TGFB1 and cancer: In this manuscript, we elucidate the crystal structure of the intra­cellular domain of TβR1 (ICD) in complex with the inhibitor SB505124 [2-(4-(benzo)[d][1,3]dioxol-5yl)-2-tert-butyl-1H-imidazol-5-yl)-6-methylpyridine], shedding light on the regulatory mechanisms of TGF-β signalling and its implications in cancer biology.