What makes you think they determined that by clinical trial?
I'd think their scientists would identify a compound that should function as a protease inhibitor, verify that action in the lab or a model (like the studies you posted), and then conduct clinical trials to see if that action was effective fighting the virus in people.
Clinical trials are very late in the drug development process. Long after the expected mechanism of action has been identified.
Ok, so you’re saying that the claim that Pfizer’s drug is a Protease inhibitor has not been proven in a clinical trial?