Rationale for Therapeutic Drug Monitoring of Biopharmaceuticals in Inflammatory Diseases

Infliximab Efficacy May Be Linked to Full TNF-α Blockade in Peripheral Compartment-A Double Central-Peripheral Target-Mediated Drug Disposition (TMDD) Model

Infliximab is an anti-TNF-α monoclonal antibody approved in chronic inflammatory bowel diseases (IBD). This study aimed at providing an in-depth description of infliximab target-mediated pharmacokinetics in 133 IBD patients treated with 5 mg/kg infliximab at weeks 0, 2, 14, and 22. A two-compartment model with double target-mediated drug disposition (TMDD) in both central and peripheral compartments was developed, using a rich database of 26 ankylosing spondylitis patients as a reference for linear elimination kinetics. Population approach and quasi-steady-state (QSS) approximation were used. Concentration-time data were satisfactorily described using the double-TMDD model. Target-mediated parameters of central and peripheral compartments were respectively baseline TNF concentrations (R^C₀ = 3.3 nM and R^P₀ = 0.46 nM), steady-stated dissociation rates (K^C_SS = 15.4 nM and K^P_SS = 0.49 nM), and first-order elimination rates of complexes (k^C_int = 0.17 day⁻¹ and k^P_int = 0.0079 day⁻¹). This model showed slower turnover of targets and infliximab-TNF complex elimination rate in peripheral compartment than in central compartment. This study allowed a better understanding of the multi-scale target-mediated pharmacokinetics of infliximab. This model could be useful to improve model-based therapeutic drug monitoring of infliximab in IBD patients.

[Pharmacokinetic variability of therapeutic antibodies]

Therapeutic antibodies have been increasingly used for the treatment of various diseases, including cancers and chronic inflammatory diseases. The pharmacokinetic interindividual variability of mAbs is large and influences, at least in part, the clinical response to antibody treatment. This variability is explained by a number of individual sources of variability, which are reviewed here. Some of them are major because they are frequently reported to greatly influence the interindividual variability; notably, increased body size, the presence of anti-drug antibodies, and high antigen mass are associated with decreased antibody concentrations. Other individual sources of variability are of less critical importance. They include sex, age, co-treatments, or genetic polymorphisms of IgG Fc receptors (FcgRs). The interindividual variability of antibody pharmacokinetics should be soundly described in order to design optimal dosing strategy.

Cost evolution of biological drugs in rheumatoid arthritis patients in a tertiary hospital: Influential factors on price

OBJECTIVE

To assess the evolution of cost per patient/year and the cost per patient/year/drug in patients with rheumatoid arthritis (RA) receiving biological treatments. To analyze and quantify the factors influencing this evolution, such as the optimization of the biological drugs, the use of biosimilars, and official discounts and discounts obtained after negotiated procedures. In addition, to assess specific clinical parameters of disease activity in these patients.

METHODS

Retrospective, observational study conducted in a Spanish tertiary hospital. Adult patients diagnosed with RA under treatment from 2009 to 2017 were included.

RESULTS

320, 270 and 389 patients were included in 2009, 2013 and 2017, respectively. The patient/year cost decreased from 10,789€ in 2009, 7491€ in 2013 to 7116€ in 2017. In 2017, due to the established competition, discounts of 14% and 29.5% were achieved on etanercept and its biosimilar; 11.5%, 17.8%, 17.9%, 17.3% on adalimumab, certolizumab, golimumab and tocilizumab IV respectively, and 24.6% and 43.1% on infliximab and its biosimilar. The percentage of patients optimized in 2017 was 35.2%. The annual saving in 2017 was 1,288,535€ (830,000€ due to dose optimization and/or administration regimens, 249,666€ corresponding to 7.5% of the official discount and 208,868€ after negotiated procedures).

CONCLUSION

The annual cost per patient in RA decreased considerably due to different factors, such as discounts on the purchase of drugs due to official discounts and negotiated procedures, together with the optimization of therapies, the latter being the factor that contributed most to this decrease.

Association between infliximab concentrations and clinical response in psoriasis: a prospective cohort study

BACKGROUND

Infliximab (IFX) trough concentrations (C_min) have been linked to treatment efficacy in psoriatic patients. Inter-individual IFX C_min variability and factors influencing IFX pharmacokinetics could explain differences in treatment response.

OBJECTIVE

To evaluate the association between IFX C_min and clinical outcomes in psoriatic patients.

METHODS

Prospective study of 33 patients with moderate to severe psoriasis receiving IFX at Bellvitge University Hospital, between October 2013 and November 2016. IFX C_min and antibodies toward infliximab (ATI) were measured.

RESULTS

We collected 155 IFX C_min and ATI values (mean age, 46 (14) years; 11 (33.3%) women). Mean IFX C_min was 2.5 (2.4) mg/L and ATIs were detected in six patients, resulting in undetectable IFX C_min. IFX C_min was significantly associated with ATI and body mass index (BMI) (β -2.51, 95% CI -3.56 to -1.4 and β -0.05, 95% CI -0.09 to -0.01). PASI score and PASI 90/100 response were significantly associated with IFX C_min (IRR 0.80, 95% CI 0.70 to 0.92; OR 1.79, 95% CI 1.18 to 2.71 and OR 1.79, 95% CI 1.14 to 2.81).

CONCLUSION

IFX C_min significantly influences PASI 90/100 response rates. IFX C_min wa significantly associated with ATI and BMI. The observed inter-individual variability in IFX C_min supports the need for IFX drug monitoring.

Immunogenicity assay development and validation for biological therapy as exemplified by ustekinumab

Introduction of biotherapeutics has been a major milestone in the treatment of different chronic diseases. Nevertheless, the immune system can recognize the administered biological as non-self and respond with generation of anti-drug antibodies (ADA), including neutralizing ADA (nADA). Immunogenic responses may result in altered drug dynamics and kinetics leading to changes in safety and efficacy. However, there are several challenges with standard techniques for immunogenicity testing. Ustekinumab (UST), used in different inflammatory diseases, is a therapeutic antibody directed against the shared p40 subunit of interleukin (IL)-12 and IL-23, interfering in the pathogenically crucial T helper type 1 (Th1)/Th17 pathway. We established and validated different approaches for detection and quantitation of UST, UST-specific ADA and nADA. Addressing the obstacle of complex formation of UST with nADA, we developed an acidification assay to approach the total amount of nADA. Validated methods were based on surface plasmon resonance spectroscopy (SPR), enzyme-linked immunosorbent assay (ELISA) and a cell-based approach to characterize neutralizing capacity of nADA. Parameters assessed were determination and quantitation limits, linearity, range, precision, accuracy and selectivity. Quantitation of ADA and UST was feasible at lower concentrations using ELISA, whereas SPR showed a wider linear range for determination of ADA and UST. Accuracy, precision and linearity for quantitation were comparable using ELISA, SPR and the cell-based approach. All validated parameters fulfill the requirements of regulatory agencies. A combination of the testing approaches could address the increasing demand of precision medicine as it can be suitable for capturing the whole spectrum of immunogenicity and is transferable to other biologicals.

Cost evolution of biological agents for the treatment of spondyloarthritis in a tertiary hospital: influential factors in price

Background Spending on biological agents has risen dramatically due to the high cost of the drugs and the increased prevalence of spondyloarthritis. Objective To evaluate the annual cost per patient and cost for each biological drug for treating patients with spondyloarthritis from 2009 to 2016, and to calculate factors that affect treatment cost, such as optimizing therapies by monitoring drug serum levels, the use of biosimilar-TNF inhibitors, and official discounts or negotiated rebates in biologicals acquired by the pharmacy department. Method Retrospective, observational study in a Spanish tertiary hospital. Main outcome Annual cost per patient and per drug. Factors that influenced the costs and socio-demographic parameters and disease activity. Results A total of 129, 215, and 224 patients were treated in 2009, 2013, and 2016, respectively. The annual cost per patient decreased: EUR11,604 in 2009, EUR8513 in 2013, and EUR7464 in 2016. The introduction of new drugs drives economic competition, leading to total savings per drug, with discounts reaching 5.8, 12.4, 16.7, 17.7, 13.7, and 24.8% for original infliximab, etanercept, adalimumab, ertolizumab, golimumab, and secukinumab, respectively, while rebates for biosimilar infliximab reached 31.90% in 2016. The number of patients with optimized therapies reached 47.5% in 2016, which led to cost savings of EUR798,614, in addition to savings from official discounts and rebates of EUR252,706 and savings from optimized therapies of EUR545,908 in 2016. Conclusion The cost of biological treatments declined after official discounts, negotiated rebates, and optimized therapies, leading to a significant decrease in the annual cost per patient. The greatest contribution to economic savings in biological therapy according to our study was biological therapy optimization.

Current Practice for Therapeutic Drug Monitoring of Biopharmaceuticals in Spondyloarthritis

Treatment of spondyloarthritis (SpA) has greatly improved in the biopharmaceutical era. These compounds, primarily tumor necrosis factor inhibitors, are effective, but some patients may show poor response, sometimes due to the presence of antidrug antibodies (ADAs). In some instances, clinicians may increase or taper the dose, depending on the clinical response. Besides the current clinical practice, a tailored strategy based on drug monitoring is emerging as a way to improve the use of these drugs. However, the relevance of this therapeutic drug monitoring of biopharmaceuticals for SpA is still unknown. In this literature review, we examined the most relevant articles dealing with the concentration-response relation, ADA detection, and pharmacokinetics in SpA treated with biopharmaceuticals. ADAs were associated with low or undetectable concentration of monoclonal antibodies. The relation between drug concentration and clinical response in SpA is debated, some studies showing an association and others not. Therefore, therapeutic drug monitoring of biopharmaceuticals for SpA requires a better understanding of the association among the pharmacokinetics, pharmacodynamics, and immunogenicity of these drugs.

Current Practices for Therapeutic Drug Monitoring of Biopharmaceuticals in Pediatrics

Biopharmaceuticals have recently emerged as effective treatments for refractory pediatric autoimmune conditions. Several reports have shown a relationship between drug concentration, antidrug antibodies, and clinical response in these patients, strongly suggesting the potential interest, usefulness, and reliability of therapeutic drug monitoring (TDM) in children. This article reviews the current state of research in juvenile idiopathic arthritis, pediatric inflammatory bowel disease, and pediatric psoriasis from a TDM point of view. There is a remarkable lack of evidence-based data in pediatric patients, which is reflected throughout the article. Most investigations of TDM are focused on research of tumor necrosis factor alpha antagonists in inflammatory bowel disease, albeit preliminary publications are emerging from pediatric rheumatologists and dermatologists. To date, immunogenicity has been a primary concern, particularly regarding infliximab and adalimumab therapy in children, as it may lead to a loss of therapeutic response. Preliminary investigations show that adjusting the dose according to blood drug concentrations improves disease outcomes by overcoming antidrug antibodies, suggesting a crucial role for TDM. Patients who receive other drugs, such as etanercept, abatacept, or tocilizumab, could benefit from TDM because dosage can be optimized by adjusting it to the minimum effective dose.