BPR3P0128, a non-nucleoside RNA-dependent RNA polymerase inhibitor, inhibits SARS-CoV-2 variants of concern and exerts synergistic antiviral activity in combination with remdesivir.

Viral RNA-dependent RNA polymerase (RdRp), a highly conserved molecule in RNA viruses, has recently emerged as a promising drug target for broad-acting inhibitors. Through a Vero E6-based anti-cytopathic effect assay, we found that BPR3P0128, which incorporates a quinoline core similar to hydroxychloroquine, outperformed the adenosine analog remdesivir in inhibiting RdRp activity (EC50 = 0.66 µM and 3 µM, respectively). BPR3P0128 demonstrated broad-spectrum activity against various severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern. When introduced after viral adsorption, BPR3P0128 significantly decreased SARS-CoV-2 replication; however, it did not affect the early entry stage, as evidenced by a time-of-drug-addition assay. This suggests that BPR3P0128's primary action takes place during viral replication. We also found that BPR3P0128 effectively reduced the expression of proinflammatory cytokines in human lung epithelial Calu-3 cells infected with SARS-CoV-2. Molecular docking analysis showed that BPR3P0128 targets the RdRp channel, inhibiting substrate entry, which implies it operates differently-but complementary-with remdesivir. Utilizing an optimized cell-based minigenome RdRp reporter assay, we confirmed that BPR3P0128 exhibited potent inhibitory activity. However, an enzyme-based RdRp assay employing purified recombinant nsp12/nsp7/nsp8 failed to corroborate this inhibitory activity. This suggests that BPR3P0128 may inhibit activity by targeting host-related RdRp-associated factors. Moreover, we discovered that a combination of BPR3P0128 and remdesivir had a synergistic effect-a result likely due to both drugs interacting with separate domains of the RdRp. This novel synergy between the two drugs reinforces the potential clinical value of the BPR3P0128-remdesivir combination in combating various SARS-CoV-2 variants of concern.

Ovatodiolide inhibits SARS-CoV-2 replication and ameliorates pulmonary fibrosis through suppression of the TGF-ß/TßRs signaling pathway.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection continues to pose threats to public health. The clinical manifestations of lung pathology in COVID-19 patients include sustained inflammation and pulmonary fibrosis. The macrocyclic diterpenoid ovatodiolide (OVA) has been reported to have anti-inflammatory, anti-cancer, anti-allergic, and analgesic activities. Here, we investigated the pharmacological mechanism of OVA in suppressing SARS-CoV-2 infection and pulmonary fibrosis in vitro and in vivo. Our results revealed that OVA was an effective SARS-CoV-2 3CLpro inhibitor and showed remarkable inhibitory activity against SARS-CoV-2 infection. On the other hand, OVA ameliorated pulmonary fibrosis in bleomycin (BLM)-induced mice, reducing inflammatory cell infiltration and collagen deposition in the lung. OVA decreased the levels of pulmonary hydroxyproline and myeloperoxidase, as well as lung and serum TNF-ɑ, IL-1ß, IL-6, and TGF-ß in BLM-induced pulmonary fibrotic mice. Meanwhile, OVA reduced the migration and fibroblast-to-myofibroblast conversion of TGF-ß1-induced fibrotic human lung fibroblasts. Consistently, OVA downregulated TGF-ß/TßRs signaling. In computational analysis, OVA resembles the chemical structures of the kinase inhibitors TßRI and TßRII and was shown to interact with the key pharmacophores and putative ATP-binding domains of TßRI and TßRII, showing the potential of OVA as an inhibitor of TßRI and TßRII kinase. In conclusion, the dual function of OVA highlights its potential for not only fighting SARS-CoV-2 infection but also managing injury-induced pulmonary fibrosis.