Same target, different stickiness: polyreactivity of therapeutic antibodies

The Challenge

Polyreactivity is the binding of an antibody to structurally unrelated molecules. Cross-interaction measures have been associated with faster antibody clearance in mice. Polyreactivity is one of several flags in multi-assay developability panels, so a useful screen reports both the breadth and the pattern of binding.

The Approach

Eight ligands are immobilized on one sensor chip by DNA-directed immobilization (DDI) and read in parallel while the antibody flows over them. Six clinical antibodies were profiled, among them two pairs that bind the same target, so a difference within a pair comes from the antibody, not from its target.

Key Results

• Two orders of magnitude: five of the six antibodies scored above the detection limit, with indices from 0.08 to 8.8.
• Same-target pairs resolved: briakinumab scored 69-fold above ustekinumab (IL-12/23 p40), and ravulizumab at least tenfold above eculizumab (C5), although the two differ at only four amino acid positions.
• Ligand fingerprints: briakinumab binds most on the acidic HSA and least on the basic lysozyme, a pattern consistent with electrostatic binding.
• Fast: about 25 min of flow per antibody, ligand loading included.

Why It Matters

Each index comes with its ligand fingerprint, so a high value can be traced to one surface or to many. The index is a ranking at a stated concentration, not an affinity and not a pass or fail threshold; thresholds need calibration against orthogonal data.