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 Δ⁹- tetrahydrocannabinol (Δ⁹-THC); hence, monoclonal antibodies with high affinity and specificity for Δ⁹-tetrahydrocannabinol could be valuable immunopharmacotherapeutic intervention and diagnostic tools. We have synthesized immunoconjugates that induce an effective immune response to Δ⁹-THC and describe a convenient synthesis of radiolabeled Δ⁹-THC. We demonstrate the value and use of this probe to select anti-Δ⁹-THC antibodies that bind Δ⁹-THC with good affinity. The synthetic route to radiolabeled Δ⁹-THC has enabled the correct assessment of the affinity of these antibodies to their ligand and may facilitate future binding studies between Δ⁹- THC and its analogues and the cannabinoid receptors.