Immunosuppressants exert differential effects on pan‐coronavirus infection and distinct combinatory antiviral activity with molnupiravir and nirmatrelvir

Abstract Background Immunocompromised populations, such as organ transplant recipients and patients with inflammatory bowel disease (IBD) receiving immunosuppressive/immunomodulatory medications, may be more susceptible to coronavirus infections. However, little is known about how immunosuppressants affect coronavirus replication and their combinational effects with antiviral drugs. Objective This study aims to profile the effects of immunosuppressants and the combination of immunosuppressants with oral antiviral drugs molnupiravir and nirmatrelvir on pan‐coronavirus infection in cell and human airway organoids (hAOs) culture models. Methods Different coronaviruses (including wild type, delta and omicron variants of SARS‐CoV‐2, and NL63, 229E and OC43 seasonal coronaviruses) were used in lung cell lines and hAOs models. The effects of immunosuppressants were tested. Results Dexamethasone and 5‐aminosalicylic acid moderately stimulated the replication of different coronaviruses. Mycophenolic acid (MPA), 6‐thioguanine (6‐TG), tofacitinib and filgotinib treatment dose‐dependently inhibited viral replication of all tested coronaviruses in both cell lines and hAOs. The half maximum effective concentration (EC50) of tofacitinib against SARS‐CoV‐2 was 0.62 μM and the half maximum cytotoxic concentration (CC50) was above 30 μM, which resulted in a selective index (SI) of about 50. The anti‐coronavirus effect of the JAK inhibitors tofacitinib and filgotinib is dependent on the inhibition of STAT3 phosphorylation. Combinations of MPA, 6‐TG, tofacitinib, and filgotinib with the oral antiviral drugs molnupiravir or nirmatrelvir exerted an additive or synergistic antiviral activity. Conclusions Different immunosuppressants have distinct effects on coronavirus replication, with 6‐TG, MPA, tofacitinib and filgotinib possessing pan‐coronavirus antiviral activity. The combinations of MPA, 6‐TG, tofacitinib and filgotinib with antiviral drugs exerted an additive or synergistic antiviral activity. Thus, these findings provide an important reference for optimal management of immunocompromised patients infected with coronaviruses.