Famotidine increases cellular phospho-tyrosine levels.

While vaccines were being developed, the SARS-CoV-2 pandemic triggered a race to find known drugs that could be quickly repurposed to treat patients. One such candidate was famotidine, which retrospective cohort studies had shown increased survival in hospitalized patients. Computational studies had suggested that famotidine may target early viral proteases; however, ultimately, famotidine was shown not to function as a viral inhibitor. In contrast, we have observed a change in the cellular levels of phospho-tyrosine in A549 lung epithelial cells following treatment with famotidine. This quick change in phosphorylation was due mainly to a dose-dependent increase in cellular production of H(2)O(2). Notably, these changes in phospho-tyrosine levels were able to affect cell signaling; we detected an increased short- and long-term response to IFNα stimulation. Our results suggest that famotidine can increase the anti-viral state of non-infected cells thereby potentially increasing viral resistance.