Seqirus Inc. v ModernaTX, Inc. [2025] APO 15 is a recent Australian Patent Office opposition decision regarding an invention relating to lipid nanoparticle encapsulated nucleic acid vaccines – this technology rose to prominence during the COVID-19 pandemic and remains a fertile area of research, development, and patent protection.

The opposition canvasses many interesting points in relation to Australian practice. This article will focus on one such point – the patent applicant’s specification definition of a claim term and the impact of this definition.

Claim 1 of the opposed application 2015249553 in the name of ModernaTx, Inc broadly relates to a nucleic acid vaccine comprising one or more mRNA polynucleotides having an open reading frame encoding an antigenic polypeptide formulated in a cationic lipid nanoparticle having a particular molar composition of different lipids.

The interpretation of many terms of Claim 1 came under analysis, but the interpretation of the “vaccine” is notable.

The specification of the opposed application defines “vaccine” as follows (paragraph [45] of the decision):

“In the definitions section of the specification, a vaccine is defined as “a biological preparation that improves immunity in the context of a particular disease, disorder or condition.” Under the heading of “Activation of the immune response” the word “vaccine” is defined as referring to “a composition, for example, a substance or preparation that stimulates, induces, causes or improves immunity in an organism, e.g., an animal organism, for example, a mammalian organism (e.g., a human.)… These two definitions share the feature of improving immunity in an organism.”

There was some dispute between experts for the Opponent and Applicant regarding the scope of “vaccine”.

The Opponent’s expert asserted that the term “vaccine” must be given a narrow interpretation in accordance with the term as used in the art and as follows (at paragraphs [41] and [42]):

“…provide functional and protective immunity in a subject following its administration, or improve existing immunity, and not just induce a potentially low level or transient immune response as might be achieved by any administered mRNA composition following protein expression… ‘true’ vaccine in that it must produce a protective immune response generating immunological memory in a subject and not just some small, non-protective or very transient immune response…”

Although the Opponent’s interpretation of the term is narrow, it does create a high burden as induction of a protective immune response that generates immunological memory is a difficulty for the immune system.

The Applicant’s expert disagreed with the Opponent’s interpretation, asserting that a broader interpretation is appropriate (paragraph [43]):

“…I do not believe it is or was ever regarded in the field that something to be regarded as a “vaccine”, there must be immunological memory generated. This is overly narrow and at odds with what is accepted in the field. Certainly a vaccine must elicit an immune response, but that does not need to extend to long-term immunological memory.”

The issue of immunological memory remained a point of contention for the Opponent’s expert in their evidence in reply (at paragraph [44]):

“Any formulation which is suggested to provide protection against an antigen but which does not result in immunological memory … could not properly be termed a vaccine. A vaccine absolutely requires immunological memory and, indeed, is largely the point of vaccinating a population against pathogens such as the influenza virus in advance of the ‘flu season’.”

Ultimately, the Hearing Officer deferred to the definition in the specification pursuant to jurisprudence, namely a vaccine is a composition that improves immunity. That is, a vaccine within the context of the opposed application does not need to result in immunological memory.

This broad definition-based construction of the term was in the Applicant’s favour in the following ways.

One of the Opponent’s arguments regarding lack of sufficiency was that a person of skill in the art could not perform the invention across the full scope of Claim 1 without undue burden due to the amount of experimentation required to test for an “efficacious vaccine” or providing for a “protective immune response”. That is, at paragraph [268]:

The opposed application does not teach how to select within the broad parameters and vast combinations encompassed by claim 1 to obtain in every instance a vaccine which provides for a protective immune response to the relevant disease as it would involve more than mere trial and error in light of the number of alternative components of the LNP and ratios of those components.

In light of the Hearing Officer’s interpretation of “vaccine”, which is a lower bar than producing “an efficacious vaccine”, this aspect of the Opponent’s sufficiency argument was not successful.

The Opponent raised a lack of utility attack against Claim 1 of the opposed application. Under Australian law, a requirement for patentability is that an invention must be useful. This concept was summarised in Artcraft Urban Group Pty Ltd v Streetworx Pty Ltd [2016] FCAFC 29 at paragraph [121]:

“…the two questions are: first, what is the promise of the invention derived from the whole of the specification?; second, by following the teaching of the specification, does the invention, as claimed in the patent, attain the result promised for it by the patentee?… Further, ‘everything’ that is within the scope of a claim must be useful, that is, attain the result promised for the invention by the patentee.”

In general, it can be challenging to succeed on this ground of invalidity as, ultimately, lack of utility is a question of fact and evidence, and not mere speculation or argument.

Indeed, the Opponent’s inutility argument was somewhat convoluted and speculative. The Opponent relied upon an unsuccessful clinical trial of a similar vaccine technology using lipid nanoparticle-mRNA approach of an unrelated third party to assert that the vaccine of Claim 1 lacked utility. In the Opponent’s view, this clinical trial failure was an “an indication of the significant difficulty in successfully formulating mRNA in LNPs” (paragraph [334]). An expert for the Opponent also commented that an mRNA vaccine employing a specific cationic lipid that fell within the scope of Claim 1 did not work effectively as a functional, protective commercial vaccine.

Once again, the definition of “vaccine” adopted by the Hearing Officer was favourable to the patent applicant. According to this definition, a vaccine formulation of Claim 1 need only produce an immune response and not necessarily be a commercial vaccine. After consideration of the specification as a whole, the Hearing Officer considered the promise of the invention to be “a composition comprising a mRNA encoding an antigenic polypeptide formulated in a LNP having the components in the molar ratios as defined in claim 1, will function as a vaccine (i.e. will produce an antigen specific immune response)”. There was no evidence adduced by the Opponent that a formulation falling within the scope of Claim 1 could not meet this promise, which is a lower bar than production of a commercial vaccine. Claim 1 and claims dependent therefrom were found to be useful.

Seqirus is an example of how a term definition in the specification can work in favour of the patent applicant. However, at the other end of the spectrum is the now infamous Federal Court Decision in Merck Sharp & Dohme Corporation v Wyeth LLC (No 3) [2020] FCA 1477 where the inclusive definition of the term “comprising” as it appeared in the patent specification ultimately led to a finding of lack of claim support.

It is a well-worn truism that a patent applicant can be their own lexicographer and define or redefine terms to suit their requirements. Defining a term can either narrow or broaden scope of protection. The cases touched on above highlight that this can be a double-edged sword and also, in Australia, a claim integer that is expressly defined in the specification will be afforded the definition that the patent applicant has chosen.