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

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.

Vaccines to Treat Substance Use Disorders: Current Status and Future Directions

Addiction, particularly in relation to psychostimulants and opioids, persists as a global health crisis with profound social and economic ramifications. Traditional interventions, including medications and behavioral therapies, often encounter limited success due to the chronic and relapsing nature of addictive disorders. Consequently, there is significant interest in the development of innovative therapeutics to counteract the effects of abused substances. In recent years, vaccines have emerged as a novel and promising strategy to tackle addiction. Anti-drug vaccines are designed to stimulate the immune system to produce antibodies that bind to addictive compounds, such as nicotine, cocaine, morphine, methamphetamine, and heroin. These antibodies effectively neutralize the target molecules, preventing them from reaching the brain and eliciting their rewarding effects. By obstructing the rewarding sensations associated with substance use, vaccines aim to reduce cravings and the motivation to engage in drug use. Although anti-drug vaccines hold significant potential, challenges remain in their development and implementation. The reversibility of vaccination and the potential for combining vaccines with other addiction treatments offer promise for improving addiction outcomes. This review provides an overview of anti-drug vaccines, their mechanisms of action, and their potential impact on treatment for substance use disorders. Furthermore, this review summarizes recent advancements in vaccine development for each specific drug, offering insights for the development of more effective and personalized treatments capable of addressing the distinct challenges posed by various abused substances.

An Engineered Human-Antibody Fragment with Fentanyl Pan-Specificity That Reverses Carfentanil-Induced Respiratory Depression

The opioid overdose crisis primarily driven by potent synthetic opioids resulted in more than 500,000 deaths in the US over the last 20 years. Though naloxone, a short-acting medication, remains the primary treatment option for temporarily reversing opioid overdose effects, alternative countermeasures are needed. Monoclonal antibodies present a versatile therapeutic opportunity that can be tailored to synthetic opioids and help prevent post-treatment renarcotization. The ultrapotent analog carfentanil is especially concerning due to its unique pharmacological properties. With this in mind, we generated a fully human antibody through a drug-specific B cell sorting strategy with a combination of carfentanil and fentanyl probes. The resulting pan-specific antibody was further optimized through scFv phage display, producing C10-S66K. This monoclonal antibody displays high affinity to carfentanil, fentanyl, and other analogs and reversed carfentanil-induced respiratory depression. Additionally, X-ray crystal structures with carfentanil and fentanyl bound provided structural insight into key drug:antibody interactions.

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.

An Engineered Human-Antibody Fragment with Fentanyl Pan-Specificity that Reverses Carfentanil-Induced Respiratory Depression

The opioid overdose crisis primarily driven by potent synthetic opioids resulted in more than 500,000 deaths in the US over the last 20 years. Though naloxone, a short acting medication, remains the primary treatment option for temporarily reversing opioid overdose effects, alternative countermeasures are needed. Monoclonal antibodies present a versatile therapeutic opportunity that can be tailored for synthetic opioids and that can help prevent post-treatment renarcotization. The ultrapotent analog carfentanil, is especially concerning due to its unique pharmacological properties. With this in mind, we generated a fully human antibody through a drug-specific B cell sorting strategy with a combination of carfentanil and fentanyl probes. The resulting pan-specific antibody was further optimized through scFv phage display. This antibody, C10-S66K, displays high affinity to carfentanil, fentanyl, and other analogs, and reversed carfentanil-induced respiratory depression. Additionally, x-ray crystal structures with carfentanil and fentanyl bound provided structural insight into key drug:antibody interactions.

Catalytic Antibody Blunts Carfentanil-Induced Respiratory Depression

Carfentanil, the most potent of the fentanyl analogues, is at the forefront of synthetic opioid-related deaths, second to fentanyl. Moreover, the administration of the opioid receptor antagonist naloxone has proven inadequate for an increasing number of opioid-related conditions, often requiring higher/additional doses to be effective, as such interest in alternative strategies to combat more potent synthetic opioids has intensified. Increasing drug metabolism would be one strategy to detoxify carfentanil; however, carfentanil's major metabolic pathways involve N-dealkylation or monohydroxylation, which do not lend themselves readily to exogenous enzyme addition. Herein, we report, to our knowledge, the first demonstration that carfentanil's methyl ester when hydrolyzed to its acid was found to be 40,000 times less potent than carfentanil in activating the μ-opioid receptor. Physiological consequences of carfentanil and its acid were also examined through plethysmography, and carfentanil's acid was found to be incapable of inducing respiratory depression. Based upon this information, a hapten was chemically synthesized and immunized, allowing the generation of antibodies that were screened for carfentanil ester hydrolysis. From the screening campaign, three antibodies were found to accelerate the hydrolysis of carfentanil's methyl ester. From this series of catalytic antibodies, the most active underwent extensive kinetic analysis, allowing us to postulate its mechanism of hydrolysis against this synthetic opioid. In the context of potential clinical applications, the antibody, when passively administered, was able to reduce respiratory depression induced by carfentanil. The data presented supports further development of antibody catalysis as a biologic strategy to complement carfentanil overdose reversal.

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.

Endogenous opiates and behavior: 2021

This paper is the forty-fourth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2021 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonizts and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

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.

Anthracene-Walled Acyclic CB[n] Receptors: in vitro and in vivo Binding Properties toward Drugs of Abuse

We report studies of the interaction of six acyclic CB[n]-type receptors toward a panel of drugs of abuse by a combination of isothermal titration calorimetry and 1 H NMR spectroscopy. Anthracene walled acyclic CB[n] host (M3) displays highest binding affinity toward methamphetamine (Kd =15 nM) and fentanyl (Kd =4 nM). Host M3 is well tolerated by Hep G2 and HEK 293 cells up to 100 μM according to MTS metabolic and adenylate kinase release assays. An in vivo maximum tolerated dose study with Swiss Webster mice showed no adverse effects at the highest dose studied (44.7 mg kg-1 ). Host M3 is not mutagenic based on the Ames fluctuation test and does not inhibit the hERG ion channel. In vivo efficacy studies showed that pretreatment of mice with M3 significantly reduces the hyperlocomotion after treatment with methamphetamine, but M3 does not function similarly when administered 30 seconds after methamphetamine.

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.

Efficacy and Selectivity of Monovalent and Bivalent Vaccination Strategies to Protect against Exposure to Carfentanil, Fentanyl, and Their Mixtures in Rats

Drug-related fatal overdoses have significantly increased in the past decade due to the widespread availability of illicit fentanyl and other potent synthetic opioids such as carfentanil. Deliberate or accidental consumption or exposure to carfentanil, fentanyl, and their mixture induces respiratory depression and bradycardia that can be difficult to reverse with the opioid receptor antagonist naloxone. Vaccines offer a promising strategy to reduce the incidence of fatalities associated with fentanyl-related substances, as well as treatment for opioid use disorder (OUD). This study reports monovalent and bivalent vaccination strategies that elicit polyclonal antibody responses effective in protecting against the pharmacological actions of carfentanil, fentanyl, or carfentanil/fentanyl mixtures. Rats were prophylactically immunized with individual conjugate vaccines containing either carfentanil- or fentanyl-based haptens, or their combination in bivalent vaccine formulations, and then challenged with carfentanil, fentanyl, or their mixture. First, these studies identified a lead vaccine protective against carfentanil-induced antinociception, respiratory depression, and bradycardia. Then, efficacy against both carfentanil and fentanyl was achieved through bivalent vaccination strategies that combined lead anti-carfentanil and anti-fentanyl vaccines via either heterologous prime/boost or co-administration immunization regimens. These preclinical data support the development of vaccines as a viable strategy to prevent toxicity from exposure to excessive doses of carfentanil, fentanyl, or their mixtures.

A Vaccine against Benzimidazole-Derived New Psychoactive Substances That Are More Potent Than Fentanyl

New psychoactive substance (NPS) opioids have proliferated within the international drug market. While synthetic opioids are traditionally composed of fentanyl analogues, benzimidazole-derived isotonitazene and its derivatives are the current NPS opioids of concern. Hence, in this study, we implement immunopharmacotherapy wherein antibodies are produced with high titers and nanomolar affinity to multiple benzimidazole-derived NPS opioids (BNO). Notably, these antibodies blunt psychoactive and physiological repercussions from BNO exposure, which was observed through antinociception, whole-body plethysmography, and blood-brain biodistribution studies. Moreover, we detail previously unreported pharmacokinetics of these drugs, which explains the struggle of traditional pharmaceutical opioid antagonists against BNO substances. These findings provide further insight into the in vivo effects of BNO drugs and the development of effective broad-spectrum therapeutics against NPS opioids.

Development of effective therapeutics for polysubstance use disorders

Traditional pharmacotherapies for substance use disorders have focused on mono-substance abuse. However, recent epidemiological studies have found polysubstance use disorders (PUD) are becoming more prevalent and the abuse of adulterated drugs has led to increasing unintentional overdose deaths. Unfortunately, there are no approved pharmacological agents for PUD. Hence, a therapeutic model of interest to address this growing epidemic is immunopharmacotherapy, where individuals are inoculated with conjugate vaccines formulated with haptens that mimic the drug of abuse. These conjugate vaccines have demonstrated significant therapeutic potential against mono-substance abuse, thus recent studies have applied this model to address PUD. This review presents immunopharmacotherapeutic advancements against polysubstance abuse and discusses necessary developments for conjugate vaccines in order to effectively treat this unaddressed epidemic.

Bivalent Conjugate Vaccine Induces Dual Immunogenic Response That Attenuates Heroin and Fentanyl Effects in Mice

Opioid use disorders and fatal overdose due to consumption of fentanyl-laced heroin remain a major public health menace in the United States. Vaccination may serve as a promising potential remedy to combat accidental overdose and to mitigate the abuse potential of opioids. We previously reported the heroin and fentanyl monovalent vaccines carrying, respectively, a heroin hapten, 6-AmHap, and a fentanyl hapten, para-AmFenHap, conjugated to tetanus toxoid (TT). Herein, we describe the mixing of these antigens to formulate a bivalent vaccine adjuvanted with liposomes containing monophosphoryl lipid A (MPLA) adsorbed on aluminum hydroxide. Immunization of mice with the bivalent vaccine resulted in IgG titers of >105 against both haptens. The polyclonal sera bound heroin, 6-acetylmorphine, morphine, and fentanyl with dissociation constants (Kd) of 0.25 to 0.50 nM. Mice were protected from the anti-nociceptive effects of heroin, fentanyl, and heroin +9% (w/w) fentanyl. No cross-reactivity to methadone and buprenorphine was observed in vivo. Naloxone remained efficacious in immunized mice. These results highlighted the potential of combining TT-6-AmHap and TT-para-AmFenHap to yield an efficacious bivalent vaccine that could ablate heroin and fentanyl effects. This vaccine warrants further testing to establish its potential translatability to humans.