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Raltegravir (Isentress) Found to Be an Effective Substitute for Enfuvirtide (Fuzeon)

Raltegravir (Isentress)
Enfuvirtide (Fuzeon)

By Ronald Baker, PhD

Raltegravir (Isentress) is an HIV integrase inhibitor that is administered orally, while enfuvirtide (Fuzeon) is an HIV fusion (entry) inhibitor administered by subcutaneous injection. Enfuvirtide is FDA-approved for treatment-experienced HIV patients who exhibit continued HIV replication despite ongoing antiretroviral therapy. Raltegravir is also FDA-approved for treatment-experienced patients.

According to results of a new study published in the May 28, 2009 online issue of the Journal of Acquired Immune Deficiency Syndromes, raltegravir (Isentress) can be safely and effectively substituted for enfuvirtide in treatment-experienced patients on a stable, virologically suppressive enfuvirtide-containing regimen. A study published in 2008 in the journal AIDS found similar results.

The primary objective of the present study was to determine the safety and efficacy of changing from enfuvirtide to raltegravir in HIV patients with an undetectable viral load for at least 6 months.

Study investigators enrolled 52 eligible patients at 11 Kaiser Permanente facilities in California. Participants were at least 18 years old and were on suppressive antiretroviral medications at baseline. At the start of the study, 400 mg twice-daily oral raltegravir was substituted for twice-daily enfuvirtide injections; the other background drugs in their regimens did not change.

The primary endpoint was the percentage of participants who achieved undetectable HIV RNA (below the limit of quantification) in an intent-to-treat analysis after 24 weeks on a raltegravir-based regimen.


After 24 weeks of therapy with raltegravir, 49 patients (94.2%) had undetectable HIV viral load.

The median CD4 cell increase was 32 cells/mm3.

Questionnaires showed that patients who switched to raltegravir experienced improved satisfaction with their regimen.

Adverse events while on raltegravir were infrequent and mild.

Based on these results, the study authors concluded, "In treatment-experienced patients on a stable virologically suppressive enfuvirtide-containing regimen, raltegravir can safely be substituted for enfuvirtide."


Clearly, patients would be expected to prefer taking a twice-daily oral tablet compared with using twice-daily injections. However, the finding that raltegravir was safe and effective in addition to being an oral drug could not be assumed without conducting this or a similar study.

The potential for improvement in quality of life for patients using raltegravir versus enfuvirtide cannot be overstated. Almost all patients taking enfuvirtide experience injection site reactions. These reactions may be mild to moderate, but occasionally they are severe. Reactions on the skin where enfuvirtide is injected may include itching, swelling, redness, pain or tenderness, hardened skin, and bumps (nodules). In clinical trials, serious adverse events leading to study discontinuation occurred in 12.9% of patients (114 of 885) in the enfuvirtide arm, compared with 10.7% (12 of 112) in the control arm.

So far, there have been no serious adverse effects reported in patients using raltegravir, which was approved by the FDA in October 2007 -- the first HIV integrase inhibitor to be approved by the agency.

Department of Internal Medicine, Kaiser Permanente, Los Angeles, CA; Division of Infectious Diseases, Kaiser Permanente, Hayward, CA; Division of Infectious Diseases, Kaiser Permanente, San Francisco, CA; Division of Infectious Diseases, Kaiser Permanente, West Los Angeles, CA; Division of Research, Kaiser Permanente, Oakland, CA.

Articles on Raltegravir Posted on HIV and

Isentress Full US Prescribing Information

More Patient Information about Raltegravir

Articles on Fuzeon Posted on HIV and

Fuzeon Full U.S. Prescribing Information

More Patient Information about Fuzeon



W Towner, D Klein, HL Kerrigan, and others. Virologic Outcomes of Changing Enfuvirtide to Raltegravir in HIV-1 Patients Well Controlled on an Enfuvirtide Based Regimen: 24-Week Results of the CHEER Study Journal of Acquired Immune Deficiency Syndromes. May 28, 2009 [Epub ahead of print].

Other citation
HB Fung and Y Guo. Enfuvirtide: A Fusion Inhibitor for the Treatment of HIV Infection. Clinical Therapy 26(3): 352-378. March 2004.





























































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