The clinical relevance of early anti-adalimumab antibodies detection in rheumatoid arthritis, ankylosing spondylitis and psoriatic arthritis: A prospective multicentre study

No Correlation between Anti-drug Antibodies and Therapeutic Response in Tunisian Patients with Chronic Inflammatory Diseases Treated by TNF Blockers

INTRODUCTION

Tumor necrosis factor alpha (TNF alpha) blockers such as infliximab (IFX) and adalimumab (ADA) had significantly changed the course of inflammatory diseases such as rheumatoid arthritis (RA), spondyloarthritis (SpA) and Crohn's disease (CD). However, about 30% of patients do not respond to these treatments. This lack of response may be due to the formation of antibodies against these drugs (anti-drug antibodies: ADAbs). The aim of this study was to determine the prevalence of ADAbs against IFX and ADA, and the trough serum concentration of IFX and ADA in RA, SpA or CD patients and to assess their impact on the therapeutic response.

METHODS

A cross sectional, multi-centric study was conducted, including patients with RA, SpA or CD treated with IFX or ADA as a first biotherapy for at least 6 months. ADAbs and trough levels were measured by an Enzyme Linked Immunosorbent assay (ELISA).

RESULTS

197 patients were included (57 RA, 73 SpA and 67 CD). ADAbs were positive in 40% of cases for IFX and 25% for ADA. They were positive in 40% of SpA, 35% of RA, and 21% of CD. The presence of ADAbs was inversely correlated to the trough levels of IFX and ADA during RA (p = 0.01 and p < 0.0001), SpA (p < 0.01 and p < 0.0001) and CD (p = 0.001 and p = 0.04). For all pathologies, the presence of ADAbs was not correlated with disease activity. Concomitant methotrexate significantly reduced immunogenicity.

CONCLUSION

In our study, the presence of ADAb and low trough levels seem to not affect the therapeutic response in patients on TNF alpha antagonists. Other tracks more than immunogenicity should be investigated to explain the loss of response to these biotherapies.

Tailored therapeutic decision of rheumatoid arthritis using proteomic strategies: how to start and when to stop?

Unpredictable treatment responses have been an obstacle for the successful management of rheumatoid arthritis. Although numerous serum proteins have been proposed, there is a lack of integrative survey to compare their relevance in predicting treatment outcomes in rheumatoid arthritis. Also, little is known about their applications in various treatment stages, such as dose modification, drug switching or withdrawal. Here we present an in-depth exploration of the potential usefulness of serum proteins in clinical decision-making and unveil the spectrum of immunopathology underlying responders to different drugs. Patients with robust autoimmunity and inflammation are more responsive to biological treatments and prone to relapse during treatment de-escalation. Moreover, the concentration changes of serum proteins at the beginning of the treatments possibly assist early recognition of treatment responders. With a better understanding of the relationship between the serum proteome and treatment responses, personalized medicine in rheumatoid arthritis will be more achievable in the near future.

Therapeutic drug monitoring of disease-modifying antirheumatic drugs in circulating leukocytes in immune-mediated inflammatory diseases

The treatment of immune-mediated inflammatory diseases (IMIDs) is one of the main challenges of modern medicine. Although a number of disease-modifying antirheumatic drugs (DMARDs) are available, there is wide variability in clinical response to treatment among individuals. Therapeutic drug monitoring (TDM) has been proposed to optimize treatment; however, some patients still experience unsatisfactory outcomes, although the blood concentrations of drugs in these patients remain in the therapeutic range. One possible reason for this is that the conventional samples (e.g., whole blood or plasma) used in TDM may not accurately reflect drug concentrations or concentrations of their metabolites at the target site. Hence, more refined TDM approaches to guide clinical decisions related to dose optimization are necessary. Circulating leukocytes or white blood cells have a critical role in driving the inflammatory process. They are recruited to the site of injury, infection and inflammation, and the main target of small molecule DMARDs is within immune cells. Given this, assaying drug concentrations in leukocytes has been proposed to be of possible relevance to the interpretation of outcomes. This review focuses on the clinical implications and challenges of drug monitoring of DMARDs in peripheral blood leukocytes from therapeutic or toxicological perspectives in IMIDs.

Immunogenicity of Monoclonal Antibodies and the Potential Use of HLA Haplotypes to Predict Vulnerable Patients

The use of monoclonal antibodies (mAbs) in the clinic has successfully expanded to treatment of cancer, viral infections, inflammations, and other indications. However, some of the classes of mAbs that are used in the clinic show the formation of anti-drug antibodies (ADAs) leading to loss of efficacy. This review describes ADA formation for the various mAbs, and its clinical effect. Lastly, this review considers the use of HLA-haplotypes as biomarkers to predict vulnerability of patients sensitive to formation of ADAs.

Therapeutic drug monitoring of biopharmaceuticals in inflammatory rheumatic and musculoskeletal disease: a systematic literature review informing EULAR points to consider

The objectives of this review were to collect and summarise evidence on therapeutic drug monitoring (TDM) of biopharmaceuticals in inflammatory rheumatic and musculoskeletal diseases and to inform the EULAR Task Force for the formulation of evidence-based points to consider. A systematic literature review (SLR) was performed, covering technical aspects and (clinical) utility of TDM, to answer 13 research questions. MEDLINE, Embase and Cochrane were searched until July 2020. American College of Rheumatology and EULAR abstracts were also considered for inclusion. Data were extracted in evidence tables and risk of bias assessment was performed. For the search on technical aspects, 678 records were identified, of which 22 papers were selected. For the clinical utility search, 3846 records were identified, of which 108 papers were included. Patient-related factors associated with biopharmaceutical blood concentrations included body weight, methotrexate comedication and disease activity. The identification of a target range was hampered by study variability, mainly disease activity measures and study type. Evidence was inconsistent for multiple clinical situations in which TDM is currently applied. However, for some particular scenarios, including prediction of future treatment response, non-response to treatment, tapering and hypersensitivity reactions, robust evidence was found. There is currently no evidence for routine use of proactive TDM, in part because published cost-effectiveness analyses do not incorporate the current landscape of biopharmaceutical costs and usage. This SLR yields evidence in favour of TDM of biopharmaceuticals in some clinical scenarios, but evidence is insufficient to support implementation of routine use of TDM.

Systematic Review and Principal Components Analysis of the Immunogenicity of Adalimumab

BACKGROUND

The reported immunogenicity rates of adalimumab differ significantly between studies because of a wide variety of factors related to the disease, patients, study design, and products.

OBJECTIVE

The objective of this study was to characterize this variability and identify the major factors that contribute to these fluctuations.

METHODS

A systematic literature review was conducted using the MEDLINE, Clinicaltrials.gov, and Cochrane Library databases. Studies that reported the immunogenicity rates of adalimumab were selected, and data pertaining to publication details, study characteristics, characteristics of the cohort at baseline, and immunogenicity were extracted. Records were sorted according to the immunogenicity assay type, and mean immunogenicity values for each assay type were calculated. Normalised immunogenicity was calculated for each report by subtracting the appropriate mean immunogenicity value. Collected data were subjected to statistical analysis, namely analysis of variance (ANOVA) and principal component analysis, to unveil immunogenicity rate patterns across studies from a multivariate perspective.

RESULTS

In total, 130 publications were identified, from which 165 data records were extracted and included in the analysis. The immunogenicity rates of adalimumab averaged 24.9% across studies and varied significantly over time, ranging between 0 and 87%. An increase across time in the reported immunogenicity rates was detected, and the assay used to detect anti-adalimumab antibodies was a significant (but not exclusive) contributor to this trend. Furthermore, the principal components analysis revealed that the type of study and the exposure time were associated with the assay-normalised immunogenicity rates of adalimumab. Nonetheless, neither these nor the remaining factors included in this analysis seem to contribute to the temporal increase in reported immunogenicity rates.

CONCLUSIONS

Future studies that evaluate the patient-, product-, and disease-related factors behind the immunogenicity of adalimumab are required because the evidence published so far does not completely explain the temporal increase in immunogenicity rates detected in this analysis.

Therapeutic Drug Monitoring in Patients with Suboptimal Response to Adalimumab for Hidradenitis Suppurativa: A Retrospective Case Series

BACKGROUND

Adalimumab, a tumor necrosis factor-α inhibitor, is a biologic used for the treatment of moderate-to-severe hidradenitis suppurativa (HS). It is well known that patients may experience loss of efficacy from its use in other conditions, and it is suggested that developing a strategy for therapeutic drug monitoring (TDM) may help secure optimal clinical outcomes.

OBJECTIVES

We sought to determine serum adalimumab concentrations and anti-adalimumab antibody (AAA) status in patients with moderate-to-severe HS.

METHODS

A retrospective case series of 38 patients with suboptimal response to adalimumab 40 mg weekly was conducted at a community dermatology clinic. Adalimumab serum trough levels, AAA status, and inflammatory biomarkers were collected. Blood was drawn on identification of suboptimal response (after a minimum of 12 weeks) and was collected once prior to receiving the next scheduled dose. Kruskal-Wallis and Chi-squared tests were used for data analysis.

RESULTS

A total of 38 patients had a median adalimumab trough concentration of 8.76 (interquartile range [IQR] 1.3-12.5) µg/mL. The median duration of adalimumab therapy of all patients was 21 (IQR 12-24) months. AAAs were detected in nine patients (24%), and all had subtherapeutic serum concentrations (< 6 µg/mL). Patients who were AAA+ had a significantly lower median adalimumab concentration than those who were AAA- (0.02 µg/mL [range 0.02-0.81] vs. 10.14 [range 0.76-48.00]; p = 0.0006).

CONCLUSION

Patients with AAAs had significantly lower serum adalimumab levels. The current study suggests that TDM may identify underlying reasons for suboptimal response and detect patients who may benefit from dose optimization strategies.

Presence of anti-nuclear antibodies is a risk factor for the appearance of anti-drug antibodies during infliximab or adalimumab therapy in patients with rheumatoid arthritis

This study aimed to directly analyze the potential relationship of anti-nuclear antibodies (ANA) before and after the administration of TNF-α inhibitors (TNFi) with the appearance of anti-drug antibodies (ADrA) in patients with rheumatoid arthritis (RA). A total of 121 cases, viz., 38, 53, and 30 cases treated with infliximab (IFX), adalimumab (ADA), and etanercept (ETN), respectively, were enrolled. The ANA titers were measured using indirect immunefluorescence assay (IF-ANA) and multiplex flow immunoassay (ANA Screen) before and serially during the therapy. The anti-IFX antibodies (HACA) and anti-ADA antibodies (AAA) were measured with a radioimmunoassay. ADrA turned positive in 14 (36.8%) among 38 patients treated with IFX, and 16 (30.2%) among 53 treated with ADA. All of them were positive for IF-ANA before TNFi administration, while ADrA never appeared in any of the 15 patients negative for IF-ANA (< 40). IF-ANA of high titers (≥ 320 and ≥ 640) before IFX treatment showed a significant association with the appearance of HACA 52 weeks after IFX (P = 0.040 and 0.017, respectively), whereas AAA appearance was not related to IF-ANA titers before treatment. Moreover, IF-ANA of high titers before IFX treatment was significantly associated with inefficacy and discontinuation of the treatment. The positivity of anti-SS-A antibodies before therapy might be a risk factor for ADrA appearance in patients treated with IFX or ADA. The percentage of patients whose IF-ANA titers increased was significantly higher with IFX than with ADA or ETN treatments (P = 0.026 and 0.022, respectively). High ANA titers and positive ANA Screen after IFX therapy showed a significant association with HACA appearance and possibly led to treatment failure. Among the three TNFi, only IFX showed a close relationship with IF-ANA and ADrA appearance, suggesting the interaction of immunogenicity with autoimmunity as well as the advantage of ANA measurement before TNFi therapy.

Immunogenicity-unwanted immune responses to biological drugs - can we predict them?

INTRODUCTION

Biological agents (BAs) target molecules involved in disease mechanisms and have modified the natural history of several immune-mediated disorders. All BAs are immunogenic, resulting in the formation of antidrug antibodies (ADAs), which can neutralize drug activity leading to loss of response and potential relapse, or serious adverse events such as infusion hypersensitivity reactions. The production of ADAs is the result of a specific adaptive immune response in which T and B cells are involved.

AREAS COVERED

Factors conditioning the immunogenicity of BAs, including drug-, treatment- and patient-related factors are currently the subject of many studies. Among them, a lot of attention is dedicated to define the impact of BAs structure, the effect of targeting (soluble or membrane) molecules, the impact of interruption of therapy as well as the role of genetic (HLA and non-HLA) predisposing factors and disease activity.

EXPERT OPINION

Knowledge of factors capable of influencing the immunogenicity of BAs may help to understand, in a predictive manner and at the single patient level, the presence of risk factors influencing the production of ADAs and their impact on clinical outcomes.

Laboratory Monitoring of Biological Therapies in Rheumatology: The Role of Immunogenicity

Biological drugs, such as proteins and immunogens, are increasingly used to treat various diseases, including tumors and autoimmune diseases, and biological molecules have almost completely replaced synthetic drugs in rheumatology. Although biological treatments such as anti-tumor necrosis factor (TNF) drugs seem to be quite safe, they cause some undesirable effects, such as the onset of infections due to weakening of the immune system. Given the biological nature of these drugs, they might be recognized as extraneous; this would induce an immune reaction that neutralizes their effectiveness or lead to more serious consequences. Laboratories play a pivotal role in appropriate therapeutic management. The aim of this review was to underline the production of anti-drug antibodies during treatment with biological drugs and highlight the role of laboratories in ensuring appropriate use of these drugs.

Early Adalimumab and Anti-Adalimumab Antibody Levels for Prediction of Primary Nonresponse in Ankylosing Spondylitis Patients

This study aimed at exploring the concentration‐effect relationship of adalimumab and early adalimumab and anti‐adalimumab antibody (AAA) levels in predicting primary nonresponse in a real‐world pilot cohort of patients with ankylosing spondylitis. Thirty‐one patients were included. The Ankylosing Spondylitis Disease Activity Score improved with increasing adalimumab trough level at week 12 and reached a major improvement with levels between 8 and 12 μg/mL. Moreover, weeks 4 and 2 adalimumab levels below 4.28 and 3.37 μg/mL were predictive of primary nonresponse (area under the curve (AUC) = 0.89, 0.88; P = 0.0003, P = 0.034, respectively). Week 4 AAA signal‐to‐noise levels were significantly higher among primary nonresponders, and the cutoff for primary nonresponse prediction was above 5.31 (AUC = 0.81; P = 0.004). Adalimumab trough levels in a range of 8–12 μg/mL are optimum to reach major improvement, and lower adalimumab with higher AAA levels at the early stage (week 4) predict primary nonresponse by supporting proactive monitoring to optimize adalimumab therapy.

Therapeutic drug monitoring of biologicals in rheumatoid arthritis: a disconnect between beliefs and facts

PURPOSE OF REVIEW

To give an overview of recently published articles covering therapeutic drug monitoring (TDM) of biological DMARDs (bDMARDs) in rheumatoid arthritis.

RECENT FINDINGS

In the last 18 months, two clinical studies and nine reviews were found after a systematic literature search. Most (narrative) reviews conclude that TDM should be used to improve biological treatment in rheumatoid arthritis patients, whereas most of the clinical studies (including 13 studies identified earlier) whenever scrutinized do not support this conclusion. This disconnect between sobering data from prediction studies and test-treatment diagnostic studies and optimistic TDM beliefs in reviews is caused by failure to recognize incorrect study designs, false positives because of lack of validation after explorative multiple testing, cherry picking of studies, and incorrect interpretation of test characteristics.

SUMMARY

Serum (anti)-drug level monitoring has been extensively studied in rheumatoid arthritis, but correctly designed and executed interventional prediction studies or test-treatment intervention studies are sparse and mostly negative. In contrast, many reviews advocate use of biological TDM in rheumatoid arthritis. On the basis of current evidence, therapeutic drug monitoring of biologicals cannot be recommended in the treatment of rheumatoid arthritis patients, although two clinical scenarios deserve further study.

Restricted immune activation and internalisation of anti-idiotype complexes between drug and antidrug antibodies

Objectives

Therapeutic antibodies can provoke an antidrug antibody (ADA) response, which can form soluble immune complexes with the drug in potentially high amounts. Nevertheless, ADA-associated adverse events are usually rare, although with notable exceptions including infliximab. The immune activating effects and the eventual fate of these ‘anti-idiotype’ complexes are poorly studied, hampering assessment of ADA-associated risk of adverse events. We investigated the in vitro formation and biological activities of ADA-drug anti-idiotype immune complexes using patient-derived monoclonal anti-infliximab antibodies.

Methods

Size distribution and conformation of ADA-drug complexes were characterised by size-exclusion chromatography and electron microscopy. Internalisation of and immune activation by complexes of defined size was visualised with flow imaging, whole blood cell assay and C4b/c ELISA.

Results

Size and conformation of immune complexes depended on the concentrations and ratio of drug and ADA; large complexes (>6 IgGs) formed only with high ADA titres. Macrophages efficiently internalised tetrameric and bigger complexes in vitro, but not dimers. Corroborating these results, ex vivo analysis of patient sera demonstrated only dimeric complexes in circulation.

No activation of immune cells by anti-idiotype complexes was observed, and only very large complexes activated complement. Unlike Fc-linked hexamers, anti-idiotype hexamers did not activate complement, demonstrating that besides size, conformation governs immune complex potential for triggering effector functions.

Conclusions

Anti-idiotype ADA-drug complexes generally have restricted immune activation capacity. Large, irregularly shaped complexes only form at high concentrations of both drug and ADA, as may be achieved during intravenous infusion of infliximab, explaining the rarity of serious ADA-associated adverse events.

Immunoassay methods used in clinical studies for the detection of anti-drug antibodies to adalimumab and infliximab

We examined the assay formats used to detect anti-drug antibodies (ADA) in clinical studies of the anti-tumour necrosis factor (TNF) monoclonal antibodies adalimumab and infliximab in chronic inflammatory disease and their potential impact on pharmacokinetic and clinical outcomes. Using findings of a recent systematic literature review of the immunogenicity of 11 biological/biosimilar agents, we conducted an ancillary qualitative review of a subset of randomized controlled trials and observational studies of the monoclonal antibodies against anti-TNF factor adalimumab and infliximab. Among studies of adalimumab and infliximab, the immunoassay method used to detect antibodies was reported in 91 of 111 (82%) and 154 of 206 (75%) adalimumab and infliximab studies, respectively. In most adalimumab and infliximab studies, an enzyme-linked immunosorbent assay or radioimmunoassay was used [85 of 91 (93%) and 134 of 154 (87%), respectively]. ADA incidence varied widely among assays and inflammatory diseases (adalimumab, 0-87%; infliximab, 0-79%). Pharmacokinetic and clinical outcomes were only reported for ADA-positive patients in 38 of 91 (42%) and 61 of 154 (40%) adalimumab and infliximab studies, respectively. Regardless of assay format or biological used, ADA formation was associated with lower serum concentrations, reduced efficacy and elevated rates of infusion-related reactions. Consistent with previous recommendations to improve interpretation of immunogenicity data for biologicals, greater consistency in reporting of assay methods and clinical consequences of ADA formation may prove useful. Additional standardization in immunogenicity testing and reporting, application of modern, robust assays that satisfy current regulatory expectations and implementation of international standards for marketed products may help to improve our understanding of the impact of immunogenicity to biologics.

The comparative immunogenicity of biologic therapy and its clinical relevance in psoriatic arthritis: a systematic review of the literature

INTRODUCTION

Biologic agents have demonstrated efficacy in treating patients with psoriatic arthritis (PsA). Biologic agents also have an intrinsic capacity to induce an immune response in patients that could result in unwanted adverse events and/or treatment failure.

AREAS COVERED

In this systematic literature review, the authors document the incidence of immune responses, primarily anti-drug antibodies (ADA), to the biologic therapeutic agents currently in clinical practice for the treatment of PsA. The authors discuss the importance of these responses with respect to clinical practice.

EXPERT OPINION

Our evaluation of the published literature shows that the immune responses to the various biologic therapeutic agents currently being used to treat PsA are similar to those observed for these agents in other rheumatic diseases. Moreover, similar to observations in other rheumatic diseases, the incidence of ADA formation to biologic agents in patients with PsA is often decreased when patients are given concomitant treatment with disease-modifying anti-rheumatic drugs. These data strongly suggest that the immune response is a characteristic of the biologic agent. Using therapeutic drug monitoring may be an approach to assess the immune response to the agent and to mitigate the potential impact on efficacy and safety, and consequently optimize treatment.

Biologics in juvenile idiopathic arthritis: a narrative review

In the past years, pediatric rheumatology has seen a revolution in the treatments for rheumatic diseases, particularly juvenile idiopathic arthritis. Even if nonsteroidal anti-inflammatory drugs (NSAID), intra-articular corticosteroids (IAC) injections, and methotrexate remain the mainstay of the treatment for JIA patients, in aggressive disease, these treatments may be not sufficient to reach disease remission and to prevent long-term disability. Comprehension of immunological mechanisms involved in the pathogenesis of the diseases allowed to conceive new drugs targeting specific steps of the immune response. Several cytokines, like TNF alpha and IL-1, represent a very interesting target for biologic therapies. Due to the efficacy of these therapies, nowadays, "disease remission" in pediatric rheumatology is more and more frequent, especially in juvenile idiopathic arthritis patients, and the long-term outcomes have been significantly improved. Crucial to these advancements have been multicenter controlled clinical trials and long-term safety monitoring.

CONCLUSIONS

Research in pediatric rheumatology has resulted in dramatic advances in diseases management. Biologic treatments have improved physical and functional outcomes and quality of life of patients with rheumatic disease. What is Known: • NSAID, intra-articular injection of corticoids, and methotrexate are the mainstay in treatment of JIA. • In aggressive JIA, these treatments may be not sufficient to reach disease remission and to prevent long term disability. What is New: • In recent years, management of JIA has significantly improved with the development of biologic therapies that allowed children with arthritis to reach a normal growth and to achieve a good long-term functional outcome.

Immunogenicity of Biologics in Chronic Inflammatory Diseases: A Systematic Review

OBJECTIVES

A systematic review was conducted to explore the immunogenicity of biologic agents across inflammatory diseases and its potential impact on efficacy/safety.

METHODS

Literature searches were conducted through November 2016 to identify controlled and observational studies of biologics/biosimilars administered for treatment of rheumatoid arthritis (RA), psoriatic arthritis (PsA), juvenile idiopathic arthritis (JIA), ankylosing spondylitis (AS), non-radiographic axial spondyloarthritis (nr-axSpA), psoriasis (Ps), Crohn's disease, and ulcerative colitis.

RESULTS

Of >21,000 screened publications, 443 were included. Anti-drug antibody (ADAb) rates varied widely among biologics across diseases (and are not directly comparable because of immunoassay heterogeneity); the highest overall rates were reported with infliximab (0-83%), adalimumab (0-54%), and infliximab biosimilar CT-P13 (21-52%), and the lowest with secukinumab (0-1%), ustekinumab (1-11%), etanercept (0-13%), and golimumab (0-19%). Most ADAbs were neutralizing, except those to abatacept and etanercept. ADAb+ versus ADAb- patients had lower rates of clinical response to adalimumab (RA, PsA, JIA, AS, Ps), golimumab (RA), infliximab (RA, PsA, AS, Ps), rituximab (RA), ustekinumab (Ps), and CT-P13 (RA, AS). Higher rates of infusion-related reactions were reported in infliximab- and CT-P13-treated ADAb+ patients. Background immunosuppressives/anti-proliferatives reduced biologic immunogenicity across diseases.

CONCLUSIONS

Based on reviewed reports, biologic/biosimilar immunogenicity differs among agents, with the highest rates observed with infliximab and adalimumab. As ADAb formation in biologic-/biosimilar-treated patients may increase the risk of lost response, the immunogenicity of these agents is an important (albeit not the only) consideration in the treatment decision-making process.

Clinical utility of therapeutic drug monitoring in biological disease modifying anti-rheumatic drug treatment of rheumatic disorders: a systematic narrative review

INTRODUCTION

Biological Disease Modifying Anti-Rheumatic Drugs (bDMARDs) have improved the treatment outcomes of inflammatory rheumatic diseases including Rheumatoid Arthritis and spondyloarthropathies. Inter-individual variation exists in (maintenance of) response to bDMARDs. Therapeutic Drug Monitoring (TDM) of bDMARDs could potentially help in optimizing treatment for the individual patient. Areas covered: Evidence of clinical utility of TDM in bDMARD treatment is reviewed. Different clinical scenarios will be discussed, including: prediction of response after start of treatment, prediction of response to a next bDMARD in case of treatment failure of the first, prediction of successful dose reduction or discontinuation in case of low disease activity, prediction of response to dose-escalation in case of active disease and prediction of response to bDMARD in case of flare in disease activity. Expert opinion: The limited available evidence does often not report important outcomes for diagnostic studies, such as sensitivity and specificity. In most clinical relevant scenarios, predictive value of serum (anti-) drug levels is absent, therefore the use of TDM of bDMARDs cannot be advocated. Well-designed prospective studies should be done to further investigate the promising scenarios to determine the place of TDM in clinical practice.

Clinical practice of analysis of anti-drug antibodies against interferon beta and natalizumab in multiple sclerosis patients in Europe: A descriptive study of test results

Antibodies against biopharmaceuticals (anti-drug antibodies, ADA) have been a well-integrated part of the clinical care of multiple sclerosis (MS) in several European countries. ADA data generated in Europe during the more than 10 years of ADA monitoring in MS patients treated with interferon beta (IFNβ) and natalizumab have been pooled and characterized through collaboration within a European consortium. The aim of this study was to report on the clinical practice of ADA testing in Europe, considering the number of ADA tests performed and type of ADA assays used, and to determine the frequency of ADA testing against the different drug preparations in different countries. A common database platform (tranSMART) for querying, analyzing and storing retrospective data of MS cohorts was set up to harmonize the data and compare results of ADA tests between different countries. Retrospective data from six countries (Sweden, Austria, Spain, Switzerland, Germany and Denmark) on 20,695 patients and on 42,555 samples were loaded into tranSMART including data points of age, gender, treatment, samples, and ADA results. The previously observed immunogenic difference among the four IFNβ preparations was confirmed in this large dataset. Decreased usage of the more immunogenic preparations IFNβ-1a subcutaneous (s.c.) and IFNβ-1b s.c. in favor of the least immunogenic preparation IFNβ-1a intramuscular (i.m.) was observed. The median time from treatment start to first ADA test correlated with time to first positive test. Shorter times were observed for IFNβ-1b-Extavia s.c. (0.99 and 0.94 years) and natalizumab (0.25 and 0.23 years), which were introduced on the market when ADA testing was already available, as compared to IFNβ-1a i.m. (1.41 and 2.27 years), IFNβ-1b-Betaferon s.c. (2.51 and 1.96 years) and IFNβ-1a s.c. (2.11 and 2.09 years) which were available years before routine testing began. A higher rate of anti-IFNβ ADA was observed in test samples taken from older patients. Testing for ADA varies between different European countries and is highly dependent on the policy within each country. For drugs where routine monitoring of ADA is not in place, there is a risk that some patients remain on treatment for several years despite ADA positivity. For drugs where a strategy of ADA testing is introduced with the release of the drug, there is a reduced risk of having ADA positive patients and thus of less efficient treatment. This indicates that potential savings in health cost might be achieved by routine analysis of ADA.