Presence Of Anti-drug Antibodies Research Articles

Complex immunogenicity assessment in caplacizumab-treated patients with immune-mediated thrombotic thrombocytopenic purpura who have received plasma exchange

BackgroundISTH guidelines for immune-mediated thrombotic thrombocytopenic purpura (iTTP) treatment recommend concurrent therapeutic plasma exchange (TPE), immunosuppressive therapy (IST), and caplacizumab. TPE can complicate anti-drug antibody (ADA) measurements by transferring pre-existing antibodies (pre-Abs) into patients via donor plasma and/or diluting treatment-emergent (TE) ADAs. ObjectivesTo assess the presence of ADAs in patients with iTTP who received caplacizumab. MethodsImmunogenicity data from patients with iTTP receiving caplacizumab once daily plus TPE/IST in four clinical trials (TITAN, HERCULES, Post-HERCULES, and a trial conducted in Japanese patients) in the clinical development program were analyzed. ADA and modified ADA (mADA) assays differentiated pre-Abs from TE ADAs. A functional neutralizing antibody (NAb) assay and neutralizing epitope characterization assay (NECA) assessed the presence of ADAs with neutralizing potential. The impact of ADAs on efficacy, pharmacokinetics/pharmacodynamics, and safety was evaluated. ResultsAmong 228 patients in four studies, prevalence of pre-Abs ranged from 17.1% (TITAN) to 56.7% (HERCULES), while TE ADA prevalence ranged from 3.1% (HERCULES) to 14.3% (Japanese study). The TE NAb-positive rate ranged from 0% (Japanese study) to 12% (Post-HERCULES) using the functional NAb assay and from 2.7% (Post-Hercules) to 14.3% (Japanese study) using NECA. The presence of these antibodies did not impact treatment efficacy or safety. ConclusionsA complex immunogenicity assay strategy was required to define the pre-Ab/TE ADA status of patients with iTTP treated with caplacizumab in a clinical trial setting. In addition to the wide range of pre-Abs observed, few patients had detectable TE ADAs or NAbs, neither of which impacted on efficacy/safety.

Factors Associated with the Development of Anti-drug Antibodies to TNFi and the Consequences for Axial Spondyloarthritis: A Two-year Follow-up Study.

To evaluate the development of anti-drug antibodies (ADAb) against tumor necrosis factor inhibitors (TNFi) therapy during a 2-year period and search the factors linked to patients with axial spondyloarthritis (axSpA). Biologic-naive patients with axSpA were included in this observational study. Serum drug levels and ADAb were measured at weeks 12, 24, 52, and 104 of treatment by enzyme-linked immunosorbent assay (ELISA). The development of ADAb and factors related to ADAb over time were investigated using generalized estimating equations (GEE). A total of 180 patients with axSpA (116 male, mean (±SD) 45.6 (±11.9) years) who started TNFi treatment (etanercept (32.2%), adalimumab (27.2%), golimumab (20.6%), infliximab (20%)) were included. In the etanercept treatment group, only 1 patient had ADAb at 12 weeks and 24 weeks. Anti-drug antibodies against TNFi drugs were present in the adalimumab group in 32.7% of patients and in the infliximab group in 21.2% of patients at 12 weeks, and the proportion of ADAb-positive patients were found to be stable throughout the follow-up for adalimumab- and infliximab-treated patients. In the golimumab group, one patient had ADAb against golimumab at 12 weeks and the proportion of ADAb-positive patients increased throughout follow-up. In longitudinal analysis, baseline age, TNFi type, longitudinal Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and ASDAS-CRP scores, serum C-eeactive protein (CRP) levels, presence of adverse events and treatment discontinuation were associated with the presence of ADAb. The development of ADAb against TNFi therapy is associated with younger age, high disease activity, the development of adverse events and more common treatment discontinuation in patients with axSpA during 2-year follow-up.

Exploring TNFi drug-levels and anti-drug antibodies during tapering among patients with inflammatory arthritis: secondary analyses from the randomised BIODOPT trial

To evaluate tumour necrosis factor inhibitor (TNFi) drug-levels and presence of anti-drug antibodies (ADAb) in patients with inflammatory arthritis who taper TNFi compared to TNFi continuation. Patients with rheumatoid arthritis, psoriatic arthritis, or axial spondyloarthritis on stable TNFi dose and in low disease activity ≥ 12 months were randomised (2:1) to disease activity-guided tapering or control. Blood samples at baseline, 12- and 18-months were evaluated for TNFi drug-levels and ADAb. In total, 129 patients were randomised to tapering (n = 88) or control (n = 41). Between baseline and month 18, a significant shift in TNFi drug-levels were observed in the tapering group resulting in fewer patients with high drug-levels (change: − 14% [95% CI − 27 to − 1%]) and more with low drug-levels (change: 18% [95% CI 5–31%]). Disease activity was equivalent between groups at 18 months, mean difference: RA − 0.06 (95% CI − 0.44 to 0.33), PsA 0.03 (95% CI − 0.36 to 0.42), and axSpA 0.16 (− 0.17 to 0.49), equivalence margins ± 0.5 disease activity points. ADAb were detected in eight patients, all from the tapering group. TNFi drug-level category or ADAb were not predictive for achieving successful tapering at 18 months. TNFi drug-levels decreased during tapering which indicate adherence to the tapering algorithm. Despite the difference in TNFi drug-levels at 18 months, disease activity remained equivalent, and only few tapering patients had detectable ADAb. These data do not support using TNFi drug-level and/or ADAb to guide the tapering decision but future research with larger trials is needed.Trial registration: EudraCT: 2017-001970-41, December 21, 2017.

Immune-Mediated Liver Effects Associated With Administration of a Human Anti-IL-21 Receptor Antibody (ATR-107) in Rats.

The toxicity of ATR-107, a human anti-interleukin-21 receptor (IL-21R) monoclonal antibody (mAb), was evaluated in CD-1 mice and cynomolgus monkeys after single-dose intravenous (IV) administration, and in Sprague-Dawley (SD) rats and cynomolgus monkeys after weekly IV and subcutaneous (SC) administration in 13-week toxicity studies that included recovery. Adverse liver necrosis, diffuse bridging fibrosis, and higher liver enzymes occurred in rats in the low-dose IV group (10 mg/kg), but not at 50 or 250 mg/kg IV, and not following SC administration despite overlapping systemic ATR-107 exposures. Similar findings were not seen in mice or cynomolgus monkeys. A series of investigative rat toxicity studies showed liver findings only occurred after administration of at least 3 weekly doses, only occurred in rats that developed anti-drug antibodies (ADAs), and the incidence was associated with higher ADAs titers. However, the presence of ADAs did not always result in liver injury. Liver findings did not occur in nude rats, which had high ATR-107 exposures and no ADAs. These findings suggest an adaptive immune response with formation of ADAs was necessary for development of ATR-107-related liver findings, and that liver injury can occur in rats secondary to development of ADAs following repeated administration of a human therapeutic mAb.

Mass cytometry reveals atypical immune profile notably impaired maturation of memory CD4 T with Gb3-related CD27 expression in CD4 T cells in Fabry disease.

Fabry disease (FD) is an X-linked disease characterized by an accumulation of glycosphingolipids, notably of globotriaosylceramide (Gb3) and globotriaosylsphingosine (lysoGb3) leading to renal failure, cardiomyopathy, and cerebral strokes. Inflammatory processes are involved in the pathophysiology. We investigated the immunological phenotype of peripheral blood mononuclear cells in Fabry patients depending on the clinical phenotype, treatment, Gb3, and lysoGb3 levels and the presence of anti-drug antibodies (ADA). Leucocytes from 41 male patients and 20 controls were analyzed with mass cytometry using both unsupervised and supervised algorithms. FD patients had an increased expression of CD27 and CD28 in memory CD45- and CD45 + CCR7-CD4 T cells (respectively p < 0.014 and p < 0.02). Percentage of CD45RA-CCR7-CD27 + CD28+ cells in CD4 T cells was correlated with plasma lysoGb3 (r = 0.60; p = 0.0036) and phenotype (p < 0.003). The correlation between Gb3 and CD27 in CD4 T cells almost reached significance (r = 0.33; p = 0.058). There was no immune profile associated with the presence of ADA. Treatment with agalsidase beta was associated with an increased proportion of Natural Killer cells. These findings provide valuable insights for understanding FD, linking Gb3 accumulation to inflammation, and proposing new prognostic biomarkers.

Abstract 7164: Exposure-efficacy and exposure-safety relationships of tarlatamab to inform dose selection and benefit-risk assessment in patients with advanced small cell lung cancer (SCLC)

Abstract Introduction: Tarlatamab is a first in class, half-life extended bispecific T-cell engager (BiTE) immunotherapy targeting delta-like ligand 3 (DLL3) that has shown promising anti-tumor activity and survival outcomes with manageable safety profile in clinical studies of patients with previously treated SCLC (NCT03319940, NCT05060016) (Ahn et al, 2023; Paz-Ares et al, 2023). Here we characterized the exposure-efficacy and exposure-safety profiles associated with tarlatamab treatment in SCLC, including the effects of patient-specific covariates (brain or liver metastasis, smoking status, number of prior lines of therapy, prior PD-1/PD-L1 inhibitor therapy, sum of target lesion diameters, and presence of anti-drug antibody). Methods: The analysis dataset consisted of 412 subjects with SCLC from ongoing Phase 1 DeLLphi-300 study (dose range 0.003 mg to 100 mg Q2W and 200 mg Q3W) and Phase 2 DeLLphi-301 study (10 mg and 100 mg Q2W). Serum tarlatamab exposure averaged over the first cycle (28 days) was utilized as the predictor of response in the regression analysis. Efficacy endpoints included objective response rate, disease control rate, best tumor size response, progression-free survival and overall survival (OS). Safety endpoints included overall treatment related adverse event (TRAE), overall treatment emergent adverse event (TEAE), and TEAEs of cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS) and associated neurologic events, and neutropenia. Only the grade ≥ 3 adverse events (AEs) were evaluated. Results: Significant exposure-response relationships were established for all key efficacy measures across the dose range investigated. Plateau in the exposure-efficacy relationship (maximal efficacy) was observed at the recommended dose of 10 mg Q2W. Exposures associated with lower doses were estimated to have lower efficacy. No clear trends for exposure-response relationships were identified for the evaluated AEs except for grade ≥ 3 neutropenia, where a shallow trend was observed for increased neutropenia rate with increasing tarlatamab exposures. Of all the evaluated covariate relationships, only higher baseline sum of target lesion diameters was statistically significantly correlated with worsening of OS. Conclusions: Overall results in this SCLC population suggest tarlatamab exposures associated with the recommended dose of 10 mg Q2W exhibited near maximal efficacy and a favorable benefit-risk profile. None of the evaluated patient-specific covariates resulted in clinically meaningful changes in efficacy or safety, and therefore do not warrant a dose adjustment. Citation Format: Po-Wei Chen, Mukul Minocha, Stephanie M. Kong, Erik S. Anderson, Amanda Parkes, Pablo Martinez, Brett E. Houk, Chih-Wei Lin. Exposure-efficacy and exposure-safety relationships of tarlatamab to inform dose selection and benefit-risk assessment in patients with advanced small cell lung cancer (SCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7164.

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.

P468 Relevance of anti-drug antibodies in context of supra-therapeutic anti-TNF concentrations

Abstract Background The low serum concentration of anti-tumor necrosis factor-alpha (anti-TNFα) agents and the presence of anti-drug antibodies are related to poor therapeutic outcomes in inflammatory bowel disease (IBD). We aimed to evaluate the prognosis of patients having both antidrug antibodies and supratherapeutic drug concentrations. Methods IBD patients on maintenance infliximab (IFX) or adalimumab (ADA) therapy were prospectively recruited. Serum drug concentrations and antidrug antibodies were measured (Anser, Prometheus). The drug concentrations were classified as subtherapeutic (IFX: &amp;lt;3 µg/mL; ADA: &amp;lt;5 µg/mL), therapeutic (IFX: 3-8 µg/mL; ADA 5-10 µg/mL), and supratherapeutic (IFX &amp;gt; 8 µg/mL; ADA &amp;gt; 10 µg/mL) concentrations regardless of the timing of blood sample collection. We analysed the relationship between i) drug concentrations and ii) the presence and absence of anti-drug antibodies with use of systemic corticosteroids and anti-TNF discontinuation. Results Of 172 patients (122 CD [70.9%], 44 UC [25.6%], 3 IBD-U [1.7%], and 3 IBD-pouch [1.7%]), the median age was 32.3 years (range, 24.8-42.5), and the median duration of IBD was 9.7 years (range 5.3-15.6). IFX and ADA were used in 81 (47.1%) and 91 (52.9%) patients, respectively, and concurrent usage of immunomodulators and systemic corticosteroids was observed in 39 (22.7%) and 23 (13.4%) patients, respectively. Supratherapeutic, therapeutic, and subtherapeutic concentrations were observed in 74 (43.0%), 32 (18.6%), and 66 (38.4%), respectively. The patients with antidrug antibodies (n = 79, 45.9%) showed a higher frequency of having subtherapeutic drug concentrations (68.4% vs 12.9%, P &amp;lt; 0.001) compared to those without antibodies, and the presence of antibodies was an independent predictor of discontinuation of anti-TNFα agents (hazard ratio 3.50, 95% confidence interval 1.88-6.51, P &amp;lt; 0.001, Fig. 1A). In subgroup analysis, patients with antidrug antibodies and supratherapeutic drug concentration exhibited a tendency to have improved drug persistence compared to those with subtherapeutic drug concentration, albeit insignificantly (P = 0.099, Fig. 1B). However, the persistence in this group was still poorer than that observed in patients without antibodies (P = 0.003). Finally, neither anti-TNFα concentrations nor the presence of antidrug antibodies were associated with the need for additional systemic corticosteroid use within 6 months. Conclusion The presence of antidrug antibodies can predict the discontinuation of anti-TNFα agents despite supratherapeutic drug levels. While supratherapeutic drug concentration may improve the treatment persistence of anti-TNFα agents in patients with anti-drug antibodies, it does not last as long as in those without antibodies.

Development and Validation of an ADA-Tolerant Assay for Quantification of an Exatecan-Based ADC in Monkey Plasma.

The development of an anti-drug antibody (ADA)-tolerant pharmacokinetic (PK) assay is important when the drug exposure is irrelevant to toxicity in the presence of ADA. We aimed to develop and validate an ADA-tolerant assay for an exatecan-based antibody-drug conjugate (ADC) in monkey plasma. The assay tolerated 5.00 µg/mL of ADA at 12 µg/mL of ADC. Its accuracy and precision results satisfied the acceptance criteria. Furthermore, the assay was free from hook and matrix effects and exhibited good dilutional linearity. Additionally, the ADC in plasma samples was stable under different storage conditions. An ADA-tolerant ADC assay was configured with an anti-payload antibody for capture, and a drug-target protein combined with a horseradish peroxidase (HRP)-labeled antibody against a drug-target-protein tag for detection. Samples were firstly acidified to dissociate drug and ADA complexes, and to convert the carboxylate form to the lactone form of exatecan molecules; then, the ADAs in the samples were removed with a naked antibody-coated microplate. The treated samples were further incubated with coated anti-payload antibody and captured ADC molecules were quantified by the detection reagent. The developed assay was optimized and validated against regulatory guidelines. The assay met both methodological and sample-related ADA tolerance requirements, and was applicable to a nonclinical study in cynomolgus monkeys.

P897 The association of HLA-DQA1*05 carriage with immunogenicity to anti-tumour necrosis factor therapy and drug persistence in Asian patients with inflammatory bowel disease

Abstract Background HLA-DQA1*05 carriage increases anti-tumour necrosis factor (TNF) immunogenicity and lowers drug persistence in European inflammatory bowel disease (IBD) patients. There is a paucity of data for Asian patients. We hypothesize that the HLA-DQA1*05 allele is present in our local IBD population and may be associated with similar clinical and pharmacokinetic outcomes as European cohorts. Methods A single-centre retrospective study of consecutive IBD patients on Infliximab (IFX) or Adalimumab (ADM) was performed. HLA-DQA1*05 carriage was tested with Sanger sequencing. Serum anti-drug antibody (ADA) levels were analysed at each IFX infusion and per physician discretion for ADM. Concomitant immunomodulator (IM) therapy with Azathioprine or Methotrexate was recorded. Primary outcome was immunogenicity to IFX or ADM, defined as ADA concentration ≥10 AU/ml at any time point. Secondary outcomes were loss of response (LOR), defined as IBD symptom-related treatment intensification, and persistence, defined as anti-TNF continuation at end of follow-up. The effects of HLA-DQA1*05 carriage on outcomes and predictors of persistence were analysed. Results 39 patients (28 Crohn’s disease, 11 ulcerative colitis) were included (mean age 39 years, median disease duration 10 years). 24 patients had IFX as first anti-TNF agent (21 with IM, 3 as monotherapy), 7 of whom had second-line ADM with IM. 15 patients had ADM as first anti-TNF agent (13 with IM, 2 as monotherapy), 2 of whom had second-line IFX (1 with IM). 15/39 (38.5%) patients were positive for HLA-DQA1*05. 42/48 (87.5%) of anti-TNF exposures were on IM. In HLA-DQA1*05 carriers compared to non-carriers, development of ADA (61.1% vs 47.8%, p=0.397) and LOR (42.1% vs 31.0%, p=0.433) was numerically higher but not statistically different. Persistence of first anti-TNF agent was similar between carriers and non-carriers at the end of follow-up (median 28.0 months vs 21.5 months, p=0.364) (Figure 1). ADA development was not associated with LOR (p=0.07) or persistence (p=0.29). 19/48 (39.6%) of anti-TNF exposures discontinued treatment at the end of follow-up, 13 of whom experienced LOR. 10/13 (76.9%) of patients with LOR were female. Female sex was significantly associated with anti-TNF non-persistence on univariable (OR 4.82, 95% CI 1.38-16.75, p=0.01) and multivariable logistic regression (OR 7.24, 95% CI 1.35-38.90, p=0.02), after adjusting for HLADQA1*05 carriage, presence of ADA and anti-TNF order (first versus second-line) (Table 1). Conclusion In Asian IBD patients, HLA-DQA1*05 carriage may not affect immunogenicity nor treatment persistence, especially with proactive therapeutic drug monitoring and concurrent IM. Female sex negatively affects persistence. Larger prospective studies are needed.

Infliximab monitoring in Crohn’s disease: a neural network approach for evaluating disease activity and immunogenicity

Background: The treatment for Crohn’s disease (CD) has increasingly required the use of biological agents. Safe and affordable tests have led to the active implementation of therapeutic drug monitoring (TDM) in clinical practice, which, although not yet widely available across all health services, has been proven effective. Objective: To analyze serum infliximab (IFX) and antidrug antibody (ADA) levels in CD patients, compare two tests, as well as construct a prediction of neural network using a combination of clinical, epidemiological, and laboratory variables. Design: Cross-sectional observational study. Method: A cross-sectional observational study was conducted on 75 CD patients in the maintenance phase of IFX treatment. The participants were allocated into two groups: CD in activity (CDA) and in remission (CDR). Disease activity was defined by endoscopic or radiological criteria. Serum IFX levels were measured by enzyme-linked immunosorbent assay (ELISA) and rapid lateral flow assay; ADA levels were measured by ELISA. A nonparametric test was used for statistical analysis; p value of ⩽0.05 was considered significant. Differences between ELISA and rapid lateral flow results within the measurement range were assessed by the Wilcoxon test, Passing–Bablok regression, and Bland–Altman method. Prediction models were created using four neural network sets. Neural networks and performance receiver operating characteristic curves were created using the Keras package in Python software. Results: Most participants exhibited supratherapeutic IFX levels (&gt;7 mg/mL). Both tests showed no difference in IFX levels between the CDA and CDR groups ( p &gt; 0.05). The use of immunosuppressive therapy did not affect IFX levels ( p &gt; 0.05). Only 14.66% of patients had ADA levels &gt;5 AU/mL, and all ADA-positive participants exhibited subtherapeutic IFX levels in both tests. The median results of both tests showed significant differences and moderate agreement ( r = −0.6758, p &lt; 0.001). Of the four neural networks developed, two showed excellent performance, with area under the curve (AUCs) of 82–92% and 100%. Conclusion: Most participants exhibited supratherapeutic IFX levels, with no significant serum level difference between the groups. There was moderate agreement between tests. Two neural network sets showed disease activity and the presence of ADA, noninvasively determined in patients using IFX by presenting an AUC of &gt;80%.

Quantifying the Effect of Methotrexate on Adalimumab Response in Psoriasis by Pharmacokinetic–Pharmacodynamic Modeling

Previously, we showed that the combination of methotrexate and adalimumab treatment leads to less antidrug antibody development. In this study, we quantify the pharmacokinetics/pharmacodynamics (PK/PD) of adalimumab and evaluate the influence of methotrexate cotreatment. A population PK-PD model was developed using prospective data from 59 patients with psoriasis (baseline PASI= 12.6) receiving adalimumab over 49 weeks. Typical PK and PD parameters and their corresponding interpatient variability were estimated. We performed a covariate analysis to assess whether interpatient variability could be explained by addition of methotrexate and other covariates. In total, 330 PASIs, 252 adalimumab serum concentrations, and 247 antidrug antibody titers were available. Presence of antidrug antibodies (adalimumab group= 46.7%, adalimumab+ methotrexate group= 38.7%; P= .031) was correlated with increased adalimumab apparent clearance (P < .001). In the PD model, the use of concomitant methotrexate was borderline to significantly correlated with a decreased half-maximal inhibitory concentration (adalimumab concentration for which clinical response score is reduced by half; P < .10). On the basis of our PK-PD model, concomitant use of methotrexate indirectly increases adalimumab concentration, partially through less antidrug antibodies formation, which may result in better 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.

Abstract 6330: Countering antidrug antibodies to programmed cell death-1 blockade in mouse Pten-null prostate cancer

Abstract Therapeutic biologics have the potential to elicit immune responses that results in the development anti-drug antibodies (ADAs). ADAs that develop after immune checkpoint blockade (ICB) limit their therapeutic efficacy and increase the risk of adverse events. Mitigating ADAs would improve the efficacy of antibody-based therapeutics and identifying reliable biomarkers would allow for rational, evidence-based criteria for tailoring treatments. However, detecting ADAs is challenging and data regarding their biology and means to counter this phenomenon are limited. Here, we examined the development of ADAs to anti-programmed cell death-1 (PD-L1) monoclonal antibodies in a mouse model Pten/Trp53-null (DKO) prostate cancer and countered their negative effect with systemic administration of a JAK1/2 inhibitor. Like human prostate cancer, adding PD-L1 ICB to androgen deprivation therapy has failed to produce a therapeutic effect in DKO cancer model. Our analysis showed that tumor-bearing DKO mice have increased levels of peripheral dendritic cells (pDC) of which &amp;gt;80% exhibited high levels of PD-L1. Given this finding, we developed a system to monitor the development of ADAs against two murine anti-PD-L1 (aPD-L1) monoclonal antibodies clone 80 and 10F9.G2. Pharmacodynamic studies showed that a single-dose administration of the blocking antibodies effectively neutralized PD-L1 in pDC that lasted for four days. Chronic (twice/week) dosing of the aPD-L1 antibodies strongly neutralized PD-L1 in pDCs, but the efficacy waned after 22 days. Using crossover approach, consisting of clone 10F9.G2 dosing for two weeks followed by clone 80, extended PD-L1 blockade in pDCs to 36 days, but did not improve antitumor activity. Blocking STAT3 signaling with the JAK1/2 inhibitor AZD1480 restored PD-L1 blockade in pDCs and was associated with improved reduction of tumor burden. Further analysis showed improved neutralization of PD-L1 in cancer cells and tumor infiltrating immune cells in mice treated with AZD1480. These effects were associated with greater T and NK cell reactivity in tumors. Our study shows that the presence of ADAs is associated with lack of antitumor responses to ant-PD-L1 blockade in a preclinical model of prostate cancer and provides additional data that will improve our understanding of ADAs against immune checkpoint inhibitors. This study also offers an approach to monitor ADA development and a platform to investigate novel approaches to target ADAs. Citation Format: Marco A. De Velasco, Yurie Kura, Noriko Sako, Naomi Ando, Kazutoshi Fujita, Mitsuhisa Nishimoto, Kazuko Sakai, Kazuhiro Yoshimura, Masahiro Nozawa, Scott A. Hammond, Simon J. Dovedi, Barry R. Davies, Kazuto Nishio, Hirotsugu Uemura. Countering antidrug antibodies to programmed cell death-1 blockade in mouse Pten-null prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6330.

Effectiveness of golimumab intensification in ulcerative colitis: A multicentric prospective study.

Loss of response to golimumab occurs in nearly 40% of patients with ulcerative colitis (UC). Unlike others anti-TNF, no study has reported a correlation between serum golimumab level and response to drug intensification. The objective of this study was to evaluate the effectiveness and safety of golimumab intensification and to identify the best threshold of serum golimumab before drug intensification predictive of response. We included all consecutive patients with active UC with loss of response to golimumab in a prospective multicentric cohort study. Patients with loss of response at 50 mg q4 weeks (W) and 100 mg q4W underwent therapeutic intensification at 100 mg q4W and 100 mg q2W, respectively. Effectiveness and safety were assessed between Weeks 2 and 4 (visit 2) and between Weeks 4 and 8 (visit 3) after intensification. Serum level and anti-golimumab antibodies were evaluated at each medical visit (Lisa Tracker, Theradiag France). A total of 47 UC patients (Female, 50%; median age, 39 years (IQR, 27-52)) treated with golimumab for a median of 20.4 weeks (IQR, 10.7-38.3) were included. The median partial Mayo score was 6 (IQR, 5-7), and the median endoscopic Mayo score was 3 (IQR, 2-3). The median golimumab serum level before intensification was 2.23 μg/mL (IQR, 1.02-3.96) and only one patient (2.1%) had anti-drug antibodies. At Visit 2 (Week 2-4), 40% patients experienced clinical response, 10% clinical remission, 33% endoscopic response and 23% endoscopic remission. At Visit 3 (Week 4-8), 44% of patients had clinical response, 22% of patients had clinical remission, 45% of patients had endoscopic response, and 41% of patients had endoscopic remission. The median golimumab levels before intensification do not differ between responders and non-responders (2.13μg/ml (0.76-2.76) and 3.37μg/ml (IQR, 1.08-4.67), respectively; p= 0.14) assessed at Visit 3. Golimumab intensification to 100 mg q4W (vs q2W) (OR 1.98, 95% CI [1.06-3.70]; p= 0.032) was significantly associated with clinical remission at Visit 3. Serum drug level at baseline or the presence of antidrug antibodies were not associated with clinical or endoscopic remission/response. Two serious adverse events (one infection and one UC flare) were reported during the 24-week follow-up. In this prospective multicentric study, half of patients recaptured response following golimumab intensification in UC. Therapeutic drug monitoring did not predict response after optimisation of golimumab.

Presence and impact of antidrug antibodies (ADAs) to tremelimumab (T) or durvalumab (D) in the phase 3 HIMALAYA study of unresectable hepatocellular carcinoma (uHCC).

551 Background: ADAs to immune checkpoint inhibitors may decrease antitumor activity in HCC. Reported rates of treatment-emergent ADAs (TE-ADAs) vary from 1.5% for pembrolizumab and 8.6% for nivolumab to 54.1% for atezolizumab across indications (Enrico et al. Clin Cancer Res 2020). In the global, Phase 3 HIMALAYA study (NCT03298451) in uHCC, the STRIDE regimen (Single T Regular Interval D) significantly improved overall survival vs sorafenib (S); D monotherapy was noninferior to S (Abou-Alfa et al. NEJM Evid 2022). Here, we analyzed ADAs to T and D in HIMALAYA. Methods: Prespecified secondary analyses assessed the presence of ADAs to D and T before the first study dose (baseline), once during treatment and once after treatment discontinuation. For participants (pts) who were ADA-positive at any visit (ADA+), presence of neutralizing antibodies (nAbs) was also assessed. TE-ADA+ was defined as pts with a positive post-baseline sample only or pts with an ADA titer that increased ≥4-fold following treatment. ADA negative (ADA-) was defined as pts with no positive sample at any visit, at baseline or post-baseline. Objective response rate (ORR; RECIST v1.1, inc. unconfirmed), overall survival (OS) and treatment-related adverse events (TRAEs) were evaluated in ADA subgroups. Results: The frequency of ADAs to D was similar in the STRIDE (T+D) and D arms: 8.2% (24/294) and 7.1% (20/282) of pts, respectively, were ADA+ to D; 3.1% (9/294) and 2.8% (8/282) of pts, respectively, were TE-ADA+ to D; and 1.7% (5/294) and 0.7% (2/282) of pts, respectively, had nAbs to D. In the STRIDE arm, 15.9% (29/182) of pts were ADA+ to T, 11.0% (20/182) of pts were TE-ADA+ to T, and 4.4% (8/182) of pts had nAbs to T. Although the number of pts was small, in the STRIDE arm, ORR was 11.1% (1/9) in pts TE-ADA+ to D, 35.0% (7/20) in pts TE-ADA+ to T and 23.9% (94/393) in the full analysis set (FAS). In the D arm, ORR was 25.0% (2/8) in pts TE-ADA+ to D and 18.5% (72/389) in the FAS. OS for pts TE-ADA+/nAb+ to D or T in the D and STRIDE arms was consistent with the FAS. In both arms, TRAE and Grade 3/4 TRAE rates were not increased in the ADA+ vs ADA- groups (Table) and were generally consistent with the overall population. Conclusions: In HIMALAYA, the rates of TE-ADAs and nAbs to D and T were low (≤11%). The presence of ADAs did not appear to impact clinical efficacy or safety of STRIDE or D monotherapy in the small number of ADA+ pts. These results support a low risk of ADAs for STRIDE or D in uHCC. Clinical trial information: NCT03298451 . [Table: see text]

A root cause analysis to identify the mechanistic drivers of immunogenicity against the anti-VEGF biotherapeutic brolucizumab.

Immunogenicity against intravitreally administered brolucizumab has been previously described and associated with cases of severe intraocular inflammation, including retinal vasculitis/retinal vascular occlusion (RV/RO). The presence of antidrug antibodies (ADAs) in these patients led to the initial hypothesis that immune complexes could be key mediators. Although the formation of ADAs and immune complexes may be a prerequisite, other factors likely contribute to some patients having RV/RO, whereas the vast majority do not. To identify and characterize the mechanistic drivers underlying the immunogenicity of brolucizumab and the consequence of subsequent ADA-induced immune complex formation, a translational approach was performed to bridge physicochemical characterization, structural modeling, sequence analysis, immunological assays, and a quantitative systems pharmacology model that mimics physiological conditions within the eye. This approach revealed that multiple factors contributed to the increased immunogenic potential of brolucizumab, including a linear epitope shared with bacteria, non-natural surfaces due to the single-chain variable fragment format, and non-native drug species that may form over prolonged time in the eye. Consideration of intraocular drug pharmacology and disease state in a quantitative systems pharmacology model suggested that immune complexes could form at immunologically relevant concentrations modulated by dose intensity. Assays using circulating immune cells from treated patients or treatment-naïve healthy volunteers revealed the capacity of immune complexes to trigger cellular responses such as enhanced antigen presentation, platelet aggregation, endothelial cell activation, and cytokine release. Together, these studies informed a mechanistic understanding of the clinically observed immunogenicity of brolucizumab and associated cases of RV/RO.

P787 Subcutaneous infliximab in IBD patients with previous immunogenic failure of intravenous infliximab

Abstract Background The immunogenicity of infliximab (IFX) is a major reason for secondary loss of response to intravenous (IV) IFX treatment. A lower incidence of anti-drug antibodies (ADA) with subcutaneous (SC) IFX treatment compared to IFX IV has been described1,2. Furthermore, data on four patients with immunogenic failure or allergic reactions to IFX IV documented safety of exposure to IFX SC3. Here, we analyzed the efficacy and safety of IFX SC in IBD patients with previous immunogenic/allergic failure to IFX IV in a monocentric analysis conducted at the Dresden University Hospital. Methods Immunogenic failure was defined as presence of ADA and low/undetectable IFX trough levels during IFX IV therapy. Patients received IFX SC 120 mg every other week (EOW). HBI and partial Mayo, IFX trough levels, free ADA, and fecal calprotectin (FCP) were determined at wk 0 and wk 12. Clinical remission was defined as HBI&amp;lt;5 or partial Mayo≤1. FCP&amp;lt;250ug/g was considered biochemical remission. Results Ten patients (7/10 with active IBD and 3/10 in remission) were included. All patients had previously developed ADA during IFX IV treatment. Two patients had suffered an IFX infusion-related allergic reaction. Baseline demographic parameters are shown in table 1. Patients were extensively pretreated (5/10 had previous treatment with ≥3 biologics). 5/10 patients were switched from ongoing IV application to IFX SC, while 5/10 were started on IFX SC without IFX IV induction. During follow up, 6/10 patients did not reach IFX trough levels≥3ug/ml, of whom four patients showed detectable ADA. 2/10 patients developed mild injection site reactions. No severe immediate hypersensitivity reactions were observed. Treatment persistence across wk 12 was 70% (7/10), while 3/10 patients discontinued IFX SC due to lack of efficacy. In the active IBD group, clinical remission at wk 12 was achieved in 1/7 patients. 2/7 patients showed a decrease in FCP from baseline to wk 12. Among the three patients who entered the study in remission, all maintained clinical and biochemical remission until wk 12 (3/3). Conclusion In this cohort, exposure of patients with previous immunogenic/allergic failure of IFX IV was well tolerated and safe. However, only a minority of patients established significant IFX through levels with EOW IFX SC therapy and clinical responses were heterogeneous. Further studies are required to assess the safety and efficacy of IFX SC in patients with previous immunogenic IFX failure and to investigate the value of dose intensification and/or interval shortening of IFX SC in this patient population.

P607 HLA-DQA1*05 Allele Carriage and Anti-TNF Therapy Persistence in Inflammatory Bowel Disease

Abstract Background Carriage of HLA-DQA1*05 allele is associated with development of antidrug antibodies (ADA) in patients with Crohn’s Disease (CD) receiving anti-TNF therapy. The presence of ADA is not uniformly associated with anti-TNF therapy failure as patients with adequate trough drug concentrations, even where ADA are present, can maintain therapy response. We aimed to determine the impact of carriage of HLA-DQA1*05 allele on outcome of anti-TNF therapy evaluated by drug persistence in routine clinical practice. Methods A multi-centre retrospective study of IBD patients treated with anti-TNF therapy was performed. HLA-DQA1*05 genotypes were generated for each included patient by imputation from whole genome sequence using HIBAG. Only outcome of first anti-TNF therapy received by patients was evaluated in this study. Study primary endpoint was anti-TNF therapy persistence, expressed as time to discontinuation of anti-TNF therapy, segregated by HLA-DQA1*05 allele genotype. Patients discontinuing anti-TNF therapy due to primary or secondary loss of response or due to side-effects were considered therapy failures. Statistical analysis was performed using survival analysis and multivariate cox logistic regression with effect of covariates on outcome expressed as odds ratios (OR). Results 921 IBD patients were identified with 877 included in the study population. Baseline demographics for the entire cohort and segregated by HLA-DQA1*05 allele status are summarised in Figure 1. In the study population, 543 (62%) had no copy, 281 (32%) one copy and 53 (6%) two copies of HLA-DQA1*05 allele. Median time to anti-TNF therapy discontinuation in patients with 2 copies of HLA-DQA1*05 allele was significantly shorter compared to patients with 1 or no copy at 700-days follow-up: 418 versus 513 versus 541 days respectively, p=0.007 (Figure 2) with similar results observed at 2000-days follow-up (p=0.04). In a multivariate regression, factors independently associated with time to anti-TNF therapy discontinuation included: carriage of HLA-DQA1*05 allele OR 1.2, p=0.02; male gender OR 1.6, p=4.2 x 10-5; CD phenotype OR 0.7, p=0.009; and anti-TNF therapy type (infliximab) OR 1.5, p=0.002. Concomitant immunomodulator use was not associated with time to anti-TNF therapy discontinuation in this model, OR 0.97, p=0.84. Conclusion Carriage of two HLA-DQA1*05 alleles is associated with a less favorable outcome of anti-TNF therapy with shorter time to therapy discontinuation. Carriage of one HLA-DQA1*05 allele is not associated with outcome of anti-TNF therapy. Assessing HLA-DQA1*05 genotype has value in routine clinical practice as HLA-DQA1*05 homozygotes are at increased risk of anti-TNF failure which should be a consideration in IBD therapy selection.

Antidrug Antibodies to Tumor Necrosis Factor α Inhibitors in Patients With Noninfectious Uveitis

Tumor necrosis factor inhibitors (TNFis) can induce antidrug antibody (ADA) formation and loss of therapeutic response. However, the utility of ADA testing and the association between ADAs and treatment response in patients with noninfectious uveitis (NIU) is not well understood. To assess the frequency of ADAs and their association with drug levels and clinical response in patients with NIU treated with adalimumab or infliximab. This retrospective cross-sectional study included patients diagnosed with NIU who received adalimumab or infliximab and underwent testing for serum drug level and ADAs at the National Eye Institute from September 2017 to July 2021. Serum drug level testing with reflex testing for ADA levels was performed. The main outcome was the association between drug levels and ADAs, clinical response, and concurrent antimetabolite use in patients treated with TNFis for NIU. Of 54 patients included in the study, 42 received adalimumab (mean [SD] age, 43.6 [19.6] years; 25 [59.5%] female) and 12 received infliximab (mean [SD] age, 42.7 [20.4] years; 7 [58.3%] male). In the adalimumab group, mean (SD) drug level was 9.72 (6.82) μg/mL, mean (SD) ADA level was 84.2 (172.9) arbitrary units/mL, and ADA frequency was 35.7% (15 of 42 patients). Mean drug level was lower in those with ADAs compared with those without ADAs (mean [SD], 2.8 [2.6] μg/mL vs 13.6 [5.2] μg/mL; difference: 10.8 μg/mL; 95% CI, 8.3-13.2 μg/mL; P < .001). There was a higher mean drug level with concurrent antimetabolite use compared with monotherapy (mean [SD], 11.0 [7.3] μg/mL vs 6.8 [4.5] μg/mL; difference: -4.2 μg/mL; 95% CI, -8.7 to 0.2 μg/mL; P = .06). Multivariable modeling showed that a 1-arbitrary unit increase in ADAs was associated with a -0.02 μg/mL (95% CI, -0.01 to -0.34 μg/mL) difference in mean drug level (P < .001). Favorable clinical response was associated with a threshold drug level above 2.7 μg/mL or an antibody level below 15.2 μg/mL. The mean (SD) drug level in the infliximab group was 27.02 (18.15) μg/mL, and no ADAs were detected. In this study, 35.7% of adalimumab-treated patients with NIU had ADAs. The presence of ADAs was associated with lower drug levels, and higher ADA levels were associated with increased risk of TNFi treatment failure. Although limited by the retrospective design, our results suggest that therapeutic drug monitoring may be considered among patients experiencing therapy failure to help exclude ADAs as a potential cause of treatment failure.