An antifentanyl monoclonal antibody reverses fentanyl-induced apnea in pigs

The incidence of fatal drug overdoses has increased dramatically over the past decade due to the widespread availability of fentanyl and its analogs. As a complementary strategy to current overdose reversal agents, monoclonal antibodies (mAbs) are in development as therapeutics for prevention and reversal of fentanyl overdose. In the present study, the anti-fentanyl mAb HY6-F9 was tested for reversal of fentanyl-induced respiratory arrest (apnea) in a porcine model. In a first study, following fentanyl-induced apnea, chimeric HY6-F9 and naloxone control were administered as an intravenous bolus. Both chimeric HY6-F9 and naloxone restored spontaneous breathing within 90 seconds. Treatment with mAb increased the concentration of fentanyl in serum by 10-fold within the first minute after mAb bolus administration. In a second study, after induction of apnea, humanized HY6-F9 and naloxone control were administered as a slow intravenous infusion over 10 minutes to determine the ED₅₀ to restore baseline breathing. In this study, the mean ± SEM ED₅₀ of humanized HY6-F9 and naloxone to restore baseline respiratory rate were 16.0 ± 1.3 mg/kg and 6.9 ± 1.8 μg/kg, respectively. During mAb infusion, the concentration of fentanyl in serum increased proportionally to the concentration of infused mAb. The anti-fentanyl mAb ablated fentanyl-dependent opioid receptor activation in an in vitro system with concentrations of fentanyl similar to those observed in pigs after mAb treatment. These results demonstrate the efficacy of an anti-fentanyl mAb as a treatment to reverse fentanyl overdose. SIGNIFICANCE STATEMENT: Treatments for opioid use disorder and overdose are urgently needed. Here, we show that an anti-fentanyl monoclonal antibody reversed fentanyl-induced apnea in pigs, and caused rapid (<1 minute) redistribution of fentanyl into serum. Fentanyl was 99% bound by monoclonal antibodies and showed no activity at the opioid receptor.