highly pathogenic coronavirus termed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in 2019 causing coronavirus disease 2019 (COVID-19). Trials have been carried out to find drugs effective in fighting the disease, as COVID-19 is being considered a treatable disease only after we have antivirals. A clinical candidate originally developed for HIV treatment, AZVUDINE (FNC), is a promising drug in the treatment of COVID-19, being able to reduce the patient's viral load leading to cure. In this study, a randomized clinical trial was performed in moderate COVID-19 patients to evaluate the efficacy of FNC added to standard treatment, compared with placebo group added to standard treatment. RTqPCR and ddPCR were applied to estimate the viral load in samples from patients, which was performed every 48 hours throughout the treatment. Also, the clinical improvement was evaluated as well as the liver and kidney function. Notably, FNC treatment in moderate COVID-19 patients may shorten the time of nucleic acid negativity conversion versus placebo group, accelerates the elimination of the virus, decreasing the viral load significantly, especially in the first days. Due to the lack of specific antiviral drug, the pandemic is not under the control and resurfaces in different waves of infection, which cause a large cumulative expense of medical resources. Fortunately, FNC could reduce treatment time of moderate COVID-19 patients and save a lot of medical resources, making it a strong candidate for the treatment of COVID-19.