Imiquimod

Overview
Imiquimod (INN, marketed by 3M under the trade name Aldara) is a prescription medication that acts as an immune response modifier.

Uses
Imiquimod is a patient-applied cream used to treat certain diseases of the skin, including skin cancer (basal cell carcinoma, Bowen's disease, superficial squamous cell carcinoma, some superfical malignant melanomas and actinic keratosis) as well as genital warts (Condylomata Acuminata). It has also been tested for treatment of Molluscum contagiosum. It causes interferon production which triggers the patient's immune response against these tumors.

It is also used pre-operatively to shrink basal cell cancer and melanoma in situ (especially Lentigo Maligna) before Mohs surgery.

Side effects include redness and irritation of the skin during treatment.

History
The original FDA approval was on February 27, 1997, FDA Application No. (NDA) 020723, by Graceway.

Since then, the label has been revised many times. Adverse side effects have been reported, in some cases serious and systemic. Some patients have been suffering from severe auto-immune or neuro-immune effects for years.

Mechanism of action
The exact mode in which imiquimod and its analogs activate the immune system is not yet known. Nevertheless, it is known that Imiquimod activates immune cells by ligating the toll-like receptor 7 (TLR7), commonly involved in pathogen recognition, on the cell surface. Cells activated by imiquimod via TLR-7 secrete cytokines (primarily interferon-α (IFN-α), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α)). There is evidence that imiquimod, when applied to skin, can lead to the activation of Langerhans cells, which subsequently migrates to local lymph nodes to activate the adaptive immune system. Other cell types activated by imiquimod include natural killer cells, macrophages and B-lymphocytes.