Daily close, T-120 (12/5/24) through T+5. Run-up high $40.39 on 3/19/25, low $32.08 on 1/17/25 (T-120 to T-1). FDA decision 5/22/25. Historical price action, not a forecast.
Positioning before the decision
On May 8, 2025, 14 days before the decision date, at-the-money options priced a move of ±5.7% through May 23, 2025 (the first listed expiry after the decision; ATM implied volatility 35%). The stock closed +1.0% at the first close across the decision and +3.8% 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 Nucala (mepolizumab) on May 22, 2025. The primary source is linked on this page.
What was Nucala (mepolizumab) under FDA review for?
The application covered Chronic obstructive pulmonary disease (COPD). The FDA approved the application on May 22, 2025.
How did GSK stock react to the FDA decision?
On the decision day GSK moved +1.0%. That is the recorded reaction to this specific event -- historical measurement, not a prediction, and not investment advice.