Research has suggested DPPIV/CD26 as a functional receptor while playing a modulating or inhibiting role, and may potentially prevent infection or progression of COVID-19.1 There is also evidence that suggests that DPPIV inhibitors modulate inflammation.1 Although a direct involvement of DPPIV and SARS-CoV-2 infection remains unclear, there is a potential relationship.
Cathepsin B & Cathepsin L
The S protein is important for coronavirus entry into cells. Cathepsins have been suggested as a potential inhibitor for SARS-CoV-2 entry into HEK 293/hACE2 cells. While Cathepsin B did not show an effect on virus entry, Cathepsin L decreased entry of SARS-CoV-2 in these cells by over 76% in a reported study2.