ibritumomab tiuxetan - Generic Medications

Zevalin (ibritumomab tiuxetan) is the immunoconjugate resulting from a stable thiourea covalent bond between the monoclonal antibody ibritumomab and the linker-chelator tiuxetan [N-[2-bis(carboxymethyl) amino]-3-(p-isothiocyanatophenyl)-propyl]-[N-[2-bis(carboxymethyl)amino]-2- (methyl)-ethyl]glycine. This linker-chelator provides a high affinity, conformationally restricted chelation site for Yttrium-90. The approximate molecular weight of ibritumomab tiuxetan is 148 kD. The antibody moiety of Zevalin is ibritumomab, a murine IgG 1 kappa monoclonal antibody directed against the CD20 antigen. Ibritumomab tiuxetan is a clear, colorless, sterile, pyrogen-free, preservative-free solution that may contain translucent particles. Each single-use vial includes 3.2 mg of ibritumomab tiuxetan in 2 mL of 0.9% Sodium Chloride. Physical/Radiochemical Characteristics of Y-90 Yttrium-90 decays by emission of beta particles, with a physical half-life of 64.1 hours (2.67 days). The product of radioactive decay is non-radioactive Zirconium-90. The range of beta particles in soft tissue ( χ 90) is 5 mm. Radiation emission data for Y-90 are summarized in Table 5 . Table 5. Principal Y-90 Radiation Emission Data Radiation Mean % per Disintegration Mean Energy (keV) Beta minus 100 750-935 External Radiation The exposure rate for 1 mCi (37 MBq) of Y-90 is 8.3 x 10 -3 C/kg/hr (32 R/hr) at the mouth of an open Y-90 vial. To allow correction for physical decay of Y-90, the fractions that remain at selected intervals before and after the time of calibration are shown in Table 6 . Table 6. Physical Decay Chart: Y-90 Half-life 2.67 Days (64.1 Hours) Calibration Time (Hrs.) Fraction Remaining Calibration Time (Hrs.) Fraction Remaining -36 1.48 0 1.00 -24 1.30 1 0.99 -12 1.14 2 0.98 -8 1.09 3 0.97 -7 1.08 4 0.96 -6 1.07 5 0.95 -5 1.06 6 0.94 -4 1.04 7 0.93 -3 1.03 8 0.92 -2 1.02 12 0.88 -1 1.01 24 0.77 0 1.00 36 0.68