Inotuzumab ozogamicin is a CD22-directed antibody-drug conjugate (ADC) consisting of 3 components: 1) the recombinant humanized immunoglobulin class G subtype 4 (IgG4) kappa antibody inotuzumab, specific for human CD22, 2) N-acetyl-gamma-calicheamicin that causes double-stranded DNA breaks, and 3) an acid-cleavable linker composed of the condensation product of 4-(4'-acetylphenoxy)-butanoic acid (AcBut) and 3-methyl-3-mercaptobutane hydrazide (known as dimethylhydrazide) that covalently attaches N-acetyl-gamma-calicheamicin to inotuzumab.
Inotuzumab ozogamicin has an approximate molecular weight of 160 kDa. The average number of calicheamicin derivative molecules conjugated to each inotuzumab molecule is approximately 6 with a distribution from 2–8. Inotuzumab ozogamicin is produced by chemical conjugation of the antibody and small molecule components. The antibody is produced by mammalian (Chinese hamster ovary) cells, and the semisynthetic calicheamicin derivative is produced by microbial fermentation followed by synthetic modification.
BESPONSA (inotuzumab ozogamicin) for Injection is supplied as a sterile, white to off-white, preservative-free, lyophilized powder for intravenous administration. Each single-dose vial delivers 0.9 mg inotuzumab ozogamicin. Inactive ingredients are polysorbate 80 (0.36 mg), sodium chloride (2.16 mg), sucrose (180 mg), and tromethamine (8.64 mg). After reconstitution with 4 mL of Sterile Water for Injection, USP, the final concentration is 0.25 mg/mL of inotuzumab ozogamicin with a deliverable volume of 3.6 mL (0.9 mg) and a pH of approximately 8.0.