A new class of drugs—short, chemically modified DNA sequences called nucleic acid therapeutics—can now be made using engineered enzymes instead of toxic solvents and expensive reagents. Current chemical synthesis of these drugs requires one tonne of acetonitrile solvent per kilogram of product, yields only about 90% purity, and cannot produce batches larger than 10 kilograms. That was acceptable when these drugs treated only rare diseases in small volumes, but a cholesterol-lowering nucleic acid therapeutic called Inclisiran was recently approved, and hundreds more are in clinical trials for common conditions like heart disease and diabetes. Existing chemical methods simply cannot scale to the tonne-level production these drugs will need. The researchers will use directed evolution to engineer enzymes that tolerate the chemical modifications in these drugs, then combine multiple engineered enzymes to build both the nucleotide building blocks and the final therapeutic molecules. If successful, this biocatalytic platform could produce nucleic acid therapeutics in high purity, at lower cost, and with far less environmental waste—removing a critical bottleneck that currently prevents these drugs from reaching millions of patients with common diseases.
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Proteins control almost all biochemical processes in the human body. These biological macromolecules are encoded in our DNA, which is first transcribed to mRNA and subsequently translated to proteins. Traditional small molecule pharmaceuticals are designed to selectively bind to a target protein in order to modulate its function. While this approach has proven very powerful, there are numerous diseases which are difficult or not possible to treat in this manner. In recent years, a new class of drug molecules called nucleic acid therapeutics (NATs) have emerged which offer a potentially versatile approach for the treatment of a wide range of genetic disorders and diseases. These molecules are short modified DNA sequences which are designed to bind to mRNA and directly modulate the production of disease related proteins. Existing methods of producing NATs rely on chemical synthesis, which requires large excesses of expensive reagents, huge volumes of organic solvent (1 ton of acetonitrile per Kg of product) and deliver the final products with low yield and modest (~90%) purity. Reactions are performed on solid supports or columns, which limits the process scalability meaning that these methods are only suitable for producing oligonucleotides in <10 Kg batches. These limitations have not been a major problem for the manufacture of NATs currently on the market, as these have been limited to the treatment of rare diseases and are therefore produced in low volumes. However, a large volume cholesterol lowering drug called Inclisarin was recently approved and there are several hundred NATs under evaluation in clinical trials for the treatment of common diseases. As current chemical methods are not suitable for the large (tonne) scale synthesis of NATs, it is now essential that we develop new, sustainable, scalable and versatile manufacturing strategies for their production. In this application, we will develop a green, cost-efficient and truly versatile biocatalytic platform for manufacturing NATs and their nucleotide triphosphate (NTP) building blocks. Biocatalysis is an exciting technology which is widely used across the chemical industry, whereby enzymes (nature's own catalysts) are used to convert starting materials into high-value products. Compared to natural DNA, NATs contain chemical modifications which are designed to improve their efficacy, selectivity and metabolic stability. These chemical modifications are not well tolerated by natural enzymes, however using a technology called directed evolution we are able to quickly engineer enzymes to modify their functions and optimise their properties making them suitable for practical applications. We will use combinations of different engineered enzymes to firstly access NTP building blocks, which will be used in subsequent biocatalytic reactions to produce NATs. We will then compare NATs produced using our approaches to those produced with standard chemical approaches, using state of the art analytical techniques combined with biological validation assays. The technologies developed will allow efficient, sustainable and cost-effective manufacturing of NATs in high purity, thus allowing this important new drug modality to realise its full potential for the treatment of a wide-range of diseases.
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