• RNA traditionally known as the intermediary between DNA and protein, and passive conduit for information

• RNA also helps turn genes on and off, aid chemical reactions, slice and dice other RNAs, and build proteins through transcription

• harnessing RNA for use in medicines initiateed the field of RNA therapies → first two RNA-based therapies used for hereditary ATTR amyloidosis

  • Disease definition: progressive and potentially fatal disorder in which abnormal proteins build up in nerves nad organs such as heart

• biggest barrier to RNA therapy is delivering RNA to correct place in cells → really key for getting drugs in the liver as many proteins implicated in diseases

• three main categories: (1) those that target nucleic acids (DNA or RNA) (2) targeting proteins (3) encoding proteins

• for targeting nucleic acids, two distinct types of therapies that target nucleic acids: single-stranded antisesne oligonucleotides (ASOs) | double-stranded molecules that operate through cellular pathway known as RNA interference (RNAi)

• ASOs are short stretches of modified DNA made up of about 13-25 building blocks, or nucleotides → moleucles prevent mRNA from being translted into protein by several mechanisms (blocking start of translation or tagging mRNA for degredation)

  • inotersen is an ASO → main approved drug in 2019

• ASOs can also alter splicing, process that sculpts a precurosr messenger RNA into its mature form → two of this type of ASO received FDA approval in 2016: nusinersen targets fatal inherited condition called spinal muscular atrophy | eteplirsen is treatment for Duchenne muscular dystrophy

  • the latter is an example of exon skipping drug, using ASO to block only the mutated portion of a gene from being expressed = results in protein that is functional but lacks mutated portion that causes a pathology

• RNAi makes use of double-stranded molecules, making it harder to get into cells than ASOs but advantage is that fewer molecules are needed for therapy to be effective → RNAi involves small interfering RNAs (siRNAs) that are 21-23 nucleotides long or similar to moleucles such as microRNAs that degreade mRNA and prevent it from being translated into protein

  • other amyloidosis drug approval called patisiran is siRNA therapy

• RNA therapies that use mRNAs are being used to develop personalized cancer vaccines and those for ZIka viruses

  • researchers also exploring whether these type of treatments can be used as protein-replacement therapies for rare conditions such as haemophilia (blood-clotting disorder)

• many researchers using hybrid strategies of three main RNA forms → Apic Bio using silence and replcae which uses RNAi to silence a harmful gene and mRNA component that encodes a normal version of the corresponding mutated protein

RNA-Based Vaccines in Cancer Immunotherapy:

• RNA vaccines traditionally consist of messenger RNA synthesized by in vitro transcription using bacteriophage RNA polymerase and template DNA that encodes antigens of interest for specific disease → mRNA transcripts are translated directly in cytoplasm and then resulting antigens presented to antigen presenting cells for stimulated immune response
  • alternatively, dendritic cells can be loaded with either tumor associated antigen mRNA or total tumour RNA and delivered to the host to elicit specific immune response
• cancer immunotherapy seeks to stimualte host antitumor immune response, leads to tumor shrinkage and imrpoved clinical outcomes
  • discovery of agents aimed at enhancing immune responses against tumors exploded → include cytokines, immune checkpoint inhibitors, adoptive T cell therapies, and numerous vaccine strategies
    • several drugs like ipilumumab and nivolumab are impressive for benefits shown in phaseIII
• vaccines can be more difficult to produce and shown more modest clinical responses in patients → moreso well-tolerated and safer therapy that offers potential to avoid drug resistance and obtain durable treatment responses promoter
  1. DNA plasmid administered to host and interalized by host cells
  2. Transcribed in nucleus and translted in cytoplasm by cell
  3. resulting proteins processed into peptides which are presented on the surface of host-antigen-presenting cells (APCs) with major histocompability complex molecules (MHC)
  4. peptide-MHC complex recognized by antigen-specific T cells, results in cellular host immune response
  5. RNA vaccines involve messenger RNA synthesized by in vitro transcription using bacteriophage's RNA polymerase and template DNA that encodes antigens of interest
  6. Host cells interalize mRNA transcripts, then translated directly in cytoplasm and then like DNA Vaccines, resulting antigens are presented to APC to stimulate an immune response
• important to recognize mRNA-encoded products are degraded by proteasomes and presented on MHC class I molecules to CDG+T cells and do not reach MHC Class II