Competitive ligand binding assay for detecting neutralizing antibodies

The method of any one of the above claims, wherein the capture reagent comprises the labeled biotherapeutic protein.

The method of any one of the above claims, wherein the capture reagent is labeled sarilumab.

The method of any of the above claims, wherein the detection reagent is labeled soluble IL-6 receptor α.

The method of any of the above claims wherein the patient sample is subjected to treatment with low pH prior to step (b).

The method of any of the above claims, wherein the assay exhibits a sensitivity tolerance of about 150 ng/mL, a drug tolerance of about 500 ng/mL, and a target interference tolerance of about 1 μg/mL.

A method for detecting the presence of neutralizing antibodies to sarilumab, wherein sarilumab has been administered to a patient in need, comprising the steps of (a) combining a patient serum sample with a capture reagent comprising biotinylated sarilumab, (b) subjecting the combined serum sample and capture reagent to treatment with low pH, followed by a neutralizing step;

• and (d) adding a detecting reagent, wherein the detecting reagent comprises labeled soluble IL-6 receptor α, wherein a decreased signal relative to a control sample indicates the presence of a neutralizing antibody to the biotherapeutic agent.

A kit, comprising the capture and detection reagents of any of the above claims and instructions for use.