Famotidine

Caki-2 cells were cultured in McCoy’s 5A (modified) medium supplemented with 10% FCS, Calu-3 cells were cultured in MEM with 10% FCS and 1x non-essential amino acids and both obtained from ATCC (Manassas, VA, USA). HEK293T cells were cultured in DMEM supplemented with GlutaMAX, 10% heat-inactivated FCS. Caco-2 cells were from Sigma Aldrich (Schnelldorf, Germany) and were cultured in EMEM medium supplemented with 10% FCS, L-glutamine and non-essential amino acids (M7145, Sigma Aldrich, Schnelldorf, Germany). HepG2 was obtained from Sigma Aldrich (Schnelldorf, Germany) and cultured in DMEM supplemented with GlutaMAX and 10% heat-inactivated FCS. All media contained 1% penicillin/streptomycin and the cells were cultured at 37 °C in a 5% CO₂ atmosphere. Silvestrol was dissolved in DMSO and further diluted in media (c_stock = 6 mM, maximal DMSO concentration during experiments 0.1% v/v). EGTA, famotidine and carbamazepine were from Sigma Aldrich (Schnellendorf, Germany). Lucifer Yellow (sc-215269) was obtained from Santa Cruz. Celecoxib was synthesized by WITEGA Laboratorien Berlin-Adlershof GmbH (Berlin, Germany). Forskolin and ionomycin were obtained from Sigma Aldrich (Schnelldorf, Germany). Silvestrol was provided by the Sarawak Biodiversity Centre (Kuching, North-Borneo, Malaysia; purity > 99%) and zotatifin was bought from MedChemExpress (USA, purity: 98%).

Lipopolysaccharide (E. coli. 0111:B4, Cat# L2630), histamine (Cat # H7125), ranitidine (Cat # R101), famotidine (Cat # F6889) and cimetidine (Cat # C4522) were purchased from Sigma (St. Louis, MO). famotidine (iv vial, 20 mg/2 ml) was from APP Pharmaceutical LLC (Schaumburg, IL). Tiotidine (Cat # 0826) was from Tocris Bioscience (Minneapolis, MN). Fetal bovine serum was obtained from Gibco BRL (Carlsbad, CA). Glutamine was from Biowhittaker Inc., (Walkersville, MD). Thioglycollate medium was purchased from Becton Dickinson Co., (Sparks, MD). Protease inhibitor minitablets (Cat # A32953) were form Thermo Fisher Scientific Inc., (Waltham, MA).

Famotidine was acquired from Sigma Aldrich (Missouri, USA; cat. No. F6889). Compound 6, a previously reported inhibitor of SARS-CoV-2 PL^pro function^{21 (link)} was acquired from MedChem Express, Inc. (New Jersey, USA; cat no. HY-17542). ML188, a compound with known 3CL^pro inhibitory activity¹⁵ was also acquired from MedChem Express, Inc. (cat. no HY-136259). Similarly, remdesivir. (cat. No HY-104077) an inhibitor of SARS-CoV-2 replication^{2 (link)} was purchased from the same vendor. All compounds were dissolved in 100% DMSO at 100 mM.