Previous pharmacokinetic study showed that patients treated with 1.25 mg/m2 omacetaxine every 12 h by subcutaneous injection may reach the maximal plasma concentration at 25.1 ng/mL (0.046 μM) and 36.2 ng/mL (0.066 μM) on days 1 and 11, respectively (Nemunaitis et al., 2013), which were below the EC50 against SARS-CoV-2 virus in vitro.