Protecting therapeutic nucleic acids in Australia

Therapeutic nucleic acids are no longer a niche technology. Antisense oligonucleotides (ASOs), siRNAs and related RNA-based medicines now form a commercially important class of therapeutics, with expanding clinical pipelines and a growing number of approved products. Additionally, while these molecules were traditionally developed for orphan indications, this has changed in more recent times with molecules in development to compete with established small molecules or large molecules. The estimated market size for ASOs, RNAi and siRNAs was about USD7.2 billion in 2025 and is expected to grow to about USD29.6 billion in 2033.¹ For companies developing these medicines, Australia offers a generally favourable patent environment. However, Australian law also presents distinctive challenges, particularly for inventions involving nucleic acid sequences.

Patentable subject matter

Following D'Arcy v Myriad Genetics decision (D’Arcy v Myriad Genetics Inc. (2015) HCA 35), there was a fear that nucleic acid-based inventions may be unpatentable in Australia. However, the High Court in that case made it clear that their decision was not a wholesale ban on the patentability of inventions derived from nature. Instead, the Court favoured a case-by-case approach having regard to the substance of the invention, and not simply the form of the claim under consideration. The High Court also made it clear that they were not considering claims to oligonucleotides.

Subsequent Australian Patent Office decision Arrowhead Research Corporation [2016] APO 70 and Academisch Ziekenhuis Leiden and BioMarin Technologies B.V. [2018] APO 49 have specifically addressed therapeutic nucleic acids and found certain claims to satisfy the requirements for patentable subject matter. In both cases, the patent applications in question faced rejections alleging the substance of the invention was genetic information and not a product. In both cases, the patent office considered how the invention works and how the claimed nucleic acid achieved its purpose. In the Academisch Ziekenhuis Leiden decision, the patent office considered a claims to an ASO having a specified length and comprising modified nucleotides that induced exon skipping in dystrophin. The patent office considered the “manner in which the information embodied in the specific nucleotide sequence is used, and the result of that use, to be significant considerations in determining the substance of the claimed invention” and “the length and presence of [modified nucleotides] of the claimed oligonucleotide are structural features that are significant to the working of the present invention”. However, the patent office did state that “the presence of [modified nucleotides] and/or a variation in the length of an oligonucleotide is not sufficient, in itself, to conclude that the substance of the claimed invention is a chemical compound”.

Perhaps the most important lesson from the Arrowhead and Academisch Ziekenhuis Leiden decisions is that Australian patentable subject matter analysis begins with proper characterisation of the nature of the claimed invention as a whole. This characterisation is based on the following questions

• What, in substance, is the invention?
• Where does the alleged ingenuity reside?
• What has human intervention contributed?

Where the answer is merely the discovery of naturally occurring genetic information, patentability may be problematic. Where the answer is the creation of a new therapeutic molecule through deliberate chemical design, the analysis is very different.

It is clear from these decisions that patent applicants must take care to describe how any claimed therapeutic nucleic acid works and how the structure of the therapeutic nucleic acid confers the activity. While not aspects of the decisions, it will be apparent that the broader the claims, the more difficult it is to establish that the specific structure of a therapeutic nucleic acid (e.g., length or present of modified nucleotides) confers the purported activity. However, applicants will have different options for claiming therapeutic nucleic acids once an activity and the structure conferring that activity has been identified. For example, if it is the binding of an ASO of a specific length to a specific target in a nucleic acid that induced exon skipping, the applicant may be able to claim only those features and then add features of modified bases, etc in subordinate claims or additional application.

Complete disclosure

While patent offices have traditionally taken the view that once a target is known, it is straightforward to make an ASO, siRNA or RNAi against the target, this is not always the case in practice. In fact, even single nucleotide changes can have a substantial effect on the activity of a nucleic acid. These data are useful for establishing non-obviousness of specific therapeutic nucleic acids and even that claims define patentable subject matter (see above). However, these data may also suggest that not everything falling within a broader claim actually works.

The current requirement in Australia for a complete disclosure requires that the specification must provide sufficient information to enable the skilled person to perform the invention over the whole width of the claims, without undue burden or the need for further invention. Obviously, it is more difficult to support claims directed to broad classes of therapeutic nucleic acids, nucleic acids defined only by functional language or large genera of compounds. This is particularly so if the applicant has disclosed data suggesting that not everything within the scope of the claims actually works. This was shown in the case of Seqirus Inc. v ModernaTX, Inc. [2025] APO 15 (23 May 2025), in which a disclosure by Moderna was used to show that not everything within the scope of the claims actually worked and the claims were held invalid.

Of course, applicants need to balance disclosures required to establish non-obviousness versus those required to establish enablement. This tension is not new and is not limited to the Australian context.

Conclusion

While Australia has some quite stringent patentability requirements, these requirements can be reasonably anticipated during the drafting process. Despite the above, broad claims should be accompanied by disclosure explaining why the claimed generalisation is technically justified. In particular including a description establishing what the inventor(s) have produced and how it provides a therapeutic benefit and the technical reasons as to why it is feasible to extrapolate from this to what is claimed should assist with satisfying Australian requirements.