Since June 2007, raltegravir has been available in Switzerland within a named patient program for patients who have virologic failure, triple class experience and resistance, and no other treatment options. This proposal has been designed to evaluate efficacy and safety data among patients who receive raltegravir within the routine clinical practice in Switzerland and who participate in the Swiss HIV Cohort Study. This is a combined retrospective analysis of patients who already received raltegravir and a prospective part of patients who enter the named patient program and will be followed up in a standardized way. In the prospective part, patients will also be able to receive raltegravir in case of intolerance to their current medication with virologic suppression.

The analysis will primarily use descriptive statistics. In addition, we will assess the duration of virologic response and focus on predictors of HIV RNA suppression during a follow-up of at least 6 months. In the prospective part, we will assess trough plasma levels of raltegravir and other antiretrovirals. In patients who will develop virologic failure, genotypic and phenotypic resistance to raltegravir (and other antiretrovirals) will be performed to characterize the evolution of resistance during the raltegravir-containing regimen.

Inclusion Criteria:

• all patients treated with Raltegravir within the Swiss HIV Cohort Study

Exclusion Criteria:

• drop out of the Swiss HIV Cohort study

The Swiss HIV Cohort study is a nationwide observational cohort existing for more than 20 years and is representative of the HIV-infected population in Switzerland (approx. 50% of HIV-infected patients in Switzerland, participate in this study). All patients must sign an informed consent to participate in this study.

The study population enrolled in the current "Raltegravir in the SHCS" study, is a subgroup of patients, that has to go on Raltegravir within the Swiss HIV Cohort study.