The discovery of antiviral compounds targeting adenovirus and herpes simplex virus : assessment of synthetic compounds and natural products

Abstract: There is a need for new antiviral drugs. Especially for the treatment of adenovirus infections, since no approved anti-adenoviral drugs are available. Adenovirus infections in healthy persons are most often associated with respiratory disease, diarrhea and infections of the eye. These infections can be severe, but are most often self-limiting. However, in immunocompromised patients, adenovirus infections are associated with morbidity and high mortality rates. These patients are mainly stem cell or bone marrow transplantation recipients, however solid organ transplantation recipients or AIDS patients may be at risk as well. In addition, children are at higher risk to develop disseminated disease.Due to the need for effective anti-adenoviral drugs, we have developed a cell based screening assay, using a replication-competent GFP expressing adenovirus vector based on adenovirus type 11 (RCAd11GFP). This assay facilitates the screening of chemical libraries for antiviral activity. Using this assay, we have screened 9800 small molecules for anti-adenoviral activity with low toxicity. One compound, designated Benzavir-1, was identified with activity against representative types of all adenovirus species. In addition, Benzavir-1 was more potent than cidofovir, which is the antiviral drug used for treatment of adenovirus disease. By structure-activity relationships analysis (SAR), the potency of Benzavir-1 was improved. Hence, the improved compound is designated Benzavir-2. To assess the antiviral specificity, the activity of Benzavir-1 and -2 on both types of herpes simplex virus (HSV) was evaluated. Benzavir-2 displayed better efficacy than Benzavir-1 and had an activity comparable to acyclovir, which is the original antiviral drug used for therapy of herpes virus infections. In addition, Benzavir-2 was active against acyclovir-resistant clinical isolates of both HSV types.To expand our search for compounds with antiviral activity, we turned to the natural products. An ethyl acetate extract library was established, with extracts derived from actinobacteria isolated from sediments of the Arctic Sea. Using our screening assay, several extracts with anti-adenoviral activity and low toxicity were identified. By activity-guided fractionation of the extracts, the active compounds could be isolated. However, several compounds had previously been characterized with antiviral activity. Nonetheless, one compound had uncharacterized antiviral activity and this compound was identified as a butenolide. Additional butenolide analogues were found and we proposed a biosynthetic pathway for the production of these compounds. The antiviral activity was characterized and substantial differences in their toxic potential were observed. One of the most potent butenolide analogues had minimal toxicity and is an attractive starting point for further optimization of the anti-adenoviral activity.This thesis describes the discovery of novel antiviral compounds that targets adenovirus and HSV infections, with the emphasis on adenovirus infections. The discoveries in this thesis may lead to the development of new antiviral drugs for clinical use. 

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