A single dose of monoclonal anti-phencyclidine IgG offers long-term reductions in phencyclidine behavioral effects in rats

These studies tested the hypothesis that a single dose of high-affinity anti-phencyclidine monoclonal antibody (anti-PCP mAb) provides long-term protection against behavioral effects of repeated PCP administration in rats. Rats were treated with saline, nonspecific bovine IgG (NS-IgG), or anti-PCP mAb (1.0 g/kg). The next morning, the rats were challenged with escalating i.v. doses of PCP (0.32, 0.56, and 1.0 mg/kg) at 90-min intervals. This regimen was repeated every 3 days for 2 weeks. In the saline and NS-IgG control groups, PCP yielded reproducible and linear dose-dependent effects that remained constant during the experiment. In contrast, the anti-PCP mAb treatment blocked PCP effects on day 1, and sustained significant (P < 0.05) reductions in drug effects for the entire 2-week experiment. Brain PCP concentrations (determined at study termination) were reduced by ∼55%, whereas serum concentrations were increased over 4000% compared with controls. Thus, a single dose of antibody medication provided long-term reductions in drug effects and brain concentrations, beyond the expected capacity of the drug-antibody interaction. These data challenge current concepts about in vivo dose dependence and unimolecular interaction between antibody binding sites and small molecules and establish that neuroprotection by mAbs may have an unique mechanism of action.