ACVR1 and neoplasm: After 28 days, there was a decrease in cellularity of the treated ACVR1 mutant tumours compared with controls, as assessed by counting of positive cells by immunohistochemical staining using anti-human nuclear antigen (p = 0.0079, LDN-214117, t-test) (Fig. 6c, d, g, h), though differences in proliferation (Ki67) (Supplementary Fig. 8d–g), and vascularisation (CD31) (Supplementary Fig. 8h–k) were not significant.