LAS41005 in Hyperkeratotic Actinic Keratosis

Main Inclusion Criteria: * Signed and dated written informed consent. * Men and women aged between 18 and 85 years inclusive. * Have a general good and stable health condition as confirmed by a physical examination and by medical history. * Have at least 4 but not more than 10 clinically confirmed hyperkeratotic AK target lesions of moderate to severe intensity within the face/forehead or bald scalp * Skin type I to IV according to Fitzpatrick's . * Are free of any significant physical abnormalities (e.g., tattoos, dermatoses) in the potential treatment area that may cause difficulty with examination or final evaluation. * Physical ability to apply the study preparation correctly and to follow the study restrictions and visit. * Women of childbearing potential are allowed to participate in this study, only if they use a highly effective method of contraception Main Exclusion Criteria: * Have received treatment of AK within the treatment area (face / scalp) in the three months preceding this clinical trial. * Have known hypersensitivity to the ingredients * Are subjects under immunosuppressive therapy. * Having coagulation defects which are inherited or acquired * Have evidence of clinically significant, unstable medical conditions * Have currently other malignant or benign tumors of the skin within the treatment area * Subjects who have taken topical or systemic treatments that might interfere with the study end points, within a time window that is not allowed, or who are currently taking phenytoin, methotrexate or sulfonylurea. * Subjects taking inhibitors of DPD (e.g. Brivudin, Sorivudin) * Are known to be pregnant or lactating (currently or within the past 3 months). * Have any dermatological disease in the treatment area or surrounding area that may be exacerbated by treatment * Are currently or within the past 8 weeks participating in another clinical study. * Have active chemical dependency or alcoholism as assessed by the investigator. * Subject is institutionalized because of legal or regulatory order.