The present invention describes a photodynamic prodrug, i.e., a substituted 4-thiothymidine (4-TT), which is able to cross the body's epithelia tissues such as the skin, oral cavity, nasal cavity, pulmonary tract, digestive tract, and blood-brain barrier, including the use of such a prodrug in a topical application for the treatment of skin hyperplasias, including skin cancer, psoriasis, keloids, actinic keratosis, and the like.
