Enzyme-linked immunosorbent assay (ELISA) for the quantitative determination of free adalimumab (Humira®) in serum and plasma with confirmation. The Assay Genie adalimumab ELISA has been especially developed for the quantitative analysis of free adalimumab in serum and plasma samples.

Solid phase enzyme-linked immunosorbent assay (ELISA) based on the sandwich principle. Standards and diluted samples (serum or plasma) are incubated in the microtitre plate coated with the reactant for adalimumab (Humira®). After incubation, the wells are washed. A horse radish peroxidase (HRP) conjugated probe is added and binds to adalimumab (Humira®) captured by the reactant on the surface of the wells. Following incubation, wells are washed, and the bound enzymatic activity is detected by addition of chromogen-substrate. The colour developed is proportional to the amount of adalimumab in the sample or standard. Results of samples can be determined directly using the standard curve.

Adalimumab (Humira®) is a recombinant human IgG1 monoclonal antibody specific for human tumor necrosis factor alpha (TNF-a). Adalimumab (Humira®) was created using phage display technology resulting in an antibody with human derived heavy and light chain variable regions and human IgG1:k constant regions. Adalimumab (Humira®) is produced by recombinant DNA technology in a mammalian cell expression system and is purified by a process that includes specific viral inactivation and removal steps. It consists of 1330 amino acids and has a molecular weight of approximately 148 kilodaltons.

Adalimumab (Humira®) binds specifically to (TNF-a) and blocks its interaction with the p55 and p75 cell surface TNF receptors. Adalimumab (Humira®) also lyses surface TNF expressing cells in vitro in the presence of complement. Adalimumab (Humira®) does not bind or inactivate lymphotoxin (TNF-beta). TNF is a naturally occurring cytokine that is involved in normal inflammatory and immune responses. Elevated levels of TNF are found in the synovial fluid of rheumatoid arthritis, including juvenile idiopathic arthritis, psoriatic arthritis, and ankylosing spondylitis patients and play an important role in both the pathologic inflammation and the joint destruction that are hallmarks of these diseases. Increased levels of TNF are also found in psoriasis (Ps) plaques.

Adalimumab is to treat various autoimmune diseases and works to treat inflammation. Adalimumab is administered to minimize pain and swelling due to various types of arthritis, including rheumatoid arthritis, psoriatic arthritis, juvenile idiopathic arthritis and ankylosing spondylitis. Adalimumab also treats various skin conditions including plaque psoriasis and hidradenitis suppurativa.

After treatment with adalimumab (Humira®), a decrease in levels of acute phase reactants of inflammation (Creactive protein [CRP] and erythrocyte sedimentation rate [ESR]) and serum cytokines (IL-6) was observed compared to baseline in patients with rheumatoid arthritis. A decrease in CRP levels was also observed in patients with Crohn's disease. Serum levels of matrix metalloproteinases (MMP-1 and MMP-3) that produce tissue remodeling responsible for cartilage destruction were also decreased after adalimumab (Humira®) administration. According to the prospectus; the maximum serum concentration (Cmax) and the time to reach the maximum concentration (Tmax) were 4.7 ± 1.6 ?g/mL and 131 ± 56 hours respectively, following a single 40 mg subcutaneous administration of adalimumab (Humira®) to healthy adult subjects.

The average absolute bioavailability of adalimumab (Humira®) estimated from three studies following a single 40 mg subcutaneous dose was 64%. The pharmacokinetics of adalimumab were linear over the dose range of 0.5 to 10.0 mg/kg following a single intravenous dose. The single dose pharmacokinetics of adalimumab in rheumatoid arthritis (RA) patients were determined in several studies with intravenous doses ranging from 0.25 to 10 mg/ kg. The distribution volume (Vss) ranged from 4.7 to 6.0 L. The systemic clearance of adalimumab is approximately 12 mL/hr. The mean terminal half-life was approximately 2 weeks, ranging from 10 to 20 days across studies. Adalimumab concentrations in the synovial fluid from five rheumatoid arthritis patients ranged from 31 to 96% of those in serum. In RA patients receiving 40 mg adalimumab (Humira®) every other week, adalimumab mean steady-state trough concentrations of approximately 5 mg/mL and 8 to 9 mg/mL, were observed without and with 3 methotrexate (MTX), respectively.

Serum concentration of adalimumab (Humira®) might be related to predict some clinical outcome during maintenance therapy. It was also possible that the surveillance of circulating adalimumab (Humira®) concentration during maintenance therapy represents a direct and/or indirect factor for some other side effects. In this context, identification of biomarkers for (non-)response and risk factors for adverse drug reactions that might be related to serum concentrations and maintaining the effective minimum concentration of adalimumab (Humira®) in order to potentially avoid some side effects with a reliable method might be beneficial.

Humira® is a registered trademark of AbbVie Biotechnology, Inc.