Etanercept Concentrations Research Articles

Response to Biologic Drugs in Patients With Rheumatoid Arthritis and Antidrug Antibodies

There are conflicting data on the association of antidrug antibodies with response to biologic disease-modifying antirheumatic drugs (bDMARDs) in rheumatoid arthritis (RA). To analyze the association of antidrug antibodies with response to treatment for RA. This cohort study analyzed data from the ABI-RA (Anti-Biopharmaceutical Immunization: Prediction and Analysis of Clinical Relevance to Minimize the Risk of Immunization in Rheumatoid Arthritis Patients) multicentric, open, prospective study of patients with RA from 27 recruiting centers in 4 European countries (France, Italy, the Netherlands, and the UK). Eligible patients were 18 years or older, had RA diagnosis, and were initiating a new bDMARD. Recruitment spanned from March 3, 2014, to June 21, 2016. The study was completed in June 2018, and data were analyzed in June 2022. Patients were treated with a new bDMARD: adalimumab, infliximab (grouped as anti-tumor necrosis factor [TNF] monoclonal antibodies [mAbs]), etanercept, tocilizumab, and rituximab according to the choice of the treating physician. The primary outcome was the association of antidrug antibody positivity with EULAR (European Alliance of Associations for Rheumatology; formerly, European League Against Rheumatism) response to treatment at month 12 assessed through univariate logistic regression. The secondary end points were the EULAR response at month 6 and at visits from month 6 to months 15 to 18 using generalized estimating equation models. Detection of antidrug antibody serum levels was performed at months 1, 3, 6, 12, and 15 to 18 using electrochemiluminescence (Meso Scale Discovery) and drug concentration for anti-TNF mAbs, and etanercept in the serum was measured using enzyme-linked immunosorbent assay. Of the 254 patients recruited, 230 (mean [SD] age, 54.3 [13.7] years; 177 females [77.0%]) were analyzed. At month 12, antidrug antibody positivity was 38.2% in patients who were treated with anti-TNF mAbs, 6.1% with etanercept, 50.0% with rituximab, and 20.0% with tocilizumab. There was an inverse association between antidrug antibody positivity (odds ratio [OR], 0.19; 95% CI, 0.09-0.38; P < .001) directed against all biologic drugs and EULAR response at month 12. Analyzing all the visits starting at month 6 using generalized estimating equation models confirmed the inverse association between antidrug antibody positivity and EULAR response (OR, 0.35; 95% CI, 0.18-0.65; P < .001). A similar association was found for tocilizumab alone (OR, 0.18; 95% CI, 0.04-0.83; P = .03). In the multivariable analysis, antidrug antibodies, body mass index, and rheumatoid factor were independently inversely associated with response to treatment. There was a significantly higher drug concentration of anti-TNF mAbs in patients with antidrug antibody-negative vs antidrug antibody-positive status (mean difference, -9.6 [95% CI, -12.4 to -6.9] mg/L; P < 001). Drug concentrations of etanercept (mean difference, 0.70 [95% CI, 0.2-1.2] mg/L; P = .005) and adalimumab (mean difference, 1.8 [95% CI, 0.4-3.2] mg/L; P = .01) were lower in nonresponders vs responders. Methotrexate comedication at baseline was inversely associated with antidrug antibodies (OR, 0.50; 95% CI, 0.25-1.00; P = .05). Results of this prospective cohort study suggest an association between antidrug antibodies and nonresponse to bDMARDs in patients with RA. Monitoring antidrug antibodies could be considered in the treatment of these patients, particularly nonresponders to biologic RA drugs.

Interval prolongation of etanercept in rheumatoid arthritis, ankylosing spondylitis, and psoriatic arthritis: a randomized controlled trial

Objective The majority of patients with a rheumatic disease treated with etanercept may be overexposed. Data regarding etanercept tapering are scarce, particularly in psoriatic arthritis (PsA) and ankylosing spondylitis (AS). We compared extending the dose interval to continuation of the standard dose and studied the success rate of etanercept discontinuation. Etanercept concentrations were measured throughout the study. Method 160 patients with rheumatoid arthritis (RA), PsA, or AS with sustained minimal disease activity (MDA) were enrolled in this 18-month, open-label, randomized controlled trial. The intervention group doubled the dosing interval at baseline and discontinued etanercept 6 months later. The control group continued the standard dose for 6 months and doubled the dosing-interval thereafter. The primary outcome was the proportion of patients maintaining MDA at 6 month follow-up. Results At 6 months, MDA status was maintained in 47 patients (63%) in the intervention group and 56 (74%) in the control group (p = 0.15), with comparable results in all rheumatic diseases. And median etanercept concentrations decreased from 1.50 µg/mL (interquartile range 1.06– 2.65) to 0.46 µg/mL (0.28–0.92). In total, 40% discontinued etanercept successfully with maintained MDA for at least 6 months. Conclusion Etanercept tapering can be done without losing efficacy in RA, PsA, and AS patients in sustained MDA. A substantial proportion of patients could stop etanercept for at least 6 months. In many patients, low drug concentrations proved sufficient to control disease activity. However, the risk of minor and major flares is substantial, even in patients continuing standard dosing.

Serum etanercept concentrations in relation to disease activity and treatment response assessed by ultrasound, biomarkers and clinical disease activity scores: results from a prospective observational study of patients with rheumatoid arthritis

ObjectivesTo identify the therapeutic range for etanercept and to assess the incidence of anti-etanercept antibody formation.MethodsAssociations between etanercept serum concentration and disease activity as well as treatment response were examined...

Low Etanercept Concentrations in Children With Obesity and Juvenile Idiopathic Arthritis.

To evaluate the impact of obesity on etanercept (ETN) drug exposure in children with juvenile idiopathic arthritis (JIA). We conducted a pilot, cross-sectional, observational study in a real-world cohort of children with JIA receiving ETN as standard of care from a single center. We analyzed the relationship between body size and ETN plasma concentrations, adjusting for dosage. Body size was analyzed as a continuous measure using weight and body mass index (BMI) percentiles and categorically using BMI percentile classifications according to the CDC guidelines. We enrolled a total of 29 children. Each child provided one plasma sample for ETN concentration measurement, and all participants were receiving subcutaneous ETN dosed weekly. We observed that the ETN concentration normalized for dose decreased significantly as a function of weight (p = 0.004) and BMI percentile (p = 0.04). Similarly, we observed a progressive decline in mean and median dose-normalized concentrations across higher body size categories. Because of reaching maximum ETN dosage (50 mg), 7 of 8 children (87.5%) with obesity received a weight-based dosage < 0.8 mg/kg/dose. We found that higher body weight and BMI percentile are significantly and negatively associated with ETN drug serum concentration, accounting for differences in dosing. Our data suggest that children who are obese may be routinely under-dosed using current dosing strategies. Inadequate dosing may increase the risk for therapeutic failure and long-term morbidity in a developing child. As a result, characterizing adequate drug exposure in children of all sizes is an important step toward precision dosing.

Lymphatic Distribution of Etanercept Following Intravenous and Subcutaneous Delivery to Rats.

The purpose of this work was to investigate the role of the lymphatic system in the pharmacokinetics of etanercept, a fusion protein. Etanercept 1mg/kg was administered intravenously (IV) and subcutaneously (SC) to thoraciclymph duct-cannulated and sham-operated control rats. Blood and lymph samples were obtained for up to 6days. Model-based SC bioavailability of etanercept was 65.2% in thecontrol group. In lymph-cannulated rats, etanercept concentration in the lymph was consistently lower than in serum following IV dosing; and the concentration in the lymph was significantly higher than in serum after SC injection. The absorption occurred predominantly through the lymphatic pathway (82.7%), and only 17.3% by direct uptake into the central compartment (blood pathway). Lymphatic cannulation reduced the area under the serumconcentration-time curve by 28% in IV group and by 91% in SC group. A mechanistic pharmacokinetic model that combined dual absorption pathways with redistribution of the systemically available protein drug into lymph was developed. The model successfully captured serum and lymph data in all groups simultaneously, and all parameters were estimated with sufficient precision. Lymphatic system was shown to play an essential role in systemic disposition and SC absorption of etanercept.

OP0209 INTERVAL PROLONGATION IN ETANERCEPT-TREATED PATIENTS WITH RHEUMATOID ARTHRITIS, ANKYLOSING SPONDYLITIS OR PSORIATIC ARTHRITIS: AN OPEN-LABEL, RANDOMISED CONTROLLED TRIAL

Background:The majority of patients with a rheumatic disease treated with etanercept may be overexposed. Data regarding etanercept tapering is scarce, particularly in psoriatic arthritis (PsA) and ankylosing spondylitis (AS). Dose reductions can potentially reduce blood drug levels too much, resulting in loss of effect.Objectives:We compared extending the dose interval to continuation of the standard dose and studied the success rate of etanercept discontinuation. Etanercept concentrations were measured throughout the study.Methods:160 consecutive patients with rheumatoid arthritis (RA), PsA or AS with sustained minimal disease activity (MDA) were enrolled in this 18-month, open-label, randomised controlled trial. The intervention group doubled the dosing-interval at baseline and discontinued etanercept 6 months later. The control group continued the standard dose up to 6 months, after which the dosing-interval was doubled. Primary outcome was the proportion of patients maintaining MDA after 6 months follow-up.Results:At 6 months, MDA status was maintained in 47 (63%) patients in the intervention group and 56 (74%) in the control group (p=0.15), with comparable results in all rheumatic diseases. Median etanercept concentrations decreased from 1.50 µg/mL (25-75thpercentile 1.06-2.65) to 0.46 µg/mL (0.28-0.92) after 6 months of interval prolongation (figure 1). In total, 40% discontinued etanercept successfully with maintained MDA for at least 6 months.Figure 1.Median (with Q1 to Q3 boxplots) etanercept concentrations (per protocol) during the first 6 months of follow-up in the intervention group (prolongation; gray boxplots) and the control group (continuation; white boxplots), separated by disease (RA, PsA, AS). Bars represent 10-90 percentile and outliers are shown separately (dots).Conclusion:As observed in RA, etanercept tapering can be safely attempted in PsA and AS patients in sustained MDA. A substantial proportion of patients could stop etanercept for at least 6 months. In many patients low drug concentrations proved sufficient to control disease activity. However, the risk of minor and major flares is substantial, even in patients continuing standard dosing.

Modelling of bioprocess non-linear fluorescence data for at-line prediction of etanercept based on artificial neural networks optimized by response surface methodology

In the last years, regulatory agencies in biopharmaceutical industry have promoted the design and implementation of Process Analytical Technology (PAT), which aims to develop rapid and high-throughput strategies for real-time monitoring of bioprocesses key variables, in order to improve their quality control lines. In this context, spectroscopic techniques for data generation in combination with chemometrics represent alternative analytical methods for on-line critical process variables prediction. In this work, a novel multivariate calibration strategy for the at-line prediction of etanercept, a recombinant protein produced in a mammalian cells-based perfusion process, is presented. For data generation, samples from etanercept processes were daily obtained, from which fluorescence excitation-emission matrices were generated in the spectral ranges of 225.0 and 495.0 nm and 250.0 and 599.5 nm for excitation and emission modes, respectively. These data were correlated with etanercept concentration in supernatant (measured by an off-line HPLC-based reference univariate technique) by implementing different chemometric strategies, in order to build predictive models. Partial least squares (PLS) regression evidenced a non-linear relation between signal and concentration when observing actual vs. predicted concentrations. Hence, a non-parametric approach was implemented, based on a multilayer perceptron artificial neural network (MLP). The MLP topology was optimized by means of the response surface methodology. The prediction performance of MLP model was superior to PLS, since the first is able to cope with non-linearity in calibration models, reaching percentage mean relative error in predictions of about 7.0% (against 12.6% for PLS). This strategy represents a fast and inexpensive approach for etanercept monitoring, which conforms the principles of PAT.

Treatment with etanercept and low monocyte concentration contribute to the risk of invasive aspergillosis in patients post allogeneic stem cell transplantation

Invasive aspergillosis (IA) is a life-threatening complication among allogeneic hematopoietic stem cell transplant (alloSCT) recipients. Despite well known risk factors and different available assays, diagnosis of invasive aspergillosis remains challenging. 103 clinical variables from patients with hematological malignancies and subsequent alloSCT were collected. Associations between collected variables and patients with (n = 36) and without IA (n = 36) were investigated by applying univariate and multivariable logistic regression. The predictive power of the final model was tested in an independent patient cohort (23 IA cases and 25 control patients). Findings were investigated further by in vitro studies, which analysed the effect of etanercept on A. fumigatus-stimulated macrophages at the gene expression and cytokine secretion. Additionally, the release of C-X-C motif chemokine ligand 10 (CXCL10) in patient sera was studied. Low monocyte concentration (p = 4.8 × 10−06), severe GvHD of the gut (grade 2–4) (p = 1.08 × 10−02) and etanercept treatment of GvHD (p = 3.5 × 10−03) were significantly associated with IA. Our studies showed that etanercept lowers CXCL10 concentrations in vitro and ex vivo and down-regulates genes involved in immune responses and TNF-alpha signaling. Our study offers clinicians new information regarding risk factors for IA including low monocyte counts and administration of etanercept. After necessary validation, such information may be used for decision making regarding antifungal prophylaxis or closely monitoring patients at risk.

Adherence to etanercept therapy in rheumatoid arthritis patients during 3 years of follow-up.

ObjectivesTo determine the percentage non-adherence to etanercept in patients with rheumatoid arthritis during three years of follow-up.MethodsDuring study visits in this prospective cohort study, blood samples were taken to determine serum etanercept concentrations using ELISA and patients were asked if they had missed an etanercept dose, at which date and for what reason. Non-adherence was defined as serum etanercept concentration <0.1 μg/mL and no valid reason to miss the prescribed etanercept dose.ResultsIn total, 292 consecutive patients treated with etanercept were included. Most patients had a valid reason to miss their etanercept dose (25/37). In total 12 out of 292 patients (4.1%, 95% confidence interval 2.2–7.2) were non-adherent during the 3 year period. In a small percentage of patients (3.4%, 95% confidence interval 0.8–10.4) who failed to respond to etanercept therapy, according to their rheumatologist, this was associated with inadequate exposure to etanercept and thus non-adherence.ConclusionIn this study, adherence to etanercept therapy was measured using serum etanercept concentration. In most patients an absent etanercept concentration was due to a medical reason. Furthermore, the majority of patients were adherent to etanercept therapy and had adequate drug exposure. In total, only 12 out of 292 patients (4.1%) were non-adherent during 3 years of follow-up. These findings highlight that only a small minority of patients are non-adherent to etanercept treatment, especially compared to adherence rates of other drugs. However, physicians should be aware that in patients failing to respond to treatment, non-adherence is a possible cause.

Etanercept concentration and immunogenicity do not influence the response to Etanercept in patients with juvenile idiopathic arthritis

Objective: To investigate the relationship of clinical response of Juvenile Idiopathic Arthritis (JIA) to etanercept (ETN) with ETN levels, and the presence of anti-drug antibodies to ETN (ADAb).Methods: Prospective study of JIA patients under 18 years old. Clinical and pharmacological data were collected at two visits. JIA clinical inactivity and activity were assessed according to the Wallace criteria and to the Juvenile Arthritis Disease Activity Score (JADAS). ETN and ADAb serum levels assessments were determined using ELISA-based assays.Results: 126 patients were enrolled. The median duration of ETN treatment at inclusion was 569 days (range 53–2340). ADAb were undetectable (<10 ng/ml) in 171/218 (78%) samples and were > 25 ng/mL in 2/218 samples. No significant relationship between ETN concentration and the clinical inactivity status and JIA activity was found using either univariate logistic regression or multiple logistic regression analysis, adjusted on one individual descriptors, time since diagnosis, time of sampling, use of corticosteroids or methotrexate and classification of JIA. No correlation was found between the remission status and the detection of ADAb.Conclusion: This study did not demonstrate any correlation between JIA activity and circulating ETN levels in a large population of patients with JIA previously treated with ETN for at least 1.5 months. As described for adults, our study confirms that ETN is marginally immunogenic in pediatric patients. These results do not support the clinical usefulness of a monitoring of ADAb or ETN concentrations for the management of this group of JIA patients if they fail to achieve clinical inactive disease.

Effect of Etanercept Concentration on Human Islet Integrity

BackgroundEtanercept is widely used as an antiinflammatory drug to improve engraftment after intraportal islet transplantation. In contrast to other immunosuppressive agents, very little is known about detrimental effects of etanercept on islets. The aim of this pilot study was to define the toxic range of etanercept. MethodsHuman islets isolated from 8 donors were cultured for 4–5 days at 37°C in culture medium supplemented with etanercept at concentrations from 2.5 to 40 μg/mL, corresponding to potential in vivo levels within the portal vein. After culture, islet equivalent (IEQ) yield, fragmentation index (islet number/IEQ), purity, viability, and stimulated insulin release (2 vs 20 mmol/L) were assessed and normalized to islets before culture. ResultsYield (73 ± 8%) and viability (91 ± 4%) were highest with 5 μg/mL etanercept. Islet loss was evident when etanercept was ≥10 μg/mL (55 ± 7%; P < .05 vs control). Fragmentation (154 ± 34%; P < .05) was markedly increased and viability (81 ± 4%, P < .05) markedly decreased with etanercept >10 μg/mL. The accumulation of cell debris at concentrations ≥20 μg/mL resulted in a significant reduction of islet purity (84 ± 3%; P < .05). Etanercept did not interfere with stimulated insulin secretion at concentrations ≤10 μg/mL. The maximum stimulation index was noted at 2.5 μg/mL (1.8 ± 0.1). ConclusionsEtanercept is tolerated by isolated human islets at concentrations <10 μg/mL. Our data suggest that the tight range between benefit and toxicity should be considered for dosage and administration of etanercept.

LBEC0101, A Proposed Etanercept Biosimilar: Pharmacokinetics, Immunogenicity, and Tolerability Profiles Compared with a Reference Biologic Product in Healthy Male Subjects.

We performed this study to compare the pharmacokinetic (PK), immunogenicity, and tolerability profiles of etanercept between LBEC0101, a proposed biosimilar, and Enbrel®, the reference biological product. A randomized, double-blind, single-dose, two-treatment, two-period, two-sequence, crossover study was conducted in 48 healthy males. In each period, a single dose of LBEC0101 or Enbrel® was subcutaneously injected at 25mg and serial blood samples for PK evaluation were collected up to 648h post-dose. Serum etanercept concentrations and anti-drug antibodies (ADA) were measured using an enzyme-linked immunosorbent assay and an affinity capture elution assay. Log-transformed maximum concentration (C max) and area under the concentration-time curve (AUCinf) were compared. Tolerability was also evaluated. The serum concentration-time profiles were almost overlapped between LBEC0101 and Enbrel®. Geometric mean ratio (90% confidence intervals) for C max and AUCinf of LBEC0101 to Enbrel® were 1.02 (0.92-1.13) and 0.96 (0.87-1.05), respectively, which were within a conventional bioequivalence criteria of 0.80-1.25. ADA development was also comparable. Both drugs were well tolerated. LBEC0101 showed similar PK, immunogenicity, and tolerability profiles to Enbrel® after a single subcutaneous injection in healthy males. LBEC0101 can be further developed as a potential etanercept biosimilar (ClinicalTrial.gov identifier: NCT01725620).

The association between etanercept serum concentration and psoriasis severity is highly age-dependent.

The association between etanercept serum concentration and psoriasis disease severity is poorly investigated, and currently etanercept serum concentration monitoring that is aiming to optimize the psoriasis treatment lacks evidence. In this prospective study, we investigated the relation between etanercept exposure and disease severity via measuring etanercept concentrations at five consecutive time points in 56 psoriasis patients. Disease severity assessments included the Psoriasis Area and Severity Index (PASI), body surface area (BSA) and Physician Global Assessment (PGA), and etanercept and anti-etanercept antibody concentrations were determined every 3 months for a period of 1 year. The present study demonstrated that the association between etanercept concentration and psoriasis severity is age-dependent: when patients were stratified into three groups, patients in the youngest age group (-50 years) showed a lower PASI at a higher etanercept concentration (β = -0.26), whereas patients in the oldest age group (+59 years) showed the opposite trend (β =0.22). Similar age effects were observed in the relation of etanercept concentration with BSA (P=0.02) and PGA (P=0.02). The influence of age and length of time in therapy on the etanercept concentration-disease severity relation was unaffected by body mass index (BMI) or any other possible confounder. Incidence of anti-etanercept antibodies was low (2%). The age-dependent relation between etanercept serum concentrations is both unexpected and intriguing and needs further investigation.

Etanercept protects rat cardiomyocytes against hypertrophy by regulating inflammatory cytokines secretion and cell apoptosis.

We aimed to investigate the effect of etanercept, a tumor necrosis factor-α (TNF-α) inhibitor, on rat cardiomyocyte hypertrophy and its underlying mechanism. Primary neonatal rat cardiomyocytes were isolated from Sprague-Dawley rats. The model of rat cardiomyocyte hypertrophy was induced by endothelin, and then treated with different concentrations of etanercept (1, 10, and 50 μM). After treatment, cell counts, viability and cell apoptosis were evaluated. The mRNA levels of myocardial hypertrophy marker genes, including atrial natriuretic factor (ANF), matrix metalloproteinase (MMP)-9 and MMP-13, were detected by qRT-PCR, and the expressions of apoptosis-related proteins (Bcl-2 and Bax) were measured by western blotting. The protein levels of transforming growth factor-β1 (TGF-β1), interleukin (IL)-1β, IL-6, leukemia inhibitory factor (LIF) and cardiotrophin-1 (CT-1) were determined using enzyme linked immunosorbent assay (ELISA) kits. In the present study, TNF-α level in cardiomyocytes with hypertrophy was significantly enhanced (P<0.05). Compared to the model group, cell number and viability were significantly increased and ratio of apoptotic cells was reduced by etanercept (P<0.05, P<0.01, or P<0.001). In addition, etanercept remarkably reduced the mRNA levels of ANF, MMP-9 and MMP-13, inhibited the expression of Bax, and increased the expression of Bcl-2 compared to the model group (P<0.05). ELISA results further showed that etanercept lowered the levels of IL-1β, IL-6, LIF and CT-1 but not TGF-β1 compared to the model group (P<0.05). Etanercept may protect rat cardiomyocytes from hypertrophy by inhibiting inflammatory cytokines secretion and cell apoptosis.

Comparison of Three Assays to Quantify Infliximab, Adalimumab, and Etanercept Serum Concentrations.

To optimize treatment of inflammatory diseases, interest in the measurement of anti-tumor necrosis factor alpha (anti-TNFα) serum drug concentrations is increasing. Preferably, assays for the detection of these drugs should be compared using the same reference material. In this study, 2 commercially available enzyme-linked immunosorbent assays (ELISAs) and a commercially available bioassay for the determination of anti-TNFα drugs are compared. Serum samples from infliximab-, adalimumab-, and etanercept-treated patients, control samples from ustekinumab-treated patients, and healthy donors were obtained. ELISAs manufactured by Sanquin and Theradiag and the iLite reporter gene-based bioassay from Biomonitor were compared. Sanquin, Theradiag, and iLite assays concordantly (100%) detected infliximab, adalimumab, and etanercept in the relevant patient groups. The Sanquin ELISAs specifically detected the anti-TNFα drug they were designed for, whereas the Theradiag and iLite showed cross-reactivity with other anti-TNFα drugs. Ustekinumab was not detected in any of the assays. Sanquin, Theradiag, and iLite exhibited linear quantitative correlation for all drug concentration assays. However, there were statistically significant quantitative differences in measured concentrations. All 3 commercially available assays seem suitable for therapeutic drug monitoring of anti-TNFα drugs, allowing sensitive and comparable detection of infliximab, adalimumab, and etanercept concentrations, however with differences in specificity and recovery.

Positive correlation between etanercept concentration and the decrease in Psoriasis Area and Severity Index scale value.

Background In the case of psoriatic patients, only a limited number of studies have related serum biological therapies and antidrug antibodies levels to clinical response. With respect to etanercept, the available evidence has not shown any relationship yet. Objective The aim of this study was to determine if there is any correlation among etanercept serum levels, the presence of anti-etanercept antibodies and clinical response to this treatment in psoriatic patients. Setting A 1500-bed hospital (A Coruña University Hospital Complex). Method A retrospective observational study in psoriatic patients treated with etanercept (50mg once weekly) was carried out. Psoriasis Area and Severity Index scale and adverse reactions were recorded at the time of the extraction sample. The pharmacokinetic monitoring was evaluated at the previous time points by extracting peripheral blood samples before the dose administration. Etanercept and anti-etanercept antibodies concentrations were quantified by two sandwich-type ELISA immunoassays. The patients were classified into three groups (good, partial and nonresponders) in accordance with the treatment efficacy at the blood assessment moments. The Kruskall-Wallis test and Spearman correlation assay were used to assess the efficacy and incidence of adverse effects according to the etanercept concentration and anti-etanercept antibodies, considering p values of <0.05 as statistically significant. This statistical analysis was conducted using SPSS software (version19.0). Main outcome measures Etanercept and anti-etanercept antibodies trough serum levels and clinical response. Results 38 patients were included. 26 patients (68.4%) were good, 5 (13.2%) were partial and 7 (18.4%) were non-responders. There was no significant difference with respect to etanercept levels: 2.7μg/mL (range 0.7-5.6) versus 2.2μg/mL (range 1.0-3.5) versus 1.73μg/mL (range 0.1-2.3), respectively (p=0.085). Nevertheless, a positive correlation between percentage decrease in the Psoriasis Area and Severity Index scale value with respect to the baseline value and etanercept concentration was found (p=0.011). No anti-etanercept antibodies were detected; nor was there a significant difference in the incidence of adverse effects (p=0.8523). Conclusions Our results showed a positive correlated between etanercept concentration and the percentage decrease in the Psoriasis Area and Severity Index scale value. The incidence of anti-etanercept antibodies in psoriatic patients was low.

The effects in vitro of TNF-α and its antagonist ‘etanercept’ on ejaculated human sperm

Tumour necrosis factor (TNF)-α is primarily involved in the regulation of cell proliferation and apoptosis; in addition it possesses pro-inflammatory properties. Anti-TNF-α strategies involve either administration of anti-TNF-α antibody or soluble TNF receptor to mop up circulating TNF-α. Etanercept, a recombinant human TNF-α receptor, was found to be effective in the treatment of rheumatoid arthritis. The impact of TNF-α inhibitors on human fertility is of notable interest. This in vitro study investigated the effect of different concentrations of TNF-α and etanercept used alone or in combination on sperm viability, motility, mitochondrial function, percentage of apoptosis and chromatin integrity in swim-up selected human spermatozoa. A negative effect of TNF-α (300 and 500ng mL-1) and etanercept (from 800µg mL-1 to 2000µg mL-1) individually on sperm viability, motility, mitochondrial function, percentage of apoptotic spermatozoa and sperm DNA integrity was demonstrated. However, at concentrations of 100 and 200µg mL-1, etanercept can block, in a significant way, the toxic effects of TNF-α (500ng mL-1) on studied sperm characteristics. Our results confirm that TNF-α has a detrimental effect on sperm function and suggest, for the first time, that etanercept may counteract the in vitro toxic action of TNF-α. This data appears to be quite promising, although further studies, both in vivo and in vitro, are needed to understand the exact mechanism of action of TNF-α and TNF-α antagonists on sperm function.

Characterization and Application of a Unique Panel of Monoclonal Antibodies Generated against Etanercept.

The clinical response in ankylosing spondylitis (AS) patients treated with biologic agents can be influenced by pharmacokinetic variability among and within these patients. Therapeutic drug monitoring is seen as a valuable tool to improve patient care. The aim of this study was to generate a panel of mAbs toward etanercept (ETN) and to determine ETN and anti-ETN concentrations in AS patients. mAbs against ETN (MA-ETN) were generated using hybridoma technology. For quantification of ETN concentrations, a mAb-based TNF-coated ELISA and a mAb/mAb-based sandwich-type ELISA were developed. For evaluation of the anti-ETN Ab response, a bridging ELISA, as well as a functional cell-based assay, were constructed. Disease activity of the AS patients was measured with the AS Disease Activity Score (ASDAS). Active disease was defined as ASDAS ≥ 2.1. A total of 59 of 76 generated mAbs were ETN specific and were characterized further. Fifty-one mAbs revealed inhibitory properties in a cell-based assay. Analysis of serum concentrations of 21 ETN-treated AS patients with the TNF/MA-ETN68C5-HRP ELISA and the MA-ETN63C8/MA-ETN61C1-HRP ELISA revealed a good Pearson's r (+0.974) but a poor intraclass correlation coefficient (+0.528) as the result of underestimation of the values in the former ELISA. At 24 wk, ETN concentrations were similar in patients with ASDAS < 2.1 and ≥ 2.1. Anti-ETN Abs were not detected in any of the patient samples tested. In conclusion, highly sensitive mAb-based immunoassays were developed for quantification of ETN and anti-ETN concentrations. The impact of these methods needs to be evaluated further in clinical practice.

Biodistribution of etanercept to tissues and sites of inflammation in arthritic rats.

Many monoclonal antibodies (mAbs) and other protein drugs have targets usually residing within tissues, making tissue concentrations of mAbs relevant to their pharmacologic effects. Therefore, knowledge of tissue distribution kinetics is important to better understand their pharmacokinetics and pharmacodynamics. The tissue distribution of mAbs is affected by many physiologic factors that may be altered in disease status. In the present work, we studied the tissue distribution kinetics of the fusion protein etanercept in inflamed joint tissues and examined the impact of inflammation on the tissue distribution of etanercept. Etanercept concentration profiles in plasma, blister fluid, and different tissues were obtained from healthy and collagen-induced arthritic (CIA) rats by use of a fluorescence quantification method via IRDye800CW labeling. Stepwise minimal and full physiologically based pharmacokinetic (PBPK) approaches were applied to characterize the distribution kinetics of etanercept in tissues in healthy and diseased animals. Etanercept exhibited modest tissue access (tissue/plasma area under the concentration curve [AUC] ratios 0.03-0.15 and estimated tissue reflection coefficients [σ] of 0.6-1.0), but with good penetration into arthritic paws (tissue/plasma AUC ratio 0.23 and σ 0.36). Etanercept exposure in the inflamed paws of CIA rats was approximately 3-fold higher than in normal paws taken from either CIA or healthy rats (tissue/plasma AUC ratios 0.23 versus 0.07 and σ 0.36 versus 0.71). The tissue distribution kinetics of etanercept in arthritic paws were well characterized with PBPK modeling approaches. Etanercept shows good penetration to arthritic paws in CIA rats. Our study indicates that inflammation produced increased tissue distribution of etanercept in CIA rats.

Clinical utility of random anti-tumour necrosis factor drug testing and measurement of anti-drug antibodies on long-term treatment response in rheumatoid arthritis

BackgroundUp to 40% of patients with rheumatoid arthritis treated with anti-tumour necrosis factor (TNF) drugs do not respond because of primary inefficacy or loss of response. Although one explanation is that immunogenicity leads to the development of anti-drug antibodies and low drug concentrations, the clinical usefulness of pharmacological monitoring is debated. Our aim was to assess whether the presence of anti-drug antibodies and non-trough drug concentrations could predict treatment response in patients with rheumatoid arthritis treated with anti-TNF drugs. Methods331 patients were selected from a multicentre prospective cohort (160 treated with adalimumab, 171 etanercept). Serum samples were collected at 3, 6, and 12 months after treatment initiation. Anti-drug antibodies were measured with RIA, drug concentrations with ELISAs, and Disease Activity Score in 28 joints (DAS28) at each timepoint. Linear and logistic regression, generalised estimating equation (GEE), and receiver operating characteristic curves were used to test the association and predictive value of anti-drug antibodies and non-trough drug concentrations on treatment response (ΔDAS28). Findings835 serial samples were tested (414 adalimumab, 421 etanercept). Anti-adalimumab antibodies were detected in 31 (24·8%) of 125 patients who had completed 12 month follow-up and none of the etanercept patients. The presence of anti-drug antibodies was associated with lower adalimumab concentrations (Spearman r=–0·66, p=0·0041). At 3 months, anti-drug antibody formation and low adalimumab concentrations were significant predictors of poor treatment response at 12 months (area under curve [AUC] 0·68, 95% CI 0·54–0·81, and 0·66, 0·55–0·77, respectively; and both combined 0·71, 0·57–0·85). Adalimumab concentration was the most significant independent predictor of ΔDAS28 after adjustment for confounders (regression coefficient 0·12, 95% CI 0·06–0·18; p=0·003). High etanercept concentrations were associated with better treatment response (p=0·01), but low concentrations at 3 months were not a significant predictor of poor treatment response at 12 months (AUC 0·58, 95% CI 0·46–0·70). In the combined GEE model including adalimumab and etanercept, a body-mass index of 30 kg/m2 or more was associated with low drug concentrations (regression coefficient 0·78, 95% CI 0·37–1·18; p<0·0001). InterpretationPharmacological testing in anti-TNF initiated patients is clinically useful even in the absence of trough levels. At 3 months, presence of anti-drug antibodies and low adalimumab concentrations are a significant predictor for poor treatment response at 12 months. Strengths of this study include a large, prospective cohort and use of RIA to measure antibodies (less prone to drug interference). Although non-trough concentrations might have underestimated the frequency of antibodies, their presence still predicted response. FundingMJ is a MRC Clinical Training Fellow supported by the North West England Medical Research Council Fellowship Scheme in Clinical Pharmacology and Therapeutics, which is funded by the UK Medical Research Council (grant number G1000417/94909), ICON, GlaxoSmithKline, AstraZeneca, and the Medical Evaluation Unit. Arthritis Research UK (grant ref 20385).