Study to Evaluate the Safety, Tolerability and Efficacy of BF-200 ALA (Ameluz®) in the Field-directed Treatment of Actinic Keratosis (AK) on the Extremities and Neck/Trunk With Photodynamic Therapy (PDT) Using a RhodoLED Lamp

Inclusion criteria

• ✓. Willingness and ability of subjects to provide informed consent and sign the Health Insurance Portability and Accountability Act (HIPAA) form. A study-specific informed consent and HIPAA form must be obtained in writing prior to starting any study procedures.
• ✓. 4 - 15 mild to moderate clinically confirmed AK lesions according to Olsen either on the extremities or on the neck/trunk with a diameter of ≥ 4 mm that must be present in the treatment field (defined as AK target lesions). In addition, non-target AK lesions may be present in the treatment field, including up to two severe AK lesions ≥ 4 mm. For each severe AK lesion (≥ 4 mm), a biopsy must be taken for confirmation of diagnosis. The treatment field (continuous or in several patches) totaling approx. either 80 cm², 160 cm² or 240 cm2 must be within one effective illumination area of the BF-RhodoLED® XL but may require up to three illuminations with the BF-RhodoLED®. All AK target lesions and, if applicable, severe AK lesions ≥ 4 mm located in the treatment field should be clearly distinguishable, without restrictions on the distance between lesions, and should have a minimal distance of 1 cm to the border of the treatment field.
• ✓. All sexes, ≥ 18 years of age.
• ✓. Willingness to undergo a 2 mm punch biopsy for each (up to two) severe AK lesion ≥ 4 mm, if applicable, at the screening visit.
• ✓. Willingness and ability to comply with study procedures, particularly willingness to receive up to 2 PDTs within approximately 12 weeks.
• ✓. Subjects with good general health or with clinically stable medical conditions will be permitted to be included in the study.
• ✓. Willingness to stop the use of moisturizers and any other non-medical topical treatments within the treatment field at least 24 h prior to the next clinical visit.
• ✓. Acceptance to abstain from extensive sunbathing and the use of a solarium or tanning beds during the treatment phase.