On October 1, 2021, Omeros announced that the U.S. Food and Drug Administration (“FDA”) had identified deficiencies with the Company’s Biologics License Application for its drug candidate narsoplimab in the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (HSCT-TMA), which “preclude discussion of labeling and post-marketing requirements/commitments at this time.” The Company further advised that the “FDA did not provide specific details of the deficiencies in its notification[,]” and that the “the company does not currently expect any resolution to occur by the October 17, 2021 target action date under the Prescription Drug User Fee Act (PDUFA).”

On this news, Omeros’s stock price fell $5.25 per share, or 38.07%, to close at $8.54 per share on October 1, 2021.