Antisense oligonucleotides (ASO)-based drugs are emerging with great potential as therapeutic compounds for diseases with unmet medical needs. To be effective as clinical entities, ASOs must adequately reach the intracellular RNA and DNA targets at therapeutic concentrations. Over the past decades various covalently attached delivery vehicles have been used for intracellular delivery of ASOs. The most promising approach is the use of biocompatible cell-penetrating peptides (CPPs) covalently conjugated to ASOs. The stability of the linkage is of supreme importance for maximal intracellular delivery to achieve the desired therapeutic effect. We have investigated the efficiency and stability of different bio-orthogonal and non-reductive linkages including triazole, thioether and thiazole moieties.1 Details will be reported about the design, synthesis, and our current findings of these novel Peptide-ASO conjugates.