Discovery of a new selective ERAP1 inhibitor for Hedgehog-dependent cancer treatment

Inappropriate activation of the Hedgehog (HH) signaling pathway drives the pathogenesis of several cancers, including medulloblastoma (MB), the most common malignant brain tumor in children. HH group MB (HH-MB) is highly heterogeneous and resistant to current treatments. Understanding the molecular events underlying the control of the HH pathway is critical for the development of more effective and tailored interventions. Endoplasmic reticulum aminopeptidase 1 (ERAP1), a key regulator of the immune response, has emerged as a promising therapeutic target for HH-MB, but the lack of clinically viable ERAP1 inhibitors has hindered progress in this area. Here, we identify canthin-6-one (N1) as a selective ERAP1 inhibitor. N1 binds directly to ERAP1 and disrupts its function in the HH pathway, resulting in reduced signaling. Specifically, N1 impairs the association of ERAP1 with the deubiquitinase USP47, promoting βTrCP protein stability and Gli1 degradation. Notably, HH-dependent cells genetically depleted for ERAP1 are insensitive to N1, confirming its specificity. Remarkably, N1 inhibits HH-MB growth in vitro and in vivo, crosses the blood-brain barrier, and improves survival in an HH-MB mouse model. These findings highlight N1 as a breakthrough ERAP1 inhibitor and provide a promising therapeutic option for the treatment of HH-dependent cancers.