Prophylactic Active Immunization Protects against Xylazine-Induced Pharmacological Effects in Rats

Opioid-related overdoses have continued to rise in the past decade and have been further exacerbated by polydrug exposure involving the α₂ adrenergic receptor agonist xylazine, a veterinary tranquilizer referred to as "tranq" or "tranq dope". Despite the growing threat of xylazine and other α₂ adrenergic receptor agonists, no FDA-approved treatment or prophylaxis exists for xylazine-induced overdose toxicity in humans. To address this unmet need, our team developed and characterized a series of novel xylazine-based haptens and their cognate conjugate vaccines. This study tested their efficacy against xylazine-induced pharmacological effects in rats. Our results demonstrated that active immunization provides protection against xylazine by limiting its entry into the brain and mitigating its pharmacological effects. This study also provides preliminary evidence that a xylazine vaccine can be combined with a fentanyl vaccine through a multivalent formulation strategy to provide protection against drug mixtures of xylazine and synthetic opioids. These findings highlight the potential for immunotherapeutics to prevent toxicity resulting from xylazine and polydrug exposure.