Reduction of toxicity of a vinca alkaloid by an anti-vinca alkaloid antibody.

Inadvertent oncolytic overdoses occur rarely, but can have serious consequences. We have investigated the possibility of using an antibody, 27.8.1A, reactive with vinca alkaloids, as a means of reducing the toxicity associated with overdose situations. In vitro cytotoxicity of a vinca derivative, 4-desacetyl- vinblastine-3-carbox-hydrazide (DAVLBHYD), with and without the addition of 27.8.1A, was determined. Using CCRF-CEM, a human acute lymphoblastic leukemia cell line, as a target in this assay, we observed a greater than 90% increase in cell viability using 100 micrograms/ml 27.8.1A with a 0.1 microgram/ml concentration of DAVLBHYD. 27.8.1A had no effect on cell viability when doxorubicin was used as a control drug in this assay. Similarly, the addition of an irrelevant antibody. EGFrL11, had no effect on the toxicity of DAVLBHYD. In an in vivo survival experiment, nude mice were injected with a toxic dose of DAVLBHYD and subsequently given four doses of 27.8.1A. All anti vinca antibody-treated mice survived, in contrast to the untreated group or irrelevant antibody-treated group in which only 25% and 10% of the mice survived, respectively.