Development of a sensitive high-throughput enzymatic assay capable of measuring sub-nanomolar inhibitors of SARS-CoV2 Mpro.

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.

Antiviral Drug Discovery for the Treatment of COVID-19 Infections.

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.

Discovery of (R)-(3-fluoropyrrolidin-1-yl)(6-((5-(trifluoromethyl)pyridin-2-yl)oxy)quinolin-2-yl)methanone (ABBV-318) and analogs as small molecule Na1.7/ Nav1.8 blockers for the treatment of pain.

The voltage-gated sodium channel Na1.7 is an attractive target for the treatment of pain based on the high level of target validation with genetic evidence linking Na1.7 to pain in humans.

Implications of the Conformationally Flexible, Macrocyclic Structure of the First-Generation, Direct-Acting Anti-Viral Paritaprevir on Its Solid Form Complexity and Chameleonic Behavior.

Direct-acting antiviral regimens have transformed therapeutic management of hepatitis C across all prevalent genotypes. Most of the chemical matter in these regimens comprises molecules well outside the traditional drug development chemical space and presents significant challenges. Herein, the implications of high conformational flexibility and the presence of a 15-membered macrocyclic ring in paritaprevir are studied through a combination of advanced computational and experimental methods with focus on molecular chameleonicity and crystal form complexity.

Desymmetrization of pibrentasvir for efficient prodrug synthesis.

A novel and practical desymmetrization tactic is described to access a new class of pibrentasvir prodrugs. The homotopic benzimidazoles of pibrentasvir (PIB) are differentiated a one-pot di-Boc/mono-de-Boc selective -Boc protection and formaldehyde adduct formation sequence, both enabled by crystallization-induced selectivity. The first step represents the only known application of the Horeau principle of statistical amplification for -symmetric polyheterocycle regioselective functionalization.

Prodrug Strategies to Improve the Solubility of the HCV NS5A Inhibitor Pibrentasvir (ABT-530).

A research program to discover solubilizing prodrugs of the HCV NS5A inhibitor pibrentasvir (PIB) identified phosphomethyl analog and trimethyl-lock (TML) prodrug . The prodrug moiety is attached to a benzimidazole nitrogen atom via an oxymethyl linkage to allow for rapid and complete release of the drug for absorption following phosphate removal by intestinal alkaline phosphatase. These prodrugs have good hydrolytic stability properties and improved solubility compared to PIB, both in aqueous buffer (pH 7) and FESSIF (pH 5).

Discovery of 2-aminoisobutyric acid ethyl ester (AIBEE) phosphoramidate prodrugs for delivering nucleoside HCV NS5B polymerase inhibitors.

Our HCV research program investigated novel 2'-dihalogenated nucleoside HCV polymerase inhibitors and identified compound 1, a 5'-phosphoramidate prodrug of 2'-deoxy-2'-α-bromo-β-chloro uridine. Although 1 had a favorable in vitro activity profile in HCV replicons, oral dosing in dog resulted in low levels of the active 5'-triphosphate (TP) in liver. Metabolism studies using human hepatocytes provided a simple assay for screening alternative phosphoramidate prodrug analogs.

Synthesis and evaluation of 2'-dihalo ribonucleotide prodrugs with activity against hepatitis C virus.

Hepatitis C virus (HCV) nucleoside inhibitors have been a key focus of nearly 2 decades of HCV drug research due to a high barrier to drug resistance and pan-genotypic activity profile provided by molecules in this drug class. Our investigations focused on several potent 2'-halogenated uridine-based HCV polymerase inhibitors, resulting in the discovery of novel 2'-deoxy-2'-dihalo-uridine analogs that are potent inhibitors in replicon assays for all genotypes. Further studies to improve in vivo performance of these nucleoside inhibitors identified aminoisobutyric acid ethyl ester (AIBEE) phosphoramidate prodrugs 18a and 18c, which provide high levels of the active triphosphate in dog liver.

Beyond the Rule of 5: Lessons Learned from AbbVie's Drugs and Compound Collection.

Recently, there has been an increasing focus on the pursuit of targets considered to be less druggable that offer potential for development of promising new therapeutic agents for the treatment of diseases with large unmet medical need, particularly in the areas of oncology and virology. However, conducting drug discovery campaigns in "beyond rule of 5" (bRo5) chemical space presents a significant drug design and development challenge to medicinal chemists to achieve acceptable oral pharmacokinetics. Retrospective analysis of past successes and failures in drug discovery bRo5 may shed light on the key principles that contribute to the oral bioavailability of successful bRo5 compounds and improve the efficiency of drug design for future projects.

Substituted Indazoles as Nav1.7 Blockers for the Treatment of Pain.

The genetic validation for the role of the Nav1.7 voltage-gated ion channel in pain signaling pathways makes it an appealing target for the potential development of new pain drugs. The utility of nonselective Nav blockers is often limited due to adverse cardiovascular and CNS side effects.

Discovery of ABT-267, a pan-genotypic inhibitor of HCV NS5A.

We describe here N-phenylpyrrolidine-based inhibitors of HCV NS5A with excellent potency, metabolic stability, and pharmacokinetics. Compounds with 2S,5S stereochemistry at the pyrrolidine ring provided improved genotype 1 (GT1) potency compared to the 2R,5R analogues. Furthermore, the attachment of substituents at the 4-position of the central N-phenyl group resulted in compounds with improved potency.

Aryl uracil inhibitors of hepatitis C virus NS5B polymerase: synthesis and characterization of analogs with a fused 5,6-bicyclic ring motif.

The synthesis and structure-activity relationships of a novel aryl uracil series which contains a fused 5,6-bicyclic ring unit for HCV NS5B inhibition is described. Several analogs display replicon cell culture potencies in the low nanomolar range along with excellent rat pharmacokinetic values.

Discovery of pyrido[2,3-d]pyrimidine-based inhibitors of HCV NS5A.

Efforts to improve the genotype 1a potency and pharmacokinetics of earlier naphthyridine-based HCV NS5A inhibitors resulted in the discovery of a novel series of pyrido[2,3-d]pyrimidine compounds, which displayed potent inhibition of HCV genotypes 1a and 1b in the replicon assay. SAR in this system revealed that the introduction of amides bearing an additional 'E' ring provided compounds with improved potency and pharmacokinetics. Introduction of a chiral center on the amide portion resulted in the observation of a stereochemical dependence for replicon potency and provided a site for the attachment of functional groups useful for improving the solubility of the series.

P1-substituted symmetry-based human immunodeficiency virus protease inhibitors with potent antiviral activity against drug-resistant viruses.

Because there is currently no cure for HIV infection, patients must remain on long-term drug therapy, leading to concerns over potential drug side effects and the emergence of drug resistance. For this reason, new and safe antiretroviral agents with improved potency against drug-resistant strains of HIV are needed. A series of HIV protease inhibitors (PIs) with potent activity against both wild-type (WT) virus and drug-resistant strains of HIV was designed and synthesized.

KCNQ2/3 openers show differential selectivity and site of action across multiple KCNQ channels.

KCNQ2/3 voltage-gated potassium channels conduct low-threshold, slowly activating and non-inactivating currents to repolarize the neuronal resting membrane potential. The channels negatively regulate neuronal excitability and KCNQ2/3 openers are efficacious in hyperexcited states such as epilepsy and pain. We developed and utilized thallium influx assays to profile novel KCNQ2/3 channel openers with respect to selectivity across KCNQ subtypes and on requirement for tryptophan 236 of KCNQ2, a critical residue for activity of the KCNQ opener retigabine.

Identification of proteasome gene regulation in a rat model for HIV protease inhibitor-induced hyperlipidemia.

Patients treated with highly active antiretroviral therapy may develop metabolic side effects such as hyperlipidemia, insulin resistance, lipoatrophy and lactic acidosis. The pathophysiology of these metabolic abnormalities is unknown, although some, e.g.

Water-soluble prodrugs of the human immunodeficiency virus protease inhibitors lopinavir and ritonavir.

We studied the synthesis, cleavage rates, and oral administration of prodrugs of the HIV protease inhibitors (PIs) lopinavir and ritonavir. Phosphate esters attached directly to the central hydroxyl groups of these PIs did not demonstrate enzyme-mediated cleavage in vitro and did not provide measurable plasma levels of the parent drugs in vivo. However, oxymethylphosphate (OMP) and oxyethylphosphate (OEP) prodrugs provided improved rates of cleavage, high levels of aqueous solubility, and high plasma levels of the parent drugs when dosed orally in rats and dogs.

2-Pyridyl P1'-substituted symmetry-based human immunodeficiency virus protease inhibitors (A-792611 and A-790742) with potential for convenient dosing and reduced side effects.

A series of symmetry-based HIV protease inhibitors was designed and synthesized. Modification of the core regiochemistry and stereochemistry significantly affected the potency, metabolic stability, and oral bioavailability of the inhibitors, as did the variation of a pendent arylmethyl P3 group. Optimization led to the selection of two compounds, 10c (A-790742) and 9d (A-792611), for advancement to preclinical studies.

Characterization of a novel human immunodeficiency virus type 1 protease inhibitor, A-790742.

A-790742 is a potent human immunodeficiency virus type 1 (HIV-1) protease inhibitor, with 50% effective concentrations ranging from 2 to 7 nM against wild-type HIV-1. The activity of this compound is lowered by approximately sevenfold in the presence of 50% human serum. A-790742 maintained potent antiviral activity against lopinavir-resistant variants generated in vitro as well as against a panel of molecular clones containing proteases derived from HIV-1 patient isolates with multiple protease mutations.

Discovery of imidazolidine-2,4-dione-linked HIV protease inhibitors with activity against lopinavir-resistant mutant HIV.

A new series of HIV protease inhibitors has been designed and synthesized based on the combination of the (R)-(hydroxyethylamino)sulfonamide isostere and the cyclic urea component of lopinavir. The series was optimized by replacing the 6-membered cyclic urea linker with an imidazolidine-2,4-dione which readily underwent N-alkylation to incorporate various methylene-linked heterocycle groups that bind favorably in site 3 of HIV protease. Significant improvements compared to lopinavir were seen in cell culture activity versus wild-type virus (pNL4-3) and the lopinavir-resistant mutant virus A17 (generated by in vitro serial passage of HIV-1 (pNL4-3) in MT-4 cells).

Practical preclinical model for assessing the potential for unconjugated hyperbilirubinemia produced by human immunodeficiency virus protease inhibitors.

A practical preclinical model for the hyperbilirubinemia produced by human immunodeficiency virus protease inhibitors has been developed. Indinavir and atazanavir produced significant hyperbilirubinemia, whereas amprenavir, the negative control, was indistinguishable from the ritonavir booster dose. This model was used to disqualify an exploratory protease inhibitor from development.

Peptidomimetic inhibitors of HIV protease.

There are currently (July, 2002) six protease inhibitors approved for the treatment of HIV infection, each of which can be classified as peptidomimetic in structure. These agents, when used in combination with other antiretroviral agents, produce a sustained decrease in viral load, often to levels below the limits of quantifiable detection, and a significant reconstitution of the immune system. Therapeutic regimens containing one or more HIV protease inhibitors thus provide a highly effective method for disease management.

Enantioselective synthesis of antiinfluenza compound A-315675.

Drug discovery efforts at Abbott Laboratories have led to the identification of influenza neuraminidase inhibitor A-315675 (1) as a candidate for development as an antiinfluenza drug. A convergent, stereoselective synthesis of this highly functionalized pyrrolidine is reported that utilizes pyrrolinone 2 as the key intermediate. The C5, C6 stereochemistry was established through a diastereoselective condensation of chiral imine compound 3 with silyloxypyrrole 4 to give pyrrolinone 2.