If you’re talking about Regeneron, nobody knows if it actually works or not, it’s super early in clinical trials and is not approved for patient use unless administered through the “compassionate use”exception. It has yet to be proven safe or effective, no matter how positive it looks in the early stages of trials. That is why it’s not approved for the general public, it just has not met stringent FDA requirements yet.
I’m pretty sure he also got remdesivir and dexamethasone, which are available and approved by the FDA, and are now almost de facto standard of care for patients who are either very ill or at high risk of becoming extremely ill.
Dexamethasone is cheap and widely available, remdesivir is subject to shortages in hospitals from time to time, but lately has been fairly available with some exceptions, throughout the United States.