The Effect of a Humanized Anti‐Cocaine Monoclonal Antibody on the In Vitro Metabolism of Cocaine

Abstract

The humanized anti‐cocaine monoclonal antibody (mAb) h2E2 is a lead candidate for treating cocaine‐use disorders and relapse. When cocaine binds to h2E2, it is hypothesized to be unavailable for hydrolysis by endogenous esterases such as liver carboxylesterase I (CES1) and butyrylcholinesterase (BChE). Therefore, h2E2 is expected to slow the clearance of cocaine. However, pharmacokinetic studies in rats and mice demonstrate an apparently unchanged elimination half‐life (t1/2β) of cocaine in the presence of h2E2. To explore this paradoxical finding, we investigated the effect of h2E2 on the in vitro metabolism of cocaine by CES1, which hydrolyzes cocaine to benzoylecgonine (BE), and by BChE, which hydrolyzes cocaine to ecgonine methyl ester (EME). Cocaine hydrochloride (20 μM) was incubated at 37°C with a range of concentrations of either CES1 or BChE in the presence or absence of h2E2 (10 μM). Aliquots were collected at designated time points over 60 minutes. Cocaine and metabolite concentrations in each sample were measured using LC‐MS/MS. In CES1 reactions, there was a time‐dependent formation of BE in the absence of h2E2 (n=5). The mAb dramatically inhibited the production of BE by greater than 90% at all enzyme concentrations. Preliminary data (n=1) also suggest h2E2 prevents the hydrolysis of cocaine to EME by BChE. The dramatic decrease in both the production of BE and EME in the presence of the antibody is consistent with h2E2 reducing the concentration of free cocaine by acting as a chemical antagonist. In addition, it is possible that the substantial h2E2‐induced increase in plasma cocaine concentrations may alter the in vivo metabolism of cocaine in favor of butyrylcholinesterase, thereby increasing the relative proportion of EME. This and the paradoxical elimination of cocaine from plasma in vivo should be resolved through a more extensive investigation of the pharmacokinetics of cocaine in the presence of the antibody.Support or Funding InformationThis work was supported by the National Institutes of Health, National Institute on Drug Abuse grant number U01DA039550 (ABN).displays benzoylecgonine production (ng/mL) over time (minutes). Samples containing CES1, h2E2, and cocaine (n=5) are shown in black. The non‐h2E2 group (n=5) is shown in blue. Data were normalized with baseline cocaine readings (t=0). The graph displays an initial timecourse of 60 minutes.Figure 1