Δ9-tetrahydrocannabinol immunochemical studies:: Haptens, monoclonal antibodies, and a convenient synthesis of radiolabeled Δ9-tetrahydrocannabinol

Immunopharmacotherapy as an approach to combat drugs of abuse has become an active area of investigation. Marijuana is the most commonly used illicit drug in the U.S. The main active chemical in marijuana is Delta(9)-tetrahydrocannabinol (Delta(9)-THC); hence, monoclonal antibodies with high affinity and specificity for Delta(9)-tetrahydrocannabinol could be valuable immunopharmacotherapeutic intervention and diagnostic tools. We have synthesized immunoconjugates that induce an effective immune response to Delta(9)-THC and describe a convenient synthesis of radiolabeled Delta(9)-THC. We demonstrate the value and use of this probe to select anti-Delta(9)-THC antibodies that bind Delta(9)-THC with good affinity. The synthetic route to radiolabeled Delta(9)-THC has enabled the correct assessment of the affinity of these antibodies to their ligand and may facilitate future binding studies between Delta(9)-THC and its analogues and the cannabinoid receptors.