**8. Future prospects**

As the miRNA field dramatically grows, a better understanding of miRNA biogenesis and path-physiologic function will help to develop miRNA-based therapies. In addition, it is well known that a specific miRNA could target multiple genes and affect different organs in the same time. Therefore, research efforts should try to maximize the benefit of target diversity and prevent off-target effects. To achieve this goal, improvement of the chemical design of miRNA antisense and mimics and developing novel delivery systems are very important to ensure that the desired miRNA concentrations are achieved in organs and the targets are specifically regulated.

The use of synthetic miRNAs holds great promise as a new class of potential therapeutic agents by silencing the gene(s) of interest. Applicable to a wide variety of human diseases such as cancer, viral infections, genetic disorders, and cardiovascular disease, the attractiveness of miRNA therapeutics is their ability to target specific genes of interest, not always possible with small molecules or protein-based drugs. When designing drugs for therapeutic use, RNA sequence must be carefully designed to avoid undesired effects and immune responses in the body. The care into making a safe and relevant delivery system for miRNA-based therapies must also balance considerations of target tissue and cell delivery, cellular uptake, and nuclease degradation of the molecule.

Although a considerable number of clinical trials involving miRNA therapeutics have been conducted over the years, not all of those miRNA therapeutics have so far moved into clinical implication. The big challenges for miRNA-based therapeutics is to identify the best miRNA candidates or miRNA targets for each type of disease. The other challenges include the optimizing the miRNA delivery vehicles that can have higher targeting specificity and stability, as well as having lower toxicities and off-target effects. Although there are still hurdles to the use of mRNA-targeting approaches for clinical applications, with the rapid expansion occurring in this field, the prospects of miRNA-based therapeutics remain promising.
