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More Monotherapy Data Underscore Its Potential to Harm

By Alan McCord

February 21, 2009

In a poster presentation at CROI 2009 in Montreal, Canada, the MOST study showed poor results using Kaletra alone (called monotherapy) to control HIV levels. There was such a high rate of early failure (viral breakthrough) that the study was stopped early due to safety concerns.

This randomized study was designed to evaluate how well Kaletra alone suppressed HIV in the cerebral spinal fluid and genital tract. Safety and effectiveness were evaluated as well as identifying what (if any) markers predicted failure. After 48 weeks on three-drug therapy, people were offered Kaletra alone. The failure protocol was set at 6 or more volunteers failing on Kaletra alone out of the first 30 enrolled.

In September 2008, the protocol committee stopped the study due to 6 volunteers showing detectable HIV levels in blood. By that time, 60 had been enrolled and 29 of them were taking the single-drug therapy. People who experienced viral breakthrough while on Kaletra alone had generally lower nadir (lowest ever) CD4 counts (below 100). Also, several had symptoms of problems with their central nervous systems.

As noted in our coverage from the 2008 ICAAC on two other similar studies (, Project Inform believes these types of studies should no longer be attempted as these monotherapy regimens continue to show dramatic virologic failures. Not only is this a poor use of resources that could be better spent on more pressing questions, the strategy puts study participants at great risk for treatment failure, which may unduly complicate their future regimens.

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