Efficacy and Safety of Imiquimod 3.75% from Lmax in Actinic Keratosis According to Fitzpatrick Skin Type

BACKGROUND: Imiquimod 3.75% is an effective actinic keratosis (AK) treatment that detects and clears clinical and subclinical lesions across an entire sun-exposed field such as the full face or balding scalp. OBJECTIVE: To determine the efficacy and safety of imiquimod 3.75% according to patients' Fitzpatrick skin type. METHODS: Data were pooled from two identical 14-week, double-blind studies. Patients were randomized to imiquimod 3.75% or placebo and applied study medication to the full face or balding scalp each day for 2 two-week treatment cycles separated by a two-week treatment-free interval. End of study (EOS) was eight weeks after the last treatment application. Patients were subgrouped according to whether they had Fitzpatrick skin types I or II (FST I/II), or types III or IV (FST III/IV). Efficacy was analyzed using the reduction in lesions from Lmax (maximum lesion count during treatment) to EOS. This assesses whether clinical lesions, and subclinical lesions which become detectable during treatment, are cleared. Safety was assessed by monitoring local skin reactions. RESULTS: In total, 173 patients with FST I/II and 142 with FST III/IV were included. The median percentage reductions in lesions from Lmax to EOS were similar in patients treated with imiquimod 3.75% with FST I/II and FST III/IV (94.2% and 89.7%, respectively) as were the median absolute reductions in lesions from Lmax to EOS (19.0 and 17.0, respectively). These reductions were significantly greater with imiquimod 3.75% versus placebo in the two respective FST subgroups (P<0.0001). The frequency of local skin reactions was similar in the two imiquimod 3.75% FST subgroups. CONCLUSIONS: Imiquimod 3.75% is well tolerated and effective at clearing clinical and subclinical lesions across large areas of sun-exposed skin in patients with FST I-IV, and so can be considered for AK patients with any of these skin types.