ABSTRACT
Description: Bexxar contains tositumomab, a murine IgG2a monoclonal antibody that specifically binds the CD 20 antigen. CD 20 is a surface antigen found on B lymphocytes, both normal and malignant. The 150-kDa antibody is composed of two gamma 2a heavy chains (451 amino acids each) and two light (lambda) chains (220 amino acids each). The Bexxar therapeutic regime entails the use of both tositumomab and radioactive tositumomab. Tositumomab is supplied as a sterile, preservative-free liquid concentrate containing 14 mg active/ml in 35-mg and 225-mg single-use vials. Radiolabeled tositumomab (131I-tositumomab) is also supplied as a sterile, preservative-free liquid concentrate, available at concentrations of 0.1 and 1.1 mg/ml.
