KLK4 and diabetic macular edema: THR-149, a bicyclic peptide identified by a combination of phage-based selections and directed medicinal chemistry (see Teufel et al. [22] for a general description of the method), is a potent and specific inhibitor of plasma kallikrein currently being developed by Oxurion N.V. for the treatment of diabetic macular edema (source: www.clinicaltrials.gov).