Improved immunogenicity assays

Method according to any of the preceding claims, in which the variant has essentially the same amino acid sequence as the ISV-based drug, except for the changes to the CDRs that, in the variant, remove the ability of the ISV(s) present in the variant to bind to the therapeutic target(s) of the ISV-based drug.

Method according to any of the preceding claims, in which the variant has a degree of sequence identity (as defined herein) with the ISV-based drug of at least 90%, such as at least 95%, in particular at least 99% (up to and including 100%), not taking into account the changes in the CDRs that, in the variant, remove the ability of the ISV(s) present in the variant to bind to the therapeutic target(s) of the ISV-based drug.

Method according to any of the preceding claims, in which performing the bridging anti-drug antibody assay comprises the steps of:

• a) contacting said sample with a capturing agent that is immobilized on a support, wherein said capturing agent is or essentially consists of said ISV-based drug, under conditions such that any anti-drug antibodies against ISV-based drug can bind to said capturing agent;
• b) (optionally) removing any components or constituents present in said sample that do not bind to the capturing agent;
• c) detecting or measuring any anti-drug antibodies that have bound to the capturing agent, by contacting the complex of the capturing agent and any captured anti-drug antibodies with a detection agent, which detection agent is or essentially consists of said ISV-based drug which is linked to a detectable label, under conditions such that said detection agent can bind to (the complex of the capturing agent and) any captured anti-drug antibodies.

Method according to any of the preceding claims, which is performed on a sample that contains (or is suspected to contain), both neutralizing and non-neutralizing ADAs against the ISV-based drug.

Method according to any of the preceding claims, which is performed on a sample obtained from a human subject.

Method according to any of the preceding claims, which is performed on a sample of whole blood, serum, plasma, lymph fluid, ocular fluid, bronchoalveolar fluid/BALF, cerebrospinal fluid or another biological fluid (such as sputum or nasal washes);

• and in particular a sample of whole blood, serum or plasma.

Method according to any of the preceding claims, in which the ISV-based drug has a half-life in man (expressed as t ½ beta) of at least 3 days.

Method according to any of the preceding claims, in which the ISV-based drug comprises at least two ISVs, such as 2, 3, 4 or 5 ISVs