mRNA-encoded Cas13 as a pan-respiratory antiviral - Project Summary There are over 200 viruses known to infect humans and they contribute to 6.6% of global mortality. We have approximately 91 drugs for 10 viral species and vaccines for only 16. Reassortment and antigenic changes pose challenges to vaccine efficacy; this has clearly been demonstrated during the COVID pandemic. Current drug development is focused on small molecules and neutralizing antibodies, which require high doses or frequent re-dosing to obtain functional outcomes and have also been challenged by antigenic changes. Thus, it is crucial to address the need for higher efficiency and broader spectrum antivirals. To address this need we are proposing an entirely different paradigm for antiviral development, an mRNA-encoded activatable RNase, Cas13, as a platform for a pan-respiratory treatment. Cas13 represents a programmable RNase that can directly target and degrade multiple viral messenger or genomic RNA. Synthetic mRNA is being used to deliver the RNase, as it allows for transient, non-viral delivery, with an improved safety profile over other gene therapy vectors1. Given achieving pan-respiratory results with a single mRNA-encoded Cas13 based drug is not trivial, critical steps towards that goal can be achieved by focusing on the three most impactful respiratory viruses in circulation, RSV, influenza and SARS-CoV-2. To date, our team was the first to demonstrate efficacy of mRNA-encoded Cas13 in vitro and in vivo via nebulizer-based lung delivery against influenza in the mouse model and SARS- CoV-2 in the hamster model in our recent publication in Nature Biotechnology. In order to achieve one drug for RSV, influenza and SARS-CoV-2 there are important questions/challenges that will need to be met. Thus, we will determine the optimal Cas13 species for multiple respiratory pathogens and investigate the mechanism of action of Cas13 for each virus. We will also demonstrate single drug efficacy against RSV, influenza and SAR- CoV-2 in vivo in mouse and hamster models, given as treatments for the individual viral infections, during co- infection (influenza and SAR-CoV-2), and to mitigate transmission of SARS-CoV-2.
