Fig. 1

Hydrocarbon stapling leads to increased EJ1 activity in comparison to HER-directed monoclonal therapies. a EJ1 sequence with PTD4 domain (underlined) corresponding to EGFR juxtamembrane domain sequence 643–663. Stabilized alpha helix (SAH) variations 1–5 beneath, with asterisks (*) indicating sites of staple. Control peptide (CP) with altered residues indicated by double underline. Stapled control (5) asterisks (*) indicate sites of staple. b Cartoon representation of EJ1 structure, with staple variation 5 highlighted. Positively charged residues indicated in blue, negatively charged residues in red [94]. c Cartoon representation of CP structure, with staple variation highlighted. d Cell viability assay performed in MDA-MB-468 cells after 24 h comparing unstapled EJ1 versus staple variations SAH1, SAH4, and SAH5, with increasing concentrations. e Visualization of MDA-MB-468 cells untreated, treated with 10 µM EJ1, and 10 µM SAH5-EJ1 after 60 min. Scale bars represent 50 µm. f–h Cell viability assay performed in MDA-MB-468, MCF10A, or CHO cells over 3 days comparing treatment with Sapitinib (blue lines), SAH5-EJ1 (red lines), and SAH5-CP (grey lines). Solid lines represent 24 h; dashed lines represent 72 h. i Cell viability assay performed in BT474 cells over 3 days comparing treatment with Trastuzumab (µg/mL) (blue) to SAH5-EJ1 or SAH5-CP (µM) (red and grey, respectively). p < 0.001 in all cases unless indicated by NS for p > 0.05. Data shown in d, f, g–i represent mean ± percent difference of assays performed in triplicate