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Oligonucleotide Manufacturing Facility Design: Unique Challenges

Nov 21, 2024

Shwetha Ravi Devine

Lead Process Engineer

In the ever-evolving world of molecular biology and genetic research, oligonucleotides play a pivotal role in a vast array of applications, from DNA sequencing to gene synthesis and targeted therapy development.

 

The demand for these short, customized DNA or RNA sequences has been steadily rising, driven by advances in biotechnology and our expanding understanding of genetics. They have a wide range of applications in genetic testing, research, and forensics. Because they can be manufactured as single-stranded molecules with any user-specified sequence, they are vital for artificial gene synthesis, polymerase chain reaction (PCR), DNA sequencing, molecular cloning and as molecular probes. The result is a class of pharmaceuticals revolutionizing the treatment of diseases that other therapies cannot touch.

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Oligonucleotides and “untreatable” diseases

Oligonucleotides are short strands of modified DNA and RNA sequences that are usually about 20 nucleotides in length. Thanks to DNA synthesis, oligonucleotides can be manufactured synthetically with modified nucleotides to improve their therapeutic effects. They are designed to bind to specific DNA or RNA sequences in the same manner as naturally occurring oligonucleotides, preventing genetic errors from translating into proteins. However, they do not affect the genome itself. Such therapeutics target the genetic code to reach the root cause of diseases, as opposed to biologic drugs that target proteins.

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Upstream process with oligonucleotides

The upstream process with oligonucleotides differs from traditional pharmaceutical processes due to the unique combination of chemistry and biology required. The upstream process begins with a phosphoramidite chemical reaction (i.e., the addition of bases through a repeated sequence of reactions) to grow the chain of modified nucleotides. The drug substance is then synthesized on a solid substrate in a synthesis column. These reactions involve several thousand liters of flammable solvent (ethanol, acetonitrile, and toluene) per kilogram of produced product. After synthesis, oligonucleotides are separated from the solid support by heating them in concentrated aqueous ammonium hydroxide, eliminating protecting groups from the bases and phosphates. Deprotection then removes the blocks used to ensure linear chains versus split chains. Finally, the drug undergoes a crude ultrafiltration process before moving to downstream processing.

Challenges in the oligonucleotide upstream process

An oligonucleotide facility must safely handle the large quantities of flammable solvents required. Once these solvents are used, they are removed as hazardous waste. In addition, systems using fire-safe valves, interlocks, and single-pass airflows need to be in place to minimize the risk of fire and contain potential solvent spills. Any electrical components used in areas with these solvents also require proper classification.


Downstream process with oligonucleotides

The purification process varies among manufacturers, but most use Reverse Phase Chromatography (RPC) and Anion Exchange (AEX) chromatography to separate components, ensuring impurities are removed prior to the concentration process. Depending on the type of process used, either a solvent- or water-based solution is used. Post-purification, the concentration process uses ultrafiltration/diafiltration (UF/DF), followed by lyophilization (freeze drying) of the final substance before the final formulation.


Challenges in the oligonucleotide downstream process

Bacterial or microbial contamination is a significant factor in facility design. Special care is necessary to minimize the danger to workers and the product. Facilities must incorporate aspects of biologic drug production plants to ensure a suitable environment for sterile formulation and fill-finish of the final parenteral oligonucleotide drug product.

Scaling challenges

Thinking long-term when designing an oligonucleotide facility is crucial to getting the most out of it. If you think you will make the same drug in five years, plan for potential expansion during the design phase. You will appreciate this extra work when you need to expand and spend less time and money than if you had no plan.

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Supply chain challenges

The major raw material in oligo-based drug manufacturing is very expensive nucleic acids. Solvents used in this process are extremely hazardous. Manufacturers must provide safe on-site storage and guarantee safe transport to the facility. Designers must ask themselves:

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Contamination and other safety concerns

Worker safety is paramount. While there is no risk of operators contaminating the product during synthesis, workers may be at great risk using the explosive chemicals necessary for the process. Oligonucleotide manufacturers must meet all code requirements to maximize safety.

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Final thoughts

Designing oligonucleotide manufacturing facilities is a challenging prospect and designing them in a way that allows for flexibility and future scalability is even more daunting. However, the work is imperative to developing and distributing innovative therapies that can cure diseases previously thought of as uncurable. New oligonucleotide treatments continue to qualify for regulatory approval, giving hope to patients and those in the healthcare industry.

AUTHOR

Shwetha Ravi Devine

Shwetha Ravi Devine

Lead Process Engineer

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