Practical Strategies For Protecting Innovations Under The Doctrine Of Equivalents

• Published date: 22 June 2023
• Subject Matter: Intellectual Property, Food, Drugs, Healthcare, Life Sciences, Patent, Food and Drugs Law, Biotechnology & Nanotechnology
• Law Firm: Morrison & Foerster LLP
• Author: Ms Kelsey J Roberts Kingman and Bu Yin

Recent case law highlights enablement and written description challenges for genus claims.¹ Given the challenges of enforcing genus claims, the doctrine of equivalents (DOE) may become a more important tool for patentees when literal infringement is unavailable.

As discussed below, the outlook for successful application of DOE to biologics remains uncertain. But with careful prosecution strategies, patentees can better preserve their DOE arguments to block design-arounds with insubstantial differences and/or those that perform substantially the same function in substantially the same way.

DOE for Biologics

Ajinomoto Co., Inc. v. ITCprovides a rare example of successful DOE application to protein sequences.² There'applying the "function-way-result" (FWR) test for analyzing equivalence'the Federal Circuit concluded that a bacterialstrain engineered to express a particular amino acid sequence was equivalent to a strain engineered to express a different amino sequence of a related protein.³ In finding that the proteins functioned in substantially the same way, the court relied on the facts that the two proteins were 95% identical in primary amino acid sequence and were predicted to be 85% identical in structure.⁴ Thus, when applying the FWR test to large biomolecules, sequence similarity will likely be an important consideration as it was in the Ajinomoto decision.

A more recent case, Teva Pharmaceuticals International GmbH v. Eli Lilly & Co., illustrates that relying on DOE to broaden the scope of claims reciting biological sequences (e.g., antibody sequences) can be challenging.⁵ There, Teva asserted two claims reciting antibody CDR sequences and variable region sequences against Lilly under DOE. The antibodies at issue shared only 29.9% sequence similarity in the CDRs, and the heavy chain of the closest variant disclosed in Teva's patent shared only 52.5% similarity with Lilly's antibody.⁶ In this case, the court said that application of DOE would be "a bridge too far" and would effectively read the amino acid sequence limitation out of the claims.⁷ Thus, DOE arguments that essentially vitiate the sequence limitations would not be likely to succeed.

It is worth noting that the court in Teva decided on the DOE issue using the "insubstantial differences" test, which the court viewed as more appropriate for evaluating equivalents in chemical compounds. Although it is clear from Teva that application of DOE to biologics likely requires "insubstantial...