Discovery of Small Molecule Interleukin 17A Inhibitors with Novel Binding Mode and Stoichiometry: Optimization of DNA-Encoded Chemical Library Hits to In Vivo Active Compounds

Dysregulation of IL17A drives numerous inflammatory and autoimmune disorders with inhibition of IL17A using antibodies proven as an effective treatment. Oral anti-IL17 therapies are an attractive alternative option, and several preclinical small molecule IL17 inhibitors have previously been described. Herein, we report the discovery of a novel class of small molecule IL17A inhibitors, identified via a DNA-encoded chemical library screen, and their subsequent optimization to provide in vivo efficacious inhibitors. These new protein-protein interaction (PPI) inhibitors bind in a previously undescribed mode in the IL17A protein with two copies binding symmetrically to the central cavities of the IL17A homodimer.

Development of Orally Efficacious Allosteric Inhibitors of TNFα via Fragment-Based Drug Design

Tumor necrosis factor α (TNFα) is a soluble cytokine that is directly involved in systemic inflammation through the regulation of the intracellular NF-κB and MAPK signaling pathways. The development of biologic drugs that inhibit TNFα has led to improved clinical outcomes for patients with rheumatoid arthritis and other chronic autoimmune diseases; however, TNFα has proven to be difficult to drug with small molecules. Herein, we present a two-phase, fragment-based drug discovery (FBDD) effort in which we first identified isoquinoline fragments that disrupt TNFα ligand-receptor binding through an allosteric desymmetrization mechanism as observed in high-resolution crystal structures. The second phase of discovery focused on the de novo design and optimization of fragments with improved binding efficiency and drug-like properties. The 3-indolinone-based lead presented here displays oral, in vivo efficacy in a mouse glucose-6-phosphate isomerase (GPI)-induced paw swelling model comparable to that seen with a TNFα antibody.

Microphysiological systems for ADME-related applications: current status and recommendations for system development and characterization

Over the last decade, progress has been made on the development of microphysiological systems (MPS) for absorption, distribution, metabolism, and excretion (ADME) applications. Central to this progress has been proof of concept data generated by academic and industrial institutions followed by broader characterization studies, which provide evidence for scalability and applicability to drug discovery and development. In this review, we describe some of the advances made for specific tissue MPS and outline the desired functionality for such systems, which are likely to make them applicable for practical use in the pharmaceutical industry. Single organ MPS platforms will be valuable for modelling tissue-specific functions. However, dynamic organ crosstalk, especially in the context of disease or toxicity, can only be obtained with the use of inter-linked MPS models which will enable scientists to address questions at the intersection of pharmacokinetics (PK) and efficacy, or PK and toxicity. In the future, successful application of MPS platforms that closely mimic human physiology may ultimately reduce the need for animal models to predict ADME outcomes and decrease the overall risk and cost associated with drug development.

Navigating tissue chips from development to dissemination: A pharmaceutical industry perspective

Tissue chips are poised to deliver a paradigm shift in drug discovery. By emulating human physiology, these chips have the potential to increase the predictive power of preclinical modeling, which in turn will move the pharmaceutical industry closer to its aspiration of clinically relevant and ultimately animal-free drug discovery. Despite the tremendous science and innovation invested in these tissue chips, significant challenges remain to be addressed to enable their routine adoption into the industrial laboratory. This article describes the main steps that need to be taken and highlights key considerations in order to transform tissue chip technology from the hands of the innovators into those of the industrial scientists. Written by scientists from 13 pharmaceutical companies and partners at the National Institutes of Health, this article uniquely captures a consensus view on the progression strategy to facilitate and accelerate the adoption of this valuable technology. It concludes that success will be delivered by a partnership approach as well as a deep understanding of the context within which these chips will actually be used. Impact statement The rapid pace of scientific innovation in the tissue chip (TC) field requires a cohesive partnership between innovators and end users. Near term uptake of these human-relevant platforms will fill gaps in current capabilities for assessing important properties of disposition, efficacy and safety liabilities. Similarly, these platforms could support mechanistic studies which aim to resolve challenges later in development (e.g. assessing the human relevance of a liability identified in animal studies). Building confidence that novel capabilities of TCs can address real world challenges while they themselves are being developed will accelerate their application in the discovery and development of innovative medicines. This article outlines a strategic roadmap to unite innovators and end users thus making implementation smooth and rapid. With the collective contributions from multiple international pharmaceutical companies and partners at National Institutes of Health, this article should serve as an invaluable resource to the multi-disciplinary field of TC development.

Synthesis and optimization of furano[3,2-d]pyrimidines as selective spleen tyrosine kinase (Syk) inhibitors

A series of furano[3,2-d]pyrimidine Syk inhibitors were synthesized and optimized for their enzyme potency and selectivity versus other kinases. In addition, ADME properties were assessed and compounds were prepared with optimized profiles for in vivo experiments. Compound 23 was identified as having acceptable pharmacokinetic properties and demonstrated efficacy in a rat collagen induced arthritis model.

Sphingosine-1-Phosphate (S1P) Lyase Inhibition Causes Increased Cardiac S1P Levels and Bradycardia in Rats

Inhibition of the sphingosine-1-phosphate (S1P)-catabolizing enzyme S1P lyase (S1PL) elevates the native ligand of S1P receptors and provides an alternative mechanism for immune suppression to synthetic S1P receptor agonists. S1PL inhibition is reported to preferentially elevate S1P in lymphoid organs. Tissue selectivity could potentially differentiate S1PL inhibitors from S1P receptor agonists, the use of which also results in bradycardia, atrioventricular block, and hypertension. But it is unknown if S1PL inhibition would also modulate cardiac S1P levels or cardiovascular function. The S1PL inhibitor 6-[(2R)-4-(4-benzyl-7-chlorophthalazin-1-yl)-2-methylpiperazin-1-yl]pyridine-3-carbonitrile was used to determine the relationship in rats between drug concentration, S1P levels in select tissues, and circulating lymphocytes. Repeated oral doses of the S1PL inhibitor fully depleted circulating lymphocytes after 3 to 4 days of treatment in rats. Full lymphopenia corresponded to increased levels of S1P of 100- to 1000-fold in lymph nodes, 3-fold in blood (but with no change in plasma), and 9-fold in cardiac tissue. Repeated oral dosing of the S1PL inhibitor in telemeterized, conscious rats resulted in significant bradycardia within 48 hours of drug treatment, comparable in magnitude to the bradycardia induced by 3 mg/kg fingolimod. These results suggest that S1PL inhibition modulates cardiac function and does not provide immune suppression with an improved cardiovascular safety profile over fingolimod in rats.

pH-sensitive interaction of HMG-CoA reductase inhibitors (statins) with organic anion transporting polypeptide 2B1

The human organic anion transporting polypeptide 2B1 (OATP2B1, SLCO2B1) is ubiquitously expressed and may play an important role in the disposition of xenobiotics. The present study aimed to examine the role of OATP2B1 in the intestinal absorption and tissue uptake of 3-hydroxy-3-methylglutaryl-Coenzyme A (HMG-CoA) reductase inhibitors (statins). We first investigated the functional affinity of statins to the transporter as a function of extracellular pH, using OATP2B1-transfeced HEK293 cells. The results indicate that OATP2B1-mediated transport is significant for rosuvastatin, fluvastatin and atorvastatin, at neutral pH. However, OATP2B1 showed broader substrate specificity as well as enhanced transporter activity at acidic pH. Furthermore, uptake at acidic pH was diminished in the presence of proton ionophore, suggesting proton gradient as the driving force for OATP2B1 activity. Notably, passive transport rates are predominant or comparable to active transport rates for statins, except for rosuvastatin and fluvastatin. Second, we studied the effect of OATP modulators on statin uptake. At pH 6.0, OATP2B1-mediated transport of atorvastatin and cerivastatin was not inhibitable, while rosuvastatin transport was inhibited by E-3-S, rifamycin SV and cyclosporine with IC(50) values of 19.7 ± 3.3 μM, 0.53 ± 0.2 μM and 2.2 ± 0.4 μM, respectively. Rifamycin SV inhibited OATP2B1-mediated transport of E-3-S and rosuvastatin with similar IC(50) values at pH 6.0 and 7.4, suggesting that the inhibitor affinity is not pH-dependent. Finally, we noted that OATP2B1-mediated transport of E-3-S, but not rosuvastatin, is pH sensitive in intestinal epithelial (Caco-2) cells. However, uptake of E-3-S and rosuvastatin by Caco-2 cells was diminished in the presence of proton ionophore. The present results indicate that OATP2B1 may be involved in the tissue uptake of rosuvastatin and fluvastatin, while OATP2B1 may play a significant role in the intestinal absorption of several statins due to their transporter affinity at acidic pH.

Prediction of biliary excretion in rats and humans using molecular weight and quantitative structure-pharmacokinetic relationships

The aims were (1) to evaluate the molecular weight (MW) dependence of biliary excretion and (2) to develop quantitative structure-pharmacokinetic relationships (QSPKR) to predict biliary clearance (CL(b)) and percentage of administered dose excreted in bile as parent drug (PD(b)) in rats and humans. CL(b) and PD(b) data were collected from the literature for rats and humans. Receiver operating characteristic curve analysis was utilized to determine whether a MW threshold exists for PD(b). Stepwise multiple linear regression (MLR) was used to derive QSPKR models. The predictive performance of the models was evaluated by internal validation using the leave-one-out method and external test groups. A MW threshold of 400 Da was determined for PD(b) for anions in rats, while 475 Da was the cutoff for anions in humans. MW thresholds were not present for cations or cations/neutral compounds in either rats or humans. The QSPKR model for human CL(b) showed a significant correlation (R (2) = 0.819) with good prediction performance (Q (2) = 0.722). The model was further assessed using a test group, yielding a geometric mean fold-error of 2.68. QSPKR models with significant correlation and good predictability were also developed for CL(b) in rats and PD(b) data for anions or cation/neutral compounds in rats and humans. Both CL(b) and PD(b) data were further evaluated for subsets of MRP2 or P-glycoprotein substrates, and significant relationships were derived. QSPKR models were successfully developed for biliary excretion of non-congeneric compounds in rats and humans, providing a quantitative prediction of biliary clearance of compounds.

Role of transporters in the disposition of the selective phosphodiesterase-4 inhibitor (+)-2-[4-({[2-(benzo[1,3]dioxol-5-yloxy)-pyridine-3-carbonyl]-amino}-methyl)-3-fluoro-phenoxy]-propionic acid in rat and human

The role of transporters in the disposition of (+)-2-[4-({[2-(benzo[1,3]dioxol-5-yloxy)-pyridine-3-carbonyl]-amino}-methyl)-3-fluoro-phenoxy]-propionic acid (CP-671,305), an orally active inhibitor of phosphodiesterase-4, was examined. In bile duct-exteriorized rats, a 7.4-fold decrease in the half-life of CP-671,305 was observed, implicating enterohepatic recirculation. Statistically significant differences in CP-671,305 pharmacokinetics (clearance and area under the curve) were discernible in cyclosporin A- or rifampicin-pretreated rats. Considering that cyclosporin A and rifampicin inhibit multiple uptake/efflux transporters, the interactions of CP-671,305 with major human hepatic drug transporters, multidrug resistance protein 1 (MDR1), multidrug resistance-associated protein 2 (MRP2), breast cancer resistant protein (BCRP), and organic anion-transporting polypeptide (OATPs) were evaluated in vitro. CP-671,305 was identified as a substrate of MRP2 and BCRP, but not MDR1. CP-671,305 was a substrate of human OATP2B1 with a high affinity (Km = 4 microM) but not a substrate for human OATP1B1 or OATP1B3. Consistent with these results, examination of hepatobiliary transport of CP-671,305 in hepatocytes indicated active uptake followed by efflux into bile canaliculi. Upon examination as a substrate for major rat hepatic Oatps, CP-671,305 displayed high affinity (Km = 12 microM) for Oatp1a4. The role of rat Mrp2 in the biliary excretion was also examined in Mrp2-deficient rats. The observations that CP-671,305 pharmacokinetics were largely unaltered suggested that compromised biliary clearance of CP-671,305 was compensated by increased urinary clearance. Overall, these studies suggest that hepatic transporters play an important role in the disposition and clearance of CP-671,305 in rat and human, and as such, these studies should aid in the design of clinical drug-drug interaction studies.

Use of cryopreserved human hepatocytes in sandwich culture to measure hepatobiliary transport

Fresh hepatocytes cultured in a sandwich configuration allow for the development of intact bile canaliculi and the ability to measure hepatic uptake and biliary clearance. A disadvantage of this model is its dependence upon hepatocytes from fresh tissue. Therefore, the ability to use cryopreserved human hepatocytes in this model would be a great advantage. Multiple variables were tested, and the recommended conditions for culturing cryopreserved human hepatocytes in a sandwich configuration in 24-well plates are as follows: BioCoat plates, a cell density of 0.35 x 10(6) cells/well in 500 microl, an overlay of Matrigel and InVitroGRO media. These conditions resulted in good hepatocyte morphology and the formation of distinct bile canaliculi. The function of multiple uptake and efflux transporters was tested in multiple lots of cryopreserved and fresh human hepatocytes. For taurocholate [Na+ taurocholate cotransporting polypeptide/organic anion transporting polypeptide (OATP) uptake/bile salt export pump efflux], the average apparent uptake, apparent intrinsic biliary clearance, and biliary excretion index among five cryopreserved hepatocyte lots was high, ranging from 11 to 17 pmol/min/mg protein, 5.8 to 10 microl/min/mg protein, and 41 to 63%, respectively. The corresponding values for digoxin (OATP-8 uptake/multidrug resistance protein 1 efflux) were 0.69 to 1.5 pmol/min/mg protein, 0.60 to 1.5 microl/min/mg protein, and 37 to 63%. Both substrates exhibited similar results when fresh human hepatocytes were used. In addition, substrates of breast cancer resistance protein and multidrug resistance-associated protein 2 were also tested in this model, and all cryopreserved lots showed functional transport of these substrates. The use of cryopreserved human hepatocytes in 24-well sandwich culture to form intact bile canaliculi and to exhibit functional uptake and efflux transport has been successfully demonstrated.

A 96-well efflux assay to identify ABCG2 substrates using a stably transfected MDCK II cell line

Human ABCG2 (breast cancer resistance protein, BCRP) is an important efflux transporter which exhibits broad substrate specificity and which is found in many tissues. The purpose of the present study was to develop a 96-Transwell assay using an MDCK II cell line stably transfected with ABCG2 (MDCK II/ABCG2) to identify ABCG2 substrates. In this assay, which also incorporates a high throughput mass spectrometry method for quantification, efflux activity of the MDCK II/ABCG2 cells was evaluated by monitoring the basolateral-to-apical/ apical-to-basolateral (B to A/A to B) efflux ratio of several substrates. Mean MDCK II/ABGC2 efflux ratios for 2 microM prazosin, SN-38, and Cl 033 were 2.8, 7.6, and 2.4, respectively, and the mean efflux ratio for 10 microM mitoxantrone was 5.0. Interday variability of the assay was low (CV = 10-29% for control compounds at 2 microM). Our data indicate that a compound tested at 2 microM can be considered a substrate of ABCG2 if its ratio of ratios (MDCK II/ABCG2 efflux ratio)/ (MDCK II efflux ratio) is > 1.2. This assay provides an efficient, high throughput means to identify ABCG2 substrates in drug discovery.

Expression and characterization of canine cytochrome P450 2D15

CYP2D15 is the canine ortholog of human CYP2D6, the human CYP2D isoform involved in the metabolism of drugs such as antiarhythmics, adrenoceptor antagonists, and tricyclic antidepressants. Similar to human, canine CYP2D15 is expressed in the liver, with detectable levels in several other tissues. Three different CYP2D15 cDNA clones were obtained by RT-PCR from dog liver RNA. Two clones corresponded to variant full-length CYP2D15 cDNAs (termed CYP2D15 WT2 and CYP2D15 V1); the third was identified as a splicing variant missing exon 3 (termed CYP2D15 V2). Recombinant baculoviruses were constructed containing full-length cDNAs and used to express CYP2D15 WT2 and CYP2D15 V1 in Spodoptera frugiperda (Sf9) cells with expression levels of up to 0.14 nmol/mg cell protein. As with human CYP2D6, the recombinant CYP2D15 enzymes exhibited bufuralol 1'-hydroxylaseand dextromethorphan O-demethylase activities whencoexpressed with rabbit NADPH:P450 oxidoreductase. For bufuralol 1'-hydroxylase, apparent Km values were 4.9, 3.7, and 2.5 microM and the Vmax values were 0.14, 0.034, and 0.60 nmol/min/mg protein for dog liver microsomes, CYP2D15 WT2, and the variant CYP2D15 V1, respectively. For dextromethorphan O-demethylase, apparent Km values were 0.6, 0.6, and 2.0 microM and the Vmax values were 0.18, 0.034, and 0.057 nmol/min/mg protein for dog liver microsomes, CYP2D15 WT2, and the variant CYP2D15 V1, respectively. The human CYP2D6-specific inhibitor quinidine and the rat CYP2D1-specific inhibitor quinine were both shown to be inhibitors of bufuralol 1'-hydroxylase activity for dog liver microsomes, CYP2D15 WT2, and the CYP2D15 V1 variant with nearly equal potency. Thus, the dog expresses a CYP2D ortholog possessing enzymatic activities similar to human CYP2D6, but is affected by the inhibitors quinine and quinidine in a manner closer to that of rat CYP2D1.

Synthesis, SAR and pharmacology of CP-293,019: a potent, selective dopamine D4 receptor antagonist

A series of novel, potent and selective pyrido[1,2-a]pyrazine dopamine D4 receptor antagonists are reported including CP-293,019 (D4 Ki = 3.4 nM, D2 Ki > 3,310 nM), which also inhibits apomorphine-induced hyperlocomotion in rats after oral dosing.

The metabolism of xenobiotics and endogenous compounds by the constitutive dog liver cytochrome P450 PBD-2

We have investigated the metabolism of polychlorinated biphenyls and endogenous steroids by the major phenobarbital (PB)-inducible hepatic cytochromes P450 in dogs and rats, PBD-2 and PB-B, respectively. Previous results from our laboratory indicate that dog PBD-2 purified from microsomes of PB-treated animals is similar to rat PB-B with respect to structure and the regioselective metabolism of warfarin and androstenedione. The results also strongly suggest that PBD-2 is the P450 form responsible for metabolizing 2,2',4,4',5,5'-hexachlorobiphenyl (245-HCB) in liver microsomes from untreated dogs. In the present study, a cytochrome P450 with similar chromatographic behavior to that of PBD-2 has been purified from liver microsomes of untreated dogs. This protein is identical to PBD-2 based on (i) mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, (ii) reactivity with anti-PBD-2 IgG, (iii) amino-terminal sequence, and (iv) 245-HCB metabolite profile. Induction and antibody-inhibition data suggest that PBD-2 is responsible for the metabolism of 2,2',3,3',6,6'-hexachlorobiphenyl (236-HCB) in microsomes obtained from both untreated and PB-treated dogs. In contrast, metabolism of 4,4'-dichlorobiphenyl (4-DCB) by dog microsomes is poor, and does not appear to be catalyzed to a significant extent by PBD-2. Antibody-inhibition studies with intact microsomes corroborate previous results that androstenedione is metabolized by purified PBD-2 to the same major metabolite (16 beta-OH androstenedione) produced by rat PB-B. Dog PBD-2 metabolizes progesterone primarily to the 21-OH metabolite, while metabolism by rat PB-B leads to the formation of the 16 alpha-OH product. On the other hand, upon Ouchterlony double-immunodiffusion analysis, anti-PBD-2 IgG reacts strongly with PB-B but not PB-C, the major rat liver progesterone 21-hydroxylase. The data suggest that dog PBD-2 is a constitutive P450 important in the metabolism of various PCBs and endogenous steroids. Dog PBD-2 and rat PB-B appear to be similar enzymes, yet they differ in their regioselective metabolism of progesterone.

Selective inactivation by chloramphenicol of the major phenobarbital-inducible isozyme of dog liver cytochrome P-450

Chloramphenicol (CAP) is a potent and effective mechanism-based inactivator of the major phenobarbital (PB)-inducible isozyme of dog liver cytochrome P-450 (PBD-2) in vitro. In a reconstituted system containing PBD-2, CAP causes a time- and NADPH-dependent irreversible loss of 7-ethoxycoumarin deethylase activity, with no loss of spectrally detectable cytochrome P-450. Inactivation is enhanced by cytochrome b5, and, in the presence of cytochrome b5, the concentration of CAP at which the rate constant for inactivation is half-maximal (Kl) and the maximal rate constant for inactivation (Kinact) are 5 microM and 1.2 min-1, respectively. CAP binds covalently to PBD-2 with a stoichiometry of 1 nmol of [14C]CAP bound/nmol of cytochrome P-450 inactivated. In addition, CAP is a selective inactivator of PBD-2. In intact liver microsomes from PB-treated dogs, CAP irreversibly inhibits androstenedione 16 alpha and 16 beta, but not 6 beta hydroxylation. Covalent binding of [14C]CAP to dog liver microsomes in vitro is increased 5.5 times by PB induction. This increase correlates well with the increased levels of immunochemically determined PBD-2 (5.8-fold) and 16 alpha and 16 beta hydroxylation of androstenedione (5.7- and 5.8-fold) in microsomes from PB-treated compared to control animals. Anti-PBD-2 IgG specifically inhibits by greater than 80% the covalent binding of [14C]CAP to microsomes from control and PB-treated dogs. Finally, in liver microsomes from PB-treated and control dogs, CAP appears to bind covalently to a single protein with the same molecular weight as PBD-2 as evidenced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography.

Purification and characterization of the dog hepatic cytochrome P-450 isozyme responsible for the metabolism of 2,2',4,4',5,5'-hexachlorobiphenyl

The biochemical basis for the marked difference in the rate of the hepatic metabolism of 2,2',4,4',5,5'-hexachlorobiphenyl (245-HCB) by Beagle dogs and Sprague-Dawley rats has been investigated. Control dog liver microsomes metabolize this substrate 15 times faster than control rat liver microsomes. Upon treatment with phenobarbital (PB), at least two cytochrome P-450 isozymes are induced in the dog, and the hepatic microsomal metabolism of 245-HCB is increased on both a per nanomole P-450 basis (twofold) and a per milligram protein basis (fivefold). One of the PB-induced isozymes, PBD-2, has been purified to a specific content of 17-19 nmol/mg protein and to less than 95% homogeneity, as evidenced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In a reconstituted system containing cytochrome b5, this isozyme shows an activity toward 245-HCB which is greater than threefold that seen in intact liver microsomes from PB-induced dogs. A reconstituted system containing the major isozyme induced by PB in the rat (PB-B) metabolizes 245-HCB at 1/10 the rate observed with purified PBD-2. Antibody inhibition studies have shown that PBD-2 accounts for greater than 90% of the hepatic microsomal metabolism of 245-HCB in control and PB-induced dogs, while PB-B only accounts for about half of the metabolism of this compound by microsomes obtained from PB-treated rats. Immunoblot analysis has revealed that the level of PBD-2 in dog liver microsomes increases nearly sixfold with PB treatment, and this increase correlates well with the fivefold increase in the rate of hepatic microsomal metabolism of 245-HCB by dogs. Together these data support a primary role for isozyme PBD-2 in the hepatic metabolism of 245-HCB in control and PB-induced dogs. In addition, these results suggest that, in contrast to rats, dogs can readily metabolize 245-HCB as a result of the presence of a cytochrome P-450 isozyme with efficient 245-HCB metabolizing activity.