Structure-guided optimization of small molecule c-Abl activators.

c-Abl kinase is maintained in its normal inactive state in the cell through an assembled, compact conformation. We describe two chemical series that bind to the myristoyl site of the c-Abl kinase domain and stimulate c-Abl activation. We hypothesize that these molecules activate c-Abl either by blocking the C-terminal helix from adopting a bent conformation that is critical for the formation of the autoinhibited conformation or by simply providing no stabilizing interactions to the bent conformation of this helix. Structure-based molecular modeling guided the optimization of binding and activation of c-Abl of these two chemical series and led to the discovery of c-Abl activators with nanomolar potency. The small molecule c-Abl activators reported herein could be used as molecular tools to investigate the biological functions of c-Abl and therapeutic implications of its activation.

Application of Solvent-Assisted Dual-Network Hydrogel in Water-Based Drilling Fluid for Lost Circulation Treatment in Fractured Formation.

During oil and gas well construction, lost circulation caused substantial nonoperation time and extra costs, and hydrogel, resilient and environmentally friendly, was one of the major types of material for lost circulation treatment. To migrate the weak bonding and hydrothermal degradation of conventional single network hydrogels, dual network (DN) hydrogel was prepared and immersed in solvents of polyethylene glycol (PEG), ethylene glycol, and glycerol. The swelling of DN gels at different temperatures was studied with water content and swelling rate tests, and the gel structural and morphology was characterized with attenuated total reflectance infrared spectroscopy (ATR-IR) and scanning electron microscopy test. Then, the compression test and fracture plugging performance test were conducted to study the strength of the gel. The results show that compared to those in ethylene glycol and glycerin, DN gel after immersion in PEG (DN-PEG) exhibits greater compression strength and better plugging performance even at high temperatures. The compression strength of DN-PEG was twice that of DN hydrogel before immersion, and its fracture plug breaking pressure can reach over 10.0 MPa. After undergoing hydrothermal treatment at 90 °C, the compression strength of the DN-PEG was nearly 20 times that of the DN hydrogel, and the fracture plug breaking pressure was still 2.81 MPa. According to ATR-IR spectroscopy, as the molecular weight of the solvent increases, more hydroxyl groups in the PEG have better ability to bind with hydrogen bonds, which greatly inhibits the swelling and polymer chain breakage, thereby reducing hydrothermal degradation in the strength of the dual-network hydrogel. Our work proposed an effective method to reduce the degradation of hydrogel in water at high temperature, and the prepared DN-PEG hydrogel was a promising material for lost circulation treatments in fractured formation.

Comparative analysis of the antibacterial activity of a novel peptide deformylase inhibitor, GSK1322322.

GSK1322322 is a novel peptide deformylase (PDF) inhibitor being developed for the intravenous and oral treatment of acute bacterial skin and skin structure infections and hospitalized patients with community-acquired pneumonia. The activity of GSK1322322 was tested against a global collection of clinical isolates of Haemophilus influenzae (n = 2,370), Moraxella catarrhalis (n = 115), Streptococcus pneumoniae (n = 947), Streptococcus pyogenes (n = 617), and Staphylococcus aureus (n = 940), including strains resistant to one or more marketed antibiotics. GSK1322322 had an MIC(90) of 1 µg/ml against M. catarrhalis and 4 µg/ml against H. influenzae, with 88.8% of ß-lactamase-positive strains showing growth inhibition at that concentration. All S. pneumoniae strains were inhibited by ≤ 4 µg/ml of GSK1322322, with an MIC(90) of 2 µg/ml. Pre-existing resistance mechanisms did not affect its potency, as evidenced by the MIC(90) of 1 µg/ml for penicillin, levofloxacin, and macrolide-resistant S. pneumoniae. GSK1322322 was very potent against S. pyogenes strains, with an MIC(90) of 0.5 µg/ml, irrespective of their macrolide resistance phenotype. This PDF inhibitor was also active against S. aureus strains regardless of their susceptibility to methicillin, macrolides, or levofloxacin, with an MIC(90) of 4 µg/ml in all cases. Time-kill studies showed that GSK1322322 had bactericidal activity against S. pneumoniae, H. influenzae, S. pyogenes, and S. aureus, demonstrating a ≥ 3-log(10) decrease in the number of CFU/ml at 4× MIC within 24 h in 29 of the 33 strains tested. Given the antibacterial potency demonstrated against this panel of organisms, GSK1322322 represents a valuable alternative therapy for the treatment of infectious diseases caused by drug-resistant pathogens.

Multiple Hydrogen Bonding-Assisted High-Strength Hydrogel of Silica/Polyacrylamide Nanocomposite Cross-Linked with Polyethylenimine.

The nanocomposite gel system has been successfully applied as a water shutoff agent to enhance oil recovery (EOR) or for plugging to control lost circulation events. In this study, the silica/polyacrylamide nanocomposite was synthesized via in situ free radical polymerization of acrylamide (AM) monomers in the presence of silica nanoparticles. The composite was cross-linked with polyethylenimine to prepare a high-strength hydrogel. The viscosity test was conducted to determine the gelation time of the gel. Rheological measurements and sand pack breakthrough pressure tests were carried out to measure the gel strength. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and scanning electron microscopy (SEM) tests were adopted to characterize the structure and morphology of the gel. The results show that compared to polyacrylamide (PAM) gel, the gelation time of the nanocomposite gel will decrease with increasing gel elasticity modulus, and the breakthrough pressure of the nanocomposite gel is 29.82 MPa, which increased by 65%. As shown in the ATR-FTIR test, this can be attributed to the presence of multiple hydrogen bonds for the PAM molecule with both silica and quartz sand particles. In the composite gel, hydrogen bonding mainly forms between the O atoms of PAM and the H atom on the surface of silica, enhancing gel strength and elasticity modulus with more cross-linking density and less porosity. Moreover, H bonding between additional -NH2 of PAM and quartz sand particles helps improve gel plugging pressure. However, in the silica and PAM mixture gel, the H bonding of silica occupies -NH2 of PAM, which became unavailable to attach on the sand surface, reducing the breakthrough pressure by 30%, although it can enhance the rheological strength. This study suggests that in situ composite of silica in PAM can not only greatly improve gel rheological strength but also help maintain the strong adhesion of PAM molecules onto quartz sand, resulting in better plugging performance in the sand reservoir.

Pharmacokinetics and Safety Study of HN0037, a Novel Anti-Human Herpes Simplex Virus Inhibitor, in Healthy Volunteers.

HN0037 is a helicase-primase inhibitor developed to treat herpes simplex virus (HSV) infection. This study evaluated the safety, tolerability, and pharmacokinetics of HN0037, following oral administration in healthy volunteers. This double-blind, placebo-controlled, phase 1 study comprised two parts. In part 1, a single escalating dose of 10, 30, 60, 120, 200, 300, and 400 mg was assessed, and the food effect was evaluated in the 200-mg cohort. In part 2, a multiple dose evaluation involving 30 and 100 mg once a day was conducted for 14 days. Following single oral doses, the systemic exposure of HN0037 increased in a proportional manner over the lower dose range (10-120 mg) and in a subproportional manner over the higher dose range (200-400 mg). Following multiple oral doses, significant drug accumulation of systemic exposure was found at steady state, and the half-life ranged 50.4-61.0 h. The food effect study results indicated that a high-fat meal had a marginal impact on HN0037's pharmacokinetics. No differences were observed in the incidence of adverse events between HN0037 and placebo groups in either study. These results demonstrate that HN0037 is safe and well-tolerated, supporting further clinical development.

Discovery of Orally Bioavailable Ligand Efficient Quinazolindiones as Potent and Selective Tankyrases Inhibitors.

We report herein the discovery of quinazolindiones as potent and selective tankyrase inhibitors. Elucidation of the structure-activity relationship of the lead compound 1g led to truncated analogues that have good potency in cells, pharmacokinetic (PK) properties, and excellent selectivity. Compound 21 exhibited excellent potencies in cells and proliferation studies, good selectivity, in vitro activities, and an excellent PK profile. Compound 21 also inhibited H292 xenograft tumor growth in nude mice. The synthesis, biological, pharmacokinetic, in vivo efficacy studies, and safety profiles of compounds are presented.

Identification and Optimization of Novel Small c-Abl Kinase Activators Using Fragment and HTS Methodologies.

Abelson kinase (c-Abl) is a ubiquitously expressed, nonreceptor tyrosine kinase which plays a key role in cell differentiation and survival. It was hypothesized that transient activation of c-Abl kinase via displacement of the N-terminal autoinhibitory "myristoyl latch", may lead to an increased hematopoietic stem cell differentiation. This would increase the numbers of circulating neutrophils and so be an effective treatment for chemotherapy-induced neutropenia. This paper describes the discovery and optimization of a thiazole series of novel small molecule c-Abl activators, initially identified by a high throughput screening. Subsequently, a scaffold-hop, which exploited the improved physicochemical properties of a dihydropyrazole analogue, identified through fragment screening, delivered potent, soluble, cell-active c-Abl activators, which demonstrated the intracellular activation of c-Abl in vivo.

Discovery of a First-in-Class Gut-Restricted RET Kinase Inhibitor as a Clinical Candidate for the Treatment of IBS.

Abdominal pain and abnormal bowel habits represent major symptoms for irritable bowel syndrome (IBS) patients that are not adequately managed. Although the etiology of IBS is not completely understood, many of the functions of the gastrointestinal (GI) tract are regulated by the enteric nervous system (ENS). Inflammation or stress-induced expression of growth factors or cytokines may lead to hyperinnervation of visceral afferent neurons in GI tract and contribute to the pathophysiology of IBS. Rearranged during transfection (RET) is a neuronal growth factor receptor tyrosine kinase critical for the development of the ENS as exemplified by Hirschsprung patients who carry RET loss-of-function mutations and lack normal colonic innervation leading to colonic obstruction. Similarly, RET signaling in the adult ENS maintains neuronal function by contributing to synaptic formation, signal transmission, and neuronal plasticity. Inhibition of RET in the ENS represents a novel therapeutic strategy for the normalization of neuronal function and the symptoms of IBS patients. Herein, we describe our screening effort and subsequent structure-activity relationships (SARs) in optimizing potency, selectivity, and mutagenicity of the series, which led to the discovery of a first-in-class, gut-restricted RET kinase inhibitor, 2-(4-(4-ethoxy-6-oxo-1,6-dihydropyridin-3-yl)-2-fluorophenyl)-N-(5-(1,1,1-trifluoro-2-methylpropan-2-yl)isoxazol-3-yl)acetamide (15, GSK3179106), as a clinical candidate for the treatment of IBS. GSK3179106 is a potent, selective, and gut-restricted pyridone hinge binder small molecule RET kinase inhibitor with a RET IC50 of 0.3 nM and is efficacious in vivo.

Interactions of very long-chain saturated fatty acids with serum albumin.

The remarkable binding properties of serum albumin have been investigated extensively, but little is known about an important class of fatty acids, the very long-chain saturated fatty acids (VLCFA; >18 carbons). Although VLCFA are metabolized efficiently in normal individuals, they are markers for and possibly causative agents of several peroxisomal disorders. We studied the binding of [(13)C]carboxyl-enriched arachidic (C20:0), behenic (C22:0), lignoceric (C24:0), and hexacosanoic (C26:0) acids to bovine serum albumin (BSA) by (13)C-NMR spectroscopy. For each VLCFA, the NMR spectra showed multiple signals at chemical shifts previously identified for long-chain fatty acids (12-18 carbons), suggesting stabilization of binding by similar, if not identical, interactions of the fatty acid carboxyl anion with basic amino acid residues. The maximal binding (mol of VLCFA/mol of BSA) and the number of observed binding sites decreased with increasing chain length, from 4-5 for C20:0, 3-4 for C22:0, and 2 for C24:0; we validated our previous conclusion that BSA has only one site for C26:0 (Ho, J. K., H. Moser, Y. Kishimoto, and J. A. Hamilton. 1995. J. Clin. Invest. 96: 1455-1463). Analysis of chemical shifts suggested that the highest affinity sites for VLCFA are low affinity sites for long-chain fatty acids. In competition experiments with (13)C-labeled C22:0 (3 mol/mol of BSA) and unlabeled oleic acid, C22:0 bound to BSA in the presence of up to 4 mol of oleic acid/mol of BSA, but 1 mol was shifted into a different site. Our studies suggest that albumin has adequate binding capacity for the low plasma levels of VLCFA with 20 to 26 carbons, but the protein may not be able to bind longer chain VLCFA.