TUMOUR-TARGETING AGENTS AND A METHOD OF TARGETING TUMOURS

摘要

An agent for use in targeting tumour cells comprises a compound (6) of a mean molecular weight of no more than about 70,000, and preferably of considerably lower molecular weight; it is thus able to pass relatively readily from the bloodstream into the extra-cellular fluid. The compound is able to become reversibly bound to characteristic antigens (5) on tumour cells (4) and to this end may include fragments (7) of antibodies. The compound also includes a ligand (9) that can become reversibly bound to a binding protein (10) naturally occurring in the bloodstream or introduced into the bloodstream. The complex formed by the compound and binding protein is eliminated from the body only relatively slowly and thus provides a continuing source of the compound for attachment to the tumour antigens. The compound may be radioactive or include a chemotherapeutic constituent. When it is desired to flush the compound from the body, an unreactive substance that competes with the binding protein is introduced into the bloodstream at relatively high concentrations, thus displacing the compound from the binding protein and enabling it to be eliminated by the kidneys.