Pharmacotherapeutic group: Chemotherapeutics for topical use, antivirals, ATC Code: D06BB10
Imiquimod is an immune response modifier. Saturable binding studies suggest a membrane receptor for imiquimod exists on responding immune cells. Imiquimod has no direct antiviral activity. In animal models imiquimod is effective against viral infections and acts as an antitumour agent principally by induction of alpha interferon and other cytokines.
Increases in systemic levels of alpha interferon and other cytokines following topical application of imiquimod were demonstrated in a pharmacokinetic study.
Actinic keratosis (data available for the test product, Bascellex 50 mg/g cream)
Clinical efficacy
A randomized, double-blind, multiple-site, placebo-controlled, parallel-design, clinical study was performed to evaluate the therapeutic equivalence of the test product, Bascellex 50 mg/g to the reference product, imiquimod 5% cream in patients with actinic keratosis. Patients were randomized and treated for 8 weeks (two 4-week courses).
Efficacy evaluations were based on lesion counts, performed by Investigator at all clinic visits. The primary statistical analysis of interest was the proportion of patients considered to be a Complete Cure, defined as 100% clearance of all AK lesions within the treatment area.
For therapeutic equivalence evaluation of the primary endpoint in the PP and the mITT populations, the following results were observed: The 95% confidence interval for the difference between the proportion of patients considered a Complete Cure in the Test and the Reference product groups was contained within the equivalence interval of -20% to +20% for both populations. For the superiority analyses of the primary endpoint, the following results were observed: The proportion of patients considered Complete Cure in the Test and Reference groups was significantly higher at the 5% significance level (p < 0.05) than the proportion of patients considered Complete Cure in the Placebo group.

Therefore, both equivalence and superiority were demonstrated for the primary endpoint.
Actinic keratosis (data available for the reference product, imiquimod 5% cream)
Clinical efficacy
The efficacy of imiquimod applied 3 times per week for one or two courses of 4 weeks, separated by a 4 week treatment-free period, was studied in two double-blind vehicle controlled clinical trials.
Patients had clinically typical, visible, discrete, nonhyperkeratotic, nonhypertrophic AK lesions on the balding scalp or face within a contiguous 25 cm2 treatment area. 4-8 AK lesions were treated. The complete clearance rate (imiquimod minus placebo) for the combined trials was 46.1% (CI 39.0%, 53.1%).
One-year data from two combined observational studies indicate a recurrence rate of 27% (35/128 patients) in those patients who became clinically clear after one or two courses of treatment. The recurrence rate for individual lesions was 5.6% (41/737). Corresponding recurrence rates for vehicle were 47% (8/17 patients) and 7.5% (6/80 lesions).
Two open-label, randomised, controlled clinical trials compared the long-term effects of imiquimod with those of topical diclofenac in patients with actinic keratosis with respect to the risk of progression to in situ or invasive squamous cell carcinoma (SCC). Treatments were given as officially recommended. If the treated AK field was not completely cleared of lesions, additional treatment cycles could be started. All patients were followed-up until withdrawal or up to 3 years after randomisation. Results are emerged from a meta-analysis of both trials.
A total of 482 patients were included into the trials, of these 481 patients received study treatments, and of these 243 patients were treated with imiquimod and 238 patients with topical diclofenac. The treated AK field was located on the balding scalp or face with a contiguous area of about 40 cm² for both treatment groups presenting with a median number of 7 clinically typical AK lesions at baseline. There is clinical experience from 90 patients who got 3 or more imiquimod treatment cycles, 80 patients received 5 or more courses of imiquimod treatment over the 3-year study period.
Regarding the primary endpoint, histological progression, overall 13 of 242 patients (5.4%) of the imiquimod group and 26 of 237 patients (11.0%) of the diclofenac group were found to have a histological progression to in situ or invasive SCC within 3 years, a difference of -5.6% (95% CI: -10.7% to -0.7%). Thereof 4 of 242 patients (1.7%) of the imiquimod and 7 of 237 patients (3.0%) of the diclofenac group were found to have a histological progression to invasive SCC within the 3-year period.
A total of 126 of 242 patients treated with imiquimod (52.1%) and 84 of 237 patients treated with topical diclofenac (35.4%) showed complete clinical clearance of the treated AK field at week 20 (i.e. about 8 weeks after the end of the initial treatment cycle); a difference of 16.6% (95% CI: 7.7% to 25.1%). For those patients with complete clinical clearance of the treated AK field recurrence of AK lesions was evaluated. A patient was counted as recurrent in these trials if at least one AK lesion was observed in the completely cleared field whereby a recurrent lesion could be a lesion which occurred at the same location as a formerly cleared lesion or a newly identified lesion anywhere in the treated AK field. The risk for recurrence of AK lesions in the treated field (as defined above) was 39.7% (50 of 126 patients) until month 12 for patients treated with imiquimod compared with 50.0% (42 of 84 patients) for patients treated with topical diclofenac, a difference of -10.3% (95% CI: -23.6% to 3.3%); and 66.7% (84 of 126 patients) for a treatment with imiquimod and 73.8% (62 of 84 patients) for topical diclofenac until month 36, a difference of -7.1% (95% CI: -19.0% to 5.7%).
A patient with recurrent AK lesions (as defined above) in the completely cleared field had a chance of about 80% to become completely cleared again following an additional imiquimod treatment cycle compared with a chance of about 50% for a re-treatment with topical diclofenac.
Paediatric population
The approved indication actinic keratosis is a condition not generally seen within the paediatric population and was not studied.
Imiquimod has been evaluated in four randomised, vehicle controlled, double-blind trials in children aged 2 to 15 years with molluscum contagiosum (imiquimod n = 576, vehicle n = 313). These trials failed to demonstrate efficacy of imiquimod at any of the tested dosage regimens (3x/week for ≤16 weeks and 7x/week for ≤8 weeks).
The benefit-risk of the Bascellex 50 mg/g cream in the indications external genital and perianal warts and small superficial basal cell carcinomas, approved for the reference product imiquimod 5% cream, is unknown due to lack of data.