Methods and substances for recruiting therapeutic agents to solid tumors

Abstract

Disclosed is a method of using bifunctional binding molecules, such as two linked V -V single chain binding molecules, to recruit a therapeutic agent to a solid tissue site. The therapeutic agent is administered separately from the binding molecules and following the administration of a remover substance which aids in clearing free binding molecules in the circulation. In the preferred mode of the invention, the binding molecules have one specificity for antigens at the target site and one for the therapeutic agent. The binding molecules are administered and allowed time to approach a maximum concentration in the extravascular space. A remover substance, preferably a liposome conjugated with antibodies which are reactive with an antigenic epitope on the binding molecules, is then administered to remove excess binding molecules from the circulation and the extravascular space. A therapeutic agent, preferably a cytotoxic drug such as ricin A chain modified so as to enable it to enter the target cells once delivered to the target site, is then administered.