Regeneron Pharmaceuticals (REGN) Plunges 19.89% on Failed COPD Trial

Regeneron Pharmaceuticals (REGN) experienced a significant decline, with its share price dropping 19.89% intraday, marking its lowest level since May 2021.

The strategy of buying REGN shares after they reached a recent low and holding for 1 week yielded moderate returns over the past 5 years, with a 4.56% annualized return and a 22.13% total return as of the latest data point in May 2025. However, the volatility was significant, with a maximum drawdown of 38.24% during the period, indicating that this strategy is risky and may not be suitable for all investors.

The primary reason behind the decline in Regeneron's stock price is the failure of the Phase 3 trial for its COPD treatment, itepekimab, which was developed in collaboration with Sanofi. The disappointing outcome has affected investor sentiment, leading to a sharp decrease in the company's stock value. Analysts had anticipated positive results from the trial, making the failure particularly impactful.

This setback comes at a critical time for Regeneron, as the company has been focusing on expanding its portfolio of respiratory treatments. The failure of itepekimab not only halts progress in this area but also raises questions about the efficacy of Regeneron's pipeline in addressing chronic respiratory conditions. Investors are now closely monitoring the company's next steps and its ability to recover from this setback.

Despite this challenge, Regeneron remains a key player in the biopharmaceutical industry, with a strong track record of innovation and a robust pipeline of other potential treatments. The company's leadership has expressed confidence in its ability to overcome this hurdle and continue delivering value to shareholders. However, the immediate impact on the stock price underscores the high stakes involved in clinical trials and the potential for significant market reactions to trial outcomes.