GSK983: A novel compound with broad-spectrum antiviral activity

GSK983, a novel tetrahydrocarbazole, inhibits the replication of a variety of unrelated viruses in vitro with EC 50 values of 5–20 nM. Both replication of the adenovirus Ad-5 and the polyoma virus SV-40, and episomal maintenance of human papillomaviruses (HPV) and Epstein-Barr virus (EBV) are susceptible to GSK983. The compound does not inhibit all viruses; herpes simplex virus (HSV-1), human immunodeficiency virus (HIV), and lytic replication of EBV were not susceptible at concentrations below 1 μM. GSK983 does inhibit the growth of cell lines immortalized by HTLV-1, EBV, HPV, SV40 and Ad-5, with EC 50 values in the range of 10–40 nM. Depending on the cell line, the compound induces either apoptosis or cytostasis at concentrations over 20 nM. GSK983 also inhibits cell lines immortalized by non-viral mechanisms, but has little effect on primary cells. The CC 50 values for keratinocytes, fibroblasts, lymphocytes, endothelial, and bone marrow progenitor cells are all above 10 μM. The pattern of inhibition, which includes diverse viruses as well as growth of immortalized cells of varied origins, suggests the target is a host cell protein, rather than a viral protein. Preliminary mechanism studies indicate that GSK983 acts by inducing a subset of interferon-stimulated genes.