Table 1.

Representative peptide boronic acids have been used as serine protease inhibitors since 2011.

Compound	Structure	Target	Pathology
6 (WLS6a)		hClpXP	IC50 of hClpXP = 29 μM [33]; proteolytic cleavage of casein mediated by hClpXP was clearly inhibited as demonstrated by in vitro study [33].
7 (MG262)		hClpXP	IC50 of hClpXP ≈ 40 μM [34].
8 (Talabostat, Val-boroPro)		DPP4, FAP, DPP8, DPP9	IC50 of DPP4 < 4 nM; IC50 of FAP = 560 nM; IC50 of DPP8 = 4 nM; IC50 of DPP9 = 11 nM [36,37]; Phase II studies for prostate cancer and solid tumors; Phase I/II study for pancreatic cancer (https://adisinsight.springer.com/drugs/800016264, accessed on 5 November 2021).
9 (ARI-3099)		FAP	IC50 of FAP = 36 nM; inhibition of cellular prolyl endopeptidase activity but no cytotoxicity in murine FAP transfected HEK293 cells were observed [41,42].
10 (ARI-3531)		PREP	IC50 of PREP = 1.3 nM; complete inhibition of cellular prolyl endopeptidase activity in the mock-transfected cells but only approximately 60% inhibition in the mFAP transfected cells were observed [41,42].
11		virus protease	IC50 of Dengue virus protease = 66 nM; IC50 of West Nile virus protease = 110 nM; IC50 of Zika virus protease = 250 nM; Antiviral effect: EC50 of Dengue virus = 30 μM; EC50 of West Nile virus = 38 μM [43].