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Integrase Inhibitors: First Clear Success in Human Trial

By John S. James

December 14, 2005

Merck reported that its experimental integrase inhibitor MK-0518 reduced HIV viral load 98%, in a 10-day monotherapy trial in 28 treatment-naive volunteers.1 All doses tested, from 100 to 600 mg taken as tablets twice daily, showed a highly statistically significant viral reduction (p=0.001). There were no serious adverse effects in this trial, and no one discontinued the drug due to adverse effects. Based on these results, a 48-week dose-ranging trial of MK-0518 has been started in antiretroviral-naive patients. This information was presented November 18 at the EACS (European AIDS Clinical Society) meeting in Dublin, Ireland.


HIV uses at least three enzymes to reproduce -- reverse transcriptase, protease, and integrase. These enzymes are obvious targets for designing anti-HIV drugs that block them (but enzymes are certainly not the only targets; there are many more steps in the HIV life cycle that drugs might attack). AZT and many other approved drugs block reverse transcriptase. Protease inhibitors came into use around 1996 and revolutionized AIDS treatment (although highly effective HAART combinations without protease inhibitors are also possible). Integrase inhibitors have been the hardest to develop, partly because different protease inhibitors were already used in other areas of medicine, while anti-HIV integrase inhibitors had to be developed from scratch. An earlier integrase inhibitor, S-1360, developed by Shionogi & Co. and GlaxoSmithKline, had to be discontinued because of poor bioavailability.

The new Merck trial clearly shows that an integrase inhibitor can work in people to lower HIV viral load.

For More Information

Information about this drug will change rapidly, and we do not know which Web or other information will be best. You might check first with the treatment-information sources you already use.

For general news you might try -- search for "integrase" (quotation marks not necessary). Or for more focus on AIDS-related news, try -- "integrase" returns hundreds of articles, mostly very technical, so try "MK-0518" (or any newer drug name that Merck may use in the future).


  1. Morales-Ramirez J.O., Teppler H., Kovacs C., and others, Protocol 004 Team (USA, Canada, Australia). Antiretroviral effect of MK-0518, a novel HIV-1 integrase inhibitor, in ART-naive HIV-1 infected patients. 10th European AIDS Conference/EACS, November 17-20, 2005, Dublin, Ireland [abstract LBPS1/6].

ISSN # 1052-4207

Copyright 2005 by John S. James. Permission granted for noncommercial reproduction, provided that our address and phone number are included if more than short quotations are used.

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