Basal cell carcinoma (BCC), although mostly locally confined, is the most common cancer. Most BCCs harbor inactivating mutations in the membrane receptor/gene Ptch, thereby activating the Hedgehog signaling pathway (Hh) via the essential signaling molecule Smoothened (SMO). Novel small-molecule inhibitors or antagonists of SMO have shown excellent response rates in patients with locally advanced, unresectable and metastatic BCC in roughly 35-60% of patients, with disease control rates and clinical benefit being even higher. Sonidegib is the second-in-class SMO inhibitor approved for locally advanced, unresectable and metastatic BCC. Sonidegib is given once daily continuously, with specific side effects as listed in the label indication. Resistance develops over time and knowledge gleaned from other SMO inhibitors indicates that SMO mutations preventing drug binding as well as mechanisms activating the Hh pathway downstream of SMO are responsible, ultimately reactivating Hh pathway signaling. The next challenge will be to define novel salvage and SMO combination strategies for BCC and other tumors.
Keywords: Basal cell carcinoma; Hedgehog pathway; Smoothened receptor; Sonidegib.
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