Metabolic Enzymes of Cocaine Metabolite Benzoylecgonine

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.

Catalytic activities of a highly efficient cocaine hydrolase for hydrolysis of biologically active cocaine metabolites norcocaine and benzoylecgonine

Cocaine is a widely abused, hepatotoxic drug without an FDA-approved pharmacotherapy specific for cocaine addiction or overdose. It is recognized as a promising therapeutic strategy to accelerate cocaine metabolism which can convert cocaine to pharmacologically inactive metabolite(s) using an efficient cocaine-metabolizing enzyme. Our previous studies have successfully designed and discovered a highly efficient cocaine hydrolase, denoted as CocH5-Fc(M6), capable of rapidly hydrolyzing cocaine at the benzoyl ester moiety. In the present study, we determined the kinetic parameters of CocH5-Fc(M6) against norcocaine (k_cat = 9,210 min^-1, K_M = 20.9 μM, and k_cat/K_M = 1.87 × 10⁵ min^-1 M^-1) and benzoylecgonine (k_cat = 158 min^-1, K_M = 286 μM, and k_cat/K_M = 5.5 × 10⁵ min^-1 M^-1) for the first time. Further in vivo studies have demonstrated that CocH5-Fc(M6) can effectively accelerate clearance of not only cocaine, but also norcocaine (known as a cocaine metabolite which is more toxic than cocaine itself) and benzoylecgonine (known as an unfavorable long-lasting metabolite with some long-term toxicity concerns) in rats. Due to the desired high catalytic activity against norcocaine, CocH5-Fc(M6) is capable of quickly detoxifying both cocaine and its more toxic metabolite norcocaine after intraperitoneally administering lethal dose of 60 or 180 mg/kg cocaine. In addition, the ability of CocH5-Fc(M6) to accelerate clearance of benzoylecgonine should also be valuable for the use of CocH5-Fc(M6) in treatment of cocaine use disorder.

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.

Cocaine use associated gut permeability and microbial translocation in people living with HIV in the Miami Adult Study on HIV (MASH) cohort

OBJECTIVE

Determine if cocaine use impacts gut permeability, promotes microbial translocation and immune activation in people living with HIV (PLWH) using effective antiretroviral therapy (ART).

METHODS

Cross-sectional analysis of 100 PLWH (ART ≥6 months, HIV-RNA <200 copies/mL) from the Miami Adult Studies on HIV (MASH) cohort. Cocaine use was assessed by self-report, urine screen, and blood benzoylecgonine (BE). Blood samples were collected to assess gut permeability (intestinal fatty acid-binding protein, I-FABP), microbial translocation (lipopolysaccharide, LPS), immune activation (sCD14, sCD27, and sCD163) and markers of inflammation (hs-CRP, TNF-α and IL-6). Multiple linear regression models were used to analyze the relationships of cocaine use.

RESULTS

A total of 37 cocaine users and 63 cocaine non-users were evaluated. Cocaine users had higher levels of I-FABP (7.92±0.35 vs. 7.69±0.56 pg/mL, P = 0.029) and LPS (0.76±0.24 vs. 0.54±0.27 EU/mL, P<0.001) than cocaine non-users. Cocaine use was also associated with the levels of LPS (P<0.001), I-FABP (P = 0.033), and sCD163 (P = 0.010) after adjusting for covariates. Cocaine users had 5.15 times higher odds to exhibit higher LPS levels than non-users (OR: 5.15 95% CI: 1.89-13.9; P<0.001). Blood levels of BE were directly correlated with LPS (rho = 0.276, P = 0.028), sCD14 (rho = 0.274, P = 0.031), and sCD163 (rho = 0.250, P = 0.049).

CONCLUSIONS

Cocaine use was associated with markers of gut permeability, microbial translocation, and immune activation in virally suppressed PLWH. Mitigation of cocaine use may prevent further gastrointestinal damage and immune activation in PLWH.

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).

Cocaethylene, simultaneous alcohol and cocaine use, and liver fibrosis in people living with and without HIV

BACKGROUND

The simultaneous consumption of cocaine and alcohol results in the production of cocaethylene (CE) in the liver, a highly toxic metabolite. Prior research suggests that cocaine use contributes to liver disease and its concomitant use with alcohol may increase its hepatotoxicity, but studies in humans are lacking. We evaluated the role of cocaine, its simultaneous use with alcohol, and CE on liver fibrosis.

METHODS

We performed a cross-sectional analysis of the Miami Adult Studies on HIV (MASH) cohort. Cocaine use was determined via self-report, urine screen, and blood metabolites, using liquid chromatography with tandem mass spectrometry. Hazardous drinking was determined with the AUDIT-C and liver fibrosis with the Fibrosis-4 Index (FIB-4).

RESULTS

Out of 649 participants included in this analysis, 281 (43.3%) used cocaine; of those, 78 (27.8%) had CE in blood. Cocaine users with CE had higher concentrations of cocaine metabolites in blood and were more likely to drink hazardously than cocaine users without CE and cocaine non-users. Overall, cocaine use was associated with liver fibrosis. CE in blood was associated with 3.17 (95% CI: 1.61, 6.23; p = 0.0008) times the odds of liver fibrosis compared to cocaine non-users, adjusting for covariates including HIV and HCV infection. The effect of CE on liver fibrosis was significantly greater than that of cocaine or alcohol alone.

CONCLUSIONS

CE is a reliable marker of simultaneous use of cocaine and alcohol that may help identify individuals at risk of liver disease and aid in the prevention of its development or progression.

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.

Computational Design and Crystal Structure of a Highly Efficient Benzoylecgonine Hydrolase

Benzoylecgonine (BZE) is the major toxic metabolite of cocaine and is responsible for the long-term cocaine-induced toxicity owing to its long residence time in humans. BZE is also the main contaminant following cocaine consumption. Here, we identified the bacterial cocaine esterase (CocE) as a BZE-metabolizing enzyme (BZEase), which can degrade BZE into biological inactive metabolites (ecgonine and benzoic acid). CocE was redesigned by a reactant-state-based enzyme design theory. An encouraging mutant denoted as BZEase2, presented a >400-fold improved catalytic efficiency against BZE compared with wild-type (WT) CocE. In vivo, a single dose of BZEase2 (1 mg kg^-1 , IV) could eliminate nearly all BZE within only two minutes, suggesting the enzyme has the potential for cocaine overdose treatment and BZE elimination in the environment by accelerating BZE clearance. The crystal structure of a designed BZEase was also determined.

Pharmacokinetic and pharmacodynamic analyses of cocaine and its metabolites in behaviorally divergent inbred mouse strains

Cocaine (COC) is a psychostimulant with a high potential for abuse and addiction. Risk for COC use disorder is driven, in part, by genetic factors. Animal models of addiction-relevant behaviors have proven useful for studying both genetic and nongenetic contributions to drug response. In a previous study, we examined initial locomotor sensitivity to COC in genetically diverse inbred mouse strains. That work highlighted the relevance of pharmacokinetics (PK) in initial locomotor response to COC but was limited by a single dose and two sampling points. The objective of the present study was to characterize the PK and pharmacodynamics of COC and its metabolites (norcocaine and benzoylecgonine) in six inbred mouse strains (I/LnJ, C57BL/6J, FVB/NJ, BTBR T+ tf/J, LG/J and LP/J) that exhibit extreme locomotor responses to cocaine. Mice were administered COC at one of four doses and concentrations of cocaine, norcocaine and benzoylecgonine were analyzed in both plasma and brain tissue at 5 different time points. Initial locomotor sensitivity to COC was used as a pharmacodynamic endpoint. We developed an empirical population PK model that simultaneously characterizes cocaine, norcocaine and benzoylecgonine in plasma and brain tissues. We observed interstrain variability occurring in the brain compartment that may contribute to pharmacodynamic differences among select strains. Our current work paves the way for future studies to explore strain-specific pharmacokinetic differences and identify factors other than PK that are responsible for the diverse behavioral response to COC across these inbred mouse strains.

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.

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.

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.

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.