Phase II clinical trials have shown that fosfluridine has the potential of becoming an effective and well-tolerated oral therapy for patients with advanced actinic keratosis.

Actinic keratoses are the most common pre-malignant lesions in humans. Increasingly, actinic keratosis is considered a carcinoma in situ, representing tumor cells which are initially confined to the epidermis, the outer layer of the skin, but which may have the potential to progress to invasive squamous cell carcinoma (white skin cancer).