FXR INHIBITION AS A NEW STRATEGY AGAINST COVID19 T Brevini1, M Maes2, GJ Webb3, CD Fuchs4, G Buescher5

Introduction: Vaccines revolutionised the management of COVID19. Nevertheless, they lack efficacy in high-risk or vulnerable groups (e.g., immunosuppressed patients), who may not mount an appropriate immune response. Monoclonal antibodies represent the gold-standard agents for such cases;but they are limited by availability, need for parenteral administration and the risk for viral escape because of spike protein mutations. Therefore, there is a pressing need for new prophylactic agents less prone to resistance.The viral receptor ACE2 represents an ideal target as it is essential for viral entry and transmission and because being a host protein it is not affected by viral mutations. However, the regulation of ACE2 remains elusive, due to the lack of appropriatein vitromodels. Cholangiocytes show one of the highest ACE2 expression levels in the body, representing an ideal platform for these studies. Here, we use cholangiocyte organoids as proof-of-principleto identify that the bile acid receptor FXR regulates ACE2 expression and SARS-CoV-2 infectionin vitro. We validate these findings in lung and gut organoids, animal models, human organs perfusedex situand patient cohorts. Aims & Methods: 1. Identify pathways controlling the transcriptional regulation of ACE2 2. Identify drugs modulating these pathways as novel prophylactic and therapeutic agents for COVID19. Organoids were propagated using established protocols. Marker expression was assessed using single-cell RNA sequencing, QPCR, and immunofluorescence. FXR binding on DNA was assessed with chromatin immunoprecipitation. SARS-CoV-2 was isolated from bronchoalveolar lavage of a COVID19 patient. Syrian golden hamsters were infected via direct inoculation and QPCR on oral swab, nasal turbinate and lung samples was used to measure SARS-CoV-2 infection. Human livers and lungs not used for transplantation were perfusedex-situusing normothermic perfusion. Nasopharyngeal swabs were used to measure ACE2 expression in nasal epithelial cells of healthy individuals taking UDCA at the standard therapeutic dose of 15 mg/kg/day. Patient registry data were compared using propensity score matching for sex, age, diabetes, NAFLD and Child- Turcotte-Pugh score. Result(s): We identified that FXR directly regulates ACE2 transcription in cholangiocyte organoids, while FXR inhibition with the approved drug ursodeoxycholic acid (UDCA), reduced ACE2 expression and SARS-CoV-2 infectionin vitro. We confirmed this mechanism in organoids from other COVID19-affected tissues, including the respiratory and intestinal systems. We validated our findingsin vivoin Syrian golden hamsters, showing that treatment with UDCA downregulates ACE2 and prevents SARS-CoV-2 infection. We confirmed that UDCA reduces ACE2 and SARS-CoV-2 infection in human lungs and livers perfusedex-situ. We performed a clinical study demonstrating that UDCA lowers ACE2 levels in the nasal epithelium of 6 healthy volunteers. Finally, we identified a correlation between UDCA and better clinical outcomes (hospitalisation, ICU admission and death) in COVID19 patients receiving UDCA for cholestatic diseases using the COVID-Hep and SECURELiver registry data. Conclusion(s): We identified FXR as a novel regulator of ACE2 expression. Using a bench-to-bedside approach combining in vitroand in vivomodels, exsituperfused human organs and clinical data we showed that FXR inhibition prevents or reduces SARS-CoV-2 infection and identified UDCA as an approved, cost-effective drug which could be repurposed for COVID19, paving the road for future clinical trials.

Global variability in admission to intensive care units for patients with chronic liver disease and COVID-19: International registry data

Background: The COVID-19 pandemic has provided a unique opportunity to evaluate global intensive care unit (ICU) admission practices. Patients with chronic liver disease (CLD) and cirrhosis may have limited or variable access to ICU. We aimed to describe international ICU admission rates and outcomes in critically-ill patients with CLD and COVID-19. Methods: Data were combined from two international registries (SECURE-Liver and COVID-Hep) for patients with CLD and lab-confirmed COVID-19 deemed sick enough to require ICU admission by the reporting clinician. Rates of ICU admission or decline, and respective outcomes were compared by country. We performed a secondary analysis comparing ICU admissions/declines and outcomes from the United States (US) and United Kingdom (UK), the two greatest contributing countries. Results: Between 25 March 2020 and 3 February 2021, 319 patients with CLD and COVID-19 from 27 countries were deemed to require ICU care. There was considerable country-level variability in ICU decline rates (Figure 1A), although mortality following ICU admission was similar by country (Figure 1B). Rates of ICU admission differed significantly between the US (75/79, 95%) and UK (22/77, 29%) (p<0.001). However, there were no differences in the US and UK in mortality after ICU admission (42/75 [56%] vs. 10/22 [45%];p=0.468;Figure 1B) or mortality after invasive ventilation (29/59 [49%] vs. 9/17 [53%];p=1.000). Both in those requiring ICU admission and admitted to the ICU, there were no differences in age, sex, Charlson Comorbidity Index or Child Pugh Score. Only four US patients were declined ICU admission of whom 2 (50%) died compared to 55 UK patients declined ICU admission of whom 51 (93%) died. Baseline factors associated with being declined ICU admission in the UK were older age, alcohol-related liver disease, and Child B/C cirrhosis. In both US and UK cohorts, the reason for not admitting patients to ICU was due to this being deemed inappropriate (futile) by the responsible clinician, except for one case in both countries in which no ICU bed was available. Information relating to patient goals of care, longterm outcomes in survivors, and granular detail regarding organ support requirements were not available. Conclusion: Patients with CLD and critical COVID-19 were over 3-times more likely to be admitted to ICU in the US than the UK despite having similar baseline characteristics. However, the rates of mortality following ICU admission were comparable between the two countries. ICU bed availability was not a key factor in decline rates. The differing thresholds for escalation to ICU with similar post admission outcomes warrants further discussion.

Fxr as a new therapeutic target for COVID-19

Background: Despite recent advances, 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. Modifying the expression of the SARS-CoV-2 entry receptor ACE2 could prevent viral infection and limit disease progression. Here, we identify that ACE2 expression is controlled by the transcription factor farnesoid X receptor (FXR) and demonstrate that ACE2 downregulation through FXR antagonism, using approved drugs, such as ursodeoxycholic acid (UDCA), could represent a novel therapeutic strategy to complement current approaches. Methods: Primary cholangiocyte, pulmonary and intestinal organoids were propagated using established protocols. Marker expression was assessed using singlecell RNA sequencing, QPCR, immunofluorescence and flow cytometry. FXR binding on DNA was assessed with chromatin immunoprecipitation. SARS-CoV-2 was isolated from bronchoalveolar lavage of a COVID19 patient. Viral load was measured via QPCR. Human livers not used for transplantation were perfused ex-situ using the metra (OrganOx) normothermic perfusion device. Serum ACE2 activity was measured with commercial kits. Patient data from the COVID-Hep and SECURE-Liver registries were compared using propensity score matching. Results: FXR activation directly upregulated ACE2 transcription in organoids from COVID19 affected tissues, including the biliary, gastrointestinal and respiratory systems. Conversely, FXR antagonism with z-guggulsterone or UDCA, had the opposite effect. Importantly, both drugs reduced susceptibility to SARS-CoV-2 infection in lung, cholangiocyte and gut organoids. Furthermore, systemic administration of UDCA in human organs perfused ex-situ downregulated ACE2 and reduced SARS-CoV-2 infection ex-vivo. Oral UDCA rapidly reduced serum ACE2 in vivo. Registry data showed a correlation between UDCA administration and better clinical outcomes in COVID19 patients, including hospitalisation, ICU admission, mechanical ventilation and death. Conclusion: We discovered FXR as a novel therapeutic target against SARS-CoV-2 and we identified approved FXR inhibitors which could be repurposed to potentially treat COVID19, paving the road for future clinical trials to validate these results.

Intensive care unit (icu) escalation more likely among liver transplant (lt) recipients with sarscov-2 compared to patients with decompensated cirrhosis

Background: A number of factors can inform ICU escalation decisions, including the likelihood of survival and patient co-morbidities. This study examined prior liver transplant (LT) recipients and patients with chronic liver disease (CLD) diagnosed with SARS-CoV-2, and compared the rate of ICU admission and decline amongst those who were sick enough to require ICU care. Methods: Patient data from 12 March 2020 to 6 May 2021 was extracted using two international reporting registries (SECURE-Liver and COVID-Hep). Patients had a history of LT or CLD, laboratory-confirmed SARS-CoV-2, and were deemed ill enough to require ICU care. Patients were either admitted to the ICU, or declined admission due to inadequate capacity or because ICU escalation was deemed inappropriate. We compared patient characteristics by ICU decline, and compared ICU decline rates by LT and CLD categories with unadjusted and multivariable logistic regression. Results: 173 LT recipients were admitted to the hospital with SARS-CoV-2 (transplant year 1986-2020, median age 63, 74% male), and 66 (38.2%) were deemed unwell enough to require ICU care. Among those sick enough to require ICU care, 55 (83.3%) were admitted to the ICU and 11 (16.7%) were declined admission. Compared to those admitted to the ICU, patients declined ICU admission were significantly older (median 69 yrs vs 62 yrs, p=0.01) but otherwise similar in other characteristics. ICU decline rates in prior LT recipients (16.7%) were similar to patients with non-cirrhotic CLD (16.1%, p=0.96), but substantially lower than patients with Child A cirrhosis (31.8%, p=0.03), Child B cirrhosis (37.1%, p=0.006) and Child C cirrhosis (38.7%, p=0.004). Differences in ICU decline between LT recipients and Child B or C cirrhosis remained statistically significant after adjustment for age, sex and major co-morbidities. Among patients admitted to the ICU, mortality was higher in LT recipients compared to non-cirrhotic CLD (OR 0.31, 95% CI 0.14-0.71) but lower in LT recipients compared to Child C cirrhosis (OR 3.85, 95% CI 1.47-10.11) after adjustment for age, sex and co-morbidities (see Figure 1). Conclusion: ICU decline was less likely in LT recipients compared to patients with decompensated cirrhosis. LT recipients may be seen as gaining more benefit from ICU care, given the higher mortality amongst patients with decompensated cirrhosis. This is in line with prior data showing decompensated cirrhosis is a predictor of higher mortality in patients with SARS-CoV-2. Moreover, large investment of resources in LT recipients may make them more likely to be admitted to the ICU.

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.