Daily close, T-120 (3/6/25) through T+5. Run-up high $43.78 on 8/15/25, low $25.51 on 4/14/25 (T-120 to T-1). FDA decision 8/21/25. Historical price action, not a forecast.
Positioning before the decision
On Aug 7, 2025, 14 days before the decision date, at-the-money options priced a move of ±16.1% through Sep 19, 2025 (the first listed expiry after the decision; ATM implied volatility 59%). The stock closed +1.0% at the first close across the decision and -0.1% five trading days on. A straddle priced weeks out covers ordinary movement plus the event, so this is the move the options market priced through that expiry, not the event-implied move alone. How this compares across 1,000+ decisions.
Yes. The FDA approved the application for DAWNZERA (Donidalorsen) on August 21, 2025. The primary source is linked on this page.
What was DAWNZERA (Donidalorsen) under FDA review for?
The application covered Hereditary Angioedema (HAE). The FDA approved the application on August 21, 2025.
How did IONS stock react to the FDA decision?
On the decision day IONS moved +1.0%. That is the recorded reaction to this specific event -- historical measurement, not a prediction, and not investment advice.