The regulatory setback occurred on June 26, 2026, when the Committee for Medicinal Products for Human Use (CHMP) rejected the marketing authorization application for narsoplimab, intended to treat hematopoietic stem cell transplant-associated thrombotic microangiopathy. Despite Omeros presenting its case alongside international experts, the committee maintained its stance, prompting a sell-off that saw the company's share price tumble by $2.05 to close at $8.67.

Pomerantz LLP is currently examining whether Omeros or its leadership engaged in unlawful business practices or misled shareholders regarding the drug's prospects. Investors affected by this decline are being directed to contact Danielle Peyton to discuss potential participation in class action litigation.