On Dec. 21, 2020, Federal Circuit affirmed district court’s summary judgment that found infringement under Doctrine of Equivalents (DoE).

Eli Lilly owns US 7,772,209 patent which relates to “a method of administering an antifolate to a mammal in need thereof, comprising administering an effective amount of said antifolate in combination with a methylmalonic acid lowering agent”. Independent claims covers administration of pemetrexed disodium (antifolate) with folic acid & methylmalonic acid lowering agent (vitamin B12). This patent is listed in Orange Book for the product ALIMTA®.  Eli Lilly markets ALIMTA in USA for the treatment of mesothelioma and certain types of lung cancer.  Apotex filed NDA with USFDA to market different salt i.e. pemetrexed dipotassium.  Eli Lilly then sued Apotex for infringement. United States District Court for the Southern District of Indiana issued summary judgment of infringement in favor of Lilly. It found that Lilly is not estopped from arguing DoE because there was no Prosecution History Estoppel (PHE).

Apotex argued that the term “ALIMTA” in the original claims would have been understood to mean “pemetrexed,” therefore, Lilly’s amendment to replace “ALIMTA” with “pemetrexed disodium” was a narrowing amendment and Lilly surrendered all other salt forms of pemetrexed. Federal Circuit, however, sided with district court & said that this amendment was not narrowing one. The intrinsic record equates ALIMTA with pemetrexed disodium. The specification refers to “pemetrexed disodium” twice, both times in association with ALIMTA. Moreover, the prosecution history confirms that the inventors used “ALIMTA” in the original claims—and the Examiner understood the term—as Lilly’s trade name for pemetrexed disodium. Examiner rejected claims related to ALIMTA trademark under 35 U.S.C. 112, second paragraph because it is improper to use trademark in the claims according to MPEP. In response to the rejection, Lilly canceled its claims reciting the trade name and pursued claims using the generic name (pemetrexed disodium), which mooted the rejection. Therefore, nothing in the prosecution history suggests that Lilly’s amendment narrowed the claims or or that either Lilly or the Examiner understood “ALIMTA” to mean anything other than pemetrexed disodium.

Thus, the district court properly concluded that prosecution history estoppel does not bar Lilly’s infringement claims under the doctrine of equivalents.