Prospects for RNAi Therapy of COVID-19

Abstract

COVID-19 caused by the SARS-CoV-2 virus is a fast emerging disease with deadly consequences. The pulmonary system and lungs in particular are most prone to damage caused by the SARS-CoV-2 infection, which leaves a destructive footprint in the lung tissue, making it incapable of conducting its respiratory functions and resulting in severe acute respiratory disease and loss of life. There were no drug treatments or vaccines approved for SARS-CoV-2 at the onset of pandemic, necessitating an urgent need to develop effective therapeutics. To this end, the innate RNA interference (RNAi) mechanism can be employed to develop front line therapies against the virus. This approach allows specific binding and silencing of therapeutic targets by using short interfering RNA (siRNA) and short hairpin RNA (shRNA) molecules. In this review, we lay out the prospect of the RNAi technology for combatting the COVID-19. We first summarize current understanding of SARS-CoV-2 virology and the host response to viral entry and duplication, with the purpose of revealing effective RNAi targets. We then summarize the past experience with nucleic acid silencers for SARS-CoV, the predecessor for current SARS-CoV-2. Efforts targeting specific protein-coding regions within the viral genome and intragenomic targets are summarized. Emphasizing non-viral delivery approaches, molecular underpinnings of design of RNAi agents are summarized with comparative analysis of various systems used in the past. Promising viral targets as well as host factors are summarized, and the possibility of modulating the immune system are presented for more effective therapies. We place special emphasis on the limitations of past studies to propel the field faster by focusing on most relevant models to translate the promising agents to a clinical setting. Given the urgency to address lung failure in COVID-19, we summarize the feasibility of delivering promising therapies by the inhalational route, with the expectation that this route will provide the most effective intervention to halt viral spread. We conclude with the authors' perspectives on the future of RNAi therapeutics for combatting SARS-CoV-2. Since time is of the essence, a strong perspective for the path to most effective therapeutic approaches are clearly articulated by the authors.

Keywords: COVID-19; SARS-CoV-2; anti-viral drugs; drug delivery; siRNA.

FIGURE 1

(A) Number of deaths associated with SARS-CoV vs SARS-CoV-2 (as of May 15, 2020). Data from World Health Organization. (B) Number of Pubmed publications on “siRNA and cancer” and “siRNA and SARS” between 2000 and 2010. The relative numbers of published papers in the two field is indicative of relative emphasis of deploying the newly emerging RNAi technology in cancer and SARS CoV infections.

FIGURE 2

Main events in cellular entry and trafficking of CoV. Some of the outlined steps were inferred form the SARS-CoV infection of host cells. Figure courtesy of BioRender.

FIGURE 3

Different approaches to vaccine development against COVID-19 disease. Main strategies are schematically shown, which relies on (from top left, clockwise) (i) nucleic acid (DNA and RNA) vaccines delivered with nanoparticulate carriers and coding for specific viral sub-units or virus-neutralizing agents, (ii) direct administration of DNA/RNA expression systems with forced expression, (iii) viral vaccines composed of recombinant or attenuated viruses, (iv) vaccines derived from recombinant viral proteins or purified sub-unit proteins, and (v) cell based vaccines relying of modification and administration of cells. Figure courtesy of BioRender.