First human study of a chimeric anti-methamphetamine monoclonal antibody in healthy volunteers

Development of fentanyl-specific monoclonal antibody (mAb) to antagonize the pharmacological effects of fentanyl

Fentanyl, a critical component of opioid analgesics, poses a severe threat to public health, exacerbating the drug problem due to its potential fatality. Herein, we present two novel haptens designed with different attachment sites conjugated to keyhole limpet hemocyanin (KLH), aiming to develop an efficacious vaccine against fentanyl. KLH-Fent-1 demonstrated superior performance over KLH-Fent-2 in antibody titer, blood-brain distribution, and antinociceptive tests. Consequently, we immunized mice with KLH-Fent-1 to generate fentanyl-specific monoclonal antibodies (mAbs) using the hybridoma technique to compensate for the defects of active immunization in the treatment of opioid overdose and addiction. The mAb produced by hybridoma 9D5 exhibited the ability to recognize fentanyl and its analogs with a binding affinity of 10-10 M. Subsequently, we developed a human IgG1 chimeric mAb to improve the degree of humanization. Pre-treatment with murine and chimeric mAb significantly reduced the analgesic effect of fentanyl and altered its blood-brain biodistribution in vivo. Furthermore, in a mouse model of fentanyl-induced respiratory depression, the chimeric mAb effectively reversed respiratory depression promptly and maintained a certain level during the week. The development of high-affinity chimeric mAb gives support to combat the challenges of fentanyl misuse and its detrimental consequences. In conclusion, mAb passive immunization represents a viable strategy for addressing fentanyl addiction and overdose.

Investigation of monoclonal antibody CSX-1004 for fentanyl overdose

The opioid crisis in the United States is primarily driven by the highly potent synthetic opioid fentanyl leading to >70,000 overdose deaths annually; thus, new therapies for fentanyl overdose are urgently needed. Here, we present the first clinic-ready, fully human monoclonal antibody CSX-1004 with picomolar affinity for fentanyl and related analogs. In mice CSX-1004 reverses fentanyl antinociception and the intractable respiratory depression caused by the ultrapotent opioid carfentanil. Moreover, toxicokinetic evaluation in a repeat-dose rat study and human tissue cross-reactivity study reveals a favorable pharmacokinetic profile of CSX-1004 with no safety-related issues. Using a highly translational non-human primate (NHP) model of respiratory depression, we demonstrate CSX-1004-mediated protection from repeated fentanyl challenges for 3-4 weeks. Furthermore, treatment with CSX-1004 produces up to a 15-fold potency reduction of fentanyl in NHP respiration, antinociception and operant responding assays without affecting non-fentanyl opioids like oxycodone. Taken together, our data establish the feasibility of CSX-1004 as a promising candidate medication for preventing and reversing fentanyl-induced overdose.

Pillar[6]MaxQ: A Potent Supramolecular Host for In Vivo Sequestration of Methamphetamine and Fentanyl

Pillar[6]MaxQ (P6AS) functions as an in vivo sequestration agent for methamphetamine and fentanyl. We use 1H NMR, isothermal titration calorimetry, and molecular modelling to deduce the geometry and strength of the P6AS•drug complexes. P6AS forms tight complexes with fentanyl (Kd=9.8 nM), PCP (17.1 nM), MDMA (25.5 nM), mephedrone (52.4 nM), and methamphetamine (101 nM). P6AS has good in vitro biocompatibility according to MTS metabolic, Adenylate Kinase cell death, and hERG ion channel inhibition assays, and the Ames fluctuation test. The no observed adverse effect level for P6AS is 45 mg/kg. The hyperlocomotion of mice treated with methamphetamine (0.5 mg/kg) can be ameliorated by treatment with P6AS (35.7 mg/kg) 5-minutes later, whereas the hyperlocomotion of mice treated with fentanyl (0.1 mg/kg) can be controlled by treatment with P6AS (5 mg/kg) up to 15-minutes later. P6AS has significant potential for development as a broad spectrum in vivo sequestration agent.

Anti-Strychnine Immunoconjugate Reduces the Effects of Strychnine-Induced Toxicity in Mice

Strychnine poisoning induces seizures that result in loss of control of airway muscles, leading to asphyxiation and subsequent death. Current treatment options are limited, requiring hands-on medical care and isolation to low-stimulus environments. Anticonvulsants and muscle relaxants have shown limited success in cases of severe toxicity. Furthermore, nonfatal strychnine poisoning is likely to result in long-term muscular and cognitive damage. Due to its potency, accessibility, and lack of effective antidotes, strychnine poses a unique threat for mass casualty incidents. As a first step toward developing an anti-strychnine immunotherapy to reduce or prevent strychnine-induced seizures, a strychnine vaccine was synthesized using subunit keyhole limpet hemocyanin. Mice were vaccinated with the strychnine immunoconjugate and then given a 0.75 mg/kg IP challenge of strychnine and observed for seizures for 30 min. Vaccination reduced strychnine-induced events, and serum strychnine levels were increased while brain strychnine levels were decreased in vaccinated animals compared to the control. These data demonstrate that strychnine-specific antibodies can block the seizure-inducing effects of strychnine and could be used to develop a therapeutic for strychnine poisoning.

Immunotherapeutic strategies for treating opioid use disorder and overdose

INTRODUCTION

Development and implementation of effective treatments for opioid use disorder (OUD) and prevention of overdose are urgent public health needs. Though existing medications for OUD (MOUD) are effective, barriers to initiation and retention in treatment persist. Therefore, development of novel treatments, especially those may complement existing treatments, is needed.

AREAS COVERED

This review provides an overview of vaccines for substance use disorders (SUD) and mechanisms underlying their function and efficacy. Next, we focus on existing preclinical and clinical trials of SUD vaccines. We focus briefly on related strategies before providing an expert opinion on prior, current, and future work on vaccines for OUD. We included published findings from preclinical and clinical trials found on PubMed and ScienceDirect as well as ongoing or initiated trials listed on ClinicalTrials.gov.

EXPERT OPINION

The present opioid overdose and OUD crises necessitate urgent development and implementation of effective treatments, especially those that offer protection from overdose and can serve as adjuvants to existing medications. Promising preclinical trial results paired with careful efforts to develop vaccines that account for prior SUD vaccine shortcomings offer hope for current and future clinical trials of opioid vaccines. Clinical advantages of opioid vaccines appear to outnumber disadvantages, which may result in improved treatment options.

Neuroscientific Basis of Treatment for Substance Use Disorders

Substance use disorder is a chronic and relapsing disease that burdens both the individual and the society. In addition to psychosocial treatment approaches, currently there are approved pharmacological treatment options for opioid, alcohol and tobacco use disorders, but only symptomatic treatment can be offered to patients with other substance use disorders. Advances in neuroscience and a better understanding of the addiction process offer an opportunity to create new treatment options. There is a wide range of studies, ranging from the use of drugs with different indications to the development of new pharmacological treatments, and from vaccine studies to neuromodulation techniques. Establishing novel treatment goals in addition to complete abstinence and individualizing treatment by focusing on endophenotypes may increase the treatment alternatives and the efficacy of these treatments for SUD.

Advancing humanized monoclonal antibody for counteracting fentanyl toxicity towards clinical development

Innovative therapies to complement current treatments are needed to curb the growing incidence of fatal overdoses related to synthetic opioids. Murine and chimeric monoclonal antibodies (mAb) specific for fentanyl and its analogs have demonstrated pre-clinical efficacy in preventing and reversing drug-induced toxicity in rodent models. However, mAb-based therapeutics require extensive engineering as well as in vitro and in vivo characterization to advance to first-in-human clinical trials. Here, novel murine anti-fentanyl mAbs were selected for development based on affinity for fentanyl, and efficacy in counteracting the pharmacological effects of fentanyl in mice. Humanization and evaluation of mutations designed to eliminate predicted post-translational modifications resulted in two humanized mAbs that were effective at preventing fentanyl-induced pharmacological effects in rats. These humanized mAbs showed favorable biophysical properties with respect to aggregation and hydrophobicity by chromatography-based assays, and thermostability by dynamic scanning fluorimetry. These results collectively support that the humanized anti-fentanyl mAbs developed herein warrant further clinical development for treatment of fentanyl toxicity.

Pharmacological Profiling of Antifentanyl Monoclonal Antibodies in Combination with Naloxone in Pre- and Postexposure Models of Fentanyl Toxicity

The incidence of fatal drug overdoses in the United States is an alarming public health threat that has been exacerbated by the COVID-19 pandemic, resulting in over 100,000 deaths between April 2020 and April 2021. A significant portion of this is attributable to widespread access to fentanyl and other synthetic opioids, alone or in combination with heroin or psychostimulants, such as cocaine or methamphetamine. Monoclonal antibodies (mAb) offer prophylactic and therapeutic interventions against opioid overdose by binding opioids in serum, reducing distribution of drug to the brain and other organs. Here, we investigated the efficacy of a leading antifentanyl mAb, clone HY6-F9, in reversal and prevention of fentanyl-induced toxicity compared with the opioid receptor antagonist naloxone (NLX) in rats. In postexposure models, rats were challenged with fentanyl, followed by HY6-F9, NLX, or both. HY6-F9 reversed fentanyl-induced antinociception, respiratory depression, and bradycardia, and rats retained protection against additional challenges for at least 1 week. Although intravenous NLX reversed fentanyl-induced respiratory depression more rapidly than mAb alone, kinetics of reversal by intravenous mAb were similar to subcutaneous NLX. Coadministration of mAb and NLX provided greater protection than individual treatments against high doses of fentanyl. Prophylactic administration of mAb reduced the ED50 of NLX approximately twofold against 2.25 mg/kg of fentanyl. Finally, mAb sequestered fentanyl and its metabolite norfentanyl in serum and reduced brain concentrations of fentanyl. These results support the translation of mAb as medical interventions alone or in combination with NLX to prevent and reverse fentanyl-related overdose. SIGNIFICANCE STATEMENT: Fentanyl-related overdoses have increased dramatically in the US and worldwide. Currently, approved pharmacotherapies for treatment of opioid use disorder and reversal of overdose are not sufficient to curb the incidence of opioid-related deaths. Additionally, fentanyl and its potent analogs present a potential risk from use in deliberate poisoning or chemical attacks. This study demonstrates the use of monoclonal antibodies as a countermeasure to fentanyl-induced toxicity in pre- and postexposure scenarios, supporting their use in combination with the opioid antagonist naloxone.

In Vitro and In Vivo Sequestration of Methamphetamine by a Sulfated Acyclic CB[n]-Type Receptor

We report the synthesis of two new acyclic sulfated acyclic CB[n]-type receptors (TriM0 and Me4 TetM0) and investigations of their binding properties toward a panel of drugs of abuse (1-13) by a combination of 1 H NMR spectroscopy and isothermal titration calorimetry. TetM0 is the most potent receptor with Ka ≥106  M-1 toward methamphetamine, fentanyl, MDMA and mephedrone. TetM0 is not cytotoxic toward HepG2 and HEK 293 cells below 100 μM according to MTS metabolic and adenylate kinase release assays and is well tolerated in vivo when dosed at 46 mg kg-1 . TetM0 does not inhibit the hERG ion channel and is not mutagenic based on the Ames fluctuation test. Finally, in vivo efficacy studies show that the hyperlocomotion of mice treated with methamphetamine can be greatly reduced by treatment with TetM0 up to 5 minutes later. TetM0 has potential as a broad spectrum in vivo sequestrant for drugs of abuse.

In Vitro and In Vivo Sequestration of Phencyclidine by Me4 Cucurbit[8]uril*

We report investigations of the use of cucurbit[8]uril (CB[8]) macrocycles as an antidote to counteract the in vivo biological effects of phencyclidine. We investigate the binding of CB[8] and its derivative Me4 CB[8] toward ten drugs of abuse (3-9, 12-14) by a combination of 1 H NMR spectroscopy and isothermal titration calorimetry in phosphate buffered water. We find that the cavity of CB[8] and Me4 CB[8] are able to encapsulate the 1-amino-1-aryl-cyclohexane ring system of phencyclidine (PCP) and ketamine as well as the morphinan skeleton of morphine and hydromorphone with Kd values ≤50 nm. In vitro cytotoxicity (MTS metabolic and adenylate kinase cell death assays in HEK293 and HEPG2 cells) and in vivo maximum tolerated dose studies (Swiss Webster mice) which were performed for Me4 CB[8] indicated good tolerability. The tightest host⋅guest pair (Me4 CB[8]⋅PCP; Kd =2 nm) was advanced to in vivo efficacy studies. The results of open field tests demonstrate that pretreatment of mice with Me4 CB[8] prevents subsequent hyperlocomotion induction by PCP and also that treatment of animals previously dosed with PCP with Me4 CB[8] significantly reduces the locomotion levels.

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.

Monoclonal Antibodies Counteract Opioid-Induced Behavioral and Toxic Effects in Mice and Rats

Monoclonal antibodies (mAbs) and vaccines have been proposed as medical countermeasures to treat opioid use disorder (OUD) and prevent opioid overdose. In contrast to current pharmacotherapies (e.g., methadone, buprenorphine, naltrexone, and naloxone) for OUD and overdose, which target brain opioid receptors, mAbs and vaccine-generated polyclonal antibodies sequester the target opioid in the serum and reduce drug distribution to the brain. Furthermore, mAbs offer several potential clinical benefits over approved medications, such as longer serum half-life, higher selectivity, reduced side effects, and no abuse liability. Using magnetic enrichment to isolate opioid-specific B cell lymphocytes prior to fusion with myeloma partners, this study identified a series of murine hybridoma cell lines expressing mAbs with high affinity for opioids of clinical interest, including oxycodone, heroin and its active metabolites, and fentanyl. In mice, passive immunization with lead mAbs against oxycodone, heroin, and fentanyl reduced drug-induced antinociception and the distribution of the target opioid to the brain. In mice and rats, mAb pretreatment reduced fentanyl-induced respiratory depression and bradycardia, two risk factors for opioid-related overdose fatality. Overall, these results support use of mAbs to counteract toxic effects of opioids and other chemical threats. SIGNIFICANCE STATEMENT: The incidence of fatal overdoses due to the widespread access to heroin, prescription opioids, and fentanyl suggests that current Food and Drug Administration-approved countermeasures are not sufficient to mitigate the opioid epidemic. Monoclonal antibodies (mAbs) may provide acute protection from overdose by binding to circulating opioids in serum. Use of mAbs prophylactically, or after exposure in combination with naloxone, may reduce hospitalization and increase survival.

Effect of Bile Duct Ligation-induced Liver Dysfunction on Methamphetamine Pharmacokinetics and Locomotor Activity in Rats

PURPOSE

Methamphetamine (METH) abuse is associated with hepatic dysfunction related comorbidities such as HIV, hepatitis C, and polysubstance abuse with acetaminophen-containing opioid formulations. We aimed to develop a bile duct ligation (BDL)-induced hepatic dysfunction model for studying both METH and experimental treatments for METH abuse in this comorbidity.

METHODS

Sham or BDL surgery was performed in male Wistar rats on day 0. Liver function was measured throughout the study. On days 7 and 19, serum pharmacokinetics studies were performed with 1 mg/kg subcutaneous (sc) METH. On day 21, this dose was repeated to determine 2 h post-METH brain concentrations. METH-induced open field behaviors were measured every other day (days 12 - 16) with ascending sc doses (0.3 - 3 mg/kg).

RESULTS

BDL transiently increased alanine aminotransferase levels and altered liver structure, which resulted in significantly greater METH serum and brain exposure. In the BDL compared to sham group, there was a longer duration of METH-induced locomotor activity (after 1 and 3 mg/kg) and stereotypy (after 3 mg/kg).

CONCLUSIONS

In rats, liver dysfunction reduced METH clearance, increased brain METH concentrations, and enhanced METH effects on locomotor activity in a dose dependent manner. In addition, this model could be further developed to simulate the associated hepatic dysfunction of key METH abuse comorbidities for preclinical testing of novel pharmacotherapies for effectiveness and/or toxicity in vulnerable populations.

Antibody production and pharmacokinetics of METH in rats following vaccination with the METH vaccine, IXT-v100, adjuvanted with GLA-SE

BACKGROUND

Methamphetamine use disorder continues to be inadequately treated, but improvements are being made in the field of immunotherapeutics, including vaccines, which could provide new options for treatment. Cocaine and nicotine vaccines have been tested clinically, but have yet to elicit the necessary antibody concentrations required to be effective. Methamphetamine vaccines have been tested in multiple nonclinical models and appear promising. Improved adjuvants have the potential to further stimulate the immune system to reach effective levels of antibodies. Previously, the methamphetamine vaccine IXT-v100 was administered with GLA-SE, a toll-like receptor 4 agonist, in mice to produce higher levels of antibodies than when it was administered with two other widely used adjuvants, Alhydrogel and Sigma Adjuvant System.

METHODS

The purpose of this research was to evaluate IXT-v100, given in combination with the adjuvant GLA-SE, to determine its efficacy in antagonizing methamphetamine disposition in a rat pharmacokinetic study. Additional rat studies were conducted to compare the ability of IXT-v100 manufactured with greater hapten densities to elicit higher antibody levels.

RESULTS

As expected based on prior studies with anti-methamphetamine monoclonal antibodies, the antibodies resulting from vaccination with IXT-v100 altered methamphetamine pharmacokinetics by increasing serum concentrations and extending the half-life. Furthermore, intentional variations in the ratio of components during manufacturing led to production of vaccines with higher hapten densities. The higher hapten densities resulted in production of antibodies that maintained the ability to bind methamphetamine with high affinity.

CONCLUSIONS

The results support continued development of IXT-v100 for the treatment of methamphetamine use disorder.

Psychopharmacology: neuroimmune signaling in psychiatric disease-developing vaccines against abused drugs using toll-like receptor agonists

RATIONALE

Since substance use disorders have few or no effective pharmacotherapies, researchers have developed vaccines as immune-therapies against nicotine, cocaine, methamphetamine, and opioids including fentanyl.

OBJECTIVES

We focus on enhancing antibody (AB) production through stimulation of toll-like receptor-5 (TLR5) during active vaccination. The stimulating adjuvant is Entolimod, a novel protein derivative of flagellin. We review the molecular and cellular mechanisms underlying Entolimod's actions on TLR5.

RESULTS

Entolimod shows excellent efficacy for increasing AB levels to levels well beyond those produced by anti-addiction vaccines alone in animal models and humans. These ABs also significantly block the behavioral effects of the targeted drug of abuse. The TLR5 stimulation involves a wide range of immune cell types such as dendritic, antigen presenting, T and B cells. Entolimod binding to TLR5 initiates an intracellular signaling cascade that stimulates cytokine production of tumor necrosis factor and two interleukins (IL-6 and IL-12). While cytokine release can be catastrophic in cytokine storm, Entolimod produces a modulated release with few side effects even at doses 30 times greater than doses needed in these vaccine studies. Entolimod has markedly increased AB responses to all of our anti-addiction vaccines in rodent models, and in normal humans.

CONCLUSIONS

Entolimod and TLR5 stimulation has broad application to vaccines and potentially to other psychiatric disorders like depression, which has critical inflammatory contributions that Entolimod could reduce.

Monoclonal Antibodies for Combating Synthetic Opioid Intoxication

Opioid abuse in the United States has been declared a national crisis and is exacerbated by an inexpensive, readily available, and illicit supply of synthetic opioids. Specifically, fentanyl and related analogues such as carfentanil pose a significant danger to opioid users due to their high potency and rapid acting depression of respiration. In recent years these synthetic opioids have become the number one cause of drug-related deaths. In our research efforts to combat the public health threat posed by synthetic opioids, we have developed monoclonal antibodies (mAbs) against the fentanyl class of drugs. The mAbs were generated in hybridomas derived from mice vaccinated with a fentanyl conjugate vaccine. Guided by a surface plasmon resonance (SPR) binding assay, we selected six hybridomas that produced mAbs with 10^-11 M binding affinity for fentanyl, yet broad cross-reactivity with related fentanyl analogues. In mouse antinociception models, our lead mAb (6A4) could blunt the effects of both fentanyl and carfentanil in a dose-responsive manner. Additionally, mice pretreated with 6A4 displayed enhanced survival when subjected to fentanyl above LD₅₀ doses. Pharmacokinetic analysis revealed that the antibody sequesters large amounts of these drugs in the blood, thus reducing drug biodistribution to the brain and other tissue. Lastly, the 6A4 mAb could effectively reverse fentanyl/carfentanil-induced antinociception comparable to the opioid antagonist naloxone, the standard of care drug for treating opioid overdose. While naloxone is known for its short half-life, we found the half-life of 6A4 to be approximately 6 days in mice, thus monoclonal antibodies could theoretically be useful in preventing renarcotization events in which opioid intoxication recurs following quick metabolism of naloxone. Our results as a whole demonstrate that monoclonal antibodies could be a desirable treatment modality for synthetic opioid overdose and possibly opioid use disorder.

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.

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

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

Abuse liability assessment for biologic drugs - All molecules are not created equal

The development of novel drug candidates involves the thorough evaluation of potential efficacy and safety. To facilitate the safety assessment in light of global increases in prescription drug misuse/abuse, health authorities have developed guidance documents which provide a framework for evaluating the abuse liability of candidate therapeutics. The guidances do not distinguish between small molecules and biologics/biotherapeutics; however, there are key differences between these classes of therapeutics which are important drivers of concern for abuse. An analysis of these properties, including ability to distribute to the central nervous system, pharmacokinetic properties (e.g., half-life and metabolism), potential for off-target binding, and the physiochemical characteristics of biologic drug products suggests that the potential for abuse of a biologic is limited. Many marketed antibodies and recombinant proteins have been associated with adverse effects such as headache and dizziness. However, biologics have not historically engendered the rapid-onset psychoactive effects typically present for drugs of abuse, thus further underscoring their low risk for abuse potential. The factors to be taken into consideration before conducting nonclinical abuse liability studies with biologics are described herein; importantly, the aggregate assessment of these factors leads to the conclusion that abuse liability studies are unlikely to be necessary for this class of therapeutics.

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

INTRODUCTION

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

Molecular Containers Bind Drugs of Abuse in Vitro and Reverse the Hyperlocomotive Effect of Methamphetamine in Rats

We measured the affinity of five molecular container compounds (calabadions 1 and 2, CB[7], sulfocalix[4]arene, and HP-β-CD) toward seven drugs of abuse in homogenous aqueous solution at physiological pH by various methods (1 H NMR, UV/Vis, isothermal titration calorimetry [ITC]) and found binding constants (Ka values) spanning from <102 to >108  m-1 . We also report X-ray crystal structures of CB[7]⋅methamphetamine and 1⋅methamphetamine. We found that 2, but not CB[7], was able to ameliorate the hyperlocomotive activity of rats treated with methamphetamine. The bioavailability of the calabadions and their convergent building block synthesis suggest potential for further structural optimization as reversal agents for intoxication with nonopioid drugs of abuse for which no treatments are currently available.

A mathematical model of a recombinant humanized anti-cocaine monoclonal antibody's effects on cocaine pharmacokinetics in mice

AIMS

A recombinant humanized anti-cocaine monoclonal antibody (mAb), h2E2, is at an advanced stage of pre-clinical development as an immunotherapy for cocaine abuse. It is hypothesized that h2E2 binds to and sequesters cocaine in the blood.

MAIN METHODS

A three-compartment model of the effects of h2E2 on cocaine's distribution was constructed. The model assumes that h2E2 binds to cocaine and that the h2E2-cocaine complex does not enter the brain but distributes between the central and peripheral compartments. Free cocaine is eliminated from both the central and peripheral compartments, and h2E2 and the h2E2-cocaine complex are eliminated from the central compartment only. This model was tested against a new dataset measuring cocaine concentrations in the brain and plasma over 1h in the presence and absence of h2E2.

KEY FINDINGS

The mAb significantly increased plasma cocaine concentrations with a concomitant significant decrease in brain concentration. Plasma concentrations declined over the 1-hour sampling period in both groups. With a set of parameters within reasonable physiological ranges, the three-compartment model was able to qualitatively and quantitatively simulate the increased plasma concentration in the presence of the antibody and the decreased peak brain concentration in the presence of antibody. Importantly, the model explained the decline in plasma concentrations over time as distribution of the cocaine-h2E2 complex into a peripheral compartment.

SIGNIFICANCE

This model will facilitate the targeting of ideal mAb PK/PD properties thus accelerating the identification of lead candidate anti-drug mAbs.

The effects of a repeated dose of a recombinant humanized anti-cocaine monoclonal antibody on cocaine self-administration in rats

BACKGROUND

Immunotherapy has shown potential as a treatment for cocaine abuse. The humanized recombinant anti-cocaine monoclonal antibody (mAb) with the preclinical designation h2E2 has been shown to decrease cocaine concentrations in the brain in rats, but its effects on cocaine self-administration behavior have never been tested.

METHODS

The amount of cocaine needed to reinstate self-administration behavior (priming threshold) was calculated and the inter-injection intervals at unit doses of 0.3μmol/kg and 3μmol/kg during maintained self-administration were measured over a five-week baseline period. Rats trained to self-administer cocaine were infused with two doses of h2E2 (120mg/kg i.v.) 35days apart. Priming threshold and inter-injection intervals were measured for 35days after both injections.

RESULTS

After both injections of h2E2, priming thresholds were significantly increased (3-fold) compared to expected baseline and then gradually declined over 35days. A significant decrease (15-33%) in inter-injection intervals during maintained self-administration was also observed following both h2E2 infusions at the lower dose, and after the first injection at the higher dose. No significant decreases in body weight were observed after either injection, indicating a lack of toxicity following a second injection.

CONCLUSIONS

These data predict that the safety and effectiveness of h2E2 will be maintained after multiple treatments of this potential immunotherapy for cocaine abuse.

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

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

Chronic treatment of (+)-methamphetamine-induced locomotor effects in rats using one or a combination of two high affinity anti-methamphetamine monoclonal antibodies

We hypothesized that treatment of methamphetamine (METH) effects with a mixture of 2 high affinity anti-METH monoclonal antibodies (mAb) with differing molecular recognition for METH-like structures could increase efficacy compared to treatment with a single mAb. The antibodies studied were mAb7F9 (METH and amphetamine [AMP] KD = 7.7 and 270 nM) and mAb4G9 (16 nM and 110 nM, respectively) in a 50:50 mixture. Adult male Sprague Dawley Rats were treated with iv saline or a loading dose of mAb7F9-mAb4G9 (141 mg/kg of each mAb) followed by 2 weekly doses (70.5 mg/kg total) on days 7 and 14. METH challenge doses (0.56 mg/kg) were administered 4 hrs and 3 days after each mAb7F9-mAb4G9 treatment, and 7 days after the final treatment (day 21). Locomotor activity (0-4 hrs) and serum METH and AMP concentrations (at 5 hrs) were measured after each METH challenge. MAb7F9-mAb4G9 treatment significantly reduced the duration of locomotor activity after 6 of the 7 METH doses (P < 0.05) and significantly increased serum METH and AMP concentrations. Administering three-fold higher METH doses (1.68 mg/kg) on days 24 and 28 showed mAb7F9-mAb4G9 treatment had negligible effects on the duration of METH-induced locomotor activity. These data were then compared to previous monotherapy data. While mAb7F9-mAb4G9 therapy inhibited the effects of multiple METH challenge doses, the inhibition was not as profound or as long lasting as the effects of mAb7F9 treatment alone. These data demonstrate the importance of both mAb affinity and specificity in the production of effective, long-lasting anti-METH mAb therapies.

Optimization of a methamphetamine conjugate vaccine for antibody production in mice

There are still no approved medications for treating patients who abuse methamphetamine. Active vaccines for treating abuse of nicotine and cocaine are in clinical studies, but have not proven effective seemingly due to inadequate anti-drug antibody production. The current studies aimed to optimize the composition, adjuvant and route of administration of a methamphetamine conjugate vaccine, ICKLH-SMO9, in mice with the goal of generating significantly higher antibody levels. A range of hapten epitope densities were compared, as were the adjuvants Alhydrogel and a new Toll-like receptor 4 (TLR4) agonist called GLA-SE. While methamphetamine hapten density did not strongly affect the antibody response, the adjuvant did. Glucopyranosyl lipid A in a stable oil-in-water emulsion (GLA-SE) produced much higher levels of antibody in response to immunization compared with Alhydrogel; immunization with GLA-SE also produced antibodies with higher affinities for methamphetamine. GLA-SE has been used in human studies of vaccines for influenza among others and like some other clinical TLR4 agonists, it is safe and elicits a strong immune response. GLA-SE adjuvanted vaccines are typically administered by intramuscular injection and this also proved effective in these mouse studies. Clinical studies of the ICKLH-SMO9 methamphetamine vaccine adjuvanted with GLA-SE have the potential for demonstrating efficacy by generating much higher levels of antibody than substance abuse vaccines that have unsuccessfully used aluminum-based adjuvants.

Biologic Approaches to Treat Substance-Use Disorders

In contrast to traditional pharmacodynamic approaches to treat substance-use disorders (SUDs), the use of biologics (vaccines, monoclonal antibodies, and genetically modified enzymes) is based on a pharmacokinetic principle: reduce the amount of (and, ideally, eliminate) abused drug entering the central nervous system (CNS). Preclinical studies indicate that biologics are effective in both facilitating abstinence and preventing relapse to abused substances ranging from nicotine to heroin. While data are still emerging, the results from multiple clinical trials can best be described as mixed. Nonetheless, these clinical studies have already provided important insights using 'first-generation' tools that may inform the development of effective and commercially viable biologics to treat tobacco-, cocaine-, and methamphetamine-use disorders.

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.

Animal Models and the Development of Vaccines to Treat Substance Use Disorders

The development of pharmacotherapies for substance use disorders (SUDs) is a high priority in addiction research. At present, there are no approved pharmacotherapies for cocaine and methamphetamine use disorders, while treatments for nicotine and opioid use are moderately effective. Indeed, many of these treatments can cause adverse drug side effects and have poor medication compliance, which often results in increased drug relapse rates. An alternative to these traditional pharmacological interventions is immunotherapy or vaccines that can target substances associated with SUDs. In this chapter, we discuss the current knowledge on the efficacy of preclinical vaccines, particularly immunogens that target methamphetamine, cocaine, nicotine, or opioids to attenuate drug-induced behaviors in animal models of SUDs. We also review vaccines (and antibodies) against cocaine, nicotine, and methamphetamine that have been assessed in human clinical trials. While preclinical studies indicate that several vaccines show promise, these findings have not necessarily translated to the clinical population. Thus, continued effort to design more effective vaccine immunogens using SUD animal models is necessary in order to support the use of immunotherapy as a viable option for individuals with SUDs.

The Cardiac Complications of Methamphetamines

Methamphetamines are increasingly popular drugs of abuse in Australia, and are rising in purity. The rising popularity and purity of methamphetamines has notably increased demands upon Australian medical services. Methamphetamines are sympathomimetic amines with a range of adverse effects upon multiple organ systems. Cardiovascular complications are the second leading cause of death in methamphetamine abusers, and there appears to be a high prevalence of cardiac pathology. Cardiovascular pathology frequently seen in methamphetamine abusers includes hypertension, aortic dissection, acute coronary syndromes, pulmonary arterial hypertension and methamphetamine-associated cardiomyopathy. The rising prevalence of methamphetamine abuse is likely to increase the burden of cardiovascular pathology in Australians. A National Parliamentary Enquiry was opened in March 2015 to address concerns regarding the medical and social impacts of methamphetamine abuse. From April 2015, a National 'Ice Taskforce' was also created in parallel. Reversal of cardiac pathology appears to be achievable with abstinence from methamphetamines and initiation of appropriate treatment. It is key to appreciate that the pathogenesis of methamphetamine-induced cardiac complications arises as a result of the specific toxic effects of methamphetamines. Clinical management is hence individualised; suggested management approaches for methamphetamine-induced cardiac complications are detailed within this article.

Is immunotherapy an opportunity for effective treatment of drug addiction?

Immunotherapy has a great potential of becoming a new therapeutic strategy in the treatment of addiction to psychoactive drugs. It may be used to treat addiction but also to prevent neurotoxic complications of drug overdose. In preclinical studies two immunological methods have been tested; active immunization, which relies on the administration of vaccines and passive immunization, which relies on the administration of monoclonal antibodies. Until now researchers have succeeded in developing vaccines and/or antibodies against addiction to heroin, cocaine, methamphetamine, nicotine and phencyclidine. Their effectiveness has been confirmed in preclinical studies. At present, clinical studies are being conducted for vaccines against nicotine and cocaine and also anti-methamphetamine monoclonal antibody. These preclinical and clinical studies suggest that immunotherapy may be useful in the treatment of addiction and drug overdose. However, there are a few problems to be solved. One of them is controlling the level of antibodies due to variability between subjects. But even obtaining a suitable antibody titer does not guarantee the effectiveness of the vaccine. Additionally, there is a risk of intentional or unintentional overdose. As vaccines prevent passing of drugs through the blood/brain barrier and thereby prevent their positive reinforcement, some addicted patients may erroneously seek higher doses of psychoactive substances to get "high". Consequently, vaccination should be targeted at persons who have a strong motivation to free themselves from drug dependency. It seems that immunotherapy may be an opportunity for effective treatment of drug addiction if directed to adequate candidates for treatment. For other addicts, immunotherapy may be a very important element supporting psycho- and pharmacotherapy.

Combining Active Immunization with Monoclonal Antibody Therapy To Facilitate Early Initiation of a Long-Acting Anti-Methamphetamine Antibody Response

We hypothesized that an anti-METH mAb could be used in combination with a METH-conjugate vaccine (MCV) to safely improve the overall quality and magnitude of the anti-METH immune response. The benefits would include immediate onset of action (from the mAb), timely increases in the immune responses (from the combined therapy) and duration of antibody response that could last for months (from the MCV). A novel METH-like hapten (METH-SSOO9) was synthesized and then conjugated to immunocyanin monomers of keyhole limpet hemocyanin (IC(KLH)) to create the MCV ICKLH-SOO9. The vaccine, in combination with previously discovered anti-METH mAb7F9, was then tested in rats for safety and potential efficacy. The combination antibody therapy allowed safe achievement of an early high anti-METH antibody response, which persisted throughout the study. Indeed, even after 4 months the METH vaccine antibodies still had the capacity to significantly reduce METH brain concentrations resulting from a 0.56 mg/kg METH dose.