Warning on two specific 3-drug regimens: Viread + Videx + either Sustiva or Viramune.

On November 12 the U.S. Food and Drug Administration's AIDS listserve noted a Dear Doctor letter from Bristol-Myers Squibb, warning that the two particular three-drug combinations noted above had shown a high rate of virologic failure in treatment-naive patients with high viral loads (about half of those patients failed the treatment). The problem seems to be specific to these regimens, as Sustiva has worked with Viread-based regimens, and with Videx-based regimens, in different trials.

The FDA email is available on its archive, http://www.fda.gov/oashi/aids/listserve/listserve2004.html (you need to scroll down). And this page has the full BMS Dear Doctor letter attached.

Comment

There are now several antiretroviral regimens that failed to control the virus, and were not predicted to tail on the basis of clinical trials, physicians' experience, and known drug interactions. The leading theory seems to be that the bad combinations have a genetic barrier against the virus that is too low. If so, then it may be possible to better predict such failures from existing resistance data--and perhaps to improve other regimens as well, by avoiding possible weaknesses that are less serious but still important. Has anybody yet brought this information together into a model that works?