Bivalent Hapten Display Strategies for Conjugate Vaccines Targeting Opioid Mixtures Containing Fentanyl

Increasingly, street mixtures of opioids are reported to contain combinations of synthetic opioids, such as fentanyl with fentanyl analogues or counterfeit oxycodone pills containing fentanyl. While antiopioid immunotherapeutics have been investigated as a possible approach to address the opioid epidemic, the efficacy of vaccines and antibodies is limited to specific target opioids, based on the chemical structure of the haptens used in vaccines. Hence, there is a need for rational design of antiopioid conjugate vaccines that simultaneously target multiple opioids. Here, four novel haptens were synthesized, which were designed to elicit antibodies capable of binding to fentanyl other target opioids, including carfentanil, alfentanil, or oxycodone. Haptens were conjugated to CRM carrier protein and formulated with an aluminum salt adjuvant, and vaccines containing bivalent haptens were compared to admixtures of individual conjugate vaccines targeting the two opioids separately. Rats were immunized with monovalent, admixed, or novel bivalent vaccines, and the blockade of opioid effects was assessed against the individual drugs and their mixtures. Opioid-specific antibody titer was measured, and in vivo effects of vaccines were assessed in terms of preventing opioid-induced antinociception and respiratory depression and opioid distribution to the brain. While the bivalent vaccines reduced the effects of some target opioids, the admixed vaccine formulations were more effective against fentanyl/carfentanil and fentanyl/alfentanil mixtures. The bivalent fentanyl/oxycodone vaccine was as effective as the monovalent vaccines against a single drug challenge. These results inform the design of future vaccines against opioids and other drugs, particularly in the context of vaccines against polysubstance use that require optimization of response against multiple drugs of interest.