Abraxis (AstraZeneca) v. Mayne (Fed. Cir. 2006).
Mayne attempted to around Abrxis’s anesthetic formulation patent covering DIPRIVAN. The district court, however, found that Mayne’s product still infringed, both directly and under the doctrine of equivalents, despite its replacement of EDTA (“edetate”) with DTPA.
On appeal, the CAFC reversed the direct infringement based on claim construction, but agreed that there was infringement under the DOE.
Infringement under the doctrine of equivalents is reviewed for clear error. To infringe under the DOE, the accused device must perform “substantially the same function in substantially the same way to obtain the same result” as the patented invention.
During the design-around, the defendant had attempted to identically match the characteristics and stability function of the Abraxis product. They eventually chose the DTPA replacement because it is “structurally similar to edetate, [and therefore] product stability is predicted to be unaffected."
Even so, the defendant argued under the modern DOE exclusion principle that the patentee’s use of the “restrictive term edetate,” rather than a more generic term, precluded extension of equivalents coverage as a matter of law. The CAFC disagreed, finding that equivalents could be asserted because the inventors “did not clearly disavow” broader coverage.
There is no evidence that the patentees made a clear and unmistakable surrender of other polyaminocarboxylates, or calcium trisodium DTPA in particular, during prosecution.
Furthermore, because the use of DTPA was admittedly unforeseeable, it is proper to extend DOE.
The defendant also asserted that DOE should not be extended to cover DTPA because Mayne was able to obtain a patent to cover that modification. The CAFC did not buy that argument either. As noted above, the patent shows that the equivalent was unforeseeable at the time of the invention (weighing in favor of DOE). In addition, the district court’s fact finding of “substantial evidence of equivalence” withstood CAFC scrutiny.