Phase III study demonstrates superiority of imiquimod cream 2.5% and 3.75% in treatment of AK

Imiquimod 3.75% Is Now Available In Pharmacies Across Canada

The Journal of the American Academy of Dermatology (JAAD) has published Phase III data evaluating the safety and efficacy of imiquimod cream at two doses - 2.5% and 3.75% - administered daily on a 2-week treatment cycle. The study demonstrates that both formulations were superior to placebo, and that imiquimod 3.75% on a daily 2-week treatment cycle is superior to imiquimod 2.5% in treating actinic keratosis (AK) on a large surface area - the face or balding scalp. AKs are considered to be the earliest stage in the development of skin cancer and have the potential to progress to squamous cell carcinoma (SCC) if left untreated.

Health Canada has recently approved imiquimod cream 3.75% (Zyclara(TM)) as a topical cream for the treatment of multiple AKs located on the face or balding scalp in adults. It is now available in pharmacies across Canada.

The Phase III clinical trial program evaluated the safety and efficacy of imiquimod in patients averaging between five to 20 AKs in an area greater than 25cm on either the face or balding scalp. Imiquimod cream 3.75% administered once daily for two 2-week treatment cycles, separated by a 2-week non-treatment period, reduced total AK lesions by 82 per cent as compared to only a quarter of patients treated with placebo. Complete clearance, defined as the number of patients with zero AKs after treatment, was 36 per cent with imiquimod 3.75% versus 6 per cent with placebo. Additionally, partial clearance, defined as at least 75 per cent or greater reduction in total AKs, was achieved in 59 per cent of patients treated with imiquimod 3.75% versus only 23 per cent with placebo. Results for imiquimod 2.5% administered on the same frequency included a total AK lesion reduction of 72 per cent, complete clearance of 31 per cent and partial clearance of 48 per cent respectively. The clinical trial program was led by Neil Swanson, M.D., professor and chairman, Department of Dermatology, Oregon Health and Science University.

"The low concentration of imiquimod enhances tolerability, so patients can use it in a simple daily-dosing regimen," said Dr. Charles Lynde, dermatologist and assistant clinical professor at the University of Toronto. "This helps increase compliance which ultimately helps achieve long term medical clearance of lesions and desired cosmetic outcomes."

Approximately half, 40 to 60 per cent, of SCCs begin as untreated AKs. Anyone who has previously had an AK is at a higher risk for developing new AKs. If AKs are visible on the surface of the skin, it is likely that there are more invisible AKs just below the skin's surface, known as subclinical lesions. Therapies that treat surface areas greater than 25 cm may account for greater reductions in both AK lesions and subclinical lesions.

"With the low concentration imiquimod 3.75% you can treat a large surface area which includes lesions you can see and those that are under the skin's surface, which means a greater chance of treating AK effectively," says Dr. Lynde. "We know that patients prefer prescription creams over more invasive therapies, so the Health Canada approval offers another safe and effective option."