PDE4A and COVID-19: Of note, there were 19 druggable genes with 117 targeting drugs yielding remarkably higher single‐cell druggable gene scores (scDGSs >120 and FDR < 0.05) in lung MSCs for treating severe COVID‐19, including CCR1, TNFRSF4, PDE4A, and IFNAR2 (Figures 5M, S22A,B, and Table S16).