FUZEON (enfuvirtide) with an active, boosted protease inhibitor (PI) may make undetectable possible for more treatment-experienced patients. This treatment strategy is confirmed by DHHS Guidelines: "Patients who received more active drugs (e.g., an active ritonavir-boosted PI and ENF) had a better and more prolonged virologic response than those with fewer active agents in the regimen."¹

Delayed Use of FUZEON May Influence Subsequent Response

The TORO trials were randomized, open-label, multinational studies of 997 triple-class-experienced patients with documented resistance to at least one member in each of the NRTI, NNRTI and PI classes. The trials compared treatment with FUZEON plus a background regimen and a background regimen alone. Patients receiving an optimized background treatment regimen were allowed to switch to a FUZEON-based regimen in the event of virologic failure.^5-7

Upon failing an initial regimen without FUZEON, patients who switched to an optimized regimen with FUZEON showed an attenuated improvement in viral load relative to patients who received a FUZEON-based regimen initially. It is possible that the attenuated response in the switch group was influenced by poorer prognoses at baseline and/or the loss of active ARVs at virologic failure.⁵

The design of the TORO trials allowed patients receiving an optimized background treatment regimen to switch to a FUZEON-based regimen in the event of virologic failure.⁵



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1. Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents. Panel on Clinical Practices for Treatment of HIV Infection, United States Dept of Health and Human Services; October 10, 2006.
2. Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents. Panel on Clinical Practices for Treatment of HIV Infection, United States Dept of Health and Human Services; March 23, 2004.
3. Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents. Panel on Clinical Practices for Treatment of HIV Infection, United States Dept of Health and Human Services; April 7, 2005.
4. Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents. Panel on Clinical Practices for Treatment of HIV Infection, United States Dept of Health and Human Services; May 4, 2006.
5. Arasteh K, Lazzarin A, Clotet B, et al. TORO: 96 week virological and immunological response and safety evaluation of enfuvirtide with an optimized background regimen. Program and abstracts from the XV International AIDS Conference. July 11-16, 2004; Bangkok, Thailand. Poster MoOrB1058.
6. Nelson M, Arasteh K, Clotet B, et al. Durable efficacy of enfuvirtide over 48 weeks in heavily treatment-experienced HIV-1-infected patients in the T-20 versus optimized background regimen only 1 and 2 clinical trials. J Acquir Immune Defic Syndr. 2005;40(4):404-412.
7. Trottier B, Walmsley S, Reynes J, et al. Safety of enfuvirtide in combination with an optimized background of antiretrovirals in treatment-experienced HIV-1-infected adults over 48 weeks. J Acquir Immune Defic Syndr. 2005;40(4):413-421.