Tocilizumab Dose Tapering Based on a Model-Based Algorithm is Feasible in Clinical Practice: A Short Communication.

BACKGROUND: Tocilizumab in the treatment of rheumatoid arthritis (RA) is a potential candidate for concentration-guided tapering because the standard dose of tocilizumab results in a wide range of serum concentrations, usually above the presumed therapeutic window, and an exposure-response relationship has been described. However, no clinical trials have been published to date on this subject. Therefore, the objective of this study was to assess the feasibility of the tapering of intravenous (iv) tocilizumab with the use of a pharmacokinetic model-based algorithm in RA patients. METHODS: A randomized controlled trial with a double-blind design and follow-up of 24 weeks was conducted. RA patients who received the standard of tocilizumab for at least the past 24 weeks, which is 8 mg/kg every 4 weeks, were included. Patients with a tocilizumab serum concentration above 5 mg/L at trough were randomized between concentration-guided dose tapering, referred to as therapeutic drug monitoring (TDM), or the standard 8 mg/kg dose. In the TDM group, the tocilizumab dose was tapered with a recently published model-based algorithm to achieve a target concentration of 4-6 mg/L after 20 weeks of dose tapering. RESULTS: Twelve RA patients were included and 10 were randomized between the TDM and standard dose group. The study was feasible regarding the predefined feasibility criteria and patients had a positive attitude toward therapeutic drug monitoring. In the TDM group, the tocilizumab trough concentration within patients decreased on average by 24.5 ± 18.3 mg/L compared with a decrease of 2.8 ± 12 mg/L in the standard dose group. None of the patients in the TDM group reached the drug range of 4-6 mg/L. Instead, tocilizumab concentrations of 1.6 and 1.5 mg/L were found for the 2 patients who completed follow-up on the tapered dose. No differences in RA disease activity were observed between the 2 study groups. CONCLUSIONS: This study was the first to show that it is feasible to apply a dose-reduction algorithm based on a pharmacokinetic model in clinical practice. However, the current algorithm needs to be optimized before it can be applied on a larger scale.

Antidrug antibody detection for adalimumab depends on the type of assay used: an experimental approach to help clinicians interpret diagnostic data.

OBJECTIVES: To compare different methods of antidrug antibody (ADA) against adalimumab detection in ankylosing spondylitis (AS) patients and the impact of ADA on adalimumab drug levels and mean ASDAS-CRP. METHODS: We used the acid-dissociation-radioimmunoassay (ARIA), antidrug-binding-test (ABT) and a bridging Enzyme-linked Immunosorbent Assay (ELISA) to detect ADA at 4, 12 and 24 weeks of treatment. Patients were divided into groups; all assays negative (All-neg), only ARIA positive (ARIA-only-pos), ARIA and ABT positive, bridging ELISA negative (ARIA/ABT-double-pos) and all assays positive (All-pos). RESULTS: Eighty-three consecutive AS patient were included. At week 4, 18% compared to 11% and 0% of the patients tested positive for ADA in the ARIA, ABT and bridging ELISA, respectively. At week 12 and 24, cumulative 52% and 69% patients tested positive in the ARIA, compared to 27% and 30% patients in the ABT and 2% patients in the bridging ELISA. Adalimumab levels between All-neg and ARIA-only-pos were 9.1 (5.5-12.5) and 8.5 (5.7-12.3). Drug levels differed between ARIA/ABT-double-pos (2.7 (1.3-4.4)) and All-neg (9.1 (5.5-12.5)). All-pos patients had undetectable drug levels. Mean ASDAS-CRP at week 24 differs between All-neg (1.9 (±1.2)), and All-pos (3.8 (±1.9)) and ARIA/ABT-double-pos (2.0 (±1.1)) and All-pos. CONCLUSIONS: The majority of AS patients had detectable ADA against adalimumab in the ARIA. The ARIA detects more ADA compared to the less drug tolerant ABT and bridging ELISA. The clinical relevance depends on the impact on the bio-availability of the drug. A drug level measurement therefore helps to interpret ADA data regardless of type of assay used.

Efficacious transition from reference infliximab to biosimilar infliximab in clinical practice.

OBJECTIVES: To evaluate the transition from reference infliximab Remicade to biosimilar Remsima in patients with rheumatoid arthritis (RA) or psoriatic arthritis (PsA). METHODS: Patients were informed through a letter about the transition to a biosimilar and were subsequently contacted for possible additional questions and whether they agreed upon the transition. Once agreed, Remsima was administered at the same dosage and interval as previous treatment with Remicade. Data on the transition were analyzed in January 2018. The primary outcome was the percentage of patients continuing treatment with Remsima and secondary outcome was the change in disease activity measured with the Disease Activity Score in 28 joints using erythrocyte sedimentation rate (DAS28-ESR). In addition, the reasons for discontinuation with infliximab or restarting Remicade were recorded. RESULTS: In total 47 patients were approached, 45 patients switched from Remicade to Remsima, two patients disagreed upon transition and continued Remicade. At the end of the follow-up period of 2 years, 39 patients (87%) continued with Remsima, three patients (7%) restarted Remicade due to inefficacy according to the patient (this was not objectified by the rheumatologist) 2 (4%) patients switched to another biological due to lack of effect and in one patient (2%) infliximab was stopped because of lung malignancy. Furthermore, the DAS28-ESR remained comparable before and after the switch, with a mean (SD) of 2.34 (±1.02) and 2.31 (±1.11) respectively. CONCLUSION: In our population, 87% of patients continued Remsima during the follow-up period of approximately 2 years. Three patients restarted Remicade, while retaining stable DAS28-ESR.

Dynamics of circulating TNF during adalimumab treatment using a drug-tolerant TNF assay.

Patients with rheumatoid arthritis (RA) can be successfully treated with tumor necrosis factor (TNF) inhibitors, including the monoclonal antibody adalimumab. Once in remission, a proportion of patients can successfully discontinue treatment, indicating that blocking TNF is no longer required for disease control. To explore the dynamics of circulating TNF during adalimumab treatment, we developed a competition enzyme-linked immunosorbent assay that can quantify TNF in the presence of large amounts of TNF inhibitor, i.e., a "drug-tolerant" assay. In 193 consecutive adalimumab-treated patients with RA, we demonstrated that circulating TNF increased in average of >50-fold upon treatment and reached a stable concentration in time for most patients. A similar increase in TNF was found in 30 healthy volunteers after one dose of adalimumab. This implies that TNF in circulation during anti-TNF treatment is not primarily associated with disease activity. During treatment, TNF was in complex with adalimumab and could be recovered as inactive 3:1 adalimumab-TNF complexes. No quantitative association was found between TNF and adalimumab concentrations. Low TNF concentrations at week 4 were associated with a higher frequency of antidrug antibodies (ADAs) at subsequent time points, less frequent methotrexate use at baseline, and less frequent remission after 52 weeks. Also in healthy volunteers, early low TNF concentrations are associated with ADAs. In conclusion, longitudinal TNF concentrations are mostly stable during adalimumab treatment and may therefore not predict successful treatment discontinuation. However, early low TNF is strongly associated with ADA formation and may be used as timely predictor of nonresponse toward adalimumab treatment.