Experimental Studies On Antitumor Effects Against Human Hepatoma By The Immunoconjugate Composed Of Monoclonal Antibody Fab Fragment And Antitumor Antibiotic C1027

Chemoimmunoconjugate, a macromolecular substance composed of a monoclonal antibody (McAb) molecule and tens of drug molecules, is difficult to penetrate the interstitial space in a solid tumor to reach the tumor cells located in central area of the tumor mass. For better therapeutic effects, it is important to make an immunoconjugate with smaller molecular size. The present study has prepared a conjugate by linking the Fab fragment to C1027, an antitumor antibiotic with extremely potent cytotoxicity, at a molar ratio of approximately 1:1 and has examined its antitumor activity both in vitro and in vivo.McAb 3A5, a monoclonal antibody directed against human hepatoma BEL-7402 cells, was obtained from the rat hybridoma ascites. Fab fragment of 3A5 was prepared by digestion of the McAb and purification through the Sepharose 4B-Markl affinity column. By ELISA, McAb 3A5 and the Fab fragment were strongly reactive with hepatoma BEL-7402 cells and weakly reactive with KB cells. Using SPDP as the linker agent, McAb 3A5 and its Fab fragment were conjugated to C1027 separately and the immunoconjugates retained the activities of the both partners. For comparison, Markl-C1027 and BSA-C1027 conjugates were prepared by linking C1027 to Mark1, an irrelevant IgG, and bovine serum albumin, separately.As determined by clonogenic assay against hepatoma BEL-7402 cells for 1 h exposure to the drug, IC50 values...