Sarilumab is a fully human monoclonal antibody of the IgG1 subclass that targets the interleukin-6 receptor (IL-6R). It is a recombinant biological therapeutic produced using Chinese hamster ovary (CHO) cell technology. Sarilumab binds both soluble and membrane-bound IL-6 receptors and inhibits IL-6-mediated signaling.
Sarilumab API is a biological active pharmaceutical ingredient rather than a conventional small-molecule API. FDA identifies sarilumab as a recombinant human monoclonal antibody with an approximate molecular weight of 150 kDa. EMA reports a relative molecular mass of approximately 143.9 kDa without N-linked glycosylation, while FDA characterization reports an expected glycosylated molecular mass of approximately 149.6 kDa.
The API is produced through recombinant DNA technology in CHO cell suspension culture. It consists of two disulfide-linked human heavy chains, each linked to a human kappa light chain. Each heavy chain contains an N-linked glycosylation site at Asn296.
Sarilumab has the CAS number 1189541-98-7 and is classified by FDA GSRS as a protein substance. FDA GSRS provides an estimated average molecular weight of approximately 144,000 Da and an estimated molecular formula of C6388H9868N1718O1998S44. Because these values are explicitly identified by FDA as estimated, they should not be treated as a fixed molecular specification for the commercial glycoprotein.
Sarilumab is used as an interleukin-6 receptor antagonist in inflammatory and autoimmune diseases. Current European authorization includes treatment of moderately to severely active rheumatoid arthritis, polymyalgia rheumatica in adults with inadequate response or relapse during corticosteroid tapering, and active polyarticular juvenile idiopathic arthritis in patients aged 2 years and older who have responded inadequately to previous conventional synthetic DMARD therapy.
Sarilumab specifically binds to both soluble and membrane-bound IL-6 receptors. By blocking IL-6 receptor signaling, it inhibits downstream IL-6-mediated inflammatory pathways. This mechanism forms the basis of its therapeutic activity in inflammatory disorders.
As a monoclonal antibody API, Sarilumab requires a biologics-focused quality-control strategy rather than the conventional testing approach used for small molecules. Relevant quality attributes include identity, purity, potency, glycosylation, aggregation, charge variants, protein concentration, host-cell proteins, host-cell DNA, residual process-related impurities and microbiological quality.
FDA characterization identifies multiple sarilumab isoforms associated with post-translational modifications and glycosylation. These molecular variants were separated and characterized, with the characterized isoforms retaining biological activity.
Sarilumab is manufactured using recombinant DNA technology in Chinese hamster ovary (CHO) cell suspension culture. The manufacturing process for a monoclonal antibody requires controlled cell culture, harvest, purification, viral safety controls, formulation and aseptic processing.
Sarilumab is a glycosylated IgG1 monoclonal antibody. FDA describes the finished injectable product as a sterile, colorless to pale-yellow solution with an approximate pH of 6.0. The commercial product is formulated for subcutaneous administration.
Sarilumab API and bulk biological material should be handled using validated storage and transport conditions appropriate for monoclonal antibodies. Commercial finished product labeling specifies controlled refrigerated storage and protection from freezing and light; bulk API requirements should follow validated manufacturer stability data and the applicable regulatory specification.
Typical documentation for Sarilumab biological API may include:
A qualified Sarilumab API manufacturer should have appropriate biologics manufacturing capabilities, validated cell-culture and purification processes, robust analytical characterization and strong control of critical quality attributes. Because Sarilumab is a recombinant monoclonal antibody, manufacturing consistency, biological activity, molecular integrity and impurity control are particularly important.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 0.5% |
| Residue on Ignition | NMT 0.1% |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |
| Water Content | NMT 0.5% |