Oligonucleotide Therapeutics—Complementing Modern Medicine

Oligonucleotide therapeutics are short DNA or RNA molecules that modulate the expression of target RNA for the treatment of diseases. These oligos are:

• Usually about 20 nucleotides long,
• Single- or double-stranded,
• Traditionally chemically synthesized using phosphoramidites as building blocks.

This drug family includes antisense oligonucleotides (ASOs), small interfering RNAs (siRNAs) involved in RNA interference (RNAi), small activating RNAs (saRNAs), aptamers, and guide RNAs (gRNAs) involved in CRISPR gene editing technology. As of early 2023, there are 14 such drugs currently commercialized worldwide.* Twelve of these are approved in the United States, the majority of which are ASOs and siRNAs. They treat diseases including muscular dystrophy, polyneuropathy, and hypercholesterolemia, with many more therapeutics currently in development and other diseases being targeted.

* Based on molecular databases, press releases, market reports, clinicaltrials.gov, and expert interviews.

They both act on target RNA, resulting in RNA cleavage and ultimately preventing protein translation. However, their structure and mechanisms are different. ASOs are single-stranded oligos that recruit RNase H1 to cleave their RNA targets in the nucleus or the cytoplasm. On the other hand, RNAi involves double-stranded siRNAs that recruit the RNA-induced silencing complex (RISC) to cleave their RNA targets in the cytoplasm.

The success of mRNA-based SARS-CoV-2 vaccines has brought renewed interest to other nucleic acid drugs, including ASO and RNAi therapeutics. In the next 5 years, the oligo therapeutics market is expected to grow by 25–30%; over 1,000 oligonucleotide molecules are currently in the pipeline.*

As both ASOs and siRNAs are short oligonucleotides, their stability in the body, immunogenicity to the host, specificity to their target sequences, and delivery to target organs have always been challenges.

As the building blocks for oligonucleotide therapeutics, modifications to phosphoramidite structures have been developed to improve performance and mitigate these issues. For example,

• 2′-O-methyl (2′-OMe) and 2′-fluoro (2′-Fl) modifications are commonly incorporated into siRNA oligonucleotides to improve resistance to nucleases and thermal stability, and reduce off-target effects.
• For ASOs, 2′-O-methoxyethyl (2′-MOE)–modified amidites, among others, can be incorporated to produce similar effects.
• For delivery, encapsulating oligonucleotide therapeutics in lipid nanoparticles (LNPs) or conjugating them to N-acetylgalactosamine (GalNAc) moieties that have been developed in recent years facilitate improved durability and specificity of organ targeting for nucleic acid drugs.

* Based on molecular databases, press releases, market reports, clinicaltrials.gov, and expert interviews.

They look for quality assurance, documentation support, capacity, scalability, and batch-to-batch consistency in their products.

• Quality: Providing quality products starts with solid manufacturing processes housed within a well-established quality system for quality assurance, traceability, and documentation support.
• Capacity: Drug developers want to make sure their phosphoramidite supplier is capable of meeting their capacity needs, to help minimize interruption in their drug development pipelines.
• Scalability: Scale-up and future capacity are also important when drug developers are starting with a custom modification but also looking toward their large-scale manufacturing down the road.
• Raw material consistency: Batch-to-batch consistency is very important for process developers and manufacturers. Minimizing batch-to-batch variation by the supplier starts from raw material qualification and incoming raw material testing to help ensure quality is maintained in manufacturing and final product release specifications via in-process testing.

We offer Thermo Scientific TheraPure phosphoramidites, which are suitable for oligonucleotide manufacturers for the development of therapeutic applications. Our TheraPure phosphoramidites undergo additional quality control release testing compared to our standard phosphoramidites, helping ensure that impurities and residual solvents are controlled to the stringent levels required by our customers for their oligo therapeutics.

In addition to our on-shelf products, we provide services for custom oligonucleotide chemistry such as customization of existing phosphoramidites and the development of new compounds or oligonucleotide delivery chemistries.

Outside of our phosphoramidite team, Thermo Fisher Scientific offers reagents for oligonucleotide synthesis and analysis tools for synthesized oligonucleotides, as well as the ability to synthesize large-scale oligonucleotides.

A longer version of this article was published in the “Resources and tools for oligonucleotide therapeutics” eBook in collaboration with BioPharm International. Read it and other articles in the eBook