Chemical tools for the Gid4 subunit of the human E3 ligase C-terminal to LisH (CTLH) degradation complex

We have developed a novel chemical handle (PFI-E3H1) and a chemical probe (PFI-7) as ligands for the Gid4 subunit of the human E3 ligase CTLH degradation complex. Through an efficient initial hit-ID campaign, structure-based drug design (SBDD) and leveraging the sizeable Pfizer compound library, we identified a 500 nM ligand for this E3 ligase through file screening alone. Further exploration identified a vector that is tolerant to addition of a linker for future chimeric molecule design. The chemotype was subsequently optimized to sub-100 nM Gid4 binding affinity for a chemical probe. These novel tools, alongside the suitable negative control also identified, should enable the interrogation of this complex human E3 ligase macromolecular assembly.

Late-Stage Microsomal Oxidation Reduces Drug-Drug Interaction and Identifies Phosphodiesterase 2A Inhibitor PF-06815189

Late-stage oxidation using liver microsomes was applied to phosphodiesterase 2 inhibitor 1 to reduce its clearance by cytochrome P450 enzymes, introduce renal clearance, and minimize the risk for victim drug–drug interactions. This approach yielded PF-06815189 (2) with improved physicochemical properties and a mixed metabolic profile. This example highlights the importance of C–H diversification methods to drug discovery.

Design of Pyridopyrazine-1,6-dione γ-Secretase Modulators that Align Potency, MDR Efflux Ratio, and Metabolic Stability

Herein we describe the design and synthesis of a series of pyridopyrazine-1,6-dione γ-secretase modulators (GSMs) for Alzheimer's disease (AD) that achieve good alignment of potency, metabolic stability, and low MDR efflux ratios, while also maintaining favorable physicochemical properties. Specifically, incorporation of fluorine enabled design of metabolically less liable lipophilic alkyl substituents to increase potency without compromising the sp(3)-character. The lead compound 21 (PF-06442609) displayed a favorable rodent pharmacokinetic profile, and robust reductions of brain Aβ42 and Aβ40 were observed in a guinea pig time-course experiment.

Synthesis of pyridopyrazine-1,6-diones from 6-hydroxypicolinic acids via a one-pot coupling/cyclization reaction

A facile one-pot synthesis of 3,4-dihydro-1H-pyrido[1,2-a]pyrazine-1,6(2H)-diones (pyridopyrazine-1,6-diones) has been developed which employs a sequential coupling/cyclization reaction of 6-hydroxypicolinic acids and β-hydroxylamines. The transformation proceeds in good yield under mild conditions using O-(7-aza-1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HATU) to both carry out the amide formation and activate the hydroxyl group for intramolecular alkylation.

Design and synthesis of dihydrobenzofuran amides as orally bioavailable, centrally active γ-secretase modulators

We report the discovery and optimization of a novel series of dihydrobenzofuran amides as γ-secretase modulators (GSMs). Strategies for aligning in vitro potency with drug-like physicochemical properties and good microsomal stability while avoiding P-gp mediated efflux are discussed. Lead compounds such as 35 and 43 have moderate to good in vitro potency and excellent selectivity against Notch. Good oral bioavailability was achieved as well as robust brain Aβ42 lowering activity at 100 mg/kg po dose.

Systematic review: association of polycystic ovary syndrome with metabolic syndrome and non-alcoholic fatty liver disease

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common disorder for women of child-bearing age and is associated with metabolic syndrome (MS).

AIM

To assess the literature for associations between polycystic ovary syndrome and non-alcoholic fatty liver disease (NAFLD).

METHODS

We performed a systematic review using PubMed-search for peer-reviewed articles related to polycystic ovary syndrome and NAFLD. Articles were summarised and grouped according to different sections defining interactions of polycystic ovary syndrome with metabolic syndrome and non-alcoholic fatty liver disease as well as risk factors, pathogenic pathways and treatment options.

RESULTS

Obesity is a common factor involved in both polycystic ovary syndrome and non-alcoholic fatty liver disease. Obesity causes non-alcoholic fatty liver disease and aggravates hirsutism and menstrual disorders in polycystic ovary syndrome. Insulin resistance, a hallmark of metabolic syndrome is observed in 50-80% of women with polycystic ovary syndrome and patients with non-alcoholic fatty liver disease. Recent findings suggest that women with polycystic ovary syndrome may be at risk for developing non-alcoholic fatty liver disease and conversely, non-alcoholic fatty liver disease may be a risk for polycystic ovary syndrome. Based on the association of polycystic ovary syndrome and other metabolic abnormalities, such as insulin resistance, hyperandrogenism, obesity and non-alcoholic fatty liver disease, the candidate genes have been speculated for polycystic ovary syndrome. Closer scrutiny of these genes placed most of their proteins at the crossroads of three highly inter-related conditions: metabolic syndrome, obesity and non-alcoholic fatty liver disease. In most studies, the prevalence of both polycystic ovary syndrome and non-alcoholic fatty liver disease rises proportionally to the degree of insulin resistance and increases in the mass of adipose tissue.

CONCLUSIONS

Non-alcoholic fatty liver disease is considered as the hepatic manifestation of metabolic syndrome. Similarly, it seems appropriate to consider polycystic ovary syndrome as the ovarian manifestation of metabolic syndrome. Both these conditions can co-exist and may respond to similar therapeutic strategies.

Novel γ-secretase modulators: a review of patents from 2008 to 2010

INTRODUCTION

The amyloid precursor protein is first cleaved by β-secretase to generate a 99-residue membrane-bound CTF (C99 or β-CTF), which is subsequently cleaved by γ-secretase to generate amyloid β (Aβ) peptides and the APP intracellular domain. The amyloidogenic Aβ42 has attracted considerable attention because it is thought to be the most pathogenic species associated with Alzheimer's disease progression. New classes of compounds, called γ-secretase modulators (GSMs), have been shown to selectively lower Aβ42 production without shutting down key γ-secretase-dependent signaling pathways. This has become an important therapeutic strategy aimed at modulating Aβ production.

AREAS COVERED

The progress on the clinical development of γ-secretase inhibitors is briefly covered in this review, followed by a discussion of the potential differentiating attributes of GSMs. Then, the patent literature covering novel GSMs is reviewed, focusing on patents from 2008 to 2010.

EXPERT OPINION

Much progress has been made in the past 2 years on developing GSMs with improved potency for lowering the production of Aβ42. However, many of these chemotypes are in a challenging chemical space and generally possess higher lipophilicity than most CNS drugs. It will be important to gain a better understanding of the specific target(s) that these GSMs interact with in order to facilitate future drug design efforts.

Diabetes alters protein expression of hyperpolarization-activated cyclic nucleotide-gated channel subunits in rat nodose ganglion cells

Vagal afferent neurons, serving as the primary afferent limb of the parasympathetic reflex, could be involved in diabetic autonomic neuropathy. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed in the vagal afferent neurons and play an important role in determining cell membrane excitation. In the present study, the protein expression and the electrophysiological characteristics of HCN channels were investigated in nodose ganglion (NG) afferent neurons (A-fiber and C-fiber neurons) from sham and streptozotocin (STZ)-induced diabetic rats. In the sham NG, HCN1, HCN3, and HCN4 were expressed in the A-fiber neurons; and HCN2, HCN3, and HCN4 were expressed in the C-fiber neurons. Compared to the sham NG neurons, diabetes induced the expression of HCN2 in the A-fiber neurons besides overexpression of HCN1 and HCN3; and enhanced the expression of HCN2 and HCN3 in C-fiber neurons. In addition, whole-cell patch-clamp data revealed diabetes also increased HCN currents in A-fiber and C-fiber neurons. However, we found that diabetes did not alter the total nodose afferent neuron number and the ratio of A-fiber/C-fiber neurons. These results indicate that diabetes induces the overexpression of HCN channels and the electrophysiological changes of HCN currents in the A- and C-fiber nodose neurons, which might contribute to the diabetes-induced alteration of cell excitability in the vagal afferent neurons.

Synthesis and antibacterial activity of the C-7 side chain of 3-aminoquinazolinediones

A novel series of bacterial topoisomerase (3-aminoquinazolinediones) inhibitors are described. The side-chain SAR against Gram-positive and Gram-negative organisms as well as DNA gyrase activity is reported.

The impact of a rural emergency department rotation on applicant ranking of a US emergency medicine residency program

INTRODUCTION

Few US emergency medicine (EM) residency programs have been located in rural states due to program requirements for emergency department (ED) patient volume. Recent revision to the program requirements now permits 'educationally justifiable exceptions' to the patient population requirement, 'such as clinical sites in a rural setting', and some EM residency programs now plan to offer rural ED clinical experiences as a required curricular component. The impact of a required rural EM rotation on the ranking decisions of applicants is important to residency programs seeking to attract the most desirable applicants.

OBJECTIVE

To assess the impact of a required rural ED rotation on applicant ranking of an EM residency program in the US National Resident Matching Program (NMRP).

METHODS

All applicants to the study's EM residency program completing the interview portion of the application process received a mailed and emailed survey following the release of the 2004 NMRP results. The survey included questions addressing the rural/non-rural classification of the location of the applicants' childhood home, medical school, and anticipated future practice.

RESULTS

Of 46 eligible subjects, 32 (69.6%) completed the survey. Of subjects with a rural childhood, 73.3% reported a positive impact on rank order (95% CI 50.9-95.7%) and 26.7% reported no impact (CI 4.3-49.1%); 81.3% of subjects with non-rural backgrounds reported no impact (CI 62.2-100%), 12.5% higher rank (CI 0-28.7%), and 6.3% lower (CI 0-18.2%). If planning a future practice in a rural community, 83.3% reported positive impact (CI 62.2-100%) and 16.7% no impact (CI 0-37.8%); 78.9% of subjects anticipating future practice in non-rural communities reported no impact (CI 60.6-97.3%), 15.8% higher rank (CI 0-32.2%), and 5.3% lower (CI 0-15.4). Of the subjects attending medical school in rural states, 52.2% reported a positive impact (CI 31.8-72.6%) and 47.8% no impact (CI 27.4-68.2%), while 75% of graduates of medical schools in non-rural states reported no impact (CI 32.6-100%) and 25% (CI 0-67.4%) a negative impact.

CONCLUSION

The presence of a rural ED rotation did not adversely impact EM residency applicants' ranking of the program.

Structure-activity relationships of 3-aminoquinazolinediones, a new class of bacterial type-2 topoisomerase (DNA gyrase and topo IV) inhibitors

A series of 3-aminoquinazolinediones was synthesized and evaluated for its antibacterial and DNA gyrase activity. The SAR around the quinazolinedione core was explored and the optimal substitutions were combined to give two compounds, 2r and 2s, with exceptional enzyme potency (IC50 = 0.2 microM) and activity against gram-positive organisms (MIC's = 0.015-0.06 microg/mL).

3-Aminoquinazolinediones as a New Class of Antibacterial Agents Demonstrating Excellent Antibacterial Activity Against Wild-Type and Multidrug Resistant Organisms

The 3-aminoquinzolinediones represent a new series of antibacterial agents structurally related to the fluoroquinolones. They are inhibitors of bacterial gyrase and topoisomerase IV and demonstrate clinically useful antibacterial activity against fastidious Gram-negative and Gram-positive organisms, including multidrug- and fluoroquinolone-resistant organisms. These agents also demonstrate in vivo efficacy in murine systemic infection models.

Tyrosine kinase inhibitors. 19. 6-Alkynamides of 4-anilinoquinazolines and 4-anilinopyrido[3,4-d]pyrimidines as irreversible inhibitors of the erbB family of tyrosine kinase receptors

Structure-activity relationships for inhibition of erbB1, erbB2, and erbB4 were determined for a series of alkynamide analogues of quinazoline- and pyrido[3,4-d]pyrimidine-based compounds. The compounds were prepared by coupling the appropriate 6-aminoquinazolines or 6-aminopyrido[3,4-d]pyrimidines with alkynoic acids, using EDCI.HCl in pyridine. The compounds showed pan-erbB enzyme inhibition but were on average about 10-fold more potent against erbB1 than against erbB2 and erbB4. For cellular inhibition, the nature of the alkylating side chains was an important determinant, with 5-dialkylamino-2-pentynamide type Michael acceptors providing the highest potency. This is suggested to be due to an improved ability of the amine to participate in an autocatalysis of the Michael reaction with enzyme cysteine residues. Pyrido[3,4-d]pyrimidine analogue 39 was selected for in vivo evaluation and achieved tumor regressions at 10 mg/kg in the A431 human epidermoid carcinoma and at 40 mg/kg for the SF767 human glioblastoma and the SKOV3 human ovarian carcinoma. Complete stasis was observed at 40 mg/kg in the BXPC3 human pancreatic carcinoma as well as in the H125 human non-small-cell lung carcinoma.

Synthesis and structural–activity relationships of 3-hydroxyquinazoline-2,4-dione antibacterial agents

A series of 3-hydroxyquinazoline-2,4-diones was synthesized and evaluated for antibacterial activity. This series represents a novel addition to the DNA gyrase inhibitor class of antibacterials. Appropriate substitutions onto the core template yielded compounds with excellent potency against E. coli gyrase and significant in vitro Gram-negative and Gram-positive antibacterial activity.

Gas exchange and lung mechanics during percutaneous transtracheal ventilation in an unparalyzed canine model

OBJECTIVE

To compare the efficacy of percutaneous transtracheal ventilation (PTV) in the unparalyzed state with that in the paralyzed state using a sedated nonobstructed canine model.

METHODS

Eight mongrel dogs (16.8-32 kg) were anesthetized, instrumented, and placed in a volume plethysmograph. Anesthesia was achieved with pentobarbital sodium (up to 30 mg/kg). The spontaneous respiratory drive was kept intact. PTV was performed using a 13-ga transtracheal catheter and compressed air at 45 psi at an I:E ratio of 1:3 (15 breaths/min). Each dog was sequentially ventilated in both the paralyzed and unparalyzed states. The paralyzed/unparalyzed sequence was alternated among the animals to avoid sequence bias. Paralysis was achieved with succinylcholine (0.1 mg/kg bolus and 0.01 mg/kg/min drip). Reversal of paralysis was achieved by discontinuing the succinylcholine infusion. Key variables, including arterial blood gas, tidal volume, and pulmonary mechanics, were measured and compared for the paralyzed and unparalyzed states.

RESULTS

Gas exchanges and lung mechanics were similar between the unparalyzed and paralyzed states. There was no significant difference in mean pH, pCO2, pO2, tidal volume, or peak inspiratory transpulmonary pressure. There was also no significant difference in pulmonary resistance or pulmonary compliance.

CONCLUSION

In a sedated nonobstructed canine model, PTV is as efficacious in the unparalyzed state as it is in the paralyzed state. The lung mechanics are also similar in the 2 states. These data suggest that it may be unnecessary to induce paralysis when using PTV for emergency ventilation in the heavily sedated state.

Response to dopamine vs norepinephrine in tricyclic antidepressant-induced hypotension

OBJECTIVE

To compare the efficacy of dopamine (DA) with that of norepinephrine (NE) in the treatment of refractory hypotension caused by tricyclic antidepressants (TCAs).

METHODS

A retrospective analysis was used to compare blood pressure responses in concurrent case series of patients treated with vasopressors for TCA-associated hypotension. The patients were adults (aged > or = 16 years) treated at 2 urban teaching hospitals from 1983 to 1994. All patients were diagnosed as having TCA ingestion (positive serum toxicologic assay), were hypotensive [systolic blood pressures (SBPs) < or = 90 mm Hg], and required vasopressor therapy. The patients were grouped by initial vasopressor treatment (i.e., NE vs DA).

RESULTS

There were 26 hypotensive adult patients who met study criteria. All 26 patients remained hypotensive after initial treatment of their TCA-associated hypotension with crystalloid infusion and alkalinization. The NE and DA groups were similar in age, sex, and proportion of patients with single and co-drug ingestion. The NE group, however, had a significantly lower average SBP at study entry (56 vs 74 mm Hg, p = 0.04). Nine of 15 (60%) patients responded to DA (5-10 micrograms/kg/min) and 11/11 (100%) patients responded to NE (5-53 micrograms/min). The difference in response rates was statistically significant (p = 0.02). Six patients in whom DA (max rate 10-50 micrograms/min/kg) failed to raise the SBP subsequently responded to NE (max rate 5-74 micrograms/ min) when this drug was later used. One patient receiving NE (12 micrograms/min) developed ventricular ectopy, successfully treated with lidocaine. There were no ischemic complications from either NE or DA. Patients who failed DA therapy tended to be older (39 vs 30 years, p = 0.08), to be more hypotensive at study entry (64 vs 81 mm Hg, p = 0.008), and to remain hypotensive even at higher doses of DA (24 vs 7 micrograms/min/kg, p = 0.002).

CONCLUSION

While this was not a prospective randomized study, NE appears advantageous over DA as the first-line vasopressor agent for those patients who require vasopressor support in the setting of TCA-induced hypotension that is refractory to IV fluid and serum alkalinization.