Federal Circuit Uses Claim Construction to Determine Proper Inventorship

University of Pittsburgh v. Hedrick (Fed. Cir. Jul. 23, 2009)

In this case, the district court (Central District of California) found that four individuals were not co-inventors of the patent at issue. The Federal Circuit, in an opinion by Judge Mayer, affirmed. This case is interesting as the inventorship issue turned on the construction of the claim term "adipose-derived."

The patent claims related to adipose-derived stem cells. Initially, the patent application listed seven inventors (two from the University of Pittsburgh and five from UCLA ("the REBAR researchers")). After the patent was granted, the University of Pittsburgh filed an action seeking the removal of all five REBAR researchers as co-inventors. One of the REBAR researchers voluntarily dismissed himself from the suit, leaving the dispute between the remaining four REBAR researchers and the University of Pittsburgh.

At issue in this case was the definition of the term "adipose-derived" and specifically whether "adipose-derived" simply meant "derived from fat tissue" or more specifically meant "species of stem cell distinct from the mesenchymal stem cell that is obtainable from bone marrow tissue." The district court determined that the term should have the plain meaning of "derived from fat tissue." Claim construction was important in this dispute because the REBAR researchers "alleged that their research proved that the inventive stem cells were in fact distinct from the prior art mesenchymal stem cells." While the REBAR researchers agreed that "derived from fat tissue" was the plain meaning of the term "adipose-derived," they argued that the proper construction must also include that the stem cell is "a species of stem cell distinct from the mesenchymal stem cell ('MSC') that is obtainable from bone marrow tissue." While the REBAR researchers pointed to both the specification and prosecution history to support their argument, the district court determined that the specification supported the plain meaning of the term and there was no disavowal of any other meaning during prosecution and concluded that the invention had been conceived prior to the REBAR researchers' work on it.

In its analysis, the Federal Circuit considered the patent specification first. The Court found the specification indicated that while "the mesenchymal stem cells require costly prescreening of culture materials, the inventive stem cells can be passaged in culture in an undifferentiated state not requiring prescreened lots of serum." Further, the specification did not state that the cells were a separate species from mesenchymal stem cells collected form bone marrow. However, the Court found "[t]hat other similar prior art cells are described differently than the inventive cells does not rise to an intent to deviate from the meaning of the terms describing the inventive cells."

Next the Federal Circuit focused on the prosecution history. During prosecution, the applicants overcame a rejection of claims by introducing the term "adipose-derived." They then submitted a paper showing that mesenchymal stem cells and the inventive stem cells differed in their intrinsic properties. This submission was made after an examiner interview where the patentees "agreed that a submission to distinguish between adipose derived stem cell and bone marrow stem cell will be submitted." The Examiner then agreed with the inventors that the "adipose-derived stem cells are distinct from the mesenchymal stem cells" of the prior art, but also noted that the claims were in condition for allowance without requiring an amendment.

The Federal Circuit found there was no disavowal, stating that "[a] wide chasm exists between the weak inference from the summary that adipose-derived stem cells in this invention must be a different species from mesenchymal stem cells and a clear and unmistakable disavowal as required to limit a claim term." Subsequently, the Federal Circuit agreed with the district court's claim construction and found that the REBAR researchers should not have been listed as co-inventors on the patent.

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