Narsoplimab is a fully human recombinant monoclonal antibody that selectively targets mannan-binding lectin-associated serine protease 2 (MASP-2), the key effector enzyme of the lectin pathway of the complement system. It is also known by its development code OMS721 and its nonproprietary name narsoplimab-wuug. Narsoplimab is an immunoglobulin G4 (IgG4) monoclonal antibody produced using recombinant biotechnology.
Narsoplimab differs fundamentally from conventional small-molecule pharmaceutical APIs because it is a large, structurally complex biological molecule. Its characterization therefore requires biologics-specific analytical methods covering identity, purity, aggregation, charge heterogeneity, glycosylation, potency and other critical quality attributes.
Narsoplimab is a specialized biological active pharmaceutical ingredient relevant to therapeutic antibody development, complement-pathway research and pharmaceutical manufacturing.
The molecule selectively inhibits MASP-2 and therefore acts on the lectin pathway of complement activation while preserving the classical and alternative complement pathways.
Important quality attributes for narsoplimab include:
Product Name: Narsoplimab
Development Code: OMS721
US Nonproprietary Name: Narsoplimab-wuug
Brand Name: YARTEMLEA
CAS Number: 2108782-45-0
Molecule Type: Fully Human Recombinant Monoclonal Antibody
Antibody Isotype: Human IgG4
Target: Mannan-binding lectin-associated serine protease 2 (MASP-2)
Target Pathway: Lectin Pathway of Complement
Host Cell: Chinese Hamster Ovary (CHO) cells
Approximate Molecular Weight: 143 kDa
The NIH GSRS database gives an estimated molecular weight of approximately 143,000 Da, while technical antibody databases report approximately 143.1 kDa.
Narsoplimab selectively binds to MASP-2, thereby inhibiting activation of the lectin pathway of the complement system. MASP-2 is the effector serine protease responsible for downstream activation of the lectin pathway.
Its pharmacological activity includes:
The selective MASP-2 mechanism allows narsoplimab to inhibit the lectin pathway without directly blocking the classical and alternative complement pathways.
Narsoplimab-wuug is marketed in the United States as YARTEMLEA. According to the manufacturer's current information, the FDA approved YARTEMLEA in December 2025. It is indicated for the treatment of adult and pediatric patients 2 years of age and older with hematopoietic stem cell transplant-associated thrombotic microangiopathy (HSCT-TMA).
This is an important update compared with older descriptions of narsoplimab as an investigational therapy.
HSCT-TMA is a serious complication associated with hematopoietic stem cell transplantation and involves endothelial injury, complement activation and microvascular thrombosis.
Narsoplimab's selective inhibition of MASP-2 is intended to interrupt lectin-pathway complement activation associated with the disease process. Clinical research has specifically investigated narsoplimab in this setting.
Narsoplimab API is relevant to:
As a recombinant IgG4 monoclonal antibody, narsoplimab has structural characteristics typical of therapeutic antibodies.
Relevant characterization parameters may include:
Narsoplimab is produced through recombinant cell-culture technology rather than conventional organic chemical synthesis.
A representative monoclonal-antibody manufacturing workflow may include:
The actual commercial manufacturing process and acceptance criteria are controlled by proprietary validated manufacturing procedures.
Narsoplimab requires a biologics-focused analytical control strategy.
Typical testing may include:
For narsoplimab, biological potency is a critical quality attribute because the therapeutic activity depends on functional inhibition of MASP-2.
A suitable potency assay should evaluate the ability of narsoplimab to inhibit the relevant MASP-2/lectin-pathway activity using an appropriately validated biological method.
A conventional HPLC assay alone cannot fully establish the functional quality of a monoclonal antibody.
Narsoplimab has an approximate molecular weight of 143 kDa. NIH GSRS reports an estimated calculated molecular weight of approximately 143,000 Da, while commercial research references report 143.1 kDa.
Because monoclonal antibodies are glycoproteins and can exhibit molecular heterogeneity, molecular weight should be treated as an approximate characteristic, rather than as an absolute small-molecule molecular weight.
The CAS Registry Number reported for narsoplimab is 2108782-45-0. This identifier is also reported in technical antibody databases.
Narsoplimab should be stored according to the approved product specification and validated stability conditions.
For research-grade narsoplimab preparations, storage conditions can vary by formulation and supplier. One technical research preparation specifies storage at −80°C, while another recommends following the lot-specific Certificate of Analysis.
Therefore, a commercial pharmaceutical page should avoid publishing a generic storage temperature unless it corresponds to the exact drug-substance or drug-product specification.
Narsoplimab is a biological therapeutic and should be manufactured under applicable biologics GMP requirements.
Quality control should address the critical quality attributes relevant to monoclonal antibodies, including structural integrity, purity, potency, aggregation, glycosylation and process-related impurities.
Narsoplimab is relevant to research involving:
| Parameter | Specification |
|---|---|
| Appearance | White crystalline powder or crystals |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Residue on Ignition | NMT 0.5% |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |
| Water Content | NMT 1.0% |