Suppression of human melanoma growth in nude mice injected with anti high-molecular-weight melanoma-associated antigen monoclonal antibody 225.28S conjugated to purothionin.

The cytotoxic agent purothionin purified from barley was covalently conjugated to the anti-human high-molecular-weight melanoma-associated antigen (HMW-MAA) monoclonal antibody (MoAb) 225.28S by utilizing water-soluble carbodiimide. Injection of the conjugate (0.1 mg/injection) significantly increased the life span of nude mice injected with ascitic-form human melanoma cells (Colo 38), and caused 40% inhibition on day 25 of the growth of solid-form human melanoma cells in nude mice. The effect is specific and is markedly influenced by the site of growth of tumors and by the schedule of administration of the conjugate.