RSRGVFF (FOXP3 inhibitor P60) is a mixed-type angiotensin-converting enzyme ( ACE ) inhibitor with blood-brain barrier permeability, boasting an IC 50 value of 5.01 μM. RSRGVFF is capable of binding to both active and non-active sites of ACE and its substrate HHL complex, thus reducing the catalytic activity of ACE. RSRGVFF can be further utilized for research on lowering hypertension.