A Chimeric Human/Murine Anticocaine Monoclonal Antibody Inhibits the Distribution of Cocaine to the Brain in Mice

Abstract

The predominantly human sequence, high-affinity anticocaine monoclonal antibody (mAb) 2E2 was cleared slowly from mouse blood by a first-order process with an elimination t 1/2 of 8.1 days. Infused 2E2 also produced a dramatic dose-dependent increase in plasma cocaine concentrations and a concomitant decrease in the brain cocaine concentrations produced by an i.v. injection of cocaine HCl (0.56 mg/kg). At the highest dose of 2E2 tested (3:1, mAb/drug), cocaine was not detectable in the brain. Pharmacokinetic studies showed that the normal disappearance of cocaine from plasma was described by a two-compartment pharmacokinetic model with distribution t 1/2␣ and terminal elimination t 1/2␤ values of 1.9 and 26.1 min, respectively. In the presence of an equimolar dose of mAb 2E2, there was a 26-fold increase in the area under the plasma cocaine concentration-time curve (AUC) relative to the AUC in the absence of 2E2. Consequently, 2E2 decreased the volume of distribution of cocaine from 6.0 to 0.20 l/kg, which approximated that of 2E2 (0.28 l/kg). However, cocaine was still rapidly cleared from plasma, and its elimination was now described by a single-compartment model with an elimination t 1/2 of 17 min. Importantly, 2E2 also produced a 4.5-fold (78%) decrease in the cocaine AUC in the brain. Therefore, the effect of 2E2 on plasma and brain cocaine concentrations was predominantly caused by a change in the distribution of cocaine with negligible effects on its rate of clearance. These data support the concept of immunotherapy for drug abuse.Despite decades of basic and clinical research there is still no approved pharmacotherapy for the prevention of relapse in cocaine abusers (Vocci and Ling, 2005). The drug-induced reinstatement (priming) of drug self-administration behavior represents an animal model of relapse (DeWitt and Stewart, 1981) with the concentration of cocaine in the body a critical determinant of the probability of reinstating cocaine selfadministration (Norman et al., 1999(Norman et al., , 2002. Because the site of action of cocaine is presumably in the brain, decreasing the concentrations reaching the brain would be expected to decrease the probability of relapse. Antibodies with high affinity and specificity for cocaine would be expected to act as pharmacokinetic antagonists by sequestering cocaine in the peripheral circulation and preventing its entry to the brain. Indeed, active immunization of animals with hapten-carrier conjugates can elicit the production of polyclonal anticocaine antibodies with sufficient levels and affinity for cocaine that they can reduce the amount of cocaine entering the brain (Fox et al., 1996). Active immunization has also been shown to attenuate the behavioral effects (Carrera et al., 1995;Fox et al., 1996;Ettinger et al., 1997) and the priming effect (Carrera et al., 2000) of systemically administered cocaine in rats. Furthermore, the ability of active immunization to produce levels of polyclonal anticocaine antibodies in humans (Kosten et al., 2002) that we...

A Recombinant Humanized Anti-Cocaine Monoclonal Antibody Inhibits the Distribution of Cocaine to the Brain in Rats

“…This procedure was identical to that reported in a previous study (Norman et al, 2007). The mean 6 S.E.M.…”

“…The program provides Akaike Information Criterion and Schwartz Bayesian Criterion measures of model diagnostics of the data to the pharmacokinetic models that were used. Pharmacokinetic data were analyzed according to a two-compartment model based on previous evidence that a singlecompartment model gave a poor fit to the cocaine pharmacokinetic data (Norman et al, 2007). The two-compartment pharmacokinetic model used to fit the data assumed that cocaine distributed between a central and a peripheral compartment.…”

“…The in vivo concentrations of h2E2 following a single injection (120 mg/kg i.v.) were determined using an ELISA described previously (Paula et al, 2004;Norman et al, 2007) that compared the quantity of mAb in varying dilutions of the rat blood samples with that quantified in a standard curve using known dilutions of purified h2E2. The blood samples (10 ml each) were collected from a small incision at the tip of the tail, and the samples were collected at various time points up to 7 weeks after the administration of h2E2.…”

“…Cocaine, BE, and EME concentrations in plasma and brain were measured using solid-phase extraction, followed by GC/MS, according to the procedures detailed by Norman et al (2007).…”

“…However, the murine l L chain gene was not knocked out in this transgenic mouse strain, and 2E2 is a mixed-chain or chimeric mAb consisting of a human g 1 H and murine l L chain (Norman et al, 2007). This unusual mAb has a high affinity for cocaine and selectivity for cocaine over its inactive metabolites (Paula et al, 2004), and in vivo studies with mice have demonstrated that infused hybridomaderived 2E2 dramatically increases plasma cocaine levels and decreases the concentration of cocaine reaching the brain (Norman et al, 2007). Furthermore, in rats trained to self-administer cocaine, 2E2 increased the concentration of cocaine required to reinstate this behavior (Norman, et al, 2009).…”