Full Court Rejects Inventive Step Attack on Veterinary Formulation Patent

In Boehringer Ingelheim Animal Health USA Inc v Intervet International BV 2022 FCAFC 88 the Full Court dismissed Boehringer’s appeal of the primary Judge’s rejection of Boehringer’s opposition to Intervet’s patent application on the basis of lack of inventive step.

Intervet’s patent application relates to injectable formulations of a macrocyclic lactone and levamisole and their use for controlling parasites and has a priority date of 24th June 2010. As examination was requested several days before the 15th April 2013 commencement of the Intellectual Property Laws Amendment (Raising the Bar) Act 2012, the case applied the pre-Raising the Bar test for inventive step.

The use of macrocyclic lactones for controlling parasites in animals was well known, but there were concerns around the emergence of resistant strains of parasites. Similarly, the use of levamisole as an anti-parasitic was also well known. While macrocyclic lactones and levamisole had been co-administered, attempts to formulate a stable combination of those active ingredients had been unsuccessful for several reasons including: they tend to react with each other when combined; they are individually stable at different pH ranges; and differences in solubility profiles. Those skilled in the art recognised that a stable formulation for such a combination would be desirable in relation to the concerns around resistant strains of parasites. Intervet’s patent application alleges to solve that formulation problem by using a macrocyclic lactone solution formulation comprising levamisole in a particulate form in a non-aqueous solvent system. Claim 1 defines the invention as follows:

An injectable formulation of a macrocyclic lactone and levamisole in a non-aqueous solvent system comprising oil and an organic solvent, wherein the macrocyclic lactone is in solution and the levamisole is a salt in a particulate form, and wherein the levamisole salt is present in the range of between 10-35% w/v.

The trial Judge found that the person skilled in the art to which the patent application was directed consisted of a team with experience in the field of animal health including a pharmaceutical formulator and parasitology expert. An expert giving evidence for Boehringer claimed that it would have been obvious to make a suspension formulation in which the macrocyclic lactone is in solution and the levamisole HCl is in particulate form, making routine adjustments to enhance viscosity, and that he would expect such a formulation to be stable. Intervet’s expert counter responded that the use of a suspension could affect the release profile of the levamisole in the formulation and that there could be issues with achieving even dispersion or preventing agglomeration. It was also noted that in a 2005 patent application Boehringer’s above noted expert made a statement about the difficulty of making liquid formulations containing mixtures across different classes of active compounds.

The trial Judge rejected Boehringer’s expert’s lack of inventive step pleading for several reasons including: the departure from existing formulations; the lack of commercially available formulations; the above noted differences between the actives; Boehringer’s expert’s claims to the contrary were essentially speculative and unlikely to be established by way of routine testing; uncertainty as to the efficacy of levamisole in such a formulation; and long-standing need for such a formulation.

Boehringer also argued for lack of inventive step on the basis of a prior Chinese patent application in combination with the common general knowledge. The trial Judge also rejected that attack on inventive step, finding that the patent application: did not address stability issues or provide the skilled addressee assistance in addressing the known incompatibilities; and did not specify whether the levamisole would be in particulate form.

On appeal Boehringer contended that the trial Judge erred in rejecting its first inventive step attack. Given that claim 1 does not require a formulation within its scope to have any particular release profile or absorption rate or other measure of efficacy, Boehringer contended that the trial Judge gave too much emphasis to the uncertainty as to the efficacy of levamisole in such a formulation and point away from its adoption. The Full Court disagreed, finding that the trial Judge rightly recognised that for pharmaceutical compositions the skilled team would be seeking a formulation that is safe and efficacious. Boehringer also argued that the trial Judge wrongly held that the invention could be arrived at through routine testing. The Full Court disagreed finding the testing involved would be exploratory rather than confirmatory in nature and more importantly it was the selection of the formulation that was inventive, irrespective of the routineness or otherwise of testing it. Boehringer sought to downplay the formulation difficulties acknowledged in the above noted 2005 patent application by arguing that a different approach may have been taken by that expert in 2010. However, this too was rejected as there was no evidence to support that contention.

Regarding the trial Judge’s rejection of Boehringer’s second inventive step attack the Full Court found no error in the trial Judge’s conclusions. While the Chinese patent application qualified as prior art, it was found the notional skilled team would derive little assistance or expectation of success from it given its lack of stability or efficacy data. Nor did it contain information from which the skilled reader could infer whether the levamisole was present in particulate form or in solution.

As earlier noted the opposition to the related New Zealand patent application was also unsuccessful. That opposition was not appealed beyond the Assistant Commissioner’s decision. Given that the New Zealand opposition was conducted under the provisions of the now repealed Patents Act 1953 establishing lack of inventive step was harder than under the Australian pre-Raising the Bar legislation.

Author: Quinn Miller

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