Coronavirus is just a family of viruses. From what I understand, about 80-85% of cats have FeCov and most present mild symptoms like a runny nose. In about 0.5% of those infected, the virus will mutate and cause FIP. About 6 years ago, that would have been a death sentence as the death rate of FIP is 100%.

Gilead was working on a treatment and had one that was promising. They had started the process of getting it approved. But then the pandemic hit and they stopped all work. Since COVID is caused by a virus in the same family, they pivoted their research and eventually produced Remdesivir, which is an effective antiviral treatment for humans.

That also decided not to continue with the feline treatment because humans could technically use that instead of Remdesivir and Gilead would make less money.