Abstract

Fentanyl is an extremely potent synthetic opioid that has been increasingly used to adulterate heroin, cocaine and counterfeit prescription pills leading to an increase in opioid-induced fatal overdoses in the US, Canada, and Europe. A vaccine targeting fentanyl could offer protection against fatal overdoses in both recreational drug users and others in professions at risk of accidental exposure. This study focuses on the development of a vaccine consisting of a fentanyl hapten (F) conjugated to keyhole limpet hemocyanin (KLH) carrier protein or to GMP-grade subunit KLH (sKLH). Immunization with F-KLH in mice and rats reduced fentanyl-induced hotplate antinociception and in rats reduced fentanyl distribution to brain compared to controls. F-KLH did not reduce antinociceptive effects of equianalgesic doses of heroin or oxycodone in rats. To assess vaccine effect on fentanyl toxicity, rats immunized with F-sKLH or unconjugated sKLH were exposed to increasing s.c. doses of fentanyl. Vaccination with F-sKLH shifted the dose-response curves to the right for both fentanyl-induced antinociception and respiratory depression. Naloxone reversed fentanyl effects in both groups, showing that its activity for reversing opioid overdose was preserved. These data demonstrate pre-clinical selectivity and efficacy of a fentanyl vaccine and suggest that vaccines may offer a therapeutic option in reducing fentanyl-induced overdoses.