O07 FXR antagonists as new agents for COVID19

Introduction The management of COVID19 is complicated by vaccine availability, the modest efficacy of existing treatments, and the potential for viral resistance. Therefore, there is a pressing need for new prophylactic and therapeutic agents. The viral receptor ACE2 is an ideal target as it is required for SARS-CoV-2 entry in host cells. Modifying ACE2 expression could prevent infection and/or limit disease progression. Nevertheless, the mechanisms controlling ACE2 expression remain elusive. Aims To identify pathways controlling the transcriptional regulation of ACE2, and exploit them to reduce SARS-CoV-2 infection. Methods Organoids from primary biliary, intestinal and pulmonary epithelia were derived and cultured as previously described. Single-cell RNA sequencing, QPCR, immunofluorescence and flow cytometry were used to assess marker expression. Chromatin immunoprecipitation was used to assess FXR binding on DNA. Bronchoalveolar lavage SARS-CoV-2 patient isolates were used for infection experiments. Human livers not used for transplantation were connected to the metra (OrganOx) normothermic perfusion device and perfused ex-situ using therapeutic doses of UDCA for 12 hours. ACE2 activity was measured following manufacturer's instructions. Patient data from the COVID-Hep and SECURE-Liver registries were compared using propensity score matching for sex, age and Child-Turcotte-Pugh score. Results We first demonstrated that cholangiocytes are susceptible to SARS-CoV-2 infection in vivo and in organoid culture. We then used cholangiocyte organoids to identify FXR as a transcriptional regulator of ACE2. We validated our results in pulmonary and intestinal organoids, showing that ACE2 regulation by FXR represents a broad mechanism present in multiple COVID19-affected tissues. We then demonstrated that approved FXR inhibitors, such as ursodeoxycholic acid (UDCA) and z-guggulsterone (ZGG), decrease ACE2 levels and reduce viral infection in vitro in primary biliary, intestinal and pulmonary organoids. We interrogated the impact of systemic UDCA administration in human livers perfused ex-situ, demonstrating reduced ACE2 levels and SARS-CoV-2 infection. Furthermore, we showed that commencing UDCA treatment lowers ACE2 levels in primary biliary cholangitis (PBC) patients. Finally, we identified a correlation between UDCA treatment and better clinical outcome in COVID-19 patients, including hospitalisation, ICU admission, mechanical ventilation and death, using registry data. Conclusion We identified FXR as a novel master regulator of ACE2 expression. Using a bench-to-bedside approach we combined in vitro, ex-vivo and patient data to demonstrate the efficacy of ACE2 downregulation against SARS-CoV-2 infection and identified approved and inexpensive drugs (UDCA, ZGG) which could be repurposed as prophylactic and therapeutic agents against SARS-CoV-2 infection, paving the road for future clinical trials.