Immune response modification: imiquimod

Imiquimod is 1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4-amine and has a molecular formula of C14H16N4. It was discovered by researchers at 3M Pharmaceuticals (St Paul, MN, USA) and is the newest in a class of drugs known as immune response modifiers. Imiquimod 5% cream has been formulated for the treatment of external genital and perianal warts (condylomata acuminata) in male and female patients. Each gram of 5% cream contains 50 mg of imiquimod. In preclinical studies, imiquimod induced the production of cytokines, the principal one for antiviral activity being interferon-alpha. Imiquimod does not induce direct antiviral activity, nor does it cause direct, non-specific cytolytic destruction. Preclinical studies suggest that its antiviral action results from in vivo cytokine-induced activation of the immune system. A double-blind, placebo-controlled study designed to evaluate this hypothesis has been previously presented. The results of the study showed that wart regression after treatment with imiquimod is strongly correlated with a decrease in virally infected cells and with increases in the expression of a spectrum of cytokines. This supports the hypothesis that stimulation of local cytokines by imiquimod leads to a reduction of human papillomavirus load and wart regression, without evidence of scarring.