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

In vitro biophysical and pharmacological profiling predicts in vivo efficacy of anti-carfentanil monoclonal antibodies in mice

Synthetic opioids, including fentanyl and its potent analogs (F/FA) such as carfentanil, are involved in the majority of fatal and non-fatal overdoses in the United States. Despite the availability of the opioid receptor antagonists naloxone and nalmefene to treat overdose, this public health crisis highlights the need for a broader range of treatment options. To support the clinical value of drug-specific monoclonal antibodies (mAbs) as therapeutics for reducing opioid overdose toxicity, the current studies performed in vitro characterization of anti-carfentanil mAbs, and in vivo assessment of their efficacy against carfentanil-induced respiratory depression in mice. To probe the binding interaction between mAbs and carfentanil, this study employed a human mu-opioid receptor (hMOR) calcium mobilization assay and differential scanning fluorimetry. Two of the five mAbs significantly reversed carfentanil-induced respiratory depression in mice. The degree of thermal stabilization of carfentanil-bound mAb correlated with greater efficacy of a given mAb to reverse carfentanil-induced respiratory depression in mice. The reduction of carfentanil-induced hMOR activation stratified mAbs into categories that corresponded, albeit not significantly, to greater in vivo efficacy. These studies indicate that biophysical and pharmacological in vitro analyses can predict the in vivo efficacy of novel mAbs, and support further investigation of mAb-based therapeutics against carfentanil toxicity.

Fentanyl-Antibody Interaction as a Novel Strategy against Opiates and Opioids Abuse

While naloxone remains the antidote for opioid overdoses, more efficient tools are required to effectively combat this growing crisis. Vaccines and antibodies targeting substances of abuse appear to be a novel and promising approach to tackling the fentanyl and opioid epidemic. After an initial in-depth rundown on the pharmacodynamics of the substances involved from a structural and mechanistic standpoint, and a brief overview of pharmacological approaches used in clinical settings for managing overdoses and opioid addiction, this Perspective will be mainly focused on these innovative strategies, based on the development of antibodies binding and sequestering substances of abuse and on their generation in vivo through vaccines. The most promising approaches will be examined, from production techniques to their potential clinical applications, analyzing the structures and mechanisms of antibody-substance interactions and comparing these with receptor binding processes.

Substructure-Specific Antibodies Against Fentanyl Derivatives

Structural variants of the synthetic opioid fentanyl are a major threat to public health. Following an investigation showing that many derivatives are poorly detected by commercial lateral flow and related assays, we created hapten conjugate vaccines using an immunogenic virus-like particle carrier and eight synthetic fentanyl derivatives designed to mimic the structural features of several of the more dangerous analogues. Immunization of mice elicited strong antihapten humoral responses, allowing the screening of hundreds of hapten-specific hybridomas for binding strength and specificity. A panel of 13 monoclonal IgG antibodies were selected, each showing a different pattern of recognition of fentanyl structural variations, and all proving to be highly efficient at capturing parent fentanyl compounds in competition ELISA experiments. These results provide antibody reagents for assay development as well as a demonstration of the power of the immune system to create binding agents capable of both broad and specific recognition of small-molecule targets.

Structure-Based Engineering of Monoclonal Antibodies for Improved Binding to Counteract the Effects of Fentanyl and Carfentanil

The opioid overdose epidemic is a growing and evolving public health crisis fueled by the widespread presence of fentanyl and fentanyl analogues (F/FAs) in both street mixtures and counterfeit pills. To expand current treatment options, drug-targeting monoclonal antibodies (mAbs) offer a viable therapeutic for both pre- and postexposure clinical scenarios. This study reports the isolation, in vitro characterization, and in vivo efficacy of two murine mAb families targeting fentanyl, carfentanil, or both. Because humanization of the mAbs by CDR grafting negatively impacted affinity for both fentanyl and carfentanil, crystal structures of mAbs in complex with fentanyl or carfentanil were analyzed to identify key residues involved in ligand binding in murine versus humanized structures, and site-directed mutagenesis was used to verify their functional importance. The structural analysis identified a framework residue, Tyr36, present in the murine germline sequence of two mAbs, which was critical for binding to fentanyl and carfentanil. These studies emphasize the importance of structural considerations in mAb engineering to optimize mAbs targeting small molecules including opioids and other drugs of public health interest.

Endogenous opiates and behavior: 2023

This paper is the forty-sixth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2023 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists 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 and alcohol abuse (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).

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.

Machine Learning Discrimination and Ultrasensitive Detection of Fentanyl Using Gold Nanoparticle-Decorated Carbon Nanotube-Based Field-Effect Transistor Sensors

The opioid overdose crisis is a global health challenge. Fentanyl, an exceedingly potent synthetic opioid, has emerged as a leading contributor to the surge in opioid-related overdose deaths. The surge in overdose fatalities, particularly due to illicitly manufactured fentanyl and its contamination of street drugs, emphasizes the urgency for drug-testing technologies that can quickly and accurately identify fentanyl from other drugs and quantify trace amounts of fentanyl. In this paper, gold nanoparticle (AuNP)-decorated single-walled carbon nanotube (SWCNT)-based field-effect transistors (FETs) are utilized for machine learning-assisted identification of fentanyl from codeine, hydrocodone, and morphine. The unique sensing performance of fentanyl led to use machine learning approaches for accurate identification of fentanyl. Employing linear discriminant analysis (LDA) with a leave-one-out cross-validation approach, a validation accuracy of 91.2% is achieved. Meanwhile, density functional theory (DFT) calculations reveal the factors that contributed to the enhanced sensitivity of the Au-SWCNT FET sensor toward fentanyl as well as the underlying sensing mechanism. Finally, fentanyl antibodies are introduced to the Au-SWCNT FET sensor as specific receptors, expanding the linear range of the sensor in the lower concentration range, and enabling ultrasensitive detection of fentanyl with a limit of detection at 10.8 fg mL-1.

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.

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.

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.

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.