Indefiniteness kills patent, as expert testimony cannot compensate for the failure of intrinsic evidence to provide a “reasonably certain” meaning to claim term.

Cindy Chen | July 15, 2015

Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc.

June 18, 2015

Before: Moore, Mayer, Wallach. Opinion by Moore. Dissent by Mayer.


The validity of Teva Pharmceuticals’ patent hinged on the definiteness of the term “molecular weight”. Under a the old “insolubly ambiguous” standard, the Federal Circuit had determined once before that the term was indefinite. The Supreme Court vacated this indefiniteness determination in Teva Pharm. USA, Inc. v. Sandoz, Inc., 135 S. Ct. 831 (2015) (Briefed by John Wang  ). The Federal Circuit was found to have erred by not giving proper deference to the lower court’s factual findings in construing the term “molecular weight”. Teva Pharmaceuticals’ short-lived victory lasted until the Federal Circuit once again reached the same conclusion that the term “molecular weight” was indefinite, this time under the new “reasonably certain” standard of Nautilus, Inc. v. Biosig Instruments, Inc., 134 S. Ct. 2120 (2014).


Teva Pharmaceuticals USA (“Teva”) owns U.S. Patent No. 5,800,808 (the “‘808 patent”), which relates to a method of making copolymer-1 having a particular molecular weight fraction by:

reacting protected copolymer-1 with hydrobromic acid to form trifluoroacetyl copolymer-1, treating said trifluoroacetyl copolymer-1 with aqueous piperidine solution to form copolymer-1, and purifying said copolymer-1, to result in copolymer-1 having a molecular weight of about 5 to 9 kilodaltons.

The trouble with Teva’s claim 1 is that the “molecular weight” can mean one of three things: peak average molecular weight (Mp), number average molecular weight (Mn), and weight average molecular weight (Mw).

Individual polymer molecules in a sample of copolymer-1 have varying weights. Each measure of the sample’s “molecular weight” of can therefore be calculated differently based on a different parameter of the sample. Mp measures the molecular weight of the most abundant molecule in the sample. Mn measures the arithmetic mean, or the total mass of all the molecules in the sample divided by the total number of molecules. Mw is determined by a still more complicated formula based on weight fractions of each type of molecules.

When Teva sued Sandoz, Inc. (“Sandoz”) for infringing the ‘808 patent, Sandoz attacked the patent’s validity by arguing that the term “molecular weight” was “insolubly ambiguous” and “not amenable to construction”, which were the standard for indefiniteness at the time.

The district court disagreed, and construed the term based on the following evidence:

  •  Intrinsic evidence
  • Claim: The claims are unhelpful, as they do not define “molecular weight”.
  • Specification: Example 1 describes measuring “molecular weight” of copolymer-1 using size exclusion chromatography. Figure 1 of the specification shows a molecular weight distribution curve generated using size exclusion chromatography.

  • Prosecution history: The meaning of “molecular weight” was not discussed during the prosecution of the ‘808 patent, even though to overcome the art rejections, Teva relied on the advantage of its method to produce precise fractions of copolymers-1 within the “molecular weight” range of 5 to 9 kilodaltons. During prosecution of two continuations of the ‘808 patent, the Examiners rejected the term “molecular weight” as indefinite. Teva overcame the indefiniteness rejection in one case by defining “molecular weight” as “weight average molecular weight (Mw)”, and in another, “peak average molecular weight (Mp)”.
  • Extrinsic evidence: Teva offered expert testimony to explain that the “peaks” in the distribution curve in Figure 1 corresponds directly to “peak average molecular weight (Mp)”, without requiring further calculation. To derive any other measures of “molecular weight” from Figure 1 would require further calculations. The fact that the peaks in Figure 1 do not align exactly with 7.7 kDa or 12.0 kDa as shown in the figure legend was the merely the result of curve-shifting from noises during data processing.

The district court gave tremendous credit to the opinions of Teva’s expert on Figure 1, and ultimately construed “molecular weight” to mean “peak molecular weight detected using an appropriately calibrated suitable gel filtration column”.

In Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc. (Fed. Cir. 2013) (“Teva I”), the Federal Circuit reviewed the district court’s claim construction de novo, and reversed the district court’s determination. The Federal Circuit concluded that the term “molecular weight” was “not amenable to construction or insolubly ambiguous”. Given the (i) inconsistency in the related prosecution histories and (ii) the fact that all three of peak average, number average, and weight average “molecular weights” can be read from Figure 1, the Federal Circuit was not convinced that Teva’s expert testimony saved the term “molecular weight” from indefiniteness.

In Teva’s subsequent appeal to the Supreme Court, Teva argued that the Federal Circuit should have given more deference to the district court’s factual findings about Teva’s expert testimony. The Supreme Court agreed:

“If a district court needs to consult extrinsic evidence, for example, to understand the meaning of a term in the relevant art at the relevant time, the court may need to make subsidiary factual findings about that extrinsic evidence.” “The reviewing court, however, should review subsidiary factual findings under the clearly erroneous standard.”

The Supreme Court vacated and remanded Teva I for review of the district court’s factual findings about Teva’s expert testimony under the clearly erroneous standard.

The Federal Circuit obliged, which leads us to the Teva II decision before us.

Repeating the phrase “no clear error” in four quick successions in one paragraph, the Federal Circuit found no clear error in the district court’s factual findings with respect to the opinions of Teva’s expert on what Figure 1 in the ‘808 patent represents.

But the hand that giveth, also taketh away. The Federal Circuit pointed out that while that decision was pending, the Supreme Court wrote its opinion in Nautilus, Inc. v. Biosig Instruments, Inc.:

A patent is indefinite “if its claims, read in light of the specification delineating the patent, and the prosecution history, fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.”

The Federal Circuit immediately reinstated its previous position that the opinions of Teva’s expert cannot save the indefiniteness of the term “molecular weight”:

A party cannot transform into a factual matter the internal coherence and context assessment of the patent simply by having an expert offer an opinion on it. The internal coherence and context assessment of the patent, and whether it conveys claim meaning with reasonable certainty, are questions of law . . . Teva cannot transform legal analysis about the meaning or significance of the intrinsic evidence into a factual question simply by having an expert testify on it.

The Federal Circuit examined the intrinsic evidence, and found that the (i) lack of a clear definition in the claims, (ii) ambiguity of Figure 1 in the specification, and in particular, (iii) contradictory definitions in the related prosecution histories, failed to resolve the question of how “molecular weight” should be measured. The Federal Circuit thus concluded that the meaning of the term “molecular weight” is not “reasonably certain”, and the ‘808 patent claims were invalid as indefinite.

When the Supreme Court’s decision in Teva issued, it was believed that the decision, by requiring certain deference to the district courts’ claim construction determinations (and indirectly indefiniteness determinations), would insulate those determinations against the Federal Circuit’s typically high reversal rate, and instill predictability into the proceedings. The Federal Circuit’s Teva II decision here seems to belie that belief. Couched in the legal analysis of indefiniteness, the Federal Circuit retains substantial leeway in deciding how lower courts’ factual determinations should be treated. Teva II thus suggests that deference may be partial and certainly not guaranteed. A similar theme can be found in the Federal Circuit’s recent decision in Shire Development et al. v. Watson Pharmaceutical et al. (Briefed Ryan Chirnomas)


  • The decision in Teva II shows that involving an expert will not necessarily cure the indefiniteness of a claim term. The Federal Circuit will continue to give more weight to intrinsic evidence, which is also the lesson in Enzo Biochem Inc. v. Applera Corp. (briefed by Nicolas Seckel).
  • The focus should still be on developing the “internal coherence” of the intrinsic evidence at the prosecution level. For example, crucial terms should be defined; beware of inconsistent positions regarding the same claim term in related applications; beware of what is said in response to indefiniteness rejections.

full opinion

U.S. 5,800,808

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