Nucleic Acid-Based Therapeutics Overview

Nucleic Acid-Based Therapeutics

• Genentech pioneered the production of human proteins in bacteria using recombinant DNA. Somatostatin was an early product.
• Marvin Caruthers and Phosphoramidite Chemistry advanced DNA/RNA synthesis in the 1980s, transitioning from liquid-phase to solid-state methods. This facilitated synthesis of longer strands, contributing to the Human Genome Project.
• Antisense oligonucleotides (ASOs) were shown in 1978 to block viral replication (e.g., RSV).
• DNA/RNA can be chemically modified to enhance their efficacy as drugs, making them resistant to degradation by the body and improving target specificity.
• Fomivirsen (Vitravene), the first oligonucleotide drug, was approved in 1998 to treat cytomegalovirus retinitis in immunocompromised patients. It inhibits viral replication.
• Challenges for ASO therapies include liver/kidney toxicity, immune stimulation, stability issues (nucleases), and ensuring the drug reaches the correct target cells.
• Several FDA-approved ASO drugs exist, with more in clinical trials.

ASO's Continued

• Locked Nucleic Acids (LNAs) stabilize the ASO double helix, improving specificity and stability.
• Gapmer technology uses RNA mimics around a target DNA sequence to recruit the cell's RNAse H, degrading the target DNA and blocking protein expression.
• Gapmer therapies are effective for liver and muscle diseases, and diseases related to abnormal mRNA splicing, such as Duchenne muscular dystrophy and Spinal muscular atrophy (SMA).

RNA Interference (RNAi)

• siRNA duplexes bind to the RISC complex, targeting mRNA for degradation, silencing gene expression.
• Argonaut (Argo) protein within the RISC complex degrades the mRNA.
• RNAi is a natural mechanism found in organisms like C. elegans.
• RNAi can have off-target effects.

Nucleic Acid Drug Delivery

• Recent advances have improved nucleic acid drug delivery methods through various approaches, including nanoparticles, nanotubes, bulky conjugates, exosomes, and peptides.
• Many new drugs are currently in clinical trials.

CRISPR/Cas9 Technology

• CRISPR/Cas9 is a gene-editing technology that allows for precise deletion or insertion of genetic material in a cell's genome.
• A guideRNA directs the Cas9 enzyme to a target DNA sequence, creating a double-stranded break.
• The cell's repair mechanisms then lead to the desired change.
• CRISPR/Cas9 has been used as a potential therapy for sickle-cell anemia, however, cautions exist due to potential drawbacks.

mRNA Therapeutics

• mRNA therapies have demonstrated success in vaccines (e.g., COVID-19) and are being explored for cancer therapies.
• Clinical studies are underway to expand the application of mRNA vaccines.