FDA Issues Complete Response Letter to Omeros for Narsoplimab

Narsoplimab was under review at the FDA to treat a complication of stem cell transplants.

The FDA has issued a complete response letter to Omeros about its biologics license application (BLA) for narsoplimab in the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (HSCT-TMA).

Thrombotic microangiopathy is characterized by the destruction of red blood cells, low platelets, and organ damage due to the formation of microscopic blood clots in capillaries and small arteries. It can lead to worsen outcomes in patients who have undergone stem cell transplants. The condition occurs in both autologous and allogeneic transplants but is more common in the allogeneic population, and recent reports suggest it occurs in about 40% of allogeneic transplants.

In the CRL, FDA indicated it was difficult to assess the treatment effect of narsoplimab in HSCT-TMA. Regulatory officials are requesting additional information to support approval, including data on chemistry, manufacturing and controls (CMC), safety, or nonclinical issues precluding approval raised in the CRL.

Narsoplimab is a human monoclonal antibody targeting mannan-binding lectin-associated serine protease-2 (MASP-2), an enzyme of the lectin pathway of complement, which is part of the immune system. Narsoplimab is the first drug candidate submitted to FDA for approval in for this indication. It has breakthrough therapy and orphan designations in both HSCT-TMA and immunoglobulin A (IgA) nephropathy or chronic kidney disease. The company also has a phase development program in IgA.

Omeros plans to request a Type A meeting, which is a formal meeting between sponsors and regulators for stalled product developments.

Omeros’ application had been accepted in January 2021 for the thrombotic microangiopathy indication.