Shares of Merus NV (MRUS), a clinical-stage oncology company, plummeted by 5.49% on November 5, 2024, following the announcement that the U.S. Food and Drug Administration (FDA) has extended the review period for the company's investigational drug zenocutuzumab.

The FDA has set a new target action date of February 4, 2025, for the Biologics License Application (BLA) of zenocutuzumab, which is currently under priority review for the treatment of certain patients with non-small cell lung and pancreatic cancer expressing the NRG1 fusion. The extension was granted to provide the agency with additional time to review supplemental information submitted by Merus in response to a request related to chemistry, manufacturing, and controls (CMC).

Merus stated that the FDA did not request any additional clinical data, and the company believes that obtaining a commercialization partnership agreement is an important step in bringing zenocutuzumab to patients with NRG1+ cancer, if approved. However, the delay in the regulatory review process has raised concerns among investors, leading to the significant decline in the company's stock price.