 Tranexamic acid also directly inhibits the activity of plasmin with weak potency (IC50 = 87 mM), and it can block the active-site of urokinase plasminogen activator (uPA) with high specificity (Ki = 2 mM) among all the serine proteases.Tranexamic acid was first synthesized in 1962 by Japanese researchers Shosuke and Utako Okamoto.It has been included in the WHO list of essential medicines.