Single therapeutic dose of an antiviral UL29 siRNA swarm diminishes symptoms and viral load of mice infected intranasally with HSV-1

Herpes simplex virus type 1 (HSV-1) is a human pathogen that causes recurrent infections. Acyclovir-resistant strains exist and can cause severe complications, which are potentially untreatable with current therapies. We have developed siRNA swarms that target a 653 base pair long region of the essential HSV gene UL29. As per our previous results, the anti-UL29 siRNA swarm effectively inhibits the replication of circulating HSV strains and acyclovir-resistant HSV strains in vitro, while displaying a good safety profile. We investigated a single intranasal therapeutic dose of a siRNA swarm in mice, which were first inoculated intranasally with HSV-1 and given treatment 4 h later. We utilized a luciferase-expressing HSV-1 strain, which enabled daily follow-up of infection with in vivo imaging. Our results show that a single dose of a UL29-targeted siRNA swarm can inhibit the replication of HSV-1 in orofacial tissue, which was reflected in ex vivo HSV titers and HSV DNA copy numbers as well as by a decrease in a luciferase-derived signal. Furthermore, the treatment had a tendency to protect mice from severe clinical symptoms and delay the onset of the symptoms. These results support the development of antiviral siRNA swarms as a novel treatment for HSV-1 infections.

Overcoming Pharmaceutical Bottlenecks for Nucleic Acid Drug Development

The outbreak of the coronavirus disease 2019 (COVID-19) pandemic and swift approval of two mRNA vaccines have put nucleic acid therapeutics in the spotlight of both the scientific community and the general public. Actually, in addition to mRNAs, multiple nucleic acid therapeutics have been successively commercialized over the past few years. The rapid development of nucleic acid drugs not only demonstrates their superior potency but also marks a new era of the field. Compared with conventional treatments targeting proteins rather than the root causes of diseases at the genetic level, nucleic acids are capable of achieving long-standing or even curative effects against undruggable disorders by modulating gene expression via inhibition, editing, addition, or replacement. This offers a terrific arsenal for expanding therapeutic access to diseases lacking current treatment options and developing vaccines to provide swift responses to emerging global health threats.Despite the stunning success and recent resurgence of interest in the field, the unfavorable physicochemical characteristics (i.e., the negative charge, large molecular weight, and hydrophilicity), susceptibility to nuclease degradation, off-target toxicity, and immunogenicity are a brake for moving nucleic acid therapeutics from bench to bedside. Currently, developing technologies to improve the circulation stability, targeting affinity, cellular entry, endolysosomal escape, efficacy, and safety of nucleic acid drugs still remains a major pharmaceutical bottleneck.In this Account, we outline the research efforts from our group on the development of technology platforms to overcome the pharmaceutical bottlenecks for nucleic acid therapeutics. We have engineered a variety of intelligent delivery platforms such as synthetic nanomaterials (i.e., lipid nanoparticles, polymers, and inorganic nanoparticles), physical delivery methods (i.e., electroporation), and naturally derived vehicles (i.e., extracellular vesicles), aiming at endowing nucleic acids with improved circulation stability, targeting affinity, and cellular internalization (Get in) and stimuli responsive endolysosomal escape capability (Get out). Moreover, we will discuss our progress in developing a series of modification strategies for sequence engineering of nucleic acids to endow them with enhanced nuclease resistance, translation efficiency, and potency while alleviating their off-target toxicity and immunogenicity (Sequence engineering). Integrating these technologies may promote the development of nucleic acid therapeutics with potent efficacy and improved safety (Efficacy & safety). With this Account, we hope to offer insights into rational design of cutting-edge nucleic acid therapeutic platforms. We believe that the continuing advances in nucleic acid technologies together with academic-industry collaborations in the clinic, will promise to usher in more clinically translatable nucleic acid therapeutics in the foreseeable future.

Probing the inherent stability of siRNA immobilized on nanoparticle constructs

Small interfering RNA (siRNA) is a powerful and highly effective method to regulate gene expression in vitro and in vivo. However, the susceptibility to serum nuclease-catalyzed degradation is a major challenge and it remains unclear whether the strategies developed to improve the stability of siRNA free in serum solution are ideal for siRNA conjugated to nanoparticle surfaces. Herein, we use spherical nucleic acid nanoparticle conjugates, consisting of gold nanoparticles (AuNPs) with siRNA chemisorbed to the surface, as a platform to study how a model siRNA targeting androgen receptor degrades in serum (SNA-siRNAAR). In solutions of 10% (vol/vol) FBS, we find rapid endonuclease hydrolysis at specific sites near the AuNP-facing terminus of siRNAAR, which were different from those of siRNAAR free in solution. These data indicate that the chemical environment of siRNA on a nanoparticle surface can alter the recognition of siRNA by serum nucleases and change the inherent stability of the nucleic acid. Finally, we demonstrate that incorporation of 2'-O-methyl RNA nucleotides at sites of nuclease hydrolysis on SNA-siRNAAR results in a 10-fold increase in siRNA lifetime. These data suggest that strategies for enhancing the serum stability of siRNA immobilized to nanoparticles must be developed from a dedicated analysis of the siRNA-nanoparticle conjugate, rather than a reliance on strategies developed for siRNA free in solution. We believe these findings are important for fundamentally understanding interactions between biological media and oligonucleotides conjugated to nanoparticles for the development of gene regulatory and therapeutic agents in a variety of disease models.