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Substance Name: Tositumomab [USAN:INN]
RN: 208921-02-2
UNII: 0343IGH41U


  • NCI: A murine IgG2a lambda monoclonal antibody, both unradiolabeled and radiolabeled with iodine I 131, directed against the human B cell-specific surface antigen CD20. Tositumomab binds to CD20, resulting in complement-dependent cytotoxicity (CDC), antibody-dependent cellular cytotoxicity (ADCC), and apoptosis in B cells expressing CD20; in addition to the antibody-mediated cytotoxicity, iodine I 131 tositumomab delivers cytotoxic ionizing radiation specifically to CD20-expressing B cells. In a two-step therapeutic regimen, a predose of unradiolabeled tositumomab is administered first followed by the administration of a dosimetric dose of iodine I 131 tositumomab; 7-14 days later, a therapeutic dose of iodine I 131 tositumomab is administered. The predose of unradiolabeled tositumomab binds to nontumor B cells, increasing the terminal half-life of radiolabeled antibody while protecting nontumor B cells from radiolabeled antibody-mediated radiocytotoxicity. (NCI Thesaurus)

Molecular Formula

  • Unspecified

Classification Code

  • Antineoplastic Agents
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Names and Synonyms

Name of Substance

  • Tositumomab [USAN:INN]


  • Tositumomab
  • UNII-0343IGH41U

Systematic Name

  • Immunoglobulin G2a, anti-(human CD20 (antigen)) (mouse monoclonal clone B1R1 gamma2a-chain), disulfide with mouse monoclonal clone B1R1 lambdax-chain, dimer

Registry Numbers

CAS Registry Number

  • 208921-02-2


  • 0343IGH41U

System Generated Number

  • 0208921022