Discovery and Optimization of Indolyl-Containing 4-Hydroxy-2-Pyridone Type II DNA Topoisomerase Inhibitors Active against Multidrug Resistant Gram-negative Bacteria

There exists an urgent medical need to identify new chemical entities (NCEs) targeting multidrug resistant (MDR) bacterial infections, particularly those caused by Gram-negative pathogens. 4-Hydroxy-2-pyridones represent a novel class of nonfluoroquinolone inhibitors of bacterial type II topoisomerases active against MDR Gram-negative bacteria. Herein, we report on the discovery and structure-activity relationships of a series of fused indolyl-containing 4-hydroxy-2-pyridones with improved in vitro antibacterial activity against fluoroquinolone resistant strains. Compounds 6o and 6v are representative of this class, targeting both bacterial DNA gyrase and topoisomerase IV (Topo IV). In an abbreviated susceptibility screen, compounds 6o and 6v showed improved MIC₉₀ values against Escherichia coli (0.5-1 μg/mL) and Acinetobacter baumannii (8-16 μg/mL) compared to the precursor compounds. In a murine septicemia model, both compounds showed complete protection in mice infected with a lethal dose of E. coli.

4-Hydroxy-2-pyridones: Discovery and evaluation of a novel class of antibacterial agents targeting DNA synthesis

The continued emergence of bacteria resistant to current standard of care antibiotics presents a rapidly growing threat to public health. New chemical entities (NCEs) to treat these serious infections are desperately needed. Herein we report the discovery, synthesis, SAR and in vivo efficacy of a novel series of 4-hydroxy-2-pyridones exhibiting activity against Gram-negative pathogens. Compound 1c, derived from the N-debenzylation of 1b, preferentially inhibits bacterial DNA synthesis as determined by standard macromolecular synthesis assays. The structural features of the 4-hydroxy-2-pyridone scaffold required for antibacterial activity were explored and compound 6q, identified through further optimization of the series, had an MIC₉₀ value of 8 μg/mL against a panel of highly resistant strains of E. coli. In a murine septicemia model, compound 6q exhibited a PD₅₀ of 8 mg/kg in mice infected with a lethal dose of E. coli. This novel series of 4-hydroxy-2-pyridones serves as an excellent starting point for the identification of NCEs treating Gram-negative infections.

Identification of benzazole compounds that induce HIV-1 transcription

Despite advances in antiretroviral therapy, HIV-1 infection remains incurable in patients and continues to present a significant public health burden worldwide. While a number of factors contribute to persistent HIV-1 infection in patients, the presence of a stable, long-lived reservoir of latent provirus represents a significant hurdle in realizing an effective cure. One potential strategy to eliminate HIV-1 reservoirs in patients is reactivation of latent provirus with latency reversing agents in combination with antiretroviral therapy, a strategy termed "shock and kill". This strategy has shown limited clinical effectiveness thus far, potentially due to limitations of the few therapeutics currently available. We have identified a novel class of benzazole compounds effective at inducing HIV-1 expression in several cellular models. These compounds do not act via histone deacetylase inhibition or T cell activation, and show specificity in activating HIV-1 in vitro. Initial exploration of structure-activity relationships and pharmaceutical properties indicates that these compounds represent a potential scaffold for development of more potent HIV-1 latency reversing agents.

Discovery of 2-(4-sulfonamidophenyl)-indole 3-carboxamides as potent and selective inhibitors with broad hepatitis C virus genotype activity targeting HCV NS4B

A novel series of 2-(4-sulfonamidophenyl)-indole 3-carboxamides was identified and optimized for activity against the HCV genotype 1b replicon resulting in compounds with potent and selective activity. Further evaluation of this series demonstrated potent activity across HCV genotypes 1a, 2a and 3a. Compound 4z had reduced activity against HCV genotype 1b replicons containing single mutations in the NS4B coding sequence (F98C and V105M) indicating that NS4B is the target. This novel series of 2-(4-sulfonamidophenyl)-indole 3-carboxamides serves as a promising starting point for a pan-genotype HCV discovery program.

Motor neuron disease. SMN2 splicing modifiers improve motor function and longevity in mice with spinal muscular atrophy

Spinal muscular atrophy (SMA) is a genetic disease caused by mutation or deletion of the survival of motor neuron 1 (SMN1) gene. A paralogous gene in humans, SMN2, produces low, insufficient levels of functional SMN protein due to alternative splicing that truncates the transcript. The decreased levels of SMN protein lead to progressive neuromuscular degeneration and high rates of mortality. Through chemical screening and optimization, we identified orally available small molecules that shift the balance of SMN2 splicing toward the production of full-length SMN2 messenger RNA with high selectivity. Administration of these compounds to Δ7 mice, a model of severe SMA, led to an increase in SMN protein levels, improvement of motor function, and protection of the neuromuscular circuit. These compounds also extended the life span of the mice. Selective SMN2 splicing modifiers may have therapeutic potential for patients with SMA.

Structure-activity relationship (SAR) optimization of 6-(indol-2-yl)pyridine-3-sulfonamides: identification of potent, selective, and orally bioavailable small molecules targeting hepatitis C (HCV) NS4B

A novel, potent, and orally bioavailable inhibitor of hepatitis C RNA replication targeting NS4B, compound 4t (PTC725), has been identified through chemical optimization of the 6-(indol-2-yl)pyridine-3-sulfonamide 2 to improve DMPK and safety properties. The focus of the SAR investigations has been to identify the optimal combination of substituents at the indole N-1, C-5, and C-6 positions and the sulfonamide group to limit the potential for in vivo oxidative metabolism and to achieve an acceptable pharmacokinetic profile. Compound 4t has excellent potency against the HCV 1b replicon, with an EC50 = 2 nM and a selectivity index of >5000 with respect to cellular GAPDH. Compound 4t has an overall favorable pharmacokinetic profile with oral bioavailability values of 62%, 78%, and 18% in rats, dogs, and monkeys, respectively, as well as favorable tissue distribution properties with a liver to plasma exposure ratio of 25 in rats.

An Expeditious Route to Novel 1,4,2-Benzodiazaphosphepin-5-one 2-Oxide Analogues

A short and efficient synthesis of the novel 1,4,2-benzodiazaphosphepin-5-one 2-oxide ring system, a phosphonamidate isostere of the 1,4-benzodiazepine-2,5-dione system, has been carried out in good overall yield. The key step is the base-induced cyclization of (2-aminobenzamido)methylphosphonates 6a-c to the 1,4,2-benzodiazaphosphepin-5-one 2-oxides 7a-c. Alkylation of 7b with methyl iodide gives the expected N-methyl analogue 9. When a tandem one-pot cyclization/alkylation is carried out from 6b in the presence of excess base, the sole isolable product obtained is the phosphonate 13, presumably via ethanolysis of a transiently formed 9. Carrying out the tandem cyclization/alkylation in the absence of excess base, however, affords only 9. Thionation of 7 with Lawesson's reagent occurs at either the phosphonamidate oxygen (P-2) or the amide carbonyl (C-5) depending on the steric constraint of the N-4 substituent.