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β-Cyclodextrins as affordable antivirals to treat coronavirus infection

The SARS-CoV-2 pandemic made evident that we count with few coronavirus-fighting drugs. Here we aimed to identify a cost-effective antiviral with broad spectrum activity and high safety and tolerability profiles. We began elaborating a list of 116 drugs previously used to treat other pathologies or characterized in pre-clinical studies with potential to treat coronavirus infections. We next employed molecular modelling tools to rank the 44 most promising inhibitors and tested their efficacy as antivirals against a panel of α and β coronavirus, e.g., the HCoV-229E and SARS-CoV-2 viruses. Four drugs, OSW-1, U18666A, hydroxypropyl-β-cyclodextrin (HβCD) and phytol, showed antiviral activity against both HCoV-229E (in MRC5 cells) and SARS-CoV-2 (in Vero E6 cells). The mechanism of action of these compounds was studied by transmission electron microscopy (TEM) and by testing their capacity to inhibit the entry of SARS-CoV-2 pseudoviruses in ACE2-expressing HEK-293T cells. The entry was inhibited by HβCD and U18666A, yet only HβCD could inhibit SARS-CoV-2 replication in the pulmonary cells Calu-3. With these results and given that cyclodextrins are widely used for drug encapsulation and can be safely administered to humans, we further tested 6 native and modified cyclodextrins, which confirmed β-cyclodextrins as the most potent inhibitors of SARS-CoV-2 replication in Calu-3 cells. All accumulated data points to β-cyclodextrins as promising candidates to be used in the therapeutic treatments for SARS-CoV-2 and possibly other respiratory viruses.