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Document<br />

XVI. Perspective<br />

Page 70<br />

Substantial progress has been made in understanding the structure and function of HIV-1 RT and in the<br />

development of anti-HIV-1 inhibitors. However, the genetic flexibility of HIV-1 will continue to make<br />

development of a truly effective antiviral therapy for AIDS an exceptionally difficult task. We are<br />

beginning to understand how to circumvent drug resistance. The accumulated evidence has shown that<br />

the ability of the virus to develop drug resistance is limited and that the drug-resistant viral variants are<br />

less efficient than the wild-type virus. If the selection pressure provided <strong>by</strong> antiviral drugs makes the<br />

virus pay a sufficiently high price, then the viral load can be decreased and there will be a measurable<br />

clinical benefit. Based on a better understanding of the structure-function relationships of HIV-1 RT, we<br />

are now coming to grips with the mechanisms of polymerization, drug inhibition, and drug resistance.<br />

This information should make it possible to develop new or improved HIV-1 RT inhibitors that have<br />

different properties and provoke different patterns of drug-resistance mutations. Though it is likely that<br />

there will be no single drug which would be effective against all HIV-1 variants, we have reasons to<br />

believe that new or improved drugs or, more likely, new drug combinations, will be designed that are<br />

broadly effective against all of the HIV-1 variants that can grow efficiently. Detailed analysis of the<br />

conformational changes among the various HIV-1 RT structures may reveal additional sites (in addition<br />

to the currently known NRTI- and NNRTI-binding sites) for binding new inhibitors able to interfere<br />

with the polymerization and/or the flexibility of the enzyme required for its activity. The considerable<br />

physical and genetic flexibility of HIV-1 RT suggests that more effective anti-RT drugs should be<br />

designed to target the conserved portions of HIV-1 RT that the virus cannot easily afford to change.<br />

Such conserved elements can be identified <strong>by</strong> comparing the sequences of RTs from different<br />

retroviruses; the functions and relative importance of these conserved elements can be determined <strong>by</strong><br />

mutagenesis and biochemical and structural analyses. It is our hope that application of structure-<strong>based</strong><br />

drug design strategies may aid in the development of novel HIV-1 RT inhibitors for a more effective<br />

treatment of HIV-1 infection.<br />

Acknowledgments<br />

We thank the other members of the Arnold and Hughes laboratories and our collaborators for their<br />

helpful discussions and assistance, including Koen Andries, Gail Ferstandig Arnold, Paul Boyer, Arthur<br />

Clark, Jr., Paul Janssen, Jörg-Peter Kleim, Luc Koymans, Tack Kuntz, Karen Lentz, Chris Michejda,<br />

Henri Moereels, Manfred Roesner, Marilyn Kroeger Smith, Rick Smith, Jr., and<br />

http://legacy.netlibrary.com/nlreader/nlReader.dll?bookid=12640&filename=Page_70.html [4/5/2004 4:50:51 PM]

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