Apotex Pty Ltd v Servier Laboratories (Aust) Pty Ltd FCA 1426
Following a recent Federal Court decision, a Servier patent may be revoked because it failed to disclose the best method of performing the invention known to the applicant at the time of filing. The decision provides a pertinent ‘cautionary tale’ because the Court reached the conclusion that the best method was not disclosed despite expert evidence that:
- the method described in the patent was sufficient for a skilled addressee to produce something within each claim without prolonged study; and
- the absent best method amounted to no more than ‘standard classical procedures’.
The decision is particularly pertinent to foreign pharmaceutical companies because the best method disclosure requirement is generally less significant under the patent laws of major foreign jurisdictions.
A compound known as perindopril lowers blood pressure. A patent for perindopril itself, owned by a Servier entity, expired in 2006.
Servier has also patented a salt of perindopril, known as ‘perindopril erbumine’. Servier marketed a pharmaceutical product with the active ingredient perindopril erbumine under the brand name COVERSYL. In 2006, Servier switched the active ingredient to a more stable salt of perindopril, known as ‘perindopril arginine’.
The subject of the proceedings was Australian Patent No. 2003200700, which is directed to the perindopril salt.
Grounds of Revocation
The generic pharmaceutical manufacturer Apotex sought revocation of the patent on a number of grounds, including that the patent fails to disclose the best method of performing the invention. This update focuses on the best method ground, which was the only ground on which Apotex succeeded.
Under section 40(2) of the Australian Patents Act 1990 (as in force at the relevant time), a patent must ‘describe the invention fully, including the best method known to the applicant of performing the invention’.
The problem addressed by the patent is developing a salt of perindopril having improved stability over the erbumine salt.
Claim 1 is directed to ‘[t]he arginine salt of perindopril and its hydrates’.
The arginine salt, according to the patent specification, ‘has entirely unexpected advantages over all the other salts studied and, more especially, over the [erbumine] salt’.
The patent specification most relevantly discloses, in relation to preparation of the arginine salt: ‘[t]he arginine salt used in this study is the L-arginine salt. It has been prepared according to a classical method of salification of organic chemistry.’
Servier’s Preparation Methods
It emerged in evidence that by the time the patent was filed, Servier’s employees had prepared the arginine salt using at least two different classical salification methods, the first time in 1986 and the second in 1991.
The expert evidence presented to the court included the following:
- The ‘method described in the patent was sufficient for a skilled addressee to produce something within each claim without prolonged study’.
- There was ‘no certainty that any particular method within the range of classical methods, or the variety of choices, such as solvents, duration, or temperatures within a selected method would necessarily produce a crystalline salt or a particular salt form that could be used in a pharmaceutical composition.
- Both the 1986 and 1991 methods employed ‘standard classical procedures’.
- The 1991 method was superior.
Rares J considered that ‘the patent’s disclosure that the arginine salt used in the study had “been prepared according to a classical method of salification” was pregnant with ambiguity’. ‘The complete specification essentially failed to disclose any detail sufficient to provide a skilled addressee with the directions necessary to perform the invention without undertaking potentially extensive trial and error experimentation in refining the choices of parameters and methodologies of classical salification.’
Even though the method described in the patent was sufficient for a skilled addressee to produce something within each claim without prolonged study, it fell short of disclosing the best method, i.e. the method known to the patentee that yielded an arginine salt that could be used in a pharmaceutical composition.
Any Australian patent including claims to a compound or composition risks invalidity unless it discloses the best method known to the patentee of preparing the compound or composition. The patentee must disclose the method in sufficient detail to minimise variables and allow the skilled addressee to perform it without prolonged study. It is well established that the patentee’s knowledge is assessed as at the date on which the patent was filed.