Antitumor activity of L/1C2-4-desacetylvinblastine-3-carboxhydrazide immunoconjugate in xenografts.

The murine IgG3 monoclonal antibody L/1C2 is reactive with a high percentage of human carcinomas and has preferentially strong reactivity with tumors of squamous differentiation. This antibody was tested for antitumor activity in vitro and in xenograft models as a carbohydrate-linked immunoconjugate with the Vinca derivative 4-desacetylvinblastine-3-carboxhydrazide (DAVLBHYD). The conjugate retained good immunoreactivity and was highly active in a cytotoxicity assay. In human tumor nude mouse xenograft studies, L/1C2-DAVLBHYD antitumor activity was superior to that seen with free drug, free antibody, mixtures of free drug and free antibody, or control DAVLBHYD conjugates prepared with non-tumor-binding IgGs. With well-established tumors, potent antitumor activity was observed, including the ability to specifically regress greater than 400-mg tumors to 0 mg. In some cases, apparent long-term cures were effected. In studies using six different human tumor xenografts, the level of potency of L/1C2-DAVLBHYD was related to L/1C2 antigen expression, although the growth rate probably also contributes to the conjugate sensitivity of the tumors.

New antitumor monoclonal antibody-vinca conjugates LY203725 and related compounds: design, preparation, and representative in vivo activity.

A method has been developed to allow the direct coupling of the cytotoxic vinca alkaloid 4-desacetylvinblastine-3-carbohydrazide (DAVLB hydrazide) to a variety of murine monoclonal antibodies directed against human solid tumors. Periodate oxidation of carbohydrate residues on the antibodies, followed by reaction with DAVLB hydrazide in aqueous acid affords, in most cases, conjugates with conjugation ratios of 4-6 vincas per antibody in high yield without significantly impairing antigen binding or solubility. The outcome of the conjugation reaction is highly dependent on the concentration of, and time of exposure of the protein to, the oxidant. These conjugates exhibit potent antitumor activity in vivo against a number of human solid tumor-nude mouse xenografts, with efficacy and safety increased over unconjugated DAVLB hydrazide. This antitumor activity is also superior to that of similarly prepared but nontarget tumor binding antibody-DAVLB hydrazide conjugates. MoAb-DAVLB hydrazide conjugates release DAVLB hydrazide in solution in a temperature- and pH-dependent manner. Hydrolytic release of unmodified DAVLB hydrazide from tumor-localized MoAb-DAVLB hydrazide conjugates in vivo may be an important factor in their antitumor activity.

Succinylated polylysine as a possible link between an antibody molecule and deferoxamine.

Modification of antibodies with chelating polymers may be helpful for radioimmunoimaging, radioimmunotherapy, and NMR tomography. Succinylated polylysine was activated with carbodiimide/N-hydroxysulfosuccinimide in dimethyl sulfoxide and isolated as a dry solid. Sulfosuccinimide-esterified polymer was used for the two-stage coupling of an amino-containing chelating agent (deferoxamine) to monoclonal R11D10 (IgG) or its Fab fragment. Conjugates were separated from free components by using gel-chromatography and anion-exchange chromatography. Antibody-coupling efficiency and the loss of its immunoreactivity upon modification have been studied for polymers with different deferoxamine content. Specific binding of 67Ga to the corresponding antigen via the conjugate has been demonstrated.

Conjugates of mitomycin C with the immunoglobulin M monomer fragment of a monoclonal anti-MM46 immunoglobulin M antibody with or without serum albumin as intermediary.

In studies on antitumor antibody-drug conjugates as potential antitumor agents with improved tumor specificity, conjugates of mitomycin C (MMC) with the IgMs fragment of a monoclonal IgM antibody to a tumor-associated antigen (MM antigen) on mouse mammary tumor MM46 cell (anti-MM46 IgMs) were prepared by direct and bovine serum albumin (BSA)-mediated indirect conjugation. MMC was linked to the IgMs and BSA by the use of 1a-[4-(N-succinimidoxycarbonyl)butyryl]mitomycin C, which allowed the slow release of MMC. In the indirect conjugation, the thiol group of BSA was first protected as the 2-pyridyldithio group and, after the MMC binding, regenerated with dithiothreitol, and the resulting BSA-MMC was reacted with the IgMs having the maleimide group introduced with N-succinimidyl m-(N-maleimido)benzoate. Anti-MM46 IgMs-MMC was more cytotoxic against the target MM antigen-positive but Thy 1.2 antigen-negative MM46 cells than control anti-Thy 1.2 IgM-MMC. No such selective cytotoxicity was observed between anti-MM46 IgMs-MMC and anti-Thy 1.2 IgMs-MMC against the MM antigen- and Thy 1.2 antigen-negative MM48 cells. Anti-MM46 IgMs-BSA-MMC was more cytotoxic against MM46 cells than was a mixture of unconjugated anti-MM46 IgMs and BSA-MMC.