Connexin43 (Cx43), the most abundantly expressed member of the connexin protein family in the heart, oligomerizes into hemichannels (HCs), forming thereafter intercellular channels known as gap junctions (GJs)¹. While GJs are involved in ‘healthy’ physiological intercellular communication, HC activity is linked to various pathological states, and therefore HC inhibition represents a potential therapeutic approach. In particular, a peptide segment of 10 residues long at the C-terminal (CT) region of Cx43 is known to be involved in both proteinogenic intra- and intermolecular interactions that result in HC activity regulation². Previously reported mimetic peptides based on this CT region (e.g., αCT1³) have revealed to be promising therapeutic agents preserving left ventricular function cardiac after ischemia/reperfusion injury⁴. The rapid proteolytic cleavage of these peptide-based inhibitors in serum, however, together with their low bioavailability makes them poor systemically-applied drug candidates. To overcome such limitations, a set of chemical strategies was used to transform the abovementioned αCT1 peptide into a conformationally stabilized and proteolytically stable peptide inhibitor. After an initial Ala scan, side chain substitutions were introduced, allowing for macrocyclization through the formation of a covalent triazole linker (a), as well as N- and C- terminal modifications, including lipidation through different linkers to obtain a water soluble cell-penetrating ‘pepducin’ variant (b). A cardiac cell targeting strategy was also investigated, in which a homing peptide (CRPPR)⁵ was introduced in order to selectively deliver the active peptidomimetic to the cardiac endothelium (c). These stabilized peptides were tested for their selectivity and their inhibitory capacity by means of in vitro assays, and the roles of the cardiac targeting moiety and the lipidated tail in peptide delivery were investigated.