ENHANCED CELLULAR UPTAKE AND IN-VIVO BIODISTRIBUTION OF A MONOCLONAL-ANTIBODY FOLLOWING CATIONIZATION

Owing to the poor transport of monoclonal antibodies across either cap illary or cell membrane barriers, drug delivery strategies are needed to target monoclonal antibodies to intracellular sites where proteins function. One antibody drug delivery strategy is cationization, wherei n the isoelectric point Ipl) is raised by conversion of surface carbox yl groups to extended primary amino groups. The present studies descri be the cationization of a murine monoclonal antibody (D146) prepared a gainst a synthetic peptide encoding the Asp(13) point mutation of the res protooncogenic p21 protein. The pi of the D146 monoclonal antibody was raised from 8.9 to >9.5. The uptake in vitro of the (125)l-labele d native D146 antibody by MDA-MB231 human carcinoma cells was negligib le, whereas there was a marked increase in the endocytosis of the anti body following cationization. In vivo pharmacokinetic analysis was per formed in male BALB/c mice. The in vivo organ uptake of the cationized monoclonal antibody was increased relative to the native antibody; th ere was a B-fold increase in the systemic volume of distribution, a 58 -fold increase in the systemic clearance of the cationized antibody fr om the plasma compartment, and a 9-fold reduction in the mean residenc e time of the cationized antibody as compared to the native D146 antib ody. In conclusion, these studies show that cationization of an oncoge ne-specific monoclonal antibody results in markedly increased endocyto sis of the antibody by cancer cells in vitro and in increased systemic clearance and organ uptake in vivo.