Addressing the issue of the proper construction of claims to a trihydrate compound, the US District Court for the District of New Jersey concluded that a person of ordinary skill in the art (POSA) would understand "hydrate" to require a crystalline form. AstraZeneca AB v. Andrx Labs, LLC, Case Nos. 14-8030, 15-1057 (D.N.J. Jan. 11, 2017) (Cooper, J.).

Defendants Andrx and Perrigo both sought to market generic versions of Plaintiff's Nexium® product. Plaintiff asserted patents covering the magnesium salt of S-omeprazole trihydrate. The parties disputed whether the term "trihydrate" requires a crystalline form—Defendants argued in the affirmative and Plaintiff disagreed. All parties pointed to intrinsic and extrinsic evidence to support their positions, including expert testimony. The court began by summarizing the written description and prosecution histories of the asserted patents, but concluded that "[a]fter reviewing the specification and prosecution histories in detail, the question of whether the term 'trihydrate' was understood by the POSA to connote a crystalline form is left unanswered." The court next turned to the extrinsic evidence and found "the testimony and exhibits of Andrx's expert, Dr. Zaworotko most persuasive."

The court placed particular emphasis on the fact that Dr. Zawartko cited numerous texts from the pertinent time period indicating that "trihydrate" refers to a crystalline form. The court also noted that two of the references on which Dr. Zawartko relied were authored by AstraZeneca's expert, Dr. Byrn, whose pre-priority date writings "made clear distinctions between hydrates and amorphous forms on the basis of crystallinity." Based on the references provided by Dr. Zawartko, the court was "persuaded that the POSA would have understood the term 'trihydrate' to mean a crystalline form."

In contrast, the court rejected the competing references proffered by Plaintiff's expert, Dr. Byrn, as "not persuasive" and emphasized that Dr. Byrn's own publications contradicted his opinions. In addition to the Byrn articles relied on by Dr. Zawartko, the court pointed out that Dr. Byrn's "prior writings directly contradict [his] position" that "solid state materials exist on a continuum of amorphous and crystalline material"; further, Dr. Bryn's "prior writings also directly contradict his characterization of a hydrate."

Plaintiff also argued that the principle of claim differentiation required a broad reading of the trihydrate term. The asserted claims defined the claimed compound in different ways: the broadest claim covered "[t]he magnesium salt of S-omeprazole trihydrate" with no other limitations, while other claims further required that trihydrate be "characterized by" a list of 13 "major peaks in its X-ray diffractogram" or "represented by" the X-ray power diffraction (XRPD) diffractogram provided in "FIG 1." According to Plaintiff, because the claim directed to the trihydrate compound must be broader in scope than the claims directed to a trihydrate with a particular XRPD profile, the term "trihydrate" must encompass non-crystalline forms.

The court agreed that the claims differ in scope, but cautioned that "the doctrine of claim differentiation cannot broaden the term 'the magnesium salt of S-omeprazole trihydrate' beyond its correct scope." The court then adopted the rationale of Andrx's expert and concluded that the claim to the trihydrate compound "may cover all crystalline polymorphs of S-omeprazole magnesium trihydrate." Thus, the claims requiring a particular XRPD profile are narrower because they "are both limited to a particular crystalline polymorph of that trihydrate."

Practice Note:

Before proffering expert testimony in support of a claim construction position, counsel should review the expert's publications on the subject at issue in order to avoid a potential credibility hit from repeated inconsistencies.

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