Biogen's Stock Dips 0.91% Amid 90% Volume Surge, Ranks 395th in Trading Activity

Biogen (BIIB) closed on September 19, 2025, , despite a notable surge in trading volume. , .

Recent developments highlight regulatory scrutiny as a key factor. A U.S. Senate panel is reviewing Biogen’s Alzheimer’s drug , questioning its efficacy and pricing strategy. While the FDA approved the drug in 2021, ongoing debates about its clinical value have persisted, creating uncertainty for investors.

Analysts note that Biogen’s financial outlook remains tied to its pipeline advancements. Positive Phase 3 trial results for a Parkinson’s disease candidate earlier this year provided temporary optimism. However, delays in regulatory timelines and mixed feedback from advisory committees have dampened momentum. The company’s reliance on high-margin biologics also exposes it to biosimilar competition in the coming years.

To run this back-test precisely we need to clarify a few practical details: 1. Universe: Which exchange / country should we pull the “top-500-by-volume” list from each day (e.g., all primary-listed US stocks, only S&P 500 constituents, all NYSE + NASDAQ, etc.)? 2. Survivorship & corporate actions: Should we use today’s constituent list (which introduces survivorship bias) or the historical membership on each date? Adjust for splits / dividends (total-return series)? 3. Transaction assumptions: Any round-trip cost (commission/slippage) per trade? Portfolio sizing: equal-weight each of the 500 names every day, or volume-weighted, or some other scheme? Cash drag (if any) on non-invested capital between close and next-day open? 4. Benchmark / performance metrics: Show cumulative return & max drawdown only, or also metrics such as Sharpe, turnover, etc.? 5. Output format: Is an interactive chart sufficient, or do you also need the underlying daily P&L series in a CSV? Once these points are settled I can pull the required data and run the automated back-test from 2022-01-03 (first trading day in 2022) to the present.