<qa>  What is the first drug to be developed?Over the last few years, an unprecedented decrease in the mortality and morbidity associated with AIDS has been achieved attributed to the use of highly active antiretroviral therapy HAART which consists of three different classes of drugs: Nucleoside reverse transcriptase inhibitors NRTIs, protease inhibitors PIs, and non-nucleoside reverse transcriptase inhibitors NNRTIs. However, the durability of viral suppression is often limited by treatment with combinations of non-fully suppressive antiretroviral agents. Heavily pretreated patients often possess multiple mutations of the reverse transcriptase and protease genes resulting in multi-drug resistance. Thus, a pharmacological agent effective at an alternate point in the virus replication cycle would make a valuable addition to the anti-HIV armamentarium. T-20, enfuvirtide, is the first drug to be developed which specifically inhibits the function of the gp41 transmembrane glycoprotein of HIV-1. The objective of this study is to assess the safety and tolerability of Fuzeon Enfuvirtide in patients who are limited by the current commercially available antiretroviral agents or agents available via early access or compassionate use programs as per the judgment of the investigator or patients with advanced disease and most in need of therapy. This study is a multicenter, open-label, single-arm, safety study. Each patient will receive enfuvirtide 90 mg deliverable dose via subcutaneous injection twice daily with food, in combination additional antiretroviral agents. Subjects will continue to receive enfuvirtide until 12 weeks after commercial availability of enfuvirtide in the United States. Laboratory testing, CD4lymphocyte counts, HIV-1 viral loads will be monitored on a regular and continual basis. The main outcome measures are ones of safety and tolerability: serious adverse events including all deaths, serious AIDS defining events, and discontinuations for any reason, injection reconstitution fatigue. 