Fluorescent Cocaine Probes: A Tool for the Selection and Engineering of Therapeutic Antibodies

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Abstract
Cocaine is a highly addictive drug, and despite intensive efforts, effective therapies for cocaine craving and addiction remain elusive. In recent years, we and others have reported advances in anti-cocaine immunopharmacotherapy based on specific antibodies capable of sequestering the drug before it reaches the brain. In an effort to obtain high affinity therapeutic anti-cocaine antibodies, either whole IgGs or other antibody constructs, fluorescence spectroscopic techniques could provide a means of assisting selection and engineering strategies. We report the synthesis of a series of cocaine−fluorophore conjugates (GNC − F1, GNC − F2, GNC − I) and the functional evaluation of these compounds against single-chain Fv antibodies obtained via crystallographic analysis/engineering and against commercially available anti-cocaine monoclonal antibodies with a wide range of cocaine-binding affinities. From these studies, we determined that the GNC − F2 fluorophore reproduced affinity constants obtained using [3H]-labeled cocaine. We anticipate that the readily synthesized and nonradioactive GNC − F2 will find use both as a tool for bioimaging and in the high-throughput selection and engineering of potential therapeutic antibodies against cocaine.