Development and evaluation of drug-antibody conjugates for the treatment of human myelogenous leukemia

An immune serum to the Ph1+ human myelogenous leukemia cell line, K-562, was developed in goats. Following exhaustive absorptions, the antiserum and its immunoglobulin (Ig) fraction were highly cytotoxic for the homologenous cells in vitro in the presence of complement. In a nude mouse-human myelogenous leukemia model system, the Ig inhibits the growth and proliferation of myelosarcomas made up of K-562 cells. At the concentration of 6 mg or more, and beginning at 7 days after transplantation of myelosarcomas in nude mice, the administration of immunoglobulins resulted in the total suppression and subsequent elimination of the tumors. The dose-response relationship between the amount of Ig injected and the growth of myelosarcomas was demonstrated to be linear i.e., the extent of inhibition of tumor growth was directly dependent upon the dose of Ig given. Also, the uptake of 125I-labelled immunoglobulins by the K-562 myelosarcomas was at least 6-fold higher than that of the corresponding preimmune globulins