Search, Identification, and Design of Effective Antiviral Drugs Against Pandemic Human Coronaviruses

Discovery of natural catechol derivatives as covalent SARS-CoV-2 3CLpro inhibitors

The COVID-19 pandemic caused by SARS-CoV-2 continues to pose a threat to public health, and extensive research by scientists worldwide has also prompted the development of antiviral therapies. The 3C-like protease (3CLpro) is critical for SARS-CoV-2 replication and acts as an effective target for drug development. To date, numerous of natural products have been reported to exhibit inhibitory effects on 3CLpro, which encourages us to identify other novel inhibitors and elucidate their mechanism of action. In this study, we first screened an in-house compound library of 101 natural products using FRET assay, and found that oleuropein showed good inhibitory activity against SARS CoV-2 3CLpro with an IC50 value of 4.18 μM. Further studies revealed that the catechol core is essential for activity and can covalently bind to SARS-CoV-2 3CLpro. Among other 45 catechol derivatives, wedelolactone, capsazepine and brazilin showed better SARS-CoV-2 3CLpro inhibitory activities with IC50 values of 1.35 μM, 1.95 μM and 1.18 μM, respectively. These catechol derivatives were verified to be irreversible covalent inhibitors by time-dependent experiments, enzymatic kinetic studies, dilution and dialysis assays. It also exhibited good selectivity towards different cysteine proteases (SARS-CoV-2 PLpro, cathepsin B and cathepsin L). Subsequently, the binding affinity between brazilin and SARS-CoV-2 3CLpro was determined by SPR assay with KD value of 0.80 μM. Molecular dynamic (MD) simulations study showed the binding mode of brazilin in the target protein. In particular, brazilin displayed good anti-SARS-CoV-2 activity in A549-hACE2-TMPRSS2 cells with EC50 values of 7.85 ± 0.20 μM and 5.24 ± 0.21 μM for full time and post-infection treatments, respectively. This study provides a promising lead compound for the development of novel anti-SARS-CoV-2 drugs.

Preventive and therapeutic benefits of nelfinavir in rhesus macaques and human beings infected with SARS-CoV-2

Effective drugs with broad spectrum safety profile to all people are highly expected to combat COVID-19 caused by SARS-CoV-2. Here we report that nelfinavir, an FDA approved drug for the treatment of HIV infection, is effective against SARS-CoV-2 and COVID-19. Preincubation of nelfinavir could inhibit the activity of the main protease of the SARS-CoV-2 (IC50 = 8.26 μM), while its antiviral activity in Vero E6 cells against a clinical isolate of SARS-CoV-2 was determined to be 2.93 μM (EC50). In comparison with vehicle-treated animals, rhesus macaque prophylactically treated with nelfinavir had significantly lower temperature and significantly reduced virus loads in the nasal and anal swabs of the animals. At necropsy, nelfinavir-treated animals had a significant reduction of the viral replication in the lungs by nearly three orders of magnitude. A prospective clinic study with 37 enrolled treatment-naive patients at Shanghai Public Health Clinical Center, which were randomized (1:1) to nelfinavir and control groups, showed that the nelfinavir treatment could shorten the duration of viral shedding by 5.5 days (9.0 vs. 14.5 days, P = 0.055) and the duration of fever time by 3.8 days (2.8 vs. 6.6 days, P = 0.014) in mild/moderate COVID-19 patients. The antiviral efficiency and clinical benefits in rhesus macaque model and in COVID-19 patients, together with its well-established good safety profile in almost all ages and during pregnancy, indicated that nelfinavir is a highly promising medication with the potential of preventative effect for the treatment of COVID-19.

Curing Cats with Feline Infectious Peritonitis with an Oral Multi-Component Drug Containing GS-441524

Feline infectious peritonitis (FIP) caused by feline coronavirus (FCoV) is a common dis-ease in cats, fatal if untreated, and no effective treatment is currently legally available. The aim of this study was to evaluate efficacy and toxicity of the multi-component drug Xraphconn^® in vitro and as oral treatment in cats with spontaneous FIP by examining survival rate, development of clinical and laboratory parameters, viral loads, anti-FCoV antibodies, and adverse effects. Mass spectrometry and nuclear magnetic resonance identified GS-441524 as an active component of Xraphconn^®. Eighteen cats with FIP were prospectively followed up while being treated orally for 84 days. Values of key parameters on each examination day were compared to values before treatment initiation using linear mixed-effect models. Xraphconn^® displayed high virucidal activity in cell culture. All cats recovered with dramatic improvement of clinical and laboratory parameters and massive reduction in viral loads within the first few days of treatment without serious adverse effects. Oral treatment with Xraphconn^® containing GS-441524 was highly effective for FIP without causing serious adverse effects. This drug is an excellent option for the oral treatment of FIP and should be trialed as potential effective treatment option for other severe coronavirus-associated diseases across species.