Self-Adjuvanting TLR7/8 Agonist and Fentanyl Hapten Co-Conjugate Achieves Enhanced Protection against Fentanyl Challenge

Abstract

Currently approved pharmacotherapies for opioid use disorders (OUDs) and overdose reversal agents are insufficient to slow the spread of OUDs due to the proliferation of fentanyl. This is evident in the 31% rise in drug overdose deaths from 2019 to 2022, with rates increasing from 21.6 to 28.3 overdoses per 100,000 deaths. Vaccines are a potential alternative or adjunct therapy for the treatment of several substance use disorders (nicotine, cocaine) but have shown limited clinical success due to suboptimal antibody titers. In this study, we demonstrate that coconjugation of a Toll-like receptor 7/8 (TLR7/8) agonist (UM-3006) alongside a fentanyl-based hapten (F 1 ) on the surface of the carrier protein cross-reactive material 197 (CRM) significantly increased generation of high-affinity fentanyl-specific antibodies. This demonstrated enhanced protection against fentanyl challenges relative to an unconjugated (admix) adjuvant control in mice. Inclusion of aluminum hydroxide (alum) adjuvant further increased titers and enhanced protection, as determined by analysis of fentanyl concentration in serum and brain tissue. Collectively, our findings present a promising approach to enhance the efficacy of antiopioid vaccines, underscoring the need for extensive exploration of TLR7/8 agonist conjugates as a compelling strategy to combat opioid use disorders.

Multivalent Vaccination Strategies Protect against Exposure to Polydrug Opioid and Stimulant Mixtures in Mice and Rats

“…It is conceivable that boosting the efficacy of each individual vaccine could enable concurrent protection against higher drug doses or more complex drug mixtures. Incorporating TLR agonists into the vaccine formulation, for example, has been shown to increase the efficacy of conjugate vaccines. ,,,− …”

“…Preclinical studies identified lead haptens designed to target fentanyl (F), carfentanil (Carf), oxycodone (Oxy), and heroin/morphine (M), whose individual lead candidate conjugate vaccines (F-CRM, Carf-CRM, Oxy-sKLH, and M-sKLH, respectively) were effective in blocking the distribution of their respective target drug to the brain and reducing their behavioral effects in mice, rats, ,− and mini-pigs . Among these conjugate vaccines, a vaccine against oxycodone (Oxy-sKLH) is currently in Phase I clinical trials (NCT04458545), while the other lead conjugate vaccines F-CRM and M-sKLH are either in the process of being manufactured or readied for upcoming clinical trials, which will include the incorporation of toll-like receptor (TLR) 7/8 agonists to enhance efficacy. ,, Throughout the remainder of this paper, the M hapten and its conjugated form, M-sKLH, will be referred to as “Her” and “Her-sKLH”, respectively, as they target heroin, 6-acetylmorphine (6-MAM), and morphine …”