Disease markers
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Following an extensive series of studies in nude mice with human xenografts a pilot scale clinical trial of antibody directed enzyme prodrug therapy has been initiated. The principle is to activate a relatively inert prodrug to an active cytotoxin by a tumour located enzyme. In the first stage of the study a prodrug para-N-(mono-2-chloroethyl monomesyl)-aminobenzoyl glutamic acid was administered to six patients with advanced colorectal cancer in a dose escalating protocol. ⋯ Two patients received higher doses which resulted in myelosuppression and temporary regression of advanced disease. No complications resulted from administration of the antibody-enzyme complex or enzyme inactivating antibody. The myelosuppression is attributable to the relatively long half-life of the active drug formed from the prodrug used in the present study.