Population pharmacokinetic modeling of vedolizumab for graft-versus-host disease prophylaxis in adults with allogeneic hematopoietic stem cell transplant.

We aimed to characterize the population pharmacokinetics (PK) of vedolizumab for acute graft-versus-host disease prophylaxis in adults undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) and assess potential clinically relevant covariates. Dosing, patient characteristics, and PK from a phase 1b, open-label, dose-finding study of vedolizumab 75 mg initial dose escalated to 300 mg and a phase 3 study of vedolizumab 300 mg in patients receiving allo-HSCT were analyzed using a two-compartment population PK model with linear elimination. Covariates included age, race, weight, sex, albumin, lymphocyte count, GvHD type, and concomitant medications. Weight, albumin, and lymphocyte count were time-varying covariates. Model selection was driven by goodness-of-fit criteria, precision of parameter estimates, and visual predictive checks. In 193 patients undergoing allo-HSCT, vedolizumab PK were well described by a two-compartment, linear PK model. Using reference covariate values, final parameter estimates (95% confidence intervals [CI]) were: clearance, 0.148 (0.136, 0.162) L/day; central volume of distribution, 3.12 (3.03, 3.21) L; intercompartmental clearance, 0.500 (0.408, 0.612) L/day; and peripheral volume of distribution, 3.95 (3.52, 4.44) L. Weight and albumin were the most important predictors of vedolizumab PK, with clearance decreasing by ≈20% for low body weight/high albumin and increasing by ≈30% for high body weight/low albumin. There was an inverse relationship between vedolizumab clearance and age, but no detectable effect for lymphocyte count or GvHD type. Post hoc analyses did not detect any relationship between vedolizumab PK and concomitant medications. In summary, the covariates studied did not have a clinically meaningful effect on the PK of vedolizumab.

Subcutaneous versus intravenous infliximab therapy - a real-world study: toward higher drug concentrations.

BACKGROUND: Recently, a formula of subcutaneous infliximab (SC-IFX) has been approved for inflammatory bowel disease (IBD), demonstrating a better pharmacokinetic and immunogenic profiles, compared to intravenous infliximab (IV-IFX), with similar efficacy and safety. AIM: The aim of this study is to evaluate the clinical, biochemical, and pharmacological outcomes of IBD patients in clinical remission, who switched from IV-IFX to SC-IFX, with a follow-up period of 6 months. METHODS: Retrospective cohort study, including IBD patients in clinical remission, previously medicated with IV-IFX, who switched to SC-IFX 120 mg every other week. Biochemical parameters were evaluated before the switch and 6 months after, namely infliximab serum concentrations, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and fecal calprotectin. RESULTS: Included 41 patients in clinical remission, 32 with Crohn's disease (78.0%) and 9 with ulcerative colitis (22.0%). All patients maintained clinical remission during the 6 months after the switch, with a treatment persistence rate of 100%, and no patients requiring corticosteroid therapy, switching back to IV-IFX, or IBD-related hospitalization. The mean infliximab serum concentrations were significantly higher after 6 months of SC-IFX (17.3 ±â€…6.6 vs. 9.1 ±â€…5.5 µg/ml, P  < 0.001). However, there were no differences between values of ESR, CRP, and fecal calprotectin, before and after the switch ( P  = 0.791, P  = 0.246, and P  = 0.639). Additionally, none of the patients developed antibodies to infliximab. CONCLUSION: Switching from IV-IFX to SC-IFX in IBD patients in clinical remission is effective and leads to higher infliximab serum concentrations, regardless of the combination with immunomodulatory therapy.

Treatment Targets Should Influence Choice of Infliximab Dose Intensification Strategy in Inflammatory Bowel Disease: A Pharmacokinetic Simulation Study.

BACKGROUND: The optimal infliximab dose intensification strategy to address loss of response associated with subtherapeutic infliximab trough levels remains uncertain, as does whether post-intensification trough and treatment targets should influence this decision. OBJECTIVES: This pharmacokinetic simulation study aimed to identify infliximab dose intensification strategies capable of achieving post-intensification infliximab trough thresholds associated with clinical and objective treatment targets in Crohn's disease and ulcerative colitis. METHODS: A validated pharmacokinetic infliximab model, applied to 200 simulated patients, identified those with subtherapeutic (< 3.00 mg/L) trough levels after 30 weeks of standard (5 mg/kg 8-weekly) dosing, and subsequently applied 10 dose intensification strategies over a further 32 weeks. The proportion of simulations achieving 32-week post-intensification infliximab trough levels associated with endoscopic remission (ulcerative colitis > 7.50 mg/L, Crohn's disease > 9.70 mg/L) was the primary outcome, with perianal fistula healing (Crohn's disease > 10.10 mg/L) and clinical improvement (ulcerative colitis > 3.70 mg/L, Crohn's disease > 7.00mg/L) evaluated as secondary outcomes. All outcomes were stratified by intensity of dose intensification, with standard (≤ 10 mg/kg 8-weekly or 5 mg/kg 4-weekly; n = 5) and intensive (> 10 mg/kg 8-weekly or 5 mg/kg 4-weekly; n = 5) dosing strategies defined, respectively. RESULTS: The median pre-intensification infliximab trough level was 0.91 mg/L (interquartile range 1.37). Intensive dosing strategies were more likely to achieve infliximab trough concentrations associated with endoscopic remission (ulcerative colitis 36.48% vs. 10.80%, Crohn's disease 25.98 vs. 4.68%), perianal fistula healing (24.52% vs. 4.36%) and clinical improvement (ulcerative colitis 61.90% vs. 34.86%, Crohn's disease 40.32 vs. 12.08%) than standard intensification strategies (all p < 0.01). When controlling for cumulative (mg/kg) infliximab dose over 32 weeks, strategies that concurrently dose increased and interval shortened achieved the highest infliximab trough levels (all p < 0.01). CONCLUSION: This simulation-based analysis highlights the potential of using post-intensification infliximab trough thresholds associated with aspirational treatment targets in Crohn's disease and ulcerative colitis to guide choice of infliximab dose intensification strategy. Intensive dose intensification strategies, particularly those that concurrently dose increase and interval shorten, appear to achieve higher infliximab levels than standard dose intensification strategies. This may be particularly important in the pursuit of stringent endpoints, such as endoscopic remission and fistula healing, which have been consistently associated with higher infliximab trough levels. These findings require validation across real-world cohorts.

Real-life experiences of switching from intravenous to subcutaneous vedolizumab maintenance therapy in patients with inflammatory bowel disease.

BACKGROUND: A few prospective cohort studies support the safety of switching from intravenous to subcutaneous administration of vedolizumab during maintenance therapy in patients with inflammatory bowel disease. Real-life data on switching after intravenous induction therapy are lacking. OBJECTIVE: The aim was to obtain real-world data on subcutaneous vedolizumab treatment in patients with inflammatory bowel disease after switching from intravenous vedolizumab induction or maintenance therapy, and to evaluate treatment persistence, safety, and changes in disease activity and serum vedolizumab concentrations. METHODS: We performed a retrospective registry-based study of inflammatory bowel disease patients who received subcutaneous vedolizumab therapy in two tertiary centres. RESULTS: Altogether, 103 patients (26 Crohn's disease and 77 ulcerative colitis) switching from intravenous maintenance therapy (group 1) and 44 patients (14 and 30, respectively) switching from intravenous induction therapy (group 2) were included. At 6 months from baseline, 90.3% of the patients in group 1 and 90.9% of the patients in group 2 continued on subcutaneous vedolizumab. After the switch in group 1, disease activity remained stable. In group 2, clinical disease activity decreased significantly in ulcerative colitis patients ( P  = 0.002). The median serum vedolizumab concentration was 34.00 µg/ml during subcutaneous maintenance therapy in group 1, which was significantly higher than the median concentration during intravenous therapy (17.00 µg/ml, P  < 0.001), but remained unchanged in group 2 after the switch (31.50 µg/ml). CONCLUSION: Based on these data, subcutaneous vedolizumab treatment is well-tolerated and the treatment persistence remains high after switching from intravenous to subcutaneous vedolizumab therapy.

Population Pharmacokinetic and Exposure-Response Modeling to Inform Risankizumab Dose Selection in Patients With Ulcerative Colitis.

Data from phase IIb/III and phase III studies were used to characterize the population pharmacokinetics of risankizumab and its exposure-response relationships for efficacy and safety in ulcerative colitis (UC) patients. A two-compartment model with first-order absorption and elimination accurately described risankizumab pharmacokinetics. Although certain covariates, namely, body weight, serum albumin, fecal calprotectin, sex, corticosteroid use, advanced therapy inadequate response, and pancolitis, were statistically correlated with risankizumab clearance, their impact on exposure was not clinically meaningful for efficacy or safety. Phase II exposure-response analyses demonstrated that the 1,200 mg intravenous (IV) induction dose at Weeks 0, 4, and 8 achieved near maximal response for all efficacy end points, with suboptimal efficacy from the 600 mg and little added benefit from the 1,800 mg regimens, justifying 1,200 mg IV as the induction dose in the phase III study. Phase III exposure-response analyses for efficacy during induction showed statistically significant exposure-response relationships at Week 12 following 1,200 mg IV at Weeks 0, 4, and 8, in line with phase IIb results. Exposure-response analyses for maintenance demonstrated modest improvement in Week 52 efficacy when increasing the subcutaneous dose from 180 mg to 360 mg with largely overlapping confidence intervals. Exposure-response analyses for safety indicated no apparent exposure-dependent safety events over the induction or maintenance treatment. Based on these results, the recommended dosing regimen for risankizumab in UC patients is 1,200 mg IV at Weeks 0, 4, and 8, followed by 180 mg or 360 mg subcutaneously at Week 12 and every 8 weeks thereafter.

Infliximab in paediatric inflammatory bowel disease: External evaluation of population pharmacokinetic models.

AIMS: Use of infliximab (IFX) has improved outcomes in children with inflammatory bowel disease (IBD). However, a proportion of patients does not respond to IFX or loses response over time. Population pharmacokinetic (PopPK) modelling is a promising approach for IFX dose optimization, but with the increasing number of PopPK models in literature, model evaluation is essential. The aims of this study are: (i) to validate the predictive performance of existing IFX PopPK models using a cohort of children with IBD; and (ii) to perform a Bayesian estimation of the most suitable model to predict the next IFX concentrations. METHODS: PubMed was searched for IFX PopPK models in children. Selected models were rebuilt and analysed using R. Model performance was assessed through goodness-of-fit-plots, residuals against time, prediction error and prediction-corrected visual predictive checks. The validation cohort consisted of 73 children with IBD who were treated with IFX in our centre between 2017 and 2023 (340 IFX measurements). RESULTS: We identified 9 PopPK models. Model bias for individual predicted values ranged from -9.29% to 8.01% compared to bias for population predicted values. The model by Vande Casteele et al. demonstrated superior performance (individual predicted bias 2.13, population predicted bias -6.11); upon Bayesian estimation, it predicted induction trough levels with median error of 12.95% but had a median error of -69% predicting maintenance concentrations. CONCLUSION: The model by Vande Casteele et al. displayed superior performance in initial evaluations but had a high error in estimating next IFX levels and can only be used in practice to predict induction levels.

Mirikizumab Exposure-Response Relationships in Patients with Moderately-to-Severely Active Ulcerative Colitis in Randomized Phase II and III Studies.

Mirikizumab is a humanized anti-interleukin-23p19 monoclonal antibody being developed for ulcerative colitis (UC) and Crohn's disease. We characterized the relationship of mirikizumab systemic exposure with efficacy and safety end points in patients with UC using phase II (NCT02589665) and III (NCT03518086, NCT03524092) trial data. Exposure-response models were developed for clinical remission, clinical response, endoscopic remission, and change in modified Mayo score following induction (50-1,000 mg i.v. every 4 weeks) and maintenance (200 mg s.c. every 4 or 12 weeks) treatment. These models evaluated observed and pharmacokinetic model-predicted mirikizumab exposures as the exposure measure. Key safety event rates were compared across mirikizumab exposure quartiles in the phase III trial. Mirikizumab efficacy in patients with UC showed an apparent positive association with systemic exposure following both induction and maintenance. However, further analysis found this relationship to be overstated by the presence of confounding factors that were not among the tested patient covariates. While prior biologic experience and baseline disease severity showed statistically significant influences on estimated placebo effect, no patient factors affected the mirikizumab effect parameters in any of the phase III exposure-response models. There was no apparent mirikizumab concentration relationship with any adverse event of special interest. When the phase II and III data and confounding are considered together, efficacy was unlikely to be strongly affected by variation in exposures across individual patients at the phase III dose. Together with the previously demonstrated mirikizumab exposure insensitivity to patient factors, these findings indicate that mirikizumab dose adjustment to patient characteristics is not required.

Pharmacogenetics in IBS: update and impact of GWAS studies in drug targets and metabolism.

INTRODUCTION: Medications are frequently prescribed for patients with irritable bowel syndrome (IBS) or disorders of gut brain interaction. The level of drug metabolism and modifications in drug targets determine medication efficacy to modify motor or sensory function as well as patient response outcomes. AREAS COVERED: The literature search included PubMed searches with the terms: pharmacokinetics, pharmacogenomics, epigenetics, clinical trials, irritable bowel syndrome, disorders of gut brain interaction, and genome-wide association studies. The main topics covered in relation to irritable bowel syndrome were precision medicine, pharmacogenomics related to drug metabolism, pharmacogenomics related to mechanistic targets, and epigenetics. EXPERT OPINION: Pharmacogenomics impacting drug metabolism [CYP 2D6 (cytochrome P450 2D6) or 2C19 (cytochrome P450 2C19)] is the most practical approach to precision medicine in the treatment of IBS. Although there are proof of concept studies that have documented the importance of genetic modification of transmitters or receptors in altering responses to medications in IBS, these principles have rarely been applied in patient response outcomes. Genome-wide association (GWAS) studies have now documented the association of symptoms with genetic variation but not the evaluation of treatment responses. Considerably more research, particularly focused on patient response outcomes and epigenetics, is essential to impact this field in clinical medicine.

Forecasted infliximab concentrations during induction predict time to remission and sustained disease control of inflammatory bowel disease.

BACKGROUND: Infliximab (IFX) exposure is established as a predictive factor of pharmacokinetic (PK) origin in inflammatory bowel disease (IBD), and expert consensus is to achieve adequate exposure during induction to achieve and sustain remission. METHODS: We retrospectively evaluated the performance of a Bayesian PK tool in IBD patients starting IFX. Trough IFX serum levels collected immediately before the third (at week 6) and fourth (at week 14) infusions were evaluated from 307 IBD patients (median age=17 years, 50 % females, 83 % with Crohn's disease). Forecasted IFX concentration at the fourth infusion were estimated using serum IFX, antibodies to IFX, albumin and weight determined immediately before the third infusion using population PK calculator with Bayesian prior. The outcome variable was a clinical & biochemical remission status achieved (CRP levels below 3 mg/L in presence of clinical remission). Statistics consisted of Kaplan Meier analysis with calculation of Hazard ratio (HR), and logistic regression. RESULTS: IFX concentration above 15 µg/mL immediately before the third infusion associated with shorter time to clinical & biochemical remission than concentration below 15 µg/mL without reaching significance (163±14 days vs 200±16 days, respectively; p=0.052). However, using PK parameters at the third infusion, forecasted IFX concentrations above 10 µg/mL immediately before the fourth infusion were significantly associated with a higher rate (HR=1.6 95 %CI: 1.1 to 2.1 p<0.01) and shorter time to remission (148±18 days vs 200±13 days p<0.01). In the presence of IFX concentration above 15 µg/mL at the third infusion, there was a significant 2.5-fold higher likelihood of sustained clinical & biochemical remission status during maintenance as compared to IFX concentrations below 15 µg/mL (p<0.01). Forecasted IFX level above 10 µg/mL at fourth infusion associated with significantly 3.9-fold higher likelihood of clinical & biochemical remission as compared to forecasted IFX concentrations below 10 µg/mL (p<0.01). CONCLUSIONS: These data further support that optimized IFX concentrations during induction are associated with enhanced disease control in IBD.

Fluorescently labelled vedolizumab to visualise drug distribution and mucosal target cells in inflammatory bowel disease.

OBJECTIVE: Improving patient selection and development of biological therapies such as vedolizumab in IBD requires a thorough understanding of the mechanism of action and target binding, thereby providing individualised treatment strategies. We aimed to visualise the macroscopic and microscopic distribution of intravenous injected fluorescently labelled vedolizumab, vedo-800CW, and identify its target cells using fluorescence molecular imaging (FMI). DESIGN: Forty three FMI procedures were performed, which consisted of macroscopic in vivo assessment during endoscopy, followed by macroscopic and microscopic ex vivo imaging. In phase A, patients received an intravenous dose of 4.5 mg, 15 mg vedo-800CW or no tracer prior to endoscopy. In phase B, patients received 15 mg vedo-800CW preceded by an unlabelled (sub)therapeutic dose of vedolizumab. RESULTS: FMI quantification showed a dose-dependent increase in vedo-800CW fluorescence intensity in inflamed tissues, with 15 mg (153.7 au (132.3-163.7)) as the most suitable tracer dose compared with 4.5 mg (55.3 au (33.6-78.2)) (p=0.0002). Moreover, the fluorescence signal decreased by 61% when vedo-800CW was administered after a therapeutic dose of unlabelled vedolizumab, suggesting target saturation in the inflamed tissue. Fluorescence microscopy and immunostaining showed that vedolizumab penetrated the inflamed mucosa and was associated with several immune cell types, most prominently with plasma cells. CONCLUSION: These results indicate the potential of FMI to determine the local distribution of drugs in the inflamed target tissue and identify drug target cells, providing new insights into targeted agents for their use in IBD. TRIAL REGISTRATION NUMBER: NCT04112212.

Pharmacokinetic considerations for drugs that treat diarrhea-predominant irritable bowel syndrome: what's new?

INTRODUCTION: Irritable bowel syndrome (IBS), which presents a significant healthcare and socioeconomic burden, is one of the main issues in the field of therapy. Hence, it is imperative to tackle this matter by evaluating the safety and efficacy of the available treatments and determining the ideal approach for each patient. AREAS COVERED: We reviewed the pharmacokinetics and safety of pharmacologic interventions administered in diarrhea-predominant IBS (IBS-D) patients. PubMed, Google Scholar and the USFDA databases were searched up to November 2023 to include all updated information on eluxadoline, alosetron, and rifaximin. EXPERT OPINION: The most effective way to treat IBS-D is to focus on managing the most common symptoms. However, healthcare providers face a challenge when it comes to identifying the right treatment for each patient, and the root cause of this is the diversity of IBS-D population. Studies have shown that there are differences in how men and women metabolize drugs, which may lead to gender-specific adverse reactions. Women tend to have higher drug concentrations in their bloodstream and take longer to eliminate them. Therefore, healthcare providers may need to reduce the dosage for female patients. Integrating IBS care into sustainable development efforts can indirectly contribute to achieving SDGs and promote health and well-being for all.

Best Practice for Therapeutic Drug Monitoring of Infliximab: Position Statement from the International Association of Therapeutic Drug Monitoring and Clinical Toxicology.

BACKGROUND: Infliximab, an anti-tumor necrosis factor monoclonal antibody, has revolutionized the pharmacological management of immune-mediated inflammatory diseases (IMIDs). This position statement critically reviews and examines existing data on therapeutic drug monitoring (TDM) of infliximab in patients with IMIDs. It provides a practical guide on implementing TDM in current clinical practices and outlines priority areas for future research. METHODS: The endorsing TDM of Biologics and Pharmacometrics Committees of the International Association of TDM and Clinical Toxicology collaborated to create this position statement. RESULTS: Accumulating data support the evidence for TDM of infliximab in the treatment of inflammatory bowel diseases, with limited investigation in other IMIDs. A universal approach to TDM may not fully realize the benefits of improving therapeutic outcomes. Patients at risk for increased infliximab clearance, particularly with a proactive strategy, stand to gain the most from TDM. Personalized exposure targets based on therapeutic goals, patient phenotype, and infliximab administration route are recommended. Rapid assays and home sampling strategies offer flexibility for point-of-care TDM. Ongoing studies on model-informed precision dosing in inflammatory bowel disease will help assess the additional value of precision dosing software tools. Patient education and empowerment, and electronic health record-integrated TDM solutions will facilitate routine TDM implementation. Although optimization of therapeutic effectiveness is a primary focus, the cost-reducing potential of TDM also merits consideration. CONCLUSIONS: Successful implementation of TDM for infliximab necessitates interdisciplinary collaboration among clinicians, hospital pharmacists, and (quantitative) clinical pharmacologists to ensure an efficient research trajectory.

Combination Therapy With Guselkumab and Golimumab in Patients With Moderately to Severely Active Ulcerative Colitis: Pharmacokinetics, Immunogenicity and Drug-Drug Interactions.

A proof-of-concept study with the combination of guselkumab and golimumab in patients with ulcerative colitis (UC) has shown that the combination therapy resulted in greater efficacy than the individual monotherapies. The current analysis evaluated the pharmacokinetics (PK) and immunogenicity of guselkumab and golimumab in both the combination therapy and individual monotherapies. Blood samples were collected to evaluate serum concentrations and immunogenicity of guselkumab and golimumab. Population PK (PopPK) models were developed to assess the effects of combination therapy and other potential covariates on the PK of guselkumab and golimumab. The guselkumab PK was comparable between monotherapy and combination therapy, whereas golimumab concentrations were slightly higher with combination therapy. The anti-guselkumab antibody incidence was low with both monotherapy and combination therapy, and guselkumab immunogenicity did not impact the clearance. Conversely, the anti-golimumab antibody incidence with combination therapy was lower than that for monotherapy. PopPK analysis suggested that the slightly higher golimumab concentrations with combination therapy were partially due to lower immunogenicity and thus lower clearance with combination therapy. C-reactive protein (CRP) was also a significant covariate on golimumab clearance. The greater improvement of inflammation with combination therapy, as shown by reductions in CRP, may have also contributed to the higher golimumab concentrations. Combination therapy slightly decreased the clearance of golimumab, but not guselkumab clearance, in patients with UC. Lower immunogenicity and greater improvement of inflammation with combination therapy were potential mechanisms for slightly increased golimumab concentrations with combination therapy as compared with golimumab monotherapy.

The Effect of Polymorphisms and Other Biomarkers on Infliximab Exposure in Paediatric Inflammatory Bowel Disease: Development of a Population Pharmacokinetic Model.

BACKGROUND: Therapeutic drug monitoring (TDM) of infliximab has been shown to be a effective strategy for inflammatory bowel disease (IBD). Population pharmacokinetic (PopPK) modeling can predict trough concentrations for individualized dosing. OBJECTIVE: The aim of this study was to develop a PopPK model of infliximab in a paediatric population with IBD, assessing the effect of single nucleotide polymorphisms (SNPs) and other biomarkers on infliximab clearance. METHODS: This observational and ambispective single-centre study was conducted in paediatric patients with IBD treated with infliximab between July 2016 and July 2022 in the Paediatric Gastroenterology Service of the Hospital Universitari Vall d'Hebron (HUVH) (Spain). Demographic, clinical, and analytical variables were collected. Twenty SNPs potentially associated with variations in the response to infliximab plasma concentrations were analysed. infliximab serum concentrations and antibodies to infliximab (ATI) were determined by ELISA. PopPK modelling was performed using nonlinear mixed-effects analysis (NONMEM). RESULTS: Thirty patients (21 males) were included. The median age (range) at the start of infliximab treatment was 13 years (16 months to 16 years). A total of 190 samples were obtained for model development (49 [25.8%] during the induction phase). The pharmacokinetics (PK) of infliximab were described using a two-compartment model. Weight, erythrocyte sedimentation rate (ESR), faecal calprotectin (FC), and the SNP rs1048610 (ADAM17) showed statistical significance for clearance (CL), and albumin for inter-compartmental clearance (Q). Estimates of CL1 (genotype 1-AA), CL2 (genotype 2-AG), CL3 (genotype 3-GG), Q, Vc, and Vp (central and peripheral distribution volumes) were 0.0066 L/h/46.4 kg, 0.0055 L/h/46.4 kg, 0.0081 L/h/46.4 kg, 0.0029 L/h/46.4 kg, 0.6750 L/46.4 kg, and 1.19 L/46.4 kg, respectively. The interindividual variability (IIV) estimates for clearance, Vc, and Vp were 19.33, 16.42, and 36.02%, respectively. CONCLUSIONS: A popPK model utilising weight, albumin, FC, ESR, and the SNP rs1048610 accurately predicted infliximab trough concentrations in children with IBD.

Performance of Eight Infliximab Population Pharmacokinetic Models in a Cohort of Dutch Children with Inflammatory Bowel Disease.

BACKGROUND AND OBJECTIVE: Efficacy of infliximab in children with inflammatory bowel disease can be enhanced when serum concentrations are measured and further dosing is adjusted to achieve and maintain a target concentration. Use of a population pharmacokinetic model may help to predict an individual's infliximab dose requirement. The aim of this study was to evaluate the predictive performance of available infliximab population pharmacokinetic models in an independent cohort of Dutch children with inflammatory bowel disease. METHODS: In this retrospective study, we used data of 70 children with inflammatory bowel disease (443 infliximab concentrations) to evaluate eight models that focused on infliximab pharmacokinetic models in individuals with inflammatory bowel disease, preferably aged ≤ 18 years. Predictive performance was evaluated with prior predictions (based solely on patient-specific covariates) and posterior predictions (based on covariates and infliximab trough concentrations). Model accuracy and precision were calculated with relative bias and relative root mean square error and we determined the classification accuracy at the trough concentration target of ≥ 5 mg/L. RESULTS: The population pharmacokinetic model by Fasanmade was identified to be most appropriate for the total dataset (relative bias before/after therapeutic drug monitoring: -20.7%/11.2% and relative root mean square error before/after therapeutic drug monitoring: 84.1%/51.6%), although differences between models were small and several were deemed suitable for clinical use. For the Fasanmade model, sensitivity and specificity for maximum posterior predictions for the next infliximab trough concentration to be ≥ 5 mg/L were respectively 83.5% and 80% with an area under the receiver operating characteristic curve of 0.870. CONCLUSIONS: In our paediatric cohort, various models provided acceptable predictive performance, with the Fasanmade model deemed most suitable for clinical use. Model-informed precision dosing can therefore be expected to help to maintain infliximab trough concentrations in the target range.

A Gastroenterologist's guide to drug interactions of small molecules for inflammatory bowel disease.

Small molecule drugs are becoming increasingly used in the treatment of inflammatory bowel diseases (IBD). However, unlike monoclonal antibody drugs, which have few interactions with other medications, the pharmacokinetics of small molecule drugs are complex and may be influenced by a myriad of drug-drug interactions (DDI) as well as by patient characteristics and food intake. This review aims to provide a concise practical guide to small molecule drug interactions for the use of IBD physicians. It starts with a brief overview of the main metabolizing enzymes and transporters involved in drug interactions and the Food and Drug Administration's (FDA) approach to determining drug-interaction hazard thresholds. It is then followed by a more detailed review of the pharmacokinetics of five novel small molecules approved in IBD: Tofacitinib, Upadacitinib, Filgotinib, Ozanimod, and Etrasimod, including their known interactions and specific warnings. This review will also inform readers on challenges in determining the actual magnitude of interactions and their clinical relevance, including the arbitrary nature of some hazard thresholds, the inference of the impact on metabolizing enzymes and transporters from single-drug assays which may not reflect poly-pharmaceutical regimens, and other challenges in this field which the IBD physician needs to be cognizant of. In practice, before administering a small molecule drug, it is advisable to evaluate any potential interactions with other medications the patient is receiving. An increased awareness by health care professionals and patients, may reduce the possible risks associated with DDI of small molecule IBD drugs.

Therapeutic drug monitoring of vedolizumab therapy in inflammatory bowel disease.

BACKGROUND: Therapeutic drug monitoring is effective for optimizing anti-tumor necrosis factor therapies in inflammatory bowel disease, but for vedolizumab, a gut-selective leucocyte migration inhibitor, data are scarce. METHODS: Observational cohort study including 116 bio-experienced inflammatory bowel disease patients treated with vedolizumab for active luminal disease. Biobanked trough blood samples (n = 676) covering 96% of patients were analyzed using a drug-binding immunofluorometric assay. Steroid-free treatment outcomes were classified by clinical disease activity indices and objective findings, primarily endoscopy. RESULTS: Patients with clinical remission to vedolizumab induction therapy (37%) had significantly higher trough levels than those without at weeks 6 (mean 34.1 vs 28.0 µg/mL, P = 0.03) and 10 (34.8 vs 27.5 µg/mL, P = 0.01). Optimal thresholds for discrimination were 32.4 µg/mL (AUCROC 0.66, P = 0.04) and 23.5 (AUCROC 0.67, P = 0.01), respectively. This positive association persisted during maintenance phase with 11.9 µg/mL (AUCROC 0.69, P < 0.01) associated with clinical remission (37%) and 15.3 (AUCROC 0.74, P < 0.001) for objective remission (46%). Stratification by temporal evolution of treatment effects revealed higher induction and maintenance vedolizumab levels in persistent and slow responders as compared to secondary or persistent failures. Pharmacokinetics was influenced by rare formation of anti-vedolizumab antibodies (2%), and to a lesser extent gender and albumin during induction, but not disease severity, concomitant steroids, or thiopurine metabolites. Switching to subcutaneous administrations resulted in 2.3-fold increase in steady-state trough levels. CONCLUSION: Our study supports maintaining adequate drug exposure being essential for sustained positive outcomes of vedolizumab and emphasizes individualized, therapeutic drug monitoring-based treatment regimens. Controlled trials and pharmacokinetic modeling are, however, needed.

Switching from intravenous to subcutaneous infliximab maintenance therapy in inflammatory bowel disease: Post hoc longitudinal analysis of a randomized trial.

BACKGROUND: Pharmacokinetic non-inferiority of subcutaneous (SC) to intravenous (IV) CT-P13 maintenance therapy was demonstrated in a randomized trial (NCT02883452). This post hoc analysis evaluated longitudinal clinical outcomes with the two infliximab treatment strategies. METHODS: Patients with Crohn's disease or ulcerative colitis received CT­P13 IV loading doses (5 mg/kg; Week [W] 0 and W2) before randomization (1:1) to receive CT-P13 SC (body weight-based dosing every 2 weeks [Q2W]; W6-54; 'SC maintenance group') or CT­P13 IV (5 mg/kg Q8W; W6-22) then CT-P13 SC (Q2W; W30-54; 'IV-to-SC switch group'). Paired W30/W54 patient-level data were analyzed. RESULTS: Fifty-three (IV-to-SC switch) and fifty-nine (SC maintenance) patients were analyzed. Median trough serum CT-P13 concentrations were significantly higher at W54 versus W30 in the IV-to-SC switch group (20.4 versus 2.3 µg/mL; p < 0.00001), while remaining consistent in the SC maintenance group. Statistically significant improvements in pharmacokinetics, efficacy, fecal calprotectin levels, and quality of life were seen following switch to SC administration at W30 in the IV-to-SC switch group; safety findings were similar pre- and post-switch. CONCLUSION: Formulation switching from IV to SC infliximab maintenance therapy was well tolerated and may provide additional clinical improvements. Findings require confirmation in larger prospective studies.

The Influence of Subclinical Active Inflammation on IFX Pharmacokinetic Modeling and Disease Progression Assessment: Findings from a Prospective Real-World Study in Inflammatory Bowel Disease Patients.

BACKGROUND AND AIMS: Effective management of inflammatory bowel disease (IBD) relies on a comprehensive understanding of infliximab (IFX) pharmacokinetics (PK). This study's primary goal was to develop a robust PK model, identifying key covariates influencing IFX clearance (CL), while concurrently evaluating the risk of disease progression during the maintenance phase of IBD treatment. METHODS: The multicenter, prospective, real-world DIRECT study was conducted in several care centers, which included 369 IBD patients in the maintenance phase of IFX therapy. A two-compartment population PK model was used to determine IFX CL and covariates. Logistic and Cox regressions were applied to elucidate the associations between disease progression and covariates embedded in the PK model. RESULTS: The PK model included the contributions of weight, albumin, antidrug antibody (ADA), and fecal calprotectin (FC). On average, higher ADA, FC concentration and weight, and lower albumin concentration resulted in higher IFX CL. In the multivariate regression analyses, FC levels influenced the odds of disease progression in the majority of its definitions, when adjusted for several confounding factors. Additionally, alongside FC, both IFX and CL demonstrated a significant impact on the temporal aspect of disease progression. CONCLUSION: In this 2-year real-world study, readily available clinical covariates, notably FC, significantly impacted IFX availability in IBD patients. We demonstrated that subclinical active inflammation, as mirrored by FC or CRP, substantially influenced IFX clearance. Importantly, FC emerged as a pivotal determinant, not only of IFX pharmacokinetics but also of disease progression. These findings underscore the need to integrate FC into forthcoming IFX pharmacokinetic models, amplifying its clinical significance.