Regeneron market risk — Regeneron Pharmaceuticals (REGN) does not appear to be a major source of added market risk for a diversified portfolio, but its own price swings are far larger than the broad index’s. That is the central finding from a review of the stock’s daily behavior between the close on October 30, 2025, and November 2, 2026. Over that stretch, Regeneron gained 19.0% from October 26 to November 2, 2026, even as the S&P 500 slipped 1.8%, a divergence that highlights how loosely the shares track the market.
A Low Sensitivity to Index Moves
Measured against the S&P 500, Regeneron moved just 0.32% for every 1% change in the index over the 12-month period. On days when the index rose, averaging a 0.633% gain, a $10,000 position in Regeneron added roughly $46. On down days, when the index fell an average of 0.606%, the same holding lost only about $14. In other words, the stock captured about 73.1% as much of the index’s up-day gains while giving back far less on down days.
That asymmetry is reflected in a correlation of 0.12 between Regeneron’s daily moves and the index’s, where 1.0 would mean perfect alignment. For investors already exposed to broad market risk, adding Regeneron contributes relatively little additional market-driven volatility.
Volatility That Runs on Its Own Track
Yet the stock is anything but calm. Its annualized volatility over the same period was 33.6%, compared with 12.8% for the S&P 500. The disconnect showed up sharply in April 2026, when the index climbed 10.4% while Regeneron fell 8.5%. Such episodes suggest that company-specific news, not macro sentiment, drives most of the stock’s day-to-day price action.
Concentrated Revenue, Concentrated Risk
The source of that independent risk is not hard to find. Regeneron’s results lean heavily on a small number of products and regulatory milestones. Dupixent, which Regeneron shares with Sanofi, generated collaboration revenue of $2.7 billion in fiscal Q3 2026, an all-time high, according to management on the October 30, 2026 call.
EYLEA, the company’s eye-treatment franchise, is moving in the opposite direction. Revenue fell 42.4% in fiscal 2025, and management noted growing competition from additional biosimilar launches—cheaper copies of the drug. Management nonetheless described the eye business as remaining in a strong position despite that pressure.
Regulatory decisions add another layer of binary risk. Management expects an FDA ruling in November on cemdisiran for generalized myasthenia gravis, and a lymphoma treatment is under review with a February 2027 target action date. With so much riding on a handful of drugs and approvals, wide price swings are likely to persist.
Return per Unit of Risk Lags the Market
Over the five years through November 2, 2026, Regeneron delivered an annual return of 8.3%, versus 11.7% for the S&P 500. Its annual volatility over that span was 31.6%, compared with 17.0% for the index. Dividing return by volatility gives a rough measure of compensation per unit of swing: 0.263 for Regeneron and 0.688 for the index. The stock’s larger price movements have not been rewarded as well as the market’s.
What This Means for a Portfolio
If the past year’s pattern holds, Regeneron should add less than the market on the next up day and take less on the next down day. That makes it a modest contributor to the market risk an investor already carries. The risk it does bring is concentrated: Dupixent’s profitability, EYLEA’s competitive erosion and FDA decisions. For investors who already own other drugmakers with similar dependence on a few products and regulators, Regeneron may deepen that same bet rather than diversify it.