Nucleic Acid-Based Therapeutics Overview

Study Notes

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.

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).

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.

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 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 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.