Population pharmacokinetic analysis of infliximab in patients with ulcerative colitis

Review article: The pharmacokinetics and pharmacodynamics of drugs used in inflammatory bowel disease treatment

BACKGROUND

The following review is a compilation of the recent advances and knowledge on the behaviour of the most frequently used compounds to treat inflammatory bowel disease in an organism.

RESULTS

It considers clinical aspects of each entity and the pharmacokinetic/pharmacodynamic relationship supported by the use of plasma monitoring, tissue concentrations, and certain aspects derived from pharmacogenetics.

Population pharmacokinetic analysis of certolizumab pegol in patients with Crohn's disease

Certolizumab pegol (CZP), an anti–tumor necrosis factor α agent, is an effective therapy for Crohn's disease (CD). A population pharmacokinetic (PK) analysis of subcutaneously administered CZP was performed using data from 2157 CD patients from 9 separate studies. The aim was to determine which covariates influence the disposition of CZP. The final CZP population PK model consisted of a baseline, first‐order absorption, and 1‐compartment disposition. CZP antibodies were treated as a structural model covariate and caused apparent clearance (CL/F) to increase from 0.685 to 2.74 L/day. Body surface area (BSA) influenced both CL/F and apparent volume of distribution (V/F) in a linear fashion; both parameters increased by more than 53% and 49%, respectively, across the range of BSA measurements in the data. Albumin influenced CZP CL/F in a nonlinear fashion; CL/F decreased from 1.05 to 0.613 L/day with increasing albumin concentrations in antibody‐negative patients. C‐reactive protein (CRP) had a borderline influence and CL/F increased by more than 20% across the range of CRP measurements in the data set. Race had a minor influence on V/F. The determined covariates' impact on CZP disposition may be of clinical utility in CZP therapy of CD patients when the PK/pharmacodynamic relationship becomes available.

Anti-TNF levels and anti-drug antibodies, immunosuppressants and clinical outcomes in inflammatory bowel disease

The anti-tumor necrosis factor-α (TNF) antibodies have revolutionized the management of ulcerative colitis and Crohn's disease. The development of assays to allow for the measurements of serum drug levels and anti-drug antibodies have provided a more objective means of therapeutic decision making, particularly among patients losing response to treatment. Additionally, more evidence is emerging that indicates the relationship between drug levels and response to therapy including clinical response, mucosal healing and sustained remission. The use of combination therapies of the anti-TNF agents and the thiopurine immunosuppressants may also decrease immunogenicity to the anti-TNF agents and potentiate response to therapy. With more evidence emerging evidence of the importance of therapeutic drug levels and anti-drug antibodies, clinicians may be able to better optimize the current arsenal of inflammatory bowel disease therapeutics to achieve greater rates of durable remission and improved quality of life.

Pharmacokinetics and exposure-efficacy relationship of adalimumab in pediatric patients with moderate to severe Crohn's disease: results from a randomized, multicenter, phase-3 study

BACKGROUND

Adalimumab, a fully human monoclonal antibody (IgG1κ) to tumor necrosis factor, has shown benefit in the treatment of inflammatory bowel disease. The purpose of this analysis was to evaluate the pharmacokinetics (PK) and the serum concentration-efficacy relationship of adalimumab in pediatric patients with moderate-to-severe Crohn's disease.

METHODS

The safety, efficacy, and PK of adalimumab was evaluated in a phase-3, randomized, double-blind, 52-week study (IMAgINE-1, N = 192), which had a 4-week open-label induction phase (dose was determined by patient weight) followed by a 48-week double-blind maintenance phase (standard and low-dose arms, drug given every other week). Trough serum adalimumab (baseline, weeks 2, 4, 16, 26, and 52) and anti-adalimumab antibody measurements (baseline, weeks 16, 26, and 52) were collected. Disease activity was assessed using the Pediatric Crohn's Disease Activity Index.

RESULTS

At week 52, adalimumab trough concentrations (mean ± SD) were higher for patients in the standard-dose (9.48 ± 5.61 μg/mL) compared with the low-dose (3.51 ± 2.21 μg/mL) arm. In patients whose doses were increased from every other week to weekly, higher trough concentrations were observed after dose escalation. Higher body weight, baseline C-reactive protein, and lower baseline albumin levels were associated with greater clearance of adalimumab. An exposure (serum concentration)-efficacy relationship was observed, in which higher concentrations of adalimumab were associated with greater rates of remission.

CONCLUSIONS

This study is the first to describe the PK of adalimumab in pediatric patients with moderate-to-severe Crohn's disease. A positive association between serum adalimumab concentration and remission/response was identified.

A panel to predict long-term outcome of infliximab therapy for patients with ulcerative colitis

BACKGROUND & AIMS

Infliximab is effective for patients with refractory ulcerative colitis (UC), but few factors have been identified that predict long-term outcome of therapy. We aimed to identify a panel of markers associated with outcome of infliximab therapy to help physicians make personalized treatment decisions.

METHODS

We collected data from the first 285 patients with refractory UC (41% female; median age, 39 y) treated with infliximab before July 2012 at University Hospitals Leuven, in Belgium. We performed a Cox regression analysis to identify independent factors that predicted relapse-free and colectomy-free survival, and used these factors to create a panel of markers (risk panel).

RESULTS

During a median follow-up period of 5 years, 61% of patients relapsed and 20% required colectomy. Independent predictors of relapse-free survival included short-term complete clinical response (odds ratio [OR], 3.75; 95% confidence interval [CI], 2.35-5.97; P < .001), mucosal healing (OR, 1.87; 95% CI, 1.17-2.98; P = .009), and absence of atypical perinuclear antineutrophil cytoplasmic antibodies (pANCA) (OR, 1.96; 95% CI, 1.23-3.12; P = .005). Independent predictors of colectomy-free survival included short-term clinical response (OR, 7.74; 95% CI, 2.76-21.68; P < .001), mucosal healing (OR, 4.02; 95% CI, 1.16-13.97; P = .028), baseline level of C-reactive protein (CRP) of 5 mg/L or less (OR, 2.95; 95% CI, 1.26-6.89; P = .012), and baseline level of albumin of 35 g/L or greater (OR, 3.03; 95% CI, 1.12-8.22; P = .029). Based on serologic analysis of a subgroup of 112 patients, levels of infliximab greater than 2.5 μg/mL at week 14 of treatment predicted relapse-free survival (P < .001) and colectomy-free survival (P = .034). A risk panel that included levels of pANCA, CRP, albumin, clinical response, and mucosal healing identified patients at risk for UC relapse or colectomy (both P < .001).

CONCLUSIONS

Clinical response and mucosal healing were confirmed as independent predictors of long-term outcome from infliximab therapy in patients with UC. We identified additional factors (levels of pANCA, CRP, and albumin) to create a risk panel that predicts long-term outcomes of therapy. Serum levels of infliximab at week 14 of treatment also were associated with patient outcomes. Our risk panel and short-term serum levels of infliximab therefore might be used to guide therapy.

Effect of preoperative biologic drugs on complications and function after restorative proctocolectomy with primary ileal pouch formation: systematic review and meta-analysis

BACKGROUND

Debate exists concerning the presumed risk of postoperative complications in patients with ulcerative colitis (UC) receiving preoperative infliximab (IFX). Meta-analyses are contrasting because of many confounders included into analysis. Our aim was to determine the impact of IFX on pouch-related postoperative complications in patients with UC undergoing surgery with primary ileal pouch-anal anastomosis.

METHODS

We performed a systematic review to identify studies comparing the outcomes of patients undergoing surgery for UC with or without previous IFX exposure. The primary end points were (1) early ileal pouch-anal anastomosis-related complications after surgery with primary pouch formation and (2) those occurring after ileostomy closure. Secondary end points were the effects of IFX on total, infectious, and noninfectious complications in patients with UC undergoing any type of surgery. Results are reported as pooled odds ratio (OR) with 95% confidence intervals (CIs).

RESULTS

Seven papers, including 162 patients receiving biologics and 468 controls all undergoing primary pouch formation, were included for the primary aim. Patients receiving IFX were more likely developing early (OR = 4.12; 95% CI, 2.37-7.15; P < 0.001) and post-ileostomy closure (OR = 2.27; 95% CI, 1.27-4.05; P = 0.005) ileal pouch-anal anastomosis-related complications. Number needed to harm was calculated to be 5 and 4, respectively. Having received at least 3 IFX effusions increased the risk of early complications (OR = 9.59; 95% CI, 2.92-31.44; P = 0.0002), whereas an interval of <12 weeks since last effusion did not (OR = 2.35; 95% CI, 0.98-5.64; P = 0.06). Meta-analyses of 14 studies reporting on any type of surgery found that IFX showed a trend toward higher total and infectious complications, but no significant differences were observed. Biologics were associated with lower surgical site infection (OR = 0.67; 95% CI, 0.45-0.99; P = 0.04).

CONCLUSIONS

IFX exposure increases early pouch-specific complications and complications after ileostomy closure in UC. Avoiding primary pouch formation could be a prudent approach.

Role for therapeutic drug monitoring during induction therapy with TNF antagonists in IBD: evolution in the definition and management of primary nonresponse

: Primary nonresponse and primary nonremission are important limitations of tumor necrosis factor (TNF) antagonists, occurring in 10% to 40% and 50% to 80% of patients with inflammatory bowel disease, respectively. The magnitude of primary nonresponse differs between phase III clinical trials and cohort studies, indicating differences, e.g., in definition, patient population or blinding. The causes of nonresponse can be attributed to the drug (pharmacokinetics, immunogenicity), the patient (genetics, disease activity), the disease (type, location, severity), and/or the treatment strategy (dosing regimen, combination therapy). Primary nonresponse has been attributed to "non-TNF-driven disease" which is an overly simplified and potentially misleading approach to the problem. Many patients with primary nonresponse could successfully be treated with dose optimization during the induction phase or switching to another TNF antagonist. Therefore, primary nonresponse is frequently not a non-TNF-driven disease. Recent studies from rheumatoid arthritis and preliminary data from inflammatory bowel disease evaluating therapeutic drug monitoring have suggested that early measurement of drug and anti-drug antibody concentrations could help to define primary nonresponse and rationalize patient management of this problem. Moreover, a modeling approach including pharmacological parameters and patient-related covariants could potentially be predictive for response to the treatment. We describe an overview of this evolution in thinking, underpinned by previous findings, and assess the potential role of early measurement of drug and antidrug antibody concentrations in the definition and management of primary nonresponse.

The comparative safety of tumor necrosis factor inhibitors in rheumatoid arthritis: a meta-analysis update of 44 trials

OBJECTIVE

The study objective was to evaluate and update the safety data from randomized controlled trials of tumor necrosis factor inhibitors in patients treated for rheumatoid arthritis.

METHODS

A systematic literature search was conducted from 1990 to May 2013. All studies included were randomized, double-blind, controlled trials of patients with rheumatoid arthritis that evaluated adalimumab, certolizumab pegol, etanercept, golimumab, or infliximab treatment. The serious adverse events and discontinuation rates were abstracted, and risk estimates were calculated by Peto odds ratios (ORs).

RESULTS

Forty-four randomized controlled trials involving 11,700 subjects receiving tumor necrosis factor inhibitors and 5901 subjects receiving placebo or traditional disease-modifying antirheumatic drugs were included. Tumor necrosis factor inhibitor treatment as a group was associated with a higher risk of serious infection (OR, 1.42; 95% confidence interval [CI], 1.13-1.78) and treatment discontinuation due to adverse events (OR, 1.23; 95% CI, 1.06-1.43) compared with placebo and traditional disease-modifying antirheumatic drug treatments. Specifically, patients taking adalimumab, certolizumab pegol, and infliximab had an increased risk of serious infection (OR, 1.69, 1.98, and 1.63, respectively) and showed an increased risk of discontinuation due to adverse events (OR, 1.38, 1.67, and 2.04, respectively). In contrast, patients taking etanercept had a decreased risk of discontinuation due to adverse events (OR, 0.72; 95% CI, 0.55-0.93). Although ORs for malignancy varied across the different tumor necrosis factor inhibitors, none reached statistical significance.

CONCLUSIONS

These meta-analysis updates of the comparative safety of tumor necrosis factor inhibitors suggest a higher risk of serious infection associated with adalimumab, certolizumab pegol, and infliximab, which seems to contribute to higher rates of discontinuation. In contrast, etanercept use showed a lower rate of discontinuation. These data may help guide clinical comparative decision making in the management of rheumatoid arthritis.

Prior response to infliximab and early serum drug concentrations predict effects of adalimumab in ulcerative colitis

BACKGROUND

Data for adalimumab in ulcerative colitis after prior use of infliximab are scarce.

AIMS

To study adalimumab response rates and predictors of response in ulcerative colitis, including drug concentrations.

METHODS

In this single centre cohort study 73 UC patients, previously exposed to infliximab, were assessed for response to adalimumab at weeks 12 and 52. Serum samples prior to week 12 were available and included in multivariate analysis to predict response.

RESULTS

Overall clinical response at week 12 and 52 were 75% and 52%, respectively. Adalimumab was continued without need for dose escalation throughout year 1 in 16 patients, 22 needed dose escalation and 35 discontinued treatment within 1 year. Prior response to infliximab and early serum concentrations correlated with response. Receiver operator characteristic curve analysis yielded optimal adalimumab concentrations of 4.58 μg/mL for week 12 and 7.0 μg/mL for week 52. Independent predictors for response at week 12 were primary response to infliximab [odds ratio (OR) 8.33; 95% confidence interval (CI) 1.8-33.3; P = 0.006] and an adalimumab concentration ≥4.58 μg/mL at week 4 (OR 4.85; 95% CI 1.3-18.6; P = 0.009). Positive predictors for week 52 response were primary response to infliximab (OR 5.2; 95% CI 1.14-23.8; P = 0.034) and adalimumab concentration at week 4 of ≥7 μg/mL (OR 3.56; 95% CI 1.17-10.79; P = 0.025).

CONCLUSION

Prior response to infliximab and high early adalimumab serum concentrations predict week 12 and year 1 responses to adalimumab in ulcerative colitis.

Association between serum concentration of infliximab and efficacy in adult patients with ulcerative colitis

BACKGROUND & AIMS

We analyzed data collected during the Active Ulcerative Colitis Trials (ACT-1 and ACT-2) to assess relationships between serum concentrations of infliximab and outcomes of adults with moderate-to-severe ulcerative colitis.

METHODS

We compared serum concentrations of infliximab with outcomes of 728 patients with moderately-to-severely active ulcerative colitis who participated in ACT-1 or ACT-2; efficacy data were collected at weeks 8, 30, and 54 (for ACT-1 only). Relationships between serum concentration of infliximab and efficacy outcomes were assessed using trend, logistic regression, and receiver operating characteristic curve analyses. We also evaluated factors that affected the relationship between exposure and response.

RESULTS

Median serum concentrations of infliximab at weeks 8, 30, and/or 54 were significantly higher in patients with clinical response, mucosal healing, and/or clinical remission than in patients who did not meet these response criteria. There were statistically significant relationships between quartile of infliximab serum concentration and efficacy at these time points (P < .01). Infliximab therapy was effective for a smaller proportion of patients in the lowest quartile, and these patients had lower serum levels of albumin and a higher incidence of antibodies to infliximab than patients in other quartiles. Although the relationship between exposure to infliximab and response varied among patients, approximate serum concentrations of 41 μg/mL infliximab at week 8 of induction therapy and 3.7 μg/mL at steady-state during maintenance therapy produced optimal outcomes in patients.

CONCLUSIONS

Serum concentrations of infliximab are associated with efficacy in patients with moderate-to-severe ulcerative colitis; however, complex factors determine the relationship between exposure to this drug and response. A prospective evaluation of the value of measuring serum concentrations of infliximab should be performed before these data can be included in patient management strategies. Clinicaltrials.gov numbers: NCT00036439 and NCT00096655.

Patient factors that increase infliximab clearance and shorten half-life in inflammatory bowel disease: a population pharmacokinetic study

BACKGROUND

Infliximab (IFX) is effective therapy for ulcerative colitis and Crohn's disease, but it may be associated with side effects and loss of response. One loss of response mechanism is increased IFX clearance (IFX-CL), resulting in short half-life and decreased troughs.

METHODS

Patients were recruited, and relevant demographic, clinical, and laboratory data were recorded. IFX serum concentrations and antibodies against IFX (ATI) were measured for therapeutic drug monitoring and modeled using NONMEM.

RESULTS

There were 169 IFX concentrations (Crohn's disease = 73, ulcerative colitis = 92, and diagnosis undetermined = 4). Patient factors significantly associated with high IFX-CL were low albumin, high body weight, and the presence of ATI (P ≤ 0.001). Disease type did not affect IFX-CL. The typical IFX-CL was 0.381 L/d. ATI formation was associated with a 259% increase in IFX-CL. The estimated median IFX effective half-life was 5.6 ± 2.4 days. Patients with low weight are more likely to have low troughs because IFX CL is not linearly related to weight, but IFX dosing is weight-based (in mg/kg). Simulations investigating alternative dose strategies suggested that more reliably measurable concentrations over the dose interval were achieved when the dose interval was shortened than by increasing administered dose.

CONCLUSIONS

IFX-CL is significantly influenced by patient factors, specifically, albumin, body weight, and ATI. There should be a decreasing IFX dose interval strategy, particularly for low albumin patients. Higher starting doses may benefit low body weight patients. Pharmacokinetic models and therapeutic drug monitoring may ensure that patients maintain measurable concentrations throughout dose intervals. Individualized dosing may improve outcomes for IFX-treated patients with Crohn's disease and ulcerative colitis.

New tools and approaches for improved management of inflammatory bowel diseases

BACKGROUND AND AIMS

Inflammatory bowel diseases are part of a wider conglomeration of immune-mediated inflammatory diseases. New management approaches need to be developed as we understand more of the epidemiology and aetiology of inflammatory bowel diseases and medical care becomes more complex.

METHODS

Selected new tools and approaches for improved management of inflammatory bowel diseases are presented, based on published evidence and clinical experience.

RESULTS

Setting quality of care standards that are consistent across different inflammatory bowel disease care settings will be paramount and require collaboration between specialist and non-specialist centres. Alongside this, the value of care will need to be evaluated in terms of maximising outcomes over the entire care cycle for a patient. In moving towards a value-based approach to management, it is important to determine the progression rate of the disease by measuring cumulative bowel damage. As well as understanding the course of disease in individual patients, it is also becoming more feasible to individualise therapy and exploit drug pharmacology to achieve better and more long-term responses. Finally, it is timely to consider formal collaborations between specialists in immune-mediated inflammatory diseases to ensure more cohesive patient care.

CONCLUSIONS

The potential for improved management of patients with inflammatory bowel diseases continues to increase as we look to understand when and how to intervene in the disease process and how to adopt a collaborative management approach that promotes networking and reduces heterogeneity of care across different care settings.

Pharmacokinetics of biologics and the role of therapeutic monitoring

Biologic therapies, including the anti-tumor necrosis factor-α and cell adhesion molecule inhibitor drugs, have revolutionized the treatment of moderate-to-severe inflammatory bowel disease. Since the introduction of anti-tumor necrosis factor therapies, the strategy of empiric dose-escalation, either increasing the dose or frequency of administration, has been used to recapture clinical response in inflammatory bowel disease. Disparate clinical outcomes have been linked to serum drug and antidrug antibody levels. Therapeutic drug monitoring has emerged as a framework for understanding and responding to the variability in clinical response and remission.

Therapeutic Drug Monitoring of TNF Antagonists in Inflammatory Bowel Disease

Although tumor necrosis factor (TNF)-α antagonists play a critical role in the treatment of moderate-to-severe inflammatory bowel disease (IBD), several factors can impact treatment response. The degree of systemic inflammation, serum albumin concentration, disease type, body mass index, gender, concomitant therapy with immunosuppressive agents, and especially development of antidrug antibodies (ADAs) are key determinants of TNF antagonist pharmacokinetics and clinical outcomes. Therefore, measurement of serum drug and antibody concentrations in patients with IBD who are on TNF antagonists has the potential to guide clinical decision-making, optimize treatment, improve outcomes, and reduce healthcare costs. Multiple strategies to prevent ADA formation exist, including multiple clinical algorithms that employ therapeutic drug monitoring to optimize treatment following a secondary loss of therapeutic response. An individualized approach is needed, however, to identify early predictors of ADA development and other confounders of TNF antagonist therapy.

The challenge of indication extrapolation for infliximab biosimilars

A biosimilar is intended to be highly similar to a reference biologic such that any differences in quality attributes (i.e., molecular characteristics) do not affect safety or efficacy. Achieving this benchmark for biologics, especially large glycoproteins such as monoclonal antibodies, is challenging given their complex structure and manufacturing. Regulatory guidance on biosimilars issued by the U.S. Food and Drug Administration, Health Canada and European Medicines Agency indicates that, in addition to a demonstration of a high degree of similarity in quality attributes, a reduced number of nonclinical and clinical comparative studies can be sufficient for approval. Following a tiered approach, clinical studies are required to address concerns about possible clinically significant differences that remain after laboratory and nonclinical evaluations. Consequently, a critical question arises: can clinical studies that satisfy concerns regarding safety and efficacy in one condition support "indication extrapolation" to other conditions? This question will be addressed by reviewing the case of a biosimilar to infliximab that was approved recently in South Korea, Europe, and Canada for multiple indications through extrapolation. The principles discussed should also apply to biosimilars of other monoclonal antibodies that are approved to treat multiple distinct conditions.

Tailoring anti-TNF therapy in IBD: drug levels and disease activity

The treatment of IBD with anti-TNF agents has substantially evolved since their first introduction more than a decade ago. The robust efficacy witnessed in many patients has raised new questions pertaining to the observation of subgroups of patients who fail to respond or who lose response to these otherwise very effective drugs. Conversely, the exorbitant cost of biologic agents coupled with their efficacy in inducing lasting remission has introduced new concepts addressing the possibility of therapy cessation in some patients after deep remission has been achieved. Measuring drug and anti-drug antibody (ADA) levels which develop in some patients has emerged as a valuable tool in understanding the mechanisms responsible for some of these clinical scenarios. However, knowledge on how to use these measurements to guide clinical decisions in daily practice is still in its nascency and awaits prospective validation trials. Furthermore, as described in this Review, knowledgeable interpretation of drug and ADA test results mandates understanding the interplay between the technical profile of the assay used, the timing of the measurement in the drug cycle, assessment of disease activity, and the profoundly different pharmaco-clinical scenarios that can culminate in a similar test result.

TNF blocking therapies and immunomonitoring in patients with inflammatory bowel disease

Since their appearance in the armamentarium for inflammatory bowel disease (IBD) more than a decade ago, antitumor necrosis factor (TNF) inhibitors have demonstrated beneficial activity in induction and maintenance of clinical remission, mucosal healing, improvement in quality of life, and reduction in surgeries and hospitalizations. However, more than one-third of patients present primary resistance, and another one-third become resistant over time. One of the main factors associated with loss of response is the immunogenicity of anti-TNF biologics leading to the production of antidrug antibodies (ADAbs) accelerating their clearance. In this review we present the current state of the literature on the place of TNF and its blockage in the treatment of patients with IBD and discuss the usefulness of serum trough levels and ADAb monitoring in the optimization of anti-TNF therapies.

Predicting treatment response in psoriasis using serum levels of adalimumab and etanercept: a single-centre, cohort study

BACKGROUND

A substantial proportion of patients with psoriasis do not respond, or lose initial response to tumour necrosis factor-α antagonists. One possible mechanism relates to subtherapeutic drug levels due to an immunogenic antibody response.

OBJECTIVES

To investigate the association between serum adalimumab and etanercept levels, antidrug antibody levels and clinical response in a cohort of patients with psoriasis using a commercially available enzyme-linked immunoassay.

METHODS

In a single-centre cohort of 56 adults with chronic plaque psoriasis initiated on adalimumab or etanercept monotherapy between 2009 and 2011, drug and antidrug antibody levels were measured at the patients' routine clinic reviews (4, 12 and 24 weeks of treatment and the last available observation). Patients' responses at 6 months were stratified into responders [75% reduction in Psoriasis Area and Severity Index from baseline (PASI 75) or Physician's Global Assessment score of 'clear' or 'nearly clear'] and nonresponders (failure to achieve PASI 50).

RESULTS

After 4 weeks, adalimumab levels were significantly higher in responders compared with nonresponders (P = 0·003) and these higher levels were sustained at 12 and 24 weeks. Anti adalimumab antibodies were detected in 25% of nonresponders (two of eight patients, average 22·5 weeks' follow-up) and none of the responders (n = 23, average 26·1 weeks' follow-up). There was no significant association between etanercept levels and clinical response at 4 weeks (P = 0·317) and no antietanercept antibodies were detected. Lack of serum trough levels may have resulted in underestimation of the prevalence of antidrug antibodies.

CONCLUSIONS

Early adalimumab drug level monitoring at 4 weeks may be useful in predicting treatment response and potentially reduce drug exposure (and associated cost) with earlier review of treatment in those with low levels. No conclusions about the value of etanercept drug monitoring can be made due to the paucity of data. Larger studies are now required to assess the clinical utility and cost-effectiveness of these assays in personalizing therapy in psoriasis.

Outcomes following infliximab therapy for pediatric patients hospitalized with refractory colitis-predominant IBD

OBJECTIVES

Although randomized trials demonstrated the efficacy of infliximab for both pediatric Crohn disease and ulcerative colitis (UC), few patients in these studies exhibited colitis requiring hospitalization. The aims of this study were to determine the rate of subsequent infliximab failure and dose escalation in pediatric patients who started taking infliximab during hospitalization for colitis-predominant IBD, and to identify potential predictors of these endpoints.

METHODS

This is a single-center retrospective cohort study of patients admitted from 2005 to 2010 with Crohn colitis, UC, or IBD-unspecified (IBD-U) and initiated on infliximab.

RESULTS

We identified 29 patients (12 Crohn colitis, 15 UC, and 2 IBD-U; median age 14 years) with a median follow-up of 923 days. Eighteen patients (62%) required infliximab dose escalation (increased dose or decreased infusion interval). Infliximab failure occurred in 18 patients (62%) because of ineffectiveness in 12 (67%) and adverse reactions in 6 (33%). Twelve patients (41%) underwent colectomy. Subsequent need for infliximab dose escalation was associated with lower body mass index z score (P = 0.01), lower serum albumin (P = 0.03), and higher erythrocyte sedimentation rate (ESR) (P = 0.002) at baseline. ESR predicted subsequent infliximab dose escalation with an area under the curve of 0.89 (95% confidence interval [CI] 0.72-1.00) and a sensitivity and specificity at a cutoff of 38 mm/hour of 0.79 (95% CI 0.49-0.95) and 0.88 (95% CI 0.47-0.99), respectively.

CONCLUSIONS

Most hospitalized pediatric patients with colitis treated with infliximab require early-dose escalation and fail the drug long term. Low body mass index and albumin and high ESR, may identify patients who would benefit from a higher infliximab starting dose.

High C-reactive protein in Crohn's disease patients predicts nonresponse to infliximab treatment

BACKGROUND

Infliximab (IFX) is effective in treating Crohn's disease (CD) and C-reactive protein (CRP) is a useful biomarker in assessing inflammatory activity.

AIM

Correlate CRP levels before beginning of IFX, at week 14 and CRP delta within the first year of IFX treatment.

METHODS

Retrospective study of CD patients undergoing treatment with IFX. Primary nonresponse (PNR) was defined as no symptomatic improvement and CRP persistently elevated; sustained response (SR) as symptomatic improvement for at least 1 year without therapeutic adjustment; response after therapeutic adjustment (RTA) as analytic and clinical response but requiring IFX dose/frequency adjustment or association with another drug.

RESULTS

Baseline CRP levels were higher in PNR compared with SR (26.2mg/L vs 9.6 mg/L, p=0.015) and RTA (26.2mg/L vs 7.6 mg/L, p=0.007). CRP levels greater than 15 mg/L at baseline predict PNR with 67% sensitivity and 65% specificity. Lower CRP levels at week 14 were more likely to predict SR relative to RTA (3.1mg/L vs 7.6 mg/L p=0.019) and PNR (3.1mg/L vs 9.1mg/L; p=0.013). CRP levels greater than 4.6 mg/L at week 14 predict PNR with 67% sensitivity and 62% specificity. A higher CRP delta between beginning of treatment and week 14 is more likely to predict SR relative to RTA (5.2mg/L vs 0.6 mg/L p=0.027).

CONCLUSION

CRP levels at week 14 were associated with SR in patients treated with IFX, independently of baseline CRP serum levels. High inflammatory burden at beginning of IFX treatment was correlated with a worse response.

Immunogenicity and PK/PD evaluation in biotherapeutic drug development: scientific considerations for bioanalytical methods and data analysis

With the advent of novel technologies, considerable advances have been made in the evaluation of the relationship between PK and PD. Ligand-binding assays have been the primary assay format supporting PK and immunogenicity assessments. Critical and in-depth characterizations of the ligand-binding assay of interest can provide valuable understanding of the limitations, for interpreting PK/PD and immunogenicity results. This review illustrates key challenges with regard to understanding the relationship between anti-drug antibody and PK/PD, including confounding factors associated with the development and validation of ligand-binding assays, mechanisms by which anti-drug antibody impacts PK/PD, factors to consider during data analyses and interpretation, and a perspective on integrating immunogenicity data into the well-established quantitative modeling approach. Through recognizing these challenges, we propose some opportunities for improvements in the development and validation of fit-for-purpose bioanalytical methods.

A randomised, double-blind, multicentre, parallel-group, prospective study comparing the pharmacokinetics, safety, and efficacy of CT-P13 and innovator infliximab in patients with ankylosing spondylitis: the PLANETAS study

OBJECTIVES

To compare the pharmacokinetics (PK), safety and efficacy of innovator infliximab (INX) and CT-P13, a biosimilar to INX, in patients with active ankylosing spondylitis (AS).

METHODS

Phase 1 randomised, double-blind, multicentre, multinational, parallel-group study. Patients were randomised to receive 5 mg/kg of CT-P13 (n=125) or INX (n=125). Primary endpoints were area under the concentration-time curve (AUC) at steady state and observed maximum steady state serum concentration (Cmax,ss) between weeks 22 and 30. Additional PK, efficacy endpoints, including 20% and 40% improvement response according to Assessment in Ankylosing Spondylitis International Working Group criteria (ASAS20 and ASAS40), and safety outcomes were also assessed.

RESULTS

Geometric mean AUC was 32 765.8 μgh/ml for CT-P13 and 31 359.3 μgh/ml for INX. Geometric mean Cmax,ss was 147.0 μg/ml for CT-P13 and 144.8 μg/ml for INX. The ratio of geometric means was 104.5% (90% CI 94% to 116%) for AUC and 101.5% (90% CI 95% to 109%) for Cmax,ss. ASAS20 and ASAS40 responses at week 30 were 70.5% and 51.8% for CT-P13 and 72.4% and 47.4% for INX, respectively. In the CT-P13 and INX groups more than one adverse event occurred in 64.8% and 63.9% of patients, infusion reactions occurred in 3.9% and 4.9%, active tuberculosis occurred in 1.6% and 0.8%, and 27.4% and 22.5% of patients tested positive for anti-drug antibodies, respectively.

CONCLUSIONS

The PK profiles of CT-P13 and INX were equivalent in patients with active AS. CT-P13 was well tolerated, with an efficacy and safety profile comparable to that of INX up to week 30.

Review article: a clinician's guide for therapeutic drug monitoring of infliximab in inflammatory bowel disease

BACKGROUND

Tumour necrosis factor (TNF)-antagonists have an established role in the treatment of inflammatory bowel diseases (IBDs), however, subtherapeutic drug levels and the formation of anti-drug antibodies (ADAs) may decrease their efficacy.

AIM

The evidence supporting the use of therapeutic drug monitoring (TDM) based clinical algorithms for infliximab (IFX) and their role in clinical practice will be discussed.

METHODS

The literature was reviewed to identify relevant articles on the measurement of IFX levels and antibodies-to-infliximab.

RESULTS

Treatment algorithms for IBD have evolved from episodic monotherapy used in patients refractory to all other treatments, to long-term combination therapy initiated early in the disease course. Improved remission rates have been observed with this paradigm shift, nevertheless many patients ultimately lose response to therapy. Although empiric dose optimization or switching agents constitute the current standard of care for secondary failure, these interventions have not been applied in an evidence-based manner and are probably not cost-effective. Multiple TDM-based algorithms have been developed to identify patients that may benefit from measurement of IFX and ADA levels to guide adjustments to therapy.

CONCLUSIONS

Therapeutic drug monitoring offers a rational approach to the management of secondary failure to IFX. This concept has gained momentum based on evidence from case series, cohort studies and post-hoc analyses of randomised controlled trials.

Are hepatic impairment studies necessary for therapeutic proteins?

OBJECTIVE

This study assessed whether trials to investigate the effect of hepatic impairment on the pharmacokinetics of therapeutic proteins (TPs), which are conducted for small molecule drugs, are necessary.

METHODS

The product labeling for 91 TPs that have been approved by the US Food and Drug Administration were reviewed. A PubMed search was also conducted to identify completed studies that assessed the effect of hepatic impairment on the pharmacokinetics of TPs. Biologic License Applications were subsequently reviewed to gather further descriptions of the trials conducted in patients with hepatic impairment and data analyses.

RESULTS

No dedicated pharmacokinetics trials were conducted in patients with hepatic impairment for these approved TPs, but subgroup (n = 2 [2.2%]) or population (n = 5 [5.5%]) pharmacokinetic analyses were performed for 7 TPs. The pharmacokinetics of these proteins were not affected by the hepatic dysfunction, with the exception that the clearance of drotrecogin alfa seemed 25% higher in patients with hepatic impairment than in patients without hepatic impairment; however, no dose reduction was recommended. Thus, the effect of hepatic impairment on the pharmacokinetics of TPs is unclear based on the limited analyses completed to date.

CONCLUSIONS

A dedicated pharmacokinetics trial for TPs in patients with hepatic impairment is not necessary. Recognizing that the data are very limited, it would be important to continue collecting pharmacokinetic data of TP in patients with hepatic impairment and using population pharmacokinetic analyses to evaluate the effect of hepatic impairment on the pharmacokinetics of TP.

Pharmacokinetics, pharmacodynamics and physiologically-based pharmacokinetic modelling of monoclonal antibodies

Development of monoclonal antibodies (mAbs) and their functional derivatives represents a growing segment of the development pipeline in the pharmaceutical industry. More than 25 mAbs and derivatives have been approved for a variety of therapeutic applications. In addition, around 500 mAbs and derivatives are currently in different stages of development. mAbs are considered to be large molecule therapeutics (in general, they are 2-3 orders of magnitude larger than small chemical molecule therapeutics), but they are not just big chemicals. These compounds demonstrate much more complex pharmacokinetic and pharmacodynamic behaviour than small molecules. Because of their large size and relatively poor membrane permeability and instability in the conditions of the gastrointestinal tract, parenteral administration is the most usual route of administration. The rate and extent of mAb distribution is very slow and depends on extravasation in tissue, distribution within the particular tissue, and degradation. Elimination primarily happens via catabolism to peptides and amino acids. Although not definitive, work has been published to define the human tissues mainly involved in the elimination of mAbs, and it seems that many cells throughout the body are involved. mAbs can be targeted against many soluble or membrane-bound targets, thus these compounds may act by a variety of mechanisms to achieve their pharmacological effect. mAbs targeting soluble antigen generally exhibit linear elimination, whereas those targeting membrane-bound antigen often exhibit non-linear elimination, mainly due to target-mediated drug disposition (TMDD). The high-affinity interaction of mAbs and their derivatives with the pharmacological target can often result in non-linear pharmacokinetics. Because of species differences (particularly due to differences in target affinity and abundance) in the pharmacokinetics and pharmacodynamics of mAbs, pharmacokinetic/pharmacodynamic modelling of mAbs has been used routinely to expedite the development of mAbs and their derivatives and has been utilized to help in the selection of appropriate dose regimens. Although modelling approaches have helped to explain variability in both pharmacokinetic and pharmacodynamic properties of these drugs, there is a clear need for more complex models to improve understanding of pharmacokinetic processes and pharmacodynamic interactions of mAbs with the immune system. There are different approaches applied to physiologically based pharmacokinetic (PBPK) modelling of mAbs and important differences between the models developed. Some key additional features that need to be accounted for in PBPK models of mAbs are neonatal Fc receptor (FcRn; an important salvage mechanism for antibodies) binding, TMDD and lymph flow. Several models have been described incorporating some or all of these features and the use of PBPK models are expected to expand over the next few years.

Drug monitoring of biologics in inflammatory bowel disease

PURPOSE OF REVIEW

The monoclonal antibodies currently used for the treatment of inflammatory bowel disease (IBD) have been thoroughly studied with regard to efficacy and safety. Their pharmacokinetics and the considerable inter-individual variability of clearance and immunogenicity have attracted a great deal of attention recently. Knowledge about their properties carries the potential to optimize efficacy and durability of therapeutics that is a mainstay in the medical management of IBD.

RECENT FINDINGS

Based on population-based pharmacokinetics models, factors impacting the clearance of infliximab have been identified, antidrug antibodies (ADA) being one of them. Trough levels have been shown to correlate with clinical response and steroid-free remission. Initial insights have recently been gained into the individual course of ADA with a potential impact on future therapeutic strategies.

SUMMARY

We briefly review the current state of the literature and propose an algorithm for the use of serum trough levels and ADA as basis for monitoring of biologics in patients with IBD.

Association of baseline C-reactive protein and prior anti-tumor necrosis factor therapy with need for weekly dosing during maintenance therapy with adalimumab in patients with moderate to severe Crohn's disease

OBJECTIVE

A post hoc analysis of data from the adalimumab Crohn's disease (CD) maintenance trial (CHARM, NCT00077779), examining the relationship between adalimumab dosing and maintenance of remission and response in subgroups stratified by previous anti-TNF use and baseline CRP.

METHODS

All patients received open-label induction (adalimumab: 80 mg, week [wk] 0; 40 mg, wk 2). At wk 4, all patients were randomized to double-blind maintenance adalimumab (40 mg weekly or every other week [eow]) or placebo for 52 weeks. In this analysis, clinical remission (CDAI <150) and clinical response (CR-100) at wk 26 and wk 56 by baseline CRP (high: ≥ 10 mg/L, or low: <10 mg/L) and prior anti-TNF use were determined for patients with CR-70 at wk 4.

RESULTS

Of 498 patients in this analysis, 260 (52.2%) were anti-TNF-naïve. For anti-TNF-naïve patients, the wk 56 remission rates in the adalimumab groups were significantly greater than placebo (P < 0.05) for both high and low CRP cohorts, with no statistically significant differences between remission rates with eow and weekly dosing within each CRP cohort (high: 52.8% eow, 53.5% weekly; low: 34.7% eow, 41.9% weekly). For anti-TNF-exposed patients, wk 56 remission rates were higher than placebo with both eow and weekly dosing within each cohort; weekly dosing in the high CRP cohort and eow dosing in the low CRP cohort achieved statistical significance (P < 0.05). In the high CRP cohort, remission rate with weekly dosing (46.9%) was statistically significantly greater compared with eow dosing (22.5%). There were no significant differences between eow (23.1%) and weekly (37.0%) dosing in the low CRP group. For all subgroups, clinical remission (wk 26) and clinical response (wk 26 and wk 56) patterns were similar to those observed for wk 56 remission.

CONCLUSIONS

These subgroup analyses suggest that in patients with moderately to severely active CD, weekly dosing may be most effective in the anti-TNF-experienced patients with elevated CRP at baseline.

Assessing immunogenicity of biosimilar therapeutic monoclonal antibodies: regulatory and bioanalytical considerations

This article reflects on methodological limitations for interpretation of relative immunogenicity of biosimilar and reference therapeutic monoclonal antibodies, in emphasizing the relevance of correlation of bioanalytical signals with appropriate clinical end points, and the possible need for post-marketing observational studies to indicate the impact of detected differences in anti-drug antibody incidence and magnitude on sustainability of treatment benefit. Given the current uncertainty regarding the longer term clinical impact of undesirable immunogenicity for reference products, there can be no predefined margin for an acceptable difference based on incidence and magnitude of detected anti-drug antibodies. Any detected differences should be assessed in relation to clinical parameters; and the designation of biosimilarity made with reference to the similarity demonstrated in the directly comparative quality, nonclinical and clinical evaluations. Application of this ‘totality of evidence’ approach is illustrated for infliximab and adalimumab.

Infliximab for the treatment of pediatric ulcerative colitis

Ulcerative colitis is a chronic, idiopathic, inflammatory disease of the colon and rectum that may be associated with growth failure, nutritional derangements and psychosocial ramifications in affected children. Multiple medical options are available to achieve disease remission; however, some of these medications can have unwanted side effects, especially in younger patients. With increased understanding of the etiology of the disease, newer therapeutic alternatives have arisen in the form of biologic therapies, namely monoclonal antibodies targeted to a specific protein or receptor. Specifically, infliximab, an anti-TNF-α agent, has been shown to be safe and effective for the treatment of moderate-to-severe pediatric ulcerative colitis.

The utility of modeling and simulation approaches to evaluate immunogenicity effect on the therapeutic protein pharmacokinetics

While therapeutic proteins (TP), particularly recombinant human proteins and fully human monoclonal antibodies, are designed to have a low immunogenic potential in humans, a clinical immune response does sometimes occur and cannot be predicted from preclinical studies. Changes in TP pharmacokinetics may be perceived as an early indication of antibody formation and serve as a surrogate for later changes in efficacy and safety in individual subjects. Given the substantial increase in number of biological products, including biosimilars, there is an urgent need to quantitatively predict and quantify the immune response and any consequential changes in TP pharmacokinetics. The purpose of this communication is to review the utility of population-based modeling and simulation approaches developed to date for investigating the development of an immune response and assessing its impact on TP pharmacokinetics. Two examples of empirical modeling approaches for pharmacokinetic assessment are presented. The first example presents methods to analyze pharmacokinetic data in the presence of anti-drug antibody (ADA) and confirm the effect of immunogenicity on TP pharmacokinetics in early phases of drug development. The second example provides a framework to analyze pharmacokinetic data in the absence or with very low incidence of ADA and confirm with enough power the lack of an immunogenicity effect on TP pharmacokinetics in late phases of drug development. Finally, a theoretical mechanism-based modeling framework is presented to mathematically relate the complex interaction among TP, their targets, and ADA.

Meta-analysis: effect of preoperative infliximab use on early postoperative complications in patients with ulcerative colitis undergoing abdominal surgery

BACKGROUND

Infliximab is widely used in severe and refractory ulcerative colitis (UC). The results of clinical studies are inconsistent on whether preoperative infliximab use increases early postoperative complications in UC patients.

AIM

To determine the clinical safety and efficacy of preoperative infliximab treatment in UC patients with regard to short-term outcomes following abdominal surgery.

METHODS

PubMed, Embase databases were searched for controlled observational studies comparing postsurgical morbidity in UC patients receiving infliximab preoperatively with those not on infliximab. The primary endpoint was total complication rate. Secondary endpoints included the rate of infectious and non-infectious complications. We calculated pooled odds ratios (ORs) with 95% confidence intervals (CIs) as summary measures.

RESULTS

A total of 13 studies involving 2933 patients were included in our meta-analysis. There was no significant association between infliximab therapy preoperatively and total (OR = 1.09, 95% CI: 0.87-1.37, P = 0.47), infectious (OR = 1.10, 95% CI: 0.51-2.38, P = 0.81) and non-infectious (OR = 1.10, 95% CI: 0.76-1.59, P = 0.61) postoperative complications respectively. Infliximab might be a protective factor against infection for the use within 12 weeks prior to surgery (OR = 0.43, 95% CI: 0.22-0.83, P = 0.01). No publication bias was found.

CONCLUSION

Preoperative infliximab use does not increase the risk of early postoperative complications in patients with ulcerative colitis undergoing abdominal surgery.

Stratification of antibody-positive subjects by antibody level reveals an impact of immunogenicity on pharmacokinetics

The availability of highly sensitive immunoassays enables the detection of antidrug antibody (ADA) responses of various concentrations and affinities. The analysis of the impact of antibody status on drug pharmacokinetics (PK) is confounded by the presence of low-affinity or low-concentration antibody responses within the dataset. In a phase 2 clinical trial, a large proportion of subjects (45%) developed ADA following weekly dosing with AMG 317, a fully human monoclonal antibody therapeutic. The antibody responses displayed a wide range of relative concentrations (30 ng/mL to >13 μg/mL) and peaked at various times during the study. To evaluate the impact of immunogenicity on PK, AMG 317 concentration data were analyzed following stratification by dose group, time point, antibody status (positive or negative), and antibody level (relative concentration). With dose group as a stratifying variable, a moderate reduction in AMG 317 levels (<50%) was observed in antibody-positive subjects when compared to antibody-negative subjects, but the difference was not statistically significant in all dose groups. The most significant reduction in AMG 317 levels was revealed when antibody data was stratified by both time point and antibody level. In general, high ADA concentrations (>500 ng/mL) and later time points (week 12) were associated with significantly (up to 97%) lower trough AMG 317 concentrations. The use of quasi-quantitative antibody data and appropriate statistical methods was critical for the most comprehensive evaluation of the impact of immunogenicity on PK.

Therapeutic drug monitoring of tumor necrosis factor antagonists in inflammatory bowel disease

Although tumor necrosis factor (TNF) antagonists have shown clear benefits over conventional treatments for inducing and maintaining clinical remission in both Crohn's disease and ulcerative colitis, a high proportion of patients lose response over time. Given the scarce alternative of treatments when treatment failure occurs, it is highly desirable to optimize both initial response and long-term continuation of TNF antagonists. One of the most well-characterized factors associated with loss of response to these agents is the development of immunogenicity, whereby the production of neutralizing antidrug antibodies accelerates drug clearance, leading to subtherapeutic drug concentrations and, ultimately, to treatment failure. However, other patient-related factors, such as sex and/or body size, and disease severity, including TNF burden and serum albumin concentration among others, also may influence the pharmacokinetics of these agents. Nevertheless, the evidence generated to date about these complex interactions is scarce, and further prospective studies evaluating their influence on the pharmacokinetics of TNF antagonists are needed. Drug adjustment empirically based on clinical symptoms often is inaccurate and may lead to suboptimal outcomes. Recent evidence shows that maintenance of an optimal therapeutic drug concentration is associated with improved clinical outcomes. Therefore, incorporation of therapeutic drug monitoring into clinical practice may allow clinicians to optimize treatment by maintaining effective drug concentrations over time.

Optimizing immunomodulators and anti-TNF agents in the therapy of Crohn disease

Randomized trials support the use of the thiopurines and anti-TNF monoclonal antibodies in treating Crohn disease. New therapeutic approaches and laboratory assays have helped optimize the use of these agents. Thiopurine methyltransferase activity should always be determined to avoid thiopurines in individuals with absent enzyme activity. The role of metabolite-adjusted dosing when initiating thiopurines is not settled. Measuring metabolites helps guide management in patients failing therapy. Loss of response to anti-TNF therapy is mitigated by maintenance therapy and concomitant immunomodulators. When loss of response to infliximab occurs, management is guided by the serum concentrations of infliximab and antibodies to infliximab.

Influence of methotrexate on infliximab pharmacokinetics and pharmacodynamics in ankylosing spondylitis

AIMS

Infliximab, an anti-tumour necrosis factor α monoclonal antibody, has profoundly modified the treatment of several inflammatory diseases. The objective was to assess the influence of methotrexate on the variability of infliximab pharmacokinetics and concentration-effect relationship in axial ankylosing spondylitis (AAS) patients.

METHODS

Twenty-six patients with AAS were included in a prospective study. They were treated by infliximab 5 mg kg⁻¹ infusions at weeks 0, 2, 6, 12 and 18. Infliximab concentrations were measured before, and 2 and 4 h after each infusion, and at each intermediate visit (weeks 1, 3, 4, 5, 8, 10 and 14). Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) was measured at each visit. Infliximab pharmacokinetics was described using a two-compartment model with first-order distribution and elimination constants. A population approach was used. Infliximab pharmacodynamics was described using the area under the BASDAI curve.

RESULTS

A total of 507 blood samples and 329 BASDAI measurements were collected. The following pharmacokinetic parameters were obtained (interindividual coefficient of variation): volumes of distribution for the central compartment = 2.4 l (9.6%) and peripheral compartment = 1.8 l (26%), systemic clearance = 0.23 l day⁻¹ (22%) and intercompartment clearance = 2.3 l day⁻¹. Methotrexate influenced neither pharmacokinetic nor BASDAI variability.

CONCLUSIONS

Using the present dosage, the clinical efficacy of infliximab is only weakly influenced by its serum concentrations. The results do not support the combination of methotrexate with infliximab in ankylosing spondylitis.

Anti-TNF monoclonal antibodies in inflammatory bowel disease: pharmacokinetics-based dosing paradigms

Crohn's disease and ulcerative colitis are chronic inflammatory disorders resulting from immune dysregulation. Patients who fail conventional medical therapy require biological treatment with monoclonal antibodies (mAbs). Although mAbs are highly effective for induction and maintenance of clinical remission, not all patients respond, and a high proportion of patients lose response over time. One factor associated with loss of response is immunogenicity, whereby the production of antidrug antibodies accelerates mAb clearance. However, other factors related to patient and disease characteristics also influence the pharmacokinetics of mAbs. These factors include gender, body size, concomitant use of immunosuppressive agents, disease type, serum albumin concentration, and the degree of systemic inflammation. Because it is important to maintain clinically effective concentrations to provide optimal clinical response and drug exposure is affected by patient factors, a better understanding of the pharmacology of mAbs will ultimately result in better patient care.

Therapeutic drug monitoring of biologics for inflammatory bowel disease

BACKGROUND

Although tumor necrosis factor (TNF) antagonists are effective for the treatment of Crohn's disease and ulcerative colitis, lack and loss of clinical response is a clinical challenge. Accordingly, the use of therapeutic drug monitoring has been proposed as a means to optimize treatment. This article reviews the mechanisms of and factors which influence clearance of biologics, the relationship between serum drug concentrations and antidrug antibody presence and treatment efficacy, and identifies areas for future research needs regarding the use of therapeutic drug monitoring in clinical practice.

METHODS

Publications regarding these topics were identified from literature searching and supplemented by review of gastroenterology meeting presentations and reference lists.

RESULTS

The clearance of monoclonal antibodies and pegylated antibody fragments is complex, and may be affected by demographic variables, concomitant medications, inflammatory burden, and immunogenicity, leading to high interpatient variability in plasma concentration of drug and clinical response. Several observational studies have demonstrated a relationship between anti-TNF agent serum drug concentrations and/or antidrug antibody presence and various symptomatic and objective clinical endpoints. However, these relationships are not absolute, and although some algorithms for the use of therapeutic drug monitoring in clinical practice have been proposed, none have yet been validated in a prospective clinical trial.

CONCLUSIONS

Further research to identify the most appropriate use of therapeutic drug monitoring is needed.

Monoclonal antibodies: what are the pharmacokinetic and pharmacodynamic considerations for drug development?

INTRODUCTION

The number of monoclonal antibodies available for clinical use and under development has dramatically increased in the last 10 years. Understanding their pharmacokinetics and pharmacodynamics is essential for selecting the right clinical candidate, correct dose and regimen for a target indication.

AREAS COVERED

This article reviews the existing literature and knowledge of monoclonal antibodies. Specifically, the authors discuss monoclonal antibodies with respect to their pharmacokinetics (including absorption, distribution and elimination) and their pharmacodynamics. The authors also look at the pharmacokinetic/pharmacodynamic relationship, scaling from preclinical to clinical studies and selection of the first-in-human dose.

EXPERT OPINION

Monoclonal antibodies have complex pharmacokinetic and pharmacodynamic characteristics that are dependent on several factors. Therefore, it is important to improve our understanding of the pharmacokinetics and pharmacodynamics of monoclonal antibodies from a basic research standpoint. It is also equally important to apply mechanistic pharmacokinetic/pharmacodynamic models to interpret the experimental results and facilitate efforts to predict the safety and efficacy of monoclonal antibodies.

Pediatric chronic ulcerative colitis: does infliximab increase post-ileal pouch anal anastomosis complications?

BACKGROUND

Total proctocolectomy with ileal pouch anal anastomosis (IPAA) is a common surgical approach to chronic ulcerative colitis (CUC). Preoperative use of Infliximab (IFX) has raised concern of increased postoperative complications. We sought to compare outcomes of pediatric patients (≤ 18 years) who were treated with IFX before IPAA to those who did not.

METHODS

Patients (≤ 18 years of age) who underwent IPAA from 2003 to 2008 for CUC were included, and their records were retrospectively reviewed for preoperative medications, operative technique, and 1-year postoperative complications (leak, wound infection, small bowel obstruction, pouchitis). Subjects were divided into 2 groups--those who received IFX preoperatively and those who did not.

RESULTS

Eleven patients received IFX preoperatively, and 27 children did not. All complications following IPAA were more frequent in the IFX group compared to controls (55% vs 26%). Small bowel obstruction was significantly higher in the IFX group (55% vs 7%). Long-term complications occurred in 64% of the IFX group and 61% of the controls.

CONCLUSION

Children that were treated with IFX prior to IPAA suffered twice as many postoperative complications. Long-term outcomes are similar. Currently, we recommend colectomy with end ileostomy for patients that receive IFX within 8 weeks of colectomy for CUC.