Patent ID: 7470429

Claim:
A method for increasing the target-specific toxicity of a chemotherapeutic agent, comprising: a) pretargeting an enzyme to a mammalian target site, wherein said pretargeting comprises (i) administering a bispecific antibody or binding fragment thereof, wherein one arm of the bispecific antibody is targeted against a target site antigen and a second arm is targeted against a low molecular weight hapten that is conjugated to said enzyme and (ii) administering a low molecular weight hapten that is conjugated to said enzyme; and b) administering a cytotoxic chemotherapeutic agent known to act at the target site, or a prodrug form thereof which is converted to the chemotherapeutic agent in situ, which chemotherapeutic agent is also detoxified to form an intermediate of lower toxicity using said mammal's ordinary metabolic processes, whereby the detoxified intermediate is reconverted to its more toxic form by the pretargeted enzyme and thus has enhanced cytotoxicity at the target site, wherein said hapten is DTPA or a DTPA chelate.