Recent Advances in Chemical Composition and Transdermal Delivery Systems for Topical Bio-actives in Skin Cancer

Skin cancer, including basal cell carcinoma, melanoma, and squamous cell carcinoma, is conventionally treated by surgery, phototherapy, immunotherapy, and chemotherapy. For decades, surgical removal of malignant cancers has favored patients' therapeutic options. However, multiple aspects, such as the patient's comorbidities, the anatomical location of the lesion, and possible resistance to recurrent excisions, can influence the decision to conduct surgery. Therefore, topical and transdermal therapy may be a more appropriate option, allowing for higher therapeutic levels at the site of action and reducing toxicity than systemic therapy. The most commonly used topical agents for treating skin carcinoma are- 5-fluorouracil, imiquimod, sonidegib, dacarbazine, etc. However, physicochemical drug characteristics and skin physiological barriers limit the anticancer potency of topical as well as transdermal drug delivery. In recent years, unquestionable signs of progress have been demonstrated to circumvent these challenges. In particular, significant studies have been made, including modification of bio-actives, permeability enhancers, incorporation of advanced nano and microcarriers, and physical enhancement devices. This critical review summarizes the advancement in the chemical composition of bioactives used in skin cancer, such as sinecatechins, BIL-010t, patidegib, gingerol, curcumin, remetinostat, epigallocatechin-3-gallate, etc. Furthermore, this review specifically addresses the progress in transdermal delivery systems for melanoma and nonmelanoma cancer therapy, emphasizing advances in physical and chemical penetration enhancement and nanocarrier-assisted transdermal systems.