Randomized, Multi-Center, Evaluator-Blind, Vehicle-Controlled Study to Evaluate Efficacy and Safety of Reformulated Levulan Kerastick Plus Photodynamic Therapy (PDT) for Field-Directed Treatment in Patients With Actinic Keratosis (AK) of Upper Extremities

Inclusion Criteria: 1. Patient is a male or non-pregnant female aged 18-85 years. 2. Patient must have 4-8 mild to moderate actinic keratosis (AK) lesions (Olsen grade 1 or 2) in a single treatment area on their Index arm, each measuring up to 1 cm in diameter and spaced at least 1 cm apart. \[The treatment area should be approximately 25 cm², located on the extensor surface of only one of the upper extremities that is selected as the Index arm\] 3. Patients must be in good general health, avoid sunbathing or tanning devices, and maintain a consistent skincare routine throughout the study. 4. Patient is willing to stop using all topical products within the Treatment Area within 8 hours of a scheduled clinic visit with an efficacy evaluation. 5. Women of childbearing potential must use highly effective contraception; men with such partners must use barrier methods unless surgically sterile. Exclusion Criteria: 1. Presence of Olsen grade 3 AK, untreated or suspicious skin cancers, or significant skin abnormalities (e.g., psoriasis, eczema) in the treatment area. 2. Active herpes simplex infection or history of ≥2 outbreaks in the treatment area within the past year. 3. History of cutaneous photosensitization, porphyria, photodermatosis, or hypersensitivity to porphyrins. 4. Positive human immunodeficiency virus (HIV) test result, hepatitis B surface (HBS) antigen, or hepatitis C virus (HCV) test result 5. Immunosuppressed status (e.g., HIV, organ transplant) or known coagulation defects. 6. Use of specific topical therapies (e.g., retinoids, steroids, cryotherapy, PDT, chemical peels) on the treatment area within 2 days to 8 weeks prior to randomization. 7. Recent use of certain systemic therapies (e.g., corticosteroids, immune-modulators, retinoids, cytotoxic drugs) within 6 weeks to 6 months prior to randomization. 8. Recent use of hypericin or other phototoxic/photoallergic medications (e.g., tetracyclines, psoralenes, St. John's wort) within 8 weeks of randomization. 9. Clinically significant or unstable illnesses, or history of alcohol/drug abuse in the past year. 10. Pregnancy/lactation, recent or current participation in another clinical study, or any other condition deemed unsuitable by the Investigator.