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theses

Pandemics and seasonal epidemics of influenza pose a major health concern worldwide. The limitation of vaccination and the emergence of influenza virus strains that are resistant to the current antivirals, have emphasized the search for a new antiviral with novel mechanisms of action. The endonuclease activity of polymerase acidic protein (PA) has been identified as an attractive target. PAN endonuclease is a highly conserved and essential viral transcription protein, which cleaves host pre-mRNA during the cap-snatching process. The cap-snatching mechanism is a unique process of the viral transcription. There are many known PAN endonuclease inhibitors, and few of them inhibited viral reproduction in the cell. iii Our research efforts began with conducting a fragment screening campaign using 2009 pandemic H1N1 PAN. The compound 5-chloro-3-hydroxypyridin-2(1H)-one was identified as a bimetal chelating ligand at the active site of the enzyme. Several scaffolds were proposed from the hit compound including 3-hydroxypyridin-2(1H)-ones, 3-hydroxyquinolin-2(1H)-ones and aza analogous of 3-hydroxypyridin-2(1H)-ones. Although initial SAR studies on 3-hydroxypyridin-2(1H)-ones led to compound 13 with a modest antiviral activity in the cellular assay (EC50 = 11 μM), neither 3-hydroxyquinolin-2(1H)-ones nor aza analogous of 3-hydroxypyridin-2(1H)-ones displayed any ex-vivo activity. Our research again focused on the initial scaffold, 3-hydroxypyridin-2(1H)-ones. Optimization of binding interaction at the 5- and 6-positions of the pyridinone ring provided compounds having inhibitory activity that is comparative compound 13 in the enzymatic assay. Unfortunately, these compounds were not active in the cellular assay. Our research then turned to preparing noncompetitive inhibitors to validate whether irreversible or a more sustained modification of PAN could result in ex-vivo activity. In the meantime, 3-hydroxypyridin-2(1H)-one derivatives with an additional chelating moiety, which could have enhanced binding interactions with PAN, were prepared. This concept, however, turned out to be unsuccessful as we could not see any ex-vivo activity with these compounds as well. Although our various attempts at designing PAN endonuclease inhibitor with a great ex-vivo activity were unsuccessful, continued efforts are being made to find a PAN endonuclease inhibitor, which could be developed into the clinic.

ETD_7810

Ph.D.

Includes bibliographical references

by Hye Yeon Sagong

doi:10.7282/T3GF0WZ7

ETD doctoral

The author owns the copyright to this work.