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Structured Treatment Interruption Workshop

September 1999

The Foundation for AIDS and Immune Research (FAIR), in partnership with Project Inform and Treatment Action Group (TAG), co-sponsored a workshop in Boston at the end of July on structured therapy interruptions. Researchers from around the world attended to discuss preliminary data and plan future studies. People living with HIV/AIDS and representatives from industry and government also attended.

The goals of the meeting were to:

  • identify gaps in the research agenda for testing the safety and effectiveness of structured treatment interruptions which meet a minimum of three known objectives across the spectrum of HIV infection;
  • develop new study concepts and/or specific studies to fill identified gaps to coordinate a comprehensive research agenda; and
  • encourage collaboration to enhance current, planned and future studies to learn as much as possible about the risks and benefits of therapy interruption.

In general, the current goals behind structured treatment interruptions (STI) focus around three basic theories:

  • STIs may make it possible to preserve or strengthen immune responses against HIV; this is primarily being studied in people with very early infection.
  • STIs might restore a useful degree of sensitivity to anti-HIV therapies in people who are resistant to several available therapies.
  • STIs might give people who are experiencing treatment fatigue or severe side effects a break from therapy long enough to permit some degree of healing, both physically and psychologically -- if it can be done without creating long-term harm in a person's fight against HIV.

Research and interest in the area of STIs, however, should not indicate that stopping therapy, in any of these settings, is so far known to be either safe or beneficial. To the contrary, it could be found that STIs cause undue harm in some or all people. The goal of this research is to identify who (if anyone) might benefit from this approach and to shed light on potential harms of stopping therapy.

Most data presented at the Boston meeting were considered very preliminary and not ready for public distribution. Everyone carefully avoided drawing premature conclusions. Researchers agreed to present these early data only with the understanding that the forum was closed to the press. Major themes, however, came out of the workshop.

First and foremost, everyone agreed that people living with HIV and their providers should be aware that the benefit of STI has not been established in any setting and that stopping therapy involves numerous potential risks. People considering a therapy interruption are strongly encouraged to do so in the context of a planned study, where intensive monitoring of the immune system and virus is available to minimize risks.

There was at least one anecdote of a patient on effective anti-HIV therapy with full viral suppression who, upon stopping therapy, experienced increases in HIV levels and decreases in CD4+ cell counts. Upon re-starting therapy, this individual never again achieved optimal viral suppression with a potent anti-HIV therapy regimen. While no broad conclusions can be drawn from this single case, it underscores the potential risks of stopping therapy.

Secondly, workshop participants agreed that clear messages of what an STI is and is not should be clearly conveyed to people living with HIV and their health care providers. Stopping therapy for one or two days (what is commonly meant by a drug holiday) every now and then is neither strategic nor structured and will almost certainly increase the risk of developing anti-HIV drug resistance.

A Structured Treatment Interruption will include stopping therapy for some extended and defined period of time (usually at least a month or more). Depending on the goals of the STI, re-starting therapy may sometimes be done according to a specific time frame (e.g. start after one month) or be based on certain viral load or CD4+ cell count changes.

Finally, based on preliminary data from observations and studies, even if therapy interruptions prove useful in some settings, they will not be useful for all people. In every setting, observations have been made of possible harm from therapy interruptions. These include:

  • CD4+ cell count losses that might not be regained after re-initiating therapy;
  • viral load increases that might not be brought back under control;
  • the risk of resistant virus emerging and taking hold after stopping therapy; and,
  • for those with resistant virus, lack of a shift toward a predominant drug-sensitive (wild type) form of virus.

For a few people, preliminary evidence suggests improved immune responses against HIV after an STI. Among people with multi-drug resistant virus, some seem to show a shift toward drug sensitive virus after stopping therapy. For people who can't fathom a lifetime of anti-HIV therapy, at the very least some information on long-term consequences is necessary to enable informed decision-making. With all these considerations, STI research proceeds with caution.


The meeting in Boston culminated with a review of ongoing efforts and a list of recommendations by the scientists for modifying current studies, initiating specific studies and exploring existing data sets to gather more information on STIs. This would include developing an STI case definition and then applying that definition to large observational studies.

In addition to examining the experiences of people who may have already stopped therapy, the case definition can be applied and additional monitoring and data collection could take place. To achieve this goal, a Task Force is being created, including representatives from large studies around Europe and North America.

Project Inform has previously written on structured therapy interruption. For additional information, call Project Inform's National HIV/AIDS Treatment Hotline.

Back to the Project Inform Perspective September 1999 contents page.

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This article was provided by Project Inform. It is a part of the publication Project Inform Perspective. Visit Project Inform's website to find out more about their activities, publications and services.
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