Kinetic characterization of human butyrylcholinesterase mutants for the hydrolysis of cocaethylene

In vitro and in vivo stability of a highly efficient long-acting cocaine hydrolase

It is recognized as a promising therapeutic strategy for cocaine use disorder to develop an efficient enzyme which can rapidly convert cocaine to physiologically inactive metabolites. We have designed and discovered a series of highly efficient cocaine hydrolases, including CocH5-Fc(M6) which is the currently known as the most efficient cocaine hydrolase with both the highest catalytic activity against (-)-cocaine and the longest biological half-life in rats. In the present study, we characterized the time courses of protein appearance, pH, structural integrity, and catalytic activity against cocaine in vitro and in vivo of a CocH5-Fc(M6) bulk drug substance produced in a bioreactor for its in vitro and in vivo stability after long-time storage under various temperatures (- 80, - 20, 4, 25, or 37 °C). Specifically, all the tested properties of the CocH5-Fc(M6) protein did not significantly change after the protein was stored at any of four temperatures including - 80, - 20, 4, and 25 °C for ~ 18 months. In comparison, at 37 °C, the protein was less stable, with a half-life of ~ 82 days for cocaine hydrolysis activity. Additionally, the in vivo studies further confirmed the linear elimination PK profile of CocH5-Fc(M6) with an elimination half-life of ~ 9 days. All the in vitro and in vivo data on the efficacy and stability of CocH5-Fc(M6) have consistently demonstrated that CocH5-Fc(M6) has the desired in vitro and in vivo stability as a promising therapeutic candidate for treatment of cocaine use disorder.

Long-lasting blocking of interoceptive effects of cocaine by a highly efficient cocaine hydrolase in rats

Cocaine dependence is a serious world-wide public health problem without an FDA-approved pharmacotherapy. We recently designed and discovered a highly efficient long-acting cocaine hydrolase CocH5-Fc(M6). The present study examined the effectiveness and duration of CocH5-Fc(M6) in blocking interoceptive effects of cocaine by performing cocaine discrimination tests in rats, demonstrating that the duration of CocH5-Fc(M6) in blocking cocaine discrimination was dependent on cocaine dose and CocH5-Fc(M6) plasma concentration. Particularly, a dose of 3 mg/kg CocH5-Fc(M6) effectively attenuated discriminative stimulus effects of 10 mg/kg cocaine, cumulative doses of 10 and 32 mg/kg cocaine, and cumulative doses of 10, 32 and 56 mg/kg cocaine by ≥ 20% for 41, 19, and 10 days, and completely blocked the discriminative stimulus effects for 30, 13, and 5 days with corresponding threshold plasma CocH5-Fc(M6) concentrations of 15.9, 72.2, and 221 nM, respectively, under which blood cocaine concentration was negligible. Additionally, based on the data obtained, cocaine discrimination model is more sensitive than the locomotor activity to reveal cocaine effects and that CocH5-Fc(M6) itself has no long-term toxicity regarding behavioral activities such as lever pressing and food consumption in rats, further demonstrating that CocH5-Fc(M6) has the desired properties as a promising therapeutic candidate for prevenance of cocaine dependence.

Preclinical and clinical developments in enzyme-loaded red blood cells: an update

INTRODUCTION

We have previously described the preclinical developments in enzyme-loaded red blood cells to be used in the treatment of several rare diseases, as well as in chronic conditions.

AREA COVERED

Since our previous publication we have seen further progress in the previously discussed approaches and, interestingly enough, in additional new studies that further strengthen the idea that red blood cell-based therapeutics may have unique advantages over conventional enzyme replacement therapies in terms of efficacy and safety. Here we highlight these investigations and compare, when possible, the reported results versus the current therapeutic approaches.

EXPERT OPINION

The continuous increase in the number of new potential applications and the progress from the encapsulation of a single enzyme to the engineering of an entire metabolic pathway open the field to unexpected developments and confirm the role of red blood cells as cellular bioreactors that can be conveniently manipulated to acquire useful therapeutic metabolic abilities. Positioning of these new approaches versus newly approved drugs is essential for the successful transition of this technology from the preclinical to the clinical stage and hopefully to final approval.

Gender differences in cocaine-induced hyperactivity and dopamine transporter trafficking to the plasma membrane

As well known, cocaine induces stimulant effects and dopamine transporter (DAT) trafficking to the plasma membrane of dopaminergic neurons. In the present study, we examined cocaine-induced hyperactivity along with cocaine-induced DAT trafficking and the recovery rate of the dopaminergic system in female rats in comparison with male rats, demonstrating interesting gender differences. Female rats are initially more sensitive to cocaine than male rats in terms of both the DAT trafficking and hyperactivity induced by cocaine. Particularly, intraperitoneal (i.p.) administration of 5 mg/kg cocaine induced significant hyperactivity and DAT trafficking in female rats but not in male rats. After repeated cocaine exposures (i.e., i.p. administration of 20 mg/kg cocaine every other day from Day 0 to Day 32), cocaine-induced hyperactivity in female rats gradually became a clear pattern of two phases, with the first phase of the hyperactivity lasting for only a few minutes and the second phase lasting for over an hour beginning at ~30 min, which is clearly different from that of male rats. It has also been demonstrated that the striatal DAT distribution of female rats may recover faster than that of male rats after multiple cocaine exposures. Nevertheless, despite the remarkable gender differences, our recently developed long-acting cocaine hydrolase, known as CocH5-Fc(M6), can similarly and effectively block cocaine-induced DAT trafficking and hyperactivity in both male and female rats.

Development of a Highly Efficient Long-Acting Cocaine Hydrolase Entity to Accelerate Cocaine Metabolism

It is particularly challenging to develop a truly effective pharmacotherapy for cocaine use disorder (CUD) treatment. Accelerating cocaine metabolism via hydrolysis at cocaine benzoyl ester using an efficient cocaine hydrolase (CocH) is known as a promising pharmacotherapeutic approach to CUD treatment. Preclinical and clinical studies on our first CocH (CocH1), in its human serum albumin-fused form known as TV-1380, have demonstrated the promise of a general concept of CocH-based pharmacotherapy for CUD treatment. However, the biological half-life of TV-1380 (t_1/2 = 8 h in rats, associated with t_1/2 = 43-77 h in humans) is not long enough for practical treatment of cocaine dependence, which requires enzyme injection for no more than once weekly. Through protein fusion of a human butyrylcholinesterase mutant (denoted as CocH5) with a mutant (denoted as Fc(M6)) of Fc from human IgG1, we have designed, prepared, and tested a new fusion protein (denoted as CocH5-Fc(M6)) for its pharmacokinetic profile and in vivo catalytic activity against (-)-cocaine. CocH5-Fc(M6) represents the currently most efficient long-acting cocaine hydrolase with both the highest catalytic activity against (-)-cocaine and the longest elimination half-life (t_1/2 = 229 ± 5 h) in rats. As a result, even at a single modest dose of 3 mg/kg, CocH5-Fc(M6) can significantly and effectively accelerate the metabolism of cocaine in rats for at least 60 days. In addition, ∼70 nM CocH5-Fc(M6) in plasma was able to completely block the toxicity and physiological effects induced by intraperitoneal injection of a lethal dose of cocaine (60 mg/kg).

Cocaine hydrolase blocks cocaine-induced dopamine transporter trafficking to the plasma membrane

Cocaine blocks dopamine uptake via dopamine transporter (DAT) on plasma membrane of neuron cells and, as a result, produces the high and induces DAT trafficking to plasma membrane which contributes to the drug seeking or craving. In this study, we first examined the dose dependence of cocaine-induced DAT trafficking and hyperactivity in rats, demonstrating that cocaine at an intraperitoneal dose of 10 mg/kg or higher led to redistribution of most DAT to the plasma membrane while inducing significant hyperactivity in rats. However, administration of 5-mg/kg cocaine (ip) did not significantly induce DAT trafficking or hyperactivity in rats. So the threshold (intraperitoneal) dose of cocaine that can significantly induce DAT trafficking or hyperactivity should be between 5 and 10 mg/kg. These data suggest that when a cocaine dose is high enough to induce significant hyperactivity, it can also significantly induce DAT trafficking to the plasma membrane. Further, the threshold brain cocaine concentration required to induce significant hyperactivity and DAT trafficking was estimated to be ~2.0 ± 0.8 μg/g. Particularly, for treatment of cocaine abuse, previous studies demonstrated that an exogenous cocaine-metabolizing enzyme, for example, CocH3-Fc(M3), can effectively block cocaine-induced hyperactivity. However, it was unknown whether an enzyme could also effectively block cocaine-induced DAT trafficking to the plasma membrane. This study demonstrates, for the first time, that the enzyme is also capable of effectively blocking cocaine from reaching the brain even with a lethal dose of 60-mg/kg cocaine (ip) and, thus, powerfully preventing cocaine-induced physiological effects such as the hyperactivity and DAT trafficking.

Structure and therapeutic uses of butyrylcholinesterase: Application in detoxification, Alzheimer's disease, and fat metabolism

Structural information of butyrylcholinesterase (BChE) and its variants associated with several diseases are discussed here. Pure human BChE has been proved safe and effective in treating organophosphorus (OPs) poisoning and has completed Phase 1 and 2 pharmacokinetic (PK) and safety studies. The introduction of specific mutations into native BChE to endow it a self-reactivating property has gained much progress in producing effective OPs hydrolases. The hydrolysis ability of native BChE on cocaine has been confirmed but was blocked to clinical application due to poor PK properties. Several BChE mutants with elevated cocaine hydrolysis activity were published, some of which have shown safety and efficiency in treating cocaine addiction of human. The increased level of BChE in progressed Alzheimer's disease patients made it a promising target to elevate acetylcholine level and attenuate cognitive status. A variety of selective BChE inhibitors with high inhibitory activity published in recent years are reviewed here. BChE could influence the weight and insulin secretion and resistance of BChE knockout (KO) mice through hydrolyzing ghrelin. The BChE-ghrelin pathway could also regulate aggressive behaviors of BChE-KO mice.

Diagnoses of Pathological States Based on Acetylcholinesterase and Butyrylcholinesterase

Two cholinesterases exist: Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). While AChE plays a crucial role in neurotransmissions, BChE has no specific function apart from the detoxification of some drugs and secondary metabolites from plants. Thus, both AChE and BChE can serve as biochemical markers of various pathologies. Poisoning by nerve agents like sarin, soman, tabun, VX, novichok and overdosing by drugs used in some neurodegenerative disorders like Alzheimer´s disease and myasthenia gravis, as well as poisoning by organophosphorus pesticides are relevant to this issue. But it appears that changes in these enzymes take place in other processes including oxidative stress, inflammation, some types of cancer and genetically conditioned diseases. In this review, the cholinesterases are introduced, the mechanism of inhibitors action is explained and the relations between the cholinesterases and pathologies are explained.

Clinical potential of a rationally engineered enzyme for treatment of cocaine dependence: Long-lasting blocking of the psychostimulant, discriminative stimulus, and reinforcing effects of cocaine

It is a grand challenge to develop a truly effective treatment of substance use disorder (SUD), particularly for cocaine and other drugs without an FDA-approved treatment available, because a truly effective therapy must effectively block the drug's physiological and reinforcing effects during the entire period of treatment in order to achieve the long-time abstinence required by the FDA. Whether a biologic, such as monoclonal antibody, vaccine, or therapeutic enzyme, can be truly effective for SUD treatment or not has been the subject of extensive debate. The main debate question is whether a biologic, particularly an exogenous enzyme, can effectively block the drug's reinforcing effect. In this report, we demonstrate that a modest dose of a recently redesigned long-acting cocaine hydrolase, CocH3-Fc(M6), can be used to effectively block the psychostimulant, discriminative stimulus, and reinforcing effects of cocaine for a sufficiently long period of time. For example, a dose of 3 mg/kg CocH3-Fc(M6) completely blocked the discriminative stimulus and reinforcing effects for 24/25 days and continued to significantly attenuate/decrease the cocaine effects for at least 29 days in rats. All the animal data consistently suggest that the long-acting cocaine hydrolase is a truly promising candidate of enzyme therapy for treatment of cocaine use disorder.

Effects of Cebranopadol on Cocaine-induced Hyperactivity and Cocaine Pharmacokinetics in Rats

Cebranopadol is known as a highly potent analgesic. Recent studies also demonstrated that administration of cebranopadol significantly decreased cocaine self-administration and significantly reduced cue-induced cocaine-seeking behaviors in rats. However, it was unclear whether these interesting behavioral observations are related to any potential effects of cebranopadol on cocaine pharmacokinetics or cocaine-induced hyperactivity. In principle, a promising therapeutic candidate for cocaine dependence treatment may alter the cocaine pharmacokinetics and/or attenuate cocaine-induced reward and hyperactivity and, thus, decrease cocaine self-administration and reduce cue-induced cocaine-seeking behaviors. In this study, we examined possible effects of cebranopadol on cocaine pharmacokinetics and cocaine-induced hyperactivity for the first time. According to our animal data in rats, cebranopadol did not significantly alter the pharmacokinetics of cocaine. According to our more extensive locomotor activity testing data, cebranopadol itself also dose-dependently induced hyperactivity in rats at doses higher than 50 µg/kg. Cebranopadol at a low dose of 25 µg/kg (p.o.) did not induce significant hyperactivity itself, but significantly potentiated cocaine-induced hyperactivity on Days 4 to 7 after the repeated daily dosing of the drug.

Structure-Based Design and Discovery of a Long-Acting Cocaine Hydrolase Mutant with Improved Binding Affinity to Neonatal Fc Receptor for Treatment of Cocaine Abuse

Despite decades of efforts to develop a pharmacotherapy for cocaine abuse treatment, there is still no FDA-approved treatment of diseases associated with this commonly abused drug. Our previously designed highly efficient cocaine hydrolases (CocHs) and the corresponding Fc-fusion proteins (e.g., CocH3-Fc) are recognized as potentially promising therapeutic enzyme candidates for cocaine abuse treatment, but all with limited biological half-lives. In order to prolong the biological half-life and, thus, decrease the required frequency of the enzyme administration for cocaine abuse treatment, we have modeled the Fc-fusion CocH binding with neonatal Fc receptor (FcRn) in the present study. This approach led to the design and testing of CocH3-Fc(M6), a CocH3-Fc mutant with nearly 100-fold increased binding affinity: from K_d = ~ 4 μM to K_d = 43 nM. As a result, CocH3-Fc(M6) indeed revealed a markedly prolonged biological half-life (t_1/2 = 206 ± 7 h or ~ 9 days) in rats, longer than other known Fc-fusion protein drugs such as abatacept and alefacept (for other therapeutic purposes) in the same species (rats). It has been demonstrated that a single dose of 3 mg/kg CocH3-Fc(M6) effectively blocked 20 mg/kg cocaine-induced hyperactivity on day 18 after CocH3-Fc(M6) administration. This is the first attempt to rationally design long-acting Fc-fusion enzyme mutant based on combined computational modeling and experimental measurement of the Fc-fusion CocH binding with FcRn. The similar structure-based design strategy may be used to prolong the biological half-lives of other Fc-fusion protein drugs.

Catalytic activities of cocaine hydrolases against the most toxic cocaine metabolite norcocaethylene

A majority of cocaine users also consume alcohol. The concurrent use of cocaine and alcohol produces the pharmacologically active metabolites cocaethylene and norcocaethylene, in addition to norcocaine. Both cocaethylene and norcocaethylene are more toxic than cocaine itself. Hence, a truly valuable cocaine-metabolizing enzyme for cocaine abuse/overdose treatment should be effective for the hydrolysis of not only cocaine, but also its metabolites norcocaine, cocaethylene, and norcocaethylene. However, there has been no report on enzymes capable of hydrolyzing norcocaethylene (the most toxic metabolite of cocaine). The catalytic efficiency parameters (kcat and KM) of human butyrylcholinesterase (BChE) and two mutants (known as cocaine hydrolases E14-3 and E12-7) against norcocaethylene have been characterized in the present study for the first time, and they are compared with those against cocaine. According to the obtained kinetic data, wild-type human BChE showed a similar catalytic efficiency against norcocaethylene (kcat = 9.5 min-1, KM = 11.7 μM, and kcat/KM = 8.12 × 105 M-1 min-1) to that against (-)-cocaine (kcat = 4.1 min-1, KM = 4.5 μM, and kcat/KM = 9.1 × 105 M-1 min-1). E14-3 and E12-7 showed an improved catalytic activity against norcocaethylene compared to wild-type BChE. E12-7 showed a 39-fold improved catalytic efficiency against norcocaethylene (kcat = 210 min-1, KM = 6.6 μM, and kcat/KM = 3.18 × 107 M-1 min-1). It has been demonstrated that E12-7 as an exogenous enzyme can efficiently metabolize norcocaethylene in rats.

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.

In vivo characterization of toxicity of norcocaethylene and norcocaine identified as the most toxic cocaine metabolites in male mice

BACKGROUND

Majority of cocaine users also consume alcohol, and concurrent use of cocaine and alcohol produces cocaethylene, norcocaine, norcocaethylene, and other non-toxic metabolites. It is essential to know their relative toxicity for development of a truly effective therapeutics for cocaine toxicity treatment.

METHODS

Drug (norcocaethylene or norcocaine)-induced acute toxicity was characterized by the occurrence (and the timing) of prostration, seizure, and death after intraperitoneal administration of the drug (n = 15) using the same strain (Swiss Webster) of male mice reported in previous study by Hearn et al. to determine LD₅₀ of cocaine and cocaethylene. In addition, drug (cocaine, cocaethylene, norcocaine, or norcocaethylene)-induced hyperactivity was determined by locomotor activity testing (n = 8).

RESULTS

According to the animal data, norcocaethylene (LD₅₀=∼39.4 mg/kg) and norcocaine (LD₅₀=∼49.7 mg/kg) are the most toxic metabolites, but they do not induce significant hyperactivity. In addition, the relative toxicity of drugs correlates with the time to the occurrence of prostration/seizure/death after the drug administration.

CONCLUSIONS

The relative toxicity of these toxic drugs can be ranked in this order: norcocaethylene > norcocaine > cocaethylene > cocaine. The data suggest that norcocaethylene, norcocaine, and cocaethylene are all significant contributors to acute toxicity of cocaine in concurrent use of cocaine and alcohol. Hence, future therapeutic development for cocaine toxicity treatment must account for detoxification of these more toxic metabolites. In addition, the relative toxicity of different drugs correlates with the average time to the occurrence of death, seizure, or prostration after the drug administration with a same dose close to their LD₅₀ values.

A latent class analysis of the past-30-day substance use patterns among lifetime cocaine users: Findings from a community sample in North Central Florida

Objectives

Cocaine use is increasing and many cocaine users engage in polysubstance use. Within polysubstance use, relationships among use of individual substances are necessarily complex. To address this complexity, we used latent class analysis (LCA) to identify patterns of polysubstance use among lifetime cocaine users and examine associations among these patterns, demographics, and risk profiles.

Methods

Members of HealthStreet, an ongoing community engagement program, were asked about lifetime and past 30-day use of cocaine, alcohol, tobacco, marijuana, and prescription medications, mental health conditions, recent Emergency Department (ED) visits and demographics. LCA was used to identify classes of past 30-day polysubstance use among individuals who endorsed lifetime cocaine use. Multinomial logistic regression identified factors associated with these classes.

Results

Among 1797 lifetime cocaine users, a five-class LCA model was identified: 1) past 30-day tobacco use only (45%), 2) past 30-day alcohol, marijuana and tobacco use (31%), 3) past 30-day tobacco, prescription opioid and sedative use (13%), 4) past 30-day cocaine, alcohol, marijuana and tobacco use (9%), 5) past 30-day cocaine and multiple polysubstance use (2%). Demographics, ED visits and mental health conditions were associated with class membership.

Conclusions

Approximately 11% of lifetime cocaine users used cocaine in the past 30 days with two different concurrent substance use patterns. Prescription medication (opioids and sedatives) and complex polysubstance use patterns were stronger indicators of negative outcomes than current cocaine use. Cocaine was not used frequently with other stimulants. In addition to polysubstance use, prescription medication use should be targeted for intervention among lifetime cocaine users.

Catalytic Reaction Mechanism for Drug Metabolism in Human Carboxylesterase-1: Cocaine Hydrolysis Pathway

Carboxylesterase-1 (CE-1) is a crucial enzyme responsible for metabolism/activation/inactivation of xenobiotics (therapeutic agents, prodrugs, abused drugs, and organophosphorus nerve agents etc.) and also involved in many other biological processes. In this study, we performed extensive computational modeling and simulations to understand the fundamental reaction mechanism of cocaine hydrolysis catalyzed by CE-1, revealing that CE-1-catalyzed cocaine hydrolysis follows a novel reaction pathway with only two reaction steps: a single-step acylation process and a single-step deacylation process. In the transition states of both single-step processes, the cocaine NH group joins the oxyanion hole to form an additional hydrogen bond with the negatively charged carbonyl oxygen atom of the cocaine. Thus, the transition states are stabilized by both intermolecular and intramolecular hydrogen bonds with the methyl ester of cocaine, specifically the carbonyl oxygen atom. The rate-limiting transition state is associated with the acylation process, and the activation free energy barrier was predicted to be 20.1 kcal/mol. Further, in vitro experimental kinetic analysis was performed for human CE-1-catalyzed cocaine hydrolysis. For CE-1-catalyzed cocaine hydrolysis, the computationally predicted free energy barrier (20.1 kcal/mol) is reasonably close to the experimentally derived turnover number ( k_cat = 0.058 min^-1), indicating the reasonability of the computational results. The obtained novel mechanistic insights are expected to benefit not only CE-1 related rational drug discovery but also future research on the catalytic mechanism of other esterases.

TV-1380 attenuates cocaine-induced changes in cardiodynamic parameters in monkeys and reduces the formation of cocaethylene

BACKGROUND

TV-1380 is a rationally mutated, human BChE fused to human serum albumin that has high hydrolytic enzymatic activity against cocaine and as well as an extended elimination half-life.

OBJECTIVE

The present studies examined the safety of TV-1380 and its protective effect when given to monkeys alone or concomitantly with cocaine and ethanol.

METHODS

A set of studies was conducted in monkeys with TV-1380. The parameters tested included telemetric assessment of cardiovascular parameters, clinical pathology, plasma analysis of cardiac troponin I, ex-vivo analyses of cocaethylene and PK analysis of serum concentrations of TV-1380, cocaine and its metabolites, and histopathological examinations.

RESULTS

TV-1380 treatment in monkeys was well tolerated. TV-1380 pretreatment prior to cocaine significantly attenuated the cardiac effects of cocaine and reduced cocaine-induced elevations in serum cardiac troponin I. TV-1380 changed the metabolic fate of cocaine resulting in decreased exposure to benzoylecgonine, while increasing the exposure to ecgonine methyl ester in plasma.TV-1380 reduced the plasma levels of the toxic metabolite cocaethylene formed after co-administration of ethanol and cocaine.

CONCLUSION

The results of this study demonstrate that TV-1380 not only accelerates the elimination of cocaine, but also protects the treated animal from the cardiac effects of cocaine, and inhibits the formation of the toxic cocaethylene metabolite when cocaine is given together with ethanol, supporting further clinical development of modified BChE products as possible treatments for cocaine abuse.

Effectiveness of a Cocaine Hydrolase for Cocaine Toxicity Treatment in Male and Female Rats

Development of a truly effective medication for treatment of cocaine abuse has been a grand challenge. There is no FDA-approved therapeutic agent specific for cocaine addiction or overdose. An enzyme therapy using an efficient cocaine-metabolizing enzyme could be a promising treatment strategy for cocaine overdose and addiction. One of our previously designed cocaine hydrolases (CocHs), known as CocH1, was fused with human serum albumin (HSA) to prolong the biological half-life. The fusion protein CocH1-HSA is an investigational new drug (IND) approved by the FDA for clinical trials in cocaine addiction treatment, but not in cocaine overdose/toxicity treatment. In the present study, we aimed to evaluate the pharmacokinetic profile of CocH1-HSA and its effectiveness for cocaine toxicity treatment in male and female rats and demonstrate the clinical potential. The data demonstrate that enzyme CocH1-HSA has very similar pharmacokinetic profile in male and female rats. For both male and female rats, the enzyme can rapidly eliminate cocaine even if the cocaine dose is as high as 180 mg/kg (LD₁₀₀). Based on the animal data, whenever the enzyme is given to a living subject, the remaining cocaine in the body will be converted rapidly to physiologically inactive metabolites and, thus, reverse the cocaine toxicity and help the subject to recover. So, an enzyme therapy using CocH1-HSA can effectively treat cocaine toxicity and prevent the subject from further damage by cocaine. The data obtained clearly demonstrate the promising clinical potential of CocH1-HSA in cocaine overdose treatment for both genders.

A quantitative LC-MS/MS method for simultaneous determination of cocaine and its metabolites in whole blood

As new metabolic pathways of cocaine were recently identified, a high performance liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed to simultaneously determine cocaine and nine cocaine-related metabolites in whole blood samples. One-step solid phase extraction was used to extract all of the ten compounds and corresponding internal standards from blood samples. All compounds and internal standards extracted were separated on an Atlantis T3 (100Å, 3μm, 2.1mm×150mm I.D) column and detected in positive ion and high sensitivity mode with multiple reaction monitoring. This method was validated for its sensitivity, linearity, specificity, accuracy, precision, recovery, and stability. All of the ten compounds were quantifiable ranging from the lower limit of quantification (LLOQs) of ∼10nM (1.9-3.2ng/ml) to ∼1000nM (190-320ng/ml) without any interfering substance. Accuracy and precision were determined, and both of them were within the acceptance criteria of the United States (US) Food and Drug Administration (FDA) and European Medicines Agency (EMA) guidelines. The recovery was above 66.7% for all compounds. Stability tests demonstrated the stability of compounds under different storage conditions in whole blood samples. The method was successfully applied to a pharmacokinetic study with co-administration of cocaine and alcohol in rats.

Potential anti-obesity effects of a long-acting cocaine hydrolase

A long-acting cocaine hydrolase, known as CocH3-Fc(M3), engineered from human butyrylcholinesterase (BChE) was tested, in this study, for its potential anti-obesity effects. Mice on a high-fat diet gained significantly less body weight when treated weekly with 1 mg/kg CocH3-Fc(M3) compared to control mice, though their food intake was similar. There is no correlation between the average body weight and the average food intake, which is consistent with the previously reported observation in BChE knockout mice. In addition, molecular modeling was carried out to understand how ghrelin binds with CocH3, showing that ghrelin binds with CocH3 in a similar mode as ghrelin binding with wild-type human BChE. The similar binding structures explains why CocH3 and BChE have similar catalytic activity against ghrelin.

Metabolic Enzymes of Cocaine Metabolite Benzoylecgonine

Cocaine is one of the most addictive drugs without a U.S. Food and Drug Administration (FDA)-approved medication. Enzyme therapy using an efficient cocaine-metabolizing enzyme is recognized as the most promising approach to cocaine overdose treatment. The actual enzyme, known as RBP-8000, under current clinical development for cocaine overdose treatment is our previously designed T172R/G173Q mutant of bacterial cocaine esterase (CocE). The T172R/G173Q mutant is effective in hydrolyzing cocaine but inactive against benzoylecgonine (a major, biologically active metabolite of cocaine). Unlike cocaine itself, benzoylecgonine has an unusually stable zwitterion structure resistant to further hydrolysis in the body and environment. In fact, benzoylecgonine can last in the body for a very long time (a few days) and, thus, is responsible for the long-term toxicity of cocaine and a commonly used marker for drug addiction diagnosis in pre-employment drug tests. Because CocE and its mutants are all active against cocaine and inactive against benzoylecgonine, one might simply assume that other enzymes that are active against cocaine are also inactive against benzoylecgonine. Here, through combined computational modeling and experimental studies, we demonstrate for the first time that human butyrylcholinesterase (BChE) is actually active against benzoylecgonine, and that a rationally designed BChE mutant can not only more efficiently accelerate cocaine hydrolysis but also significantly hydrolyze benzoylecgonine in vitro and in vivo. This sets the stage for advanced studies to design more efficient mutant enzymes valuable for the development of an ideal cocaine overdose enzyme therapy and for benzoylecgonine detoxification in the environment.

Long-acting cocaine hydrolase for addiction therapy

Cocaine abuse is a world-wide public health and social problem without a US Food and Drug Administration-approved medication. An ideal anticocaine medication would accelerate cocaine metabolism, producing biologically inactive metabolites by administration of an efficient cocaine-specific exogenous enzyme. Our recent studies have led to the discovery of the desirable, highly efficient cocaine hydrolases (CocHs) that can efficiently detoxify and inactivate cocaine without affecting normal functions of the CNS. Preclinical and clinical data have demonstrated that these CocHs are safe for use in humans and are effective for accelerating cocaine metabolism. However, the actual therapeutic use of a CocH in cocaine addiction treatment is limited by its short biological half-life (e.g., 8 h or shorter in rats). Here we demonstrate a novel CocH form, a catalytic antibody analog, which is a fragment crystallizable (Fc)-fused CocH dimer (CocH-Fc) constructed by using CocH to replace the Fab region of human IgG1. The CocH-Fc not only has a high catalytic efficiency against cocaine but also, like an antibody, has a considerably longer biological half-life (e.g., ∼107 h in rats). A single dose of CocH-Fc was able to accelerate cocaine metabolism in rats even after 20 d and thus block cocaine-induced hyperactivity and toxicity for a long period. Given the general observation that the biological half-life of a protein drug is significantly longer in humans than in rodents, the CocH-Fc reported in this study could allow dosing once every 2-4 wk, or longer, for treatment of cocaine addiction in humans.

Kinetic characterization of a cocaine hydrolase engineered from mouse butyrylcholinesterase

Mouse butyrylcholinesterase (mBChE) and an mBChE-based cocaine hydrolase (mCocH, i.e. the A¹⁹⁹S/S²²⁷A/S²⁸⁷G/A³²⁸W/Y³³²G mutant) have been characterized for their catalytic activities against cocaine, i.e. naturally occurring (-)-cocaine, in comparison with the corresponding human BChE (hBChE) and an hBChE-based cocaine hydrolase (hCocH, i.e. the A¹⁹⁹S/F²²⁷A/S²⁸⁷G/A³²⁸W/Y³³²G mutant). It has been demonstrated that mCocH and hCocH have improved the catalytic efficiency of mBChE and hBChE against (-)-cocaine by ~8- and ~2000-fold respectively, although the catalytic efficiencies of mCocH and hCocH against other substrates, including acetylcholine (ACh) and butyrylthiocholine (BTC), are close to those of the corresponding wild-type enzymes mBChE and hBChE. According to the kinetic data, the catalytic efficiency (k(cat)/K(M)) of mBChE against (-)-cocaine is comparable with that of hBChE, but the catalytic efficiency of mCocH against (-)-cocaine is remarkably lower than that of hCocH by ~250-fold. The remarkable difference in the catalytic activity between mCocH and hCocH is consistent with the difference between the enzyme-(-)-cocaine binding modes obtained from molecular modelling. Further, both mBChE and hBChE demonstrated substrate activation for all of the examined substrates [(-)-cocaine, ACh and BTC] at high concentrations, whereas both mCocH and hCocH showed substrate inhibition for all three substrates at high concentrations. The amino-acid mutations have remarkably converted substrate activation of the enzymes into substrate inhibition, implying that the rate-determining step of the reaction in mCocH and hCocH might be different from that in mBChE and hBChE.