Anti-Natalizumab Antibodies

Antibodies for bioanalytical method development to measure natalizumab and biosimilar products

Ready-made recombinant monoclonal anti-idiotypic antibodies, highly specific for the humanized monoclonal antibody drug natalizumab (Tysabri®).

Type 1 anti-idiotypic antibody

Anti-Natalizumab Type 1 Antibodies

The Type 1 anti-natalizumab antibodies inhibit the binding of the humanized monoclonal antibody drug natalizumab to its target, human alpha4-beta1-integrin, and therefore detect free drug. These antibodies are ideal for use in direct and indirect ELISA, to develop pharmacokinetic (PK) bridging assays and as a reference standard for anti-drug antibody (ADA) assays.

Product codes: HCA248, HCA249, HCA249P, HCA250

These recombinant monoclonal antibodies are generated using the HuCAL® antibody library and an improved method of phage display, which results in highly specific and sensitive reagents. These are ideal for PK and PD assays. Antibodies are fully human, so they are also perfect as reference standards for ADA assays. The in vitro production of recombinant antibodies means that there is a consistent, secure supply throughout preclinical development and clinical trials, avoiding the need to develop new reagents.

More information about anti-idiotypic antibodies and their binding types and properties

Anti-biotherapeutic antibody quality control and characterization


Antibodies Specific to Natalizumab

Product Code Clone Antibody Specificity Binding Type Format Affinity KD, nM Assay Development Recommendations
HCA248 AbD21375 Natalizumab Type 1 Fab-FH1 2.1 Indirect ELISA
PK bridging ELISA, capture antibody with HCA249
HCA249 AbD21375_hlgG1 Natalizumab Type 1 Human lgG1 2.12 Indirect ELISA
PK bridging ELISA, detection antibody with HCA248
ADA assay, high affinity
HCA249P AbD21375_hlgG1 Natalizumab Type 1 Human IgG1
HRP labeled
2.12 Direct ELISA
PK bridging ELISA, detection antibody with HCA248
HCA250 AbD21384_hlgG1 Natalizumab Type 1 Human lgG1 12.22 Indirect ELISA
ADA assay, medium affinity

Table 1 Antibody Specifications
1 F=DYKDDDDK-tag; H=His-6-tag
2 Affinity measured in the monovalent Fab form


Pharmacokinetic Assay – Bridging ELISA Format

Pharmacokinetic (PK) Assay

Schematic image of PK Bridging ELISA. Anti-idiotypic capture antibody, Fab format (purple), monoclonal antibody drug (gold), anti-idiotypic detection antibody, Ig format (blue), labeled with HRP

PK assay, bridging format, using antibodies HCA248 and HCA249

Figure 1: PK assay, bridging format, using antibodies HCA248 and HCA249

Human anti-natalizumab antibodies, product codes HCA248 and HCA249

Figure 1: A microtiter plate was coated over night with anti-natalizumab antibody, clone AbD21375 (HCA248) at a concentration of 1 µg/ml. After washing and blocking with PBST+5% BSA, 10% human serum was added spiked with increasing concentrations of natalizumab. Detection was performed using HRP conjugated anti-natalizumab antibody, clone AbD21375_hIgG1 (HCA249P) at a concentration of 2 µg/ml in HISPEC assay diluent (BUF049A) and QuantaBlu™ fluorogenic peroxidase substrate. Data are shown as the mean of three measurements.

Protocol: PK bridging ELISA for use with anti-natalizumab antibodies HCA248 and HCA249


Inhibition ELISA

Inhibition of natalizumab binding to alpha4-beta1-integrin

Anti Human IgG HRP Labeled binding

Schematic image of inhibition assay. Drug target capture antigen (red), monoclonal antibody drug (gold), anti-IgG Fc specific detection antibody (gray) labeled with HRP

 Inhibition of natalizumab binding to human alpha4-beta1-integrin by HCA248

Figure 2: Inhibition of natalizumab binding to human alpha4-beta1-integrin by HCA248

Figure 2: A microtiter plate was coated over night with human alpha4-beta1-integrin at a concentration of 1 µg/ml. After washing and blocking with PBST+5% BSA, a pre-incubated mixture of natalizumab (0.3 µg/ml) plus increasing concentrations of human anti-natalizumab antibody clone AbD21375 (HCA248) in the monovalent Fab format was added. Free natalizumab, still capable of binding to the human alpha4-beta1-integrin coated plate, was detected using HRP conjugated mouse anti human IgG (Fc) CH2 domain (MCA647P) and QuantaBlu fluorogenic peroxidase substrate. Data are shown as the mean of three measurements.


Anti-Drug Antibody Assay - Bridging ELISA Format

Two anti-natalizumab antibodies in IgG1 format are available, each with a different affinity for the target (Table 1), allowing the ADA assay to be tailored to the specific needs of the developer.

Anti-Drug Antibody Assay

Schematic image of ADA bridging assay. Monoclonal antibody drug as capture antibody and detection antibody labeled with HRP (gold), fully human anti-idiotypic antibody, Ig format (blue)

ADA bridging ELISA with HCA249 or HCA250

Figure 3: ADA bridging ELISA with HCA249 or HCA250

Human anti-natalizumab antibodies, product codes HCA249 and HCA250

Figure 3: A microtiter plate was coated over night with natalizumab at a concentration of 1 µg/ml. After washing and blocking with PBST+5% BSA, PBST with 10% human serum was added spiked with increasing concentrations of human anti-natalizumab antibody, either HCA249 or HCA250. Detection was performed using HRP conjugated natalizumab*. Data are shown as the mean of three measurements.

Protocol: ADA bridging ELISA for use with anti-natalizumab antibody


Demonstration of Antibody Specificity

Specificity of anti-natalizumab antibody HCA248

Figure 4: Specificity of anti-natalizumab antibody HCA248

Human anti-natalizumab antibody, product code HCA248

Figure 4: A microtiter plate was coated over night with various antigens at a concentration of 5 μg/ml. After washing and blocking with PBST+5% BSA, detection was performed using human anti-natalizumab antibody clone AbD21375 (HCA248) at a concentration of 2 μg/ml followed by HRP conjugated rat anti-DYKDDDDK tag antibody (MCA4764P, 1:500 dilution) in HISPEC assay diluent (BUF049A) and QuantaBlu fluorogenic peroxidase substrate. 

* Antibody conjugated to HRP using a LYNX Rapid Conjugation Kit® (product codes LNK001P - LNK006P)


Licensed Use: For in vitro research purposes and for commercial applications for the provision of in vitro testing services to support preclinical and clinical drug development. Any re-sale in any form or any other commercial application needs a written agreement with Bio-Rad.

HuCAL® is a registered trademark of MorphoSys AG. QuantaBlu™ is a trademark of Thermo FisherScientific. Tysabri® is a registered trademark of Elan Pharmaceuticals, Inc.