PROS1 and infection: Since SARS-CoV-2 preferentially invades host cells at the plasma membrane (Hoffmann et al., 2020b) due to structural alterations in the proteolytic activation site of the S protein (Zhu et al., 2020), the achievable concentrations of CQ and HCQ at the prime site of infection might thus be too low to inhibit SARS-CoV-2 spread (Figure 3).