Chain mispairing occurs when the heavy and light chains of two different antibody arms combine in the wrong order during co-expression, producing a mix of the desired bispecific molecule and unwanted byproducts. Because only a correctly paired molecule has the intended dual specificity, manufacturers need engineering solutions — such as knobs-into-holes interfaces, electrostatic steering, or a shared common light chain — to force correct assembly. These solutions are exactly what this patent landscape tracks, and the dense prior art around the earliest such interfaces is why later filers often work around rather than on top of them.

The assignee ranking in this dataset shows a small group of large pharmaceutical filers holding a disproportionate share of records, with the top five assignees together accounting for 30.8% of all 37,330 records in scope. The single most-cited document in the corpus, cited 4,538 times, specifically covers electrostatic steering for Fc-heterodimeric molecules, underlining how foundational that filing is to everything that followed. New entrants typically need to check their proposed interface design against this concentrated cluster before committing to a manufacturing route.

Filing activity rose steadily from 1,338 records in 2017 to a peak of 1,915 in 2021, then eased to 1,485 by 2024 — a 22% decline over that three-year span. That does not mean the field is dying; it more likely means the core pairing mechanisms are well-claimed and new activity is shifting toward applications, formats and manufacturing refinements. Filings from 2025 onward are still understated in the data because publication typically lags filing by around 18 months.