Combined cocaine hydrolase gene transfer and anti-cocaine vaccine synergistically block cocaine-induced locomotion

Catalytic Antibody Blunts Carfentanil-Induced Respiratory Depression

Carfentanil, the most potent of the fentanyl analogues, is at the forefront of synthetic opioid-related deaths, second to fentanyl. Moreover, the administration of the opioid receptor antagonist naloxone has proven inadequate for an increasing number of opioid-related conditions, often requiring higher/additional doses to be effective, as such interest in alternative strategies to combat more potent synthetic opioids has intensified. Increasing drug metabolism would be one strategy to detoxify carfentanil; however, carfentanil's major metabolic pathways involve N-dealkylation or monohydroxylation, which do not lend themselves readily to exogenous enzyme addition. Herein, we report, to our knowledge, the first demonstration that carfentanil's methyl ester when hydrolyzed to its acid was found to be 40,000 times less potent than carfentanil in activating the μ-opioid receptor. Physiological consequences of carfentanil and its acid were also examined through plethysmography, and carfentanil's acid was found to be incapable of inducing respiratory depression. Based upon this information, a hapten was chemically synthesized and immunized, allowing the generation of antibodies that were screened for carfentanil ester hydrolysis. From the screening campaign, three antibodies were found to accelerate the hydrolysis of carfentanil's methyl ester. From this series of catalytic antibodies, the most active underwent extensive kinetic analysis, allowing us to postulate its mechanism of hydrolysis against this synthetic opioid. In the context of potential clinical applications, the antibody, when passively administered, was able to reduce respiratory depression induced by carfentanil. The data presented supports further development of antibody catalysis as a biologic strategy to complement carfentanil overdose reversal.

Reengineering of Albumin-Fused Cocaine Hydrolase CocH1 (TV-1380) to Prolong Its Biological Half-Life

Therapeutic treatment of cocaine toxicity or addiction is a grand medical challenge. As a promising therapeutic strategy for treatment of cocaine toxicity and addiction to develop a highly efficient cocaine hydrolase (CocH) capable of accelerating cocaine metabolism to produce physiologically/biologically inactive metabolites, our previously designed A199S/S287G/A328W/Y332G mutant of human butyrylcholinesterase (BChE), known as cocaine hydrolase-1 (CocH1), possesses the desirably high catalytic activity against cocaine. The C-terminus of CocH1, truncated after amino acid #529, was fused to human serum albumin (HSA) to extend the biological half-life. The C-terminal HSA-fused CocH1 (CocH1-HSA), known as Albu-CocH1, Albu-CocH, AlbuBChE, Albu-BChE, or TV-1380 in literature, has shown favorable preclinical and clinical profiles. However, the actual therapeutic value of TV-1380 for cocaine addiction treatment is still limited by the short half-life. In this study, we designed and tested a new type of HSA-fused CocH1 proteins, i.e., N-terminal HSA-fused CocH1, with or without a linker between the HSA and CocH1 domains. It has been demonstrated that the catalytic activity of these new fusion proteins against cocaine is similar to that of TV-1380. However, HSA-CocH1 (without a linker) has a significantly longer biological half-life (t_1/2 = 14 ± 2 h) compared to the corresponding C-terminal HSA-fused CocH1, i.e., CocH1-HSA (TV-1380 with t_1/2 = 5-8 h), in rats. Further, the N-terminal HSA-fused CocH1 proteins with a linker have further prolonged biological half-lives: t_1/2 = 17 ± 2 h for both HSA-EAAAK-CocH1 and HSA-PAPAP-CocH1, and t_1/2 = 18 ± 3 h for HSA-(PAPAP)₂-CocH1. These N-terminal HSA-fused CocH1 proteins may serve as more promising protein drug candidates for cocaine addiction treatment.

Ethical Implications in Vaccine Pharmacotherapy for Treatment and Prevention of Drug of Abuse Dependence

Different immunotherapeutic approaches are in the pipeline for the treatment of drug dependence. "Drug vaccines" aim to induce the immune system to produce antibodies that bind to drugs and prevent them from inducing rewarding effects in the brain. Drugs of abuse currently being tested using these new approaches are opioids, nicotine, cocaine, and methamphetamine. In human clinical trials, "cocaine and nicotine vaccines" have been shown to induce sufficient antibody levels while producing few side effects. Studies in humans, determining how these vaccines interact in combination with their target drug, are underway. However, although vaccines can become a reasonable treatment option for drugs of abuse, there are several disadvantages that must be considered. These include i) great individual variability in the formation of antibodies, ii) the lack of protection against a structurally dissimilar drug that produces the same effects as the drug of choice, and iii) the lack of an effect on the drug desire that may predispose an addict to relapse. In addition, a comprehensive overview of several crucial ethical issues has not yet been widely discussed in order to have not only a biological approach to immunotherapy of addiction. Overall, immunotherapy offers a range of possible treatment options: the pharmacological treatment of addiction, the treatment of overdoses, the prevention of toxicity to the brain or the heart, and the protection of the fetus during pregnancy. So far, the results obtained from a small-scale experiment using vaccines against cocaine and nicotine suggest that a number of important technical challenges still need to be overcome before such vaccines can be approved for clinical use.

Current status and future prospects for the development of substance abuse vaccines

INTRODUCTION

Substance use disorders (SUD) are a significant threat to both individual and public health. To date, SUD pharmacotherapy has focused primarily on agonist medications (i.e. nicotine replacement therapy for tobacco use disorder; methadone and buprenorphine for opioid use disorder), antagonist medications (i.e. naltrexone for opioid use disorder), and aversive therapy (i.e. disulfiram for alcohol use disorder). Pharmacotherapeutic approaches utilizing an immunological framework for medication development represent an important focus of study for treatment of these illnesses. Areas covered: This review discusses vaccines for treatment of substance use disorders. Using PubMed ( https://www.ncbi.nlm.nih.gov/pubmed/ ), we searched both preclinical and human clinical trials of vaccines for treatment of nicotine, cocaine, methamphetamine, and opioid use disorders. In addition, we searched for recently developed strategies for enhancement of the immunologic response through alteration of conjugate molecules and adjuvants. Expert commentary: Despite challenges in human clinical trials of SUD vaccines, a number of strategies have been introduced which may ultimately improve efficacy. These challenges, as well as their implications for vaccine development, are discussed. Additionally, the optimal conditions for research study and treatment are considered.

Augmenting the efficacy of anti-cocaine catalytic antibodies through chimeric hapten design and combinatorial vaccination

Given the need for further improvements in anti-cocaine vaccination strategies, a chimeric hapten (GNET) was developed that combines chemically-stable structural features from steady-state haptens with the hydrolytic functionality present in transition-state mimetic haptens. Additionally, as a further investigation into the generation of an improved bifunctional antibody pool, sequential vaccination with steady-state and transition-state mimetic haptens was undertaken. While GNET induced the formation of catalytically-active antibodies, it did not improve overall behavioral efficacy. In contrast, the resulting pool of antibodies from GNE/GNT co-administration demonstrated intermediate efficacy as compared to antibodies developed from either hapten alone. Overall, improved antibody catalytic efficiency appears necessary to achieve the synergistic benefits of combining cocaine hydrolysis with peripheral sequestration.

Biologics to treat substance use disorders: Current status and new directions

Biologics (vaccines, monoclonal antibodies (mAb), and genetically modified enzymes) offer a promising class of therapeutics to treat substance use disorders (SUD) involving abuse of opioids and stimulants such as nicotine, cocaine, and methamphetamine. In contrast to small molecule medications targeting brain receptors, biologics for SUD are larger molecules that do not cross the blood-brain barrier (BBB), but target the drug itself, preventing its distribution to the brain and blunting its effects on the central nervous system (CNS). Active and passive immunization approaches rely on antibodies (Ab) that bind drugs of abuse in serum and block their distribution to the brain, preventing the rewarding effects of drugs and addiction-related behaviors. Alternatives to vaccines and anti-drug mAb are genetically engineered human or bacterial enzymes that metabolize drugs of abuse, lowering the concentration of free active drug. Pre-clinical and clinical data support development of effective biologics for SUD.

Long-Term Blockade of Cocaine Self-Administration and Locomotor Activation in Rats by an Adenoviral Vector-Delivered Cocaine Hydrolase

A promising approach in treating cocaine abuse is to metabolize cocaine in the blood using a mutated butyrylcholinesterase (BChE) that functions as a cocaine hydrolase (CocH). In rats, a helper-dependent adenoviral (hdAD) vector-mediated delivery of CocH abolished ongoing cocaine use and cocaine-primed reinstatement of drug-seeking for several months. This enzyme also metabolizes ghrelin, an effect that may be beneficial in maintaining healthy weights. The effect of a single hdAD-CocH vector injection was examined in rats on measures of anxiety, body weight, cocaine self-administration, and cocaine-induced locomotor activity. To examine anxiety, periadolescent rats were tested in an elevated-plus maze. Weight gain was then examined under four rodent diets. Ten months after CocH-injection, adult rats were trained to self-administer cocaine intravenously and, subsequently, cocaine-induced locomotion was tested. Viral gene transfer produced sustained plasma levels of CocH for over 13 months of testing. CocH-treated rats did not differ from controls in measures of anxiety, and only showed a transient reduction in weight gain during the first 3 weeks postinjection. However, CocH-treated rats were insensitive to cocaine. At 10 months postinjection, none of the CocH-treated rats initiated cocaine self-administration, unlike 90% of the control rats. At 13 months postinjection, CocH-treated rats showed no cocaine-induced locomotion, whereas control rats showed a dose-dependent enhancement of locomotion. CocH vector produced a long-term blockade of the rewarding and behavioral effects of cocaine in rats, emphasizing its role as a promising therapeutic intervention in cocaine abuse.

Cocaine Hydrolase Gene Transfer Demonstrates Cardiac Safety and Efficacy against Cocaine-Induced QT Prolongation in Mice

Cocaine addiction is associated with devastating medical consequences, including cardiotoxicity and risk-conferring prolongation of the QT interval. Viral gene transfer of cocaine hydrolase engineered from butyrylcholinesterase offers therapeutic promise for treatment-seeking drug users. Although previous preclinical studies have demonstrated benefits of this strategy without signs of toxicity, the specific cardiac safety and efficacy of engineered butyrylcholinesterase viral delivery remains unknown. Here, telemetric recording of electrocardiograms from awake, unrestrained mice receiving a course of moderately large cocaine doses (30 mg/kg, twice daily for 3 weeks) revealed protection against a 2-fold prolongation of the QT interval conferred by pretreatment with cocaine hydrolase vector. By itself, this prophylactic treatment did not affect QT interval duration or cardiac structure, demonstrating that viral delivery of cocaine hydrolase has no intrinsic cardiac toxicity and, on the contrary, actively protects against cocaine-induced QT prolongation.

Reward and Toxicity of Cocaine Metabolites Generated by Cocaine Hydrolase

Butyrylcholinesterase (BChE) gene therapy is emerging as a promising concept for treatment of cocaine addiction. BChE levels after gene transfer can rise 1000-fold above those in untreated mice, making this enzyme the second most abundant plasma protein. For months or years, gene transfer of a BChE mutated into a cocaine hydrolase (CocH) can maintain enzyme levels that destroy cocaine within seconds after appearance in the blood stream, allowing little to reach the brain. Rapid enzyme action causes a sharp rise in plasma levels of two cocaine metabolites, benzoic acid (BA) and ecgonine methyl ester (EME), a smooth muscle relaxant that is mildly hypotensive and, at best, only weakly rewarding. The present study, utilizing Balb/c mice, tested reward effects and cardiovascular effects of administering EME and BA together at molar levels equivalent to those generated by a given dose of cocaine. Reward was evaluated by conditioned place preference. In this paradigm, cocaine (20 mg/kg) induced a robust positive response but the equivalent combined dose of EME + BA failed to induce either place preference or aversion. Likewise, mice that had undergone gene transfer with mouse CocH (mCocH) showed no place preference or aversion after repeated treatments with a near-lethal 80 mg/kg cocaine dose. Furthermore, a single administration of that same high cocaine dose failed to affect blood pressure as measured using the noninvasive tail-cuff method. These observations confirm that the drug metabolites generated after CocH gene transfer therapy are safe even after a dose of cocaine that would ordinarily be lethal.

Nano-antidotes for drug overdose and poisoning

The number of intoxications from xenobiotics—natural or synthetic foreign chemicals, or substances given in higher doses than typically present in humans—has risen tremendously in the last decade, placing poisoning as the leading external cause of death in the United States. This epidemic has fostered the development of antidotal nanomedicines, which we call “nano-antidotes,” capable of efficiently neutralizing offending compounds in situ. Although prototype nano-antidotes have shown efficacy in proof-of-concept studies, the gap to clinical translation can only be filled if issues such as the clinical relevance of intoxication models and the safety profile of nano-antidotes are properly addressed. As the unmet medical needs in resuscitative care call for better treatments, this Perspective critically reviews the recent progress in antidotal medicine and emerging nanotechnologies.

Vaccines against drugs of abuse: where are we now?

Drug addiction is a serious problem worldwide. One therapy being investigated is vaccines against drugs of abuse. The antibodies elicited against the drug can take up the drug and prevent it from reaching the reward centers in the brain. Few such vaccines have entered clinical trials, but research is going on apace. Many studies are very promising and more clinical trials should be coming out in the near future.

Vaccine for cocaine dependence: a randomized double-blind placebo-controlled efficacy trial

AIMS

We evaluated the immunogenicity, efficacy, and safety of succinylnorcocaine conjugated to cholera toxin B protein as a vaccine for cocaine dependence.

METHODS

This 6-site, 24 week Phase III randomized double-blind placebo-controlled trial assessed efficacy during weeks 8 to 16. We measured urine cocaine metabolites thrice weekly as the main outcome.

RESULTS

The 300 subjects (76% male, 72% African-American, mean age 46 years) had smoked cocaine on average for 13 days monthly at baseline. We hypothesized that retention might be better and positive urines lower for subjects with anti-cocaine IgG levels of ≥42 μg/mL (high IgG), which was attained by 67% of the 130 vaccine subjects receiving five vaccinations. Almost 3-times fewer high than low IgG subjects dropped out (7% vs 20%). Although for the full 16 weeks cocaine positive urine rates showed no significant difference between the three groups (placebo, high, low IgG), after week 8, more vaccinated than placebo subjects attained abstinence for at least two weeks of the trial (24% vs 18%), and the high IgG group had the most cocaine-free urines for the last 2 weeks of treatment (OR=3.02), but neither were significant. Injection site reactions of induration and tenderness differed between placebo and active vaccine, and the 29 serious adverse events did not lead to treatment related withdrawals, or deaths.

CONCLUSIONS

The vaccine was safe, but it only partially replicated the efficacy found in the previous study based on retention and attaining abstinence.

Physiologic and metabolic safety of butyrylcholinesterase gene therapy in mice

In continuing efforts to develop gene transfer of human butyrylcholinesterase (BChE) as therapy for cocaine addiction, we conducted wide-ranging studies of physiological and metabolic safety. For that purpose, mice were given injections of adeno-associated virus (AAV) vector or helper-dependent adenoviral (hdAD) vector encoding human or mouse BChE mutated for optimal cocaine hydrolysis. Age-matched controls received saline or AAV-luciferase control vector. At times when transduced BChE was abundant, physiologic and metabolic parameters in conscious animals were evaluated by non-invasive Echo-MRI and an automated "Comprehensive Laboratory Animal Monitoring System" (CLAMS). Despite high vector doses (up to 10(13) particles per mouse) and high levels of transgene protein in the plasma (∼1500-fold above baseline), the CLAMS apparatus revealed no adverse physiologic or metabolic effects. Likewise, body composition determined by Echo-MRI, and glucose tolerance remained normal. A CLAMS study of vector-treated mice given 40 mg/kg cocaine showed none of the physiologic and metabolic fluctuations exhibited in controls. We conclude that neither the tested vectors nor great excesses of circulating BChE affect general physiology directly, while they protect mice from disturbance by cocaine. Hence, viral gene transfer of BChE appears benign and worth exploring as a therapy for cocaine abuse and possibly other disorders as well.

The future potential for cocaine vaccines

INTRODUCTION

Addiction to cocaine is a major problem around the world, but especially in developed countries where the combination of wealth and user demand has created terrible social problems. Although only some users become truly addicted, those who are often succumb to a downward spiral in their lives from which it is very difficult to escape. From the medical perspective, the lack of effective and safe, non-addictive therapeutics has instigated efforts to develop alternative approaches for treatment, including anticocaine vaccines designed to block cocaine's pharmacodynamic effects.

AREAS COVERED

This paper discusses the implications of cocaine pharmacokinetics for robust vaccine antibody responses, the results of human vaccine clinical trials, new developments in animal models for vaccine evaluation, alternative vaccine formulations and complementary therapy to enhance anticocaine effectiveness.

EXPERT OPINION

Robust anti-cocaine antibody responses are required for benefit to cocaine abusers, but since any reasonably achievable antibody level can be overcome with higher drug doses, sufficient motivation to discontinue use is also essential so that the relative barrier to cocaine effects will be appropriate for each individual. Combining a vaccine with achievable levels of an enzyme to hydrolyze cocaine to inactive metabolites, however, may substantially increase the blockade and improve treatment outcomes.

Long-term reduction of cocaine self-administration in rats treated with adenoviral vector-delivered cocaine hydrolase: evidence for enzymatic activity

A new pharmacokinetic approach treating cocaine addiction involves rapidly metabolizing cocaine before it reaches brain reward centers using mutated human butyrylcholinesterase (BChE) or cocaine hydrolase (CocH). Recent work has shown that helper-dependent adenoviral (hdAD) vector-mediated plasma CocH reduced the locomotor-activating effects of cocaine and prevented reinstatement of cocaine-seeking behavior up to 6 months in rats. The present study investigated whether hdAD-CocH could decrease ongoing intravenous cocaine (0.4 mg/kg) self-administration. The hdAD-CocH vector was injected into self-administering rats, and after accumulation of plasma CocH, there was a dramatic reduction in cocaine infusions earned under a fixed ratio 1 schedule of reinforcement that lasted for the length of the study (>2 months). Pretreatment with the selective BChE and CocH inhibitor iso-OMPA (1.5 mg/kg) restored cocaine intake; therefore, the decline in self-administration was likely due to rapid CocH-mediated cocaine metabolism. Direct measurements of cocaine levels in plasma and brain samples taken after the conclusion of behavioral studies provided strong support for this conclusion. Further, rats injected with hdAD-CocH did not experience a deficit in operant responding for drug reinforcement and self-administered methamphetamine (0.05 mg/kg) at control levels. Overall, these outcomes suggest that viral gene transfer can yield plasma CocH levels that effectively diminish long-term cocaine intake and may have potential treatment implications for cocaine-dependent individuals seeking to become and remain abstinent.

Experimental treatments for cocaine toxicity: a difficult transition to the bedside

Cocaine is a commonly abused illicit drug that causes significant morbidity and mortality. Although there is no true antidote to cocaine toxicity, current management strategies address the life-threatening systemic effects, namely hyperthermia, vasospasm, and severe hypertension. Clinicians rely on rapid cooling, benzodiazepines, and α-adrenergic antagonists for management, with years of proven benefit. Experimental agents have been developed to more effectively treat acute toxicity. Pharmacodynamic approaches include antipsychotics that are thought to interfere with cocaine's actions at several neurotransmitter receptors. However, these medications may worsen the consequences of cocaine toxicity as they can interfere with heat dissipation, cause arrhythmias, and lower the seizure threshold. Pharmacokinetic approaches use cocaine-metabolizing enzymes, such as butyrylcholinesterase (BChE), cocaine hydrolase (CocH), and bacterial cocaine esterase (CocE). Experimental models with these therapies improve survival, primarily when administered before cocaine, although newer evidence demonstrates beneficial effects shortly after cocaine toxicity has manifested. CocE, a foreign protein, can induce an immune response with antibody formation. When enzyme administration was combined with vaccination against the cocaine molecule, improvement in cocaine-induced locomotor activity was observed. Finally, lipid emulsion rescue has been described in human case reports as an effective treatment in patients with hemodynamic compromise because of cocaine, which correlates well with its documented benefit in toxicity due to other local anesthetics. A pharmaceutical developed from these concepts will need to be expedient in onset and effective with minimal adverse effects while at the same time being economical.

Adenovirus capsid-based anti-cocaine vaccine prevents cocaine from binding to the nonhuman primate CNS dopamine transporter

Cocaine addiction is a major problem for which there is no approved pharmacotherapy. We have developed a vaccine to cocaine (dAd5GNE), based on the cocaine analog GNE linked to the capsid proteins of a serotype 5 adenovirus, designed to evoke anti-cocaine antibodies that sequester cocaine in the blood, preventing access to the CNS. To assess the efficacy of dAd5GNE in a large animal model, positron emission tomography (PET) and the radiotracer [(11)C]PE2I were used to measure cocaine occupancy of the dopamine transporter (DAT) in nonhuman primates. Repeat administration of dAd5GNE induced high anti-cocaine titers. Before vaccination, cocaine displaced PE2I from DAT in the caudate and putamen, resulting in 62±4% cocaine occupancy. In contrast, dAd5GNE-vaccinated animals showed reduced cocaine occupancy such that when anti-cocaine titers were >4 × 10(5), the cocaine occupancy was reduced to levels of <20%, significantly below the 47% threshold required to evoke the subjective 'high' reported in humans.

Preparation and in vivo characterization of a cocaine hydrolase engineered from human butyrylcholinesterase for metabolizing cocaine

Cocaine is a widely abused drug without an FDA (Food and Drug Administration)-approved medication. It has been recognized that an ideal anti-cocaine medication would accelerate cocaine metabolism producing biologically inactive metabolites via a route similar to the primary cocaine-metabolizing pathway, i.e. human BChE (butyrylcholinesterase)-catalysed hydrolysis. However, the native human BChE has a low catalytic activity against cocaine. We recently designed and discovered a BChE mutant (A199S/F227A/S287G/A328W/Y332G) with a high catalytic activity (kcat=5700 min-1, Km=3.1 μM) specifically for cocaine, and the mutant was proven effective in protecting mice from acute cocaine toxicity of a lethal dose of cocaine (180 mg/kg of body weight, LD100). Further characterization in animal models requires establishment of a high-efficiency stable cell line for the BChE mutant production at a relatively larger scale. It has been extremely challenging to develop a high-efficiency stable cell line expressing BChE or its mutant. In the present study, we successfully developed a stable cell line efficiently expressing the BChE mutant by using a lentivirus-based repeated-transduction method. The scaled-up protein production enabled us to determine for the first time the in vivo catalytic activity and the biological half-life of this high-activity mutant of human BChE in accelerating cocaine clearance. In particular, it has been demonstrated that the BChE mutant (administered to mice 1 min prior to cocaine) can quickly metabolize cocaine and completely eliminate cocaine-induced hyperactivity in rodents, implying that the BChE mutant may be developed as a promising therapeutic agent for cocaine abuse treatment.

Prospects, promise and problems on the road to effective vaccines and related therapies for substance abuse

This review addresses potential new treatments for stimulant drugs of abuse, especially cocaine. Clinical trials of vaccines against cocaine and nicotine have been completed with the generally encouraging result that subjects showing high titers of antidrug antibody experience a reduction in drug reward, which may aid in cessation. New vaccine technologies, including gene transfer of highly optimized monoclonal antibodies, are likely to improve such outcomes further. In the special case of cocaine abuse, a metabolic enzyme is emerging as an alternative or added therapeutic intervention, which would also involve gene transfer. Such approaches still require extensive studies of safety and efficacy, but they may eventually contribute to a robust form of in vivo drug interception that greatly reduces the risks of addiction relapse.

Gene transfer of mutant mouse cholinesterase provides high lifetime expression and reduced cocaine responses with no evident toxicity

Gene transfer of a human cocaine hydrolase (hCocH) derived from butyrylcholinesterase (BChE) by 5 mutations (A199S/F227A/S287G/A328W/Y332G) has shown promise in animal studies for treatment of cocaine addiction. To predict the physiological fate and immunogenicity of this enzyme in humans, a comparable enzyme was created and tested in a conspecific host. Thus, similar mutations (A199S/S227A/S287G/A328W/Y332G) were introduced into mouse BChE to obtain a mouse CocH (mCocH). The cDNA was incorporated into viral vectors based on: a) serotype-5 helper-dependent adenovirus (hdAD) with ApoE promoter, and b) serotype-8 adeno-associated virus with CMV promoter (AAV-CMV) or multiple promoter and enhancer elements (AAV-VIP). Experiments on substrate kinetics of purified mCocH expressed in HEK293T cells showed 30-fold higher activity (U/mg) with ³H-cocaine and 25% lower activity with butyrylthiocholine, compared with wild type BChE. In mice given modest doses of AAV-CMV-mCocH vector (0.7 or 3×10¹¹ particles) plasma hydrolase activity rose 10-fold above control for over one year with no observed immune response. Under the same conditions, transduction of the human counterpart continued less than 2 months and antibodies to hCocH were readily detected. The advanced AAV-VIP-mCocH vector generated a dose-dependent rise in plasma cocaine hydrolase activity from 20-fold (10¹⁰ particles) to 20,000 fold (10¹³ particles), while the hdAD vector (1.7×10¹² particles) yielded a 300,000-fold increase. Neither vector caused adverse reactions such as motor weakness, elevated liver enzymes, or disturbance in spontaneous activity. Furthermore, treatment with high dose hdAD-ApoE-mCocH vector (1.7×10¹² particles) prevented locomotor abnormalities, other behavioral signs, and release of hepatic alanine amino transferase after a cocaine dose fatal to most control mice (120 mg/kg). This outcome suggests that viral gene transfer can yield clinically effective cocaine hydrolase expression for lengthy periods without immune reactions or cholinergic dysfunction, while blocking toxicity from drug overdose.

Probing active cocaine vaccination performance through catalytic and noncatalytic hapten design

Presently, there are no FDA-approved medications to treat cocaine addiction. Active vaccination has emerged as one approach to intervene through the rapid sequestering of the circulating drug, thus terminating both psychoactive effects and drug toxicity. Herein, we report our efforts examining two complementary, but mechanistically distinct active vaccines, i.e., noncatalytic and catalytic, for cocaine treatment. A cocaine-like hapten GNE and a cocaine transition-state analogue GNT were used to generate the active vaccines, respectively. GNE-KLH (keyhole limpet hemocyannin) was found to elicit persistent high-titer, cocaine-specific antibodies and blunt cocaine-induced locomotor behaviors. Catalytic antibodies induced by GNT-KLH were also shown to produce potent titers and suppress locomotor response in mice; however, upon repeated cocaine challenges, the vaccine's protecting effects waned. In depth kinetic analysis suggested that loss of catalytic activity was due to antibody modification by cocaine. The work provides new insights for the development of active vaccines for the treatment of cocaine abuse.

Effects of anti-cocaine vaccine and viral gene transfer of cocaine hydrolase in mice on cocaine toxicity including motor strength and liver damage

In developing an vivo drug-interception therapy to treat cocaine abuse and hinder relapse into drug seeking provoked by re-encounter with cocaine, two promising agents are: (1) a cocaine hydrolase enzyme (CocH) derived from human butyrylcholinesterase and delivered by gene transfer; (2) an anti-cocaine antibody elicited by vaccination. Recent behavioral experiments showed that antibody and enzyme work in a complementary fashion to reduce cocaine-stimulated locomotor activity in rats and mice. Our present goal was to test protection against liver damage and muscle weakness in mice challenged with massive doses of cocaine at or near the LD50 level (100-120 mg/kg, i.p.). We found that, when the interceptor proteins were combined at doses that were only modestly protective in isolation (enzyme, 1mg/kg; antibody, 8 mg/kg), they provided complete protection of liver tissue and motor function. When the enzyme levels were ~400-fold higher, after in vivo transduction by adeno-associated viral vector, similar protection was observed from CocH alone.

Anti-cocaine antibody and butyrylcholinesterase-derived cocaine hydrolase exert cooperative effects on cocaine pharmacokinetics and cocaine-induced locomotor activity in mice

We are investigating treatments for cocaine abuse based on viral gene transfer of a cocaine hydrolase (CocH) derived from human butyrylcholinesterase, which can reduce cocaine-stimulated locomotion and cocaine-primed reinstatement of drug-seeking behavior in rats for many months. Here, in mice, we explored the possibility that anti-cocaine antibodies can complement the actions of CocH to reduce cocaine uptake in brain and block centrally-evoked locomotor stimulation. Direct injections of test proteins showed that CocH (0.3 or 1mg/kg) was effective by itself in reducing drug levels in plasma and brain of mice given cocaine (10mg/kg, s.c., or 20mg/kg, i.p). Administration of cocaine antibody per se at a low dose (8 mg/kg, i.p.) exerted little effect on cocaine distribution. However, a higher dose of antibody (12 mg/kg) caused peripheral trapping (increased plasma drug levels), which led to increased cocaine metabolism by CocH, as evidenced by a 6-fold rise in plasma benzoic acid. Behavioral tests with small doses of CocH and antibody (1 and 8 mg/kg, respectively) showed that neither agent alone reduced mouse locomotor activity triggered by a very large cocaine dose (100mg/kg, i.p.). However, dual treatment completely suppressed the locomotor stimulation. Altogether, we found cooperative and possibly synergistic actions that warrant further exploration of dual therapies for treatment of cocaine abuse.