Claim Construction and Expert Testimony in Pharmaceutical Patent Litigation

Tang O. Tang | January 31, 2013

Allergan, Inc. v. Barr Laboratories, Inc., Teva Pharmaceutical USA, Inc., and Teva Pharmaceutical Industries Ltd. and Sandoz Inc.

January 28, 2013

Panel: Rader, Bryson and Wallach.  Opinion by Bryson.


Barr Lab. and Sandoz Inc. etc. (collectively Defendants) filed a Abbreviated New Drug Application (ANDA), listing the patented product in Allergan’s ‘819 patent. Allergan filed an infringement suit against the Defendants. The district court ruled for Allergan, and the Defendants brought it to appeal.

One major point of dispute was about one moiety in the claimed compounds described in claim 5 of patent ‘819 as representable by –N(R4)2. The Defendants asserted that the two R4 moieties must be construed as identical. The district court and the CAFC both found for Allergan in holding that the R4 units did not need to be identical.

Another point of dispute was about the requirement for courts’ independent inquiry into “obviousness” type of patent invalidity case. The CAFC affirmed the district court’s decision that the expert testimony may be a required part of patent invalidity cases based on obviousness, and that independent review of a case involving complex technology, in absence of expert witness, is not required.

Barr Labs和Sandoz公司(以下统称被告)向联邦食品药品管理局提出简化新药申请(ANDA)中将Allergan公司的819专利所保护的专利药品列为仿制药。 Allergan公司对被告提起侵权诉讼。联邦地区法院裁定Allergan胜诉,被告遂到联邦巡回法庭提出上诉。

争议要点之一是,在专利819的权利要求5,对要求受保护药物的描述包括该化合物含有基团 “–N(R 42”。被告声称,这两个R4基团应该理解为相同基团。区法院和联邦巡回上诉法院都认同Allergan的理解,认定对R4基团定义应基于该专利文件中的具体描述,所以两个R4基团不一定相同。



Allergan obtained the US patent 5,688,819 (patent’819) in 1997, claiming a family of intraocular pressure (IOP) hypotensive compounds called PGF for the treatment of glaucoma and ocular hypertension. A major difference in patent’819 from the prior art is that in the claimed compounds, a carboxylic acid group is substituted with a non-acidic group to prevent certain side effects. A particularly commercialized PGF is Bimatoprost, with a structure of





Barr Lab. and Sandoz Inc. etc. (collectively Defendants) filed Abbreviated New Drug Applications (ANDA) respectively, listing the patented PGF product in Allergan’s patent’819 and stating that patent’819 was invalid.  Allergan filed infringement suit against the Defendants. District court ruled for Allergan, and Defendants brought it to appeal.

Claim Construction

Claim 5 of the subject patent’819 describes one moiety of the hypotensive compounds as “–N(R4)2 wherein R4 is selected from the group consisting o[f] hydrogen, a lower alkyl radical having from one to six carbon atoms…” Defendants contended that Bimatoprost is not protected under patent’819, because based on plain and ordinary language, the –N(R4)2 group should be construed as two identical R4 units connected to the N atom, while in Bimatoprost, one hydrogen atom and one ethyl group are connected to the N atom.

The district court and the CAFC both, citing Phillips v. AWH Corp., 415 F.3d 1303, 1312-13 (Fed. Cir. 2005), acknowledged that “[c]laim terms are generally given their ‘ordinary and customary meaning’…” But the courts emphasized that the person of ordinary skill is deemed to read the claim terms “in the context of the entire patent, including the specification” (see id). The courts stated that “the inventor’s lexicography governs when “the specification [] reveal[s] a special definition given to a claim term” other than the plain and ordinary meaning.

Requirement on Courts to Independently Review Obviousness of Patent

During the litigation at the district court, the Defendants called an expert witness to testify as to the obviousness of patent ’819 in light of the prior art. The district court found that the credibility of the expert witness was “flawed on a fundamental level” and declined to assign any weight to his opinions. The district court subsequently decline to independently review the prior art references.  That is, the court deemed an expert witness testimony as a necessary piece of evidence of showing invalidity based on obviousness. No further review of the evidence is needed if the expert testimony is missing from the record. Hence, the Defendants did not meet their burden of proof. The Defendants appealed, challenging that discrediting the expert witness “did not then permit the [district] court to ignore all other evidence…”.

The CAFC basically held that the court may use its discretion in determining whether expert witness testimony is required in cases involving complex technology. The CAFC pointed out that “[o]bviousness is one area in which expert testimony may be required.” The standard set forth in precedent cases is whether the technology is “sufficiently complex to fall beyond the grasp of an ordinary layperson” (see Proveris Scientific Corp. v. Innovasystems, Inc., 536 F.3d 1256, 1267 (Fed. Cir. 2008)).

The CAFC reasoned that the current case was not a case where “the technology is simple” or the references are “easily understandable without the need for expert explanatory testimony” (see Sundance, Inc. v. DeMonte Fabricating Ltd., 550 F.3d 1356, 1365 (Fed. Cir. 2008) and Union Car-bide v. American Can Co., 724 F.2d 1567, 1573 (Fed. Cir. 1984)).  And the district court did not err in find that common sense and logic were not sufficiently illuminating in the current case. The CAFC affirmed the district court’s decision with regard to this matter.

The Defendants also tried to rely on the opposing party’s expert testimony in establishing obviousness, but this approach was not successful.

Note:  ANDA is an application for a U.S. generic drug approval for an existing licensed medication or approved drug. The ANDA is submitted to FDA’s Center for Drug Evaluation and Research, Office of Generic Drugs, which provides for the review and ultimate approval of a generic drug product.  However, filing an ANDA with a Paragraph IV certificate, which contain detailed statement of the factual and legal basis of the applicant’s opinion that the patent is not valid or will not be infringed, is very likely to lead to a legal war. The patent holder has 45 days from the receipt of such a notice to file a suit for patent infringement (see FD&C Act §505(j)(5)(B)(iii)).


1. It is noteworthy that Allergan could have avoided such litigation by drafting patent’819 more clearly.  The courts may go to the extent to infer from the context of the specification and the claims, that the two R4 groups may be different from each other.  However, Applicants should not expect the PTO patent examiner to read all the customized definition of terms in their daily patent prosecution process.  Applicants are encouraged to submit claims with “specially defined” terms recited in the claims.

2. Markush group is commonly used claiming method.  However, attention to the language details of the Markush group may give the patent broader scope and less ambiguity.  For example, in the instant case, Allergen could have recited that “R4 is each independently selected from a group consisting of…” or “R4 and R4, each independently selected from a group consisting of…” to avoid ambiguity.

3. Expert testimony can be the critical piece of evidence presented at the court.  It is equally important to choose a qualified and creditable expert witness as to find the competent counsel.

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