antimetabolite

n. substance that works against metabolism

An antimetabolite is a chemical with a similar structure to a substance (a metabolite) required for normal biochemical reactions, yet different enough to interfere with the normal functions of cells, including cell division.
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Antimetabolite /an·ti·me·tab·o·lite/ a substance bearing a close structural resemblance to one required for normal physiological functioning, and [more]Antimetabolite - Community and Resources

Noun
1. an antineoplastic drug that inhibits the utilization of a metabolite
(hypernym) antineoplastic, antineoplastic drug, cancer drug
(hyponym) fluorouracil

n. antimetabolite, substance that works against metabolism