Preparation and Investigation of Monoclonal Antibodies to Block Xylazine's Mechanism of Action and Adverse Effects

Project Summary/Abstract. Xylazine has been reported as an adulterant in an increasing number of illicit drug mixtures; tragically, it has also been detected in a growing number of overdose deaths. Adulterants are substances typically added to illicit drugs that are intended to increase the value, increase the content, and modulate the activity of the drug while increasing its desirability. Adulterants can come from a wide range of pharmacological categories; however, due to its impact on the opioid crisis, xylazine is the first adulterant declared as an emerging threat by the White House’s Office of National Drug Control Policy. From a pharmacological standpoint, xylazine is a strong agonist of alpha-2 adrenergic receptors that decreases the release of norepinephrine and dopamine from the brain and thus forms a sedative effect. Xylazine is typically used in veterinary medicine, yet is readily available for purchase on internet sites, often with no association to the veterinary profession nor requirements to prove legitimate need. Indeed, xylazine powder can be purchased online with common prices ranging from $6-$20 US dollars per kilogram. At this low price, its use as an adulterant increases the profit for illicit drug traffickers, as its psychoactive effects allow them to reduce the amount of synthetic opioid used in a mixture. It also attracts customers seeking a longer “high”, since xylazine has many of the same effects for users as opioids but with a longer-lasting effect than the opioid alone. Complicating xylazine’s non-opiate sedative/analgesic effects, xylazine appears to cause severe skin ulcers developing mostly on extremities both at and away from drug injection sites, often within hours or days of exposure, that can quickly progress into large, complex, chronic wounds. Moreover, xylazine-associated wounds and xylazine withdrawal reportedly act as significant barriers to care, including addiction treatment. There is currently no antidote for xylazine poisoning other than supportive care, underscoring the need for effective measures to treat acute toxicity caused by xylazine. Moreover, the diverse and complex physiological processes involving the alpha-2 adrenergic receptors convolutes the use of a simple receptor antagonist to target the CNS site of action. As a starting point to neutralize xylazine’s pharmacologic effects, our overarching goal will be to generate a humanized monoclonal antibody with high affinity and specificity for xylazine. To meet this objective, we have proposed three specific aims that follow in a logical fashion including: (1) Isolation and production of monoclonal antibodies targeting xylazine. (2) Determination of the behavioral effects of the selected monoclonal antibodies on drug pharmacodynamics. (3) Humanization of the chosen lead anti-xylazine monoclonal antibody. A key aspect of the proposal is that it will provide a therapeutic for immediate changes in both the amount and the rate of xylazine entry into medically critical sites of action in the CNS while its preparation in a multi-manifold antibody format will engender the ability to prepare the first bispecific antibody against xylazine adulterated clandestine drugs.