Narsoplimab (OMS721) is our lead antibody targeting MASP-2, the effector enzyme of the lectin pathway of complement.

Narsoplimab (OMS721)

Narsoplimab is a human monoclonal antibody targeting mannan-binding lectin-associated serine protease-2 (MASP-2), the effector enzyme of the lectin pathway of the complement system. The lectin pathway is one of the principal pathways of complement and is activated primarily by tissue damage and microbial infection. Importantly, inhibition of MASP-2 does not appear to interfere with the classical complement pathway, a critical component of the acquired immune response to infection. This novel, proprietary drug is designed to prevent complement-mediated inflammation and endothelial damage while leaving intact the respective functions of the other pathways of innate immunity.

Hematopoietic Stem Cell Transplant-Associated Thrombotic Microangiopathy (TA-TMA)

  • Narsoplimab has been granted FDA Breakthrough Therapy designation in patients who have high-risk TA-TMA, as well as Orphan Drug designation for the prevention of complement-mediated TMAs and for the treatment of TA-TMA. In the European Union, narsoplimab has been designated an Orphan Medicinal Product for treatment in hematopoietic stem cell transplantation.
  • The 61% response rate and 68% 100-day survival seen with narsoplimab-treated TA-TMA patients in the pivotal clinical trial represent an approximately three-fold improvement when compared to an untreated age- and disease status-matched cohort from a systematic literature review.1,2
  • Omeros is pursuing approval in the US and in Europe for narsoplimab to treat TA-TMA.

Narsoplimab OMS721 MASP-2 antibody inhibitor, breakthrough therapy and orphan drug for HSCT-TMA
Narsoplimab OMS721 MASP-2 antibody inhibitor, breakthrough therapy and orphan drug for IgA nephropathy

IgA Nephropathy

  • Narsoplimab has also received FDA Breakthrough Therapy and Orphan Drug designations for the treatment of IgA nephropathy and Orphan Medicinal Product designation for IgA nephropathy in the European Union.
  • In a Phase 2 clinical trial of patients with severe IgA nephropathy, narsoplimab-treated patients received a median of one course of 12 weekly doses per year and showed a median proteinuria reduction of 64.4% and a sustained proteinuria reduction of 38% from baseline after an unprecedented nearly 3-year follow-up period. Twenty-five percent of patients demonstrated improved glomerular filtration rates – the true measure of kidney function – with stabilization of eGFR seen in others.3 This is the first time that sustained stabilization and improvement of glomerular filtration rates through long-term follow-up has been reported for any novel therapeutic in development for IgA nephropathy. The magnitude of median proteinuria reduction seen with narsoplimab is predicted to delay progression to renal dialysis by 41.6 years compared to standard of care.4
  • With FDA’s only Breakthrough Therapy designation awarded for this disorder, as well as Orphan Drug designations from both FDA and the European Medicines Agency, narsoplimab is advancing through a Phase 3 clinical program to treat IgA nephropathy.

Atypical Hemolytic Uremic Syndrome (aHUS)

  • Narsoplimab has received FDA Fast Track designation for the treatment of aHUS. Improvements in markers were observed in a Phase 2 clinical trial, and a Phase 3 clinical program is underway.

Narsoplimab OMS721 MASP-2 antibody inhibitor, fast-track designation for aHUS
View our pipeline to learn about ongoing narsoplimab clinical studies

1Khaled SK, Claes K, Goh YT, et al. Narsoplimab, a mannan-binding lectin-associated protease-2 inhibitor, for the treatment of adult hematopoietic stem-cell transplantation–associated thrombotic microangiopathy. J Clin Oncol. 2022; 40(22):2447-2457.
2Whitaker S, Nangia N, Ng E, Sotolongo S, Pullman W. Systematic literature review of the natural history of hematopoietic stem cell transplant-associated thrombotic microangiopathy in adults. Presented at: 48th Annual Meeting of the European Society for Blood and Marrow Transplantation; March 19-23, 2022.
3Barratt J, Carroll K, Lafayette R. Long-term Phase 2 efficacy of the MASP-2 inhibitor narsoplimab for treatment of severe IgA nephropathy. Kidney Int Rep. 2022;7(2):S45.
4Carroll K, Conley L, Mercer A, Saleem M, Barratt J. Estimating Delay in Time to ESKD for Treatment Effects on Proteinuria in IgA Nephropathy and FSGS. Presented at: European Renal Association-European Dialysis and Transplant Association (ERA-EDTA); June 5-8, 2021.