Active
immunization is an emerging potential modality to combat
fatal overdose amid the opioid epidemic. In this study, we described
the design, synthesis, formulation, and animal testing of an efficacious
vaccine against fentanyl. The vaccine formulation is composed of a
novel fentanyl hapten conjugated to tetanus toxoid (TT) and adjuvanted
with liposomes containing monophosphoryl lipid A adsorbed on aluminum
hydroxide. The linker and hapten
N
-phenyl-
N
-(1-(4-(3-(tritylthio)propanamido)phenethyl)piperidin-4-yl)propionamide
were conjugated sequentially to TT using amine-
N
-hydroxysuccinimide-ester
and thiol–maleimide reaction chemistries, respectively. Conjugation
was facile, efficient, and reproducible with a protein recovery of
>98% and a hapten density of 30–35 per carrier protein molecule.
In mice, immunization induced high and robust antibody endpoint titers
in the order of >10
6
against the hapten. The antisera
bound
fentanyl, carfentanil, cyclopropyl fentanyl,
para
-fluorofentanyl, and furanyl fentanyl
in vitro
with
antibody-drug dissociation constants in the range of 0.36–4.66
nM. No cross-reactivity to naloxone, naltrexone, methadone, or buprenorphine
was observed.
In vivo
, immunization shifted the antinociceptive
dose–response curve of fentanyl to higher doses. Collectively,
these preclinical results showcased the desired traits of a potential
vaccine against fentanyl and demonstrated the feasibility of immunization
to combat fentanyl-induced effects.