Injection site reactions with the HIV-1 fusion inhibitor enfuvirtide.

Background: Enfuvirtide is the first of a new class of antiretroviral agents for the treatment of HIV-1 infection, called the fusion inhibitors. The most common type of adverse event associated with enfuvirtide treatment is injection site reactions, occurring in up to 98% of patients. Many of these lesions are symptomatic. This study investigated injection site reactions occurring in 7 patients with HIV infection who were receiving enfuvirtide.

Observations: All biopsy specimens revealed an inflammatory response consistent with a localized hypersensitivity reaction; this was regardless of type of clinical lesion and included the patient with no clinical reaction. The pattern of inflammation resembled that of granuloma annulare and the recently described interstitial granulomatous drug reaction. Immunoperoxidase staining indicated that the inflammatory and collagen changes were greatest in areas where enfuvirtide was deposited.

Conclusions: The pathologic changes and clinicopathologic correlations associated with injection site reactions in human enfuvirtide recipients have been described for the first time. This information also provides valuable insights into unusual pathogenic response to foreign antigens for patients with HIV.