Controls with pp-VSV-G, which does not activate the acid sphingomyelinase/ceramide system and does not employ this system for cellular infection as previously shown (14), demonstrated that pp-VSV-G entry was not modulated by ambroxol (Fig. 4A), indicating that ambroxol specifically blocks entry of pp-VSV-SARS-CoV-2 spike by inhibition of the acid sphingomyelinase/ceramide system. The gene discussed is SMPD1; the disease is infection.