Benzolactam-Based Gli Inhibitors: Synthesis and Structural Analysis

The Hedgehog signaling pathway plays an essential role in cancer progression, including in basal cell carcinoma and medulloblastoma. This process is driven by oncogenic Gli transcription factors, which are regulated by the signaling protein Smoothened (Smo). While Smo inhibitors have shown clinical utility, drug resistance can limit their effectiveness. Here, we present a synthetic and functional evaluation of benzolactam-derived TPPB, a potent Gli inhibitor that operates downstream of Smo via protein kinase C (PKC) activation. We developed a concise, stereoselective route to the benzolactam scaffold, enabling the synthesis of TPPB. In vivo testing confirmed the antitumor activity of this lead compound in a Gli-dependent basal cell carcinoma model. To identify simplified analogues, we employed a function-oriented synthesis strategy, focusing on key positions within the scaffold that enhance Gli inhibition. Our results highlight the importance of specific benzolactam-based structural motifs and suggest guidelines for designing Smo-independent Gli inhibitors.