The Federal Circuit has reversed a decision that Mylan Inc’s proposed generic version of a drug infringed one of two patents owned by the Medicines Company (MedCo v Mylan, Fed Cir 2017). In doing so, it revised the district court’s claim construction to import a non-limiting example from the specification to define the pivotal term – ‘efficient mixing’ – based on its determination that the example provided the “only clear delineation” of the “scope of the term”.

There are two factors at play in this decision that warrant attention. First, although the issues of validity were not ultimately reached on appeal, the court’s references to Nautilus and its cited reasons for imposing an explicitly described non-limiting definition from the specification to limit the pivotal claim term – contrary to claim construction principals – evidence a court which is mindful of the definiteness requirements of 35 USC §112 as redefined by Nautilus, Inc v Biosig Instruments, Inc (134 S Ct 2120, 2130 (2014)). Despite this, the court appears to be running foul of some of Nautilus’s major tenants – among them the post-hoc supply of objective boundaries missing from the patent itself.

Second, although not expressly cited as a critical driver of the outcome in this case, the fact that the district court made no factual findings concerning extrinsic evidence in construing the disputed claim terms enabled the Federal Circuit to conduct the de novo review which allowed the claim construction overhaul which occurred here.


This case began when Mylan filed an abbreviated new drug application (ANDA) disclosing its intention to launch a generic drug which would directly compete against Medicine’s bivalirudin drug (sold as ANGIOMAX), an anticoagulant used in heart surgery. Medicine responded by filing suit under the Hatch-Waxman Act, claiming that the Mylan’s ANDA infringed claims of two of its patents US Patent Nos 7,582,727 (the ‘727 patent) and 7,598,343 (the ‘343 patent).

The claims of both patents included a batches limitation, which requires the active ingredient to have a certain “maximum impurity level” and a target pH that is “adjusted by a base”. While both patents’ specifications referenced “efficient mixing” with regard to batches of the active ingredient, only the ‘343 patent included the efficient mixing limitation in the claim language.

The district court based its construction of efficient mixing on two examples in the common specification:

  • the inefficient mixing according to earlier Medicine's processes (Example 4); and
  • the efficient process disclosed in the specifications (Example 5), defining ‘efficient mixing’ as meaning “a PH-adjusting solution and the first solution are mixed not using inefficient mixing conditions as described in example 4”.

The district court further held that Medicine had disclaimed the old inefficient mixing process.

Mylan moved for summary judgment on the grounds that its proposed generic used an inefficient mixing process to ensure batch consistency and therefore did not infringe either patent. Although the district court granted summary judgment as to non-infringement of the ‘343 patent, it found that Mylan’s ANDA infringed the ‘727 patent because the asserted claims did not include an efficient mixing limitation.


On appeal, Mylan argued that the district court had erred by not including the efficient mixing limitation as part of the batches limitation in the ‘727 patent. Medicine attempted to exclude the efficient mixing limitation from the batches limitation by arguing that this could be defined as being satisfied whenever an accused infringer consistently produces batches with impurity levels below a certain threshold and “that the claims do not require the use of a particular process that achieves batch consistency”.

The court rejected the approach advocated by Medicine as contrary to Nautilus, reasoning that without tying the interpretation of the batches limitation to the disclosed more efficient methods, there would be no way of effectively determining when and whether infringement would occur – requiring forward-looking assessments of whether future batches would infringe. For “an ongoing commercial compounding process, this approach cannot provide ‘reasonable certainty’ regarding the scope of the asserted claims” (citing Nautilus, Inc v Biosig Instruments, Inc, 134 S Ct 2120, 2129 (2014)).

The Federal Circuit also rejected Medicine's argument that efficient mixing was expressly defined in the specification because it was linguistically different from other defined terms (ie, the term did not appear in quotes) and was “a mere recitation of the results obtained” rather than constituting a definition of what ‘efficient mixing’ is.

Ultimately, the Federal Circuit agreed with Mylan that the batches limitation must include the efficient mixing limitation and further found that the efficient mixing limitation could be derived from a non-limiting example in the specification: “We hold that [the] patents include a ‘batches’ limitation that requires batch consistency, which, according to the patents in suit, is achieved through efficient mixing… We further construe efficient mixing as defined by Example 5 of the patents’ specification.”

Although the ‘727 patent specification described Example 5 as non-limiting, the court found it appropriate to limit efficient mixing to the sole description in the patent because no other portion therein otherwise taught what affirmative steps constituted efficient mixing: “In this circumstance, we think it entirely appropriate to limit the term ‘efficiently mixing’ to the sole portion of the specification that adequately discloses ‘efficient mixing’ to the public… Example 5 provides a clear objective standard by which to measure the scope of the term.”

After taking great care to delineate – and perhaps manufacture – a clear definition of the disputed claim term by imposing a definition from the specification onto the claims, contrary to claim construction rubric, the Federal Circuit ultimately held that Mylan's ANDA did not infringe the asserted claims.

Thus, the Federal Circuit effectively maintained the validity of Medicine's patents while simultaneously clearing the way for Mylan to launch a generic drug which will directly compete against Medicine's brand drug.

Going forward

A couple of key takeaways from this case for patent practitioners are as follows: first, setting out definitions in the specification can have consequences for both the terms that are expressly defined and those that are not. Second, examples may prove vital to providing the Federal Circuit with a source for objective boundaries to otherwise nebulous claim terms – at least for now.

This article first appeared in IAM. For further information please visit