Monoclonal antibodies displaying mutations in Fc region to prolong protection against fentanyl toxicity

Abstract

Synthetic opioids including fentanyl are the lead cause of opioid-related deaths in the United States. Current treatments for opioid overdose include the opioid receptor antagonist naloxone; however, naloxone is not as effective against highly potent opioids, has a relatively short half-life, and precipitates withdrawal symptoms. Monoclonal antibody (mAb) therapy offers a promising strategy to combat opioid-related overdoses. Opioid-specific mAb bind to target molecules in the bloodstream and inhibit them from crossing the blood-brain barrier. We produced a lead fentanyl-specific mAb that protects against fentanyl toxicity in rats. The efficacy of mAbs is reliant on maintaining a high concentration in the bloodstream to ensure sufficient binding to the target drug. The neonatal Fc receptor (FcRn) is responsible for the recycling of IgG in circulation, thus increasing their effective half-life. Therefore, to increase the duration of efficacy of a lead chimeric fentanyl-specific mAb, we introduced three different mutations to the Fc region of the mAb. Biolayer interferometry paired with recombinant FcRn showed a 10-fold increase in affinity of the recombinant mAb compared to wild-type. Efficacy of the mutated and WT mAb against fentanyl-induced behavior and toxicity was also tested in mice. Both the mutated and WT mAb reduced fentanyl-induced antinociception, respiratory depression, and bradycardia. Finally, the half-life and long-term efficacy of these mutated mAbs was assessed in transgenic mice expressing human FcRn. Extending the half-life of these mAbs will facilitate more successful clinical approaches in preventing opioid-related overdoses. This work was funded by NIDA under CounterACT grant U01-DA051658