active background

moving on, it might also be a good time to consider this...

remember the old boner about 'no phiii failures' for hiv drugs... well here's a recent one/two...

http://www.tradingmarkets.com/news/stock-alert/mrk_merck-amp-co-potential-remains-for-hiv-drug-despite-trial-disappointment-721438.html

and note the problem was they were trying to demonstrate superiority over an existing active background, but became confounded by the good activity of recent additional drugs...

"Participants were treatment experienced with documented resistance to at least two antiretroviral drug classes. While data from the study are not yet available, Datamonitor speculates that vicriviroc may have failed to achieve superiority due the inclusion of two to three active drugs in the background regimen. Efficacy rates as high as 90% have been observed in this population with the combination of currently available options, such as Merck's Isentress (raltegravir) or Tibotec/Johnson & Johnson's Prezista (darunavir) and Intelence (etravirine). Unsurprisingly, this leaves little room for newer agents such as vicriviroc to show any additional benefits."

much less spectacular phii results than atc thou...
http://www.hivandhepatitis.com/2007icr/ias/docs/072707_c.html
http://www.merck.com/newsroom/news-release-archive/schering-plough-news-archive/all/releaseid=1331338.html

I wonder if all this might have some implications for the design of the next phiii/iv atc trial and an aim of demonstrating non-inferiority rather than superiority...