Vascular inflammation, infusion reactions, glomerulopathies, and other potentially adverse effects may be observed in laboratory animals, including monkeys, on toxicity studies of therapeutic monoclonal antibodies and recombinant human protein drugs. Histopathologic and immunohistochemical (IHC) evaluation suggests these effects may be mediated by deposition of immune complexes (ICs) containing the drug, endogenous immunoglobulin, and/or complement components in the affected tissues. ICs may be observed in glomerulus, blood vessels, synovium, lung, liver, skin, eye, choroid plexus, or other tissues or bound to neutrophils, monocytes/macrophages, or platelets. IC deposition may activate complement, kinin, and/or coagulation/fibrinolytic pathways and result in a systemic proinflammatory response. IC clearance is biphasic in humans and monkeys (first from plasma to liver and/or spleen, second from liver or spleen). IC deposition/clearance is affected by IC composition, immunomodulation, and/or complement activation. Case studies are presented from toxicity study monkeys or rats and indicate IHC-IC deposition patterns similar to those predicted by experimental studies of IC-mediated reactions to heterologous protein administration to monkeys and other species. The IHC-staining patterns are consistent with findings associated with generalized and localized IC-associated pathology in humans. However, manifestations of immunogenicity in preclinical species are generally not considered predictive to humans.

ObjectiveTo investigate whether antidrug antibodies and/or drug non‐trough levels predict the long‐term treatment response in a large cohort of patients with rheumatoid arthritis (RA) treated with adalimumab or etanercept and to identify factors influencing antidrug antibody and drug levels to optimize future treatment decisions.MethodsA total of 331 patients from an observational prospective cohort were selected (160 patients treated with adalimumab and 171 treated with etanercept). Antidrug antibody levels were measured by radioimmunoassay, and drug levels were measured by enzyme‐linked immunosorbent assay in 835 serial serum samples obtained 3, 6, and 12 months after initiation of therapy. The association between antidrug antibodies and drug non‐trough levels and the treatment response (change in the Disease Activity Score in 28 joints) was evaluated.ResultsAmong patients who completed 12 months of followup, antidrug antibodies were detected in 24.8% of those receiving adalimumab (31 of 125) and in none of those receiving etanercept. At 3 months, antidrug antibody formation and low adalimumab levels were significant predictors of no response according to the European League Against Rheumatism (EULAR) criteria at 12 months (area under the receiver operating characteristic curve 0.71 [95% confidence interval (95% CI) 0.57, 0.85]). Antidrug antibody–positive patients received lower median dosages of methotrexate compared with antidrug antibody–negative patients (15 mg/week versus 20 mg/week; P = 0.01) and had a longer disease duration (14.0 versus 7.7 years; P = 0.03). The adalimumab level was the best predictor of change in the DAS28 at 12 months, after adjustment for confounders (regression coefficient 0.060 [95% CI 0.015, 0.10], P = 0.009). Etanercept levels were associated with the EULAR response at 12 months (regression coefficient 0.088 [95% CI 0.019, 0.16], P = 0.012); however, this difference was not significant after adjustment. A body mass index of ≥30 kg/m2 and poor adherence were associated with lower drug levels.ConclusionPharmacologic testing in anti–tumor necrosis factor–treated patients is clinically useful even in the absence of trough levels. At 3 months, antidrug antibodies and low adalimumab levels are significant predictors of no response according to the EULAR criteria at 12 months.

In preclinical toxicity studies, species-foreign proteins administered to animals frequently leads to formation of anti-drug antibodies (ADA). Such antibodies may form circulating immune complexes (CIC) with the administered protein. These CIC can activate the classical complement pathway, thereby forming complement-bound CIC (cCIC); if large of amounts of CIC or cCIC is formed, the clearance mechanism may become saturated which potentially leads to vascular immune complex (IC) deposition and inflammation. Limited information is available on the effect of different treatment related procedures as well as biomarkers of IC-related vascular disease. In order to explore the effect of different dose regimens on IC formation and deposition, and identification of possible biomarkers of IC deposition and IC-related pathological changes, C57BL/6J and BALB/c mice were dosed subcutaneously twice weekly with bovine serum albumin (BSA) for 13 weeks without adjuvant. After 6 and 13 weeks, CIC and cCIC were detected in plasma; after 13 weeks, IC deposition was detected in kidney glomeruli. In particular immunohistochemistry double-staining was shown to be useful for detection of IC deposition. Increasing dosing frequency or changing BSA dose level on top of an already established CIC and cCIC response did not cause changes in IC deposition, but CIC and cCIC concentrations tended to decrease with increased dose level, and increased cCIC formation was observed after more frequent dosing. The presence of CIC in plasma was associated with glomerular IC deposits in the dose regimen study; however, the use of CIC or cCIC as potential biomarkers for IC deposition and IC-related pathological changes, needs to be explored further.

Resistin and resistin-like molecules are pleiotropic cytokines that are involved in inflammatory diseases. Our previous work suggested that resistin has the potential to be used as a biomarker and therapeutic target for human pulmonary arterial hypertension. However, data are limited on the distribution of resistin in healthy human organs. In this study, we used our newly developed anti-human resistin (hResistin) antibody to immunohistochemically detect the expression, localization, and intracellular/extracellular compartmentalization of hResistin in a full human tissue panel from healthy individuals. The potential cross reactivity of this monoclonal anti-hResistin IgG1 with normal human tissues also was verified. Results showed that hResistin is broadly distributed and principally localized in the cytoplasmic granules of macrophages scattered in the interstitium of most human tissues. Bone marrow hematopoietic precursor cells also exhibited hResistin signals in their cytoplasmic granules. Additionally, hResistin labeling was observed in the cytoplasm of nervous system cells. Notably, the cytokine activity of hResistin was illustrated by positively stained extracellular material in most human tissues. These data indicate that our generated antibody binds to the secreted hResistin and support its potential use for immunotherapy to reduce circulating hResistin levels in human disease. Our findings comprehensively document the basal expression patterns of hResistin protein in normal human tissues, suggest a critical role of this cytokine in normal and pathophysiologic inflammatory processes, and offer key insights for using our antibody in future pharmacokinetic studies and immunotherapeutic strategies.

No abstract