The Pharmaceutical Journal
Vol 270 No 7248 p642
10 May 2003

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Benefits of fusion inhibitor against HIV maintained at 48 weeks

Data for the first HIV fusion inhibitor, enfuvirtide (Fuzeon), for HIV/AIDS shows that benefits achieved at 24 weeks have been maintained at 48 weeks.

The drug, made by Roche and Trimeris, binds to the gp41 protein on HIV's cell surface. It prevents the virus binding with the surface of T-cells and infecting them.

Used in combination therapy, the drug has been studied in patients with at least six months previous antiviral treatment and with multidrug resistance. In March, results from an American multicentre trial showed that patients taking enfuvirtide had a reduction in viral load of 1.696 log₁₀ copies/ml compared with a reduction of 0.764 log₁₀ copies/ml in the control group. Mean CD4+ count increases were 76 cells/mm³ in the enfuvirtide group compared with 32 cells/mm³ in controls.

Now, a combined analysis of this study with another phase III trial has demonstrated the sustained efficacy of the drug over 48 weeks. At baseline, patients had a median HIV level of over 5 log₁₀ copies/ml and extensive prior exposure to multiple anti-HIV drugs. At 48 weeks, patients with enfuvirtide in their antiviral regimen achieved a mean reduction in HIV levels of 1.48 log₁₀ copies/ml compared with a mean reduction of 0.63 log₁₀ copies/ml for those without the new agent.

Change from baseline for CD4 cell count was a 91 cells/mm³ increase for the enfuvirtide-containing arm and a 45 cells/mm³ increase for the control arm. The percentage achieving a reduction in HIV-1 viral load to undetectable levels (<400 copies/ml) was 30.4 per cent for patients on enfuvirtide and 12 per cent for controls. Local injection site reactions were reported by most patients treated with enfuvirtide and there were increased rates of pneumonia among patients given the fusion inhibitor.

A spokeswoman for Roche said that it was hoping for European approval for enfuvirtide within the next two to three months, with United Kingdom marketing following shortly after. The drug is difficult to produce and the companies say that demand might exceed supply. The spokeswoman explained that the UK launch would be managed so that each patient starting on the agent had a six month "safety stock" though she did not envisage supply problems in the UK.