A new method for producing DNA-based therapeutics

By combining enzymatic and chemical techniques, scientists have developed an innovative method for producing synthetic DNA molecules. This new approach opens up numerous perspectives, particularly for the production of large molecules that can be used for future therapies.

The DNA contained in our cells is the molecule carrying genetic information as well as the main support of heredity. It is made up of nucleotides, themselves composed of four nucleic bases, the elementary building blocks of DNA: adenine (A), cytosine (C), guanine (G) and thymine (T). The human genome contains around 3 billion of these letters, forming a sort of book containing the information essential to the functioning of our body.

In addition to its central role in the development and functioning of living beings, DNA is used in extremely varied contexts. Its remarkable stability, for example, allows scientists to retrace the evolutionary history of the human species. This characteristic also makes it possible to consider the use of this molecule as a support for the storage of long-term digital data, the four nucleic bases (A, T, C, G) constituting DNA being able to replace the binary code used until now. ‘now. In a completely different field, several projects are in development to develop diagnostic tools, based on short synthetic DNA sequences, making it possible to better detect various diseases, such as malaria for example.

DNA, mRNA, miRNA: therapies in full swing… but which have limits

In recent years, several therapeutic applications based on nucleic acids – DNA, messenger RNA (mRNA), micro-RNA (miRNA) – have also begun to emerge. The most emblematic example of these new drugs is the mRNA vaccine against SARS-CoV-2 which was used on a very large scale during the Covid-19 pandemic. However, if the first drugs begin to appear, the production of these therapeutic molecules remains delicate. The chemical modifications essential for their proper functioning in the body make their synthesis more complex. For example, the production of therapeutic DNA of more than 100 nucleotides proves extremely difficult with current methods, thus limiting the drug possibilities.

The discovery of microRNAs rewarded with the 2024 Nobel Prize

On October 7, 2024, Victor Ambros and Gary Ruvkun were awarded the Nobel Prize in Medicine and Physiology for their “discovery of microRNAs and their role in post-transcriptional gene regulation”. miRNAs are RNA sequences of around twenty nucleotides that regulate the expression of approximately half of the genes in humans. Despite clinical trials that have so far been unsuccessful, these short RNA fragments represent promising therapeutic avenues for the treatment of certain cancers, cardiovascular or neurodegenerative diseases in particular. “In recent years, great progress has been made in the packaging and modification of RNA molecules, allowing them to be used at smaller doses and in a more targeted manner,” says Marcel Hollenstein. Advances which could lead in the medium term to the first drugs based on miRNA.

Longer modified DNA for new therapeutic possibilities

To overcome these limits, scientists from the Pasteur Institute, Paris Cité University, CNRS and the pharmaceutical company Roche have succeeded in developing an innovative method combining chemical and enzymatic techniques.

“This is a new approach which makes it possible to reduce the current limits in the production of modified therapeutic DNA. We use enzymes called ligases rather than just chemical approaches and we demonstrate that this approach is compatible with short sequences, around twenty nucleotides, but also longer, up to 120 nucleotides,” explains Marcel Hollenstein, head of theBioorganic Chemistry of Nucleic Acids Unit at the Pasteur Institute. To return to the analogy between the book and the genome, this new method opens up the possibility of producing phrases (sequences 120 nucleotides long) where previously it was possible to produce only mots (sequences of a few dozen nucleotides) for therapeutic purposes.

This new method opens up numerous perspectives in the field of therapeutic nucleic acids but also more broadly for biotechnological applications requiring the production of long sequences of modified DNA.

Template-dependent DNA ligation for the synthesis of modified oligonucleotides, Nature communicationsSeptember 13, 2024

Nazarii Sabat1, Andreas Stämpfli2, Steven Hanlon3, Serena Bisagni3, Filippo Sladojevich2, Kurt Püntener3 & Marcel Hollenstein1

1Institut Pasteur, Université Paris Cité, CNRS UMR3523, Department of Structural Biology and Chemistry, Laboratory for Bioorganic Chemistry of Nucleic Acids, 28, rue du Docteur Roux, 75724 Paris, Cedex 15, France.

2Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, Switzerland.

3Pharmaceutical Division, Synthetic Molecules Technical Development, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, Switzerland