Measurement Of Anti-drug Antibodies Research Articles

DOP059 Lack of significance of treatment-emergent anti-drug antibodies on efficacy of mirikizumab in patients with moderately-to-severely active Crohn’s Disease: Results from the VIVID-1 study

Abstract Background Results from the phase 3 VIVID-1 study, NCT03926130, showed efficacy of mirikizumab (miri), a p19-directed antibody against IL-23, in patients with moderately-to-severely active Crohn’s disease (CD). VIVID-1 co-primary and gated endpoints, including comparison with ustekinumab (uste), are already reported1, 2. Immunogenicity is recognised as a leading contributor of loss of response to biologic therapies for approved treatments in inflammatory bowel disease3. Patients treated with miri were tested for anti-drug antibodies (ADA) in VIVID-1. We present results showing the immunogenicity effect on miri-treated patients. Methods Patients were randomised 6:3:2 to miri (N=579), uste (N=287), or placebo (N=199) in VIVID-1. Miri was administered intravenously at week (W) 0, W4 and W8 (induction), then subcutaneously every 4 weeks from W12 to W52 (maintenance). A validated acid-dissociation drug resistant assay was developed for the measurement of ADA in multiple patient samples throughout the study. Patients in the primary analysis set who were randomised to miri at baseline and had a non-missing baseline ADA result and at least 1 non-missing postbaseline ADA result were used in the analyses. The potential impact of ADA and ADA titer on efficacy outcomes was assessed using the co-primary efficacy endpoints of VIVID-12. These endpoints were assessed according to the presence or absence of treatment emergent (TE) ADA and by titer groupings. Results were analysed separately for low- and high-titer TE ADA based on a cutoff of 1:160, considering high-titer TE ADA may be more associated with clinical outcomes4. Results Of 571 participants in the analysis population, 12.6% (n=72) were TE ADA-positive. The majority (66.7%, n=48) of TE ADA-positive patients had ADA titers of <1:160. Figure shows that similar proportions of TE ADA-positive and TE ADA-negative patients achieved composite clinical remission and endoscopic improvement after 52 weeks of continuous treatment. Similarly, the subgroup of patients with high-titer TE ADA ≥1:160 achieved comparable rates of composite clinical remission and endoscopic improvement as TE ADA-negative patients. No overall clinically meaningful differences were observed based on TE ADA positivity. Conclusion The results from this study show that the overall immunogenicity of miri is low. TE ADA did not adversely impact the clinical efficacy of miri for patients with moderately-to-severely active CD. This was also true in the subgroup of patients with high-titer TE ADA.

Replacing serum with dried blood microsampling for pharmacokinetics, viral neutralisation and immunogenicity bioanalysis supporting future paediatric development of RSM01, a candidate respiratory syncytial virus neutralising monoclonal antibody

BackgroundVirus neutralising antibodies in serum are considered key correlates of protection for vaccines and monoclonal antibodies against respiratory syncytial virus (RSV). RSM01 is a novel, highly-potent, half-life-extended and fully-human monoclonal antibody candidate targeting the RSV prefusion F protein. Currently in Phase 1 development, RSM01 is primarily being developed to potentially provide an effective and affordable RSV prevention strategy in low- and middle-income countries. To evaluate the ability of dried blood collection to generate data sets and conclusions comparable to serum collection, we compared pharmacokinetics (PK) of RSM01, immunogenicity, and virus neutralisation for dried capillary blood samples with serum samples.MethodsRSM01 PK, anti-drug antibodies (ADA), and RSV-neutralising antibodies from the Phase 1 trial were analyzed and compared between matched serum and dried blood samples. Deming regression analysis was performed using baseline-corrected values to evaluate correlation between measurements in liquid serum versus dried blood.ResultsThe analysis showed good correlation (R2 > 0.95) between individual RSM01 concentrations measured in both serum and capillary blood. Analysis of RSM01 PK parameters in capillary blood yielded equivalent conclusions as from serum. A strong correlation (R2 > 0.95) was observed between RSV neutralising activity measured in both serum and capillary blood. In addition, RSV neutralising activity was correlated with RSM01 concentrations in both serum and capillary blood data sets. For ADA, individual sample results had 96% agreement (290/302) and overall participant ADA status had 93% agreement (52/56).ConclusionsBoth RSM01 concentrations and RSV neutralising activity showed a strong correlation between the serum and blood measurements. ADA measurements also had an agreement of > 90% for individual samples and overall participant status. Our results demonstrate that dried blood is a suitable specimen type for collection and evaluation in the RSM01 clinical development program and shows promise as a useful approach to reduce patient burden in clinical trials, particularly for infants in low- and middle-income countries.Trial RegistrationClinicaltrials.gov NCT05118386 November 12, 2021.

Simultaneous isotyping and semi-quantitation of anti-drug antibodies to an IgG1 biotherapeutic using hybrid LBA-LC-MS/MS.

Commonly, ligand-binding platforms are being used for immunogenicity assessment, but with the recent advent of liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) for protein quantification, this technology has become an alternative for the measurement of anti-drug antibodies (ADAs), when combined with an immunocapture step to extract them out of the biological sample. The monoclonal antibody adalimumab was immobilized on magnetic beads to isolate ADAs against this drug from serum samples. Multiple repetitions of immunopurification were used to minimize nonspecific binding and improve drug tolerance while maintaining sufficient recovery. A subsequent tryptic digestion released peptides, from which unique peptide sequences, originating from the constant region of seven ADA subclasses, were selected. These were then analyzed by LC-MS/MS against (unextracted) subclass-specific reference standards for semi-quantification. With two immunocapture and two immunopurification steps, the method simultaneously measures the ADA subclasses IgG1, IgG2, IgG3, IgG4, IgM, IgE and IgA within their relevant ranges, with good repeatability and drug tolerance, and limited interference of endogenous immunoglobulins. The method was successfully applied for the analysis of serum samples of subjects dosed with adalimumab. Hybrid LBA-LC-MS/MS is a viable platform for measuring ADAs and adds value, especially when ADA isotyping is needed.

Immunogenicity of Atezolizumab: Influence of Testing Method and Sampling Frequency on Reported Anti-drug Antibody Incidence Rates.

Measurement of anti-drug antibodies (ADA) to assess the incidence of ADA in a clinical trial is a critical step in immunogenicity assessment during the development of a protein therapeutic. We developed novel graphical approaches to illustrate clinical trial ADA data for the PD-L1 inhibitor atezolizumab (Tecentriq) that included a systematic analysis of the impact of the timing of ADA sampling and ADA assay drug tolerance on reported ADA incidence. We found that approaches used across the industry for ADA incidence analysis provide a limited view of immunogenicity in oncology studies, where ADA detection may be confounded by both drug dosage and patient attrition. Moreover, these approaches can miss important temporal information about the immune response. Our results demonstrated that the methodology of ADA assessment for the atezolizumab program was specifically designed to capture most ADA responses to ensure accurate reporting of ADA incidence. We further showed that the use of sparse sampling and/or ADA test methods with insufficient drug tolerance may result in a significant underreporting of ADA incidence. We conclude that the comparison of ADA incidence between different drugs can be highly misleading and that a test method with appropriate sensitivity in the presence of the drug and a clinical sampling scheme that is aligned with ADA responses to a drug is required to accurately report ADA incidence.

Strategy and validation of a nonclinical generic plug-and-play antidrug antibody method for human monoclonal antibody biotherapeutics.

The measurement of antidrug antibodies (ADA) in nonclinical studies provides limited value becausethe formation and incidence of nonclinical ADA does not translate to clinical experience. The formation and presence of ADA in nonclinical species can, however, correlate to reduced drug exposure and safety observations including vasculitis and immune complex disease. Generic ADA methods for humanized monoclonal antibody biotherapeutics mitigate the need to develop bespoke ADA methods during nonclinical drug development. A drug-tolerant, sensitive, generic ADA immunoassay has been developed and validated for measuring ADA in cynomolgus monkey serum samples, allowing for immediate qualification of future monoclonal antibody biotherapeutics. This approach allows us to differentiate complexed and free ADA in a rapidly deployable manner when needed.

Characterization of anti-drug antibody dynamics using a bivariate mixed hidden-markov model by nonlinear-mixed effects approach

Biological therapies may act as immunogenic triggers leading to the formation of anti-drug antibodies (ADAs). Population pharmacokinetic (PK) models can be used to characterize the relationship between ADA and drug disposition but often rely on the ADA bioassay results, which may not be sufficiently sensitive to inform on this characterization.In this work, a methodology that could help to further elucidate the underlying ADA production and impact on the drug disposition was explored. A mixed hidden-Markov model (MHMM) was developed to characterize the underlying (hidden) formation of ADA against the biologic, using certolizumab pegol (CZP), as a test drug. CZP is a PEGylated Fc free TNF-inhibitor used in the treatment of rheumatoid arthritis and other chronic inflammatory diseases.The bivariate MHMM used information from plasma drug concentrations and ADA measurements, from six clinical studies (n = 845), that were correlated through a bivariate Gaussian function to infer about two hidden states; production and no-production of ADA influencing PK. Estimation of inter-individual variability was not supported in this case. Parameters associated with the observed part of the model were reasonably well estimated while parameters associated with the hidden part were less precise. Individual state sequences obtained using a Viterbi algorithm suggested that the model was able to determine the start of ADA production for each individual, being a more assay-independent methodology than traditional population PK. The model serves as a basis for identification of covariates influencing the ADA formation, and thus has the potential to identify aspects that minimize its impact on PK and/or efficacy.

Therapeutic Drug Monitoring of Anti-TNFα Inhibitors: A Matter of Cut-Off Ranges.

Therapeutic drug monitoring (TDM) is a useful tool for optimising the use of anti-TNFα inhibitors in patients with inflammatory bowel diseases (IBDs). Recently, point-of-care methods for the quantification of drug levels and anti-drug antibodies (ADAs) have been developed to overcome the limitations of conventional enzyme-linked immunoabsorbent assays (ELISAs). Here, we evaluated the performance, interchangeability, and agreement between an automated ELISA-based immunoassay (CHORUS Promonitor) and the lateral flow assay (RIDA®QUICK) for the quantification of infliximab (IFX, n = 65) and adalimumab (ADM, n = 58) plasma levels in IBD patients. Thirty-two samples for IFX and twenty-three samples for ADM that tested positively for the presence of ADAs were also used. Overall, data analysis showed a good agreement of ADM trough concentrations (R2 = 0.75) between the two assays as well as for ADA measurement (K > 0.8). However, IFX levels highlighted a weak correlation (R2 = 0.58) between the two kits, with the RIDA®QUICK assay overestimating IFX plasma values by 30% when compared to the CHORUS Promonitor kit. Results from this study show that the two assays are not quantitatively and qualitatively interchangeable due to substantial discrepancies in some results. Accordingly, the same assay should be used for the longitudinal follow-up of IBD patients.

CBX-12-101: A first-in-human study of CBX-12, an alphalex peptide drug conjugate (PDC) in patients (pts) with advanced or metastatic solid tumors.

3087 Background: Tumor-targeted drug delivery technologies are urgently needed to overcome conventional chemotherapy’s lack of tumor selectivity. Alphalex conjugates, which contain a pH-low insertion peptide (pHLIP), a linker and a payload, are designed to overcome this lack of selectivity. Unlike antibody drug conjugates, alphalex PDCs target tumors in an antigen-agnostic manner. At pH ≥7.0, the peptide is unstructured. In the low-pH tumor microenvironment the peptide forms an alpha helix and inserts directionally into the tumor cell membrane delivering the linker and payload intracellularly where the linker is cleaved releasing the payload in the cytosol. CBX-12 consists of the pH-sensitive peptide, a self-immolating linker, and the topoisomerase 1 (TOP1) inhibitor exatecan. Methods: In this Phase 1 trial, cohorts of pts were treated with escalating doses of CBX-12 in a 3 + 3 design on three dosing schedules: daily x 5 every 3 weeks, daily x 3 every 3 weeks or once weekly. The primary objectives are safety, tolerability and to determine the MTD and/or RP2D. Secondary and exploratory objectives include evaluation of plasma PK of CBX-12 and exatecan, anti-tumor activity per RECIST v1.1, and measurement of anti-drug antibodies. Results: As of 26 Jan 2023, 42 pts have been treated on three schedules. The most frequent treatment-related AEs (TRAEs) were anaemia (42.9%), nausea (38.1%), fatigue (33.3%), ANC and WBC decreased (33.3% each), vomiting (26.2%), diarrhoea (23.8%) and thrombocytopenia (19.0%). The most frequent Gr3/4 TRAEs were ANC decreased (28.6%), anemia (23.8%), WBC decrease (16.7%), thrombocytopenia (14.3%). Dose limiting toxicity was observed in 6 pts: myelosuppression (6 pts) febrile neutropenia (2 pts), and sepsis (2 pts). Responses were observed in 2 of 9 pts with ovarian cancer and 2 of 8 with breast cancer. The MTD on the daily x 3 schedule is 45mg/m2. Dose evaluation continues on the weekly schedule. Conclusions: In this FIH study of a pH-targeting alphalex PDC, CBX-12 demonstrated single-agent antitumor activity including 4 responses with the dominant toxicity of myelosuppression. Phase 2 expansion cohorts are planned in pts with platinum-resistant ovarian cancer and hormone-receptor positive, HER2 negative breast cancer. Clinical trial information: NCT04902872 .

Abstract CT253: Phase 1/2 study of the safety, pharmacokinetics, and preliminary clinical activity of BT7480 in patients with nectin-4 associated advanced malignancies

Abstract Background: Bicycles are a novel class of synthetic molecules formed by using a central scaffold to constrain short linear peptides into a stabilized bi-cyclic structure, which can then be readily conjugated to other molecules. BT7480 is a trimeric first-in-class Bicycle tumor-targeted immune cell agonist (Bicycle TICA) comprised of two unique bicyclic peptides: one that binds to Nectin-4 and two identical Bicycles that bind and agonize CD137. The resulting multi-specific molecule stimulates an immune response in the presence of both Nectin-4-expressing tumor cells as well as CD137-expressing immune cells. Nectin-4, a cell adhesion molecule overexpressed on the surface of tumor cells and CD137, a costimulatory receptor expressed on immune cells, are co-expressed in a variety of solid tumors including lung, head and neck, breast, ovarian, and bladder. Co-ligation of Nectin-4 and CD137 by BT7480 is hypothesized to induce oligomerization and activation of CD137, resulting in a tumor-localized costimulatory signal. A favorable preclinical profile supported the initiation of this first-in-human study to investigate the safety and efficacy of BT7480 in patients with solid tumors associated with Nectin-4 expression (NCT05163041). Methods: This is a phase 1/2, open-label, multicenter study to assess safety, clinical activity, and pharmacokinetics (PK) and pharmacodynamics (PD) of BT7480. Patients must have an advanced malignancy associated with Nectin-4 expression that is not eligible for standard therapy. Additional key criteria include ≥18 years of age, ECOG of 0 or 1, adequate organ function, and no prior therapy with a CD137-targeted agent. Patients are treated at one of the escalating doses (3+3 design) by weekly IV infusion in a 4-week cycle. Primary objectives are to assess safety (phase 1) and clinical activity per RECIST v1.1 (phase 2). Secondary objectives include assessment of PK parameters, measurement of anti-drug antibodies, and evaluation of CD137 target engagement in blood. Key exploratory objectives include evaluating pharmacogenomics, ctDNA, and biomarkers in blood and tumors associated with pharmacological activity, including signals of immune activations and target expression. PK and PD analyses will be performed to support dose escalation decisions and to further the understanding of safety and clinical activity signals as a result of treatment with BT7480. This study is actively recruiting. Citation Format: Thomas R. Evans, Afshin Dowlati, Juanita S. Lopez, Mohammed M. Milhem, Jordi Rodón Ahnert, Alexander Spira, Richard D. Carvajal, Matthew Zibelman, Sebastien J. Hazard, Amy Dickson, Lei Xu, Heather Cohen, Justin Bader, Kristen Hurov, Rajiv Sharma, Dominic Smethurst, Kyriakos P. Papadopoulos. Phase 1/2 study of the safety, pharmacokinetics, and preliminary clinical activity of BT7480 in patients with nectin-4 associated advanced malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT253.

Immunomodulator comedication promotes the reversal of anti-drug antibody-mediated loss of response to anti-TNF therapy in inflammatory bowel disease

PurposeLoss of therapeutic response (LOR) due to anti-drug antibodies (ADA) against tumor necrosis factor (TNF) inhibitors is common in patients with inflammatory bowel disease (IBD). We aimed to investigate whether immunomodulator comedication can reverse the immunogenic LOR to TNF inhibitors in IBD.MethodsIn this real-world retrospective cohort study, 123 IBD patients with neutralizing ADA to infliximab or adalimumab and concomitant subtherapeutic trough levels were screened for clinical LOR. Subsequent ADA and trough level measurements and clinical outcomes were analyzed for patients who received either immunomodulator comedication or dose intensification of infliximab or adalimumab to overcome LOR.ResultsFollowing immunogenic LOR, the initial anti-TNF regimen was optimized in 33 patients. In univariable and multivariable logistic regression analyses, immunomodulator comedication was identified as the crucial factor for regaining clinical remission and ADA clearance. Detectable trough levels (≥ 0.98 or ≥ 1.00 mg/L, respectively) had optimal predictive performance for both endpoints in receiver operating characteristics curves [area under the curve 0.86 (95% confidence interval 0.68–1.00) for regaining clinical remission, 0.87 (0.71–1.00) for ADA clearance]. Furthermore, 11/20 patients (55%) on a comedication with azathioprine or methotrexate and 2/13 patients (15%) receiving anti-TNF dose intensification exclusively (P = 0.032) exhibited ADA elimination, regain of therapeutic trough levels, and clinical remission. Regain of clinical remission alone was achieved in 17/20 (85%) patients receiving comedication and 2/13 (15%) patients receiving anti-TNF dose intensification (P = 1.6 × 10−4).ConclusionImmunogenic LOR to infliximab or adalimumab in IBD can be successfully reversed using immunomodulator comedication.

A Novel Neutralization Antibody Assay Method to Overcome Drug Interference with Better Compatibility with Acid-Sensitive Neutralizing Antibodies

Immunogenicity testing to detect and characterize anti-drug antibody (ADA) is required for almost all biotherapeutics. Monoclonal antibody biotherapeutics usually have long half-lives and for high-dose indications such as oncology, high level of drug will be present in the testing samples and interfere with ADA and/or neutralization antibody (NAb) measurement. To overcome this drug interference, acid-dissociation-based sample pre-treatment such as Bead-Extraction and Acid Dissociation (BEAD) has been successfully applied. The main concern for these acid-dissociation-based methods, however, is that harsh acid treatment could denature positive control Abs as well as NAb species in testing samples. In addition, high amount of biotinylated drug is needed in order to have effective competition with high level of drug in the samples, which in turn requires expensive magnetic beads. And the whole process of magnetic beads handling is tedious if doing manually and often causes trouble during assay transfer. Here, we describe a novel method which we named as Precipitation, Acid Dissociation and Biotin-drug as Assay Drug (PABAD). This novel method will need only one step of acid dissociation, with much milder and shorter acid treatment to maximally preserve NAb activity. In addition, only a fraction of biotinylated-drug is needed and there is no need to use additional streptavidin (SA)-plate or SA-magnetic beads for extraction. Compared to a BEAD-based assay, PABAD demonstrates significantly improved recovery of acid-sensitive NAb positive controls (PCs) and similar recovery of acid-resistant NAb PCs.

Ocrelizumab concentration and antidrug antibodies are associated with B-cell count in multiple sclerosis

BackgroundThe majority of patients with multiple sclerosis on ocrelizumab have B-cell depletion after standard interval dosing of 26 weeks. With B-cell-guided dosing patients receive their next dose when B-cell repopulation...

Assessment and impact of dose escalation on anti-drug antibodies in Fabry disease.

Enzyme replacement therapy (ERT) with recombinant α-galactosidase A (AGAL) can lead to the formation of neutralizing anti-drug antibodies (ADA), which significantly limit treatment efficacy in patients with Fabry disease (FD). The effects of dose escalation on ADA titer and plasma globotriaosylsphingosine (lyso-Gb3) level are unknown. We screened 250 FD patients (200 males, 50 females) under ERT for ADAs and assessed the impact of an approved dose escalation in affected patients, focusing on ADA titers and plasma lyso-Gb3. ADA-positive patients were identified by serum-mediated inhibition assays, followed by titration assays to determine the individual inhibitory capacities of ADAs against agalsidase-alfa and agalsidase-beta. 70 (35%) of the male patients were ADA-positive, with a mean inhibitory capacity of 83.5 ± 113.7mg AGAL. Although patients receiving agalsidase-beta showed higher inhibitory capacities (84.7 ± 34.7mg) than patients under agalsidase-alfa (60.3 ± 126.7mg, p<0.001), the "theoretical deficit" to the infused dose was lower in patients receiving agalsidase-beta. In seven patients receiving agalsidase-alfa (0.2 mg/kg) ADAs were saturable by switching patients to agalsidase-beta (1.0 mg/kg). The switch resulted in increasing ADA titers within the first months. In 2 out of 7 (28.6%) therapy switchers, dose escalation could lead to durable ADA saturation. Independent of an increase in ADA titers, lyso-Gb3 levels decrease and cardiac and renal parameters remained stable after dose escalation. Dose escalation results in a heterogeneous, unpredictable ADA response, with more than a quarter of all treatment switchers succeeding in ADA saturation. Longitudinal ADA measurements are required to assess the individual risk of affected patients.

Assessing Immunogenicity of Biologic Drugs in Inflammatory Joint Diseases: Progress Towards Personalized Medicine

Biologic drugs have greatly improved treatment outcomes of inflammatory joint diseases, but a substantial proportion of patients either do not respond to treatment or lose response over time. Drug immunogenicity, manifested as the formation of anti-drug antibodies (ADAb), constitute a significant clinical problem. Anti-drug antibodies influence the pharmacokinetics of the drug, are associated with reduced clinical efficacy, and an increased risk of adverse events such as infusion reactions. The prevalence of ADAb differs among drugs and diseases, and the detection of ADAb also depends on the assay format. Most data exist for the tumor necrosis factor-alpha inhibitors infliximab and adalimumab, with a frequency of ADAb that ranges from 10 to 60% across studies. Measurement of ADAb and serum drug concentrations, therapeutic drug monitoring, has been suggested as a strategy to optimize therapy with biologic drugs. Although the recent randomized clinical Norwegian Drug Monitoring (NOR-DRUM) trials show promise towards a personalized medicine prescribing approach by therapeutic drug monitoring, several challenges remain. A plethora of assay formats, with widely differing properties, is currently used for measuring ADAb. Comparing results between different assays and laboratories is difficult, which complicates the development of cut-offs necessary for guidelines and the implementation of ADAb measurements in clinical practice. With the possible exception of infliximab, limited data on clinical relevance and cost effectiveness exist to support therapeutic drug monitoring as a routine clinical strategy to monitor biologic drugs in inflammatory joint diseases. The aim of this review is to provide an overview of the characteristics and prevalence of ADAb, predisposing factors to ADAb formation, commonly used assessment methods, clinical consequences of ADAb, and the potential implications of ADAb assessments for everyday treatment of inflammatory joint diseases.

10 Oral - CBX-12-101: A first-in-human study of CBX-12, an alphalex peptide drug conjugate (PDC) in patients with advanced or metastatic solid tumors

10 Oral - CBX-12-101: A first-in-human study of CBX-12, an alphalex peptide drug conjugate (PDC) in patients with advanced or metastatic solid tumors

P31 Chicken or egg: Inflammatory bowel disease in ankylosing spondylitis

P31 Chicken or egg: Inflammatory bowel disease in ankylosing spondylitis

Long-Term Dose Optimization of Adalimumab via Dose Spacing in Patients with Psoriasis.

Dose spacing (DS) can be useful for optimizing treatment with biologics in psoriasis patients. However, interval prolongation might increase the production of anti-drug antibodies (ADA) and, therefore, reduce the drug’s effectiveness. The long-term effects of DS with adalimumab in psoriatic patients have not been reported. The goal of our study was to evaluate the long-term follow-up of psoriatic patients after adalimumab DS regarding the clinical course and determination of circulating adalimumab, TNFα levels, and anti-adalimumab antibodies. We retrospectively included seven patients treated with adalimumab for moderate-to-severe psoriasis and benefiting from DS from 2010 to 2021. The dose interval of adalimumab was extended to three weeks for all patients and then to four weeks for three of the seven patients. Adalimumab trough levels, TNFα levels, and ADA against adalimumab were measured. For six of the seven patients, absolute PASI values remained below 3 throughout the follow-up period (median = 8.0 years; range: 1.7–11.5) after DS. All the patients were satisfied with the effectiveness of their treatment regime. Within the follow-up period, an average of 63 doses of adalimumab per patient were spared. The median adalimumab trough levels were 4.7 µg/mL (range: 1.9–12.5). TNFα levels remained under 10 pg/mL (undetectable) in all except one patient. ADA against adalimumab remained negative (<10 µg/mL) during the follow-up in all patients. Our data indicate that therapeutic drug monitoring, including the measurement of trough concentrations and ADA, together with the clinical response and patient’s preference, can be helpful for clinical decision making and treatment optimization in psoriasis.

Assessing aCCess to Investigations in Inflammatory Bowel Disease (ACCID): results from an international survey.

Multiple investigations are available to aid the diagnosis and monitoring of disease activity in inflammatory bowel disease (IBD). Fecal calprotectin (FC) is an established surrogate for intestinal inflammatory activity. Therapeutic drug monitoring (TDM) including thiopurine metabolites, anti-tumor necrosis factor (TNF) levels and antidrug antibody measurements are a step toward personalized medicine in IBD, but face access barriers. We aimed to assess test availability and barriers for these investigations in European practice. Five-hundred questionnaires were distributed to workshop participants at the 11th Congress of the European Crohn's and Colitis Organisation (ECCO). Access to FC, TDM for thiopurines and anti-tumor necrosis factor agents, as well as factors associated with usage and barriers to access were recorded. Responses were obtained from 195 attendees from 38 countries across a range of practices, healthcare settings and levels of experience. FC was available to 92.3% while access to anti-TNF (78.9%, P = 0.02 vs. thiopurine TDM, P = 0.0002 vs. FC) and thiopurine TDM (67.7%, P = 0.0001) were less widespread. Cost was a frequently cited barrier to test access or usage, with access having a significant West-East and North-South divide across all three investigations. The strongest independent predictor of access to all tests was healthcare spending per capita (P = 0.005 for FC; P < 0.0001 for both TDM). FC, anti-TNF and thiopurine TDM are increasingly incorporated as part of routine practice in IBD care across Europe and have the potential to impact positively on patient care. However, access barriers remain of which we found test cost the most significant with the investment required to reduce these barriers.

Mechanisms of Neutralizing Anti-drug Antibody Formation and Clinical Relevance on Therapeutic Efficacy of Enzyme Replacement Therapies in Fabry Disease.

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by mutations in the α-galactosidase A (AGAL/GLA) gene. The lysosomal accumulation of the substrates globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3) results in progressive renal failure, cardiomyopathy associated with cardiac arrhythmia, and recurrent strokes, significantly limiting life expectancy in affected patients. Current treatment options for FD include recombinant enzyme-replacement therapies (ERTs) with intravenous agalsidase-α (0.2 mg/kg body weight) or agalsidase-β (1 mg/kg body weight) every 2 weeks, facilitating cellular Gb3 clearance and an overall improvement of disease burden. However, ERT can lead to infusion-associated reactions, as well as the formation of neutralizing anti-drug antibodies (ADAs) in ERT-treated males, leading to an attenuation of therapy efficacy and thus disease progression. In this narrative review, we provide a brief overview of the clinical picture of FD and diagnostic confirmation. The focus is on the biochemical and clinical significance of neutralizing ADAs as a humoral response to ERT. In addition, we provide an overview of different methods for ADA measurement and characterization, as well as potential therapeutic approaches to prevent or eliminate ADAs in affected patients, which is representative for other ERT-treated lysosomal storage diseases.

P092 Development and evaluation of i-Tracker Ustekinumab and i-Tracker Anti-ustekinumab kits: fast and innovative chemiluminescent assays for the monitoring of patients treated with ustekinumab

Abstract Background Ustekinumab, a monoclonal antibody directed against IL12/23, is a drug widely used for the treatment of Chronic Inflammatory Diseases (Psoriasis, Crohn’s disease, etc.). Therapeutic Drug Monitoring is currently proposed to provide useful information to clinicians to improve the efficacy of the treatment. Theradiag has just developed the innovative i-Tracker ustekinumab and i-Tracker Anti-ustekinumab kits: fast quantification of ustekinumab and Anti-ustekinumab antibodies fully automated on the random access i-Track10 chemiluminescent analyzer. Methods Analytical performances were assessed using 2 types of serum samples: human serum spiked with ustekinumab or Anti-ustekinumab antibodies, and samples from Inflammatory Bowel Diseases patients treated with ustekinumab (n=32). For drug measurement, ustekinumab from serum sample was captured by anti-idiotypic antibody coupled magnetic microparticles and anti-ustekinumab polyclonal antibodies conjugated to acridinium ester were used for the detection of ustekinumab. For anti-drug antibodies measurement, Anti-ustekinumab antibodies were captured according to Ustekinumab coupled magnetic microparticles and detected with the use of ustekinumab conjugated to acridinium ester. Light emission was linked to the quantity of ustekinumab, or anti-ustekinumab antibodies presents in the sample. Results Ustekinumab measurement showed high accuracy (recovery was comprised between 98% and 120%). High precision weas reached for both assays (intra-precision CV were below 9.1% and 5.3% for ustekinumab and Anti-ustekinumab assays; inter-precision CV were below 4.6% and 10.6% for ustekinumab and Anti-ustekinumab assays) and no interference was seen with biologic agents (bilirubin, hemoglobin, lipids, biotin and rheumatoid factors). The dynamic ranges of the assays were 100ng/ml to 10 000ng/ml for ustekinumab quantification and 1 AU/ml to 250 AU/ml for anti-ustekinumab antibodies quantification. i-Tracker ustekinumab and i-Tracker anti-ustekinumab assays were compared to respective ELISA based LISA-TRACKER assays and showed excellent correlation (R² = 0.96, Slope = 0.93 for ustekinumab assay; Spearman’s coefficient correlation was 0.95 for Anti-ustekinumab assay). Conclusion i-Tracker kits are innovative assays which exhibit fast (time to results &amp;lt; 40min), accurate and reproducible results for the quantification of ustekinumab and Anti-ustekinumab antibodies. Excellent agreements were observed with respective LISA-TRACKER assays. i-Tracker kits are valuable tools for the monitoring of patients treated with ustekinumab.