Satralizumab is a recombinant humanized monoclonal antibody designed to target the interleukin-6 receptor (IL-6R). It is a biological active pharmaceutical ingredient belonging to the immunoglobulin G2 (IgG2) antibody class. Satralizumab is marketed as Enspryng and is also known by development names including SA237, RO5333787 and RG-6168. FDA identifies satralizumab-mwge as a recombinant humanized anti-human IL-6 receptor monoclonal antibody produced using recombinant DNA technology in Chinese hamster ovary (CHO) cells.
Unlike conventional small-molecule APIs, Satralizumab API is a complex recombinant protein requiring biologics-specific manufacturing and analytical controls. FDA describes the antibody as being based on a human IgG2 framework, with two heavy chains of 443 amino acids each and two light chains of 214 amino acids each. The labeled molecular weight is approximately 143 kDa.
The FDA Global Substance Registration System assigns Satralizumab the UNII YB18NF020M and identifies 1535963-91-7 as a substance synonym/CAS identifier. PubChem and the Australian TGA product information independently identify the same CAS number.
Satralizumab is an IL-6 receptor antagonist used for neuromyelitis optica spectrum disorder (NMOSD). In the United States, satralizumab-mwge is approved for adult patients with AQP4 antibody-positive NMOSD. EMA's current product information states that satralizumab is indicated as monotherapy or with immunosuppressive therapy for AQP4-IgG-seropositive NMOSD in adults and adolescents aged 12 years and older.
NMOSD is a rare inflammatory disorder that can primarily affect the optic nerves and spinal cord. Satralizumab is designed to reduce IL-6-mediated inflammatory signaling and thereby help reduce disease activity and relapses in appropriate patients.
Satralizumab binds to both soluble and membrane-bound IL-6 receptors, inhibiting IL-6-mediated signaling. IL-6 is an important cytokine involved in inflammatory and immune responses. By blocking IL-6 receptor signaling, satralizumab reduces the downstream inflammatory activity associated with the disease. FDA describes the binding of satralizumab to the IL-6 receptor as pH-sensitive.
Satralizumab is manufactured through recombinant DNA technology using Chinese hamster ovary (CHO) cell culture. Production of a monoclonal-antibody API requires controlled cell culture, harvest, purification, viral safety controls and extensive characterization of critical quality attributes. FDA confirms CHO-cell production, while regulatory reviews describe a quality-control strategy covering identity, purity, impurities, potency and safety.
Quality evaluation of Satralizumab drug substance is fundamentally different from testing a conventional chemical API. Regulatory documentation describes control of appearance, pH, identity, protein content, purity/impurities, potency and safety attributes. Satralizumab potency is evaluated using a cell-based assay designed to measure its ability to block binding of human IL-6 to the human IL-6 receptor.
Additional biologics characterization can include aggregate and fragment assessment, charge-variant analysis, glycosylation characterization, host-cell protein, residual host-cell DNA, bioburden/endotoxin and other process-related impurity controls. EMA confirms that the active-substance specification follows an ICH Q6B-oriented quality-attribute approach.
Satralizumab is a glycoprotein with an approximate molecular weight of 143 kDa. The commercial finished product is supplied as a sterile, clear, colorless to slightly yellow solution with an approximate pH of 6.0. Each prefilled syringe contains 120 mg/mL satralizumab-mwge. These latter values describe the finished drug product and should not be incorrectly presented as universal drug-substance specifications.
The finished Satralizumab product is supplied in a single-dose prefilled syringe and is stored refrigerated at 2–8°C, protected from light and not frozen. API/drug-substance storage conditions should instead be based on the applicable validated drug-substance stability program and manufacturer specification.
A pharmaceutical-grade Satralizumab biological API program may require:
A qualified Satralizumab API manufacturer requires appropriate biologics manufacturing infrastructure, controlled CHO-cell production, validated purification processes and sophisticated analytical characterization. Consistent control of identity, protein content, purity, potency, aggregates, process-related impurities and biological activity is essential for a recombinant monoclonal antibody such as Satralizumab. Regulatory assessments have found the Satralizumab active-substance control strategy acceptable and reported consistent commercial-process batch results.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |