Recent advances in the design of Hedgehog pathway inhibitors for the treatment of malignancies.

INTRODUCTION: The Hedgehog (Hh) signaling pathway is known to be dysregulated in several forms of cancer. Hence, specifically targeting this signaling cascade is a valid and promising strategy for successful therapeutic intervention. Several components within the Hh pathway have been proven to be druggable; however, challenges in the discovery and development process for small molecules targeting this pathway have been identified. AREAS COVERED: This review details both the current state and future potential of Hh pathway inhibitors as anticancer chemotherapeutics that target a variety of human malignancies. EXPERT OPINION: The initial development of Hh pathway inhibitors focused on small-molecule antagonists of Smoothened, a transmembrane protein that is a key regulator of pathway signaling. More recently, efforts to identify and develop inhibitors of pathway signaling that function through alternate mechanisms have been increasing. However, none of these have advanced into clinical trials. Further, early evidence suggesting the broad application of Hh pathway inhibitors as a monotherapy in a wide range of human cancers has not been validated. The potential for Hh pathway inhibitors as combination therapy has demonstrated promising preclinical results. However, more research to identify rational drug combinations to fully explore the potential of this anticancer drug class is warranted.