Scaffold modifications to the 4-(4,4-dimethylpiperidinyl) 2,6-dimethylpyridinyl class of HIV-1 allosteric integrase inhibitors.

Allosteric integrase inhibitors (ALLINIs) of HIV-1 may hold promise as a novel mechanism for HIV therapeutics and cure. Scaffold modifications to the 4-(4,4-dimethylpiperidinyl) 2,6-dimethylpyridinyl class of ALLINIs provided a series of potent compounds with differentiated 5/6 fused ring systems. Notably, inhibitors containing the 1,2,4-triazolopyridine and imidazopyridine core exhibited single digit nM antiviral potency and low to moderate clearance after intravenous (IV) dosing in rat pharmacokinetic (PK) studies. The 1,2,4-triazolopyridines showed a higher oral exposure when compared to the imidazopyridines. Further modifications to the C5 substituent of the 1,2,4-triazolopyridines resulted in a new lead compound, which had improved rat IV/PO PK compared to the former lead compound GSK3739936, while maintaining antiviral potency. Structure-activity relationships (SAR) and rat pharmacokinetic profiles of this series are discussed.

Small molecule and macrocyclic pyrazole derived inhibitors of myeloperoxidase (MPO).

Myeloperoxidase (MPO), a critical enzyme in antimicrobial host-defense, has been implicated in chronic inflammatory diseases such as coronary artery disease. The design and evaluation of MPO inhibitors for the treatment of cardiovascular disease are reported herein. Starting with the MPO and triazolopyridine 3 crystal structure, novel inhibitors were designed incorporating a substituted pyrazole, which allowed for substituents to interact with hydrophobic and hydrophilic patches in the active site. SAR exploration of the substituted pyrazoles led to piperidine 17, which inhibited HOCl production from activated neutrophils with an IC50 value of 2.4 µM and had selectivity against thyroid peroxidase (TPO). Optimization of alkylation chemistry on the pyrazole nitrogen facilitated the preparation of many analogs, including macrocycles designed to bridge two hydrophobic regions of the active site. Multiple macrocyclization strategies were pursued to prepare analogs that optimally bound to the active site, leading to potent macrocyclic MPO inhibitors with TPO selectivity, such as compound 30.

Structure-based amelioration of PXR transactivation in a novel series of macrocyclic allosteric inhibitors of HIV-1 integrase.

Previous studies have identified a series of imidazo[1,2-a]pyridine (IZP) derivatives as potent allosteric inhibitors of HIV-1 integrase (ALLINIs) and virus infection in cell culture. However, IZPs were also found to be relatively potent activators of the pregnane-X receptor (PXR), raising the specter of induction of CYP-mediated drug disposition pathways. In an attempt to modify PXR activity without affecting anti-HIV-1 activity, rational structure-based design and modeling approaches were used. An X-ray cocrystal structure of (S,S)-1 in the PXR ligand binding domain (LBD) allowed an examination of the potential of rational structural modifications designed to abrogate PXR. The introduction of bulky basic amines at the C-8 position provided macrocyclic IZP derivatives that displayed potent HIV-1 inhibitory activity in cell culture with no detectable PXR transactivation at the highest concentration tested.

Discovery of potent and efficacious pyrrolopyridazines as dual JAK1/3 inhibitors.

A series of potent dual JAK1/3 inhibitors have been developed from a moderately selective JAK3 inhibitor. Substitution at the C6 position of the pyrrolopyridazine core with aryl groups provided exceptional biochemical potency against JAK1 and JAK3 while maintaining good selectivity against JAK2 and Tyk2. Translation to in vivo efficacy was observed in a murine model of chronic inflammation. X-ray co-crystal structure determination confirmed the presumed inhibitor binding orientation in JAK3. Efforts to reduce hERG channel inhibition will be described.

Less invasive stabilization system for the management of proximal tibia fractures.

BACKGROUND: Proximal tibia fractures are difficult to treat especially when soft tissues are compromised by conventional open reduction and internal fixation with high complication rates. Many methods have been tried to manage these fractures. Less invasive stabilization system (LISS) is the latest technology applied for these injuries. This report presents clinical results of the LISS for the treatment of complex proximal tibia fractures. MATERIALS AND METHODS: From June 2007 to May 2010, total of 35 cases of the proximal tibia fractures (19 AO type 41A, 11 type 41B and five AO type 41C) were treated with the LISS technique. Clinical and radiological evaluation was done at 6, 10, 14, 20, 24 weeks and 9, 12, 18 and 24 months, respectively. RESULTS: The mean age of the patients was 50.17 years (range 20-73 years); male patients were 21 and female 14. The mean follow-up time was 31.42 months (range 21-42 months). The patients were evaluated using Knee Society scores, and the mean score was 92.11 (range 84-100); the mean full weight bearing time was 15.8 weeks (range 12-22), and union time was 25.17 weeks (range 20-29). Superficial infections and slight mal-alignment were seen on five patients each. CONCLUSION: The less invasive stabilization internal fixator system can be used successfully to treat complex proximal tibia fractures with minimal complications. It can be an alternative method for the treatment of the proximal tibia fractures.

Design, Synthesis, and Preclinical Profiling of GSK3739936 (BMS-986180), an Allosteric Inhibitor of HIV-1 Integrase with Broad-Spectrum Activity toward 124/125 Polymorphs.

Allosteric HIV-1 integrase inhibitors (ALLINIs) have garnered special interest because of their novel mechanism of action: they inhibit HIV-1 replication by promoting aberrant integrase multimerization, leading to the production of replication-deficient viral particles. The binding site of ALLINIs is in a well-defined pocket formed at the interface of two integrase monomers that is characterized by conserved residues along with two polymorphic amino acids at residues 124 and 125. The design, synthesis, and optimization of pyridine-based allosteric integrase inhibitors are reported here. Optimization was conducted with a specific emphasis on the inhibition of the 124/125 polymorphs such that the designed compounds showed excellent potency in vitro against majority of the 124/125 variants. In vivo profiling of promising preclinical lead 29 showed that it exhibited a good pharmacokinetic (PK) profile in preclinical species, which resulted in a low predicted human efficacious dose. However, findings in rat toxicology studies precluded further development of 29.

Discovery of BMS-986339, a Pharmacologically Differentiated Farnesoid X Receptor Agonist for the Treatment of Nonalcoholic Steatohepatitis.

While several farnesoid X receptor (FXR) agonists under clinical investigation for the treatment of nonalcoholic steatohepatitis (NASH) have shown beneficial effects, adverse effects such as pruritus and elevation of plasma lipids have limited their clinical efficacy and approvability. Herein, we report the discovery and preclinical evaluation of compound 32 (BMS-986339), a nonbile acid FXR agonist with a pharmacologically distinct profile relative to our previously reported agonist BMS-986318. Compound 32 exhibited potent in vitro and in vivo activation of FXR, albeit with a context-dependent profile that resulted in tissue-selective effects in vivo. To our knowledge, this is the first report that demonstrates differential induction of Fgf15 in the liver and ileum by FXR agonists in vivo. Compound 32 demonstrated robust antifibrotic efficacy despite reduced activation of certain genes in the liver, suggesting that the additional pharmacology of BMS-986318 does not further benefit efficacy, possibly presenting an opportunity for reduced adverse effects. Further evaluation in humans is warranted to validate this hypothesis.

Molecular basis for the inhibition of human NMPRTase, a novel target for anticancer agents.

Nicotinamide phosphoribosyltransferase (NMPRTase) has a crucial role in the salvage pathway of NAD+ biosynthesis, and a potent inhibitor of NMPRTase, FK866, can reduce cellular NAD+ levels and induce apoptosis in tumors. We have determined the crystal structures at up to 2.1-A resolution of human and murine NMPRTase, alone and in complex with the reaction product nicotinamide mononucleotide or the inhibitor FK866. The structures suggest that Asp219 is a determinant of substrate specificity of NMPRTase, which is confirmed by our mutagenesis studies. FK866 is bound in a tunnel at the interface of the NMPRTase dimer, and mutations in this binding site can abolish the inhibition by FK866. Contrary to current knowledge, the structures show that FK866 should compete directly with the nicotinamide substrate. Our structural and biochemical studies provide a starting point for the development of new anticancer agents.

Discovery and Optimization of Novel Pyrazolopyrimidines as Potent and Orally Bioavailable Allosteric HIV-1 Integrase Inhibitors.

The standard of care for HIV-1 infection, highly active antiretroviral therapy (HAART), combines two or more drugs from at least two classes. Even with the success of HAART, new drugs with novel mechanisms are needed to combat viral resistance, improve adherence, and mitigate toxicities. Active site inhibitors of HIV-1 integrase are clinically validated for the treatment of HIV-1 infection. Here we describe allosteric inhibitors of HIV-1 integrase that bind to the LEDGF/p75 interaction site and disrupt the structure of the integrase multimer that is required for the HIV-1 maturation. A series of pyrazolopyrimidine-based inhibitors was developed with a vector in the 2-position that was optimized by structure-guided compound design. This resulted in the discovery of pyrazolopyrimidine 3, which was optimized at the 2- and 7-positions to afford 26 and 29 as potent allosteric inhibitors of HIV-1 integrase that exhibited low nanomolar antiviral potency in cell culture and encouraging PK properties.

Crystal structure of human nicotinamide riboside kinase.

Nicotinamide riboside kinase (NRK) has an important role in the biosynthesis of NAD(+) as well as the activation of tiazofurin and other NR analogs for anticancer therapy. NRK belongs to the deoxynucleoside kinase and nucleoside monophosphate (NMP) kinase superfamily, although the degree of sequence conservation is very low. We report here the crystal structures of human NRK1 in a binary complex with the reaction product nicotinamide mononucleotide (NMN) at 1.5 A resolution and in a ternary complex with ADP and tiazofurin at 2.7 A resolution. The active site is located in a groove between the central parallel beta sheet core and the LID and NMP-binding domains. The hydroxyl groups on the ribose of NR are recognized by Asp56 and Arg129, and Asp36 is the general base of the enzyme. Mutation of residues in the active site can abolish the catalytic activity of the enzyme, confirming the structural observations.

Potent Triazolopyridine Myeloperoxidase Inhibitors.

Myeloperoxidase (MPO) generates reactive oxygen species that potentially contribute to many chronic inflammatory diseases. A recently reported triazolopyrimidine MPO inhibitor was optimized to improve acid stability and remove methyl guanine methyl transferase (MGMT) activity. Multiple synthetic routes were explored that allowed rapid optimization of a key benzyl ether side chain. Crystal structures of inhibitors bound to the MPO active site demonstrated alternate binding modes and guided rational design of MPO inhibitors. Thioether 36 showed significant inhibition of MPO activity in an acute mouse inflammation model after oral dosing.

Crystal structure of human Taspase1, a crucial protease regulating the function of MLL.

Taspase1 catalyzes the proteolytic processing of the mixed lineage leukemia (MLL) nuclear protein, which is required for maintaining Hox gene expression patterns. Chromosomal translocations of the MLL gene are associated with leukemia in infants. Taspase1, a threonine aspartase, is a member of the type 2 asparaginase family, but is the only protease in this family. We report here the crystal structures of human activated Taspase1 and its proenzyme, as well as the characterization of the effects of mutations in the active site region using a newly developed fluorogenic assay. The structure of Taspase1 has significant differences from other asparaginases, especially near the active site. Mutation of the catalytic nucleophile, Thr234, abolishes autocatalytic processing in cis but does not completely block proteolysis in trans. The structure unexpectedly showed the binding of a chloride ion in the active site, and our kinetic studies confirm that chlorides ions are inhibitors of this enzyme at physiologically relevant concentrations.

Triazolopyrimidines identified as reversible myeloperoxidase inhibitors.

Myeloperoxidase, a mammalian peroxidase involved in the immune system as an anti-microbial first responder, can produce hypochlorous acid in response to invading pathogens. Myeloperoxidase has been implicated in several chronic pathological diseases due to the chronic production of hypochlorous acid, as well as other reactive radical species. A high throughput screen and triaging protocol was developed to identify a reversible inhibitor of myeloperoxidase toward the potential treatment of chronic diseases such as atherosclerosis. The identification and characterization of a reversible myeloperoxidase inhibitor, 7-(benzyloxy)-3H-[1,2,3]triazolo[4,5-d]pyrimidin-5-amine is described.

Developing Adnectins that target SRC co-activator binding to PXR: a structural approach toward understanding promiscuity of PXR.

The human pregnane X receptor (PXR) is a promiscuous nuclear receptor that functions as a sensor to a wide variety of xenobiotics and regulates expression of several drug metabolizing enzymes and transporters. We have generated "Adnectins", derived from 10th fibronectin type III domain ((10)Fn3), that target the PXR ligand binding domain (LBD) interactions with the steroid receptor co-activator-1 (SRC-1) peptide, displacing SRC-1 binding. Adnectins are structurally homologous to the immunoglobulin superfamily. Three different co-crystal structures of PXR LBD with Adnectin-1 and CCR1 (CC chemokine receptor-1) antagonist Compound-1 were determined. This structural information was used to modulate PXR affinity for a related CCR1 antagonist compound that entered into clinical trials for rheumatoid arthritis. The structures of PXR with Adnectin-1 reveal specificity of Adnectin-1 in not only targeting the interface of the SRC-1 interactions but also engaging the same set of residues that are involved in binding of SRC-1 to PXR. Substituting SRC-1 with Adnectin-1 does not alter the binding conformation of Compound-1 in the ligand binding pocket. The structure also reveals the possibility of using Adnectins as crystallization chaperones to generate structures of PXR with compounds of interest.

Structure-Based Design of Selective Janus Kinase 2 Imidazo[4,5-d]pyrrolo[2,3-b]pyridine Inhibitors.

Early hit to lead work on a pyrrolopyridine chemotype provided access to compounds with biochemical and cellular potency against Janus kinase 2 (JAK2). Structure-based drug design along the extended hinge region of JAK2 led to the identification of an important H-bond interaction with the side chain of Tyr 931, which improved JAK family selectivity. The 4,5-dimethyl thiazole analogue 18 demonstrated high levels of JAK family selectivity and was identified as a promising lead for the program.

Discovery of a Highly Selective JAK2 Inhibitor, BMS-911543, for the Treatment of Myeloproliferative Neoplasms.

JAK2 kinase inhibitors are a promising new class of agents for the treatment of myeloproliferative neoplasms and have potential for the treatment of other diseases possessing a deregulated JAK2-STAT pathway. X-ray structure and ADME guided refinement of C-4 heterocycles to address metabolic liability present in dialkylthiazole 1 led to the discovery of a clinical candidate, BMS-911543 (11), with excellent kinome selectivity, in vivo PD activity, and safety profile.

Minimally invasive plate osteosynthesis for distal tibial fractures.

PURPOSE: To review the outcomes of 53 patients who underwent minimally invasive plate osteosynthesis (MIPO) for distal tibial fractures. METHODS: Medical records of 31 men and 22 women aged 22 to 78 (mean, 51) years who underwent MIPO using a locking compression plate for distal tibial fractures of the left (n=28) and right (n=25) legs with or without intra-articular extension were reviewed. RESULTS: Patients were followed up for a mean of 26 (range, 24-38) months. The mean time from injury to surgery was 9 (range, 3-12) days. The mean operating time was 105 (range, 75-180) minutes. The mean hospital stay was 16 (range, 8-25) days. Non-weight bearing walking with a crutch was started after a mean of 5.7 (range, 3-9) days. The mean time to callus formation was 12 (range, 8-15) weeks. The mean time to full weight bearing was 15 (range, 8-22) weeks. The mean time to bone union was 25 (range, 20-30) weeks. All except 2 fractures united anatomically. At 10 months, the range of motion of the ankle joint in all patients was similar to the contralateral side. Two patients had malunion but this was not clinically significant. Five patients had superficial infection, and 2 patients had persistent pain. CONCLUSION: MIPO is effective for closed, unstable fractures of the distal tibia. It reduces surgical trauma and preserves fracture haematoma.

Discovery of the CCR1 antagonist, BMS-817399, for the treatment of rheumatoid arthritis.

High-affinity, functionally potent, urea-based antagonists of CCR1 have been discovered. Modulation of PXR transactivation has revealed the selective and orally bioavailable CCR1 antagonist BMS-817399 (29), which entered clinical trials for the treatment of rheumatoid arthritis.

Ischemic gall bladder perforation: a complication of type A aortic dissection.

Malperfusion of end organs occurs in 20% to 40% patients with acute type A aortic dissection. Because irreversible ischemia is a time-dependent event, expedient diagnosis and treatment are necessary. We herein report successful surgical management of a patient with acute type A aortic dissection causing transient gut ischemia and a rare gall bladder perforation. We implemented one-stage surgical and laparoscopic management approach for the diagnosis and treatment. Increased awareness of this complication and appropriate use of available diagnostic tools may improve the outcome in similar patients. Patients with aortic dissection complicated by visceral ischemia require a prompt sequential and rational multidisciplinary approach for successful management.

Papillary fibroelastoma of the aortic valve--a case report and literature review.

The prevalence of primary cardiac tumour ranges from 0.0017-0.28% and papillary fibroelastoma is rare but not uncommon benign cardiac neoplasm. Currently, with the advent of higher-resolution imaging technology especially transoesophageal echocardiography such cases being recognized frequently. The clinical presentation of these tumours varies from asymptomatic to severe ischaemic or embolic complications. We herein, present a 50-year-old female patient with a papillary fibroelastoma of the aortic valve arising from the endocardium of the right coronary cusp very close to the commissure between the right and non-coronary cusps. The patient presented with angina-like chest pain and was investigated using echocardiography and CT angiographic modalities in addition to the usual investigations. The differential diagnosis considered was a thrombus, myxoma, Lambl's excrescence and infective vegetation. The surgical management included a prompt resection of the tumour on cardiopulmonary bypass avoiding injury to the aortic valve. The patient recovered well. A review of the literature suggests that the cardiac papillary fibroelastoma is a rare but potentially treatable cause of embolic stroke and other fatal complications, therefore, a strong suspicion; appropriate use of imaging modality, preoperative anticoagulation and urgent surgical resection is warranted. Also, possibility of this diagnosis should be kept in mind while managing cardiac or valvular tumours.