Although we found extension of the N-Myc helical region by an additional five residues at the Cterminus confers limited effect in terms of potency (N-Myc73-94; IC50= 199 ± 13 µM, Table ), this sequence offered additional positions for the introduction of a constraint in comparison to N-Myc61-89. More specifically, constrained variants involving the replacement of the i and i + 4 pairs: