The impact of anti-drug antibodies on drug concentrations and clinical outcomes in rheumatoid arthritis patients treated with adalimumab, etanercept, or infliximab: Results from a multinational, real-world clinical practice, non-interventional study

Objective To assess the incidence of anti-drug antibodies (ADA) in patients with rheumatoid arthritis (RA) treated with the TNF inhibitors etanercept (ETN), adalimumab (ADL), or infliximab (IFX), and determine the potential relationship with trough drug concentration, efficacy, and patient-reported outcomes. Methods This multi-national, non-interventional, cross-sectional study (NCT01981473) enrolled adult patients with RA treated continuously for 6–24 months with ETN, ADL, or IFX. ADA and trough drug concentrations were measured by independent assays ≤2 days before the next scheduled dose. Efficacy measurements included Disease Activity Score 28-joint count (DAS28), low disease activity (LDA), remission, and erythrocyte sedimentation rate (ESR). Targeted medical histories of injection site/infusion reactions, serum sickness, and thromboembolic events were collected. Results Baseline demographics of the 595 patients (ETN: n = 200; ADL: n = 199; IFX: n = 196) were similar across groups. The mean duration of treatment was 14.6, 13.5, and 13.1 months for ETN, ADL, and IFX, respectively. All ETN-treated patients tested negative for ADA, whereas 31.2% and 17.4% patients treated with ADL and IFX, respectively, tested positive. In ADL- or IFX-treated patients, those with ADA had significantly lower trough drug concentrations. There were negative correlations between trough drug levels and both CRP and ESR in ADL- and IFX-treated patients. DAS28-ESR LDA and remission rates were higher in patients without ADA. The rate of targeted medical events reported was low. Conclusion ADA were detected in ADL- and IFX-treated but not ETN-treated patients. Patients without ADA generally showed numerically better clinical outcomes than those with ADA. Trial registration This study was registered on www.ClinicalTrials.gov (NCT01981473).


Introduction
Background 2 Scientific background and explanation of rationale Theories used in designing behavioral interventions

Methods
Participants 3 Eligibility criteria for participants, including criteria at different levels in recruitment/sampling plan (e.g., cities, clinics, subjects) Method of recruitment (e.g., referral, self-selection), including the sampling method if a systematic sampling plan was implemented Recruitment setting Settings and locations where the data were collected Interventions 4 Details of the interventions intended for each study condition and how and when they were actually administered, specifically including: Unit of assignment (the unit being assigned to study condition, e.g., individual, group, community) Method used to assign units to study conditions, including details of any restriction (e.g., blocking, stratification, minimization) Inclusion of aspects employed to help minimize potential bias induced due to non-randomization (e.g., matching) 3 1, 3 Yes Yes Yes 1, 3 Yes 6-7 Yes 7-8 Yes 9 Not applicable Yes 7 Yes 10 Yes 9-10 Yes 10 Yes 9 Not applicable Blinding (masking) 9 Whether or not participants, those administering the interventions, and those assessing the outcomes were blinded to study condition assignment; if so, statement regarding how the blinding was accomplished and how it was assessed.
Unit of Analysis 10 Description of the smallest unit that is being analyzed to assess intervention effects (e.g., individual, group, or community) If the unit of analysis differs from the unit of assignment, the analytical method used to account for this (e.g., adjusting the standard error estimates by the design effect or using multilevel analysis) Statistical Methods

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Statistical methods used to compare study groups for primary methods outcome(s), including complex methods of correlated data Statistical methods used for additional analyses, such as a subgroup analyses and adjusted analysis Methods for imputing missing data, if used Statistical software or programs used

Participant flow 12
Flow of participants through each stage of the study: enrollment, assignment, allocation, and intervention exposure, follow-up, analysis (a diagram is strongly recommended) o Enrollment: the numbers of participants screened for eligibility, found to be eligible or not eligible, declined to be enrolled, and enrolled in the study o Assignment: the numbers of participants assigned to a study condition o Allocation and intervention exposure: the number of participants assigned to each study condition and the number of participants who received each intervention o Follow-up: the number of participants who completed the followup or did not complete the follow-up (i.e., lost to follow-up), by study condition o Analysis: the number of participants included in or excluded from the main analysis, by study condition Description of protocol deviations from study as planned, along with reasons Recruitment 13 Dates defining the periods of recruitment and follow-up Baseline Data 14 Baseline demographic and clinical characteristics of participants in each study condition Baseline characteristics for each study condition relevant to specific disease prevention research Baseline comparisons of those lost to follow-up and those retained, overall and by study condition Comparison between study population at baseline and target population of interest Baseline equivalence 15 Data on study group equivalence at baseline and statistical methods used to control for baseline differences Numbers analyzed 16 Number of participants (denominator) included in each analysis for each study condition, particularly when the denominators change for different outcomes; statement of the results in absolute numbers when feasible Indication of whether the analysis strategy was "intention to treat" or, if not, description of how non-compliers were treated in the analyses Outcomes and estimation 17 For each primary and secondary outcome, a summary of results for each estimation study condition, and the estimated effect size and a confidence interval to indicate the precision Inclusion of null and negative findings Inclusion of results from testing pre-specified causal pathways through which the intervention was intended to operate, if any Ancillary analyses 18 Summary of other analyses performed, including subgroup or restricted analyses, indicating which are pre-specified or exploratory Adverse events 19 Summary of all important adverse events or unintended effects in each study condition (including summary measures, effect size estimates, and confidence intervals)

Interpretation 20
Interpretation of the results, taking into account study hypotheses, sources of potential bias, imprecision of measures, multiplicative analyses, and other limitations or weaknesses of the study Discussion of results taking into account the mechanism by which the intervention was intended to work (causal pathways) or alternative mechanisms or explanations Discussion of the success of and barriers to implementing the intervention, fidelity of implementation Discussion of research, programmatic, or policy implications Generalizability 21 Generalizability (external validity) of the trial findings, taking into account the study population, the characteristics of the intervention, length of follow-up, incentives, compliance rates, specific sites/settings involved in the study, and other contextual issues Overall Evidence

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General interpretation of the results in the context of current evidence and current theory   Table  4 Yes 16-20 Yes 20 Yes 20