A guide to immunotherapy of genital warts: focus on interferon and imiquimod

Genital warts affect at least 1% of sexually active adults. Current therapies are inadequate because they are often painful, may fail to prevent recurrence and transmission of warts, and usually require either surgery or at least application by a physician. Investigation of immunotherapy for genital warts began with interferon. It has been studied in topical, intralesional, systemic and adjuvant applications. We review the major clinical trials of interferon for genital warts, and conclude that intralesional therapy with interferon-alpha or interferon-beta, with complete response rates of 36 to 63%, is the most successful route for interferon monotherapy. In choosing patients for therapy with interferon, major considerations include immune status, pregnancy and ability to return for frequent injections. Imiquimod is a new immune response enhancer that acts through stimulating host cytokine production. Interleukins-1, -2, -6, -8 and -12, interferons alpha, beta and gamma and tumour necrosis factor alpha have all been associated with the mechanism of action of imiquimod. Recently, 3 clinical trials have reported positive results using topical imiquimod to treat genital warts. Complete response rates ranged from 37 to 54% for these controlled trials of 5% imiquimod cream. Adverse effects reported include localised pruritus, erythema, erosion, burning and pain, which were rarely severe enough to cause discontinuation of the medication. Although further trials are necessary to identify the role of imiquimod in the therapy of genital warts, it appears to be an efficacious and well tolerated patient-controlled measure for wart therapy.