The Food and Drug Administration (FDA) has accepted for filing and granted Priority Review to narsoplimab (Omeros Corporation) for the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (HSCT-TMA).

Narsoplimab is a human monoclonal antibody that specifically targets mannan-binding lectin-associated serine protease-2. The investigational drug is designed to prevent complement-mediated inflammation and endothelial damage.

The BLA submission is supported by data from a single-arm, open-label phase 2 trial that evaluated the efficacy and safety of narsoplimab in 28 adult HSCT-TMA patients at high risk with a large majority having multiple comorbidities at baseline (eg, graft-versus-host-disease, significant infections, multi-organ dysfunction). Patients received narsoplimab intravenously once weekly for up to 8 weeks with an extended follow-up period. 

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The primary end point was complete response rate (CRR) assessed by clinical improvement in thrombotic microangiopathy markers (platelet count and lactate dehydrogenase) and in organ function or freedom from transfusion. Results showed a CRR of 61% (95% CI, 40.6-78.5; P <.0001) in the full analysis set, which included patients receiving at least 1 dose of narsoplimab. In the per-protocol population, which included patients receiving the protocol-specified narsoplimab treatment for at least 4 weeks, CRR was 74% (95% CI, 51.6-89.8; P <.0001).

A Prescription Drug User Fee Act (PDUFA) target date of July 17, 2021 has been set for this application. The Company is also investigating narsoplimab for the treatment of immunoglobulin A nephropathy and atypical hemolytic uremic syndrome.


  1. Biologics License Application for narsoplimab in HSCT-TMA accepted for Priority Review by U.S. FDA. [press release]. Seattle, WA: Omeros Corporation; January 19, 2021. 
  2. Omeros reports final efficacy and safety data from the narsoplimab pivotal trial in HSCT-TMA. [press release]. Seattle, WA: Omeros Corporation; October 22, 2020.

This article originally appeared on MPR