Pharmacokinetic antagonism of (+)-methamphetamine discrimination by a low-affinity monoclonal anti-methamphetamine antibody

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.

Preclinical Evaluation of Vaccines to Treat Opioid Use Disorders: How Close are We to a Clinically Viable Therapeutic?

The ongoing opioid crisis, now into its second decade, represents a global public health challenge. Moreover, the opioid crisis has manifested despite clinical access to three approved opioid use disorder medications: the full opioid agonist methadone, the partial opioid agonist buprenorphine, and the opioid antagonist naltrexone. Although current opioid use disorder medications are underutilized, the ongoing opioid crisis has also identified the need for basic research to develop both safer and more effective opioid use disorder medications. Emerging preclinical evidence suggests that opioid-targeted vaccines or immunopharmacotherapies may be promising opioid use disorder therapeutics. One premise for this article is to critically examine whether vaccine effectiveness evaluated using preclinical antinociceptive endpoints is predictive of vaccine effectiveness on abuse-related endpoints such as drug self-administration, drug discrimination, and conditioned place preference. A second premise is to apply decades of knowledge in the preclinical evaluation of candidate small-molecule therapeutics for opioid use disorder to the preclinical evaluation of candidate opioid use disorder immunopharmacotherapies. We conclude with preclinical experimental design attributes to enhance preclinical-to-clinical translatability and potential future directions for immunopharmacotherapies to address the dynamic illicit opioid environment.

The Development and Characterization of an scFv-Fc Fusion-Based Gene Therapy to Reduce the Psychostimulant Effects of Methamphetamine Abuse

Methamphetamine (METH) continues to be among the most addictive and abused drugs in the United States. Unfortunately, there are currently no Food and Drug Administration-approved pharmacological treatments for METH-use disorder. We have previously explored the use of adeno-associated viral (AAV)-mediated gene transfer of an anti-METH monoclonal antibody. Here, we advance our approach by generating a novel anti-METH single-chain variable fragment (scFv)-Fc fusion construct (termed 7F9-Fc) packaged into AAV serotype 8 vector (called AAV-scFv-Fc) and tested in vivo and ex vivo. A range of doses [1 × 10¹⁰, 1 × 10¹¹, and 1 × 10¹² vector copies (vcs)/mouse] were administered to mice, eliciting a dose-dependent expression of 7F9-Fc in serum with peak circulating concentrations of 48, 1785, and 3831 µg/ml, respectively. Expressed 7F9-Fc exhibited high-affinity METH binding, IC₅₀ = 17 nM. Between days 21 and 35 after vector administration, at both 1 × 10¹¹ vc/mouse and 1 × 10¹² vc/mouse doses, the AAV-7F9-Fc gene therapy significantly decreased the potency of METH in locomotor assays. On day 116 post-AAV administration, mice expressing 7F9-Fc sequestered over 2.5 times more METH in the serum than vehicle-treated mice, and METH concentrations in the brain were reduced by 1.2 times the value for vehicle mice. These data suggest that an AAV-delivered anti-METH Fc fusion antibody could be used to persistently reduce concentrations of METH in the central nervous system. SIGNIFICANCE STATEMENT: In this manuscript, we describe the testing of a novel antimethamphetamine (METH) single-chain variable fragment-Fc fusion protein delivered in mice using gene therapy. The results suggest that the gene therapy delivery system can lead to the production of significant antibody concentrations that mitigate METH's psychostimulant effects in mice over an extended time period.

Identification of Treatment Targets in a Genetic Mouse Model of Voluntary Methamphetamine Drinking

Methamphetamine has powerful stimulant and euphoric effects that are experienced as rewarding and encourage use. Methamphetamine addiction is associated with debilitating illnesses, destroyed relationships, child neglect, violence, and crime; but after many years of research, broadly effective medications have not been identified. Individual differences that may impact not only risk for developing a methamphetamine use disorder but also affect treatment response have not been fully considered. Human studies have identified candidate genes that may be relevant, but lack of control over drug history, the common use or coabuse of multiple addictive drugs, and restrictions on the types of data that can be collected in humans are barriers to progress. To overcome some of these issues, a genetic animal model comprised of lines of mice selectively bred for high and low voluntary methamphetamine intake was developed to identify risk and protective alleles for methamphetamine consumption, and identify therapeutic targets. The mu opioid receptor gene was supported as a target for genes within a top-ranked transcription factor network associated with level of methamphetamine intake. In addition, mice that consume high levels of methamphetamine were found to possess a nonfunctional form of the trace amine-associated receptor 1 (TAAR1). The Taar1 gene is within a mouse chromosome 10 quantitative trait locus for methamphetamine consumption, and TAAR1 function determines sensitivity to aversive effects of methamphetamine that may curb intake. The genes, gene interaction partners, and protein products identified in this genetic mouse model represent treatment target candidates for methamphetamine addiction.

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.

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.

Therapeutic vaccines for substance dependence

Immunotherapies are under development as a new approach to the treatment of substance dependence. The drugs of abuse currently being tested using this new approach are nicotine, cocaine, phencyclidine and methamphetamine. In laboratory animal models, a range of immunotherapies, including vaccines, monoclonal antibodies and catalytic antibodies, have been shown to reduce drug seeking. In human clinical trials, cocaine and nicotine vaccines have been shown to induce antibody titers while producing few side effects. Studies in humans determining how these vaccines interact in combination with their target drug are underway. Overall, immunotherapy offers a range of potential treatment options: drug treatment, as well as the treatment of overdose, prevention of brain or cardiac toxicity and fetal protection in pregnant drug abusers.

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.

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.

Immunopharmacotherapeutic manifolds and modulation of cocaine overdose

Cocaine achieves its psychostimulant, reinforcing properties through selectively blocking dopamine transporters, and this neurobiological mechanism impedes the use of classical receptor-antagonist pharmacotherapies to outcompete cocaine at CNS sites. Passive immunization with monoclonal antibodies (mAb) specific for cocaine circumvents this problem as drug is sequestered in the periphery prior to entry into the brain. To optimize an immunopharmacotherapeutic strategy for reversing severe cocaine toxicity, the therapeutic properties of mAb GNC92H2 IgG were compared to those of its engineered formats in a mouse overdose model. Whereas the extended half-life of an IgG justifies its application to the prophylactic treatment of addiction, the rapid, thorough biodistribution of mAb-based fragments, including F(ab')₂, Fab and scFv, may correlate to accelerated scavenging of cocaine and reversal of toxicity. To test this hypothesis, mice were administered the anti-cocaine IgG (180 mg/kg, i.v.) or GNC92H2-based agent after receiving an LD₅₀ cocaine dose (93 mg/kg, i.p.), and the timeline of overdose symptoms was recorded. All formats lowered the rate of lethality despite the >100-fold molar excess of drug to antibody binding capacity. However, only F(ab')₂-92H2 and Fab-92 H2 significantly attenuated the progression of premorbid behaviors, and Fab-92H2 prevented seizure generation in a percentage of mice. The calculation of serum half-life of each format demonstrated that the pharmacokinetic profile of Fab-92H2 (elimination half-life, t½~100 min) best approximated that of cocaine. These results not only confirm the importance of highly specific and tight drug binding by the mAb, but also highlight the benefit of aligning the pharmacokinetic and pharmacodynamic properties of the immunopharmacotherapeutic with the targeted drug.

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.

Bioavailability of (+)-methamphetamine in the pigeon following an intramuscular dose

Pigeons are used frequently as subjects in behavioral pharmacology research. An advantage of the pigeon is an exceedingly vascular breast muscle, which is easily accessible for injections. The purpose of these studies was to provide a profile of the pharmacokinetics of (+)-methamphetamine (METH) and (+)-amphetamine (AMP), a pharmacologically active metabolite, in pigeons (n=6) after intramuscular (i.m.) and intravenous (i.v.) dosing (0.8 mg/kg). LC-MS/MS analysis was used to determine serum concentrations of METH and AMP. A modified crossover design was used to determine the bioavailability, time to maximum concentration, total clearance, the volume of distribution, the maximal concentration, the area under the concentration-time curve (AUC), and terminal elimination half-life for METH. The route of administration did not significantly affect these pharmacokinetic parameters. The time to maximum concentration for METH and AMP following i.m. administration was 0.3 h. Maximum AMP serum concentrations were achieved in 2 h, irrespective of the route of administration, and these concentrations remained essentially constant for an additional 6 h. The metabolism of METH to AMP was not affected by the route of administration, and the molar ratio AMP to METH AUC values were the same (i.v.=0.57; i.m.=0.41). These results show that METH pharmacokinetics after i.m. administration in the pigeon are similar to i.v. administration. Thus i.m. is a reasonable route of administration for METH behavioral assays in the pigeon if sufficient time for absorption is given following the dose, and the behavioral endpoint is not dependent on the rapid input of METH following an i.v. dose.

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.

Monoclonal antibody form and function: manufacturing the right antibodies for treating drug abuse

Drug abuse continues to be a major national and worldwide problem, and effective treatment strategies are badly needed. Antibodies are promising therapies for the treatment of medical problems caused by drug abuse, with several candidates in preclinical and early clinical trials. Monoclonal antibodies can be designed that have customized affinity and specificity against drugs of abuse, and because antibodies can be designed in various forms, in vivo pharmacokinetic characteristics can be tailored to suit specific clinical applications (eg, long-acting for relapse prevention, or short-acting for overdose). Passive immunization with antibodies against drugs of abuse has several advantages over active immunization, but because large doses of monoclonal antibodies may be needed for each patient, efficient antibody production technology is essential. In this minireview we discuss some of the antibody forms that may be effective clinical treatments for drug abuse, as well as several current and emerging production systems that could bridge the gap from discovery to patient use.

Effects of anti-phencyclidine and anti-(+)-methamphetamine monoclonal antibodies alone and in combination on the discrimination of phencyclidine and (+)-methamphetamine by pigeons

RATIONALE

Drug-specific monoclonal antibodies against phencyclidine (PCP) and (+)-methamphetamine [(+)-METH] should bind to these drugs to block their discriminative stimulus effects.

OBJECTIVES

To determine if mouse monoclonal antibodies against PCP and (+)-METH can block the discriminative stimulus effects of the drugs in pigeons.

MATERIALS AND METHODS

Pigeons were trained to discriminate among intramuscular injections of saline, 1 mg/kg PCP, and 2 mg/kg (+)-METH. After responding stabilized, cumulative dose-response curves were obtained for PCP and (+)-METH. Doses of an anti-PCP antibody at 620 mg/kg (anti-PCP mAb6B5) with a K (D) of 1.3 nM for PCP and no measurable affinity for (+)-METH and 1,000 mg/kg doses of anti-(+)-METH antibody (anti-METH mAb6H7) with a K (D) of 41 nM for (+)-METH and no measurable affinity for PCP were subsequently administered, first alone and later in combination after which the dose-response curves were redetermined.

RESULTS

When the antibodies were given alone, the anti-PCP antibody blocked the discriminative stimulus effects of PCP, but not those of (+)-METH, and the anti-(+)-METH antibody blocked the discriminative stimulus effects of (+)-METH, but not those of PCP. The anti-PCP antibody shifted the PCP dose-response curve further to the right and for a longer time than the anti-(+)-METH antibody shifted the dose response curve for (+)-METH. When the anti-PCP and anti-(+)-METH antibodies were administered on the same day, the discriminative stimulus effects of both drugs were completely blocked 1 day after antibody administration.

CONCLUSIONS

These experiments demonstrate the high specificity of the antibodies for the drugs to which they bind and show that monoclonal antibodies can be combined to antagonize the effects of more than one drug.

Immunotherapy for the treatment of drug abuse

Antibody therapy (as either active or passive immunization) is designed primarily to prevent drugs of abuse from entering the central nervous system (CNS). Antidrug antibodies reduce rush, euphoria, and drug distribution to the brain at doses that exceed the apparent binding capacity of the antibody. This is accomplished through a pharmacokinetic antagonism, which reduces the amount of drug in the brain, the rate of clearance across the blood-brain barrier, and the volume of drug distribution. Because the antibodies remain primarily in the circulatory system, they have no apparent central nervous system side effects. Active immunization with drug-protein conjugate vaccines has been tested for cocaine, heroin, methamphetamine, and nicotine in animal, with 1 cocaine and 3 nicotine vaccines in Phase 2 human trials. Passive immunization with high affinity monoclonal antibodies has been tested for cocaine, methamphetamine, nicotine, and phencyclidine (PCP) in preclinical animal models. Antibodies have 2 immediate clinical applications in drug abuse treatment: to treat drug overdose and to reduce relapse to drug use in addicted patients. The specificity of the therapies, the lack of addiction liability, minimal side effects, and long-lasting protection against drug use offer major therapeutic benefit over conventional small molecule agonists and antagonists. Immunotherapies can also be combined with other antiaddiction medications and enhance behavioral therapies. Current immunotherapies already show efficacy, but improved antigen design and antibody engineering promise highly specific and rapidly developed treatments for both existing and future addictions.

Development of murine monoclonal antibodies to methamphetamine and methamphetamine analogues

Methamphetamine and ecstasy are addictive drugs that cause major health problems in young people. Here we report on the development of high-affinity monoclonal antibodies to methamphetamine and its analogues, which may constitute powerful tools for antibody-based therapy. Six haptens, methamphetamine and ecstasy analogues, were synthesized, linked to a carrier protein and injected into mice. Several specific monoclonal antibodies were subsequently obtained following fusion of splenocytes from the immunized animals, with Sp2/O cells. Antibody specificity was fully investigated by competition ELISA, using a series of analogues, to identify specific amphetamine and/or ecstasy-specific antibodies. Antibody affinity was estimated to be in the range of 10(8) M(-1) with an enantiomeric hapten. Finally, two characteristic hybridoma clones (DAS-M243-6H5 and DAS-M278-4B12), secreting specific and potent mAbs were isolated. The development of drug-specific antibodies as in this study may provide promising therapeutic insight into how to neutralize methamphetamine in vivo during acute intoxication.

Reduced nicotine distribution from mother to fetal brain in rats vaccinated against nicotine: Time course and influence of nicotine dosing regimen

Nicotine is a teratogen in rats and possibly in humans. Vaccination against nicotine is being studied as a possible treatment for nicotine dependence. The safety of maternal vaccination against nicotine during or prior to pregnancy is not known. In this study, female rats were vaccinated and then administered acute or chronic nicotine during pregnancy at doses simulating nicotine exposure in smokers. Maternal vaccination reduced nicotine distribution to both maternal brain (44-47%) and fetal brain (17-39%) for up to 25 min after a single maternal nicotine dose administered on gestational day (GD) 20, but had a smaller effect on nicotine distribution to brain after continuous nicotine infusion. Nicotine distribution to maternal or fetal brain after repeated nicotine bolus doses was reduced immediately following an individual dose in vaccinated rats, but the chronic accumulation of nicotine in fetal brain was not altered. Nicotine distribution to whole fetus, in contrast to fetal brain, was generally not altered by vaccination. Nicotine-specific antibody concentration in fetal serum was 10% that of maternal serum, and in fetal brain was <1% of maternal serum. Although nicotine transfer to the whole fetus was not reduced by vaccination, protein binding data suggest that nicotine-specific antibody transferred from mother to fetus served to bind nicotine in fetal serum, reduce the unbound nicotine concentration, and thereby reduce nicotine distribution to fetal brain. These data comment on the safety of vaccination against nicotine during pregnancy, and suggest that vaccination may reduce the distribution of nicotine to fetal brain under some nicotine dosing conditions.

Investigations using immunization to attenuate the psychoactive effects of nicotine

Despite the enormous health risks, people continue to smoke and use tobacco primarily as a result of nicotine addiction. As part of our immunopharmacotherapy research, the effects of active and passive immunizations on acute nicotine-induced locomotor activity in rats were investigated. To this end, rats were immunized with either a NIC-KLH immunoconjugate vaccine designed to elicit an antinicotine immune response, or were administered an antinicotine monoclonal antibody, NIC9D9, prior to a series of nicotine challenges and testing sessions. Vaccinated rats showed a 45% decrease in locomotor activity compared to a 16% decrease in controls. Passive immunization with NIC9D9 resulted in a 66.9% decrease in locomotor activity versus a 3.4% decrease in controls. Consistent with the behavioral data, much less nicotine was found in the brains of immunized rats. The results support the potential clinical value of immunopharmacotherapy for nicotine addiction in the context of tobacco cessation programs.

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

Two murine-derived anti-methamphetamine monoclonal antibodies were studied as potential pharmacokinetic antagonists of (+)-methamphetamine self-administration by rats. Intravenous administration of a 1 g/kg dose of the lower affinity [antibody equilibrium dissociation constant (K(d)) = 250 nM] monoclonal antibody (mAb) designated mAb6H8, 1 day before the start of several daily 2-h self-administration sessions produced effects that depended on the dose of (+)-methamphetamine. mAb6H8 increased the rate of self-administration of a unit dose of 0.06 mg/kg (+)-methamphetamine, had little effect on the rate of self-administration of a unit dose of 0.03 mg/kg (+)methamphetamine, and lowered the rate of self-administration of a unit dose of 0.01 mg/kg (+)-methamphetamine to a level similar to that after saline substitution. mAb-induced changes in rates of self-administration occurred very early in self-administration sessions and lasted for 3 to 7 days. Intravenous administration of a 1 or a 0.6 g/kg dose of a higher affinity (K(d) = 11 nM) mAb designated mAb6H4, 24 h before the first of several self-administration sessions, produced very similar effects to the lower affinity mAb, despite the more than 20-fold greater affinity for (+)-methamphetamine. It is proposed that these anti-methamphetamine antibodies bind some of the self-administered (+)-methamphetamine before it can penetrate into brain, thereby reducing the amount of free drug available to function as a reinforcer. Although neither of these mAb medications are optimal antibodies for treating (+)-methamphetamine abuse, the experiments demonstrate that anti-(+)-methamphetamine monoclonal antibodies can attenuate the self-administration of the drug and suggest the potential of using monoclonal antibodies as pharmacokinetic antagonists of (+)-methamphetamine.