When does a product contain a pharmaceutical substance for the purposes of a patent extension?

By Nicholas Tyacke and Amanda Riethmuller.

Key Points:
The eligibility to apply for a patent term extension, the time period within which to make such an application and the length of any extension granted, are all affected by the date of first inclusion in the ARTG of goods that contain, or consist of, the substance claimed in the patent. A claimed substance is contained within an ARTG registered/listed good if it is contained in any portion, even if it only exists as an impurity.

In the December edition of Life Sciences Insights, we discussed a series of cases that are likely to have a significant impact on the length of some patent term extensions already granted, the eligibility of some patents for extension and the regulatory approval path pursued. Elsewhere in this issue, we provide an update on one of those cases.

This article will discuss an additional issue that may influence the eligibility to apply for a patent term extension, the time period within which such an application must be made, and the length of any extension granted, in view of those decisions. That issue is:

"When does an approved product 'contain' or 'consist of' the substance claimed in the patent that is the subject of the extension application?"

This question was answered by the Federal Court recently in an undefended appeal, and will come before the Court again later this year in a contested dispute.

The patent term extension process

The Patents Act 1990 (Cth) (the "Act") provides a regime for extending the term of a pharmaceutical patent by up to 5 years beyond the standard patent term. In order for a patent to qualify for an extension, it must comply with section 70(3) the Act such that:

• goods "containing or consisting of" the pharmaceutical substance (as disclosed and claimed in the patent) must be included in the Australian Register of Therapeutic Goods ("ARTG"); and
• the period beginning on the date of the patent and ending on the "first regulatory approval date" for the substance must be at least five years.

The Act defines the "first regulatory approval date" in section 70(5) as:

• if no pre-TGA marketing approval was given in relation to the substance — the date of commencement of the first inclusion in the ARTG of goods that "contain, or consist of", the substance; or
• if pre-TGA marketing approval was given in relation to the substance — the date of the first approval.

Section 70(6) defines "pre-TGA marketing approval" in relation to a pharmaceutical substance as an approval (however described) by a Minister, or a Secretary to a Department, to:

• market the substance, or a product containing the substance, in Australia; or
• import into Australia, for general marketing, the substance or a product containing the substance.

The maximum length of an extension is five years. The length of an extension is calculated according to the amount of time between the date of the patent and the earliest first regulatory approval date, reduced (but not below zero) by five years (section 77). The earlier the first regulatory approval date, the shorter the length of the extension.

Section 71 of the Act requires an application for extension to be made within 6 months of the latest of

• the date the patent was granted;
• the "first regulatory approval date"; or
• the date of commencement of section 71.

The question of whether a product "contains or consists of" a pharmaceutical substance claimed in a patent is, therefore, of fundamental importance.

Merck & Co. v Arrow Pharmaceuticals

This case involved an undefended appeal to the Federal Court from the decision of a Delegate of the Commissioner of Patents not to grant Merck & Co Inc ("Merck") an extension of its Australian patent directed to Lovastatin ß-Hydroxy Acid (LHA) ("LHA Patent").[1]

In 2002, Merck had a drug called Mevacor listed on the ARTG. Mevacor contains Lovastatin as its active ingredient. Mevacor also contains LHA, but only as an impurity, making up only 0.2% of the drug. Once Mevacor was listed, Merck applied to the Commissioner of Patents for an extension of term of its LHA Patent, arguing that the presence of LHA in Mevacor, even at a level of only 0.2%, was sufficient to satisfy the requirement of section 70(3) that goods "containing" the substance be included in the ARTG.

Following a rejection of this argument by the Delegate, the Federal Court held on appeal that the LHA Patent satisfied the statutory requirements for extension. Specifically, the Court held that the fact that LHA was present in Mevacor "only in minute quantities" was irrelevant as "the section does not stipulate for any particular quantity or proportion of the substance in the registered goods."

Alphapharm Pty Ltd v H Lundbeck A/S

As discussed in our previous issue, H Lundbeck ("Lundbeck") is currently involved in a series of patent litigations with respect to its 1989 patent covering the (S)-enantiomer of citalopram ("Lundbeck Patent").

On 22 December 2003, Lundbeck applied for an extension of the term of the Lundbeck Patent. In its application for extension, Lundbeck represented that the first goods included on the ARTG containing or consisting of the (S)-enantiomer of citalopram was its product escitalopram oxalate (brand name Lexapro), which was registered on 16 September 2003. On 27 May 2004, the Commissioner granted Lundbeck an extension of the term of that patent until 13 June 2014 on the basis of that application.

Almost 14 months after the Commissioner granted the extension, Alphapharm informed the Commissioner that Cipramil, rather than Lexapro, was the first product included in the ARTG that contained or consisted of the (S)-enantiomer of citalopram. According to Alphapharm, Cipramil (citalopram hydrobromide), the racemic mixture comprised of both the (S)- and (R)- enantiomers of citalopram, was first registered on the ARTG almost six years prior to the registration of escitalopram oxalate.

The Delegate upheld Alphapharm's submission. Specifically, the Delegate held that the racemic mixture that comprised Cipramil "contained" the (S)-enantiomer of citalopram. Lundbeck argued that for the purposes of section70(5)(a), Cipramil could not be considered to "contain or consist of" the pharmaceutical substance escitalopram, as escitalopram is a new chemical entity that has different properties to those of citalopram. It was argued that Cipramil could not be marketed (except as part of the racemic mixture) based on its ARTG registration. The Delegate rejected this argument on the basis that he was bound by the decision in Merck, discussed above.

An appeal from this decision is to be heard in April of this year. This is along with a claim brought by Alphapharm for revocation of six claims of the Lundbeck patent, or an order that the Register be rectified to remove the extension of the term of the Lundbeck patent, and a cross-claim for infringement.

Impact

The eligibility to apply for a patent term extension, the time period within which such an application must be made, and the length of any extension granted, are all affected by the date of first inclusion in the ARTG of goods that "contain, or consist of", the substance claimed in the patent.

As currently interpreted, a good may contain a patented substance for the purpose of these issues if it contains such a substance in any quantity, no matter how small, and irrespective of whether that substance is the active ingredient in the registered/listed good or not.

Based on this interpretation, eligibility for a patent term extension may be lost or the length of an extension reduced because a patented substance that may have been entitled to an extension as an active ingredient of a later approved product existed as an impurity of an earlier approved product.

For further information, please contact Mary Still.