Omeros Corporation (NASDAQ:OMER) shares rose 3.1% on Tuesday following the company's announcement that it has finished initial commercial shipments of YARTEMLEA (narsoplimab-wuug) to distributors, with transplant centers initiating orders immediately.
The company reported that both adult and pediatric patients suffering from stem cell transplant-associated thrombotic microangiopathy - TA-TMA - are now receiving YARTEMLEA in clinical settings. Treatment is being delivered in hospitals as well as outpatient facilities, and includes patients who recently failed prior off-label C5-inhibitor regimens, according to the company.
YARTEMLEA holds the distinction of being the first and only therapy approved by the U.S. Food and Drug Administration specifically for TA-TMA. The approval was granted on December 23, 2025, for use in adults and children two years of age and older.
The drug's mechanism targets MASP-2, the effector enzyme of the lectin pathway of the complement system. By selectively inhibiting MASP-2, YARTEMLEA blocks activation of the lectin pathway while preserving the classical and alternative complement functions that play a role in defending against infection.
TA-TMA can develop after both autologous and allogeneic hematopoietic stem cell transplantation, with a higher observed prevalence following allogeneic transplants. The company noted that about 30,000 allogeneic transplants are performed each year in the United States and Europe, and cited recent studies estimating that TA-TMA develops in up to 56% of allogeneic transplant recipients.
Omeros also disclosed that a marketing authorization application for YARTEMLEA is under review by the European Medicines Agency, with a regulatory decision expected in mid-2026.
Context and immediate developments
- Initial commercial shipments to distributors have been completed and transplant centers have begun placing orders.
- Administration is underway for both adult and pediatric patients, including cases that did not respond to prior off-label C5-inhibitor treatment.
- Regulatory progress continues in Europe with an EMA decision anticipated in mid-2026.
This represents the transition from regulatory approval to early commercial availability for a therapy addressing a potentially fatal complication of stem cell transplantation. Details on the scale of the rollout beyond the initial shipments were not provided in the announcement.