| Date of decision: | 24 September 2025 |
| Body: | Federal Court |
| Adjudicator: |
Justice Jackman |
Introduction
Justice Jackman of the Federal Court has handed down judgment in proceedings between Abbey Laboratories Pty Ltd. (Abbey) and Virbac Australia Pty Ltd (Virbac), in a dispute concerning Virbac’s patent for a veterinary topical pour-on formulation for cattle containing macrocyclic lactone and levamisole. Justice Jackman found that the majority of the patent’s claims were valid and infringed by Abbey, while three claims concerning viscosity modifiers were found invalid for lack of inventive step.
Background
The patent, AU2012227241 entitled “Veterinary Topical Formulation” with a priority date of 23 September 2011 (the 241 Patent), relates to anthelmintic formulations for treating parasitic infections in cattle. Anthelmintics are products used to treat parasites in livestock, an important aspect of modern livestock farming.
The specification identifies five major classes of broad spectrum anthelmintic. Of these, macrocyclic lactones, introduced in the 1980s, are described as the most potent killers of worms with a unique quality of also killing external parasites such as lice, mites and ticks. The 241 Patent addresses the challenge of formulating a stable combination of macrocyclic lactones and levamisole in a pour-on formulation, which is ordinarily difficult given their different physicochemical properties. The invention claimed stable formulations using specific non-aqueous solvents, namely dimethyl acetamide (DMA), dimethyl isosorbide (DMI), diethyl phthalate (DEP) and dimethyl phthalate (DMP).
Abbey commenced revocation proceedings in May 2024 and subsequently launched its competing product, Levamox Duo, in January 2025, after an interlocutory injunction was refused in December 2024 on balance of convenience grounds. Virbac cross-claimed for infringement. There was no dispute that if the Patent was valid, Abbey had infringed by offering to sell and supplying Levamox Duo in Australia.
Key Issues and Consideration
Inventive Step
Abbey challenged claims 1-10, 13, 15, 16, 18-21 on lack of inventive step. Claim 1 is as follows (with integers identified):
1.1 A stable formulation including
1.1(a) a levamisole active ingredient and
1.1(b) at least one active selected from the group known as macrocyclic lactones
1.2 with both of said actives being dissolved in a non-aqueous system, including solvents selected from DMA, DMI, DEP and DMP
1.3 wherein the formulation is a topical formulation for administration
1.4 to cattle
Abbey had initially also challenged claims 11 and 12 (relating to additional anthelmintics such as triclabendazole), but abandoned that challenge.
Abbey’s inventive step challenge focused on two key propositions: that a person skilled in the art (PSA), would obviously adopt a non-aqueous solvent system, and that the PSA would select one of the four specified solvents. Both these challenges failed.
Abbey’s expert, Dr Alawi (a pharmaceutical formulator with extensive experience in the animal health industry, including as co-inventor on competing patents), gave evidence that using a non-aqueous system was “the usual approach” for dissolving lipophilic molecules and that including water would be “unusual and a waste of time”. However, Justice Jackman found that Dr Alawi’s evidence was based on his own specialised research experience rather than the common general knowledge. Critically, Dr Alawi’s position was contradicted by his own prior conduct. In developing the invention the subject of New Zealand patent NZ 20060552040 (the 040 Patent), Dr Alawi had tested twelve aqueous formulations combining abamectin and levamisole. More significantly, for another patent in the same field filed just three months before the 241 Patent’s priority date, Dr Alawi had trialled over forty formulations with eleven out of thirteen test formulations using water and various salt forms of levamisole.
Justice Jackman accepted evidence from Virbac’s expert, Professor Bunt, that a PSA would not exclude water from consideration without first testing. Professor Bunt explained that water and water-based solvents are generally safer on animals, easier to formulate and less expensive than organic solvents. Professor Bunt considered that he would have begun testing levamisole’s solubility in water across different pH values, prioritising the salt form of levamisole as salts are the most water-soluble form of a compound. Dr Alawi admitted in cross-examination that someone who had not conducted his research program would say: “Okay. Let’s try the water” and “let’s try the levamisole … hydrochloride format”.
The Court also considered whether the PSA would have selected any of the four solvents specified in claim 1 (namely, DMA, DMI, DEP and DMP). Database search evidence relied upon by Virbac showed that DMI, DEP and DMP were not used in any veterinary product at the priority date, and DMA appeared in only one product.
Professor Bunt gave evidence that DMA would have been an unlikely choice due to its known skin irritancy, distinct unpleasant odour, being water-miscible and quite fluid, causing run-off concerns, links to reproductive and developmental toxicity, flammability concerns, and potential regulatory difficulties given its limited prior use in veterinary products.
As to DMI, Professor Bunt had never used it, did not keep it in his ‘library’ of solvents, was not aware of others using it for veterinary formulations, and noted concerns about regulatory approval and cost. Dr Alawi had not used DMI in any of his prior research work for various patents, explaining he included it in his solvent list as a “back up”. The Court rejected this explanation, finding the most plausible explanation was that Dr Alawi’s awareness of Virbac’s Cydectin Platinum product led him to include DMI in his list.
As to the phthalates (DEP and DMP), Dr Alawi had not used them in his work for the 040 Patent but listed them as a “back up”. Neither Dr Alawi, Dr Agnew nor the database search evidence identified any veterinary products using phthalates. Professor Bunt said it had never been his preference to consider a phthalate when other materials could function just as well.
Justice Jackman accepted Professor Bunt’s list of preferred solvents for the hypothetical task, which in order of preference were: water, PEGs; propylene glycol; glycerol formal; ethanol; benzyl alcohol; methyl ethyl ketone; and NMP – none of which were the solvents listed in claim 1.
Accordingly, his Honour held that it was not obvious that the PSA would adopt a non-aqueous solvent system, nor would the PSA select any of the four solvents listed in claim 1. Abbey’s inventive step challenge to claim 1 and its dependent claims (claims 2-10, 13, 15) therefore failed.
As to the independent claim 16 (a method of preparation claim requiring dissolving actives in at least one of DMI, DMA, DEP or DMP), as the selection of those solvents was not obvious, his Honour also found this claim to be inventive.
However, claim 19 (a solvent-based topical formulation containing a macrocyclic lactone and levamisole in organic solvents with a viscosity modifier) did not require the use of DMI, DMA, DEP or DMP, but merely the use of one or more organic solvents together with a viscosity modifier. Professor Bunt’s choice of potential solvents included a number of organic solvents, and his Honour considered that there was nothing inventive about the use of organic solvents in this kind of formulation. The addition of viscosity modifiers was also common practice within the industry as at the priority date of the 241 Patent – 23 September 2011. Justice Jackman consequently found claim 19 lacked an inventive step and was invalid. Claims 20 and 21, being dependant on claim 19, and merely stipulating the concentration and type of viscosity modifier, were also invalid.
Abbey also relied on three pieces of prior art information in its inventive step challenge. However, his Honour found these documents did not indicate that the development of an anthelmintic combination formulation for cattle should only use a non-aqueous system, nor did they identify any of the solvents specifically nominated in the 241 Patent for pour-on formulations.
Novelty
Abbey relied on a “whole of contents” novelty objection based on Australian patent AU2011234984 (the 984 Patent), directed to compositions comprising four different active agents (1–arylpyrazole, a macrocyclic lactone, an insect growth regulator, and an anthelmintic) for treating parasites.
A preliminary issue arose as to whether Abbey needed to formulate a set of “notional claims” to establish anticipation. Since EI Du Pont de Nemours and Co v ICI Chemicals & Polymers Ltd [2005] FCA 892; (2005) 66 IPR 462 (Du Pont), it had been understood that a “whole of contents” objection required formulating notional claims that would be fairly based on the prior disclosure.
Justice Jackman declined to follow Du Pont, stating that its reasoning was “wrong”. The statutory language – “if the information … were to be, the subject of a claim” – does not require information to actually be drafted as a claim. The legislative history showed the “whole of contents” approach was introduced in response to the Industrial Property Advisory Committee’s recommendation to replace the “unsatisfactory” and “too narrow” prior claiming approach with a “simpler mechanism”. Requiring notional claims would “re-re-route Australian patent law back towards something resembling prior claiming … but in an even more obscure form”.
His Honour also observed that, when considering whether to depart from earlier single judge decisions, a Judge should not approach such a task through the lens of “judicial comity”, a term which “creates the unfortunate impression that judges should give priority to questions of courtesy and politeness to each other over their duty to apply the law as properly understood”. Instead, the question is whether there is a “compelling reason” to depart, rather than whether the earlier decision was “plainly” or “clearly” wrong.
Comparison with the 984 Patent
Turning to the comparison between the 241 Patent and the 984 Patent, Justice Jackman found there was no “clear and unmistakable direction” in the 984 Patent to make any formulation within the claims of the 241 Patent. The 984 Patent required four active ingredients (whereas the Patent required two); listed levamisole as merely one of sixteen possible anthelmintic options; expressly encompassed aqueous formulations (the 241 Patent required non-aqueous); and listed DMA and DMI among over 25 solvents without preference or specific combination with levamisole. Abbey’s approach of finding isolated references to individual claim features in different parts of the 984 Patent was rejected as failing to anticipate the specific combinations claimed.
Ferrocom Inferences
Abbey submitted that adverse inferences should be drawn under Commercial Union Assurance Company of Australia Ltd v Ferrcom Pty Ltd (1991) 22 NSWLR 389 (Ferrcom) from matters Virbac’s expert, Professor Bunt, had not addressed in evidence in chief – specifically, the obviousness of the solvent concentration ranges in claim 2. Justice Jackman rejected this as “misplaced” as Professor Bunt had already explained that he would not have selected the relevant solvents in the first place, so there was no need for him to address the concentration ranges of solvents he would not have chosen.
More fundamentally, his Honour held that there would “rarely (if ever)” be scope for such an inference in contemporary expert evidence practice, given the requirement for expert conferences, joint reports, and declarations that all appropriate inquiries have been made. These safeguards mean “contemporary practice thus does not leave any effective room for a party tactically to seek to ensure that certain subject matter is avoided by an expert witness”.
Outcome and Implications
Justice Jackman found that Abbey had infringed claims 1-10, 13, 15, 16 and 18, and granted an injunction preventing the sale of Levamox Duo, with an inquiry on costs to follow. His Honour found claims 19-21 invalid. Abbey has subsequently appealed the decision.
Justice Jackson’s decision demonstrates the importance of ensuring that an expert’s opinion on the issue of inventive step is based on the CGK and not knowledge specific to that particular expert which is not representative of the CGK. His Honour’s judgment also illustrates the power of prior patents and publications to corroborate or dispute the approach which PSAs would have taken to research around the time of the priority date.
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