Novel Multiplexed High Throughput Screening of Selective Inhibitors for Drug-Metabolizing Enzymes Using Human Hepatocytes

Selective chemical inhibitors are critical for reaction phenotyping to identify drug-metabolizing enzymes that are involved in the elimination of drug candidates. Although relatively selective inhibitors are available for the major cytochrome P450 enzymes (CYP), they are quite limited for the less common CYPs and non-CYPs. To address this gap, we developed a multiplexed high throughput screening (HTS) assay using 20 substrate reactions of multiple enzymes to simultaneously monitor the inhibition of enzymes in a 384-well format. Four 384-well assay plates can be run at the same time to maximize throughput. This is the first multiplexed HTS assay for drug-metabolizing enzymes reported. The HTS assay is technologically enabled with state-of-the-art robotic systems and highly sensitive modern LC-MS/MS instrumentation. Virtual screening is utilized to identify inhibitors for HTS based on known inhibitors and enzyme structures. Screening of ~4600 compounds generated many hits for many drug-metabolizing enzymes including the two time-dependent and selective aldehyde oxidase inhibitors, erlotinib and dibenzothiophene. The hit rate is much higher than that for the traditional HTS for biological targets due to the promiscuous nature of the drug-metabolizing enzymes and the biased compound selection process. Future efforts will focus on using this method to identify selective inhibitors for enzymes that do not currently have quality hits and thoroughly characterizing the newly identified selective inhibitors from our screen. We encourage colleagues from other organizations to explore their proprietary libraries using a similar approach to identify better inhibitors that can be used across the industry.

Screening for precancerous anal lesions linked to human papillomaviruses: French recommendations for clinical practice

In France, about 2000 new cases of anal cancer are diagnosed annually. Squamous cell carcinoma is the most common histological type, mostly occurring secondary to persistent HPV16 infection. Invasive cancer is preceded by precancerous lesions. In addition to patients with a personal history of precancerous lesions and anal cancer, three groups are at very high risk of anal cancer: (i) men who have sex with men and are living with HIV, (ii) women with a history of high-grade squamous intraepithelial lesions (HSILs) or vulvar HPV cancer, and (iii) women who received a solid organ transplant more than 10 years ago. The purpose of screening is to detect HSILs so that they can be treated, thereby reducing the risk of progression to cancer. All patients with symptoms should undergo a proctological examination including standard anoscopy. For asymptomatic patients at risk, an initial HPV16 test makes it possible to target patients at risk of HSILs likely to progress to cancer. Anal cytology is a sensitive test for HSIL detection. Its sensitivity is greater than 80% and exceeds that of proctological examination with standard anoscopy. It is indicated in the event of a positive HPV16 test. In the presence of cytological abnormalities and/or lesions and a suspicion of dysplasia on clinical examination, high-resolution anoscopy is indicated. Performance is superior to that of proctological examination with standard anoscopy. However, this technique is not widely available, which limits its use. If high-resolution anoscopy is not possible, screening by a standard proctological examination is an alternative. There is a need to develop high-resolution anoscopy and triage tests and to evaluate screening strategies.

In Vitro-In Vivo Extrapolation and Scaling Factors for Clearance of Human and Preclinical Species with Liver Microsomes and Hepatocytes

In vitro-in vivo extrapolation ((IVIVE) and empirical scaling factors (SF) of human intrinsic clearance (CL_int) were developed using one of the largest dataset of 455 compounds with data from human liver microsomes (HLM) and human hepatocytes (HHEP). For extended clearance classification system (ECCS) class 2/4 compounds, linear SFs (SF_lin) are approximately 1, suggesting enzyme activities in HLM and HHEP are similar to those in vivo under physiological conditions. For ECCS class 1A/1B compounds, a unified set of SFs was developed for CL_int. These SFs contain both SF_lin and an exponential SF (SF_β) of fraction unbound in plasma (f_u,p). The unified SFs for class 1A/1B eliminate the need to identify the transporters involved prior to clearance prediction. The underlying mechanisms of these SFs are not entirely clear at this point, but they serve practical purposes to reduce biases and increase prediction accuracy. Similar SFs have also been developed for preclinical species. For HLM-HHEP disconnect (HLM > HHEP) ECCS class 2/4 compounds that are mainly metabolized by cytochrome P450s/FMO, HLM significantly overpredicted in vivo CL_int, while HHEP slightly underpredicted and geometric mean of HLM and HHEP slightly overpredicted in vivo CL_int. This observation is different than in rats, where rat liver microsomal CL_int correlates well with in vivo CL_int for compounds demonstrating permeability-limited metabolism. The good CL_int IVIVE developed using HLM and HHEP helps build confidence for prospective predictions of human clearance and supports the continued utilization of these assays to guide structure-activity relationships to improve metabolic stability.

An oral SARS-CoV-2 Mpro inhibitor clinical candidate for the treatment of COVID-19

[Figure: see text].

Production of active recombinant human aldehyde oxidase (AOX) in the baculovirus expression vector system (BEVS) and deployment in a pre-clinical fraction-of-control AOX compound exposure assay

Human aldehyde oxidase (AOX) has emerged as a key enzyme activity for consideration in modern drug discovery. The enzyme catalyzes the oxidation of a wide variety of compounds, most notably azaheterocyclics that often form the building blocks of small molecule therapeutics. Failure to consider and assess AOX drug exposure early in the drug development cycle can have catastrophic consequences for novel compounds entering the clinic. AOX is a complex molybdopterin-containing iron-sulfur flavoprotein comprised of two identical 150 kDa subunits that has proven difficult to produce in recombinant form, and a commercial source of the purified human enzyme is currently unavailable. Thus, the potential exposure of novel drug development candidates to human AOX metabolism is usually assessed by using extracts of pooled human liver cytosol as a source of the enzyme. This can complicate the assignment of AOX-specific compound exposure due to its low activity and the presence of contaminating enzymes that may have overlapping substrate specificities. Herein is described a two-step process for the isolation of recombinant human AOX dimers to near homogeneity following production in the baculovirus expression vector system (BEVS). The deployment of this BEVS-produced recombinant human AOX as a substitute for human liver extracts in a fraction-of-control AOX compound-exposure screening assay is described. The ability to generate this key enzyme activity readily in a purified recombinant form provides for a more accurate and convenient approach to the assessment of new compound exposure to bona fide AOX drug metabolism.

Discovery and in Vitro Optimization of 3-Sulfamoylbenzamides as ROMK Inhibitors

Inhibitors of the renal outer medullary potassium channel (ROMK) show promise as novel mechanism diuretics, with potentially lower risk of diuretic-induced hypokalemia relative to current thiazide and loop diuretics. Here, we report the identification of a novel series of 3-sulfamoylbenzamide ROMK inhibitors. Starting from HTS hit 4, this series was optimized to provide ROMK inhibitors with good in vitro potencies and well-balanced ADME profiles. In contrast to previously reported small-molecule ROMK inhibitors, members of this series were demonstrated to be highly selective for inhibition of human over rat ROMK and to be insensitive to the N171D pore mutation that abolishes inhibitory activity of previously reported ROMK inhibitors.

VIIaAT complexes, procoagulant phospholipids, and thrombin generation during postprandial lipemia

INTRODUCTION

Factor VII activation occurs postprandially. A proportion of activated factor VII (VIIa) circulates in complex with antithrombin (VIIaAT). Our primary objective was to assess the effects of postprandial lipemia on circulating VIIaAT, procoagulant phospholipid (PPL) activity, and thrombin generation.

METHODS

Plasma samples from postmyocardial infarction patients (n = 40) and controls (n = 39) were taken before and at 3 and 6 hours during a standardized oral fat tolerance test (OFTT). Fasting PPL activity measurements were also made in a second cohort of 108 postinfarction patients and 109 controls. VIIaAT was analyzed with the Asserachrom VIIaAT ELISA, PPL activity with the STA-Procoag-PPL kit, and thrombin generation with calibrated automated thrombogram with PRP-Reagent as trigger (all Diagnostica Stago products).

RESULTS

Postprandially, VIIaAT increased in all samples without significant case-control differences in the overall response during the OFTT. Thrombin generation measures peak height and velocity, and PPL activity, were marginally affected by the test meal in the controls. Levels of all patient baseline measures were significantly different from controls, indicating a more hypercoagulable state, and these differences were maintained throughout the OFTT. Fasting samples from cases showed higher PPL activity than control samples.

CONCLUSION

Viewing VIIaAT quantitation as a surrogate for TF activity measurement, postprandial increase in VIIaAT may reflect a mechanism that adds to the cardiovascular risk associated with postprandial lipemia. On the other hand, the impact of postprandial lipemia on PPL activity and thrombin generation seems to be minor.

Hyperphosphorylated tau and neurofilament and cytoskeletal disruptions in mice overexpressing human p25, an activator of cdk5

Hyperphosphorylation of microtubule-associated proteins such as tau and neurofilament may underlie the cytoskeletal abnormalities and neuronal death seen in several neurodegenerative diseases including Alzheimer's disease. One potential mechanism of microtubule-associated protein hyperphosphorylation is augmented activity of protein kinases known to associate with microtubules, such as cdk5 or GSK3beta. Here we show that tau and neurofilament are hyperphosphorylated in transgenic mice that overexpress human p25, an activator of cdk5. The p25 transgenic mice display silver-positive neurons using the Bielschowsky stain. Disturbances in neuronal cytoskeletal organization are apparent at the ultrastructural level. These changes are localized predominantly to the amygdala, thalamus/hypothalamus, and cortex. The p25 transgenic mice display increased spontaneous locomotor activity and differences from control in the elevated plus-maze test. The overexpression of an activator of cdk5 in transgenic mice results in increased cdk5 activity that is sufficient to produce hyperphosphorylation of tau and neurofilament as well as cytoskeletal disruptions reminiscent of Alzheimer's disease and other neurodegenerative diseases.