FXIIIa-IN-1 (Compound 16) is a potent, selective inhibitor of FXIIIa (Factor XIIIa), with an IC50 of 2.4 μM. It inhibits FXIIIa by competing with the Gln-donor protein substrate (dimethylcasein). FXIIIa-IN-1 holds promise for research into the development of new, effective, and safe anticoagulants.

FXIIIa-IN-1, at a concentration of 10 μM for three days, shows no significant cytotoxicity in three different cell lines including breast (MCF-7 cells), intestinal (CaCo-2 cells), and kidney (HEK-293 cells). The compound inhibits fibrin(ogen) polymerization and the formation of γ-γ dimers in a concentration-dependent manner when applied at concentrations ranging from 5 to 2000 μM over a period of 24 hours. Furthermore, a 5 μL dose of FXIIIa-IN-1 for 5 minutes does not affect other coagulation factors (thrombin, factor Xa, factor XIa), indicating selectivity for FXIIIa.