Imiquimod, sold under the brand name Aldara among others, is a medication that acts as an immune response modifier that is used to treat genital warts, superficial basal cell carcinoma, and actinic keratosis. Scientists at 3M's pharmaceuticals division discovered the drug and 3M obtained the first FDA approval in 1997. As of 2015, imiquimod is generic and is available worldwide under many brands. Medical uses Imiquimod is a patient-applied cream prescribed to treat genital warts, Bowens disease (squamous cell carcinoma in situ), and, secondary to surgery, for basal cell carcinoma, as well as actinic keratosis. Imiquimod 5% cream is indicated for the topical treatment of: external genital and perianal warts (condylomata acuminata) in adults; small superficial basal-cell carcinomas (sBCCs) in adults; clinically typical, non-hyperkeratotic, non-hypertrophic actinic keratoses (AKs) on the face or scalp in immunocompetent adults when size or number of lesions limit the efficacy and / or acceptability of cryotherapy and other topical treatment options are contraindicated or less appropriate. Imiquimod 3.75% cream is indicated for the topical treatment of clinically typical, non-hyperkeratotic, non-hypertrophic, visible or palpable actinic keratosis of the full face or balding scalp in immunocompetent adults when other topical treatment options are contraindicated or less appropriate. Side effects Side effects include local inflammatory reactions, such as blisters, a burning sensation, skin redness, dry skin, itching, skin breakdown, skin crusting or scabbing, skin drainage, skin flaking or scaling, skin ulceration, sores, swelling, as well as systemic reactions, such as fever, "flu-like" symptoms, headache, and tiredness. People who have had an organ transplant and are taking immune-suppressing drugs should not use imiquimod. Mechanism of action Imiquimod yields profound antitumoral activity by acting on several immunological levels synergistically. Imiquimod stimulates the innate immune system by activating toll-like receptor 7 (TLR7), commonly involved in pathogen recognition. 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 migrate to local lymph nodes to activate the adaptive immune system. Other cell types activated by imiquimod include natural killer cells, macrophages and B-lymphocytes. Imiquimod exerts its effect by increasing levels of the opioid growth factor receptor (OGFr). In experiments, blocking OGFr function with siRNA technology resulted in loss of any antiproliferative effect of imiquimod. History Scientists at 3M's pharmaceutical division discovered imiquimod as part of a