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FDA Tells Omeros It Will Not Approve Therapy to Treat Side Effect of Stem Cell Transplants

October 18, 2021

The U.S. Food and Drug Administration told Omeros it would not approve the company’s application for approval of narsoplimab as a treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy without additional data.

Shares in Omeros fell more than 25 percent in morning trading to a 52-week low of $5.45.

Omeros said the FDA expressed difficulty in estimating the treatment effect of narsoplimab in hematopoietic stem cell transplant-associated thrombotic microangiopathy (HSCT-TMA) and said that additional information will be needed to support regulatory approval. There were no chemistry, manufacturing and controls, safety, or non-clinical issues precluding approval raised in the complete response letter from the agency.

The company said it plans to request a meeting as soon as possible with FDA to discuss the complete response letter and the path forward for the approval of narsoplimab.

Hematopoietic stem cell transplant-associated thrombotic microangiopathy (HSCT-TMA) is a significant and often lethal complication of stem cell transplantation. The condition is a systemic, multifactorial disorder caused by endothelial cell damage induced by conditioning regimens, immunosuppressant therapies, infection, graft-versus-host disease, and other factors associated with stem cell transplantation. Endothelial damage, which activates the lectin pathway of complement, plays a central role in the development of HSCT-TMA.

Narsoplimab is an investigational human monoclonal antibody targeting mannan-binding lectin-associated serine protease-2 (MASP-2), a novel pro-inflammatory protein target and the effector enzyme of the lectin pathway of complement. The company said inhibition of MASP-2 does not appear to interfere with the antibody-dependent classical complement activation pathway, which is a critical component of the acquired immune response to infection.

Narsoplimab is the first drug candidate submitted to FDA for approval in HSCT-TMA. It has Breakthrough Therapy and Orphan designations in both HSCT-TMA and IgA nephropathy.

Author: Rare Daily Staff

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