In Merck & Co. v. Hi-Tech Pharmacal (06-1401) , the Court of Appeals for the Federal Circuit looked at the question of whether a patent term extension under the Hatch-Waxman Act, 35 U.S.C. § 156, may be applied to a patent subject to a terminal disclaimer under 35 U.S.C. § 253, filed to overcome an obviousness-type double-patenting rejection.

Finding that the language of § 156 is unambiguous and fulfills a purpose unrelated to and not in conflict with that of § 253, the court held that a Hatch-Waxman term extension may be so applied.

Merck had filed a patent application covering carbonic anhydrase inhibitors, including dorzolamide, which is the active ingredient in Trusopt®, a drug used to treat glaucoma..  That patent application eventually issued as United States Patent No. 4,797,413 but during prosecution, the examiner rejected all claims on the ground of obviousness-type double patenting over the claims of an earlier patent owned by Merck, U.S. Patent No. 4,677,115.

To overcome this rejection, Merck filed a terminal disclaimer that disavowed any term of the ’413 patent that would extend beyond June 30, 2004, the original term of the ’115 patent (17 years from its date of issue).  The filing of the terminal disclaimer was accepted by the Examiner and the  patent was granted.

Later, under the Uruguay Round Agreements Act (URAA), patent term was changed to 20 years from the date of filing of the patent application with issued patents getting a term of the greater of 20 years from its earliest effective filing date or 17 years from its date of issue.  The expiration date of the ‘115 patent was reset to December 12, 2004 (twenty years from the filing date of the ’115 patent).  Because the terminal disclaimer linked the expiration date of the ’413 patent to the term of the ’115 patent, the expiration date of the ’413 patent likewise was reset to December 12, 2004.

Merck got approval to market Trusopt, listing the ‘413 patent in the Approved Drug Products with Therapeutic Equivalence Evaluation (the “Orange Book”).   Then the USPTO extended the term of the ’413 patent 1233 days based on the period of regulatory review undertaken by the FDA.

When Hi-Tech Pharmacal filed Abbreviated New Drug Applications for a generic version of a drug containing the active ingredient dorzolamide and used in drops for the treatment of ocular hypertension, it sent a paragraph iv patent certification notice to Merck, stating that Hi-Tech’s generic eye-drops do not infringe the ’413 patent.  In response, Merck sued.

Hi-Tech filed a motion to dismiss on the ground that while its products were covered by the claims of the ’413 patent, the terminal disclaimer foreclosed the patent term extension and the ’413 patent therefore expired on December 12, 2004.  Merck filed a cross-motion for judgment on the pleadings on the ground that the terminal disclaimer did not foreclose the Hatch-Waxman term extension.

The District Court sided with Merck and enjoined Hi-Tech from commercializing the drug claimed in the ’413 patent until the end of the patent term extension, i.e., until April 28, 2008.

The Hatch-Waxman Act established a patent term extension for patents relating to certain products subject to regulatory delays that could not be marketed prior to regulatory approval.  Section 156 provides an extension of up to five years if certain conditions are met as set forth in the five numbered sub-paragraphs of § 156(a):

(a) The term of a patent which claims a product, a method of using a product, or a method of manufacturing a product shall be extended in accordance with this section from the original expiration date of the patent, which shall include any patent term adjustment granted under section 154(b), if

(1) the term of the patent has not expired before an application is submitted under subsection (d)(1) for its extension;

(2) the term of the patent has never been extended under subsection (e)(1) of this section;

(3) an application for extension is submitted by the owner of record of the patent or its agent and in accordance with the requirements of paragraphs (1) through (4) of subsection (d);

(4) the product has been subject to a regulatory review period before its commercial marketing or use;

(5)(A) except as provided in subparagraph (B) or (C) [not relevant in this case], the permission for the commercial marketing or use of the product after such regulatory review period is the first permitted commercial marketing or use of the product under the provision of law under which such regulatory review period occurred.

Hi-Tech claimed that terminal disclaimers are irrevocable and final because the disclaimer is the only reason the patent issued.  Merck countered that § 156 unambiguously states that a patent term “shall be extended” where the conditions enumerated are satisfied.  Moreover, it argues that § 156 makes no mention of terminal disclaimers under 35 U.S.C. § 253 and does not prohibit them.

While § 156 states that, if the requirements are met, the patent term “shall be extended.” According to the Federal Circuit, the use of the word “shall” in a statute generally denotes the imperative.  Thus, use of the word “shall” indicates that if the enumerated list of requirements is met, the patent term is entitled to be extended. 

In addition, the court held that:

§ 156 states that the Hatch-Waxman extension shall run from the expiration date of the patent, as adjusted under section 154(b) to make up for certain PTO delays.  In turn, § 154(b)(2)(B) expressly excludes patents in which a terminal disclaimer was filed from the benefit of a term adjustment for PTO delays.  There is no similar provision that excludes patents in which a terminal disclaimer was filed from the benefits of Hatch-Waxman extensions.  The express prohibition against a term adjustment regarding PTO delays, the absence of any such prohibition regarding Hatch-Waxman extensions, and the mandate in § 156 that the patent term shall be extended if the requirements enumerated in that section are met, support the conclusion that a patent term extension under § 156 is not foreclosed by a terminal disclaimer.

Therefore, the court held that a patent term extension under § 156 may be applied to a patent subject to a terminal disclaimer. 

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