Effects of murine-derived anti-methamphetamine monoclonal antibodies on (+)-methamphetamine self-administration in the rat

Immunotherapies for the Treatment of Drug Addiction

Substance use disorders (SUD) are a serious public health concern globally. Existing treatment platforms suffer from a lack of effectiveness. The development of immunotherapies against these substances of abuse for both prophylactic and therapeutic use has gained tremendous importance as an alternative and/or supplementary to existing therapies. Significant development has been made in this area over the last few decades. Herein, we highlight the vaccine and other biologics development strategies, preclinical, clinical updates along with challenges and future directions. Articles were searched in PubMed, ClinicalTrial.gov, and google electronic databases relevant to development, preclinical, clinical trials of nicotine, cocaine, methamphetamine, and opioid vaccines. Various new emerging vaccine development strategies for SUD were also identified through this search and discussed. A good number of vaccine candidates demonstrated promising results in preclinical and clinical phases and support the concept of developing a vaccine for SUD. However, there have been no ultimate success as yet, and there remain some challenges with a massive push to take more candidates to clinical trials for further evaluation to break the bottleneck.

Active and Passive Immunization with an Anti-Methamphetamine Vaccine Attenuates the Behavioral and Cardiovascular Effects of Methamphetamine

BACKGROUND

Methamphetamine use disorder (MUD) is a growing health concern with no FDA-approved treatment. The present series of studies build upon our previous work developing an anti-methamphetamine (MA) vaccine for MUD. We determined the effects of a formulation that included tetanus-toxoid (TT) conjugated to succinyl-methamphetamine (TT-SMA) adsorbed onto aluminum hydroxide (alum) in combination with the novel Toll-Like Receptor-5 agonist, entolimod.

METHODS

Mice were vaccinated (0, 3, 6 weeks) with TT-SMA+alum and various doses of entolimod to determine an optimal dose for enhancing immunogenicity against MA. Functional effects were then assessed using MA-induced locomotor activation in mice. Experiments using passive immunization of antibodies generated by the vaccine tested its ability to attenuate MA-induced cardiovascular effects and alter the reinforcing effects of MA in an MA-induced reinstatement of a drug seeking model of relapse in male and female rats.

RESULTS

Antibody levels peaked at 10 weeks following vaccination with TT-SMA+alum combined with entolimod (1, 3 and 10 μg). MA-induced locomotor activation was significantly attenuated in vaccinated vs. unvaccinated mice and antibody levels significantly correlated with ambulation levels. Passive immunization decreased mean arterial pressure following MA dosing in rats of both sexes but did not alter heart rate. Passive immunization also attenuated the ability of MA to reinstate extinguished drug-seeking behavior in male and female rats. Results support further development of this vaccine for relapse prevention for individuals with MUD.

Immune to addiction: how immunotherapies can be used to combat methamphetamine addiction

Introduction: The concept of anti-methamphetamine (METH) immunotherapies is a few decades old. A substantial amount of information has been generated on the development of anti-METH immunotherapies, particularly in the preclinical stages of development of vaccines and monoclonal antibody (mAb) treatments. However, the concept of treating METH use addiction with anti-METH immunotherapies is not well understood by many researchers or general readers. A series of questions commonly arise regarding the concept: how does it work? What is the antigen used? How exactly does the vaccine prevent METH addiction?Areas covered: This paper reviews the published articles relating to the mechanisms of METH use disorders, strategies used in the development of anti-METH immunotherapies, and the mechanism of action of these treatments. It provides clear explanations to questions surrounding the basis of anti-METH immunotherapies and contextualizes their development. It also identifies areas for future investigation to speed their translation into clinical use.Expert opinion: While METH immunotherapies, including vaccines and mAbs, have progressed significantly in the last 30 years, there are newer approaches that should be evaluated to improve their translatability. Approaches including nanoparticle vaccines, virus-like particles, and other novel methods should be fully evaluated as means of generating anti-METH immunity.

Immunopharmacotherapeutic advancements in addressing methamphetamine abuse

Methamphetamine (METH) is an illicit psychostimulant that is known to account for substance abuse disorders globally, second only to opioids, yet has no approved pharmacotherapies. Traditional therapies employ small molecule agonists or antagonists for substance use disorders or overdose reversal by targeting drug-specific receptors in the brain. However, the comprehensive mechanism of METH on multiple sites within the central nervous system (CNS) implies its receptors lack the high affinity and specificity required for an "ideal" drug target. The alternative to pharmacotherapies is to sequester abused drugs in the periphery, effectively eliminating the effects from CNS receptor occupation through pharmacokinetic antagonism. This review presents updates on immunopharmacotherapeutic advancements in addressing methamphetamine abuse by focusing on the cultivation of research optimization strategies regarding hapten chemistry, carrier proteins, and adjuvants implemented in active immunization. Furthermore, we discuss necessary developments for each component of active immunopharmacotherapies and the future of active vaccines in treating METH use disorder.

Vaccine development against methamphetamine drug addiction

INTRODUCTION

There are currently no effective treatments for Methamphetamine (METH) addiction and psychotherapy remains the sole treatment option. The development of immunopharmacotherapies for the treatment of drug addiction, overdose, and relapse management appears to be promising alternative and a significant body of information has been generated using various vaccine development strategies. Herein, we present an update on the developments toward anti-METH vaccines and their study outcomes in preclinical and clinical studies.

AREAS COVERED

The scope of this article is to present an update on METH vaccine development strategies such as active vaccination through hapten design and the passive immunization through monoclonal antibodies along with preclinical and clinical studies. The relevant literatures and clinical trial outcomes were searched in databases including Google, Google Scholar, PubMed, Science Direct, ClinicalTrials.gov, and www.anzctr.org.au using specific keywords.

EXPERT OPINION

Significant improvements have been developed for immunopharmacotherapies for METH addiction over the last two decades. However, only one monoclonal antibody candidate has been evaluated in a phase I clinical trial. At this moment, it is essential to evaluate the safety and efficacy of potential candidates in clinical trials to validate the importance of this platform drug-vaccine conjugation in order to manage or overcome METH addiction.

Effects of a methamphetamine vaccine, IXT-v100, on methamphetamine-related behaviors

RATIONALE

Vaccines have been developed as a potential treatment for methamphetamine (meth) use disorder (MUD). Immunization with the meth vaccine IXT-v100 has previously been shown to elicit antibodies with high affinity for meth and thus may be an effective treatment for MUD.

OBJECTIVES

These studies were designed to determine the efficacy of IXT-v100 on meth-taking and meth-seeking behaviors in rats.

METHODS

In the acquisition and maintenance study, male and female rats were trained to self-administer meth (0.06 mg/kg/infusion) over an 8-week period following vaccination. In the last 4 weeks, the dose of meth was increased or decreased each week. To assess meth-seeking behavior, the meth-primed reactivity model was used. Rats were trained to self-administer meth for 5 weeks, followed by a 5-week or 11-week forced abstinence period during which the animals were vaccinated. Rats were then placed back into the self-administration chamber immediately after being injected with meth (1 mg/kg, i.p.) but did not receive meth during the session. Responses were recorded and used as a measure of meth seeking.

RESULTS

Results from the acquisition and maintenance study in Wistar rats show that vaccination with IXT-v100 adjuvanted with glucopyranosyl lipid A stable emulsion decreases the percentage of animals that will self-administer a moderate level of meth. In the meth-primed reactivity studies, results from males showed that vaccination significantly attenuates meth-seeking behavior.

CONCLUSION

Together, these results suggest vaccination with IXT-v100 may be effective at decreasing meth-taking and meth-seeking behaviors in humans suffering with MUD.

Investigation of the reinforcing potential of samidorphan and naltrexone by fixed and progressive ratio intravenous self-administration testing in heroin-maintained rats

BACKGROUND

Samidorphan is a novel μ-opioid antagonist with low intrinsic activity at κ- and δ-opioid receptors.

AIMS

Because samidorphan is central nervous system-active, we investigated whether samidorphan (13.6, 40.8, 68 μg/kg/injection) served as a positive reinforcer in rats trained to self-administer heroin on a fixed ratio-5 schedule. Samidorphan's relative reinforcing effect was evaluated by progressive ratio/break-point determination. Naltrexone (13.6, 40.8, 68 μg/kg/injection) and heroin (7.5, 15, 25 μg/kg/injection) were comparators.

RESULTS

All heroin doses maintained self-administration on fixed ratio-5 and progressive ratio/break-points at levels significantly greater than saline. Samidorphan and naltrexone had similar profiles on fixed ratio-5 with one samidorphan dose serving as a positive reinforcer and one naltrexone dose showing a strong trend ( p=0.053) for positive reinforcement. The numbers of injections of every samidorphan and naltrexone dose were significantly lower than all heroin doses. The numbers of self-administered samidorphan and naltrexone injections/session on fixed ratio-5 were not significantly different from one another. The mean inter-injection intervals for heroin were significantly shorter than for saline, whereas those of samidorphan and naltrexone were not. Progressive ratio break-points for samidorphan and naltrexone were not different from saline except for the highest dose of samidorphan. In addition, the progressive ratio break-points for samidorphan were not significantly different from those of naltrexone and were significantly lower than heroin. The samidorphan unit-doses evaluated in self-administration yielded plasma concentrations ranging between 25-109% and 10-45% of the maximum concentration values in humans.

CONCLUSIONS

Overall, the profiles of samidorphan and naltrexone, which has no abuse liability, were similar in this model.

Development and testing of AAV-delivered single-chain variable fragments for the treatment of methamphetamine abuse

Methamphetamine (METH) substance abuse disorders have major impact on society, yet no medications have proven successful at preventing METH relapse or cravings. Anti-METH monoclonal antibodies can reduce METH brain concentrations; however, this therapy has limitations, including the need for repeated dosing throughout the course of addiction recovery. An adeno-associated viral (AAV)-delivered DNA sequence for a single-chain variable fragment could offer long-term, continuous expression of anti-METH antibody fragments. For these studies, we injected mice via tail vein with 1 x 10¹² vector genomes of two AAV8 scFv constructs and measured long-term expression of the antibody fragments. Mice expressed each scFv for at least 212 days, achieving micromolar scFv concentrations in serum. In separate experiments 21 days and 50 days after injecting mice with AAV-scFvs mice were challenged with METH in vivo. The circulating scFvs were capable of decreasing brain METH concentrations by up to 60% and sequestering METH in serum for 2 to 3 hrs. These results suggest that AAV-delivered scFv could be a promising therapy to treat methamphetamine abuse.

Conjugate Vaccine Immunotherapy for Substance Use Disorder

Substance use disorder, especially in relation to opioids such as heroin and fentanyl, is a significant public health issue and has intensified in recent years. As a result, substantial interest exists in developing therapeutics to counteract the effects of abused drugs. A promising universal strategy for antagonizing the pharmacology of virtually any drug involves the development of a conjugate vaccine, wherein a hapten structurally similar to the target drug is conjugated to an immunogenic carrier protein. When formulated with adjuvants and immunized, the immunoconjugate should elicit serum IgG antibodies with the ability to sequester the target drug to prevent its entry to the brain, thereby acting as an immunoantagonist. Despite the failures of first-generation conjugate vaccines against cocaine and nicotine in clinical trials, second-generation vaccines have shown dramatically improved performance in preclinical models, thus renewing the potential clinical utility of conjugate vaccines in curbing substance use disorder. This review explores the critical design elements of drug conjugate vaccines such as hapten structure, adjuvant formulation, bioconjugate chemistry, and carrier protein selection. Methods for evaluating these vaccines are discussed, and recent progress in vaccine development for each drug is summarized.

Recombinant Adeno-Associated Virus-Mediated Expression of Methamphetamine Antibody Attenuates Methamphetamine-Induced Hyperactivity in Mice

Methamphetamine (Meth) is one of the most frequently abused drugs worldwide. Recent studies have indicated that antibodies with high affinity for Meth reduce its pharmacological effects. The purpose of this study was to develop a technique for virus-based passive immunization against Meth effects. We generated a recombinant adeno-associated virus serotype-8 vector (AAV-MethAb) carrying the gene for a Meth-specific monoclonal antibody (MethAb). Infection of 293 cells with AAV-MethAb resulted in the expression and secretion of antibodies which bind to Meth. The viral vector was then examined in adult ICR mice. Systemic administration of AAV-MethAb resulted in long-term expression of MethAb in the serum for up to 29 weeks. Serum collected from the animals receiving AAV-MethAb retained a high specificity for (+)-Meth. Animals were challenged with Meth five weeks after viral injection. Meth levels in the brain and serum were reduced while Meth-induced locomotor activity was significantly attenuated. In conclusion, AAV-MethAb administration effectively depletes Meth from brain and serum while reducing the behavioral response to Meth, and thus is a potential therapeutic approach for Meth abuse.

The pharmacokinetics of methamphetamine self-administration in male and female rats

BACKGROUND

Because methamphetamine (METH) pharmacokinetics after single iv doses show significant differences between male and female rats, we hypothesized that pharmacokinetic differences in METH disposition could be a contributing factor to the patterns of METH self-administration behaviors in rats.

METHODS

For the studies, we used a passive (non-contingent) METH dosing schedule consisting of 27 METH iv bolus injections (0.048mg/kg) over 2h derived from a previous active (contingent) METH self-administration behavioral study in male rats. After METH dosing of male and female Sprague-Dawley rats (n=5/group), METH and amphetamine serum concentrations were determined by LC-MS/MS. Pharmacokinetic analysis, including predictive mathematical simulations of the data, was then conducted.

RESULTS

Male and female rats achieved relatively stable METH serum concentrations within 20min, which remained constant from 20 to 120min. While not statistically different, METH clearance and volume of distribution values for females were 25% and 33% lower (respectively) than males. Linear regression analysis of predicted METH concentrations from pharmacokinetic simulations versus observed concentrations showed a substantially better correlation with male data than female data (r(2)=0.71 vs. 0.56; slope=0.95 vs. 0.45, respectively). At 120min, the time of predicted peak METH serum concentrations, female values were 42% higher than expected, while male values were within 3%.

CONCLUSIONS

Unlike METH male pharmacokinetic data, the female data was less predictable during multiple METH administrations and produced overall higher than expected METH concentrations. These findings demonstrate that METH pharmacokinetics could contribute to differences in METH self-administration behaviors in rats.

The anti-(+)-methamphetamine monoclonal antibody mAb7F9 attenuates acute (+)-methamphetamine effects on intracranial self-stimulation in rats

Passive immunization with monoclonal antibodies (mAbs) against (+)-methamphetamine (METH) is being evaluated for the treatment of METH addiction. A human/mouse chimeric form of the murine anti-METH mAb7F9 has entered clinical trials. This study examined the effects of murine mAb7F9 on certain addiction-related behavioral effects of METH in rats as measured using intracranial self-stimulation (ICSS). Initial studies indicated that acute METH (0.1-0.56 mg/kg, s.c.) lowered the minimal (threshold) stimulation intensity that maintained ICSS. METH (0.3 mg/kg, s.c.) also blocked elevations in ICSS thresholds (anhedonia-like behavior) during spontaneous withdrawal from a chronic METH infusion (10 mg/kg/day x 7 days). In studies examining effects of i.v. pretreatment with mAb7F9 (at 30, 100, or 200 mg/kg), 200 mg/kg blocked the ability of an initial injection of METH (0.3 mg/kg, s.c.) to reduce baseline ICSS thresholds, but was less capable of attenuating the effect of subsequent daily injections of METH. MAb7F9 (200 mg/kg) also produced a small but significant reduction in the ability of METH (0.3 mg/kg, s.c.) to reverse METH withdrawal-induced elevations in ICSS thresholds. These studies demonstrate that mAb7F9 can partially attenuate some addiction-related effects of acute METH in an ICSS model, and provide some support for the therapeutic potential of mAb7F9 for the treatment of METH addiction.

Pharmacological effects of two anti-methamphetamine monoclonal antibodies. Supporting data for lead candidate selection for clinical development

This lead candidate selection study compared two anti-(+)-methamphetamine (METH) monoclonal antibodies (mAb) to determine their ability to reduce METH-induced locomotor effects and redistribute METH and (+)-amphetamine (AMP) in a preclinical overdose model. Both mAbs have high affinity for METH, but mAb4G9 has moderate and mAb7F9 has low affinity for AMP. In the placebo-controlled behavioral experiment, the effects of each mAb on the locomotor response to a single 1 mg/kg intravenous (IV) METH dose were determined in rats. The doses of mAb binding sites were administered such that they equaled 1, 0.56, 0.32, and 0.1 times the molar equivalent (mol-eq) of METH in the body 30 min after the METH dose. METH disposition was determined in separate animals that similarly received either a 1 or 0.32 mol-eq dose of mAb binding sites 30 min after a 1 mg/kg METH dose. Total METH-induced distance traveled was significantly reduced in rats that received the highest three doses of each mAb compared with saline. The duration of METH effects was also significantly reduced by mAb7F9 at the highest dose. The disposition of METH was altered dose-dependently by both mAbs as shown in reductions of volume of distribution and total clearance, and increases in elimination half-life. These data indicate that both mAbs are effective at reducing METH-induced behavior and favorably altering METH disposition. Both were therefore suitable for further preclinical testing as potential human medications for treating METH use; however, due to results reported here and in later studies, mAb7F9 was selected for clinical development.

Future pharmacological treatments for substance use disorders

Substance use disorders represent a serious public health and social issue worldwide. Recent advances in our understanding of the neurobiological basis of the addictive processes have led to the development of a growing number of pharmacological agents to treat addictions. Despite this progress, there are no approved pharmacological treatments for cocaine, methamphetamine and cannabis addiction. Moving treatment development to the next stage will require novel ways of approaching substance use disorders. One such novel approach is to target individual vulnerabilities, such as cognitive function, sex differences and psychiatric comorbidities. This review provides a summary of promising pharmacotherapies for alcohol, opiate, stimulant and nicotine addictions. Many medications that target positive and negative reinforcement of drugs, as well as individual vulnerabilities to addiction, are in different phases of development. Clinical trials testing the efficacy of these medications for substance use disorder are warranted.

Vaccines against stimulants: cocaine and MA

While the worldwide prevalence of cocaine use remains significant, medications, or small molecule approaches, to treat drug addictions have met with limited success. Anti-addiction vaccines, on the other hand, have demonstrated great potential for treating drug abuse using a distinctly different mechanism of eliciting an antibody response that blocks the pharmacological effects of drugs. We provide a review of vaccine-based approaches to treating stimulant addictions; specifically and cocaine addictions. This selective review article focuses on the one cocaine vaccine that has been into clinical trials and presents new data related to pre-clinical development of a methamphetamine (MA) vaccine. We also review the mechanism of action for vaccine induced antibodies to abused drugs, which involves kinetic slowing of brain entry as well as simple blocking properties. We present pre-clinical innovations for MA vaccines including hapten design, linkage to carrier proteins and new adjuvants beyond alum. We provide some new information on hapten structures and linkers and variations in protein carriers. We consider a carrier, outer membrance polysaccharide coat protein (OMPC), that provides some self-adjuvant through lipopolysaccharide components and provide new results with a monophosopholipid adjuvant for the more standard carrier proteins with cocaine and MA. The review then covers the clinical trials with the cocaine vaccine TA-CD. The clinical prospects for advances in this field over the next few years include a multi-site cocaine vaccine clinical trial to be reported in 2013 and phase 1 clinical trials of a MA vaccine in 2014.

Effects of an oxycodone conjugate vaccine on oxycodone self-administration and oxycodone-induced brain gene expression in rats

Prescription opioid abuse is an increasing public health concern in the USA. A vaccine comprising a hapten (OXY) conjugated to the carrier protein keyhole limpet hemocyanin (OXY-KLH) has been shown to attenuate the antinociceptive effects of oxycodone. Here, the vaccine's ability to prevent acquisition of intravenous (i.v.) oxycodone self-administration was studied in rats. Effects of vaccination on oxycodone-induced changes in the expression of several genes within the mesolimbic system, which are regulated by chronic opiate use, were also examined. Vaccination with OXY-KLH reduced the proportion of rats acquiring i.v. self-administration of oxycodone under a fixed ratio (FR) 3 schedule of reinforcement compared to control rats immunized with the unconjugated KLH carrier protein. Vaccination significantly reduced the mean number of infusions at FR3, total number of infusions, and total oxycodone intake during the entire protocol. Compared to oxycodone self-administering control rats immunized with the carrier alone, rats vaccinated with the OXY-KLH immunogen showed increased levels of adenylate cyclase 5 (Adcy5) and decreased levels of early growth response protein 2 (Egr2) and the early immediate gene c-Fos in the striatum. These data suggest that vaccination with OXY-KLH can attenuate the reinforcing effects of oxycodone at a clinically-relevant exposure level. Analysis of mRNA expression identified some addiction-relevant markers that may be of interest in understanding oxycodone effects or the protection provided by vaccination.

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.

Treatment with a monoclonal antibody against methamphetamine and amphetamine reduces maternal and fetal rat brain concentrations in late pregnancy

We hypothesized that treatment of pregnant rat dams with a dual reactive monoclonal antibody (mAb4G9) against (+)-methamphetamine [METH; equilibrium dissociation rate constant (KD) = 16 nM] and (+)-amphetamine (AMP; KD = 102 nM) could confer maternal and fetal protection from brain accumulation of both drugs of abuse. To test this hypothesis, pregnant Sprague-Dawley rats (on gestational day 21) received a 1 mg/kg i.v. METH dose, followed 30 minutes later by vehicle or mAb4G9 treatment. The mAb4G9 dose was 0.56 mole-equivalent in binding sites to the METH body burden. Pharmacokinetic analysis showed baseline METH and AMP elimination half-lives were congruent in dams and fetuses, but the METH volume of distribution in dams was nearly double the fetal values. The METH and AMP area under the serum concentration-versus-time curves from 40 minutes to 5 hours after mAb4G9 treatment increased >7000% and 2000%, respectively, in dams. Fetal METH serum did not change, but AMP decreased 23%. The increased METH and AMP concentrations in maternal serum resulted from significant increases in mAb4G9 binding. Protein binding changed from ∼15% to > 90% for METH and AMP. Fetal serum protein binding appeared to gradually increase, but the absolute fraction bound was trivial compared with the dams. mAb4G9 treatment significantly reduced METH and AMP brain values by 66% and 45% in dams and 44% and 46% in fetuses (P < 0.05), respectively. These results show anti-METH/AMP mAb4G9 therapy in dams can offer maternal and fetal brain protection from the potentially harmful effects of METH and AMP.

Pharmacokinetic approaches to treatment of drug addiction

The pharmacokinetic approach to treatment targets the drug molecules themselves, aiming to reduce their concentration at the site of action, thereby reducing or preventing any pharmacodynamic effect. This approach might be useful in the treatment of acute drug toxicity/overdose and in the long-term treatment of addiction. Early clinical trials with anticocaine and antinicotine vaccines have shown reduced drug use and good tolerability. Also showing promise in animal studies are monoclonal antibodies against cocaine, methamphetamine and phencyclidine, as well as the enhancment of cocaine metabolism with genetic variants of human butyrylcholinesterase, using a bacterial esterase or catalytic monoclonal antibodies. Pharmacokinetic treatments offer potential advantages in terms of patient compliance, absence of medication interactions and benefit for patients who cannot take standard medications.

Affinity improvement of a therapeutic antibody to methamphetamine and amphetamine through structure-based antibody engineering

Methamphetamine (METH) abuse is a worldwide threat, without any FDA approved medications. Anti-METH IgGs and single chain fragments (scFvs) have shown efficacy in preclinical studies. Here we report affinity enhancement of an anti-METH scFv for METH and its active metabolite amphetamine (AMP), through the introduction of point mutations, rationally designed to optimize the shape and hydrophobicity of the antibody binding pocket. The binding affinity was measured using saturation binding technique. The mutant scFv-S93T showed 3.1 fold enhancement in affinity for METH and 26 fold for AMP. The scFv-I37M and scFv-Y34M mutants showed enhancement of 94, and 8 fold for AMP, respectively. Structural analysis of scFv-S93T:METH revealed that the substitution of Ser residue by Thr caused the expulsion of a water molecule from the cavity, creating a more hydrophobic environment for the binding that dramatically increases the affinities for METH and AMP.

Customizing monoclonal antibodies for the treatment of methamphetamine abuse: current and future applications

Monoclonal antibody-based medications designed to bind (+)-methamphetamine (METH) with high affinity are among the newest approaches to the treatment of METH abuse and the associated medical complications. The potential clinical indications for these medications include treatment of overdose, reduction of drug dependence, and protection of vulnerable populations from METH-related complications. Research designed to discover and conduct preclinical and clinical testing of these antibodies suggests a scientific vision for how intact monoclonal antibody (mAb) (singular and plural) or small antigen-binding fragments of mAb could be engineered to optimize the proteins for specific therapeutic applications. In this review, we discuss keys to success in this development process including choosing predictors of specificity, efficacy, duration of action, and safety of the medications in disease models of acute and chronic drug abuse. We consider important aspects of METH-like hapten design and how hapten structural features influence specificity and affinity, with an example of a high-resolution X-ray crystal structure of a high-affinity antibody to demonstrate this structural relationship. Additionally, several prototype anti-METH mAb forms such as antigen-binding fragments and single-chain variable fragments are under development. Unique, customizable aspects of these fragments are presented with specific possible clinical indications. Finally, we discuss clinical trial progress of the first in kind anti-METH mAb, for which METH is the disease target instead of vulnerable central nervous system networks of receptors, binding sites, and neuronal connections.

Structural characterization of a therapeutic anti-methamphetamine antibody fragment: oligomerization and binding of active metabolites

Vaccines and monoclonal antibodies (mAb) for treatment of (+)-methamphetamine (METH) abuse are in late stage preclinical and early clinical trial phases, respectively. These immunotherapies work as pharmacokinetic antagonists, sequestering METH and its metabolites away from sites of action in the brain and reduce the rewarding and toxic effects of the drug. A key aspect of these immunotherapy strategies is the understanding of the subtle molecular interactions important for generating antibodies with high affinity and specificity for METH. We previously determined crystal structures of a high affinity anti-METH therapeutic single chain antibody fragment (scFv6H4, K_D = 10 nM) in complex with METH and the (+) stereoisomer of 3,4-methylenedioxymethamphetamine (MDMA, or “ecstasy”). Here we report the crystal structure of scFv6H4 in homo-trimeric unbound (apo) form (2.60Å), as well as monomeric forms in complex with two active metabolites; (+)-amphetamine (AMP, 2.38Å) and (+)-4-hydroxy methamphetamine (p-OH-METH, 2.33Å). The apo structure forms a trimer in the crystal lattice and it results in the formation of an intermolecular composite beta-sheet with a three-fold symmetry. We were also able to structurally characterize the coordination of the His-tags with Ni²⁺. Two of the histidine residues of each C-terminal His-tag interact with Ni²⁺ in an octahedral geometry. In the apo state the CDR loops of scFv6H4 form an open conformation of the binding pocket. Upon ligand binding, the CDR loops adopt a closed formation, encasing the drug almost completely. The structural information reported here elucidates key molecular interactions important in anti-methamphetamine abuse immunotherapy.

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.

A methamphetamine vaccine attenuates methamphetamine-induced disruptions in thermoregulation and activity in rats

BACKGROUND

There are no approved pharmacotherapies for d-methamphetamine (METH) addiction and existing therapies have limited efficacy. Advances in using immunotherapeutic approaches for cocaine and nicotine addiction have stimulated interest in creating a similar approach for METH addiction. This study investigated whether active vaccination against METH could potentially attenuate responses to METH in vivo.

METHODS

Male Sprague Dawley rats (n = 32) received a four-boost series with one of three candidate anti-METH vaccines (MH2[R], MH6, and MH7) or a control keyhole limpet hemocyanin conjugate vaccine. Effects of METH on rectal temperature and wheel activity at 27°C ambient temperature were determined. The most efficacious vaccine, MH6, was then contrasted with keyhole limpet hemocyanin conjugate vaccine in a subsequent experiment (n = 16), wherein radiotelemetry determined home cage locomotor activity and body temperature at 23°C ambient temperature.

RESULTS

The MH6 vaccine produced high antibody titers with nanomolar affinity for METH and sequestered METH in the periphery of rats. In experiment 1, the thermoregulatory and psychomotor responses produced by METH at 27°C were blocked in the MH6 group. In experiment 2, METH-induced decreases in body temperature and locomotor activity at 23°C were also attenuated in the MH6 group. A pharmacokinetic study in experiment 2 showed that MH6-vaccinated rats had higher METH serum concentrations, yet lower brain METH concentrations, than control rats, and METH concentrations correlated with individual antibody titer.

CONCLUSIONS

These data demonstrate that active immunopharmacotherapy provides functional protection against physiological and behavioral disruptions induced by METH.

A vaccine against methamphetamine attenuates its behavioral effects in mice

BACKGROUND

Vaccines have treatment potential for methamphetamine (MA) addiction. We tested whether a conjugate vaccine against MA (succinyl-methamphetamine-keyhole limpet hemocyanin carrier protein; SMA-KLH) would generate MA antibodies and alter MA-induced behaviors.

METHODS

Mice were injected with SMA-KLH and received booster administrations 3 and 20 weeks later. Serum antibody titers reached peak levels by 4-6 weeks, remained at a modest level through 18 weeks, peaked again at 22 weeks after the second boost, and were still elevated at 35 weeks. At 7 weeks, groups of vaccinated and non-vaccinated mice were administered one of three MA doses (1, 2 or 3 mg/kg) to assess locomotor activity.

RESULTS

Non-vaccinated mice showed dose-dependent effects of MA with hypolocomotion at the lowest dose and elevated activity levels at the highest dose. Both dose effects were reduced in SMA-KLH groups, particularly low dose-induced hypolocomotion at later times post MA administration. Separate groups of vaccinated and non-vaccinated mice were trained in MA place conditioning at 30 weeks with either 0 (vehicle) or 0.5mg/kg MA. Although times spent in the MA-paired side did not differ between groups on test vs. baseline sessions, SMA-KLH mice conditioned with MA showed reduced conditioned approach behaviors and decreased conditioned activity levels compared to control groups.

CONCLUSION

These data suggest SMA-KLH attenuates the ability of MA to support place conditioning and reduces or delays its locomotor effects. Overall, results support SMA-KLH as a candidate MA vaccine.

Monoclonal antibodies as pharmacokinetic antagonists for the treatment of (+)-methamphetamine addiction

Developing specific medications to treat (+)-methamphetamine (METH) addiction is a difficult challenge because METH has multiple sites of action that are intertwined with normal neurological function. As a result, no small molecule medication for the treatment of METH addiction has made it through the FDA clinical trials process. With the invention of a new generation of proteinbased therapies, it is now possible to consider treating drug addiction by an entirely different approach. This new approach is based on the discovery of very high affinity anti-METH monoclonal antibodies (mAbs), which are non-addictive and antagonize METH effects from the blood stream without entering the brain. Due to a very long biological half-life, anti-METH mAbs would only need to be administered once every 2-4 weeks, aiding in patient compliance. As a relapse prevention medication, anti-METH mAbs could reduce or prevent the rewarding effects of a relapse to METH use and thereby improve a patient's probability of remaining in therapy and recovering from their addiction. In this review, we discuss the discovery process of anti-METH mAbs, with a focus on the preclinical development leading to high affinity anti-METH mAb antagonists.

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.

Dose-dependent changes in the locomotor responses to methamphetamine in BALB/c mice: low doses induce hypolocomotion

The overall goal of the present study was to determine the effects of different doses of (+)-methamphetamine (meth) on locomotor activity of Balb/C mice. Four experiments were designed to test a wide range of meth doses in BALB/c female mice. In Experiment 1, we examined locomotor activity induced by an acute administration of low doses of meth (0.01 and 0.03mg/kg) in a 90-min session. Experiment 2 was conducted to test higher meth doses (0.3-10mg/kg). In Experiment 3, separate sets of mice were pre-treated with various meth doses once or twice (one injection/week) prior to a locomotor challenge with a low meth dose. Finally, in Experiment 4, we tested whether locomotor activation would be affected by pretreatment with a low or moderate dose of meth one month prior to the low meth dose challenge. Results show that low doses of meth induce hypolocomotion whereas moderate to high doses induce hyperlocomotion. Prior exposure to either one moderate or high dose of meth or to two, low doses of meth attenuated the hypolocomotor effect of a low meth dose one week later. This effect was also attenuated in mice tested one month after administration of a moderate meth dose. These results show that low and high doses of meth can have opposing effects on locomotor activity. Further, prior exposure to the drug leads to tolerance, rather than sensitization, of the hypolocomotor response to low meth doses.

Therapeutic anti-methamphetamine antibody fragment-nanoparticle conjugates: synthesis and in vitro characterization

Treatments specific to the medical problems caused by methamphetamine (METH) abuse are greatly needed. Toward this goal, we are developing new multivalent anti-METH antibody fragment-nanoparticle conjugates with customizable pharmacokinetic properties. We have designed a novel anti-METH single chain antibody fragment with an engineered terminal cysteine (scFv6H4Cys). Generation 3 (G3) polyamidoamine dendrimer nanoparticles were chosen for conjugation due to their monodisperse properties and multiple amine functional groups. ScFv6H4Cys was conjugated to G3 dendrimers via a heterobifunctional PEG cross-linker that is reactive to a free amine on one end and a thiol group on the other. PEG modified dendrimers were synthesized by reacting the PEG cross-linker with dendrimers in a stoichiometric ratio of 11:1, which were further reacted with 3-fold molar excess of anti-METH scFv6H4Cys. This reaction resulted in a heterogeneous mix of G3-PEG-scFv6H4Cys conjugates (dendribodies) with three to six scFv6H4Cys conjugated to each dendrimer. The dendribodies were separated from the unreacted PEG modified dendrimers and scFv6H4Cys using affinity chromatography. A detailed in vitro characterization of the PEG modified dendrimers and the dendribodies was performed to determine size, purity, and METH binding function. The dendribodies were found to have affinity for METH identical to that of the unconjugated scFv6H4Cys in saturation binding assays, whereas the PEG modified dendrimers had no affinity for METH. These data suggest that an anti-METH scFv can be successfully conjugated to a PEG modified dendrimer nanoparticle with no adverse effects on METH binding properties. This study is a critical step toward preclinical characterization and development of a novel nanomedicine for the treatment of METH abuse.

Vaccines against drug abuse

The currently available medications for the treatment of drug abuse have had only limited success. Anti-addiction vaccines, aimed at eliciting antibodies that block the pharmacological effects of drugs, have great potential for treating drug abuse. We review the status of two vaccines that are undergoing clinical trials (for cocaine and nicotine addiction) and two that are still in preclinical development (for methamphetamine and heroin addiction). We also outline the challenges and ethical concerns associated with the development of anti-addiction vaccines and their use as future therapeutics.

Vaccines in the Treatment of Substance Abuse

Reconceptualizing drugs as toxins allowed an important shift in the approach to the treatment of substance abuse, because it ushered in consideration of immunological methods of pharmacotherapy. This paradigm shift represented a dramatic departure from previously considered approaches to pharmacotherapy for substance use disorders (SUDs), which had up until that time focused predominantly on either agonist and/or antagonist medications meant to block drug effects or to decrease reward, reinforcement, or craving. Use of immunological theory in SUD treatment also meant that 1) a potentially addicting medication would not be administered as part of therapy and 2) side effects could be limited, because the individual's immune system would be responsible for delivering treatment.

Anti-addiction vaccines

Despite intensive efforts to eradicate it, addiction to both legal and illicit drugs continues to be a major worldwide medical and social problem. Anti-addiction vaccines can produce the antibodies to block the effects of these drugs on the brain, and have great potential to ameliorate the morbidity and mortality associated with illicit drug intoxications. This review provides a current overview of anti-addiction vaccines that are under clinical trial and pre-clinical research evaluation. It also outlines the development challenges, ethical concerns, and likely future intervention for anti-addiction vaccines.

Pharmacological approaches to methamphetamine dependence: a focused review

Methamphetamine dependence is a serious worldwide public health problem with major medical, psychiatric, socioeconomic and legal consequences. Various neuronal mechanisms implicated in methamphetamine dependence have suggested several pharmacological approaches. A literature search from a range of electronic databases (PubMed, EMBASE, PsycInfo, the NIDA research monograph index and the reference list of clinicaltrials.gov) was conducted for the period from January 1985 to October 2009. There were no restrictions on the identification or inclusion of studies in terms of publication status, language and design type. A variety of medications have failed to show efficacy in clinical trials, including a dopamine partial agonist (aripiprazole), GABAergic agents (gabapentin) and serotonergic agents (SSRI, ondansetron, mirtazapine). Three double-blind placebo-controlled trials using modafinil, bupropion and naltrexone have shown positive results in reducing amphetamine or methamphetamine use. Two studies employing agonist replacement medications, one with d-amphetamine and the other with methylphenidate, have also shown promise. Despite the lack of success in most studies to date, increasing efforts are being made to develop medications for the treatment of methamphetamine dependence and several promising agents are targets of further research.

Drugs of abuse: management of intoxication and antidotes

Illicit drug intoxications are an increasing public health problem for which, in most cases, no antidotes are clinically available. The diagnosis and treatment of these intoxications requires a trained clinician with experience in recognizing the specific signs and symptoms of intoxications to individual drugs as well as polydrug intoxications, which are more the rule than the exception. To make the diagnosis, the clinical observation and a urine toxicology test are often enough. Evaluating the blood levels of drugs is frequently not practical because the tests can be expensive and results may be delayed and unavailable to guide the establishment of a treatment plan. Other laboratory tests may be useful depending on the drug or drugs ingested and the presence of other medical complications. The treatment should be provided in a quiet, safe and reassuring environment. Vital signs should be closely monitored. Changes in blood pressure, respiratory frequency and temperature should be promptly treated, particularly respiratory depression (in cases of opiate intoxication) or hyperthermia (in cases of cocaine or amphetamine intoxication). Intravenous fluids should be administered as soon as possible. Other psychiatric and medical complication should receive appropriate symptomatic treatment. Research on immunotherapies, including vaccines, monoclonal and catalytic antibodies, seems to be a promising approach that may yield specific antidotes for drugs of abuse, helping to ameliorate the morbidity and mortality associated with illicit drug intoxications.

The synthesis of haptens and their use for the development of monoclonal antibodies for treating methamphetamine abuse

In addition to addiction, the repeated use of (+)-methamphetamine [(+)-METH], (+)-amphetamine [(+)-AMP], or (+/-)-3,4-methylenedioxymethamphetamine ((+/-)-MDMA, commonly called ecstasy) can lead to life-threatening medical problems including cardiovascular injury, severe depression, and psychosis. Currently, there are no specific pharmacotherapies to treat these medical problems. In this study, we report the design and synthesis of two haptens, (S)-(+)-3-(9-carboxynonyloxy)methamphetamine (3a, (+)-METH MO10) and (S)-(+)-3-(5-carboxypentyloxy)methamphetamine (3b, (+)-METH MO6), and their use in generating high affinity (low K(D) value) monoclonal antibodies (mAbs) against (+)-METH, (+)-AMP, and/or (+)-MDMA. On the basis of results from the determination of mAb K(D) values and ligand specificity, the mAbs generated from hapten 3a showed the greatest promise for generating active and passive immunotherapies for treating overdose or addiction from (+)-METH-like stimulants.

Designing immunotherapies to thwart drug abuse

Immunotherapy for treating illicit drug abuse is a rapidly advancing field. There are currently two major approaches to developing drug-specific immunotherapies: active and passive. Active immunotherapy involves conjugating a drug-like hapten to a carrier protein and using traditional immunization approaches to generate a drug-specific immune response in the patient. In contrast, passive immunotherapy utilizes preformed monoclonal antibodies. Whether generated by active immunization or delivered passively, antibodies act as pharmacokinetic antagonists by binding the drug in the blood-stream and reducing the amount and rate of drug delivery to receptors in the brain. A newly emerging technology in anti-drug immunotherapy is the use of antibody fragments, or scFvs, rather than intact immunoglobulin G (IgG). These scFvs can retain the same binding properties as the original mAbs, and are onethird the molecular weight, providing a scaffold for creating antibody treatments with more customizable properties. Another nascent area of research utilizing the scFv scaffold is in creating drug-specific scFv-nanoparticle conjugates. These conjugates could improve upon current drug-specific antibody paradigms by increasing multivalency and allowing pharmacokinetic customization, while avoiding interactions with endogenous antibody receptor pathways. These parallel approaches to immunotherapy are moving rapidly toward the clinic and may soon provide new therapies for treating drug abuse.

Anti-relapse medications: preclinical models for drug addiction treatment

Addiction is a chronic relapsing brain disease and treatment of relapse to drug-seeking is considered the most challenging part of treating addictive disorders. Relapse can be modeled in laboratory animals using reinstatement paradigms, whereby behavioral responding for a drug is extinguished and then reinstated by different trigger factors, such as environmental cues or stress. In this review, we first describe currently used animal models of relapse, different relapse triggering factors, and the validity of this model to assess relapse in humans. We further summarize the growing body of pharmacological interventions that have shown some promise in treating relapse to psychostimulant addiction. Moreover, we present an overview on the drugs tested in cocaine or methamphetamine addicts and examine the overlap of existing preclinical and clinical data. Finally, based on recent advances in our understanding of the neurobiology of relapse and published preclinical data, we highlight the most promising areas for future anti-relapse medication development.

Development of active and passive human vaccines to treat methamphetamine addiction

Methamphetamine (METH) abuse is a major worldwide epidemic, with no specific medications for treatment of chronic or acute effects. Anti-METH antibodies have the potential to save lives and reduce the crippling effects of METH abuse. While they are not expected to be the magic bullet to immediately cure addiction, immunotherapy could provide a breakthrough medication to continuously block or attenuate METH effects during a comprehensive addiction recovery plan. A unique challenge for METH antibody antagonists is the need to protect the brain from the complex direct and indirect adverse effects of long-term METH use. To meet this challenge, a new generation of passive monoclonal antibodies and active immunization therapies are at an advanced stage of preclinical development. Both of these vaccines could play an essential role in a well planned recovery program from human METH addiction by providing long-lasting protection from the rewarding and reinforcing effect of METH.

Immune responses to methamphetamine by active immunization with peptide-based, molecular adjuvant-containing vaccines

Vaccines to methamphetamine (meth) were designed by covalently attaching a meth hapten (METH) to peptide constructs that contained a conformationally biased, response-selective molecular adjuvant, YSFKPMPLaR (EP54). Rats immunized with EP54-containing meth vaccines generated serum antibody titers to authentic meth, an immune outcome that altered meth self-administration. Immunization increased meth self-administration suggesting pharmacokinetic antagonism. The ability of immune sera to bind a METH-modified target protein dramatically decreased during and shortly after the meth self-administration assay, suggesting effective sequestration of free meth. However, the binding ability of immune sera to the METH-modified target protein was recovered 34 days after meth-free clearance time.

The effect of a chimeric human/murine anti-cocaine monoclonal antibody on cocaine self-administration in rats

The predominantly human sequence anti-cocaine monoclonal antibody (mAb), 2E2, has high affinity and specificity for cocaine and antagonizes cocaine distribution to the brain in mice. To determine whether 2E2 can alter the self-administration of cocaine in rats, both cocaine-induced reinstatement (priming) of self-administration, and the rates of cocaine consumption were assessed during daily sessions. After self-administration training, the rats' cocaine priming threshold values were stable over a 2-week baseline period. Furthermore, the rates of cocaine consumption at unit doses of 0.3 and 3.0 micromol/kg were steady within sessions and stable between sessions. Then, 2E2 (120 mg/kg i.v.) or an equivalent dose of nonspecific human polyclonal IgG (control) was infused and daily sessions continued. 2E2 produced an initial, approximately 3-fold, increase in the cocaine priming threshold that declined toward baseline values over the subsequent 3 weeks, with an effect t((1/2)) of approximately 4 days. In contrast to the substantial increase in the cocaine priming threshold, 2E2 produced only modest dose-dependent increases (42 and 18%) in the cocaine consumption rates, and these also gradually declined toward baseline values. There was no significant effect of the control IgG on the priming threshold or rates of consumption of cocaine. After infusion, antibody blood concentrations declined over time, and a two-compartment pharmacokinetic model generated values for the distribution and elimination half-lives of 0.5 and 11.6 days for 2E2 and 0.4 and 6.0 days for control IgG. 2E2 had a long-lasting effect on cocaine-induced priming, which may predict its efficacy as an immunotherapy for cocaine abuse.

Substance abuse vaccines

Conventional substance-abuse treatments have only had limited success for drugs such as cocaine, nicotine, methamphetamine, and phencyclidine. New approaches, including vaccination to block the effects of these drugs on the brain, are in advanced stages of development. Although several potential mechanisms for the effects of antidrug vaccines have been suggested, the most straightforward and intuitive mechanism involves binding of the drug by antibodies in the bloodstream, thereby blocking entry and/or reducing the rate of entry of the drug into the central nervous system. The benefits of such antibodies on drug pharmacodynamics will be influenced by both the quantitative and the qualitative properties of the antibodies. The sum of these effects will determine the success of the clinical applications of antidrug vaccines in addiction medicine. This review will discuss these issues and present the current status of vaccine development for nicotine, cocaine, methamphetamine, phencyclidine, and morphine.

Combined active and passive immunization enhances the efficacy of immunotherapy against nicotine in rats

Vaccination against nicotine reduces the behavioral effects of nicotine in rats, and it is under clinical evaluation as a treatment for tobacco addiction. Efficacy is limited by the need for high serum nicotine-specific antibody (NicAb) levels, and currently available nicotine vaccines do not uniformly generate the required NicAb levels. Passive immunization with a nicotine-specific monoclonal antibody (Nic311) has also shown efficacy in rats. The principal aim of this study was to determine whether the combined use of vaccination and passive immunization would produce greater effects than vaccination alone on nicotine pharmacokinetics and locomotor sensitization (LMS) to nicotine. Rats were treated with vaccination alone, Nic311 alone, both, or neither, and then they were administered 10 daily injections of 0.3 mg/kg nicotine s.c. Treatment with Nic311 or vaccination alone increased the binding of nicotine in serum, reduced the unbound serum nicotine concentration and nicotine distribution to brain, and attenuated the development of LMS. Combined use of vaccination and passive immunization produced higher total serum NicAb levels, greater changes in nicotine pharmacokinetics, and a greater attenuation of LMS than either treatment alone. The total serum NicAb concentration was significantly correlated with brain nicotine levels and locomotor activity. These data indicate that providing higher serum NicAb concentrations improves the efficacy of immunotherapy against nicotine and that supplementing vaccination with passive immunization is a potential strategy to accomplish this.

The future of vaccines in the management of addictive disorders

Conventional substance abuse treatments have had only limited success. As a result, new approaches, including vaccination to block the effects of drugs such as cocaine, nicotine, methamphetamine, and phencyclidine, are in development. Although a number of possible rationales for the effects of antidrug vaccines have been suggested, the most straightforward and intuitive mechanism would involve binding of the drug by antibodies in the bloodstream, thereby blocking entry or reducing the rate of entry of the drug into the central nervous system. The theoretical parameters that would influence vaccine-induced drug pharmacodynamics are presented in this review, along with the current status on vaccine development for nicotine, cocaine, methamphetamine, and phencyclidine.

Biotechnology and the treatment of addictive disorders: new opportunities

Addiction is a chronic relapsing illness with onset typically occurring in the early teenage years, followed by cycles of drug use and abstinence. The disease is mitigated by complex interactions between genes and environment. Viewed as such, the treatment of addiction could span the whole lifetime of the patient and, ideally, should be tailored to the illness cycle. The search for effective treatments has intensified recently due to our better understanding of the underlying neurobiologic mechanisms contributing to drug use and relapse. The three main types of treatment are behavioral, pharmacologic and, more recently, immunologic therapies. Vaccines and monoclonal antibodies are being developed mainly for stimulant use disorders and nicotine addiction. In addition, new molecular targets identified by preclinical research have shown promise and are awaiting proof-of-concept studies in humans. The main focus of this review is on the development of immunotherapy for stimulants and nicotine addiction as a model highlighting the current status of the science and potential emerging discoveries and development.

Immunization prevents DDT buildup in mouse tissues

DDT is used for pest control, causing health and environmental hazards in some parts of the world. The goal of this study was to assess whether immunization against a toxic compound could reduce the toxicant uptake of an organism, specifically to develop a DDT immunization that promotes the production of specific antibodies and assess whether it reduces DDT levels in the bodies of mice that are exposed to DDT by intake. BALB/c mice were immunized with DDT-keyhole limpet hemocyanine (DDT-KLH) conjugate (n=10) or unconjugated KLH (n=10), which was used as a control. After the immunization specific DDT antibodies in the mouse serum were determined by ELISA and then the mice were fed chow containing 40 mg/kg of DDT for 45 days. Finally, the concentration of DDT and its metabolites, DDE and DDD, in various tissues was measured by gas chromatography. Specific DDT antibody levels were significantly higher in the DDT immunized group than in the control group. DDT, DDE and DDD levels in adipose tissue, blood, brain and spleen were significantly reduced in the DDT immunized animals relative to control animals. However, DDT and DDD levels were higher in the liver compared to the control group. The findings indicate that the DDT immunization reduces the total uptake of DDT in animal tissues, which is reflected by the lower levels in adipose tissue, blood, brain and spleen. The elevated levels in liver suggest that DDT-antibody complexes in mouse serum are delivered to the liver.

Using hapten design to discover therapeutic monoclonal antibodies for treating methamphetamine abuse

When generating monoclonal antibodies (mAb) against small molecules, the chemical composition and molecular orientation of the drug-like hapten on the antigen is a crucial determinant. This is especially important when attempting to discover therapeutic mAb against the drugs of abuse (+)-methamphetamine [(+)-METH], (+)-amphetamine [(+)-AMP], and the related compound (+)-3,4-methylenedioxymethamphetamine [(+)-MDMA, the plus isomer in the racemic mixture known as MDMA or ecstasy]. The goal of these studies was to design and synthesize (+)-METH-like haptens with structural attributes that could make them effective for generating monoclonal antibodies for treating medical problems associated with these stimulant drugs of abuse. Five prototype (+)-METH-like haptens, which mimic structural aspects of these drugs, were synthesized and used to generate mAb. After screening for anti-(+)-METH IgG antibodies in more than 25,000 potential mouse hybridoma cell lines, one prototype mAb from each of the five haptens was selected and studied in detail for molecular properties and preclinical efficacy. The amino acid sequences of the IgG-variable regions, structural models, affinity, and ligand specificity of each mAb were then used to help elucidate important therapeutic characteristics. Four of these antibodies exhibited high affinity and specificity to (+)-METH and (+)-MDMA; whereas one antibody (designated mAb4G9) exhibited high affinity and specificity to (+)-METH, (+)-MDMA, and (+)-AMP, without significant cross-reactivity against other METH-like ligands, over-the-counter medications, or endogenous neurotransmitters. Considered together, discovery of mAb4G9 and the other antibodies in this report represent an important step in understanding the process for custom design of drug class-specific therapeutic antibodies for the treatment of drug addiction.

Approaches to the development of medications for the treatment of methamphetamine dependence

BACKGROUND

Methamphetamine abuse has become an increasing problem in both the United States and globally with concomitant increases in adverse medical, social and environmental sequelae. Behavioral therapies have been used with some success to treat methamphetamine abusers and dependent individuals, but are not universally efficacious. Methamphetamine has a rich pharmacology that theoretically provides many opportunities for potential pharmacotherapeutic intervention. Nevertheless, there are no approved medications with an indication for treating methamphetamine abusers or addicts at this time.

AIM

To describe briefly how methamphetamine functions and affects function in brain and report how basic researchers and clinicians are attempting to exploit and exploiting this knowledge to discover and develop effective pharmacotherapies.

RESULTS

Scientifically based approaches to medications development by evaluating medications that limit brain exposure to methamphetamine; modulate methamphetamine effects at vesicular monoamine transporter-2 (VMAT-2); or affect dopaminergic, serotonergic, GABAergic, and/or glutamatergic brain pathways that participate in methamphetamine's reinforcing effects are presented.

CONCLUSION

The evidence supports the rationale that pharmacotherapies to decrease methamphetamine use, or reduce craving during abstinence may be developed from altering the pharmacokinetics and pharmacodynamics of methamphetamine or its effects on appetitive systems in the brain.

Effects of a nicotine conjugate vaccine on the acquisition and maintenance of nicotine self-administration in rats

RATIONALE

Immunization of rats against nicotine using a nicotine conjugate vaccine reduces the distribution of nicotine to brain in rats and attenuates some of nicotine's physiological and behavioral effects. It is not known whether such a vaccine can attenuate nicotine's reinforcing effects.

OBJECTIVE

The present experiment was conducted to determine whether a nicotine conjugate vaccine could interfere with the acquisition and maintenance of nicotine self-administration (NSA) in rats given 23 h day(-1) access to nicotine.

METHODS

To examine acquisition of NSA, rats were vaccinated with nicotine or control immunogen prior to being given access to a 0.01 mg kg(-1) infusion(-1) nicotine under a fixed-ratio(FR) 1 schedule for week 1, FR 2 for week 2, and FR 3 for week 3. Acquisition of cocaine self-administration (CSA) was similarly examined to determine the specificity of vaccination effects. To examine maintenance of NSA, rats were initially trained to self-administer nicotine under an FR 3 schedule, and then vaccinated with nicotine or control immunogen while NSA continued to be monitored.

RESULTS

NSA was significantly lower in vaccinated rats compared to controls during the acquisition protocol, with a 38% decrease in the number of infusions during the last week of training. The percentage of rats meeting acquisition criteria in the vaccinated group was lower (36%) than that in the control group (70%), but this difference was not statistically significant. Vaccination did not affect acquisition of CSA, demonstrating its specificity for nicotine. Maintenance of NSA was significantly reduced in vaccinated rats as compared to controls after the final vaccine injection, with a mean reduction of 57%. There was no evidence in either protocol that vaccinated rats attempted to compensate for altered nicotine distribution by increasing nicotine intake.

CONCLUSION

These data suggest that vaccination against nicotine can reduce the reinforcing effects of nicotine in rats and may have therapeutic potential for the treatment of tobacco dependence.