Hedgehog Pathway Inhibitors: Clinical Implications and Resistance in the Treatment of Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common non-melanoma skin cancer and is on the rise. Most BCCs are benign; however, a very small percentage are locally advanced and metastatic. The pathway that normally regulates cell growth and proliferation is directed by the hedgehog pathway (HP). In BCC, it becomes over-stimulated due to genetic abnormalities. Treatments for BCC include local treatment by cryotherapy (liquid nitrogen), topical immunosuppression, surgery, or radiotherapy. Systemic treatment may be required in locally advanced lesions, metastatic BCC, or individuals who are inoperable. The systemic treatments of BCC act to inhibit the HP and are called hedgehog pathway inhibitors. The first one being vismodegib and the second sonidegib. Although these treatments have shown promising results, they have prominent side effects in almost all patients, with few patients having to discontinue the treatment. About 50% of patients did not respond to treatment from the beginning, some had partial responses, others had recurrence after discontinuing the drugs, and few had worsening of the disease. In this paper, we will explore the most common side effects, resistance, and different methods to overcome resistance to ensure the highest rate of cure for BCC.