Ocrelizumab is a recombinant humanized monoclonal antibody (mAb) and a CD20-directed B-cell-depleting therapeutic used in the treatment of multiple sclerosis. It is an IgG1 antibody designed to selectively recognize CD20-expressing B cells. Ocrelizumab is marketed as Ocrevus and is administered as a parenteral biological medicinal product. The substance has CAS Registry Number 637334-45-3 and FDA UNII A10SJL62JY.
Because ocrelizumab is a large glycosylated protein rather than a conventional low-molecular-weight chemical API, its quality characterization relies on protein identity, purity, potency, aggregation, charge variants, glycosylation, host-cell impurities, residual process-related impurities and microbiological quality rather than conventional small-molecule parameters. Public regulatory records identify ocrelizumab as a biological/biotechnological active substance.
Ocrelizumab selectively binds to CD20 expressed on pre-B cells, mature B cells and memory B cells. Following binding to the CD20 antigen, the antibody promotes selective B-cell depletion through several mechanisms, including antibody-dependent cellular phagocytosis (ADCP), antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC) and apoptosis. Lymphoid stem cells and plasma cells do not express CD20, allowing pre-existing humoral immunity and the capacity for B-cell reconstitution to be preserved.
Ocrelizumab is used for the treatment of adult patients with relapsing forms of multiple sclerosis (RMS) with active disease and for appropriate adults with primary progressive multiple sclerosis (PPMS). The EMA identifies multiple sclerosis as its therapeutic area and classifies ocrelizumab under immunosuppressants and monoclonal antibodies.
Ocrelizumab was first approved in the United States in 2017 and subsequently authorized in the European Union. Regulatory documentation describes the conventional intravenous product as a 30 mg/mL concentrate, with 300 mg presented per vial.
As a recombinant monoclonal antibody, Ocrelizumab requires controlled biotechnological manufacturing and extensive characterization. Critical quality attributes can include molecular identity, protein concentration, biological activity, purity, aggregates, fragments, charge heterogeneity, glycan profile and process-related impurities.
Analytical programs for an Ocrelizumab biological API may therefore employ techniques such as peptide mapping, LC-based characterization, size-exclusion chromatography, capillary electrophoresis, glycan analysis, ELISA or other immunological methods, and cell-based or other validated biological potency assays, depending on the approved control strategy.
Unlike a conventional chemical API, parameters such as melting point, residue on ignition and specific rotation are not appropriate universal release tests for Ocrelizumab. The applicable specification should instead be based on the biological drug-substance control strategy and relevant regulatory requirements.
Ocrelizumab is an established therapeutic monoclonal antibody with regulatory authorization in major markets. The EMA's current product information identifies Ocrevus as containing ocrelizumab and describes its CD20-targeting mechanism. The EMA product information was updated in August 2026.
For pharmaceutical manufacturing applications, Ocrelizumab drug substance should be handled under appropriate GMP, biological manufacturing, sterility assurance and cold-chain controls, with testing performed against the manufacturer's validated and regulatory-approved specifications.
| 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% |