Physiologically based pharmacokinetic modeling to predict the impact of liver cirrhosis on glucuronidation via UGT1A4 & UGT2B7/2B4 - a case study with midazolam

Hepatic impairment, due to liver cirrhosis, decreases the activity of cytochrome P450 enzymes (CYPs). The use of physiologically-based pharmacokinetic (PBPK) modeling to predict this effect for CYP substrates has been well-established, but the effect of cirrhosis on uridine-glucuronosyltransferase (UGT) activities is less studied and few PBPK models have been reported. UGT enzymes are involved in primary N-glucuronidation of midazolam and glucuronidation of 1'-OH-midazolam following CYP3A hydroxylation. In this study Simcyp® was used to establish PBPK models for midazolam, its primary metabolites midazolam-N-glucuronide (UGT1A4) and 1'-OH midazolam (CYP3A4/3A5) and the secondary metabolite 1'-OH-midazolam-O-glucuronide (UGT2B7/2B4), allowing to simulate the impact of liver cirrhosis on the primary and secondary glucuronidation of midazolam. The model was verified in non-cirrhotic subjects before extrapolation to cirrhotic patients of Child-Pugh (CP) classes A, B, and C. Our model successfully predicted the exposures of midazolam and its metabolites in non-cirrhotic and cirrhotic patients, with 86% of observed plasma concentrations within 5th-95th percentiles of predictions and observed geometrical mean of AUCinf and Cmax within 0.7-1.43-fold of predictions. The simulated metabolic ratio (AUCglucuronide/AUCparent, MR), was calculated for midazolam-N-glucuronide to midazolam (indicative of UGT1A4 activity) and decreased by 40% (CP A), 48% (CP B), and 75% (CP C). For 1'-OH-midazolam-O-glucuronide to 1'-OH-midazolam the MR (indicative of UGT2B7/2B4 activity) dropped by 35% (CP A), 51% (CP B), and 64% (CP C). These predicted MRs were corroborated by the observed data. This work thus increases confidence in Simcyp® predictions of the effect of liver cirrhosis on the pharmacokinetics of UGT1A4 and UGT2B7/UGT2B4 substrates. Significance Statement This paper presents a PBPK model for midazolam and its metabolites and verifies the accurate simulation of pharmacokinetic profiles when using the Simcyp® hepatic impairment population models. Exposure changes of midazolam-N-glucuronide and 1'-OH-midazolam-O-glucuronide reflect the impact of decreases in UGT1A4 and UGT2B7/2B4 glucuronidation activity in cirrhotic patients. The approach used in this study may be extended to verify the modeling of other UGT enzymes affected by liver cirrhosis.

In silico modeling and simulation of organ-on-a-chip systems to support data analysis and a priori experimental design

Organ-on-a-chip (OoC) systems are a promising new class of in vitro devices that can combine various tissues, cultured in different compartments, linked by media flow. The properties of these novel in vitro systems linked to increased physiological relevance of culture conditions may lead to more in vivo-relevant cell phenotypes, enabling better in vitro pharmacology and toxicology assessment. Improved cell activities combined with longer lasting cultures offer opportunities to improve the characterization of absorption, distribution, metabolism, and excretion (ADME) processes, potentially leading to more accurate prediction of human pharmacokinetics (PKs). The inclusion of barrier tissue elements and metabolically competent tissue types results in complex concentration-time profiles (in vitro PK) for test drugs and their metabolites that require appropriate mathematical modeling of in vitro data for parameter estimation. In particular, modeling is critical to estimate in vitro ADME parameters when multiple different tissues are combined in a single device. Therefore, sophisticated in silico data analysis and a priori experimental design are highly recommended for OoC experiments in a manner not needed with standard ADME screening. The design of the experiment should be optimized based on an investigation of the structural characteristics of the in vitro system, the ADME features of the test compound and any available knowledge of cell phenotypes. This tutorial aims to provide such a modeling framework to inform experimental design and refine parameter estimation in a Gut-Liver OoC (the most studied multi-organ systems to predict the oral drug PKs) to improve translatability of data generated in such complex cellular systems.

Phase 1, first-in-human study of TYRP1-TCB (RO7293583), a novel TYRP1-targeting CD3 T-cell engager, in metastatic melanoma: active drug monitoring to assess the impact of immune response on drug exposure

Introduction

Although checkpoint inhibitors (CPIs) have improved outcomes for patients with metastatic melanoma, those progressing on CPIs have limited therapeutic options. To address this unmet need and overcome CPI resistance mechanisms, novel immunotherapies, such as T-cell engaging agents, are being developed. The use of these agents has sometimes been limited by the immune response mounted against them in the form of anti-drug antibodies (ADAs), which is challenging to predict preclinically and can lead to neutralization of the drug and loss of efficacy.

Methods

TYRP1-TCB (RO7293583; RG6232) is a T-cell engaging bispecific (TCB) antibody that targets tyrosinase-related protein 1 (TYRP1), which is expressed in many melanomas, thereby directing T cells to kill TYRP1-expressing tumor cells. Preclinical studies show TYRP1-TCB to have potent anti-tumor activity. This first-in-human (FIH) phase 1 dose-escalation study characterized the safety, tolerability, maximum tolerated dose/optimal biological dose, and pharmacokinetics (PK) of TYRP1-TCB in patients with metastatic melanoma (NCT04551352).

Results

Twenty participants with cutaneous, uveal, or mucosal TYRP1-positive melanoma received TYRP1-TCB in escalating doses (0.045 to 0.4 mg). All participants experienced ≥1 treatment-related adverse event (TRAE); two participants experienced grade 3 TRAEs. The most common toxicities were grade 1-2 cytokine release syndrome (CRS) and rash. Fractionated dosing mitigated CRS and was associated with lower levels of interleukin-6 and tumor necrosis factor-alpha. Measurement of active drug (dual TYPR1- and CD3-binding) PK rapidly identified loss of active drug exposure in all participants treated with 0.4 mg in a flat dosing schedule for ≥3 cycles. Loss of exposure was associated with development of ADAs towards both the TYRP1 and CD3 domains. A total drug PK assay, measuring free and ADA-bound forms, demonstrated that TYRP1-TCB-ADA immune complexes were present in participant samples, but showed no drug activity in vitro.

Discussion

This study provides important insights into how the use of active drug PK assays, coupled with mechanistic follow-up, can inform and enable ongoing benefit/risk assessment for individuals participating in FIH dose-escalation trials. Translational studies that lead to a better understanding of the underlying biology of cognate T- and B-cell interactions, ultimately resulting in ADA development to novel biotherapeutics, are needed.

PBPK Modelling for Drugs Cleared by Non-CYP Enzymes: State-of-the-Art and Future Perspectives

Physiologically-based pharmacokinetic (PBPK) modeling has become the established method for predicting human pharmacokinetics (PK) and drug-drug interactions (DDI). The number of drugs cleared by non-CYP enzyme metabolism has increased steadily and to date, there is no consolidated overview of PBPK modeling for drugs cleared by non-CYP enzymes. This review aims to describe the state-of-the-art for PBPK modeling for drugs cleared via non-CYP enzymes, to identify successful strategies, to describe gaps and to provide suggestion to overcome them. To this end, we conducted a detailed literature search and found 58 articles published before the 1st of January 2023 containing 95 examples of clinical PBPK models for 62 non-CYP enzyme substrates. Reviewed articles covered the drug clearance by uridine 5'-diphospho-glucuronosyltransferases (UGTs), aldehyde oxidase (AO), flavin-containing monooxygenases (FMOs), sulfotransferases (SULTs) and carboxylesterases (CES), with UGT2B7, UGT1A9, CES1, FMO3 and AO being the enzymes most frequently involved. In vitro-in vivo extrapolation (IVIVE) of intrinsic clearance and the bottom-up PBPK modeling involving non-CYP enzymes remains challenging. We observed that the middle-out modeling approach was applied in 80% of the cases, with metabolism parameters optimized in 73% of the models. Our review could not identify a standardized approach used for model optimization based on clinical data, with manual optimization employed most frequently. Successful development of models for UGT2B7, UGT1A9, CES1, and FMO3 substrates provides a foundation for other drugs metabolized by these enzymes and guides the way forward in creating PBPK models for other enzymes in these families. Significance Statement Our review charts the rise of PBPK modeling for drugs cleared by non-CYP enzymes. Analyzing 58 articles and 62 non-CYP enzyme substrates, we found that UGTs, AO, FMOs, SULTs, and CES were the main enzyme families involved and that UGT2B7, UGT1A9, CES1, FMO3 and AO are the individual enzymes with the strongest PBPK modeling precedents. Approaches established for these enzymes can now be extended to additional substrates and to drugs metabolized by enzymes that are similarly well characterized.

The Activity of Members of the UDP-Glucuronosyltransferase Subfamilies UGT1A and UGT2B is Impaired in Patients with Liver Cirrhosis

BACKGROUND AND OBJECTIVE

The impact of liver cirrhosis on the activity of UDP-glucuronosyltransferases (UGTs) is currently not well characterized. We investigated the glucuronidation capacity and glucuronide accumulation in patients with liver cirrhosis.

METHODS

We administered the Basel phenotyping cocktail (caffeine, efavirenz, flurbiprofen, omeprazole, metoprolol, midazolam) to patients with liver cirrhosis (n = 16 Child A, n = 15 Child B, n = 5 Child C) and n = 12 control subjects and obtained pharmacokinetic profiles of substrates and primary metabolites and their glucuronides.

RESULTS

Caffeine and its metabolite paraxanthine were only slightly glucuronidated. The metabolic ratio (AUCglucuronide/AUCparent, MR) was not affected for caffeine but decreased by 60% for paraxanthine glucuronide formation in Child C patients. Efavirenz was not glucuronidated whereas 8-hydroxyefavirenz was efficiently glucuronidated. The MR of 8-hydroxyefavirenz-glucuronide formation increased three-fold in Child C patients and was negatively correlated with the glomerular filtration rate. Flurbiprofen and omeprazole were not glucuronidated. 4-Hydroxyflurbiprofen and 5-hydroxyomeprazole were both glucuronidated but the corresponding MRs for glucuronide formation were not affected by liver cirrhosis. Metoprolol, but not α-hydroxymetoprolol, was glucuronidated, and the MR for metoprolol-glucuronide formation dropped by 60% in Child C patients. Both midazolam and its metabolite 1'-hydroxymidazolam underwent glucuronidation, and the corresponding MRs for glucuronide formation dropped by approximately 80% in Child C patients. No relevant glucuronide accumulation occurred in patients with liver cirrhosis.

CONCLUSIONS

Detailed analysis revealed that liver cirrhosis may affect the activity of UGTs of the UGT1A and UGT2B subfamilies according to liver function. Clinically significant glucuronide accumulation did not occur in the population investigated.

CLINICAL TRIAL REGISTRATION

NCT03337945.

Dose adjustment in patients with liver cirrhosis - comparison of two different modeling approaches

Failure to perform adequate dose adjustment in patients with liver cirrhosis may be associated with increased toxicity. We compared the prediction of AUC and clearance for the six compounds of the Basel phenotyping cocktail (caffeine, efavirenz, flurbiprofen, omeprazole, metoprolol, midazolam) using a well-known physiology-based pharmacokinetic approach ("PBPK approach", Simcyp®) and a novel top-down method based on the systemic clearance in healthy volunteers adjusted for markers of liver and renal dysfunction ("top-down approach"). With few exceptions, plasma concentration-time curves were accurately predicted by the PBPK approach. In comparison to the measured AUC and clearance of these drugs in patients with liver cirrhosis and healthy controls, except for efavirenz, the estimates of both approaches were within 2 standard deviations of the mean for total and free drug concentrations. For both approaches, a correction factor for dose adjustment in patients with liver cirrhosis could be calculated for the drugs administered. AUCs calculated using the adjusted doses were comparable to the AUCs measured in control subjects, with slightly more accurate predictions generated by the PBPK approach. For drugs with a free fraction <50%, predictions using free drug concentrations were more accurate than with total drug concentrations. In conclusion, both methods provided good qualitative predictions of the changes by liver cirrhosis in the pharmacokinetics of the six compounds investigated. The top-down approach is easier to implement but the PBPK approach predicted changes in drug exposure more accurately than the top-down approach and provided reliable estimates for plasma concentrations.

A84 FACTORS ASSOCIATED WITH HIGH LEVELS OF TELEPHONE CARE SATISFACTION AMONG INDIVIDUALS WITH INFLAMMATORY BOWEL DISEASE

Background

Individuals with inflammatory bowel disease (IBD) require regular medical follow-up with gastroenterology care providers. Individuals in rural areas face barriers in assessing specialized IBD care. Virtual care (VC) may act as a solution. The coronavirus disease 2019 pandemic increased the use of VC, particularly telephone care (TC) appointments in Saskatchewan, Canada. There is limited evidence around the levels and factors associated with satisfaction with TC among individuals with IBD.

Purpose

This study aims to measure satisfaction with TC in individuals with IBD who live in Saskatchewan, Canada, and evaluate the factors associated with TC satisfaction.

Method

A cross-sectional study was conducted among individuals with IBD through an online survey between December 2021 and April 2022 in Saskatchewan. The Telephone Care Satisfaction Questionnaire for individuals with IBD (TCSQ-patient) was a 16-item questionnaire used to measure TC satisfaction on a scale from 1 (very dissatisfied) to 7 (very satisfied). The online survey also included the Quality of Care Through the Patient’s Eyes-IBD (QUOTE-IBD) questionnaire, Short Inflammatory bowel disease questionnaire (SIBDQ), and demographic questions. Factors associated with TC satisfaction were explored using linear regression models. A backward model building strategy was used, and 95% confidence intervals (95%CI) were reported.

Result(s)

In total, 87 individuals with IBD participated in the study. Among the study participants, 54 (64.3%) had Crohn's disease, 53 (61.6%) were female, 60 (69.8%) lived in urban centres, and 37 (43.5%) were between 41-59 years old. The mean satisfaction with TC was 5.70 (SD=0.94). In addition, the means of the QUOTE-IBD and SIBDQ were, respectively, 8.96 (SD=1.70) and 48.14 (SD=13.02). In the bivariate analysis, area of residence (rural vs. urban) and health related quality of life quality (SIBDQ>50 vs SIBDQ<50) were associated with satisfaction with TC, respectively, 0.47 (95%CI 0.02-0.91) and 0.48 (95%CI 0.08-0.88). Adjusting by gender, age group, type of disease, and health care provider managing IBD, we identified that the satisfaction with TC was 0.48 (95%CI 0.02-0.94) higher among individuals with IBD living in rural Saskatchewan in comparison to their urban counterparts.

Conclusion(s)

Individuals living with IBD in Saskatchewan reported high levels of satisfaction with TC. Rural residence is associated with higher levels of TC satisfaction. These results could help in the promotion of TC utilization and improve access to specialized IBD care, especially among those living in rural areas.

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Saskatchewan Health Research Foundation (SHRF)

Disclosure of Interest

None Declared

A83 ADAPTATION AND VALIDATION OF QUESTIONNAIRES TO MEASURE SATISFACTION WITH TELEPHONE CARE AMONG IBD PATIENTS AND GASTROENTEROLOGY CARE PROVIDERS

Background

People living with inflammatory bowel disease (IBD) require regular medical follow-up, which could be challenging for individuals living in rural areas and those who have limited access to specialized care. Telephone care (TC) could improve health care by increasing access to specialized care. The Covid-19 pandemic resulted in increased use of virtual care, which was predominantly TC in Saskatchewan (SK) , Canada. There are no validated questionnaires to measure satisfaction with TC among IBD patients and gastrointestinal care providers (GCPs).

Purpose

This study aimed to adapt and validate a questionnaire to evaluate the satisfaction of IBD individuals and GCPs with TC in SK, Canada.

Method

The Telehealth Usability Questionnaire was adapted to the IBD TC context by a committee of experts, comprised of three IBD GCPs, two IBD-patient partners, and two health care researchers. Two questionnaires were generated -: the Telephone Care Satisfaction Questionnaire (TCSQ) for patients (IBD-TCSQ-patient) and GCPs (IBD-TCSQ-provider). The committee evaluated the content validity of the adapted questionnaires. A pilot assessed the readability and usability of the questionnaire items. Subsequently, individuals living with IBD in SK and GCPs completed an online survey with the TCSQ-patient and IBD-TCSQ-provider questionnaires in the winter of 2022. Data were analysed using descriptive and correlational techniques. Psychometric analyses were conducted to examine the reliability and validity of the TCSQ-patient, but not for the TCSQ-provider due to small sample size.

Result(s)

The IBD-TCSQ-patient and IBD-TCSQ-provider questionnaires were developed, each with 16 individual items and one question on global TC satisfaction. The pilot demonstrated good readability and usability of the questionnaires. Then, 87 IBD individuals completed the IBD-TCSQ-patient and six GCPs the IBD-TCSQ-provider. The standardized level of TC satisfaction for the 16-item IBD-TCSQ-patient was 5.70 (SD=0.94) on a scale from 1.00-7.00. All items of the IBD-TCSQ-patient were significantly correlated (p<0.001). A strong correlation was observed between the 16-item standardized TC satisfaction and its overall item r=0.85 (p<0.001). The IBD-TCSQ-patient had optimal internal reliability (α=0.96). Two factors were identified in the exploratory factor analysis. Factor 1 focused on TC convenience while factor 2 addressed TC usability. Regarding the IBD-TCSQ-provider questionnaire, the standardized level of TC satisfaction was 5.76 (SD=0.68) on a scale from 1.00 to 7.00.

Conclusion(s)

We generated questionnaires to measure satisfaction with TC among individuals living with IBD and GCPs. The study results confirmed good validity and reliability of the IBD-TCSQ-patient questionnaire. The IBD-TCSQ-provider questionnaire was adapted; subsequent studies could assess its validity and reliability among GCPs nationally. These questionnaires could help identify opportunities for improvement and utilization of TC among IBD patients and GCPs.

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Other, None

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Saskatchewan Health Research Foundation (SHRF)

Disclosure of Interest

None Declared

Contribution of UGT Enzymes to Human Drug Metabolism Stereoselectivity: A Case Study of Medetomidine, RO5263397, Propranolol, and Testosterone

The enantiomeric forms of chiral compounds have identical physical properties but may vary greatly in their metabolism by individual enzymes. Enantioselectivity in UDP-glucuronosyl transferase (UGT) metabolism has been reported for a number of compounds and with different UGT isoforms involved. However, the impact of such individual enzyme results on overall clearance stereoselectivity is often not clear. The enantiomers of medetomidine, RO5263397, and propranolol and the epimers testosterone and epitestosterone exhibit more than a 10-fold difference in glucuronidation rates by individual UGT enzymes. In this study, we examined the translation of human UGT stereoselectivity to hepatic drug clearance considering the combination of multiple UGTs to overall glucuronidation, the contribution of other metabolic enzymes such as cytochrome P450s (P450s), and the potential for differences in protein binding and blood/plasma partitioning. For medetomidine and RO5263397, the high individual enzyme (UGT2B10) enantioselectivity translated into ∼3- to >10-fold differences in predicted human hepatic in vivo clearance. For propranolol, the UGT enantioselectivity was irrelevant in the context of high P450 metabolism. For testosterone, a complex picture emerged due to differential epimeric selectivity of various contributing enzymes and potential for extrahepatic metabolism. Quite different patterns of P450- and UGT-mediated metabolism were observed across species, as well as differences in stereoselectivity, indicating that extrapolation from human enzyme and tissue data are essential when predicting human clearance enantioselectivity. SIGNIFICANCE STATEMENT: Individual enzyme stereoselectivity illustrates the importance of three-dimensional drug-metabolizing enzyme-substrate interactions and is essential when considering the clearance of racemic drugs. However, translation from in vitro to in vivo can be challenging as contributions from multiple enzymes and enzyme classes must be combined with protein binding and blood/plasma partitioning data to estimate the net intrinsic clearance for each enantiomer. Preclinical species may be misleading as enzyme involvement and metabolism stereoselectivity can differ substantially.

POLYMYALGIA RHEUMATICA AFTER MRNA COVID-19 VACCINATION

Introduction

Polymyalgia rheumatica (PMR) is an inflammatory disorder characterized by muscle pain and stiffness. We present a 67-year-old man who developed PMR after immunization with the mRNA COVID-19 vaccine.

Case Description

A 67-year-old male with a history of viral pericarditis, non-ischemic cardiomyopathy, Raynaud's phenomenon, and prostate cancer presented for evaluation of acute-onset proximal muscle pain and weakness, extreme fatigue, malaise, and weight loss. Symptoms developed 10 days after the first dose of the mRNA COVID-19 vaccine. No associated fever or skin rashes. No history of natural COVID-19 infection. A workup for malignancy was negative. CRP and ESR were elevated. ANA was positive (1:80, speckled pattern). ENAs were negative. CK and aldolase were normal. He had low IgG at 328 mg/dL with normal IgA and IgM. However, repeat IgG levels a week later were normal (1130 mg/dL), raising the possibility of a laboratory error. Lymphocyte subsets in peripheral blood were normal. IgG titers to the SARS-COV2 spike and nucleocapsid proteins were consistent with COVID-19 immunity from prior immunization. He was treated with low-dose oral prednisone with resolution of his symptoms and has been slowly tapering prednisone as tolerated.

Discussion

This case report raises the possibility that PMR may be triggered by an immune response to the mRNA COVID-19 vaccine in susceptible individuals. However, further studies involving a larger population are required to assess whether this association is causative or rather coincidental.

Preclinical InVivo Data Integrated in a Modeling Network Informs a Refined Clinical Strategy for a CD3 T-Cell Bispecific in Combination with Anti-PD-L1

TYRP1-TCB is a CD3 T-cell bispecific (CD3-TCB) antibody for the treatment of advanced melanoma. A tumor growth inhibition (TGI) model was developed using mouse xenograft data with TYRP1-TCB monotherapy or TYRP1-TCB plus anti-PD-L1 combination. The model was translated to humans to inform a refined clinical strategy. From xenograft mouse data, we estimated an EC₅₀ of 0.345 mg/L for TYRP1-TCB, close to what was observed in vitro using the same tumor cell line. The model showed that, though increasing the dose of TYRP1-TCB in monotherapy delays the time to tumor regrowth and promotes higher tumor cell killing, it also induces a faster rate of tumor regrowth. Combination with anti-PD-L1 extended the time to tumor regrowth by 25% while also decreasing the tumor regrowth rate by 69% compared to the same dose of TYRP1-TCB alone. The model translation to humans predicts that if patients' tumors were scanned every 6 weeks, only 46% of the monotherapy responders would be detected even at a TYRP1-TCB dose resulting in exposures above the EC₉₀. However, combination of TYRP1-TCB and anti-PD-L1 in the clinic is predicted to more than double the overall response rate (ORR), duration of response (DoR) and progression-free survival (PFS) compared to TYRP1-TCB monotherapy. As a result, it is highly recommended to consider development of CD3-TCBs as part of a combination therapy from the outset, without the need to escalate the CD3-TCB up to the Maximum Tolerated Dose (MTD) in monotherapy and without gating the combination only on RECIST-derived efficacy metrics.

Application of a gut-liver-on-a-chip device and mechanistic modelling to the quantitative in vitro pharmacokinetic study of mycophenolate mofetil

Microphysiological systems (MPS) consisting of multiple linked organ-on-a-chip (OoC) components are highly promising tools with potential to provide more relevant in vitro to in vivo translation of drug disposition, efficacy and toxicity. A gut-liver OoC system was employed with Caco2 cells in co-culture with HT29 cells in the intestinal compartment and single donor primary hepatocytes in the hepatic compartment for the investigation of intestinal permeability, metabolism (intestinal and hepatic) and potential interplay of those processes. The prodrug mycophenolate mofetil was tested for quantitative evaluation of the gut-liver OoC due to the contribution of both gut and liver in its metabolism. Conversion of mycophenolate mofetil to active drug mycophenolic acid and further metabolism to a glucuronide metabolite was assessed over time in the gut apical, gut basolateral and liver compartments. Mechanistic modelling of experimental data was performed to estimate clearance and permeability parameters for the prodrug, active drug and glucuronide metabolite. Integration of gut-liver OoC data with in silico modelling allowed investigation of the complex combination of intestinal and hepatic processes, which is not possible with standard single tissue in vitro systems. A comprehensive evaluation of the mechanistic model, including structural model and parameter identifiability and global sensitivity analysis, enabled a robust experimental design and estimation of in vitro pharmacokinetic parameters. We propose that similar methodologies may be applied to other multi-organ microphysiological systems used for drug metabolism studies or wherever quantitative knowledge of changing drug concentration with time enables better understanding of biological effect.

Exploration and application of a liver-on-a-chip device in combination with modelling and simulation for quantitative drug metabolism studies

Microphysiological systems (MPS) are complex and more physiologically realistic cellular in vitro tools that aim to provide more relevant human in vitro data for quantitative prediction of clinical pharmacokinetics while also reducing the need for animal testing. The PhysioMimix liver-on-a-chip integrates medium flow with hepatocyte culture and has the potential to be adopted for in vitro studies investigating the hepatic disposition characteristics of drug candidates. The current study focusses on liver-on-a-chip system exploration for multiple drug metabolism applications. Characterization of cytochrome P450 (CYP), UDP-glucuronosyl transferase (UGT) and aldehyde oxidase (AO) activities was performed using 15 drugs and in vitro to in vivo extrapolation (IVIVE) was assessed for 12 of them. Next, the utility of the liver-on-a-chip for estimation of the fraction metabolized (f_m) via specific biotransformation pathways of quinidine and diclofenac was established. Finally, the metabolite identification opportunities were also explored using efavirenz as an example drug with complex primary and secondary metabolism involving a combination of CYP, UGT and sulfotransferase enzymes. A key aspect of these investigations was the application of mathematical modelling for improved parameter calculation. Such approaches will be required for quantitative assessment of metabolism and/or transporter processes in systems where medium flow and system compartments result in non-homogeneous drug concentrations. In particular, modelling was used to explore the effect of evaporation from the medium and it was found that the intrinsic clearance (CL_int) might be underestimated by up to 40% for low clearance compounds if evaporation is not accounted for. Modelling of liver-on-a-chip in vitro data also enhanced the approach to f_m estimation allowing objective assessment of metabolism models of different complexity. The resultant diclofenac f_m,UGT of 0.64 was highly comparable with values reported previously in the literature. The current study demonstrates the integration of mathematical modelling with experimental liver-on-a-chip studies and illustrates how this approach supports generation of high quality of data from complex in vitro cellular systems.

HCV Infection Alters Salivary Gland Histology and Saliva Composition

Hepatitis C virus (HCV) infection is the most common blood-borne chronic infection in the United States. Chronic lymphocytic sialadenitis and sicca syndrome have been reported in chronic HCV infection. Up to 55% of these patients may have xerostomia; the mechanisms of the xerostomia and salivary gland (SG) hypofunction remain controversial. The objectives of this project are to establish if xerostomia associates with SG and HCV infection and to characterize the structural changes in SG and saliva composition. Eighteen HCV-infected patients with xerostomia were evaluated for SG dysfunction; 6 of these patients (patients 1–6) were further evaluated for SG histopathological changes and changes in saliva composition. The techniques used include clinical and laboratory assessment, SG ultrasonography, histological evaluation, sialochemical and proteomics analysis, and RNA in situ hybridization. All the HCV patients had low saliva flow, chronic sialadenitis, and SG fibrosis and lacked Sjögren syndrome (SS) characteristic autoantibodies. Further evaluation of a subgroup of 6 HCV patients (patients 1–6) demonstrated diffuse lymphocytic infiltrates that are predominantly CD8+ T cells with a significant increase in the number of inflammatory cells. Alcian Blue/periodic acid–Schiff staining showed significant changes in the ratio and intensity of the acinar secretory units of the HCV patients’ minor SG. The submandibular glands showed significant ultrasonographic abnormalities in the parenchyma relative to the parotid glands. Significant changes were also observed in the concentration of sodium and mucin 5b. Although no significant correlation was observed between the lymphocytic infiltrates and the years of HCV chronic infection, a positive correlation was observed between HCV RNA–positive epithelial cells and the years of HCV infection. Consistent with the low saliva flow and xerostomia, patients showed changes in several markers of SG acinar and ductal function. Changes in the composition of the saliva suggest that HCV infection can cause xerostomia by mechanisms distinct from SS.

Physiologically-Based Pharmacokinetic Modelling of Entrectinib Parent and Active Metabolite to Support Regulatory Decision-Making

BACKGROUND AND OBJECTIVE

Entrectinib is a selective inhibitor of ROS1/TRK/ALK kinases, recently approved for oncology indications. Entrectinib is predominantly cleared by cytochrome P450 (CYP) 3A4, and modulation of CYP3A enzyme activity profoundly alters the pharmacokinetics of both entrectinib and its active metabolite M5. We describe development of a combined physiologically based pharmacokinetic (PBPK) model for entrectinib and M5 to support dosing recommendations when entrectinib is co-administered with CYP3A4 inhibitors or inducers.

METHODS

A PBPK model was established in Simcyp^® Simulator. The initial model based on in vitro-in vivo extrapolation was refined using sensitivity analysis and non-linear mixed effects modeling to optimize parameter estimates and to improve model fit to data from a clinical drug-drug interaction study with the strong CYP3A4 inhibitor, itraconazole. The model was subsequently qualified against clinical data, and the final qualified model used to simulate the effects of moderate to strong CYP3A4 inhibitors and inducers on entrectinib and M5 pharmacokinetics.

RESULTS

The final model showed good predictive performance for entrectinib and M5, meeting commonly used predictive performance acceptance criteria in each case. The model predicted that co-administration of various moderate CYP3A4 inhibitors (verapamil, erythromycin, clarithromycin, fluconazole, and diltiazem) would result in an average increase in entrectinib exposure between 2.2- and 3.1-fold, with corresponding average increases for M5 of approximately 2-fold. Co-administration of moderate CYP3A4 inducers (efavirenz, carbamazepine, phenytoin) was predicted to result in an average decrease in entrectinib exposure between 45 and 79%, with corresponding average decreases for M5 of approximately 50%.

CONCLUSIONS

The model simulations were used to derive dosing recommendations for co-administering entrectinib with CYP3A4 inhibitors or inducers. PBPK modeling has been used in lieu of clinical studies to enable regulatory decision-making.

In vitro and clinical investigations to determine the drug-drug interaction potential of entrectinib, a small molecule inhibitor of neurotrophic tyrosine receptor kinase (NTRK)

Background Entrectinib is a CNS-active, potent inhibitor of tyrosine receptor kinases A/B/C, ROS1 and anaplastic lymphoma kinase approved for use in patients with solid tumors. We describe the in vitro and clinical studies investigating potential entrectinib drug-drug interactions. Methods In vitro studies with human biomaterials assessed the enzymes involved in entrectinib metabolism, and whether entrectinib modulates the activity of the major cytochrome P450 (CYP) enzymes or drug transporter P-glycoprotein. Clinical studies investigated the effect of a strong CYP3A4 inhibitor (itraconazole) and inducer (rifampin) on single-dose entrectinib pharmacokinetics. The effect of entrectinib on sensitive probe substrates for CYP3A4 (midazolam) and P-glycoprotein (digoxin) were also investigated. Results Entrectinib is primarily metabolized by CYP3A4. In vitro, entrectinib is a CYP3A4/5 inhibitor (IC₅₀ 2 μM) and a weak CYP3A4 inducer. Entrectinib inhibited P-glycoprotein (IC₅₀ 1.33 μM) but is a poor substrate. In healthy subjects, itraconazole increased entrectinib C_max and AUC by 73% and 504%, respectively, and rifampin decreased entrectinib C_max and AUC by 56% and 77%, respectively. Single dose entrectinib did not affect midazolam AUC, although C_max decreased by 34%. Multiple dose entrectinib increased midazolam AUC by 50% and decreased C_max by 21%. Single dose entrectinib increased digoxin AUC and C_max by 18% and 28%, respectively, but did not affect digoxin renal clearance. Conclusions Entrectinib is a CYP3A4 substrate and is sensitive to the effects of coadministered moderate/strong CYP3A4 inhibitors and strong inducers, and requires dose adjustment. Entrectinib is a weak inhibitor of CYP3A4 and P-glycoprotein and no dose adjustments are required with CYP3A4/P- glycoprotein substrates.

Registration Number (Study 2) NCT03330990 (first posted online November 6, 2017) As studies 1 and 3 are phase 1 trials in healthy subjects, they are not required to be registered.

Characterization of Hepatic UDP-Glucuronosyltransferase Enzyme Abundance-Activity Correlations and Population Variability Using a Proteomics Approach and Comparison with Cytochrome P450 Enzymes

The expression of ten major drug-metabolizing UDP-glucuronosyltransferase (UGT) enzymes in a panel of 130 human hepatic microsomal samples was measured using a liquid chromatography-tandem mass spectrometry-based approach. Simultaneously, ten cytochromes P450 and P450 reductase were also measured, and activity-expression relationships were assessed for comparison. The resulting data sets demonstrated that, with the exception of UGT2B17, 10th to 90th percentiles of UGT expression spanned 3- to 8-fold ranges. These ranges were small relative to ranges of reported mean UGT enzyme expression across different laboratories. We tested correlation of UGT expression with enzymatic activities using selective probe substrates. A high degree of abundance-activity correlation (Spearman's rank correlation coefficient > 0.6) was observed for UGT1As (1A1, 3, 4, 6) and cytochromes P450. In contrast, protein abundance and activity did not correlate strongly for UGT1A9 and UGT2B enzymes (2B4, 7, 10, 15, and 17). Protein abundance was strongly correlated for UGTs 2B7, 2B10, and 2B15. We suggest a number of factors may contribute to these differences including incomplete selectivity of probe substrates, correlated expression of these UGT2B isoforms, and the impact of splice and polymorphic variants on the peptides used in proteomics analysis, and exemplify this in the case of UGT2B10. Extensive correlation analyses identified important criteria for validating the fidelity of proteomics and enzymatic activity approaches for assessing UGT variability, population differences, and ontogenetic changes. SIGNIFICANCE STATEMENT: Protein expression data allow detailed assessment of interindividual variability and enzyme ontogeny. This study has observed that expression and enzyme activity are well correlated for hepatic UGT1A enzymes and cytochromes P450. However, for the UGT2B family, caution is advised when assuming correlation of expression and activity as is often done in physiologically based pharmacokinetic modeling. This can be due to incomplete probe substrate specificities, but may also be related to presence of inactive UGT protein materials and the effect of splicing variations.

A183 TELEHEALTH USE IN RURAL SASKATCHEWAN AND INFLAMMATORY BOWEL DISEASE OUTCOMES

Background

Appropriate management of inflammatory bowel disease (IBD) often requires multiple specialist appointments per year. Living in rural locations may pose a barrier to regular specialist care. Saskatchewan (SK) has a large rural population. Prior to COVID-19, telehealth (TH) in SK was not routinely used for either patient assessment or follow up. Furthermore, TH was exclusively between hospitals and specific TH sites without direct contact using patient’s personal phones.

Aims

The objective of this study was to assess the differences in demographics, disease characteristics, outcomes, and health care utilization between patients from rural SK with IBD who used TH and those who did not.

Methods

A retrospective chart review was completed on all rural patients (postal code S0*) with IBD in SK who were followed at the Multidisciplinary IBD Clinic in Saskatoon between January 2018 and February 2020. Patients were classified as using TH if they had ever used it. Information on demographics, disease characteristics, and access to IBD-related health care in the year prior to their last IBD clinic visit or endoscopy was collected. Data was not collected for clinic visits after March 1, 2020 as all outpatient care became remote secondary to the COVID-19 pandemic. Mean, standard deviations, median and interquartile ranges (IQR) were reported. Mann-Witney U and Chi-Square tests were used to determine differences between the groups.

Results

In total, 288 rural SK IBD patients were included, 30 (10.4%) used TH and 258 (89.6%) did not. Patient demographics were not significantly different between the two groups; although, there was a statistically significant difference in the proportion of ulcerative colitis patients (17% TH vs. 38% non-TH, p=0.02). The percentage of patients with clinical remission was 87% for TH patients and 74% for non-TH patients (p=0.13). There were no significant differences in health care utilization patterns and biochemical markers of disease, including c-reactive protein (CRP) and fecal calprotectin (FCP) (p>0.05).

Conclusions

Prior to the pandemic, a small percentage of patients with IBD in rural SK ever used TH. A small proportion of UC patients used TH. No significant differences in disease characteristics, outcomes, or health care utilization were identified. Further study is warranted to identify barriers to use of this technology to tailor care to this patient group and improve access to care, especially now as the COVID-19 pandemic has drastically changed the use of virtual care.

Funding Agencies

None

A182 INFLAMMATORY BOWEL DISEASE AMONG SENIORS IN SASKATCHEWAN

Background

Inflammatory bowel disease (IBD) is a chronic inflammatory condition comprised of two major disorders: ulcerative colitis (UC) and Crohn’s disease (CD).The age of onset for many patients with UC and CD is between 15 and 30 years, with a second peak between 50 and 80 years of age.

Aims

We aim to determine if there are differences in disease characteristics, outcomes, and IBD-related health care utilization between elderly patients with IBD diagnosed at a young age compared to those diagnosed later in life.

Methods

A retrospective chart review of elderly (age ≥ 60 years) patients with IBD was conducted.Patients aged ≥ 60 years who were seen at the Saskatchewan Multidisciplinary IBD Clinic at the Royal University Hospital from 2012 to 2020 were included. Information on demographics, disease characteristics, and access to IBD-related health care was collected. Patients were divided in two groups according to age of diagnosis: &lt;60 and ≥ 60 years. Chi-squares were used to compare the groups. Charts with missing data were omitted in the final analysis. Three patients with indeterminant colitis were excluded from the analyses. Logistic regression models were built to obtain odds ratios (OR) with their corresponding 95% confidence intervals (95%CI) and considering potential confounders.

Results

In total, 264 patients were included in the study; 210(79.5%) diagnosed &lt;60 and 54(20.5%) ≥ 60. The mean age of diagnosis was 47.21(SD=16.18), [&lt;60=41.69(SD=13.25), ≥60=68.00(SD=6.264)].Cross tabulation (Table 2) of age of diagnosis and patient’s characteristics (sex, IBD type, and clinical remission at last visit, current use of biologics and steroids) confirmed lack of inter-variable significance. However, in the same analysis individuals diagnosed ≥ 60 were more likely to be on 5-ASA therapy compared to their counterparts diagnosed before the age of 60. Logistic regression model results demonstrated that: Patients diagnosed ≥ 60 years were 2.06 (1.12–3.80, 95% CI) times more likely to be using 5-ASA therapy.Patients in clinical remission were 3.04 (95% CI, 1.65–5.61) times more likely to be using biologic therapy.

Conclusions

Thus far, the results indicate significant correlation between use of 5-ASA in patients diagnosed age ≥60. In the same cohort, clinical remission was also linked to current use of biologics agents. On further analysis, with data stratification based on type of IBD, the same significance did not hold true, likely associated with low power within the stratified group. Clinical remission with those diagnosed ≥60 years while on biologics treatment, may reflect the specific disease type and inflammatory pathways responsible for second wave of IBD diagnosis in later ages.Patients diagnosed later in life were less likely to have IBD-related hospitalization or surgery, likely a reflection of shorted disease history.

Funding Agencies

NoneNone

A19 HEALTH CARE UTILIZATION DIFFERENCES BETWEEN FIRST NATIONS AND THE GENERAL POPULATION WITH INFLAMMATORY BOWEL DISEASE IN SASKATCHEWAN

Background

Indigenous patients with inflammatory bowel disease (IBD) have expressed concerns about barriers to access IBD care. The limited evidence of IBD among Indigenous people highlights the need for studies evaluating access to IBD care in this population.

Aims

We aimed to compare health care utilization between First Nations (FNs) and individuals from the general population (GP) diagnosed with IBD in Saskatchewan (SK).

Methods

A population-based retrospective cohort study was conducted using administrative health databases of SK from 1998 to 2017 fiscal years. As a patient-oriented research initiative, outcomes of interest were chosen in collaboration with Indigenous patients and family advocates. A validated algorithm requiring multiple health care contacts was applied to identify incident IBD cases. The self-declared FN status variable was used to divide IBD cases between FNs and the general population (GP). To balance the groups, 1:5 age and sex matching was applied. Cox-proportional models were used to estimate hazard ratios (HRs) and 95% confidence intervals (95%CI). Stratified analysis was completed for those diagnosed before and after 2008 (pre- and post-biologic eras).

Results

A matched cohort with 696 IBD incident cases was created (FN=116, GP=580). Comparing health care utilization of FNs and individuals from the GP with IBD, there were no statistically significant differences in outpatient gastroenterology visits (FNs=81.0%, GP=83.6%), colonoscopies (FNs=91.4%, GP=86.9%), and surgeries for IBD (FNs=31.0%, GP=33.5%). We observed differences in prescription claims for any medication for IBD (FNs=79.3%, GP=89.3%) and 5-aminosalicylic acid (5-ASA) claims (FNs=75.9%, GP=81.4%). The HRs adjusted by rural/urban residence and diagnostic type showed differences in prescription claims for any IBD medication (HR=0.52, 95%CI 0.41–0.65) and 5-ASA (HR=0.57, 95%CI 0.45–0.72). In the pre-biologic era, FNs had a lower risk of having a prescription claim for any IBD medication (HR=0.32, 95%CI 0.23–0.45) and 5-ASA (HR=0.33, 95%CI 0.24–0.47), respectively. These differences were not significant in the post-biologic era.

Conclusions

Our study identified an inverse association between FN status and having prescription medication claims for IBD in SK. We considered multiple confounding variables when evaluating this association but could not control by disease severity. Thus, this association might reflect a barrier to access IBD medications or that FNs with IBD might present a milder disease. Further studies should continue evaluating access to IBD care, medication use, and disease severity among FNs living with IBD.

Funding Agencies

Saskatchewan Centre for Patient-Oriented Research (SCPOR), Saskatchewan Health Research Foundation (SHRF), and College of Medicine, University of Saskatchewan.

Correction to: In Vitro to In Vivo Extrapolation of Metabolic Clearance for UGT Substrates Using Short-Term Suspension and Long-Term Co-cultured Human Hepatocytes

During production, the figure captions for Fig. 1 and Fig. 2 were inadvertently switched in the proofing stage.

Characterization of the Ontogeny of Hepatic UDP-Glucuronosyltransferase Enzymes Based on Glucuronidation Activity Measured in Human Liver Microsomes

An understanding of the postnatal development of hepatic UDP-glucuronosyltransferase (UGT) enzymes is required for accurate prediction of the age-dependent changes in pharmacokinetics of many drugs used in children. However, the maturation rate of hepatic UGT isoforms remains a major knowledge gap. This study aimed to establish the age-associated changes in glucuronidation activity of 10 major hepatic UGT isoforms in humans, namely, UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B4, UGT2B7, UGT2B10, UGT2B15, and UGT2B17. Human liver microsomes from pediatric and adult donors were incubated under optimized incubation conditions to assess the activity rates of hepatic UGT isoforms using a panel of 19 in vitro UGT probe substrates and clinically used drugs. Statistically strong correlations of glucuronidation activities allowed the ontogeny of UGT1A1, UGT1A4, UGT2B7, UGT2B10, and UGT2B15 to be established using multiple selective UGT substrates and matched human liver microsome samples. The postnatal development of hepatic UGTs is isoform-dependent using either individual or cross-correlated selective isoform substrates. Maximal adult activity was reached at different times ranging from within a month (UGT1A1, UGT2B4, UGT2B7, UGT2B10, and UGT2B15), during infancy (UGT1A3, UGT1A4, and UGT1A9), to adolescence (UGT1A6 and UGT2B17). This study provides an extensive characterization of the postnatal ontogeny profiles of hepatic UGT enzymes that are instrumental for predicting drug disposition via in vitro-in vivo extrapolation algorithms and verifying pharmacokinetic predictions against in vivo observations via pediatric physiologically based pharmacokinetic modeling in pediatric patients.

Application of the Extended Clearance Classification System (ECCS) in Drug Discovery and Development: Selection of Appropriate In Vitro Tools and Clearance Prediction

In vitro to in vivo extrapolation (IVIVE) to predict human hepatic clearance, including metabolism and transport, requires extensive experimental resources. In addition, there may be technical challenges to measure low clearance values. Therefore, prospective identification of rate-determining step(s) in hepatic clearance through application of the Extended Clearance Classification System (ECCS) could be beneficial for optimal compound characterization. IVIVE for hepatic intrinsic clearance (CLint,h) prediction is conducted for a set of 36 marketed drugs with low-to-high in vivo clearance, which are substrates of metabolic enzymes and active uptake transporters in the liver. The compounds were assigned to the ECCS classes, and CLint,h, estimated with HepatoPac (a micropatterned hepatocyte coculture system), was compared with values calculated based on suspended hepatocyte incubates. An apparent permeability threshold (apical to basal) of 50 nm/s in LLC-PK1 cells proved optimal for ECCS classification. A reasonable performance of the IVIVE for compounds across multiple classes using HepatoPac was achieved (with 2-3-fold error), except for substrates of uptake transporters (class 3b), for which scaling of uptake clearance using plated hepatocytes is more appropriate. Irrespective of the ECCS assignment, metabolic clearance can be estimated well using HepatoPac. The validation and approach elaborated in the present study can result in proposed decision trees for the selection of the optimal in vitro assays guided by ECCS class assignment, to support compound optimization and candidate selection. SIGNIFICANCE STATEMENT: Characterization of the rate-determining step(s) in hepatic elimination could be on the critical path of compound optimization during drug discovery. This study demonstrated that HepatoPac and plated hepatocytes are suitable tools for the estimation of metabolic and active uptake clearance, respectively, for a larger set of marketed drugs, supporting a comprehensive strategy to select optimal in vitro tools and to achieve Extended Clearance Classification System-dependent in vitro to in vivo extrapolation for human clearance prediction.

The Ontogeny of UDP-glucuronosyltransferase Enzymes, Recommendations for Future Profiling Studies and Application Through Physiologically Based Pharmacokinetic Modelling

Limited understanding of drug pharmacokinetics in children is one of the major challenges in paediatric drug development. This is most critical in neonates and infants owing to rapid changes in physiological functions, especially in the activity of drug-metabolising enzymes. Paediatric physiologically based pharmacokinetic models that integrate ontogeny functions for cytochrome P450 enzymes have aided our understanding of drug exposure in children, including those under the age of 2 years. Paediatric physiologically based pharmacokinetic models have consequently been recognised by the European Medicines Agency and the US Food and Drug Administration as innovative tools in paediatric drug development and regulatory decision making. However, little is currently known about age-related changes in UDP-glucuronosyltransferase-mediated metabolism, which represents the most important conjugation reaction for xenobiotics. Therefore, the objective of the review was to conduct a thorough literature survey to summarise our current understanding of age-related changes in UDP-glucuronosyltransferases as well as associated clinical and experimental sources of variance. Our findings indicate that there are distinct differences in UDP-glucuronosyltransferase expression and activity between isoforms for different age groups. In addition, there is substantial variability between individuals and laboratories reported for human liver microsomes, which results in part from a lack of standardised experimental conditions. Therefore, we provide a number of best practice recommendations for experimental conditions, which ultimately may help improve the quality of data used for quantitative clinical pharmacology approaches, and thus for safe and effective pharmacotherapy in children.

Use of Phenotypically Poor Metabolizer Individual Donor Human Liver Microsomes To Identify Selective Substrates of UGT2B10

UDP-glucuronosyltransferase (UGT)1A4 and UGT2B10 are the human UGT isoforms most frequently involved in N-glucuronidation of drugs. UGT2B10 exhibits higher affinity than UGT1A4 for numerous substrates, making it potentially the more important enzyme for metabolism of these compounds in vivo. Clinically relevant UGT2B10 polymorphisms, including a null activity splice site mutation common in African populations, can lead to large exposure differences for UGT2B10 substrates that may limit their developability as marketed drugs. UGT phenotyping approaches using recombinantly expressed UGTs are limited by low enzyme activity and lack of validation of scaling to in vivo. In this study, we describe the use of an efficient experimental protocol for identification of UGT2B10-selective substrates (i.e., those with high fraction metabolized by UGT2B10), which exploits the activity difference between pooled human liver microsomes (HLM) and HLM from a phenotypically UGT2B10 poor metabolizer donor. Following characterization of the approach with eight known UGT2B10 substrates, we used ligand-based virtual screening and literature precedents to select 24 potential UGT2B10 substrates of 140 UGT-metabolized drugs for testing. Of these, dothiepin, cidoxepin, cyclobenzaprine, azatadine, cyproheptadine, bifonazole, and asenapine were indicated to be selective UGT2B10 substrates that have not previously been described. UGT phenotyping experiments and tests comparing conjugative and oxidative clearance were then used to confirm these findings. These approaches provide rapid and sensitive ways to evaluate whether a potential drug candidate cleared via glucuronidation will be sensitive to UGT2B10 polymorphisms in vivo. SIGNIFICANCE STATEMENT: The role of highly polymorphic UDP-glucuronosyltransferase (UGT)2B10 is likely to be underestimated currently for many compounds cleared via N-glucuronidation due to high test concentrations often used in vitro and low activity of UGT2B10 preparations. The methodology described in this study can be combined with the assessment of UGT versus oxidative in vitro metabolism to rapidly identify compounds likely to be sensitive to UGT2B10 polymorphism (high fraction metabolized by UGT2B10), enabling either chemical modification or polymorphism risk assessment before candidate selection.

A60 THE INCIDENCE OF INFLAMMATORY BOWEL DISEASE IS DECREASING IN SASKATCHEWAN: A POPULATION-BASED COHORT STUDY

Background

Canada has one of the highest inflammatory bowel disease (IBD) incidence rates worldwide, although within Canada rates vary. Evidence show increasing incidence rates of IBD in Ontario (i.e. adults aged 30–60), stable in Alberta and decreasing in Manitoba. Additionally, higher incident rates of IBD have been identified among urban regions compared to rural regions. There is limited data on the incidence of IBD in Saskatchewan.

Aims

The study objectives were to 1) estimate IBD incidence rates in Saskatchewan from 1999 to 2016, and 2) test for differences in IBD incidence rates for rural and urban regions of Saskatchewan.

Methods

A population-based study was conducted using linked provincial administrative health databases. Individuals age 18+ old with newly diagnosed Crohn’s disease (CD) or ulcerative colitis (UC) were identified using a validated case definition. Generalized linear models with a negative binomial distribution were used to estimate incidence rates and incidence rate ratios (IRR) adjusted for age group, sex, and rurality with 95% confidence intervals (95%CI).

Results

In total, 4,908 newly diagnosed individuals with IBD were included. The average annual incidence rate of IBD decreased from 75 (95%CI 67–84) per 100,000 people in 1999 to 15 (95%CI 12–18) per 100,000 population in 2016. This decrease was evident in both UC (from 36/100,000 [95%CI 31–42] in 1999 to 6/100,000 [95%CI 4–8] in 2016) and CD (37/100,000 [95%CI 32–42] in 1999 to 8/100,000 [95%CI 6–10] in 2016). A significant decline of 6.9% (95%CI 6.2–7.6) in the average annual incidence of IBD was estimated between 1999 and 2016 (see Figure 1). Urban residents had a greater overall risk of IBD (IRR=1.19, 95%CI 1.11–1.27) than rural residents. This risk difference was statistically significant for CD (IRR=1.25, 95%CI 1.14–1.36), but not UC (IRR=1.08, 95%CI 0.97–1.19).

Conclusions

A decreasing trend in IBD incidence in Saskatchewan was identified after adjusting for age group, sex, and rural/urban region of residence. Around 150 new cases of IBD are still diagnosed annually in Saskatchewan, but this estimate is lower than estimates from other provinces. Urban dwellers have a 25% higher risk of CD onset compared to their rural counterparts. This finding could suggest the presence of specific risk factors in urban settings that require further investigation. Health care providers and decision-makers should plan IBD-specific health care programs taking into account these specific IBD rates in Saskatchewan.

Funding Agencies

College of Medicine, University of Saskatchewan

A61 FOCUSING ON THE FUTURE: REDUCING BARRIERS AND IMPROVING ACCESS TO IBD SPECIALTY CARE ACROSS CANADA

Background

Canada has the highest global age-adjusted incidence and prevalence rates of Inflammatory Bowel Disease (IBD). Resulting from compounding prevalence and limited resources, timely access to specialty care is a challenge faced by patients and healthcare providers. Despite this issue, there has been no published research elucidating the patient perspective using qualitative approaches to compare and contrast the patient experience across Canada.

Aims

To elicit a qualitative data stream to better understand phenomena related to access to healthcare for Canadians living with IBD from a patient-centered perspective.

Methods

Patients diagnosed with IBD (≥18 years of age) were recruited from gastroenterology clinics and communities through IBD specialists and Crohn’s & Colitis Canada. To ensure geographic diversity and representation, patients were recruited from urban and rural regions. In order to acquire multiple access perspectives, patients were invited to bring a family member who was involved in their care to the focus groups. Co-facilitated by a researcher and a patient research partner, the focus groups were held in Nova Scotia, New Brunswick, Quebec, Ontario, Manitoba, Saskatchewan, and British Columbia. All focus groups were audio recorded, transcribed, and coded for themes. Themes were distilled through qualitative thematic analysis using Atlas.ti software to ascertain congruence or discordance of IBD specialty care access experiences.

Results

A total of 63 participants were recruited in fourteen focus groups across seven provinces. The majority of participants were female (41/63, 65%) and from urban/suburban regions (34/63, 54%). The mean age of participants was 48 years (SD=16 years, range=16 to 77 years). Preliminary analyses illustrated three patient-identified access barrier themes: 1) Lack of multidisciplinary care (psycho-social and nutrition support), 2) Diagnostic delay, and 3) Inability to effectively receive and provide communication with healthcare providers. In response, four solutions were proposed: 1) Integration of holistic care into the clinical practice, 2) Readily accessible psycho-social and nutritional support, 3) Increased patient advocacy, and 4) Continuity and liaison through provision of a healthcare navigator resource.

Conclusions

The complexity of specialty care access for IBD patients in Canada cannot be underestimated. It is vital to possess a robust understanding of healthcare system structures, processes, and the significant impact these factors have on patients and the care received. Through the use of patient-centered exploration of barriers and facilitators, access to IBD specialty care in Canada can be better understood and improved on both a provincial and national scale.

Funding Agencies

CIHRNova Scotia Health Authority Research Fund

A4 A FRAMEWORK TO STUDY INFLAMMATORY BOWEL DISEASE AMONG INDIGENOUS PEOPLES AND PRELIMINARY RESULTS FROM SASKATCHEWAN, CANADA

Background

Inflammatory Bowel Disease (IBD) is a chronic condition with significant life-threatening disease-related complications and reductions in quality of life if left untreated. Despite available research about IBD in the general population, there is limited-to-no evidence about IBD among Indigenous peoples in Canada and around the world.

Aims

We aimed to define a collaborative framework, estimate the prevalence and incidence rates of IBD among First Nations in Saskatchewan, Canada, and explore perceptions of IBD among Indigenous peoples in the province.

Methods

This study began when Indigenous patients shared their health experiences with IBD with research team members. An interdisciplinary research team was formed including Indigenous patient and family advocates (IPFAs, Indigenous patients living with IBD and parents of an Indigenous person with IBD), an IBD gastroenterologist, knowledge users, and Indigenous and non-Indigenous researchers. Our research team committed to raise awareness of IBD among Indigenous peoples within Indigenous communities and among health care providers and to advocate for better healthcare and well-being by providing evidence of IBD among Indigenous peoples living with IBD in Saskatchewan. We defined a mixed methodology. The first phase of the study used Saskatchewan administrative health data to estimate the prevalence and incidence rates with 95% confidence intervals (95%CI) of IBD among First Nations. The second phase of the study will use a photovoice methodology to gather “the voices” of Indigenous peoples with IBD, encouraging self-interpretation of pictures, engaging their communities, and empowering them with the study findings.

Results

The IPFAs play a critical role in the project by sharing their experiences and defining the directions of the project, as well as defining our research framework (Figure 1). Preliminary results show that the prevalence of IBD among First Nations in Saskatchewan increased from 66 (95%CI 65–68) per 100,000 population in 1999 to 148 (95%CI 145–151) per 100,000 people in 2015. In contrast, the incidence rates appear to be stable over time, 11/100,000 (95%CI 4–24) in 1999 and 11/100,000 (95%CI 5–20) in 2015. We started recruiting participants for the photovoice study in September 2019.

Conclusions

This ground-breaking patient-driven study is the first stage to improve health among Indigenous peoples living with IBD in Saskatchewan. This project will generate community-engaged knowledge and expertise to inform the development of an Indigenous IBD framework that could promote better and knowledge-based healthcare for Indigenous peoples with IBD in Canada and worldwide.

Funding Agencies

CIHRSaskatchewan Health Research Foundation (SHRF) and Saskatchewan Centre for Patient-Oriented Research (SCPOR)

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.