ages 24 to 60 months (n=17): +23.2 points, p<0.0001. Receptive communication +8.1, p=0.0076. Expressive communication +11.1, p=0.0008. Fine motor +9.0, p=0.0026. Gross motor +3.9, p=0.070, not significant. Median follow-up 4.8 years, range 0.6 to 8.5. Sanfilippo syndrome type A is uniformly fatal and has no approved treatment, which is the context in which the FDA weighs evidence of this kind. Source
The FDA turned this application down in July 2025. According to Ultragenyx the letter was about manufacturing and facility inspection findings, and raised no issue with the clinical data or the clinical inspections. The company resubmitted in January 2026 and the FDA accepted it in April, setting the new September decision date. Whether the manufacturing observations have since been formally cleared is not something we can verify from any public FDA document.
The numbers. Complete Response Letter issued 11 July 2025. Ultragenyx states the FDA requested additional information on specific chemistry, manufacturing and controls aspects plus observations from recently completed facility inspections, and asked for updated clinical data from current patients. BLA resubmitted 30 January 2026, accepted 2 April 2026. Source
It is worth seeing these two applications side by side, because they are not comparable. DTX401 was tested the rigorous way: patients were randomly assigned, nobody knew who got what, and the drug beat a placebo. UX111 was not. Every child in that study received the drug, and the benefit is measured against historical records of untreated children. Neither approach is wrong. Randomising children with a rapidly fatal brain disease to placebo raises real ethical problems, and the FDA accepts external comparisons in that situation. But the confidence a reader should attach to each result is different, and a headline that reports both as positive Phase 3 data flattens a distinction that matters. [1] [2]
Closing price on the announcement date against the previous close, measured from daily data when this page was built. Announcements made before the open move that day; announcements after the close move the next session. This records what happened, and does not claim the announcement caused it.
| Date | Event | Move | Close |
|---|---|---|---|
| 2026-04-02 | UX111 resubmission accepted, September PDUFA date set | +4.8% | $21.42 to $22.45 |
| 2026-02-23 | DTX401 accepted with Priority Review, August PDUFA date set | -0.9% | $22.72 to $22.51 |
| 2026-02-03 | UX111 longer-term data presented | +0.2% | $24.76 to $24.80 |
| 2026-01-30 | UX111 BLA resubmitted | -0.8% | $24.27 to $24.07 |
| 2025-09-08 | DTX401 week 96 data | -1.0% | $31.82 to $31.51 |
| 2025-07-11 | UX111 Complete Response Letter disclosed | -4.9% | $31.04 to $29.51 |
Compiled from primary sources and last reviewed 2026-08-03. Every figure above links to the filing, regulator document or journal it came from. This is information, not investment advice, and nothing here forecasts an FDA decision.
September 19, 2026. The next catalyst for Ultragenyx Pharmaceutical Inc. is UX111 - (ABO-102) (PDUFA). That date is a confirmed date. 3 further catalysts are scheduled after it. Dates are taken from FDA notices, company filings or ClinicalTrials.gov, and we do not publish a specific day when the source only gives a month or a quarter.
Yes, 2 in our archive: 1 approval(s) and 1 Complete Response Letter(s). The most recent was on August 19, 2026 and was an approval. Each one has its own page with the source document and the share-price reaction we measured.
Measured from this company's own daily closing prices: Median across these 5 decisions: +11.3% from T-120 to the eve, +56.6% to the peak. These are historical measurements of what already happened, not forecasts, and we publish no price targets or probability of approval.
FDA publications, company filings with the SEC, company press releases and ClinicalTrials.gov, with share prices measured from daily closing data. Every date and outcome links the document it came from. Where an outcome was inferred from the price reaction rather than read from a filing, the page says so on its face.