BEXXAR: Product Information

The BEXXAR therapeutic regimen delivers the targeted action of a monoclonal antibody and the cytotoxic action of Iodine-131

The monoclonal antibody Tositumomab binds to the CD20 antigen on normal and malignant B lymphocytes
Cell death is associated with ionizing radiation from the radioisotope
Iodine-131

CHARACTERISTICS AND POSSIBLE MECHANISMS OF ACTION¹,4,5

Component

Characteristics

Possible Mechanisms of Action

Tositumomab

Tositumomab is a murine IgG2a lambda monoclonal antibody directed against the CD20 antigen, which is found on the surface of normal and malignant B lymphocytes
Iodine I 131 Tositumomab is a radioiodinated derivative of Tositumomab that has been covalently linked to Iodine-131
CD20 antigen is found on >90% of B-cell non-Hodgkin’s lymphomas

Apoptosis
Complement-dependent cytotoxicity
Antibody-dependent cellular cytotoxicity

Iodine-131

Radioisotope
Decays with beta and gamma emissions
Physical half-life of 8.04 days
Beta emission has a mean energy of 191.6 keV
Gamma emission has an energy of 364.5 keV

Cell death from ionizing radiation
Crossfire or “bystander” effect may kill tumor cells or normal B cells inaccessible to a nonradiolabeled antibody as well as the adjacent normal cells

Iodine 131 Tositumomab
Iodine I 131 Tositumomab binds to the CD20 antigen on normal and malignant B lymphocytes
"Crossfire" effect of Iodine-131 in BEXXAR may cause damage to tumor cells as well as adjacent normal tissue

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Complete Prescribing Information for
BEXXAR (Tositumomab and Iodine I 131 Tositumomab)

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