United States: Statements Made When Prosecuting Narrower Parent Application Do Not Necessarily Limit A Child Patent

Holding

In Supernus Pharm., Inc. v. Lupin Ltd., C.A. No. 21-1293 (D. Del. April 5, 2023), the United States District Court for the District of Delaware construed two claim terms disputed by the parties. The court did not apply the prosecution history of the parent application to narrow the claims at issue and also held that certain parts of the decided constructions were appropriate in this case based on the description in the specification.

Background

U.S. Patent Nos. 8,992,989 ("the '989 Patent"), 9,549,940 ("the '940 Patent"), 9,622,983 ("the '983 Patent"), and 10,314,790 ("the '790 Patent") relate to pharmaceutical compositions for topiramate. Independent claim 1 of the '989 Patent is representative of the first three of these patents and recites:

'989 patent at claim 1 (emphasis added).

Independent claim 1 of the '790 Patent recites:

'790 patent at claim 1 (emphasis added).

Regarding the phrase "an extended release (XR) topiramate-containing component" in the '989, '940, and '983 Patents, Supernus argued that no construction was necessary, but alternatively proposed a construction of "a component that releases topiramate over a prolonged period of time."

Lupin argued that the phrase should be construed narrowly based on statements made by Supernus during prosecution of the parent application of the patent at issue. Specifically, Lupin argued that the claim language included two additional limitations: (1) the XR component must be comprised of beads and (2) the XR component must have at least two populations of these beads. In connection with its arguments, Lupin pointed to statements made by Supernus during prosecution of a parent application. Lupin also argued that there was no "floor" to Supernus's phrase of "prolonged period of time" in its proposed alternative construction.

Regarding the term "at least two extended release (XR) topiramate-containing components" in the '790 Patent, Supernus again maintained that no construction was necessary, but alternatively proposed a construction of "at least two extended release topiramate-containing components having in vitro release rates for topiramate." Lupin, on the other hand, proposed a construction of "at least two different extended release (XR) topiramate-containing bead populations."

Court Decision

The Court rejected Lupin's first argument that the XR component must be comprised of beads. It pointed out that the claim language itself does not require this, and that the specification describes embodiments with and without beads. The Court also rejected Lupin's arguments that Supernus had limited its claims to bead embodiments through prosecution history estoppel. Instead, it found that the statements in question were only made to distinguish between claims that already recited beads.

After rejecting Lupin's first argument, the Court turned to Lupin's second argument that the XR component must have at least two populations of beads. The Court emphasized that the standard for finding prosecution history estoppel is high, as it requires a clear and unambiguous statement, and again, disagreed with Lupin that statements during prosecution of the parent application should apply to narrow the construction of the claims at issue. Looking closely at the prosecution history, the Court found that Supernus made the statements in question with respect to claims that already included a two-XR component limitation. It also explained that Lupin did not show why the broader claims with a single XR component required this limitation, especially where the prosecution history showed that the Examiner understood the difference in claim scope between the different applications. The Court concluded by saying that Supernus did not make any unmistakable disavowals of claim scope during prosecution to require a limitation of two XR components for claims that did not recite that aspect.

The Court did, however, add an element to the construction Supernus proposed for "an extended release (XR) topiramate-containing component." Relying on testimony from Supernus's expert, the Court held that the "prolonged period of time" should be construed to mean "a continuous period of time of greater than about 1 hour," based on particular statements in the specification.

Regarding "at least two extended release (XR) topiramate-containing components," the Court adopted a construction of "[at least] two components that release topiramate over a prolonged period of time, each component having a different release rate." This differed from Lupin's proposed construction, because it did not require bead populations, and also differed from Supernus's proposal, because it included "each component having a different release rate." In connection with this construction, the Court pointed to Supernus's specification, which "describes XR components comprising a population of beads and states that there is a specific release controlling coating for each population," as well as a table in the specification. The Court interpreted the specification's discussion of the specific coatings as showing different coatings for each population.

Take-aways

Supernus obtained a mostly favorable decision because prosecution history estoppel was not applied to reach some of the more restrictive claim constructions proposed by Lupin. Nevertheless, the Court adopted constructions different from what Supernus proposed, mostly based on the description included in the specification.

While many defendants seek to apply prosecution history estoppel, the bar remains high. Especially here, where the allegation of prosecution history estoppel involved different claim terms from a parent application that did not correspond to an asserted patent, a "clear and unmistakable" disavowal¹ was not shown and is difficult to show. Nevertheless, patentees should exercise caution with statements made during prosecution, especially when they involve claim terms likely to be used in, or otherwise relevant to, the claims of future continuation applications. Think along the lines of the Miranda rights when writing specifications: anything you say can and may be used against you by your adversary.

In addition, although it is a principle of claim construction that limitations generally should not be imported from the specification into the claims, it is also a principle that the claims generally should be read in view of the written description.² Careful consideration therefore must go into drafting the specification. One of the objectives is to draft a specification that supports the desired claim scope and makes it more likely that the claims are construed as intended and withstand challenges.

Footnotes

1. See Elbex Video, Ltd. v. Sensormatic Electronics Corp., 508 F.3d 1366, 1371 (Fed. Cir., Nov. 28, 2007).

2. Phillips v. AWH Corp., 415 F.3d 1303, 1315 (Fed. Cir. 2005) (en banc)

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