TNF-α inhibitors are excellent tools for treatment of severe chronic inflammatory diseases. Experience shows that a large proportion of patients (60-70%) with various autoimmune diseases such as rheumatic disorders and inflammatory bowel disease have an excellent primary response to treatment with TNF-α inhibitors.
Treatment with TNF-α inhibitors show a large variation between patients, in terms of treatment dose and interval between dosing. Consequently, many patients may benefit from an individualized treatment approach depending on their response to the biological drug.
There is a significant percentage of patients for whom TNF-α inhibitors fail to demonstrate efficacy (primary failure) or where the effect of the TNF-α inhibitors decreases over time despite an initial good response (secondary failure) (Bendtzen 2011 and 2013, Vincent 2013). Tests measuring drug activity (concentration) of TNF-α inhibitors and NAbs (neutralising anti-drug-antibodies) can be used as a tool to establish why the patient has no effect of their treatment.
Wieslab Diagnostic Services uses a test technology that measures the biological activity of the drug which gives a high therapeutic significance. If the test shows that the patient has low concentrations of the TNF-α inhibitors and/or has developed NAbs, it is both clinically and economically correct to adjust the treatment regime.
NAbs - Testing for NAbs against TNF-α inhibitors are performed only when the concentration of TNF-α inhibitors activity in serum is < 0.65 µg/mL.
Monitoring biologic levels in individual patients allows optimization of treatment efficacy by adjusting therapy depending on the specific response of the patient. When drug levels are decreased in a non-responder, this may reflect formation of inactivating antibodies directed to the biologic treatment. Immunogenicity testing identifies presence or absence of inactivating antibodies, which guides the next treatment decision – switch to other biological treatment, lowering of dose or intensify dosing. Reducing drug dosage in well-responding patients with relatively high drug levels cuts down cost. A personalized approach can improve therapy efficacy and quality of life.
The assay for TNF-α inhibitor NAbs is based on an in vitro reporter cell line (iLite) which is used to measure the activity (concentration) of the drug (Lallemand 2011). In short, the NAbs tests show if antibodies in patient serum can prevent TNFα-inhibitor activity in an in vitro cell model.
1. The reporter cells in the test carry a TNF-α-induceable, NFkB-regulated Firefly lucifer's reporter gene construct. When TNF-α is added to the reporter cell, the reporter gene is activated via NFkB to express Firefly luciferase. The level of Firefly luciferase is normalized relative to the level of the Renilla luciferase gene, which is under the control of a constitutive promoter in the same cell.
2. Serum from a patient treated with TNF-α inhibitor is mixed with a predetermined amount of TNF-α. The amount of TNF-α-inhibitor correlates inversely with the amount of luminescence (light).
3. The patient's serum is mixed with a certain amount of TNF-α-i (the TNF-α-i used for the treatment of the individual patient) and incubated. Then this mix is added to a predetermined amount of TNF-α and cells.
4. In neutralising anti-drug antibodies (NAbs) against TNF-α-i: NAbs bind TNF-α-i which thus cannot bind to TNF-α. This means that TNF-α can bind to the TNF-α receptor and provide normal activity in the cell.
Before analysis, the sample is treated with acid and diluted to allow dissolution of immune complexes. This process describes an EIA (enzyme immunoassay) designed to determine the presence of binding antibodies to TNF-α inhibitors. The process can be described as a sandwich EIA.