Federal Circuit decision

In its May 19 2017 panel decision in Apicore v Mylan the Federal Circuit Judges Lourie, Moore and Reyna suggested that an 'insubstantial differences' test may be more suitable than a 'function-way-result' test for evaluating infringement under the doctrine of equivalents in patent cases involving the chemical arts.

The decision arises from unusual procedural circumstances.


Apicore US LLC and Mylan Institutional LLC (collectively, 'Apicore') are the owner and licensee, respectively, of a composition patent (US Patent 9,353,050 (the ''050 patent')) and two process patents (US Patent 7,622,992 (the ''992 patent') and US Patent 8,969,616 (the ''616 patent')) concerning isosulfan blue, a dye used to map lymph nodes.

The '050 patent claims isosulfan blue having a purity greater than 99% as measured by high-performance liquid chromatography. The '992 and '616 patents claim processes for making isosulfan blue involving the use of silver oxide to oxidise isoleuco acid to isosulfan blue acid.

Aurobindo sought approval from the Food and Drug Administration to make an isosulfan blue product having a purity greater than 99% but produced by a process using manganese dioxide rather than silver oxide. Apicore sued Aurobindo in the District Court for the Eastern District of Texas for infringement of the '050, '992 and '616 patents, and sought a preliminary injunction against Aurobindo's isosulfan blue product.

In preliminary injunction proceedings, the district court found that Apicore was likely to succeed in demonstrating that Aurobindo had infringed the '992 and '616 process patents under the doctrine of equivalents, and that Aurobindo had not raised a substantial question as to the validity of the '050 patent. The district court also found that Apicore's proof of irreparable harm, the balance of equities and the public interest weighed in favour of a preliminary injunction. Accordingly, the district court granted the preliminary injunction. Aurobindo appealed.

Federal Circuit decision

On appeal, the Federal Circuit determined that the district court had erred in finding that Apicore was likely to succeed in demonstrating that Aurobindo would infringe the '992 and '616 process patents under the doctrine of equivalents.

The Federal Circuit first noted that the Supreme Court decision in Graver Tank & Mfg Co v Linde Air Prod Co (339 US 605, 608, 609 (1950)) had established two different tests for evaluating infringement under the doctrine of equivalents:

  • the 'function-way-result' test for determining whether the accused product performs substantially the same function in substantially the same way to obtain the same result; and
  • the 'insubstantial differences' test for determining whether the accused product or process is substantially different from what is patented.

The Federal Circuit then addressed the Supreme Court's subsequent encounter with the doctrine of equivalents in Warner-Jenkinson Co v Hilton Davis Chem Co (520 US 17 (1997)). According to the Federal Circuit, the Supreme Court in Warner-Jenkinson had acknowledged that the "suitability of the two tests may vary, depending on the circumstances of the case", and that "non-mechanical cases may not be well-suited to consideration under the function-way-result test. That seems to be particularly true in the chemical arts".

The Federal Circuit elaborated:

"[E]specially when evaluating an equivalents dispute dealing with chemical compositions having many components, chemical compounds with many substituents (which are usually claimed as separate limitations), and those having a medical or biological use, it is often not clear what the 'function' or 'way' is for each claim limitation. How a particular component of a composition, or substituent of a compound, functions in a human or animal body, or in what way, may not be known or even knowable (although, as technology evolves, that may change). And precedent requires that, for infringement under the doctrine of equivalents, each limitation must satisfy an equivalence test."

Turning to the case at hand, the Federal Circuit noted that the district court had opted to evaluate doctrine of equivalents infringement of the '992 and '616 process patents only under the function-way-result test. The Federal Circuit then faulted the district court for having effectively ignored the 'way' step of the function-way-result test. According to the Federal Circuit, although the district court may have correctly found that the silver oxide recited in Apicore's process patents and the manganese dioxide used in Aurobindo's accused process shared the "same function" (ie, to convert isoleuco acid to isosulfan blue acid), the district court did not adequately consider (for example) the fact that:

  • manganese dioxide and silver oxide have different oxidation strengths;
  • the use of manganese dioxide in Aurobindo's accused process requires the use of acid, whereas the use of silver oxide in the patented process does not; and
  • the two processes result in different yields.

The Federal Circuit continued:

"In this case, the district court conducted an incomplete [function-way-result] analysis while essentially bypassing the substantial differences test, in a situation where the latter test might seemingly be more appropriate. The claims in the process patents recite a method for preparing a specifically named compound by combining another specifically depicted compound with a third specific compound, viz., silver oxide. Each of these compounds is expressly named, and an infringement analysis must not take lightly the specific recitation of these materials. The district court found that the accused process using manganese dioxide was equivalent to the claimed process using silver oxide. But the court failed to consider whether the key reagent in the process, manganese dioxide, was substantially different from the claimed reagent, silver oxide, and hence whether the substitution for, and omission of, silver oxide left the accused infringer outside of the bounds of the claims...

When the case returns to the district court for a full trial on the merits, the court should, in addition to providing further analysis regarding fulfillment of the [function-way-result] test, if it determines that it should still utilize that test, also consider whether an evaluation of equivalence under the substantial differences test may be better suited to the particular facts of this case." (Emphasis in original.)

Despite its admonitions concerning the district court's doctrine of equivalents analysis, the Federal Circuit allowed the preliminary injunction to stand because the district court had not clearly erred in finding that:

  • Aurobindo's isosulfan blue product would infringe the '050 patent;
  • the '050 patent was not invalid (as Aurobindo had asserted in preliminary injunction proceedings); and
  • Apicore would suffer irreparable harm due to Aurobindo's infringement.

For further information on this topic please contact Christopher Loh at Fitzpatrick, Cella, Harper & Scinto by telephone (+1 212 218 2100) or email ([email protected]). The Fitzpatrick, Cella, Harper & Scinto website can be accessed at www.fitzpatrickcella.com.