Enablement by reference to “plausibility” and “undue burden”: Lessons for European and US Pharmaceutical Patent Applicants filing Australian Patents

The requirements under Australian Patent law to demonstrate enablement of a patent claim across its full scope was enshrined in Australian law with the IP Laws Amendment (Raising the Bar) Act 2012 that came into effect on 15 April 2013. The “enablement” requirement in Australian practice is very similar to the “sufficiency” requirement imposed in Europe.

Section 40(2)(a) of the Patents Act 1990 requires that the claimed invention be described in a manner which is clear enough and complete enough for the invention to be performed by a person skilled in the relevant art, support pursuant to section 40(3).support pursuant to section 40(3).

The issue of enablement in Australia was first discussed in Evolva SA [2017] APO 57 (14 November 2017), in which the Delegate of the Patent Office indicated that enablement would be assessed by reference to “plausibility” and “undue burden” after construing the scope of the invention defined in the claims and the disclosure of the specification. The enquiry involves asking the following questions:

   Is it plausible that the invention can be worked across the full scope of the claim?

   Can the invention be performed across the full scope of the claim without undue burden?

The above approach was affirmed by the Federal Court in Cytec Industries Inc. v Nalco Company [2021] FCA 970

In this recent decision Boehringer Ingelheim Animal Health USA Inc. v Zoetis Services LLC [2022] APO 42 (23 June 2022), IP Australia has used the above test to provide guidance on how to assess enablement especially in the context of pharmaceutical patents. This decision is for an opposition to a pharmaceutical patent.

Scope of the Main Independent Claim

gloved hand holding vaccine The only independent claim in the subject application was for a method of treating a dog for canine diseases comprising administering to the dog therapeutically effective amounts of vaccine, wherein the vaccine comprises either (i) CDV antigen, CAV-2 antigen and CPV antigen, and one or more of CPI virus antigen and CCV antigen, or (ii) one of more bacterial antigens selected from Leptospira canicolaL. grippotyphosaL. icterohaemorrhagiaeL. PomonaL. Bratislava and Bordetella bronchiseptica, or (iii) both.

In simpler terms, the above claim is to a method of treating a dog for canine disease comprising administering to the dog therapeutically effective amounts of a specific vaccine. The specific vaccine comprises viral antigens, a bacterin, or both, and the vaccine is administered subcutaneously or orally in a first dose, orally in a second dose, and orally in one or more annual doses.

What did the Examples in the Patent Specification Disclose?

  • Antibody titres to CDV antigen, CPV antigen and CAV-1 antigen in a canine in response to a vaccine administered subcutaneously in a first dose, then orally in a second and third dose (Example 1)
  • Seroconversion in a canine in response to CPV, CDV and CAV-1 antigens delivered (i) both subcutaneously in a first dose, then orally in a second and third dose, or (ii) orally in all three doses (Example 2)
  • Formulation of various canine combination vaccines (Examples 3-6)


Was the Plausibility Test satisfied?

The opponent submitted that the specification did not include any data in Example 2 as to antibody titres, rather seroconversion was used as a de-facto measure of protection and therefore the application did not demonstrate effectiveness. The applicant’s witness submitted that seroconversion was initially used in many vaccine trials to provide early indications that the vaccine stimulated the immune system and that there was a very high correlation between antibody levels and protection from challenge for CAV, CDV and CPV.

In the end, it was found that the opponent’s evidence failed to establish that it is not plausible that the seroconversion data provided in Table 5 could be used as a de-facto measure of protection. In other words, the plausibility threshold was found to be met.

Another issue related to the specification that was considered related to the Insufficient Response to CDV. The Opponent’s challenge focused on data in the specification showing seroconversion in 6 of 13 dogs as being inadequate to show that use of only oral vaccinations, as claimed, was feasible. Once again, the delegate was convinced by the Opponent’s evidence and indicated that while the data may not be optimal it at least demonstrated plausibility.

The opponent also challenged the plausibility of the claimed invention by relying on the data showing the results for subcutaneous dosing of the CAV-1 antigen. There were no examples to show that the plausibility of the claimed invention which also claimed oral dosage of the CAV-1 antigen. In this regard, the Delegate referred to other parts of the specification in which data for seroconversion using oral dosage forms had been provided. The Hearing Officer indicated that the date from these other parts in conjunction with the subcutaneous data demonstrated plausibility for oral dosage forms only.

The opponent made a further argument that the tested antigen was CAV-1, yet the claims (and Examples 1 and 2) related to CAV-2. In this regard, it was found that other parts of the specification stated that animals vaccinated with CAV-2 generate antibodies cross-reactive with CAV-1 and as such results for CAV-1 did demonstrate plausibility for CAV-2.

In a further argument, the Opponent argued that the specification only provided evidence for the effectiveness of bacterins combined with CDV, CPV and CAV in an orally administered vaccination regime. In contrast, the broadest claim included within its scope a vaccine included bacterins alone. It was on the basis of this argument alone that the plausibility test was not found to be satisfied. The applicant’s evidence suggested that some of the bacterins have been known for some time including some specific knowledge of the delivery of one of the bacterins intranasally, the Delegate was not convinced. Specifically, it was found that the specification did not indicate plausibility of the B. bronchiseptica and Leptispora antigens.

Was there undue burden to perform the invention across its full scope?

The main challenge mounted by the Opponent revolved around breaking up the independent claim into the various combinations and pointing out that there would be undue burden on the skilled person to understand the effectiveness of all these combinations of viral antigens and baceterins.  

The Delegate concluded that the evidence supported a conclusion that the proof of concept was demonstrated for oral vaccination with CDV, CPV and CAV-1(CAV-2) antigens.  The fact that some further optimisation may be required with respect to dosages was not considered to present an undue burden on the skilled person. 

The Delegate also concluded that embodiments of the claimed invention including CPI, CCV, B. bronchiseptica and Leptispora antigens, did not meet full disclosure requirements of s 40(2)(a) of the Patents Act because these embodiments were implausible and/or presented an undue burden.

Lack of Support

A successful challenge on Enablement usually results in a finding of lack of support. In this regard, the Delegate concluded that any claimed embodiments calling for the vaccine to comprise either of a) CPI or b) CCV or any of the six claimed bacterins were not supported by the specification.

The decision reaffirmed that the support requirement “does not universally require “demonstration” by experimental data or testing across the full breadth of the claims”.  However, in this instance, the patent specification did not provide any data to support whether the antigens other than CDV, CAV-1(CAV-2) and CPV, or any of the bacterins, would be able to effectively treat a canine using the defined oral vaccination regime.

The Delegate concluded any combination of features of the independent claim that encompasses CPI, CCV or any of the defined bacterin antigens, it was broader than the applicant’s technical contribution to the art and so did not satisfy the support requirement.

Amendment for Curing Lack of Enablement and Support

It is important to note that the entire claim was not found to be lacking in enablement or support and it will be reasonably straightforward to amend the independent claim to delete any features that CPI, CCV or any of the six bacterin antigens.

Lessons for Pharmaceutical Patent Applicants

The “support” requirement has a greater threshold when compared to the “enablement” requirement. While expert evidence can address some of the questions on “enablement” it is more difficult if not impossible to rely on expert evidence when arguing “support”. The specification should ideally describe the broadly claimed embodiment in the specification. The requirement of support can be summarised as requiring that the scope of the claims “should correspond to the technical contribution to the art”.

This decision demonstrates that:

  • The plausibility threshold is relatively low, although the threshold has increased beyond speculation or mere assertion and this decision confirms a higher threshold for determining plausibility. Disclosing aprincipal of general application or underlying mechanism that applies across the full scope of the claims can provide strong basis for plausibility.
  • Plausibility should be considered based on the specification at the filing date of the specification. Lack of enablement cannot be rectified by post-filed data. In the case of a divisional application, plausibility of the new claims for the divisional application must be assessed as of the filing date of the divisional application.


A Declaration from an expert on what would be considered plausible, based on the information in the specifications as understood at the filing date, can be highly persuasive in establishing plausibility. However, the “support” requirement is not remedied by such a declaration.

As a concluding remark, we wish to point out that the Australian enablement test as applied by the Australian Patent Office continues to evolve in view of UK jurisprudence and the most recent court decision (in Cytec Industries Inc. v Nalco Company [2021] FCA 970) and this decision by IP Australia confirms the importance of avoiding overreach when drafting patent claims. In the case of divisional applications, it is important to ensure that the claims of the divisional application find support and are exemplified in the specification as filed across the entire claim scope.

written by Andy Mukherji, Principal



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