Given the beneficial role of inhaled recombinant GM-CSF in reducing mortality in preclinical pneumonia studies, inhaled sargramostim is under investigation to treat patients with COVID-19 (Table 2) (Huang et al., 2010; Huang et al., 2011; Bosteels et al., 2021; ClinicalTrials.Gov, 2020c; ClinicalTrials.Gov, 2020d; ClinicalTrials.Gov, 2020f; ClinicalTrials.Gov, 2021). Here, CSF2 is linked to pneumonia.