Remdesivir is not the only antiviral effective against SARS-COV-2. It is a broad spectrum antiviral that has been effective against earlier coronaviruses. It is at least 7 years old and some phenotypes/strains of SARS-COV-2 are resistant to it. EIDD-1931(IV) and EIDD-2801 (tablet) are newer and effective against Remdesivir-resistant forms of SARS-COV-2 (and vice versa). The best treatment for severe cases is probably a combination of the two.
Science Translational Medicine 29 Apr 2020:
Vol. 12, Issue 541, eabb5883