This page aggregates IONS'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 |
|---|---|---|---|
| 2026-06-24 | APPROVAL | -5.0% | +8.2% |
| 2026-03-30 | APPROVAL | +4.3% | +25.1% |
| 2025-09-23 | CRL | +103.4% | +113.5% |
| 2025-08-21 | APPROVAL | +36.6% | +39.6% |
| 2024-12-19 | APPROVAL | -23.9% | +8.8% |
| 2023-12-22 | APPROVAL | +19.5% | +25.7% |
| 2023-12-22 | APPROVAL | +19.5% | +25.7% |
| 2023-04-25 | APPROVAL | -19.9% | +1.9% |
| 2023-03-22 | APPROVAL | -15.7% | +10.1% |
Alexander disease is an ultra-rare inherited brain disorder. A faulty gene makes the brain's support cells produce far too much of a protein called GFAP, which builds up and progressively damages the brain. It usually begins in early childhood and is usually fatal. Zilganersen is given by injection into the fluid around the spinal cord, through a lumbar puncture, once every twelve weeks, and instructs the body to make less of that protein. The goal is not to cure the disease but to slow it, for example to stop a child's walking from continuing to deteriorate.
In clinical terms. Antisense oligonucleotide administered by intrathecal bolus injection every 12 weeks, targeting GFAP messenger RNA to reduce production of glial fibrillary acidic protein in the central nervous system. Wholly owned by Ionis in the US; Recordati holds rights outside the US. Source
The design here is unusually good for a disease this rare. Patients were randomly assigned, neither they nor their doctors knew who was getting the drug, and it was compared against a placebo rather than against records of past patients. Walking speed, the main measure, improved by 33% relative to the control group. The result to keep in perspective is the p-value of 0.041. That is inside the conventional 0.05 threshold but not far inside, and in a trial this small a handful of patients moving the other way could have changed it. Everything pointed the same direction, though: the patient-reported measures, the doctor-reported measures and the biological marker all favoured the drug, and serious side effects were less common on the drug than on placebo.
The numbers. Randomised, double-blind, placebo-controlled, 2:1 drug to placebo, 60-week double-blind period, 13 sites in 8 countries, 50 mg designated the pivotal dose cohort. Primary endpoint, percent change from baseline in gait speed on the 10-Meter Walk Test at week 61 in patients aged 5 and over: least-squares mean difference +33.3%, p=0.0412. No confidence intervals disclosed. Serious treatment-emergent adverse events 37.5% on drug against 47.1% pooled control. The number of patients actually analysed for the primary endpoint has not been publicly disclosed. Source
The results in the youngest children, aged two to four, and the blood marker showing the target protein falling are both encouraging and both point the same way as the main result. They are labelled nominal, which is a specific statistical term meaning they were not adjusted for the fact that many measures were tested at once. When you test enough things, some will look significant by chance. So these support the main finding rather than independently confirming it, and that distinction is one the FDA will apply.
The numbers. GMFM-88 in children aged 2 to 4 at week 61: +22.9 points, p=0.034, nominal. Plasma GFAP at week 61: -33.6% against control, p=0.003, nominal and exploratory. Patient-reported Most Bothersome Symptom: 32% much better on drug against 0% on control. Clinician Global Impression of Change improved or unchanged in 75% against 47%. Secondary endpoints reported as raw percentages with no p-values or confidence intervals disclosed. Source
Nobody is disputing that the trial hit its target. The open question is narrower and more technical. The headline result was measured in patients aged five and over, but the trial enrolled children as young as two, and the results in the youngest group rest on a supporting measure that was not adjusted for multiple testing. Whether that age-restricted analysis was planned in advance, and whether one small trial is enough on its own, are matters for the FDA's review, and it has published nothing. A second point worth knowing: the full results have never been peer-reviewed or published in a journal, so the confidence intervals, the per-group patient numbers and the complete safety tables are not in the public domain. Everything above comes from company announcements and a conference presentation. [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 |
|---|---|---|---|
| 2026-06-25 | Recordati licensed rights outside the US | +2.4% | $76.52 to $78.34 |
| 2026-04-21 | Full pivotal data presented at AAN | -0.1% | $74.87 to $74.78 |
| 2026-03-23 | NDA accepted with Priority Review, PDUFA date set | -0.3% | $70.99 to $70.79 |
| 2025-12-02 | Breakthrough Therapy designation (release also covered olezarsen) | -0.8% | $81.99 to $81.31 |
| 2025-09-22 | Pivotal topline announced | +0.6% | $61.01 to $61.36 |
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 22, 2026. The next catalyst for Ionis Pharmaceuticals Inc. is Zilganersen (ION373) (PDUFA). That date is a confirmed date. 4 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, 4 in our archive: 3 approval(s) and 1 Complete Response Letter(s). The most recent was on June 24, 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 9 decisions: +4.3% from T-120 to the eve, +25.1% 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.