Drug-drug Interactions In Humans Research Articles

Discovery of Nelutroctiv (CK-136), a Selective Cardiac Troponin Activator for the Treatment of Cardiovascular Diseases Associated with Reduced Cardiac Contractility.

Cardiac myosin activation has been shown to be a viable approach for the treatment of heart failure with reduced ejection fraction. Here, we report the discovery of nelutroctiv (CK-136), a selective cardiac troponin activator intended for patients with cardiovascular conditions where cardiac contractility is reduced. Discovery of nelutroctiv began with a high-throughput screen that identified compound 1R, a muscle selective cardiac sarcomere activator devoid of phosphodiesterase-3 activity. Optimization of druglike properties for 1R led to the replacement of the sulfonamide and aniline substituents which resulted in improved pharmacokinetic (PK) profiles and a reduced potential for human drug-drug interactions. In vivo echocardiography assessment of the optimized leads showed concentration dependent increases in fractional shortening and an improved pharmacodynamic window compared to myosin activator CK-138. Overall, nelutroctiv was found to possess the desired selectivity, a favorable pharmacodynamic window relative to myosin activators, and a preclinical PK profile to support clinical development.

Inhibitory Effects of Tricyclic Antidepressants on Human Liver Microsomal Morphine Glucuronidation: Application of IVIVE to Predict Potential Drug-Drug Interactions in Humans.

Tricyclic antidepressants (TCAs) are commonly co-administered with morphine as an adjuvant analgesic. Nevertheless, there remains a lack of information concerning metabolic drug-drug interactions (DDIs) resulting from TCA inhibition on morphine glucuronidation. This study aimed to (i) examine the inhibitory effects of TCAs (viz., amitriptyline, clomipramine, imipramine, and nortriptyline) on human liver microsomal morphine 3- and 6-glucuronidation and (ii) evaluate the potential of DDI in humans by employing in vitro-in vivo extrapolation (IVIVE) approaches. The inhibition parameters for TCA inhibition on morphine glucuronidation were derived from the in vitro system containing 2% BSA. The Ki values were employed to predict the DDI magnitude in vivo by using static and dynamic mechanistic PBPK approaches Results: TCAs moderately inhibited human liver microsomal morphine glucuronidation, with clomipramine exhibiting the most potent inhibition potency. Amitriptyline, clomipramine, imipramine, and nortriptyline competitively inhibited morphine 3- and 6-glucuronide formation with the respective Ki values of 91 ± 7.5 and 82 ± 11 μM, 23 ± 1.3 and 14 ± 0.7 μM, 103 ± 5 and 90 ± 7 μM, and 115 ± 5 and 110 ± 3 μM. Employing the static mechanistic IVIVE, a prediction showed an estimated 20% elevation in the morphine AUC when co-administered with either clomipramine or imipramine, whereas the predicted increase was <5% for amitriptyline or nortriptyline. PBPK modelling predicted an increase of less than 10% in the morphine AUC due to the inhibition of clomipramine and imipramine in both virtual healthy and cirrhotic populations. The results suggest that the likelihood of potential clinical DDIs arising from tricyclic antidepressant inhibition on morphine glucuronidation is low.

Quantitative prediction of CYP3A-mediated drug-drug interactions by correctly estimating fraction metabolized using human liver chimeric mice.

Fraction metabolized (fm ) and fraction transported (ft ) are important for understanding drug-drug interactions (DDIs) in drug discovery and development. However, current in vitro systems cannot accurately estimate in vivo fm due to inability to reflect the ft by efflux transporters (ft,efflux ). This study demonstrates how CYP3A-mediated DDI for CYP3A/P-gp substrates can be predicted using Hu-PXB mice as human liver chimeric mice. For estimating human in vitro fm by CYP3A enzyme (fm,CYP3A,in vitro ), six drugs, including CYP3A/P-gp substrates (alprazolam, cyclosporine, docetaxel, midazolam, prednisolone, and theophylline) and human hepatocytes were incubated with or without ketoconazole as a CYP3A inhibitor. We calculated fm,CYP3A,in vitro based on hepatic intrinsic clearance. To estimate human in vivo fm,CYP3A (fm,CYP3A,in vivo ), we collected information on clinical DDI caused by ketoconazole for these six drugs. We calculated fm,CYP3A,in vivo using the change of total clearance (CLtotal ). For evaluating the human DDI predictability, the six drugs were administered intravenously to Hu-PXB and SCID mice with or without ketoconazole. We calculated the change of CLtotal caused by ketoconazole. We compared the CLtotal change in humans with that in Hu-PXB and SCID mice. The fm,CYP3A,in vitro was overestimated compared to the fm,CYP3A,in vivo . Hu-PXB mice showed much better correlation in the change of CLtotal with humans (R2 = 0.95) compared to SCID mice (R2 = 0.0058). CYP3A-mediated DDI can be predicted by correctly estimating human fm,CYP3A,in vivo using Hu-PXB mice. These mice could be useful predicting hepatic fm and ft,efflux .

Differential Preincubation Effects of Nicardipine on OATP1B1- and OATP1B3-Mediated Transport in the Presence and Absence of Protein: Implications in Assessing OATP1B1- and OATP1B3-Mediated Drug-Drug Interactions.

Impaired transport activity of hepatic OATP1B1 and OATP1B3 due to drug-drug interactions (DDIs) often leads to increased systemic exposure to substrate drugs (e.g., lipid-lowering statins). Since dyslipidemia and hypertension frequently coexist, statins are often concurrently used with antihypertensives, including calcium channel blockers (CCBs). OATP1B1/1B3-related DDIs in humans have been reported for several CCBs. To date, the OATP1B1/1B3-mediated DDI potential of CCB nicardipine has not been assessed. The current study was designed to assess the OATP1B1- and OATP1B3-mediated DDI potential of nicardipine using the R-value model, following the US-FDA guidance. IC50 values of nicardipine against OATP1B1 and OATP1B3 were determined in transporter-overexpressing human embryonic kidney 293 cells using [3H]-estradiol 17β-D-glucuronide and [3H]-cholecystokinin-8 as substrates, respectively, with or without nicardipine-preincubation in protein-free Hanks' Balanced Salt Solution (HBSS) or in fetal bovine serum (FBS)-containing culture medium. Preincubation with nicardipine for 30 min in protein-free HBSS buffer produced lower IC50 and higher R-values for both OATP1B1 and OATP1B3 compared to in FBS-containing medium, yielding IC50 values of 0.98 and 1.63 µM and R-values of 1.4 and 1.3 for OATP1B1 and OATP1B3, respectively. The R-values were higher than the US-FDA cut-off value of 1.1, supporting that nicardipine has the potential to cause OATP1B1/3-mediated DDIs. Current studies provide insight into the consideration of optimal preincubation conditions when assessing the OATP1B1/3-mediated DDIs in vitro.

Novel inhibitors of breast cancer resistance protein (BCRP, ABCG2) among marketed drugs

Drug-drug interactions (DDIs) are a major concern for the safe use of medications. Breast cancer resistance protein (BCRP) is a clinically relevant ATP-binding cassette (ABC) transporter for drug disposition. Inhibition of BCRP increases the plasma concentrations of BCRP substrate drugs, which potentially could lead to adverse drug reactions. The aim of the present study was to identify BCRP inhibitors amongst a library of 232 commonly used drugs and anticancer drugs approved by the United States Food and Drug Administration (FDA). BCRP inhibition studies were carried out using the vesicular transport assay. We found 75 drugs that reduced the relative transport activity of BCRP to less than 25% of the vehicle control and were categorized as strong inhibitors. The concentration required for 50% inhibition (IC50) was determined for 13 strong inhibitors that were previously poorly characterized for BCRP inhibition. The IC50 ranged from 1.1 to 11 µM, with vemurafenib, dabigatran etexilate and everolimus being the strongest inhibitors. According to the drug interaction guidance documents from the FDA and the European Medicines Agency (EMA), in vivo DDI studies are warranted if the theoretical intestinal luminal concentration of a drug exceeds its IC50 by tenfold. Here, the IC50 values for eight of the drugs were 100-fold lower than their theoretical intestinal luminal concentration. Moreover, a mechanistic static model suggested that vemurafenib, bexarotene, dabigatran etexilate, rifapentine, aprepitant, and ivacaftor could almost fully inhibit intestinal BCRP, increasing the exposure of concomitantly administered rosuvastatin over 90%. Therefore, clinical studies are warranted to investigate whether these drugs cause BCRP-mediated DDIs in humans.

The next frontier in ADME science: Predicting transporter-based drug disposition, tissue concentrations and drug-drug interactions in humans

The next frontier in ADME science: Predicting transporter-based drug disposition, tissue concentrations and drug-drug interactions in humans

The Next Frontier in ADME Science: Predicting Transporter-Based Drug Disposition, Tissue Concentrations and Drug-Drug Interactions in Humans

The Next Frontier in ADME Science: Predicting Transporter-Based Drug Disposition, Tissue Concentrations and Drug-Drug Interactions in Humans

Abstract 1282: IND-enabling characterization of the selective GPER agonist, LNS8801

Abstract LNS8801 is the first-in-class, small molecule, orally bioavailable, agonist of GPER being developed for the treatment of patients with advanced cancer. LNS8801 is highly selective for GPER over the classical nuclear hormone estrogen receptors α and β, and it was also highly selective for GPER in Eurofins' Safety47 panel. LNS8801 has very low aqueous solubility and is highly protein bound. Pharmacokinetic studies demonstrate that LNS8801 has high clearance and moderate, solubility-dependent, oral bioavailability. The rank ordering of metabolic liability in hepatocytes is dog&amp;lt;human&amp;lt;mouse&amp;lt;rat, which is consistent with the observed clearance rates in these species. LNS8801 metabolism, and thus clearance, is slower in dogs. Oral bioavailability is ~80% and dose proportional in human formulations tested in dogs. LNS8801 is primarily metabolized by oxidation followed by phase II conjugation. In vitro metabolism studies indicate that LNS8801 is a potential substrate for several cytochrome P450 enzymes and thus has a low potential for participating in drug-drug interactions (DDIs). Given that maximal efficacy is expected at low exposures (Cmax of ≤5 nM) and that LNS8801 is highly protein bound, it is unlikely that these effects will cause adverse DDIs in humans. In the pivotal 28-day toxicity studies, the no-observed-adverse-effect level (NOAEL) was &amp;gt;1000 mg/kg/day (the maximum feasible dose) in the rat and 30 mg/kg/day in the dog. Exposure was higher in dogs than in rats due to considerable accumulation. In the dog, mortality at doses that gave very high exposures was attributed to myelopoietic hypocellularity of the bone marrow and subsequent lymphoid depletion in associated organs. The primary target organs were identified as bone marrow, lymphoid tissues, and reproductive organs. Exposure at the canine NOAEL was more than 24,000 times the predicted maximally efficacious exposure in humans, and thus LNS8801 is anticipated to be very safe. Citation Format: Chris Natale, Tina Garyantes. IND-enabling characterization of the selective GPER agonist, LNS8801 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1282.

Assessment of the Potential for Veverimer Drug-Drug Interactions.

Veverimer is a polymer being developed as a potential treatment of metabolic acidosis in patients with chronic kidney disease. Veverimer selectively binds and removes hydrochloric acid from the gastrointestinal tract, resulting in an increase in serum bicarbonate. Veverimer is not systemically absorbed, so potential drug-drug interactions (DDIs) are limited to effects on the absorption of other oral drugs through binding to veverimer in the gastrointestinal tract or increases in gastric pH caused by veverimer binding to hydrochloric acid. In in vitro binding experiments using a panel of 16 test drugs, no positively charged, neutral, or zwitterionic drugs bound to veverimer. Three negatively charged drugs (furosemide, aspirin, ethacrynic acid) bound to veverimer; however, this binding was reduced or eliminated in the presence of normal physiologic concentrations (100-170 mM) of chloride. Veverimer increased gastric pH in vivo by 1.5-3 pH units. This pH elevation peaked within 1 hour and had returned to baseline after 1.5-3 hours. Omeprazole did not alter the effect of veverimer on gastric pH. The clinical relevance of in vitro binding and the transient increase in gastric pH was evaluated in human DDI studies using two drugs with the most binding to veverimer (furosemide, aspirin) and two additional drugs with pH-dependent solubility effecting absorption (dabigatran, warfarin). None of the four drugs showed clinically meaningful DDI with veverimer in human studies. Based on the physicochemical characteristics of veverimer and results from in vitro and human studies, veverimer is unlikely to have significant DDIs. SIGNIFICANCE STATEMENT: Patients with chronic kidney disease, who are usually on many drugs, are vulnerable to drug-drug interactions (DDIs). The potential for DDIs with veverimer was evaluated based on the known site of action and physicochemical structure of the polymer, which restricts the compound to the gastrointestinal tract. Based on the findings from in vitro and human studies, we conclude that veverimer is unlikely to have clinically significant DDIs.

Species differences in the drug–drug interaction between atorvastatin and cyclosporine: In vivo study using a stable isotope-IV method in rats and dogs

In this study, drug-drug interaction (DDI) between atorvastatin (ATV) and cyclosporine (CsA) was kinetically analyzed using a stable isotope-IV method in rats and dogs. Obtained results were compared with the clinical data quoted from literatures to clarify the species difference in DDI both qualitatively and quantitatively. ATV only or ATV with CsA was orally administered to rats or dogs, and at 90 minutes after administration, a small amount of deuterium labeled ATV (ATV-d5) was intravenously injected. Assuming that ATV-d5 exhibits the same pharmacokinetic (PK) profile with ATV, PK parameters for absorption and elimination of ATV were calculated. Plasma levels of orally administered ATV were significantly enhanced by co-administration of CsA both in rats, dogs and humans, resulted in 9.8, 31, and 8.7-fold increase in systemic exposure calculated as AUCpo. High intensity of the DDI in dogs was mainly attributed to the marked decrease of the intrinsic hepatic clearance (to 1/10 of the control), which was induced by the inhibition of hepatic uptake of ATV via organic anion transporting polypeptide 1B1 (OATP1B1). CsA also affected the absorption of ATV form GI tract. Absorbed fraction of ATV into portal vein (calculated as Fa*Fg) was increased almost same extent in rats and dogs (around 3.0-fold) by co-administration of CsA. Inhibition of efflux transport via breast cancer resistance protein as well as the intestinal metabolism mediated by CYP enzymes contributed to the DDI occurred in the intestinal tract. In conclusion, PK analysis on the DDI between ATV and CsA in rats and dogs clearly demonstarted the factors to cause species differences in the extent of DDI. This type of quantitative analysis of DDIs in both small and large animals can be a great help to predict the extent of DDI in humans in the clinical study.

P0009EVALUATION OF THE POTENTIAL FOR DRUG INTERACTIONS WITH VEVERIMER

Abstract Background and Aims Veverimer is an investigational drug being developed as an orally administered hydrochloric acid binder for the treatment of metabolic acidosis associated with chronic kidney disease (CKD). In clinical studies, treatment with veverimer safely and effectively increased serum bicarbonate and improved objective and subjective measures of physical functioning1-3. Veverimer, a free-amine polymer, is not systemically absorbed; therefore, its potential for drug-drug interactions (DDIs) is limited to those that occur in the gastrointestinal (GI) tract (i.e., direct binding or indirect effects resulting from transient increases in gastric pH). We assessed the potential for DDIs with veverimer both in vitro and in vivo in healthy subjects. Methods In vitro binding to veverimer was evaluated with 16 drugs of varying molecular weight and charge. In a separate study, the effect of veverimer on gastric pH was measured continuously in vivo in healthy subjects using a microelectrode pH probe placed in the gastric compartment. Human DDI studies were conducted with 4 orally administered drugs, including those that demonstrated the most in vitro binding to veverimer and those with pH-dependent solubility (furosemide, aspirin, warfarin, dabigatran). Results Veverimer did not bind to any of the positively charged, neutral or zwitterionic drugs tested in vitro. It bound to 3 small (MW &amp;lt;332 Da), negatively charged drugs (aspirin, ethacrynic acid, furosemide); these interactions were reduced or eliminated in the presence of physiologically relevant concentrations of chloride. Neither furosemide nor aspirin showed clinically meaningful changes in pharmacokinetic parameters when coadministered with veverimer in human DDI studies (Figure 1). Veverimer increased gastric pH by ∼3.0 and 1.5 pH units in fasted and fed subjects, respectively. The increase in gastric pH was short-lived, with a peak within 1 hour after dosing and a return to baseline after ∼1.5 hours and ∼3 hours under fasting and fed conditions, respectively. The effect of veverimer on gastric pH was similar in the presence and absence of omeprazole. No clinically meaningful changes in systemic exposure, as indicated by Cmax and AUC, were observed when 3 drugs with pH-dependent solubility were coadministered with veverimer in human DDI studies (Figure 1). Conclusions In human DDI studies, we observed: a) no effect of veverimer on the bioavailability of drugs with physicochemical characteristics most susceptible to direct binding to the polymer; b) small, short-lived effects of veverimer on gastric pH; and c) no effect of veverimer on the bioavailability of drugs with pH-sensitive solubility. Therefore, it is concluded that there is a negligible risk of veverimer involvement in clinically significant DDIs.

Mycophenolic Acid and Its Pharmacokinetic Drug-Drug Interactions in Humans: Review of the Evidence and Clinical Implications.

Mycophenolic acid (MPA) is an immunosuppressive agent commonly prescribed during posttransplant periods for the prevention of acute and chronic rejection following organ transplantation. Compelling evidence has demonstrated a pivotal role of the exposure level of MPA in determining the rate of allograft rejection as well as the incidence of adverse outcomes, such as gastrointestinal complaints and myelosuppression. Because MPA has wide interindividual pharmacokinetic (PK) variability, the importance of maintaining the MPA concentration levels within its therapeutic range is clear. In addition, due to its complex PKs, MPA is prone to inadvertently develop PK drug-drug interactions (DDIs) with many agents, some of which are commonly used in organ transplant recipients. Failure to acknowledge such clinically significant PK DDIs between MPA and other coadministered drugs could potentially lead to devastating outcomes, ie, the occurrence of acute and chronic allograft rejection or the development of severe adverse events. The rationale to avoid concomitant use of certain drugs with MPA has been established; however, there is a lack of comprehensive literature to guide clinicians and medical professionals on the recognition and monitoring of potential PK DDIs when MPA is prescribed. In this article we comprehensively review, summarize, and discuss previous clinical studies that investigated the impact of coadministered drugs on the PK of MPA, with a major focus on the PK DDIs between MPA and commonly coadministered drugs.

Drug-Drug Interactions of P-gp Substrates Unrelated to CYP Metabolism.

Recent US Food and Drug Administration (FDA) draft guidance on pharmacokinetic drugdrug interactions (DDIs) has highlighted the clinical importance of ABC transporters B1 or P-glycoprotein (P-gp), hepatic organic anion-transporting polypeptide transporters and breast cancer resistant protein because of their broad substrate specificity and the potential to be involved in DDIs. This guidance has indicated that digoxin, dabigatran etexilate and fexofenadine are P-gp substrate drugs and has defined P-gp inhibitors as those that increase the AUC of digoxin by ≧1.25-fold in clinical DDI studies. However, when substrate drugs of both CYPs and P-gp are involved in DDIs, it remains that the mechanisms of DDIs will be quite ambiguous in assessing how much the CYPs and/or drug transporters partially contribute to DDIs. Since there are no detailed manuscripts that summarizes P-gp interactions unrelated to CYP metabolism, this article reviews the effects of potent P-gp inhibitors and P-gp inducers on the pharmacokinetics of P-gp substrate drugs, including digoxin, talinolol, dabigatran etexilate, and fexofenadine in human studies. In addition, the present outcome were to determine the PK changes caused by DDIs among P-gp substrate drugs without CYP metabolism in human DDI studies. Our manuscript concludes that the PK changes of the DDIs among P-gp drugs unrelated to CYP metabolism are less likely to be serious, and it appears to be convincing that the absences of clinical effects caused to the PK changes by the P-gp inducers is predominant compared with the excessive effects caused to those by the P-gp inhibitors.

Assessment of Pharmacokinetic Drug-Drug Interactions in Humans: In Vivo Probe Substrates for Drug Metabolism and Drug Transport Revisited.

Pharmacokinetic parameters of selective probe substrates are used to quantify the activity of an individual pharmacokinetic process (PKP) and the effect of perpetrator drugs thereon in clinical drug-drug interaction (DDI) studies. For instance, oral caffeine is used to quantify hepatic CYP1A2 activity, and oral dagibatran etexilate for intestinal P-glycoprotein (P-gp) activity. However, no probe substrate depends exclusively on the PKP it is meant to quantify. Lack of selectivity for a given enzyme/transporter and expression of the respective enzyme/transporter at several sites in the human body are the main challenges. Thus, a detailed understanding of the role of individual PKPs for the pharmacokinetics of any probe substrate is essential to allocate the effect of a perpetrator drug to a specific PKP; this is a prerequisite for reliably informed pharmacokinetic models that will allow for the quantitative prediction of perpetrator effects on therapeutic drugs, also in respective patient populations not included in DDI studies.

Physiological based pharmacokinetic modeling to estimate in vivo Ki of ketoconazole on renal P-gp using human drug-drug interaction study result of fesoterodine and ketoconazole

This study was conducted to estimate in vivo inhibition constant (Ki) of ketoconazole on renal P-glycoprotein (P-gp) using human drug-drug interaction (DDI) study result of fesoterodine and ketoconazole. Fesoterodine is a prodrug which is extensively hydrolyzed by non-specific esterases to the active metabolite 5-hydroxymethyl tolterodine (5-HMT). 5-HMT is then further metabolized via Cytochrome P450 (CYP) 2D6 and CYP3A4. It is reported that 5-HMT is a substrate of P-gp whereas fesoterodine is not. Renal clearance of 5-HMT is approximately two-times greater than renal glomerular filtration rate. This suggests the possibility that renal clearance of 5-HMT involves secretion by P-gp. Utilizing the available pharmacokinetic characteristics of fesoterodine and 5-HMT, we estimated in vivo Ki of ketoconazole on P-gp at kidney based on DDI study data using physiologically-based pharmacokinetic approach. The estimated in vivo Ki of ketoconazole for hepatic CYP3A4 (6.64 ng/mL) was consistent with the reported values. The in vivo Ki of ketoconazole for renal P-gp was successfully estimated as 2.27 ng/mL, which was notably lower than reported in vitro 50% inhibitory concentration (IC50) values ranged 223–2440 ng/mL due to different condition between in vitro and in vivo.

Organic Anion–Transporting Polypeptide and Efflux Transporter–Mediated Hepatic Uptake and Biliary Excretion of Cilostazol and Its Metabolites in Rats and Humans

Cilostazol undergoes extensive liver metabolism. However, the transporter-mediated hepatic disposition of cilostazol remains unknown. The present study was performed to investigate the hepatic uptake and biliary excretion of cilostazol and its metabolites (OPC-13015 and OPC-13213) using rat liver and human transporter-transfected cells in vitro. Cilostazol uptake by rat liver slices and isolated rat hepatocytes exhibited time-, concentration-, and temperature dependency and was decreased by Oatp inhibitors, which suggested that Oatp was involved in the hepatic uptake of cilostazol. Cilostazol uptake in rat hepatocytes, OATP1B1-, and OATP1B3-HEK293 cells indicated a saturable process with Km values of 2.7 μM, 17.7 μM, and 2.7 μM, respectively. Epigallocatechin gallate, cyclosporin A, rifampicin, and telmisartan inhibited cilostazol uptake in OATP1B1/1B3-HEK293 cells with Ki values close to their clinical plasma concentration, which suggested possible drug-drug interactions in humans via OATP1B1/1B3. Moreover, the cumulative biliary excretion of cilostazol and OPC-13015 was significantly decreased by quinidine, bilirubin, and novobiocin in perfused rat liver, but OPC-13213 biliary excretion was only inhibited by novobiocin, which suggested that the efflux transporters Mrp2, Bcrp, and P-gp were involved in the biliary excretion of cilostazol and its metabolites. Our findings indicated that multiple transporters were involved in the hepatic disposition of cilostazol and its metabolites.

Physiologically based pharmacokinetic modeling of sarpogrelate and its application for prediction of drug-drug interaction in humans

Physiologically based pharmacokinetic modeling of sarpogrelate and its application for prediction of drug-drug interaction in humans

The use of cynomolgus monkeys in predicting enzyme induction and human drug-drug interactions

The use of cynomolgus monkeys in predicting enzyme induction and human drug-drug interactions

Drug-drug interactions and QT prolongation as a commonly assessed cardiac effect - comprehensive overview of clinical trials.

BackgroundProarrhythmia assessment is one of the major concerns for regulatory bodies and pharmaceutical industry. ICH guidelines recommending preclinical tests have been established in attempt to eliminate the risk of drug-induced arrhythmias. However, in the clinic, arrhythmia occurrence is determined not only by the inherent property of a drug to block ion currents and disturb electrophysiological activity of cardiac myocytes, but also by many other factors modifying individual risk of QT prolongation and subsequent proarrhythmia propensity. One of those is drug-drug interactions. Since polypharmacy is a common practice in clinical settings, it can be anticipated that there is a relatively high risk that the patient will receive at least two drugs mutually modifying their proarrhythmic potential and resulting either in triggering the occurrence or mitigating the clinical symptoms. The mechanism can be observed either directly at the pharmacodynamic level by competing for the molecular targets, or indirectly by modifying the physiological parameters, or at the pharmacokinetic level by alteration of the active concentration of the victim drug.MethodsThis publication provides an overview of published clinical studies on pharmacokinetic and/or pharmacodynamic drug-drug interactions in humans and their electrophysiological consequences (QT interval modification). Databases of PubMed and Scopus were searched and combinations of the following keywords were used for Title, and Keywords fields: interaction, coadministration, combination, DDI and electrocardiographic, QTc interval, ECG. Only human studies were included. Over 4500 publications were retrieved and underwent preliminary assessment to identify papers accordant with the topic of this review. 76 papers reporting results for 96 drug combinations were found and analyzed.ResultsThe results show the tremendous variability of drug-drug interaction effects, which makes one aware of complexity of the problem, and suggests the need for assessment of an additional risk factors and careful ECG monitoring before administration of drugs with anticipated QT prolongation.ConclusionsDDIs can play significant roles in drugs’ cardiac safety, as evidenced by the provided examples. Assessment of the pharmacodynamic effects of the drug interactions is more challenging as compared to the pharmacokinetic due to the significant diversity in the endpoints which should be analyzed specifically for various clinical effects. Nevertheless, PD components of DDIs should be accounted for as PK changes alone do not allow to fully explain the electrophysiological effects in clinic situations.Electronic supplementary materialThe online version of this article (doi:10.1186/s40360-016-0053-1) contains supplementary material, which is available to authorized users.

A Rapid Biochemical Assay to Measure Small Molecules Binding to Pregnane Xenobiotic Receptors from Human, Dog and Rat

The pregnane xenobiotic receptor (PXR) is a nuclear receptor responsible for the activation of genes that participate in the metabolism of xenobiotics and endogenous chemicals. Upon ligand binding, PXR disassociates from the heat shock protein 90 and associates with the retinoid X receptor and steroid receptor co-activator 1 (SRC-1). This complex enters the nucleus and activates target genes, driving transcription of multiple genes, including cytochrome P450 (CYP) 3A4 which directly metabolizes foreign and natural chemicals. Determination of compound affinity for PXR is of high importance, because CYP P450 is responsible for the metabolism and elimination of more than half of clinical drugs. PXR binds to a diverse range of ligands due to its unique ligand binding domain (LBD) containing an expandable, hydrophobic pocket. As a result, predicting affinity of new molecules for PXR is difficult. In addition, the LBD has limited sequence conservation between species, making it difficult to extrapolate PXR activation from preclinical species to humans. Therefore, a reliable assay is crucial in evaluating the potential for drug-drug interactions associated with PXR. The commonly employed reporter gene assay is prone to false positives and suffers from drug induced cellular toxicity.Here, the tethered human, dog and rat PXR-LBD-SRC1 proteins were purified in a soluble and active form from E. coli. Binding of known PXR activators to the recombinant proteins was measured using an optimized Differential Scanning Fluorimetry (DSF) assay. A strong correlation between DSF ΔTm values and potencies in cellular assays was observed. PXRs from pre-clinical species bind some compounds with affinities significantly different from the human receptor, indicating that care needs to be taken when using PXR activation data from animals for predicting drug-drug interactions in humans.