Development of vaccines to treat opioid use disorders and reduce incidence of overdose

A novel strategy to elicit enduring anti-morphine immunity and relief from addiction by targeting Acr1 protein nano vaccine through TLR-2 to dendritic cells

Morphine addiction poses a significant challenge to global healthcare. Current opioid substitution therapies, such as buprenorphine, naloxone and methadone are effective but often lead to dependence. Thus, exploring alternative treatments for opioid addiction is crucial. We have developed a novel vaccine that presents morphine and Pam3Cys (a TLR-2 agonist) on the surface of Acr1 nanoparticles. This vaccine has self-adjuvant properties and targets TLR-2 receptors on antigen-presenting cells, particularly dendritic cells. Our vaccination strategy promotes the proliferation and differentiation of morphine-specific B-cells and Acr1-reactive CD4 T-cells. Additionally, the vaccine elicited the production of high-affinity anti-morphine antibodies, effectively eliminating morphine from the bloodstream and brain in mice. It also reduced the expression of addiction-associated μ-opioid receptor and dopamine genes. The significant increase in memory CD4 T-cells and B-cells indicates the vaccine's ability to induce long-lasting immunity against morphine. This vaccine holds promise as a prophylactic measure against morphine addiction.

Enhancing translation: A need to leverage complex preclinical models of addictive drugs to accelerate substance use treatment options

Preclinical models of addictive drugs have been developed for decades to model aspects of the clinical experience in substance use disorders (SUDs). These include passive exposure as well as volitional intake models across addictive drugs and have been utilized to also measure withdrawal symptomatology and potential neurobehavioral mechanisms underlying relapse to drug seeking or taking. There are a number of Food and Drug Administration (FDA)-approved medications for SUDs, however, many demonstrate low clinical efficacy as well as potential sex differences, and we also note gaps in the continuum of care for certain aspects of clinical experiences in individuals who use drugs. In this review, we provide a comprehensive update on both frequently utilized and novel behavioral models of addiction with a focus on translational value to the clinical experience and highlight the need for preclinical research to follow epidemiological trends in drug use patterns to stay abreast of clinical treatment needs. We then note areas in which models could be improved to enhance the medications development pipeline through efforts to enhance translation of preclinical models. Next, we describe neuroscience efforts that can be leveraged to identify novel biological mechanisms to enhance medications development efforts for SUDs, focusing specifically on advances in brain transcriptomics approaches that can provide comprehensive screening and identification of novel targets. Together, the confluence of this review demonstrates the need for careful selection of behavioral models and methodological parameters that better approximate the clinical experience combined with cutting edge neuroscience techniques to advance the medications development pipeline for SUDs.

Opioid-Based Haptens: Development of Immunotherapy

Over the past decades, extensive preclinical research has been conducted to develop vaccinations to protect against substance use disorder caused by opioids, nicotine, cocaine, and designer drugs. Morphine or fentanyl derivatives are small molecules, and these compounds are not immunogenic, but when conjugated as haptens to a carrier protein will elicit the production of antibodies capable of reacting specifically with the unconjugated hapten or its parent compound. The position of the attachment in opioid haptens to the carrier protein will influence the specificity of the antiserum produced in immunized animals with the hapten-carrier conjugate. Immunoassays for the determination of opioid drugs are based on the ability of drugs to inhibit the reaction between drug-specific antibodies and the corresponding drug-carrier conjugate or the corresponding labelled hapten. Pharmacological studies of the hapten-carrier conjugates resulted in the development of vaccines for treating opioid use disorders (OUDs). Immunotherapy for opioid addiction includes the induction of anti-drug vaccines which are composed of a hapten, a carrier protein, and adjuvants. In this review we survey the design of opioid haptens, the development of the opioid radioimmunoassay, and the results of immunotherapy for OUDs.

Opioid vaccine clinical testing: lessons learned

PURPOSE OF REVIEW

Opioid use disorder (OUD) presents a serious public health concern, with dramatic increases in opioid-overdose mortality in recent years and a small percentage of those with OUD accessing or remaining engaged with available treatments. Efforts are currently underway to identify vaccines targeting opioids, which could provide a novel and complimentary approach. The current review provides an overview of existing literature, practical considerations for designing and conducting clinical trials with vaccines for opioids, and future directions.

RECENT FINDINGS

This review covers the following themes: clinical trial design and selection of endpoints, timepoint selection, practical considerations and lessons learned from the first (ongoing) trial of a vaccine targeting opioids, and future directions.

SUMMARY

Efforts to develop and test vaccines targeting OUD are based on a foundation of preclinical work and close collaboration between preclinical and clinical researchers. Efforts to learn from shortcomings of prior clinical trials of vaccines for other substances are essential in designing and testing effective vaccines for OUD. Design and implementation of clinical trials for a vaccine for OUD requires careful balance of participant safety and strategies for retention and efforts to gather viable data to inform future work.

Identification and biophysical characterization of a novel domain-swapped camelid antibody specific for fentanyl

Opioid use disorders (OUD) and overdoses are ever-evolving public health threats that continue to grow in incidence and prevalence in the United States and abroad. Current treatments consist of opioid receptor agonists and antagonists, which are safe and effective but still suffer from some limitations. Murine and humanized monoclonal antibodies (mAb) have emerged as an alternative and complementary strategy to reverse and prevent opioid-induced respiratory depression. To explore antibody applications beyond traditional heavy-light chain mAbs, we identified and biophysically characterized a novel single-domain antibody specific for fentanyl from a camelid variable-heavy-heavy (VHH) domain phage display library. Structural data suggested that VHH binding to fentanyl was facilitated by a unique domain-swapped dimerization mechanism, which accompanied a rearrangement of complementarity-determining region loops leading to the formation of a fentanyl-binding pocket. Structure-guided mutagenesis further identified an amino acid substitution that improved the affinity and relaxed the requirement for dimerization of the VHH in fentanyl binding. Our studies demonstrate VHH engagement of an opioid and inform on how to further engineer a VHH for enhanced stability and efficacy, laying the groundwork for exploring the in vivo applications of VHH-based biologics against OUD and overdose.

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.

Enhancing Protective Antibodies against Opioids through Antigen Display on Virus-like Particles

Opioid use disorder (OUD) has become a public health crisis, with recent significant increases in the number of deaths due to overdose. Vaccination can provide an attractive complementary strategy to combat OUD. A key for high vaccine efficacy is the induction of high levels of antibodies specific to the drug of abuse. Herein, a powerful immunogenic carrier, virus-like particle mutant bacteriophage Qβ (mQβ), has been investigated as a carrier of a small molecule hapten 6-AmHap mimicking heroin. The mQβ-6-AmHap conjugate was able to induce significantly higher levels of IgG antibodies against 6-AmHap than mice immunized with the corresponding tetanus toxoid-6-AmHap conjugate in head-to-head comparison studies in multiple strains of mice. The IgG antibody responses were persistent with high anti-6-AmHap titers 600 days after being immunized with mQβ-6-AmHap. The antibodies induced exhibited strong binding toward multiple heroin/morphine derivatives that have the potential to be abused, while binding weakly to medications used for OUD treatment and pain relief. Furthermore, vaccination effectively reduced the impacts of morphine on mice in both ambulation and antinociception assays, highlighting the translational potential of the mQβ-6-AmHap conjugate to mitigate the harmful effects of drugs of abuse.

Multivalent Vaccination Strategies Protect against Exposure to Polydrug Opioid and Stimulant Mixtures in Mice and Rats

Illicit drug mixtures containing opioids and stimulants have been responsible for the majority of fatal drug overdoses among occasional users, and those with either opioid use disorder (OUD) or substance use disorder (SUD). As a complementary strategy to current pharmacotherapies, active immunization with conjugate vaccines has been proposed as a viable intervention to treat OUD as well as other SUD for which there are either limited or no treatment options. Vaccination against opioids and stimulants could help address the limitations of current medications (e.g., patient access, compliance, misuse liability, and safety) by providing an additional tool to prevent drug misuse and/or overdoses. However, more research is needed to fully understand the potential benefits and limitations of using vaccines to treat SUD and overdose and to inform us on how to deploy this strategy in the field. Previous reports have shown promise by combining two vaccines into bivalent vaccine formulations to concurrently target multiple drugs. Here, multiple individual candidate monovalent vaccines were incrementally combined in multivalent vaccine formulations to simultaneously target fentanyl, carfentanil, oxycodone, heroin, methamphetamine, and their analogs or metabolites. Bi-, tri-, and quadrivalent vaccine formulations induced the formation of independent serum antibody responses against their respective opioid targets and selectively attenuated the distribution of each individual drug to the brain in mice and rats. Results indicate that a single injection of an admixed multivalent vaccine formulation may be more effective than coinjecting multiple monovalent vaccines at multiple sites. Finally, adding a methamphetamine conjugate vaccine to an quadrivalent opioid vaccine in a pentavalent formulation did not interfere with the production of effective antiopioid IgG antibodies. Multivalent vaccines could provide multifaceted, yet selective, protection against polydrug use and exposure.

Daily methocinnamox treatment dose-dependently attenuates fentanyl self-administration in rhesus monkeys

Opioid use disorder and opioid overdose continue to be significant public health challenges despite the availability of effective treatments. Methocinnamox (MCAM) is a novel, long-acting opioid receptor antagonist that might be an effective treatment for opioid use disorder (i.e., preventing relapse and overdose). In nonhuman primates, MCAM selectively blocks the positive reinforcing effects of mu opioid receptor agonists, including heroin, fentanyl, and its ultra-potent analogs (e.g., carfentanil) with a single administration of MCAM being effective for up to two weeks. Because treatment of opioid use disorder would involve repeated administration of a medication, MCAM was studied in rhesus monkeys (3 males and 2 females) responding under a fixed-ratio self-administration procedure for a range of doses of fentanyl (0.000032-0.1 mg/kg/infusion). The fentanyl self-administration dose-effect curve was determined before and during treatment with progressively increasing daily doses of MCAM (0.001-0.1 mg/kg) given subcutaneously 1 h before the session. MCAM dose-dependently shifted the fentanyl dose-effect curve rightward and then, at larger doses, downward. The largest treatment dose of MCAM (0.1 mg/kg/day) shifted the curve more than 120-fold rightward with monkeys receiving doses much larger than the likely lethal dose of fentanyl with no adverse effect or observable change in behavior. This study demonstrates that MCAM reliably and dose-dependently decreases fentanyl self-administration and prevents opioid overdose, with no evidence of adverse effects over a broad dose range, further supporting the potential therapeutic utility of this novel antagonist.

A bacteriophage virus-like particle vaccine against oxycodone elicits high-titer and long-lasting antibodies that sequester drug in the blood

Opioid use disorder (OUD) and opioid overdoses are public health emergencies. In 2021, 80,000 opioid overdose associated deaths were reported in the United States. Despite the availability of treatment strategies, including medications for opioid use disorder (MOUD) and naloxone, opioid overdoses continue to increase at an alarming rate. Opioid vaccines are a novel approach to combat the growing crisis with several candidates recently entering human clinical trials. In this study, we investigated Qβ bacteriophage virus-like particles (VLPs) as a vaccine platform for immunogenic display of oxycodone. A derivative of oxycodone was conjugated to pre-formed Qβ VLPs using a sulfhydryl-amine reactive heterobifunctional crosslinker with high loading of oxycodone. In mice, intramuscular immunization with Qβ-oxycodone elicited high-titer, high-avidity and long-lasting antibody responses. Qβ-oxycodone was also immunogenic after storage at ambient room temperature for over two weeks, demonstrating that the vaccine is highly thermostable. In mice, immunization with Qβ-oxycodone elicited antibodies that sequester oxycodone in the serum, an important mechanism for preventing the adverse effects of opioid activity. Finally, Qβ-oxycodone is immunogenic in nonhuman primates, eliciting serum oxycodone antibodies after intramuscular immunization of rhesus macaques. These data establish Qβ-oxycodone as a promising opioid vaccine candidate.

Oxycodone: A Current Perspective on Its Pharmacology, Abuse, and Pharmacotherapeutic Developments

Oxycodone, a semisynthetic derivative of naturally occurring thebaine, an opioid alkaloid, has been available for more than 100 years. Although thebaine cannot be used therapeutically due to the occurrence of convulsions at higher doses, it has been converted to a number of other widely used compounds that include naloxone, naltrexone, buprenorphine, and oxycodone. Despite the early identification of oxycodone, it was not until the 1990s that clinical studies began to explore its analgesic efficacy. These studies were followed by the pursuit of several preclinical studies to examine the analgesic effects and abuse liability of oxycodone in laboratory animals and the subjective effects in human volunteers. For a number of years oxycodone was at the forefront of the opioid crisis, playing a significant role in contributing to opioid misuse and abuse, with suggestions that it led to transitioning to other opioids. Several concerns were expressed as early as the 1940s that oxycodone had significant abuse potential similar to heroin and morphine. Both animal and human abuse liability studies have confirmed, and in some cases amplified, these early warnings. Despite sharing a similar structure with morphine and pharmacological actions also mediated by the μ-opioid receptor, there are several differences in the pharmacology and neurobiology of oxycodone. The data that have emerged from the many efforts to analyze the pharmacological and molecular mechanism of oxycodone have generated considerable insight into its many actions, reviewed here, which, in turn, have provided new information on opioid receptor pharmacology. SIGNIFICANCE STATEMENT: Oxycodone, a μ-opioid receptor agonist, was synthesized in 1916 and introduced into clinical use in Germany in 1917. It has been studied extensively as a therapeutic analgesic for acute and chronic neuropathic pain as an alternative to morphine. Oxycodone emerged as a drug with widespread abuse. This article brings together an integrated, detailed review of the pharmacology of oxycodone, preclinical and clinical studies of pain and abuse, and recent advances to identify potential opioid analgesics without abuse liability.

The effect of chronic stress on the immunogenicity and immunoprotection of the M6-TT vaccine in female mice

Active vaccination is an effective therapeutic option to reduce the reinforcing effects of opioids. Several studies showed that chronic stress affects the immune system decreasing the efficiency of some vaccines. Heroin withdrawal is a stressor and it is a stage in which the patient who abuses heroin is vulnerable to stress affects the immune response and consequently its immunoprotective capacity, then, the objective was to determine the effect of heroin-withdrawal and heroin-withdrawal plus immobilization, on the immune (immunogenicity) and protective response (behavioral response) of morphine-6-hemisuccinate-tetanus toxoid (M6-TT) vaccine in animals of two inbred mice strains with different sensitivity to drug-opioid and stress. Female BALB/c and C57Bl/6 inbred mice were immunized with the M6-TT. A solid-phase antibody-capture ELISA was used to monitor antibody titer responses after each booster dose in vaccinated animals. During the vaccination period, the animals were subjected to two different stress conditions: drug-withdrawal (DW) and immobilization (IMM). The study used tail-flick testing to evaluate the heroin-induced antinociceptive effects. Additionally, heroin-induced locomotor activity was evaluated. Stress decreased the heroin-specific antibody titer generated by the M6-TT vaccine in the two inbred mouse strains evaluated. In the two stress conditions, the antibody titer was not able to decrease the heroin-induced antinociceptive effects and locomotor activity. These findings suggest that stress decreases the production of antibodies and the immunoprotective capacity of the M6-TT vaccine. This observation is important to determine the efficacy of active vaccination as a potential therapy for patients with opioid drug use disorder, since these patients during drug-withdrawal present stress disorders, which could affect the efficacy of therapy such as active vaccination.

Diamino Allose Phosphates: Novel, Potent, and Highly Stable Toll-like Receptor 4 Agonists

Most known synthetic toll-like receptor 4 (TLR4) agonists are carbohydrate-based lipid-A mimetics containing several fatty acyl chains, including a labile 3-O-acyl chain linked to the C-3 position of the non-reducing sugar known to undergo cleavage impacting stability and resulting in loss of activity. To overcome this inherent instability, we rationally designed a new class of chemically more stable synthetic TLR4 ligands that elicit robust innate and adaptive immune responses. This new class utilized a diamino allose phosphate (DAP) scaffold containing a nonhydrolyzable 3-amide bond instead of the classical 3-ester. Accordingly, the DAPs have significantly improved thermostability in aqueous formulations and potency relative to other known natural and synthetic TLR4 ligands. Furthermore, the DAP analogues function as potent vaccine adjuvants to enhance influenza-specific antibodies in mice and provide protection against lethal influenza virus challenges. This novel set of TLR4 ligands show promise as next-generation vaccine adjuvants and stand-alone immunomodulators.

Self-Adjuvanting TLR7/8 Agonist and Fentanyl Hapten Co-Conjugate Achieves Enhanced Protection against Fentanyl Challenge

Currently approved pharmacotherapies for opioid use disorders (OUDs) and overdose reversal agents are insufficient to slow the spread of OUDs due to the proliferation of fentanyl. This is evident in the 31% rise in drug overdose deaths from 2019 to 2022, with rates increasing from 21.6 to 28.3 overdoses per 100,000 deaths. Vaccines are a potential alternative or adjunct therapy for the treatment of several substance use disorders (nicotine, cocaine) but have shown limited clinical success due to suboptimal antibody titers. In this study, we demonstrate that coconjugation of a Toll-like receptor 7/8 (TLR7/8) agonist (UM-3006) alongside a fentanyl-based hapten (F1) on the surface of the carrier protein cross-reactive material 197 (CRM) significantly increased generation of high-affinity fentanyl-specific antibodies. This demonstrated enhanced protection against fentanyl challenges relative to an unconjugated (admix) adjuvant control in mice. Inclusion of aluminum hydroxide (alum) adjuvant further increased titers and enhanced protection, as determined by analysis of fentanyl concentration in serum and brain tissue. Collectively, our findings present a promising approach to enhance the efficacy of antiopioid vaccines, underscoring the need for extensive exploration of TLR7/8 agonist conjugates as a compelling strategy to combat opioid use disorders.

Synthetic Anti-Cocaine Nanoaccine Successfully Prevents Cocaine-Induced Hyperlocomotion

Cocaine is one of the most widely used and increasingly popular illicit psychoactive drugs. Unlike other commonly used substances of abuse, cocaine has no pharmacological therapies to treat addiction or aid in rehabilitation. Immunopharmacology has long been touted as a possible avenue to develop effective anticocaine therapies; however, lack of efficacy and designs which are not consistent with simple large-scale production have hindered vaccine translation. We have designed and synthesized a peptide-based anti-cocaine immunogen which we have shown is capable of inducing physiologically relevant immune responses in mice as part of a self-adjuvanting delivery system or in combination with the human-approved commercial adjuvant MF59. We have demonstrated that immunization with the reported vaccine elicits high titers of anti-cocaine IgG and prevents cocaine-induced hyperlocomotion in an in vivo murine model. This peptide-hapten immunogen along with self-adjuvanting liposomal-based delivery system provides a platform for the development of effective anti-drug vaccines.

A TLR7/8 agonist increases efficacy of anti-fentanyl vaccines in rodent and porcine models

Opioid use disorders (OUD) and overdose are public health threats worldwide. Widespread access to highly potent illicit synthetic opioids such as fentanyl is driving the recent rise in fatal overdoses. Vaccines containing fentanyl-based haptens conjugated to immunogenic carrier proteins offer a long-lasting, safe, and cost-effective strategy to protect individuals from overdose upon accidental or deliberate exposure to fentanyl and its analogs. Prophylactic or therapeutic active immunization with an anti-fentanyl vaccine induces the production of fentanyl-specific antibodies that bind the drug in the blood and prevent its distribution to the brain, which reduces its reinforcing effects and attenuates respiratory depression and bradycardia. To increase the efficacy of a lead anti-fentanyl vaccine, this study tested whether the incorporation of synthetic toll-like receptor (TLR) 4 and TLR7/8 agonists as vaccine adjuvants would increase vaccine efficacy against fentanyl challenge, overdose, and self-administration in either rats or Hanford miniature pigs. Formulation of the vaccine with a nucleolipid TLR7/8 agonist enhanced its immunogenicity and efficacy in preventing fentanyl-induced respiratory depression, analgesia, bradycardia, and self-administration in either rats or mini-pigs. These studies support the use of TLR7/8 adjuvants in vaccine formulations to improve their clinical efficacy against OUD and potentially other substance use disorders (SUD).

A lipidated TLR7/8 adjuvant enhances the efficacy of a vaccine against fentanyl in mice

Opioid use disorders (OUD) and opioid-related fatal overdoses are a public health concern in the United States. Approximately 100,000 fatal opioid-related overdoses occurred annually from mid-2020 to the present, the majority of which involved fentanyl or fentanyl analogs. Vaccines have been proposed as a therapeutic and prophylactic strategy to offer selective and long-lasting protection against accidental or deliberate exposure to fentanyl and closely related analogs. To support the development of a clinically viable anti-opioid vaccine suitable for human use, the incorporation of adjuvants will be required to elicit high titers of high-affinity circulating antibodies specific to the target opioid. Here we demonstrate that the addition of a synthetic TLR7/8 agonist, INI-4001, but not a synthetic TLR4 agonist, INI-2002, to a candidate conjugate vaccine consisting of a fentanyl-based hapten, F1, conjugated to the diphtheria cross-reactive material (CRM), significantly increased generation of high-affinity F1-specific antibody concentrations, and reduced drug distribution to the brain after fentanyl administration in mice.

Development of a vaccine against the synthetic opioid U-47700

Opioid use disorders and overdose have become a major public health concern in recent years. U-47700, a New psychoactive substances (NPS) opioid, also known as "pinky" or "pink" has been identified as a new threat in the drug supply because of its potency and abuse potential. Conjugate vaccines that can produce antibodies against target drug molecules have emerged as a promising tool to treat substance use disorders. Herein, we report the design, synthesis, and in vivo characterization of a U-47700 vaccine. The vaccine demonstrated favorable results with rodents producing elevated levels of antibody titer and sub-micromolar affinity to U-47700. In addition, antibodies generated by the vaccine effectively mitigated drug-induced effects by preventing the drug from penetrating the blood-brain barrier, which was verified by antinociception and drug biodistribution studies. The development of a vaccine against U-47700 and other NPS opioids contributes to the continued advancement of non-conventional pharmacological treatments to address the global opioid epidemic.

Chemical tools for the opioids

The opioids are potent and widely used pain management medicines despite also possessing severe liabilities that have fueled the opioid crisis. The pharmacological properties of the opioids primarily derive from agonism or antagonism of the opioid receptors, but additional effects may arise from specific compounds, opioid receptors, or independent targets. The study of the opioids, their receptors, and the development of remediation strategies has benefitted from derivatization of the opioids as chemical tools. While these studies have primarily focused on the opioids in the context of the opioid receptors, these chemical tools may also play a role in delineating mechanisms that are independent of the opioid receptors. In this review, we describe recent advances in the development and applications of opioid derivatives as chemical tools and highlight opportunities for the future.

Future perspectives of emerging novel drug targets and immunotherapies to control drug addiction

Substance Use Disorder (SUD) is one of the major mental illnesses that is terrifically intensifying worldwide. It is becoming overwhelming due to limited options for treatment. The complexity of addiction disorders is the main impediment to understanding the pathophysiology of the illness. Hence, unveiling the complexity of the brain through basic research, identification of novel signaling pathways, the discovery of new drug targets, and advancement in cutting-edge technologies will help control this disorder. Additionally, there is a great hope of controlling the SUDs through immunotherapeutic measures like therapeutic antibodies and vaccines. Vaccines have played a cardinal role in eliminating many diseases like polio, measles, and smallpox. Further, vaccines have controlled many diseases like cholera, dengue, diphtheria, Haemophilus influenza type b (Hib), human papillomavirus, influenza, Japanese encephalitis, etc. Recently, COVID-19 was controlled in many countries by vaccination. Currently, continuous effort is done to develop vaccines against nicotine, cocaine, morphine, methamphetamine, and heroin. Antibody therapy against SUDs is another important area where serious attention is required. Antibodies have contributed substantially against many serious diseases like diphtheria, rabies, Crohn's disease, asthma, rheumatoid arthritis, and bladder cancer. Antibody therapy is gaining immense momentum due to its success rate in cancer treatment. Furthermore, enormous advancement has been made in antibody therapy due to the generation of high-efficiency humanized antibodies with a long half-life. The advantage of antibody therapy is its instant outcome. This article's main highlight is discussing the drug targets of SUDs and their associated mechanisms. Importantly, we have also discussed the scope of prophylactic measures to eliminate drug dependence.

Understanding the habenula: A major node in circuits regulating emotion and motivation

Over the last decade, the understanding of the habenula has rapidly advanced from being an understudied brain area with the Latin name 'habena" meaning "little rein", to being considered a "major rein" in the control of key monoaminergic brain centers. This ancient brain structure is a strategic node in the information flow from fronto-limbic brain areas to brainstem nuclei. As such, it plays a crucial role in regulating emotional, motivational, and cognitive behaviors and has been implicated in several neuropsychiatric disorders, including depression and addiction. This review will summarize recent findings on the medial (MHb) and lateral (LHb) habenula, their topographical projections, cell types, and functions. Additionally, we will discuss contemporary efforts that have uncovered novel molecular pathways and synaptic mechanisms with a focus on MHb-Interpeduncular nucleus (IPN) synapses. Finally, we will explore the potential interplay between the habenula's cholinergic and non-cholinergic components in coordinating related emotional and motivational behaviors, raising the possibility that these two pathways work together to provide balanced roles in reward prediction and aversion, rather than functioning independently.

Understanding and countering opioid-induced respiratory depression

Respiratory depression is the proximal cause of death in opioid overdose, yet the mechanisms underlying this potentially fatal outcome are not well understood. The goal of this review is to provide a comprehensive understanding of the pharmacological mechanisms of opioid-induced respiratory depression, which could lead to improved therapeutic options to counter opioid overdose, as well as other detrimental effects of opioids on breathing. The development of tolerance in the respiratory system is also discussed, as are differences in the degree of respiratory depression caused by various opioid agonists. Finally, potential future therapeutic agents aimed at reversing or avoiding opioid-induced respiratory depression through non-opioid receptor targets are in development and could provide certain advantages over naloxone. By providing an overview of mechanisms and effects of opioids in the respiratory network, this review will benefit future research on countering opioid-induced respiratory depression. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.

A trypanosome-derived immunotherapeutics platform elicits potent high-affinity antibodies, negating the effects of the synthetic opioid fentanyl

Poorly immunogenic small molecules pose challenges for the production of clinically efficacious vaccines and antibodies. To address this, we generate an immunization platform derived from the immunogenic surface coat of the African trypanosome. Through sortase-based conjugation of the target molecules to the variant surface glycoprotein (VSG) of the trypanosome surface coat, we develop VSG-immunogen array by sortase tagging (VAST). VAST elicits antigen-specific memory B cells and antibodies in a murine model after deploying the poorly immunogenic molecule fentanyl as a proof of concept. We also develop a single-cell RNA sequencing (RNA-seq)-based computational method that synergizes with VAST to specifically identify memory B cell-encoded antibodies. All computationally selected antibodies bind to fentanyl with picomolar affinity. Moreover, these antibodies protect mice from fentanyl effects after passive immunization, demonstrating the ability of these two coupled technologies to elicit therapeutic antibodies to challenging immunogens.

Structures of drug-specific monoclonal antibodies bound to opioids and nicotine reveal a common mode of binding

Opioid-related fatal overdoses have reached epidemic proportions. Because existing treatments for opioid use disorders offer limited long-term protection, accelerating the development of newer approaches is critical. Monoclonal antibodies (mAbs) are an emerging treatment strategy that targets and sequesters selected opioids in the bloodstream, reducing drug distribution across the blood-brain barrier, thus preventing or reversing opioid toxicity. We previously identified a series of murine mAbs with high affinity and selectivity for oxycodone, morphine, fentanyl, and nicotine. To determine their binding mechanism, we used X-ray crystallography to solve the structures of mAbs bound to their respective targets, to 2.2 Å resolution or higher. Structural analysis showed a critical convergent hydrogen bonding mode that is dependent on a glutamic acid residue in the mAbs' heavy chain and a tertiary amine of the ligand. Characterizing drug-mAb complexes represents a significant step toward rational antibody engineering and future manufacturing activities to support clinical evaluation.

Clinical Trial Design Challenges and Opportunities for Emerging Treatments for Opioid Use Disorder: A Review

Importance

Novel treatments for opioid use disorder (OUD) are needed to address both the ongoing opioid epidemic and long-standing barriers to existing OUD treatments that target the endogenous μ-opioid receptor (MOR) system. The goal of this review is to highlight unique clinical trial design considerations for the study of emerging treatments for OUD that address targets beyond the MOR system. In November 2019, the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership with the US Food and Drug Administration sponsored a meeting to discuss the current evidence regarding potential treatments for OUD, including cannabinoids, psychedelics, sedative-hypnotics, and immunotherapeutics, such as vaccines.

Observations

Consensus recommendations are presented regarding the most critical elements of trial design for the evaluation of novel OUD treatments, such as: (1) stage of treatment that will be targeted (eg, seeking treatment, early abstinence/detoxification, long-term recovery); (2) role of treatment (adjunctive with or independent of existing OUD treatments); (3) primary outcomes informed by patient preferences that assess opioid use (including changes in patterns of use), treatment retention, and/or global functioning and quality of life; and (4) adverse events, including the potential for opioid-related relapse or overdose, especially if the patient is not simultaneously taking maintenance MOR agonist or antagonist medications.

Conclusions and Relevance

Applying the recommendations provided here as well as considering input from people with lived experience in the design phase will accelerate the development, translation, and uptake of effective and safe therapeutics for individuals struggling with OUD.

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.

Lessons from COVID-19 to increase opioid vaccine acceptance

COVID-19 has put vaccine efficacy under a spotlight. However, the reluctance of people to be vaccinated has postponed the end of the COVID-19 pandemic. Currently, opioid vaccines are being developed, which could help prevent opioid addiction, overdoses, or relapse in combination with medication-assisted therapy. The fear is that the uptake of opioid vaccines could be met by the same reluctance as seen with COVID-19 vaccines.

An Immunconjugate Vaccine Alters Distribution and Reduces the Antinociceptive, Behavioral and Physiological Effects of Fentanyl in Male and Female Rats

Fentanyl (FEN) is a potent synthetic opioid associated with increasing incidence of opioid use disorder (OUD) and fatal opioid overdose. Vaccine immunotherapy for FEN-associated disorders may be a viable therapeutic strategy. Here, we expand and confirm our previous study in mice showing immunological and antinociception efficacy of our FEN vaccine administered with the adjuvant dmLT. In this study, immunized male and female rats produced significant levels of anti-FEN antibodies that were highly effective at neutralizing FEN-induced antinociception in the tail flick assay and hot plate assays. The vaccine also decreased FEN brain levels following drug administration. Immunization blocked FEN-induced, but not morphine-induced, rate-disrupting effects on schedule-controlled responding. Vaccination prevented decreases on physiological measures (oxygen saturation, heart rate) and reduction in overall activity following FEN administration in male rats. The impact of FEN on these measures was greater in unvaccinated male rats compared to unvaccinated female rats. Cross-reactivity assays showed anti-FEN antibodies bound to FEN and sufentanil but not to morphine, methadone, buprenorphine, or oxycodone. These data support further clinical development of this vaccine to address OUD in humans.

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.

6-Monoacetylmorphine-antibody distribution in tissues from heroin-related death cases: An experimental study to investigate the distributive response

Heroin, a semisynthetic opioid drug synthesized from morphine, is the 3,6-diacetyl ester of morphine (diacetylmorphine). The post-mortem diagnosis of heroin-related death could be an issue and usually rely on a combination of investigations, including the autopsy, histological and toxicological analysis. We conducted the present study to evaluate the correlation between the heroin concentration in biological fluids (peripheral blood, bile and urine) and the post-mortem anti-6-MAM antibody expression in various tissues (brain, heart, lung, liver and kidney) using immunohistochemical staining. A quantitative analysis of the immunohistochemical reaction was carried out. 45 cases of heroin-related death investigated at the Forensic Pathology Institutes of the University of Rome, Foggia and Pisa were included. The control group was composed of 15 cases of death due to other causes, without brain lesions and negative toxicological analysis for drugs. We found a positive immunohistochemical reaction in different organs and it was related to the timing of heroin metabolization. No reaction was found in the control group. Our findings show that immunohistochemistry can be a valuable tool for the post-mortem diagnosis of acute heroin abuse. A better understanding of the timing of heroin's metabolism can be useful in the forensic field and for future therapeutic applications.

A Rapid Method for Direct Quantification of Antibody Binding-Site Concentration in Serum

The quantitation of the available antibody binding-site concentration of polyclonal antibodies in serum is critical in defining the efficacy of vaccines against substances of abuse. We have conceptualized an equilibrium dialysis (ED)-based approach coupled with fluorimetry (ED-fluorimetry) to measure the antibody binding-site concentration to the ligand in an aqueous environment. The measured binding-site concentrations in monoclonal antibody (mAb) and sera samples from TT-6-AmHap-immunized rats by ED-fluorimetry are in agreement with those determined by a more established equilibrium dialysis coupled with ultraperformance liquid chromatography tandem mass spectrometry (ED-UPLC-MS/MS). Importantly, we have shown that the measured antibody binding-site concentrations to the ligand by ED-fluorimetry were not influenced by the sample serum matrix; thus, this method is valid for determining the binding-site concentration of polyclonal antibodies in sera samples. Further, we have demonstrated that under appropriate analytical conditions, this method resolved the total binding-site concentrations on a nanomolar scale with good accuracy and repeatability within the microliter sample volumes. This simple, rapid, and sample preparation-free approach has the potential to reliably perform quantitative antibody binding-site screening in serum and other more complex biological fluids.

Vaccines against Drug Abuse—Are We There Yet?

Background: Drug abuse is a worldwide problem that is detrimental to public health. The potential for drug abuse extends to both legal and illicit drugs. Drawbacks associated with current treatments include limited effectiveness, potential side effects and, in some instances, the absence of or concerns with approved therapy options. A significant amount of clinical research has been conducted investigating immunotherapy as a treatment option against drug abuse. Vaccines against drug abuse have been the main area of research, and are the focus of this review. Methods: An extensive search using “EBSCOhost (Multiple database collection)” with all 28 databases enabled (including “Academic Search Ultimate”, “CINAHL Plus with Full Text”, and MEDLINE), interrogation of the ClinicalTrials.gov website, and searches of individual clinical trial registration numbers, was performed in February and March of 2022. This search extended to references within the obtained articles. Results: A total of 23 registered clinical trials for treating drug abuse were identified: 15 for treatment of nicotine abuse (all vaccine-based trials), 6 against cocaine abuse (4 were vaccine-based trials and 2 were metabolic-enzyme-based trials), 1 against methamphetamine abuse (a monoclonal-antibody-based trial), and 1 multivalent opioid treatment (vaccine-based trial). As indicated on the ClinicalTrials.gov website (Home—ClinicalTrials.gov), the status of all but two of these trials was “Completed”. Phase 3 clinical trials were completed for vaccine treatments against nicotine and cocaine abuse only. Conclusion: Evidence in the form of efficacy data indicates that vaccines are not an option for treating nicotine or cocaine abuse. Efficacy data are yet to be obtained through completion of clinical trials for vaccines against opioid abuse. These findings align with the absence of regulatory approval for any of these treatments. This review further highlights the need for novel treatment strategies in instances where patients do not respond to current treatments, and while the search for efficacious vaccine-based treatments continues.

Preclinical Efficacy and Selectivity of Vaccines Targeting Fentanyl, Alfentanil, Sufentanil, and Acetylfentanyl in Rats

The ongoing public health emergency of opioid use disorders (OUD) and overdose in the United States is largely driven by fentanyl and its related analogues and has resulted in over 75 673 deaths in 2021. Immunotherapeutics such as vaccines have been investigated as a potential interventional strategy complementary to current pharmacotherapies to reduce the incidence of OUD and opioid-related overdose. Given the importance of targeting structurally distinct fentanyl analogues, this study compared a previously established lead conjugate vaccine (F₁-CRM) to a series of novel vaccines incorporating haptens derived from alfentanil and acetylfentanyl (F_{8, 9a, 9b, 10}), and evaluated their efficacy against drug-induced pharmacological effects in rats. While no vaccine tested provided significant protection against alfentanil, lead formulations were effective in reducing antinociception, respiratory depression, and bradycardia elicited by fentanyl, sufentanil, and acetylfentanyl. Compared with control, vaccination with F₁-CRM also reduced drug levels in the brain of rats challenged with lethal doses of fentanyl. These data further support investigation of F₁-CRM as a candidate vaccine against fentanyl and selected analogues.

Unique Pharmacology, Brain Dysfunction, and Therapeutic Advancements for Fentanyl Misuse and Abuse

Fentanyl is a fully synthetic opioid with analgesic and anesthetic properties. It has become a primary driver of the deadliest opioid crisis in the United States and elsewhere, consequently imposing devastating social, economic, and health burdens worldwide. However, the neural mechanisms that underlie the behavioral effects of fentanyl and its analogs are largely unknown, and approaches to prevent fentanyl abuse and fentanyl-related overdose deaths are scarce. This review presents the abuse potential and unique pharmacology of fentanyl and elucidates its potential mechanisms of action, including neural circuit dysfunction and neuroinflammation. We discuss recent progress in the development of pharmacological interventions, anti-fentanyl vaccines, anti-fentanyl/heroin conjugate vaccines, and monoclonal antibodies to attenuate fentanyl-seeking and prevent fentanyl-induced respiratory depression. However, translational studies and clinical trials are still lacking. Considering the present opioid crisis, the development of effective pharmacological and immunological strategies to prevent fentanyl abuse and overdose are urgently needed.

Development of : A Potent, Highly Selective, and Systemically Active Orthosteric Antagonist of the M5 Muscarinic Acetylcholine Receptor for the Treatment of Opioid Use Disorder

The muscarinic acetylcholine receptor (mAChR) subtype 5 (M₅) represents a novel potential target for the treatment of multiple addictive disorders, including opioid use disorder. Through chemical optimization of several functional high-throughput screening hits, VU6019650 (27b) was identified as a novel M₅ orthosteric antagonist with high potency (human M₅ IC₅₀ = 36 nM), M₅ subtype selectivity (>100-fold selectivity against human M_1-4) and favorable physicochemical properties for systemic dosing in preclinical addiction models. In acute brain slice electrophysiology studies, 27b blocked the nonselective muscarinic agonist oxotremorine-M-induced increases in neuronal firing rates of midbrain dopamine neurons in the ventral tegmental area, a part of the mesolimbic dopaminergic reward circuitry. Moreover, 27b also inhibited oxycodone self-administration in male Sprague-Dawley rats within a dose range that did not impair general motor output.

A Scoping Review of Drug Epidemic Models

The phenomenon of drug epidemics has been a global issue in the past decades, causing enormous damages to the physical and mental health of drug users and social well-being. Despite great efforts to curb drug epidemics at the governmental or social level, the total number of drug users has still been on the rise in recent years, along with illicit production and trafficking around the world. Inspired by dynamical epidemic models of infectious disease, a flourishment of promising results has been observed in the exploration of drug epidemic models. In this review, we aim to provide a scoping review of all existing drug epidemic modeling studies, and it has been shown that most studies focused on analyses of theoretical behaviors of the model systems, lacking emphasis on practical applications in real settings. We found that the drug epidemic models were characterized by a longer time scale, no incubation period, no significant prevention vaccines interfered, and population specificity. This review could assist policymakers and public health workers in gaining deeper insights into modeling tools, and help modelers improve their works, thus narrowing gaps between mathematical epidemiology and public health studies.

Advances in Reversal Strategies of Opioid-induced Respiratory Toxicity

Opioids may produce life-threatening respiratory depression and death from their actions at the opioid receptors within the brainstem respiratory neuronal network. Since there is an increasing number of conditions where the administration of the opioid receptor antagonist naloxone is inadequate or undesired, there is an increased interest in the development of novel reversal and prevention strategies aimed at providing efficacy close to that of the opioid receptor antagonist naloxone but with fewer of its drawbacks such as its short duration of action and lesser ability to reverse high-affinity opioids, such as carfentanil, or drug combinations. To give an overview of this highly relevant topic, the authors systematically discuss predominantly experimental pharmacotherapies, published in the last 5 yr, aimed at reversal of opioid-induced respiratory depression as alternatives to naloxone. The respiratory stimulants are discussed based on their characteristics and mechanism of action: nonopioid controlled substances (e.g., amphetamine, cannabinoids, ketamine), hormones (thyrotropin releasing hormone, oxytocin), nicotinic acetylcholine receptor agonists, ampakines, serotonin receptor agonists, antioxidants, miscellaneous peptides, potassium channel blockers acting at the carotid bodies (doxapram, ENA001), sequestration techniques (scrubber molecules, immunopharmacotherapy), and opioids (partial agonists/antagonists). The authors argue that none of these often still experimental therapies are sufficiently tested with respect to efficacy and safety, and many of the agents presented have a lesser efficacy at deeper levels of respiratory depression, i.e., inability to overcome apnea, or have ample side effects. The authors suggest development of reversal strategies that combine respiratory stimulants with naloxone. Furthermore, they encourage collaborations between research groups to expedite development of viable reversal strategies of potent synthetic opioid-induced respiratory depression.

Housing conditions and microbial environment do not affect the efficacy of vaccines for treatment of opioid use disorders in mice and rats

Vaccines offer a promising prophylactic and therapeutic intervention to counteract opioid use disorders (OUD) and fatal overdoses. Vaccines generate opioid-specific antibodies that bind the target opioid, reducing drug distribution to the brain and preventing drug-induced behavioral and pharmacological effects. Due to their selectivity, anti-opioid vaccines can be administered in combination with FDA-approved medications. Because patients with OUD or other substance use disorders may be affected by other multifactorial co-morbidities, such as infection or depression, it is important to test whether vaccine efficacy is modified by factors that may impact individual innate or adaptive immunity. To that end, this study tested whether housing conditions would affect the efficacy of two lead vaccine formulations targeting oxycodone and fentanyl in male mice and rats, and further analyzed whether differences in the gastrointestinal (GI) microbiome would be correlated with either vaccine efficacy or housing conditions. Results showed that housing mice and rats in either conventional (non-controlled) or specific pathogen-free (SPF, sterile barrier maintained) environment did not affect vaccine-induced antibody responses against oxycodone and fentanyl, nor their efficacy against oxycodone- and fentanyl-induced antinociception, respiratory depression, and bradycardia. Differences in the GI microbiome detected via 16S rRNA gene sequencing were related to the housing environment. This study supports use of anti-opioid vaccines in clinical populations that may display deficits in microbiome function.

Evaluation of G protein bias and β-arrestin 2 signaling in opioid-induced respiratory depression

Respiratory depression is a potentially fatal side effect of opioid analgesics and a major limitation to their use. G protein-biased opioid agonists have been proposed as "safer" analgesics with less respiratory depression. These agonists are biased to activate G proteins rather than β-arrestin signaling. Respiratory depression has been shown to correlate with both G protein bias and intrinsic efficacy, and recent work has refuted the role of β-arrestin signaling in opioid-induced respiratory depression. In addition, there is substantial evidence that G proteins do, in fact, mediate respiratory depression by actions in respiratory-controlling brainstem neurons. Based on these studies, we provide the perspective that protection from respiratory depression displayed by newly developed G protein-biased agonists is due to factors other than G protein versus arrestin bias.

Morphine alkaloids: History, biology, and synthesis

This chapter provides a short overview of the history of morphine since it's isolation by Sertürner in 1805. The biosynthesis of the title alkaloid as well as all total and formal syntheses of morphine and codeine published after 1996 are discussed in detail. The last section of this chapter provides a detailed overview of medicinally relevant derivatives of the title alkaloid.

Contribution of Antibody-Mediated Effector Functions to the Mechanism of Efficacy of Vaccines for Opioid Use Disorders

Vaccines and mAbs offer promising strategies to treat substance use disorders (SUDs) and prevent overdose. Despite vaccines and mAbs against SUDs demonstrating proof of efficacy, selectivity, and safety in animal models, it is unknown whether the mechanism of action of these immunotherapeutics relies exclusively on the formation of Ab/drug complexes, or also involves Ab-mediated effector functions. Hence, this study tested whether the efficacy of active and passive immunization against drugs of abuse requires phagocytosis, the intact Fc portion of the anti-drug Ab, FcγRs, or the neonatal FcR (FcRn). The efficacy of a lead vaccine against oxycodone was not diminished in mice after depletion of macrophages or granulocytes. Anti-oxycodone F(ab')₂ fragments resulted in lower serum levels of F(ab')₂ compared with intact mAbs, and F(ab')₂s were not as effective as the parent mAbs in reducing distribution of oxycodone to the brain. The efficacy of vaccines and mAbs against oxycodone was preserved in either FcγIII or FcγI-IV ablated mice, suggesting that FcγRs are not required for Ab efficacy. Finally, both active and passive immunization against oxycodone in FcRn^-/- mice yielded reduced efficacy compared with wild-type control mice. These data identified a role for FcRn, but not for phagocytosis or Fc-dependent effector functions, in mediating the efficacy of vaccines and mAbs against SUD. This study supports rational design of vaccines and mAbs engineered for maximal neutralization activity and optimal FcRn binding.

The morphine/heroin vaccine decreased the heroin-induced antinociceptive and reinforcing effects in three inbred strains mouse

Clinical trials have indicated that a vaccine must be immunogenic in genetically diverse human populations and that immunogenicity and protective efficacy in animal models are two key indices required for the approval of a new vaccine. Additionally, the immune response (immunogenicity) and immunoprotection are dependent on the mouse strain. Therefore, the objective of the present study was to determine the immune response (immunogenicity) and the protective efficacy (behavioral response) in three inbred mouse strains immunized with the M₆TT vaccine. Female BALB/c, C57Bl/6, and DBA/2 inbred mice were immunized with the M₆-TT vaccine. A solid-phase antibody-capture ELISA was used to monitor antibody titer responses after each booster dose in vaccinated animals. The study used tail-flick testing to evaluate the antinociceptive effects induced by heroin. Additionally, heroin-induced locomotor activity and place preference were evaluated. The M₆-TT vaccine was able to generate a specific antibody titer in the three inbred mouse strains evaluated. The antibodies reduced the antinociceptive effect of different doses of heroin. In addition, they decreased the heroin-induced locomotor activity and place preference. These findings suggest that the M₆-TT vaccine generates a powerful immunogenic response capable of reducing the antinociceptive and reinforcing effects of heroin in different inbred mouse strains, which supports its possible future use in clinical trials in genetically diverse human populations.

A Highly Efficacious Carfentanil Vaccine That Blunts Opioid-Induced Antinociception and Respiratory Depression

The opioid epidemic remains a dire public health crisis with millions of people currently suffering from opioid use disorder (OUD) and tens of thousands dying each year. Synthetic opioids are most responsible for the crisis because of their extreme potency and ease of manufacture. Carfentanil for example has an estimated potency 10,000 times greater than morphine and thus is highly dangerous for human use. Herein, we report two synthetic opioid vaccines that elicited high-affinity antibodies against carfentanil and fentanyl with cross-reactivity to other synthetic opioids in mice and offered protection against opioid-induced respiratory depression, the primary cause of overdose deaths. These vaccines also successfully diminished drug biodistribution to the brain and shielded against opioid analgesic effects. Collectively, these findings provide new insights into the development of immunotherapeutic strategies aimed at opioid abuse and overdose.

Assessing Neutralized Nicotine Distribution Using Mice Vaccinated with the Mucosal Conjugate Nicotine Vaccine

Tobacco smoking continues to be a global epidemic and the leading preventable cause of cancer and cardiovascular disease. Nicotine vaccines have been investigated as an alternative to currently available smoking cessation strategies as a means to increase rates of success and long-term abstinence. Recently, we demonstrated that a mucosal nicotine vaccine was able to induce robust mucosal and systemic antibodies when delivered heterologously using intranasal and intramuscular routes. Herein, we investigated the neutralization ability of the anti-nicotine antibodies using both intranasal and intracardiac nicotine challenges. Combining the extraction of lyophilized organ samples with RP-HPLC methods, we were able to recover between 47% and 56% of the nicotine administered from the blood, brain, heart, and lungs up to 10 min after challenge, suggesting that the interaction of the antibodies with nicotine forms a stable complex independently of the route of vaccination or challenge. Although both challenge routes can be used for assessing systemic antibodies, only the intranasal administration of nicotine, which is more physiologically similar to the inhalation of nicotine, permitted the crucial interaction of nicotine with the mucosal antibodies generated using the heterologous vaccination route. Notably, these results were obtained 6 months after the final vaccination, demonstrating stable mucosal and systemic antibody responses.

Effect of the morphine/heroin vaccine on opioid and non-opioid drug-induced antinociception in mice

Pain is a common symptom in patients with opioid use disorder (OUD), which increases synthetic and illicit synthetic opioid abuse and even fatalities due to opioid overdose. Many FDA-approved drugs are available for the treatment of OUD, however, the use of these medications is limited, mainly due to the development of various side effects. Active vaccination is a new therapeutic approach but the resulting antibodies may compromise the use and efficiency of opioid and non-opioid drugs. In this study, we evaluated whether the antibodies produced by the morphine/heroin vaccine (M-TT) would alter the antinociceptive effects of opioid and non-opioid drugs. Female Balb-c mice were immunized with the M-TT vaccine. A solid-phase antibody-capture ELISA was used for monitoring antibody titer responses after each booster dose in vaccinated animals, followed by tail-flick testing. This study found that the M-TT vaccine did not affect the antinociception induced by different doses of morphine or the ability of non-opioid and synthetic opioid drugs to decrease thermal pain. Moreover, the combination of vaccination and naloxone increased the time-course of morphine antagonism relative to either vaccination or naloxone alone. These results suggest that the antibody titers generated by the M-TT vaccine 1) are capable of reducing morphine-induced antinociception and 2) are selective enough not to alter antinociception induced by non-opioid or synthetic drugs. These characteristics support its potential as a treatment agent for patients with symptoms of pain comorbid to OUD.

Countermeasures for Preventing and Treating Opioid Overdose

The only medication available currently to prevent and treat opioid overdose (naloxone) was approved by the US Food and Drug Administration (FDA) nearly 50 years ago. Because of its pharmacokinetic and pharmacodynamic properties, naloxone has limited utility under some conditions and would not be effective to counteract mass casualties involving large-scale deployment of weaponized synthetic opioids. To address shortcomings of current medical countermeasures for opioid toxicity, a trans-agency scientific meeting was convened by the US National Institute of Allergy and Infectious Diseases/National Institutes of Health (NIAID/NIH) on August 6 and 7, 2019, to explore emerging alternative approaches for treating opioid overdose in the event of weaponization of synthetic opioids. The meeting was initiated by the Chemical Countermeasures Research Program (CCRP), was organized by NIAID, and was a collaboration with the National Institute on Drug Abuse/NIH (NIDA/NIH), the FDA, the Defense Threat Reduction Agency (DTRA), and the Biomedical Advanced Research and Development Authority (BARDA). This paper provides an overview of several presentations at that meeting that discussed emerging new approaches for treating opioid overdose, including the following: (1) intranasal nalmefene, a competitive, reversible opioid receptor antagonist with a longer duration of action than naloxone; (2) methocinnamox, a novel opioid receptor antagonist; (3) covalent naloxone nanoparticles; (4) serotonin (5-HT)_1A receptor agonists; (5) fentanyl-binding cyclodextrin scaffolds; (6) detoxifying biomimetic "nanosponge" decoy receptors; and (7) antibody-based strategies. These approaches could also be applied to treat opioid use disorder.