Cephalon v. Abraxis: Abraxane Does Not Infringe Cephalon's Patent Claiming Porous Paclitaxel Matrices

On June 17, 2015, the Federal Circuit affirmed a district court’s determination in Cephalon v. Abraxis that Celgene’s Abraxane drug product, which contains a fast-dissolving form of paclitaxel, did not infringe Cephalon’s U.S. Reissued Patent No. RE40,493 (“the ’493 patent”), titled “Porous Paclitaxel Matrices and Methods of Manufacture Thereof.”  Paclitaxel is a type of taxane compound derived from the bark of the Pacific yew tree that, in the words of the patent, exhibits “extremely low solubility in water,”, making effective administration challenging.  The ’493 patent addresses the solubility problem by integrating paclitaxel into a “porous matrix form which forms nanoparticles and microparticles of paclitaxel when the matrix is contacted with an aqueous medium.”

Resolution of the dispute centered around the construction of the claim term “microparticles” and “nanoparticles.” The claims recite “nanoparticles and microparticles of a taxane, wherein the nanoparticles and microparticles have a mean diameter between about 0.01 and 5 μm.”  The district court construed “nanoparticles” to mean “particles that have a mean diameter of between about 1 to 1000 nanometers and less than that of microparticles,” and construed “microparticles” to mean “particles that have a diameter of between about 1 to 1000 microns and greater than that of nanoparticles.”  The patent owner argued that the two terms (“microparticles” and “nanoparticles”) should be construed as meaning exactly the same thing, namely, “particles of a taxane having a mean diameter between about 0.01 and 5 μm.” The patent owner stipulated to non-infringement under the district court’s interpretation of the terms.

In reviewing the district court’s claim construction, the Federal Circuit applied the relatively deferential “clear error” standard, as set forth in the Supreme Court’s Teva decision, after noting that that the terms “microparticles” and “nanoparticles” are technical words, and therefore that the “scientific community’s understanding of the terms” is a question of fact reviewable for clear error.

 A claim amendment during prosecution of the patent figured prominently in the Federal Circuit’s interpretation of the terms “nanoparticles” and “microparticles.” The claims originally recited “microparticles of a taxane, wherein the microparticles have a mean diameter between about 0.01 and 5 μm,” i.e., the original claims did not recite nanoparticles. The examiner rejected the claims in view of prior art that purportedly rendered the use of micron -sized particles obvious. The applicant responded by arguing that “[t]here are no nanoparticles” in the cited prior art, and by amending the claims to recite “nanoparticles and microparticles” rather than simply “microparticles.” The amendment did not alter size range of the particles (0.01 to 5 μm).

 
The Federal Circuit found that the amendment precluded the patent owner’s proposed claim construction, noting that under this construction:

[A] pharmaceutical composition could incorporate only micron-sized particles and still fall within the scope of the claims. Such a construction is inconsistent with [the patent owner’s] amendment adding “nanoparticles and” to overcome [the prior art’s] use of only microparticles. [The patent owner] does not offer an explanation of why the word “nanoparticles” was added during prosecution, stating only “the inventors tweaked their nomenclature” which it claims “was a matter of semantics, not substance.” This assertion, however, is unsupported by the prosecution history.