In vitro efficacy of artemisinin-based treatments against SARS-CoV-2

Abstract

Effective and affordable treatments for patients suffering from coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), are needed. We report in vitro efficacy of Artemisia annua extracts as well as artemisinin, artesunate, and artemether against SARS-CoV-2. The latter two are approved active pharmaceutical ingredients of anti-malarial drugs. Concentration–response antiviral treatment assays, based on immunostaining of SARS-CoV-2 spike glycoprotein, revealed that treatment with all studied extracts and compounds inhibited SARS-CoV-2 infection of VeroE6 cells, human hepatoma Huh7.5 cells and human lung cancer A549-hACE2 cells, without obvious influence of the cell type on antiviral efficacy. In treatment assays, artesunate proved most potent (range of 50% effective concentrations (EC50) in different cell types: 7–12 µg/mL), followed by artemether (53–98 µg/mL), A. annua extracts (83–260 µg/mL) and artemisinin (151 to at least 208 µg/mL). The selectivity indices (SI), calculated based on treatment and cell viability assays, were mostly below 10 (range 2 to 54), suggesting a small therapeutic window. Time-of-addition experiments in A549-hACE2 cells revealed that artesunate targeted SARS-CoV-2 at the post-entry level. Peak plasma concentrations of artesunate exceeding EC50 values can be achieved. Clinical studies are required to further evaluate the utility of these compounds as COVID-19 treatment.

In vitro efficacy of Artemisia extracts against SARS-CoV-2

“…It has been suggested that flavonoids present in Artemisia species are active against SARS-CoV-2 [ 27 ]. It should be noted that the EC50 value of artemisinin differs from a previous report [ 16 ] due to differences in the treatment duration. The previous study measured a reduction in viral replication and spread in the presence of the drug over 24 h of infection.…”

“…Given the similarities between SARS-CoV and SARS-CoV-2, we investigated the use of artemisinin 1 (Fig. 1 ), artemisinin derivatives such as artesunate 2 , as well as A. annua extracts for the inhibition of SARS-CoV-2 in vitro [ 16 ]. Artesunate was found to be most effective in inhibiting the virus, but A. annua extracts also revealed some activity in vitro.…”

“…3 ). This finding was surprising considering that A. afra does not contain artemisinin and even more so since synthetic artesunate, a pharmacokinetically improved derivative of artemisinin, proved most active in previous in vitro SARS-CoV-2 inhibition studies [ 16 , 25 ]. Our findings suggest that not just artemisinin, but also other compounds present in the Artemisia extracts have inhibitory effects towards SARS-CoV-2.…”

“…In addition to pure, semi-synthetic substances, Artemisia teas and plant material have been explored for use to treat different diseases [ 14 ]. A. annua extract had shown anti-viral activity in vitro against SARS-CoV in 2005 [ 15 ] and SARS-CoV-2 (EC 50 value: 2.5 µg/mL) [ 16 , 17 ]. Standardized A. annua extracts with high artemisinin content are currently being studied in an ongoing phase 2 clinical trial against COVID-19 [ 18 ].…”

“…Standardized A. annua extracts with high artemisinin content are currently being studied in an ongoing phase 2 clinical trial against COVID-19 [ 18 ]. Artesunate 2 was significantly more active than A. annua extracts against SARS-CoV-2 in vitro [ 16 ]. The excellent safety profiles of artemisinin-based drugs in humans and their ready availability for worldwide distribution at a relatively low cost render them attractive repurposing candidates for treatment of COVID-19.…”