Tucaresol: A Clinical Stage Oral Candidate Drug with Two Distinct Antiviral Mechanisms

Globally, approximately 39 million people are living with Human Immunodeficiency Virus, HIV, arising from approximately 86 million infections since this epidemic began in 1981. However, the number of HIV infections is unevenly distributed with two thirds of global infections confined to Sub-Saharan Africa. Due to viral drug resistance, the most effective treatment requires a triple drug combination thereby adding to the complexity and cost of therapy. As such, many people living with HIV or at risk of infection do not have access to prevention or treatment of this potentially fatal disease. There is no cure for HIV [1]. Tucaresol is an orally active clinical stage drug which functions as a host targeted antiviral agent by protection or reconstitution of CD4+ T helper immune cells. We report herein that Tucaresol also displays in-vitro activity against HIV in infected human peripheral blood mononuclear cells. Although this in-vitro antiviral activity is not potent, the excellent safety profile and bioavailability of Tucaresol, along with its low Molecular Weight, support attainment of relevant drug concentrations in man to achieve significant in-vivo activity. This is demonstrated by previously reported stabilization of viremia in a prior proof of concept phase 1b/2a HIV clinical trial [2]. It is possible that the significant in-vivo activity of Tucaresol arises from synergy between co-stimulation of CD4+ T helper cells and the direct activity against virally infected cells. A pan in-vitro viral screen of Tucaresol further revealed a weak, direct antiviral activity against human herpes virus 6B, human papillomavirus 11, measles virus and hepatitis B virus.