Biological activity of AfBPP probes 2, 3 and 4. a) Probes 2 and 3, but not 4 show an increase in activity in a mouse H2K mdx cellular utrophin gene firefly luciferase reporter assay, although to a lesser extent than ezutromid, n=4, representative graph shown. b) Probes 2 and 3 increase utrophin protein, but inactive probe 4 does not. Representative utrophin western blots, top: probe treatment of mouse H2K mdx myoblasts, bottom: probe treatment of human DMD myoblasts. H, heregulin; M, protein standard (in kDa). Uncropped blots are presented in Supplementary Figure S4. c,d) Probes 2 and 3 increase utrophin protein levels comparable to heregulin and ezutromid after 24 h of compound treatment in mouse H2K mdx cells (c) and human DMD myoblasts (d) determined by western blot. Bars represent means of utrophin levels normalised to total protein and relative to DMSO, error bars are standard error of the mean, n=3. * p<0.05, ** p<0.005, ns=non‐significant.