Catalytic Antibody Blunts Carfentanil-Induced Respiratory Depression

Abstract

Carfentanil, the most potent of the fentanyl analogues, is at the forefront of synthetic opioid-related deaths, second to fentanyl. Moreover, the administration of the opioid receptor antagonist naloxone has proven inadequate for an increasing number of opioid-related conditions, often requiring higher/additional doses to be effective, as such interest in alternative strategies to combat more potent synthetic opioids has intensified. Increasing drug metabolism would be one strategy to detoxify carfentanil; however, carfentanil’s major metabolic pathways involve N-dealkylation or monohydroxylation, which do not lend themselves readily to exogenous enzyme addition. Herein, we report, to our knowledge, the first demonstration that carfentanil’s methyl ester when hydrolyzed to its acid was found to be 40,000 times less potent than carfentanil in activating the μ-opioid receptor. Physiological consequences of carfentanil and its acid were also examined through plethysmography, and carfentanil’s acid was found to be incapable of inducing respiratory depression. Based upon this information, a hapten was chemically synthesized and immunized, allowing the generation of antibodies that were screened for carfentanil ester hydrolysis. From the screening campaign, three antibodies were found to accelerate the hydrolysis of carfentanil’s methyl ester. From this series of catalytic antibodies, the most active underwent extensive kinetic analysis, allowing us to postulate its mechanism of hydrolysis against this synthetic opioid. In the context of potential clinical applications, the antibody, when passively administered, was able to reduce respiratory depression induced by carfentanil. The data presented supports further development of antibody catalysis as a biologic strategy to complement carfentanil overdose reversal.

Opioid Overdose: Limitations in Naloxone Reversal of Respiratory Depression and Prevention of Cardiac Arrest

“…Respiratory stimulants with promising results in animal or human studies include nicotinic acetylcholine receptor agonists, ampakines, potassium channel blockers, partial opioid receptor agonists or antagonists, scrubber molecules, and monoclonal antibodies against specific opioids (including antibodies that enhance opioid metabolism). 8,54 Still, none of these strategies is currently sufficiently scrutinized to allow definite conclusions regarding effectiveness and safety. For example, it remains unknown whether these strategies are able to overcome severe respiratory depression (e.g., ventilation less than 40% of baseline, gasping, or apnea) and are able to prevent cardiac arrest.…”

Nanotherapeutics for Alleviating Anesthesia‐Associated Complications

“…[ 123 ] Murine, chimeric and humanized antibodies have been developed to capture or catalyze fentanyl and its analogs to counteract opioid toxicity. [ 124 , 125 , 126 ] For instance, a humanized monoclonal antibody, C10‐S66K displayed a high binding capacity to fentanyl and carfentanil (100‐fold more potent than fentanyl). Intraperitoneal injection of 30 mg kg −1 C10‐S66K antibody significantly alleviated respiratory depression caused by carfentanil overdose ( Figure 3 a ).…”

“…[123] Murine, chimeric and humanized antibodies have been developed to capture or catalyze fentanyl and its analogs to counteract opioid toxicity. [124][125][126] For instance, a humanized monoclonal antibody, C10-S66K displayed a high binding capacity to Two-way RM ANOVA was employed for statistical analysis; * p > 0.05, # p > 0.001. Reproduced with permission.…”

An Engineered Human-Antibody Fragment with Fentanyl Pan-Specificity That Reverses Carfentanil-Induced Respiratory Depression

“…The improved scFv, C10-S66K scFv-ABD, with a suitable in vivo t 1/2 was then tested in our respiratory depression mouse model using whole body plethysmography. Carfentanil displays dose-dependent respiratory depressive effects causing a measurable decrease in respiratory minute volume (MV), a product of tidal volume and respiratory rate. , Typically, a 30 μg/kg dose (IP) produces an ∼70% reduction in MV at maximum respiratory depression, 15 min post drug administration. In prior studies, we have demonstrated blockade of carfentanil’s respiratory depressive effects by vaccine elicited serum antibodies as well as passive immunization strategies; , however, a more pertinent model for counteracting drug intoxication as a countermeasure would be to demonstrate reversal of drug-induced respiratory depression post-exposure.…”