Bifunctional Behavior of Conformationally Constrained Methamphetamine Analogs: Unexpected Heteroclitic Immune Response and Antagonist Effects Altering Methamphetamine and Fentanyl Pharmacology

Methamphetamine addiction is a growing global health crisis with no FDA-approved pharmacotherapies. Vaccination offers a promising therapeutic strategy, yet clinical translation has been limited by immune response inefficacy. Here, we evaluated three methamphetamine vaccine candidates: H1, a conventional hapten based on traditional drug–hapten–vaccine logic, and H2 and H3, two conformationally constrained analogs incorporating pyrrolidine and azetidine scaffolds, respectively. The rigidified hapten H2 produced an unprecedented heteroclitic immune response, with mature antibodies binding methamphetamine with an order of magnitude greater affinity than the immunizing scaffold. Although vaccine haptens are rarely assessed for intrinsic bioactivity, the pyrrolidine scaffold of H2, termed S1, exhibited distinct pharmacology, which was markedly divergent from methamphetamine. S1 is also capable of mitigating not only methamphetamine but also fentanyl-induced physiological effects. Methamphetamine conformational constraint offers a new tool for methamphetamine vaccine development as well as promising therapeutic agents for reversal of methamphetamine behavior and fentanyl-induced toxicity.