Structured treatment interruptions

May 2008      View PDF      En español

Using an STI before starting third line therapy

When a person tries to construct a new regimen which may contain drugs that had failed before, the regimen is often referred to as third line or salvage therapy. Because salvage also means “to save”, some people call salvage regimens rescue therapy. In this publication, third line therapy describes a new regimen that typically contains four or more HIV drugs, some of which a person may be resistant to.

The theory behind using STIs in this way is to increase HIV’s response to treatments that it had become resistant to. Studies conducted in the early days of HIV therapy found that when a person goes off therapy to which HIV has become resistant, the new virus will rapidly revert to what is called wild-type. Wild-type HIV is the strain that reproduces most easily and responds to HIV therapy. The earlier studies found that when wild-type HIV takes over as the dominant form in the body, a drug that had stopped working could sometimes regain some of its potency.

For this reason, several studies looked at how STIs impact third line therapy. A Barcelona study found that a three-month STI before starting third line therapy did not provide any advantage. The French gigaHAART study, using a shorter interruption, showed that people taking an STI had larger reductions in HIV when they started their next regimen than those who started their next regimen without an STI.

San Francisco researchers conducted a similar study using a four-month STI before starting salvage therapy to others who started their third line regimens immediately. In contrast to the French study, these results showed no benefits in viral response to treatment in those who were on the STI. In fact, people were more likely to develop an OI or die.