Perindopril Patent Confirmed Invalid on Appeal

In a recent decision, the Australian Full Federal Court has dismissed an appeal by Servier regarding the invalidity finding for Australian patent 2003200700 directed to an arginine salt of perindopril.   The Full Court upheld the decision at first instance that the patent did not disclose the best method of performing the invention.  It was found that the specification referred to an ‘umbrella’ technique and did not provide the best technique known to Servier.   As a result, the patent was found to be invalid on the basis that it failed to meet the best method requirement of the Australian Patents Act 1990.

Decision at first instance
Apotex Pty Ltd v Servier Laboratories (Aust) Pty Ltd [2013] FCA 1426 (24 December 2013)

The patent in consideration, AU2003200700 addressed the instability issues associated with known perindopril compositions.  More specifically, the patent claimed the arginine salt of perindopril, which was found to have increased stability.  The specification further described that the perindopril arginine possessed particular stability advantages in heat and humidity which resulted in an extended shelf life.  It was also stated that as a result of the increased longevity of the product, less expensive forms of packaging could be used.

The method for making perindopril arginine as described in the specification was limited to a single sentence, namely that perindopril arginine ‘has been prepared according to a classical method of salification of organic chemistry’.   It was noted during the trial there are numerous methods for forming perindopril arginine salt (all encompassed by the ‘classical method of salification’ disclosure) and that the stability of the product will vary with the salt formed.

At the time of filing, two salification methods were employed by Servier – the ‘1986 method’ and the ‘1991 method’, neither of which were disclosed in the patent.   The trial evidence found that the salification method variables, such as the solvent used and stirring variations, affected the properties of the resulting perindopril salt.  In turn, the variations in the salt were found to alter the stability of the product.

It was agreed that the limited method description was ‘pregnant with ambiguity’ and the trial Judge found at 179 that:

‘The mere reference to utilising a classical method of salification was wholly inadequate to describe the best method, or any substantive content of any particular classical method that the patentee knew of performing the invention. The generalised and unspecific description of the method in the complete specification left too much to chance for a skilled addressee to select from in order to perform the invention. .…….. The bare description “a classical method of salification” does not allow the skilled addressee to follow a routine process of deduction from that description because it leaves open too many variables.’

As such, the Court concluded that Servier had not disclosed the best method known to it of performing the invention.  The patent was subsequently found be invalid for failure to meet the best method requirement.

Amendment after grant

In response to the Federal court decision, Servier sought leave to amend the specification after grant to include the 1986 and 1991 methods for making perindopril arginine and therefore satisfy the best method requirement.   The allowance of such an amendment is at the discretion of the court and the judge exercised this discretion in refusing Servier leave to amend.

The decision was primarily based on correspondence between Servier’s Australian patent attorney and the patent director at Servier at the time the patent application was in prosecution.  Particularly, Servier’s patent attorney made recommendations to include a method for the manufacture of perindopril arginine, a recommendation which was apparently not heeded by Servier.  The court found Servier’s decision to ignore the advice of their patent attorney to be unreasonable and the application to amend was accordingly refused.

Full Federal Court Appeal
Les Laboratoires Servier (Servier) v Apotex Pty Ltd (Apotex) [2016] FCAFC 27

Servier appealed to the Full Federal Court, arguing that as the best method requirement was encompassed by the sufficiency requirement.  It was therefore satisfied, as sufficiency of the patent was not challenged.  Servier further argued that the best method requirement was already satisfied by the identification of perindopril arginine and, therefore, that the best method for producing the compound was not necessary.

On appeal, the Full Court upheld the decision at first instance.  The Court found that sufficiency and best method obligations are separate requirements, reasoning that if additional information regarding the best method is not included in a specification, it could place the patentee in an advantageous commercial position.  It was found at 135 that:

‘Accepting that there was no lack of sufficiency, the mere fact that a complete specification described a method which conveyed sufficient information to a skilled addressee to enable him or her to work the invention does not necessarily satisfy the Patentee’s additional obligation to describe the best method. The patentee has an obligation to include aspects of the method of manufacture that are material to the advantages it is claimed the invention brings.’

The Court disagreed that the best method requirement was satisfied on account of the nature of the invention, namely that the increased stability of perindopril arginine was dependent on the salt formed. It was further found at 134 that:

‘If Servier knew of a method that provides a form of the salt with the characteristics exemplified in the Patent, which characteristics provided the stated advantages of the invention over the prior art, it was incumbent on it to provide that method.  This would relieve the skilled worker from making the choices within those necessarily made or available in a classical salification. The disclosure of the method known to Servier would not only have relieved the skilled addressee of confronting blind alleys and pitfalls which may not be uncommon in a general sense but also, and importantly, would tell the skilled addressee the methodology to achieve the form that obtains the result which constitutes the invention, that is increased stability and storage length.’

Servier’s appeal was therefore dismissed and the patent held invalid for failure to satisfy the best method requirement.

Servier has applied to the High Court of Australia for special leave to appeal the judgement of the Full Court.  In the meantime, the interlocutory injunction restraining the generic manufacturers from entering the market remains in place.

This case has shed new light on the requirement in Australia to provide in the specification the best method known to the patentee of performing the invention.  The case suggests that the best method of preparing a product should be included, even when the claims are directed to the product itself.   Importantly, it was also suggested that amendment after grant to include the best method may be possible, although this is at the discretion of the Court.  It should also be noted, that amendment of a patent specification filed after 15 April 2013 cannot expand the scope beyond that disclosed in the document as originally filed.   Finally, this decision should encourage litigators to seek discovery of known methods not included in the specification.

This article was written by Dr. Ellen Reid

If you have any specific enquiries about this decision, please contact Debra Tulloch or Paul Jones.