Ofatumumab is a recombinant human IgG1κ monoclonal antibody that specifically binds to the CD20 antigen expressed on B lymphocytes. It is a biologic drug substance belonging to the anti-CD20 monoclonal antibody class.
Ofatumumab was originally developed as HuMax-CD20 / 2F2 and is also associated with development codes GSK1841157 and OMB-157. The FDA Global Substance Registration System identifies the substance as a protein, with CAS 679818-59-8 and UNII M95KG522R0.
FDA describes ofatumumab as an IgG1κ human monoclonal antibody consisting of two IgG1 heavy chains and two kappa light chains, with a molecular weight of approximately 146–149 kDa depending on the product description/formulation and molecular characterization basis.
Ofatumumab is a recombinant human IgG1κ antibody that binds to both the small and large extracellular loops of CD20. Its antibody structure contains two heavy chains and two kappa light chains.
As a protein therapeutic, its characterization relies on biologic-specific analytical methods such as peptide mapping, mass spectrometry, electrophoretic analysis, chromatography, glycan characterization and functional binding/potency assays.
Ofatumumab binds specifically to CD20 on B lymphocytes. Binding to CD20 promotes B-cell depletion through immune-mediated mechanisms, including complement-dependent and antibody-dependent cellular mechanisms.
The FDA label identifies CD20 as the target and describes ofatumumab as a CD20-directed monoclonal antibody.
Ofatumumab is the active substance in KESIMPTA, which is used for the treatment of relapsing forms of multiple sclerosis. EMA identifies ofatumumab as the active substance of Kesimpta and lists multiple sclerosis as its therapeutic area.
Ofatumumab has also been used historically in the anti-CD20 treatment of B-cell malignancies under the former ARZERRA product. EMA's Arzerra authorization was withdrawn in 2019 at the request of the marketing authorization holder for commercial reasons.
Ofatumumab is a biological drug substance, so quality assessment focuses on:
EMA's biological-medicine guidance recognizes host-cell protein testing, monoclonal-antibody specifications and biological activity such as ADCC as relevant aspects of biologic drug-substance control.
| Parameter | Specification |
|---|---|
| Appearance | White crystalline powder or crystals |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| pH (1% Solution) | 6.0–8.0 |
| Individual Impurity | ≤0.10% |
| Total Impurities | NMT 1.0% |
| Water Content | NMT 1.0% |