If it works it will block infection of new cells. Already infected cells will die and be shed.
Biologists can correct me if I'm wrong, but it seems like fighting infection is a war of attrition. So anything you can do that shifts the balance helps.
Some infections might be a war of attrition, but it's not something you can generalize. Fundamentally, stopping entry would just prevent the virus from infecting more cella in the body (which could worsen symptoms) - and coronavirus is more of your standard fast invasion - burn bright and strong before being eliminated style infection than a chronic slow burn, so stopping that fast invasion could help.