First Clinical Study Using HCV Protease Inhibitor Danoprevir to Treat Naïve and Experienced COVID-19 Patients

As coronavirus disease 2019 (COVID-19) outbreak, caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), started in China in January, 2020, repurposing approved drugs is emerging as important therapeutic options. We reported here the first clinical study using hepatitis C virus (HCV) protease inhibitor, danoprevir, to treat COVID-19 patients. Danoprevir (Ganovo®) is a potent HCV protease (NS3/4A) inhibitor (IC50 = 0.29 nM), which was approved and marketed in China since 2018 to treat chronic hepatitis C patients. Ritonavir is a CYP3A4 inhibitor to enhance plasma concentration of danoprevir while it also acts as a human immunodeficiency virus (HIV) protease inhibitor at high doses. The chymotrypsin-like protease of SARS-CoV-2 shares structure similarity with HCV and HIV proteases. In the current clinical study ( <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="clintrialgov" xlink:href="NCT04291729">NCT04291729</ext-link> ) conducted at the Nineth Hospital of Nanchang, we evaluated therapeutic effects of danoprevir, boosted by ritonavir, on treatment naïve and experienced COVID-19 patients. The data from this small-sample clinical study showed that danoprevir boosted by ritonavir is safe and well tolerated in all patients. After 4 to 12-day treatment of danoprevir boosted by ritonavir, all eleven patients enrolled, two naïve and nine experienced, were discharged from the hospital as they met all four conditions as follows: (1) normal body temperature for at least 3 days; (2) significantly improved respiratory symptoms; (3) lung imaging shows obvious absorption and recovery of acute exudative lesion; and (4) two consecutive RT-PCR negative tests of SARS-CoV-2 nucleotide acid (respiratory track sampling with interval at least one day). Our findings suggest that repurposing danoprevir for COVID-19 is a promising therapeutic option.