A review of the applications of imiquimod: a novel immune response modifier

Imiquimod (1-(2-methylpropyl)-1 H-imidazo[4,5-c]quinolin-4-amine) and its analogues are a class of non-nucleoside imidazoquinolinamines (hetero-cyclic amine) that activate the immune system through localised induction of cytokines, such as IFN-alpha, -beta, and a number of endogenous interleukins. The exact mechanism of its actions are still unexplored, although when tested in a number of cell culture systems, imiquimod demonstrated no inherent antiviral or antiproliferative activity in vitro, whereas, due to its reported ability to produce onsite stimulation and secretion of cytokines in various in vivo studies, such types of immune response modifiers have been shown to cause diverse biological functions, involving immunoregulatory, antiviral, antiproliferative and antitumour activities. These data support a rational justification to consider imiquimod as an innovative topical agent to treat various cutaneous diseases. Since its synthesis in 1980,several studies using animal models and human subjects have been reported substantiating its usefulness as a treatment option for various skin disorders such as genital warts, genital herpes, molluscum contagiosum, basal cell carcinoma and psoriasis. Imiquimod is insoluble in water but in most of the clinical studies its incorporation from 1 - 5% by weight in an oil-into-water cream emulsion has been reported as being well-tolerated with mild-to-moderate drug-related side effects, such as itching, burning sensation, pain, erythema, erosion and oedema. As a potent immune response modifier and an agent stimulating cell-mediated immune responses, imiquimod appears to be a promising drug to treat many skin disorders, infections and neoplasms.