1. Whether the scope of a claim, limited during patent prosecution because of a patentability rejection for obviousness and a restriction requirement, can be recovered by the doctrine of equivalents.
2. Whether the fact that a patent applicant was required by the examiner to select a specific polymer from a group listed on its application establishes that the resulting amendments were not made to overcome a patentability rejection for obviousness.
1. No. If claim scope is relinquished during prosecution on grounds of patentability, the doctrine of prosecution history estoppel provides that the relinquished scope cannot be recovered by operation of the doctrine of equivalents.
2. No. The determination of whether an amendment was made for purposes of patentability on grounds of obviousness is determined from the viewpoint of a person skilled in the art, and can be based on whether the applicant pursues patents for the broader claims limited by the amendment.
Merck is the assignee of U.S. Patents Nos. 4,832,957 ('957 patent) and 4,900,755 ('755 patent), that are directed to a controlled release formulation of a combination of drugs used to treat Parkinson's disease. The controlled release is achieved by delivering the drugs in a polymer vehicle. The composition of this polymer is at issue in this dispute.
Merck's initial application was directed to a polymer vehicle that was comprised of a water soluble and less water soluble polymer. The patent examiner rejected the claims in light of the prior art, based on obviousness. The examiner also required Merck to make an election of specific species of polymers. Merck then filed a continuation-in-part application claiming a polymer vehicle which would be selected from a list of water soluble and less water soluble polymers stated in the application, including HPC, HPMC, and PVACA. This was also rejected. Merck then filed a second continuation-in-part application limiting the broadest claim to the combination of polymers HPC and PVACA. This application issued a patent.
Mylan filed an Abbreviated New Drug Application with the FDA for a similar product using a combination of polymers HPC and HPMC. Merck brought suit charging Mylan with infringement under the doctrine of equivalents, claiming the polymer vehicle used in Mylan's product is equivalent to Merck's because HPMC and PVACA are interchangeable in this use. The United States District Court for the Eastern District of Pennsylvania granted summary judgement that Mylan did not infringe Merck's patents, holding that both prosecution history estoppel and the prior art precluded a finding of equivalency. The district court found that Merck limited its claims to the particular polymer species in response to the examiner's obviousness rejection, despite the fact that the examiner had also imposed a restriction requirement. Merck appealed and argued that it simply complied with the examiners formal requirement of an examination expedient, and that once it had elected a species, the examiner's rejection based on the prior art simply became irrelevant to the prosecution.
The Federal Circuit affirmed the judgement of the District Court. The Federal Circuit stated that if claim scope is relinquished during prosecution on grounds of patentability, the doctrine of prosecution history estoppel provides that relinquished scope can not be recovered by operation of the doctrine of equivalents. The court also stated that the most reasonable reading of the prosecution history estoppel is that Merck limited its claims primarily in consideration of patentability rejection for obviousness and not because of the restriction requirement.
Prepared by the liibulletin-patent Editorial Board.