Chymase converts Ang I to Ang II with greater efficiency and selectivity than ACE [4] . The rate of this conversion by chymase is approximately four fold higher than ACE. Chymase shows enzymatic activity immediately after its release into the interstitial tissues at pH 7.4 following various stimuli in tissues. Since chymase has no enzymatic activity in normal tissues, chymase inhibitors are expected to have high safety because chymase inhibitors may not have an effect on any other targets in normal tissues [5] . In order to generate Ang II, human, monkey, dog and hamster chymases cleave the angiotensin I at Phe8-His9 peptide bond. Chymase also converts precursors of transforming growth factor-β (TGF-β) and matrix metalloproteinase (MMP)-9 to their active forms thus contributing to vascular response to injury. Both TGF-β and MMP-9 are involved in tissue inflammation and fibrosis, resulting in organ damage [6] . Previous studies have demonstrated the involvement of chymase in the escalation of dermatitis and chronic inflammation pursuing cardiac and pulmonary fibrosis [7] . Therefore, inhibition of chymase is likely to divulge therapeutic ways for the treatment of cardiovascular diseases, allergic inflammation, and fibrotic disorders. Chymase inhibition may also be useful for preventing the progression of type 2 diabetes, along with the prevention of diabetic retinopathy [8] . Moreover, the role of chymase in inflammation has prompted its restorative value in diseases such as chronic obstructive pulmonary disease (COPD) and asthma [9] .