Anti‐fentanyl Vaccines and Monoclonal Antibodies are Effective in Prevention and Reversal of Fentanyl‐induced Overdose in Rats

Abstract

The incidence of drug overdose deaths in the United States is an alarming public health threat that has accelerated during the COVID-19 pandemic, with over 80,000 deaths recorded in 2020. A substantial portion of this increase is attributable to the widespread access to fentanyl and other synthetic opioids, either used alone or encountered as adulterants in heroin or psychostimulants such as cocaine or methamphetamine. Vaccines and monoclonal antibodies (mAb) offer prophylactic and therapeutic interventions against opioid overdose by binding to the target opioids in serum, and reducing drug distribution to the brain. Here, the efficacy of anti-fentanyl vaccines and mAb for prevention and reversal of fentanyl-induced overdose was investigated in rats. Rats were immunized with a candidate vaccine consisting of a fentanyl-based hapten (F) conjugated to a diphtheria toxin carrier protein (CRM), or with a control vaccine. Rats were challenged subcutaneously with doses of 0.25 mg/kg fentanyl every 15 minutes to a cumulative dose of 2.25mg/kg, or until cardiac and/or respiratory arrest occurred. Prophylactic immunization with F-CRM was effective in counteracting fentanyl-induced respiratory depression, bradycardia, and antinociception; and reduced the incidence of mortality compared to control. Additionally, a murine anti-fentanyl mAb was isolated from mice immunized against fentanyl. Purified mAb had previously shown pre-exposure efficacy in protecting mice and rats from fentanyl challenges. To evaluate the efficacy of mAb in reversing fentanyl overdose post-exposure, rats were dosed with 0.1-0.5 mg/kg fentanyl, and 15 minutes later received 40 mg/kg mAb, 0.1 mg/kg naloxone, or both intravenously. Within 15 minutes, treatment with mAb reduced fentanyl-induced respiratory depression and bradycardia, and compared favorably to naloxone in terms of the degree and rate of onset of protection. One week later, rats retained mAb-induced protection from the effects of additional doses of fentanyl, as confirmed by a 10-fold reduction of the distribution of fentanyl to the brain compared to control. These results support translation of vaccines and mAb as medical interventions to prevent and reverse opioid overdose related to fentanyl and its analogs.