The RNA-dependent RNA polymerase (RdRp) of coronaviruses, comprising highly conserved non-structural proteins, is a critical player in the viral lifecycle and represents a promising target for developing pan-coronavirus antivirals. Despite substantial efforts to identify RdRp inhibitors through drug repurposing and novel compound discovery campaigns, potent in vitro non-nucleoside inhibitors remain elusive. In this study, we detail the development of a robust PicoGreen assay, which facilitated the screening of AbbVie's extensive chemical library, encompassing over 900,000 small molecules, against the SARS-CoV-2 RdRp. Through a combination of biochemical and biophysical assays, we identified two potent non-nucleoside compounds with activity against our PicoGreen beta-coronavirus panel. Mechanism of action investigations revealed these compounds bind exclusively to the nsp12-8 complex, unveiling a potentially unique inhibitory mechanism. These compounds serve as valuable starting points for structure-activity relationship (SAR) explorations and potential therapeutic leads.

This article highlights synergistic real-time interactions between academic and industrial groups that drove innovations in both medicinal chemistry and catalysis. An AbbVie medicinal chemistry team had identified a promising series of trisubstituted cyclopropanes during a drug discovery campaign focused on developing CFTR C2 correctors for the treatment of cystic fibrosis. However, this unique chemical space was challenging to efficiently explore due to known limitations with previously established cyclopropanation reaction conditions. By expanding upon an existing precompetitive relationship with the Davies group at Emory University who are pioneers in development of methods for highly diastereo- and enantioselective cyclopropanations, a joint industry-academia team collaborated to discover a unique catalyst-additive system for this challenging transformation that had a broad and pharmaceutically relevant substrate scope. The optimized method was immediately applied to accelerate medicinal chemistry progress in the series, leading to the identification of novel CFTR corrector ABBV-602. Finally, a flow procedure was developed for generating the carbene precursor which enabled the reaction to be carried out on kilogram scale.

The SARS-CoV-2 main protease (Mpro) is essential for viral replication because it is responsible for the processing of most of the non-structural proteins encoded by the virus. Inhibition of Mpro prevents viral replication and therefore constitutes an attractive antiviral strategy. We set out to develop a high-throughput Mpro enzymatic activity assay using fluorescently labeled peptide substrates. A library of fluorogenic substrates of various lengths, sequences and dye/quencher positions was prepared and tested against full length SARS-CoV-2 Mpro enzyme for optimal activity. The addition of buffers containing strongly hydrated kosmotropic anion salts, such as citrate, from the Hofmeister series significantly boosted the enzyme activity and enhanced the assay detection limit, enabling the ranking of sub-nanomolar inhibitors without relying on the low-throughput Morrison equation method. By comparing cooperativity in citrate or non-citrate buffer while titrating the Mpro enzyme concentration, we found full positive cooperativity of Mpro with citrate buffer at less than one nanomolar (nM), but at a much higher enzyme concentration (∼320 nM) with non-citrate buffer. In addition, using a tight binding Mpro inhibitor, we confirmed there was only one active catalytical site in each Mpro monomer. Since cooperativity requires at least two binding sites, we hypothesized that citrate facilitates dimerization of Mpro at sub-nanomolar concentration as one of the mechanisms enhances Mpro catalytic efficiency. This assay has been used in high-throughput screening and structure activity relationship (SAR) studies to support medicinal chemistry efforts. IC50 values determined in this assay correlates well with EC50 values generated by a SARS-CoV-2 antiviral assay after adjusted for cell penetration.

Tyrosine kinase 2 (TYK2) is a nonreceptor tyrosine kinase that belongs to the JAK family also comprising JAK1, JAK2, and JAK3. TYK2 is an attractive target for various autoimmune diseases as it regulates signal transduction downstream of IL-23 and IL-12 receptors. Selective TYK2 inhibition offers a differentiated clinical profile compared to currently approved JAK inhibitors. However, selectivity for TYK2 versus other JAK family members has been difficult to achieve with small molecules that inhibit the catalytically active kinase domain. Successful targeting of the TYK2 pseudokinase domain as a strategy to achieve isoform selectivity was recently exemplified with deucravacitinib. Described herein is the optimization of selective TYK2 inhibitors targeting the pseudokinase domain, resulting in the discovery of the clinical candidate ABBV-712 (21).

The coronavirus disease 2019 (COVID-19) pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a recently emerged human coronavirus. COVID-19 vaccines have proven to be successful in protecting the vaccinated from infection, reducing the severity of disease, and deterring the transmission of infection. However, COVID-19 vaccination faces many challenges, such as the decline in vaccine-induced immunity over time, and the decrease in potency against some SARS-CoV-2 variants including the recently emerged Omicron variant, resulting in breakthrough infections. The challenges that COVID-19 vaccination is facing highlight the importance of the discovery of antivirals to serve as another means to tackle the pandemic. To date, neutralizing antibodies that block viral entry by targeting the viral spike protein make up the largest class of antivirals that has received US FDA emergency use authorization (EUA) for COVID-19 treatment. In addition to the spike protein, other key targets for the discovery of direct-acting antivirals include viral enzymes that are essential for SARS-CoV-2 replication, such as RNA-dependent RNA polymerase and proteases, as judged by US FDA approval for remdesivir, and EUA for Paxlovid (nirmatrelvir + ritonavir) for treating COVID-19 infections. This review presents an overview of the current status and future direction of antiviral drug discovery for treating SARS-CoV-2 infections, covering important antiviral targets such as the viral spike protein, non-structural protein (nsp) 3 papain-like protease, nsp5 main protease, and the nsp12/nsp7/nsp8 RNA-dependent RNA polymerase complex.

Cystic fibrosis (CF) is an autosomal recessive disease resulting from mutations on both copies of the CFTR gene. Phenylalanine deletion at position 508 of the CFTR protein (F508del-CFTR) is the most frequent mutation in CF patients. Currently, the most effective treatments of CF use a dual or triple combination of CFTR correctors and potentiators. In triple therapy, two correctors (C1 and C2) and a potentiator are employed. Herein, we describe the identification and exploration of the SAR of a series of 4-aminopyrrolidine-2-carboxylic acid C2 correctors of CFTR to be used in conjunction with our existing C1 corrector series for the treatment of CF.

Cystic fibrosis (CF) is a genetic disorder that affects multiple tissues and organs. CF is caused by mutations in the gene, resulting in insufficient or impaired cystic fibrosis transmembrane conductance regulator (CFTR) protein. The deletion of phenylalanine at position 508 of the protein (F508del-CFTR) is the most common mutation observed in CF patients. The most effective treatments of these patients employ two CFTR modulator classes, correctors and potentiators. CFTR correctors increase protein levels at the cell surface; CFTR potentiators enable the functional opening of CFTR channels at the cell surface. Triple-combination therapies utilize two distinct corrector molecules (C1 and C2) to further improve the overall efficacy. We identified the need to develop a C2 corrector series that had the potential to be used in conjunction with our existing C1 corrector series and provide robust clinical efficacy for CF patients. The identification of a pyrrolidine series of CFTR C2 correctors and the structure-activity relationship of this series is described. This work resulted in the discovery and selection of (2,3,4,5)-3-(-butyl)-4-((2-methoxy-5-(trifluoromethyl)pyridin-3-yl)methoxy)-1-(()-tetrahydro-2-pyran-2-carbonyl)-5-(-tolyl)pyrrolidine-2-carboxylic acid (ABBV/GLPG-3221), which was advanced to clinical trials.

Mass balance, metabolism, and excretion of ABT-126, an α7 neuronal acetylcholine receptor agonist, were characterized in healthy male subjects (n = 4) after a single 100-mg (100 μCi) oral dose. The total recovery of the administered radioactivity was 94.0% (±2.09%), with 81.5% (±10.2%) in urine and 12.4% (±9.3%) in feces. Metabolite profiling indicated that ABT-126 had been extensively metabolized, with 6.6% of the dose remaining as unchanged parent drug in urine. Parent drug accounted for 12.2% of the administered radioactivity in feces. The primary metabolic transformations of ABT-126 involved aza-adamantane N-oxidation (M1, 50.3% in urine) and aza-adamantane N-glucuronidation (M11, 19.9% in urine). M1 and M11 were also major circulating metabolites, accounting for 32.6% and 36.6% of the drug-related material in plasma, respectively. These results demonstrated that ABT-126 is eliminated primarily by hepatic metabolism, followed by urinary excretion. Enzymatic studies suggested that M1 formation is mediated primarily by human liver flavin-containing monooxygenase (FMO)3 and, to a lesser extent, by human kidney FMO1; M11 is generated mainly by human uridine 5′-diphospho-glucuronosyltransferase (UGT) 1A4, whereas UGT 2B10 also contributes to ABT-126 glucuronidation. Species-dependent formation of M11 was observed in hepatocytes; M11 was formed in human and monkey hepatocytes, but not in rat and dog hepatocytes, suggesting that monkeys constitute an appropriate model for predicting the fate of compounds undergoing significant N-glucuronidation. M1 and M11 are not expected to have clinically relevant on- or off-target pharmacologic activities. In summary, this study characterized ABT-126 metabolites in the circulation and excreta and the primary elimination pathways of ABT-126 in humans.

Enhancement of α7 nicotinic receptor (nAChR) activity is considered as an attractive approach for ameliorating cognitive deficits associated with schizophrenia and Alzheimer's disease. Here, we describe the preclinical profile of a novel α7 nAChR agonist, ABT-126. In vitro pharmacology was characterized by radioligand binding, electrophysiology, and Ca2 + imaging methodologies as previously described 1. In vivo studies involved immunohistochemical and behavioral approaches as described 2,3. ABT-126 displayed high affinity to α7 nAChRs (human or rat cortex), but substantially lower affinity at other nAChR subtypes. Functionally, ABT-126 evoked human and rat α7 nAChR current responses in Xenopus oocytes, and enhanced synaptic activity and current responses in rat hippocampal slice preparations. In vivo administration of ABT-126 in rodents modulated biochemical (ERK1/2 and CREB phosphorylation) and neurochemical (ACh release) effects in hippocampal and cortical regions at behaviorally effective dose range. In vivo, ABT-126 was found to be effective in rodent/primate models that capture domains of working memory, memory consolidation and recall, preattention and short-term memory. Repeated daily dosing or steady state exposure of ABT-126 did not result in attenuation of efficacy in vivo. Finally, ABT-126 exhibited acceptable preclinical safety/tolerability profiles. Our studies demonstrate that ABT-126 is a selective α7 nAChR agonist that modulates cortical and hippocampal signaling mechanisms associated with cognitive function. Moreover, ABT-126 exhibited broad-spectrum precognitive efficacy in preclinical models across domains implicated in schizophrenia and Alzheimer's disease. Based on these results, ABT-126 was advanced into clinical development where positive signals of cognitive efficacy were observed [accompanying abstract]. 1 Malysz et al., J. Pharmacol. Exp. Ther., 334: 863, 2010; 2 Bitner et al., J. Neurosci., 27: 10578, 2007; 3 Bitner et al., J. Pharmacol Exp Ther., 334:875, 2010.

Introduction: alpha 7-nicotinic acetylcholine receptor (alpha 7-nAChR) is one of the major neuronal nAChR subtypes. alpha 7-nAChR is involved in variety of neuronal processes and disorders including schizophrenia and Alzheimer's disease. A number of alpha 7-nAChR PET radioligands have been developed, but a quality radiotracer remains to be discovered.Methods: High binding affinity alpha 7-nAChR ligands A-833834 and A-752274 were radiolabeled with C-11. Baseline and blockadp biodistribution studies in the mouse brain of [C-11]A-833834 (5-(6-(5-[C-11] methylhexahydropyrrolo[3,4-c]pyrrol-2(1H)-yl)pyridazin-3-yl)-1H-indole) and [C-11]A-752274 (2-(6-[C-11] methyl-3,6-diazabicyclo[3,2,0]heptan-3-yl)-7-(6-methyl-3,6-diazabicyclo[3.2.0]heptan-3-yl)-9H-fluoren-9-one) were performed. [C-11]A-752274 was evaluated in a baseline baboon PET study.Results: [C-11]A-833834 and [C-11]A-752274 were synthesized by radiomethylation of corresponding desmethyl precursors. The radioligands were prepared with radiochemical yield of 12%-32%, high specific radioactivity (330-403 GB1/mu mol) and radiochemical purity>95%. Dissection studies with [C-11]A-833834 demonstrated low specific alpha 7-nAChR binding in the mouse brain. [C-11]A-752274 specifically (similar to 50%) labeled alpha 7-nAChR in the mouse thalamus. However, [(11)CA-752274 exhibited low brain uptake in baboon (%SUV<100).Conclusion: Two novel alpha 7-nAChR ligands radioligands were synthesized and studied in animals. Specific binding of [C-11]A-833834 in the mouse brain is low due to the insufficient binding affinity of the radioligand. The very high binding affinity [C-11]A-752274 exhibited good specific binding in the alpha 7-nAChR-rich mouse brain regions. The low uptake of [C-11]A-752274 in the baboon brain is due to its high hydrophilicity, rapid metabolism or other properties. Future development of alpha 7-nAChR PET radioligands will be based on compounds with high binding affinities and good blood-brain barrier permeability. (C) 2013 Elsevier Inc. All rights reserved.

A novel series of N-type calcium channel inhibitors have been discovered. Optimization of potency and HT-ADME properties provides 4-aminocyclopentapyrrolidines with analgesic efficacy after oral dosing.