[3] TAP molecules are highly dipolar,[4] and are arranged to form a twisted two-stranded antiparallel beta sheet followed by an alpha helix.

Kunitz domains are stable as standalone peptides, able to recognise specific protein structures, and also work as competitive protease inhibitors in their free form.

These properties have led to attempts at developing biopharmaceutical drugs from Kunitz domains.

The first of these drugs to be marketed was the kallikrein inhibitor ecallantide, used for the treatment of hereditary angioedema.

[12] Another example is depelestat, an inhibitor of neutrophil elastase that has undergone Phase II clinical trials for the treatment of acute respiratory distress syndrome in 2006/2007[13] and has also been described as a potential inhalable cystic fibrosis treatment.