Shares of Regeneron Pharmaceuticals Inc (NASDAQ:REGN) sank nearly 19% on Friday after the company’s experimental COPD drug, developed with partner Sanofi SA (ADR) (NYSE:SNY), posted mixed results in two Phase 3 trials—casting doubt on its regulatory path and delaying hopes for a major new revenue stream.
The drug, itepekimab, reduced moderate or severe flare-ups by 27% compared to placebo over 52 weeks in the AERIFY-1 study, which enrolled 1,127 former smokers with chronic obstructive pulmonary disease (COPD).
However, a second late-stage trial, AERIFY-2, failed to meet its primary endpoint.
Sanofi and Regeneron said the trials were affected by lower-than-expected exacerbation rates, likely linked to enrollment during the COVID-19 pandemic, which reduced exposure to respiratory infections. Both companies are reviewing the data and discussing next steps with regulators.
The outcome clouds the outlook for a drug some had projected could reach peak sales of $5 billion.
US-listed shares of Sanofi were down around 5.5% by noon Friday.