Investigation of the Efficacy and Tolerability of Topical Applied Tirbanibulin on Actinic Keratoses With Downward-directed Proliferation Patterns

Inclusion Criteria: * male, female, diverse patients (\> 18yo) who are capable of giving consent * female patients are eligible if the patient is not a woman of childbearing potential (WOCBP) or if she is postmenopausal (cessation of menstruation \>12 months) or surgically sterile (bilateral tubal ligation, bilateral oophorectomy, total hysterectomy) * signed informed consent * diagnosis of at least 1 non-hypertrophic, non-hyperkeratotic actinic keratosis of the scalp or face with Olsen Grade I and PRO II or III * planned treatment of AK with Klisyri® before study start and indepently of the study * the study participant is in good general condition for his or her age and does not currently have any active diseases that, in the opinion of the investigator, justify exclusion from the study Exclusion Criteria: * known or documented intolerance to any of the ingredients of Klisyri® * any planned AK treatment other than Klisyri® in the treatment area * treatment of actinic keratoses in the treatment area within the past 3 Months (e.g. photodynamic therapy, topical 5-FU, diclofenac, imiquimod, cryotherapy etc.) * suspected invasive squamous cell cancer in the treatment area * chronic wounds, erosions, pre-existing inflamed or infected skin with disruption of the epidermal barrier in the treatment area * suspected non-compliance * current or within the last 8 weeks given systemic cancer medication * any other topical treatment against actinic keratosis in the treatment area within the past 12 weeks * any contraindication according to the Summary of Product Characteristics (SmPC) of Klisyri® * any systemic immunosuppressant given within the 8 weeks prior to the study (e.g. systemic prednisolone, azathioprine etc.) * locally applied retinoids, steroids, or other prescribed externals in the 4 weeks prior to the start of the study in the treatment area that, in the opinion of the study physician, necessitate exclusion * products containing glycolic or alpha-hydroxy acids applied locally in the treatment area in the last 4 weeks * chemical peelings in the treatment area in the last 4 weeks * simultaneous participation in a clinical trial * participation in a clinical study within the last 30 days * family members or colleagues of the investigator or the investigational team or the CRO * patient is in a position or has a relationship with the investigator that presents a potential conflict of interest