Chymase, a chymotrypsin-like serine protease that is abundant in secretory granules from mast cells, has been identified to be
a key enzyme in the local renin-angiotensin system (RAS) that generates angiotensin II (Ang II) independent of angiotensin converting
enzyme (ACE). The pathophysiological significance of alternative Ang II-forming pathways in human cardiovascular disease remains
controversial. Although chymase inhibitors, unlike ACE inhibitors and Ang II type 1 receptor blockers (ARBs), may only play a small
role in the regulation of the systemic RAS, the possible applications of chymase inhibitors as new drugs that inhibit the local RAS to prevent
cardiovascular diseases are described in animal models. In this review, we discuss the possible application of chymase inhibitors as
new drugs to inhibit the RAS in mainly cardiovascular diseases.