The efficacy of Zafirlukast as a SARS-CoV-2 helicase inhibitor in adult patients with moderate COVID-19 Pneumonia (pilot randomized clinical trial).

OBJECTIVE: To assess the efficacy of Zafirlukast as a SARS-CoV-2 Helicase Inhibitor in adult patients with moderate COVID-19 symptoms (hospitalized patients with COVID-19 pneumonia who were not admitted to an intensive care unit). METHODS: We conducted a randomized, double blind, placebo-controlled, pilot trial with adult patients with moderate COVID-19 pneumonia. The sample was randomized to Zafirlukast 10 mg BD for 10 days plus standard care vs placebo plus standard care. The primary outcome was the complete resolution of all symptoms. The secondary outcomes were the duration of oxygen therapy, and length of hospital stay (LOS). RESULTS: In total, 40 patients were randomized (20 to Zafirlukast and 20 to the control). The time to the resolution of clinical symptoms in both groups was not significantly different. Regarding the fever, 0.3 days [95 % CI, - 1.19, 0.69], p = 0.76, for shortness of breath, the difference was 0.4 days [95 % CI, - 2.67, 3.46], p = 0.68, for cough the difference was 0.2 days [95 % CI, - 1.45, 1.95], p = 0.98, for sputum the difference was 0.5 days [95 % CI, - 0.75, 1.85], p = 0.09, for vomiting the difference was 0.1 days [95 % CI, - 0.50, 0.30], p = 0.93, for fatigue the difference was 0.3 days [95 % CI, - 4.32, 3.62], p = 0.64. The LOS per day for the two groups was not significantly different, 1.1 days [95 % CI,- 2.03, 4.28], p = 0.94, nor was the duration of oxygen therapy per days, 1.3 days [95 % CI, - 1.79, 4.49], p = 0.49. Regarding the 7 category ordinary scale, there was no significant difference between the two groups at day 7 (p-value = 0.62), day 14 (p-value = 0.60) and day 28 (p-value = 0.48). CONCLUSION: Among adult patients hospitalized with COVID-19 pneumonia, the treatment with Zafirlukast, compared to placebo, did not significantly improve symptoms resolution.

Discovery of Zafirlukast as a novel SARS-CoV-2 helicase inhibitor using in silico modelling and a FRET-based assay.

The coronavirus helicase is an essential enzyme required for viral replication/transcription pathways. Structural studies revealed a sulphate moiety that interacts with key residues within the nucleotide-binding site of the helicase. Compounds with a sulphoxide or a sulphone moiety could interfere with these interactions and consequently inhibit the enzyme. The molecular operating environment (MOE) was used to dock 189 sulphoxide and sulphone-containing FDA-approved compounds to the nucleotide-binding site. Zafirlukast, a leukotriene receptor antagonist used to treat chronic asthma, achieved the lowest docking score at -8.75 kcals/mol. The inhibitory effect of the compounds on the SARS-CoV-2 helicase dsDNA unwinding activity was tested by a FRET-based assay. Zafirlukast was the only compound to inhibit the enzyme (IC50 = 16.3 µM). The treatment of Vero E6 cells with 25 µM zafirlukast prior to SARS-CoV-2 infection decreased the cytopathic effects of SARS-CoV-2 significantly. These results suggest that zafirlukast alleviates SARS-CoV-2 pathogenicity by inhibiting the viral helicase and impairing the viral replication/transcription pathway. Zafirlukast could be clinically developed as a new antiviral treatment for SARS-CoV-2 and other coronavirus diseases. This discovery is based on molecular modelling, in vitro inhibition of the SARS-CoV helicase activity and cell-based SARS-CoV-2 viral replication.