The perspective of using messenger RNA (mRNA) as a therapeutic molecule first faced some uncertainties due to concerns about its instability and the feasibility of large-scale production. Today, given technological advances and deeper biomolecular knowledge, these issues have started to be addressed and some strategies are being exploited to overcome the limitations. Thus, the potential of mRNA has become increasingly recognized for the development of new innovative therapeutics, envisioning its application in immunotherapy, regenerative medicine, vaccination, and gene editing. Nonetheless, to fully potentiate mRNA therapeutic application, its efficient production, stabilization and delivery into the target cells are required. In recent years, intensive research has been carried out in this field in order to bring new and effective solutions towards the stabilization and delivery of mRNA. Presently, the therapeutic potential of mRNA is undoubtedly recognized, which was greatly reinforced by the results achieved in the battle against the COVID-19 pandemic, but there are still some issues that need to be improved, which are critically discussed in this review.

Cell‐penetrating peptides (CPPs) are one of the most efficient vectors for achieving cellular uptake of different cargos. However, their application in cancer therapy is greatly limited due to the lack of tissue selectivity, as they are widely distributed in most tissues following in vivo administration. To introduce specificity and improve tumor targeting, a combination of a cell‐penetrating peptide (CADY) and a targeting ligand, the laminin receptor binding peptide (YIGSR) to target the 37/67 kDa laminin receptor, known to be upregulated in most cancer cells and to be correlated with the invasiveness and metastatic potential, is formulated. The targeting CPP named “Y‐CADY” does not induce any change in the physico‐chemical properties (secondary structure, small interference RNA (siRNA) complexation, size, and charge) of CADY. Interestingly, Y‐CADY is more efficient than CADY for gene silencing in cell lines, and more potent for targeting and for inducing apoptosis of tumor xenografts in zebrafish embryos. The present study demonstrates that the novel targeting CPP “Y‐CADY” is efficient for gene silencing and can serve as a vector to target cancer cells in vivo.

Small interfering RNAs (siRNAs) are promising molecules for developing new therapies based on gene silencing; however, their delivery into cells remains an issue. In this study, we took advantage of stapled peptide technology that has emerged as a valuable strategy to render natural peptides more structured, resistant to protease degradation and more bioavailable, to develop short carriers for siRNA delivery. From the pool of stapled peptides that we have designed and synthesized, we identified non-toxic vectors that were able to efficiently encapsulate siRNA, transport them into the cell and induce gene silencing. Remarkably, the most efficient stapled peptide (JMV6582), is composed of only eight amino-acids and contains only two cationic charges.