Claims to a method of hepatocyte cryopreservation are patent-eligible, according to a recent decision by the U.S. Court of Appeals for the Federal Circuit.

In Rapid Litig. v. CellzDirect, Inc.1, the Federal Circuit over-turned the district court’s determination that U.S. Patent No. 7, 604, 929 (“‘929 patent”) patent was directed to a patent-ineligible law of nature, namely that hepatocytes are capable of surviving multiple freeze-thaw cycles. The Federal Circuit found that while the claims recited a natural law, they were directed to a new and useful method of preserving hepatocyte cells.

The ‘929 patent was based on the inventors’ discovery that some hepatocytes are capable of surviving multiple freeze-thaw cycles. Previously, it was understood that hepatocytes could only be thawed once before they would have to be used or discarded. In view of this discovery, the inventors developed an improved process of preserving hepatocytes. Accordingly, the ‘929 patent claims a method comprising (A) subjecting previously frozen and thawed cells to density gradient fractionation to separate viable cells from non-viable ones; (B) recovering the viable cells and (C) refreezing the viable cells.

The Federal Circuit applied the two-part test set out by the Supreme Court in Mayo v. Prometheus2 for determining patent-eligible subject matter under 35 U.S.C. 101. The Federal Circuit found that the claimed methods could be found eligible at step one of the test, because they are not simply directed to patent ineligible subject matter, namely the ability of hepatocytes to survive multiple freeze-thaw cycles. Rather, the claims are directed to a new and useful laboratory technique that produces a “tangible and useful result”.

The Federal Circuit distinguished the present claims from those found ineligible in other recent decisions. For example, in Ariosa v. Sequenom3 (discussed here and here), the patent at issue claimed methods for detecting paternally inherited cffDNA in the blood or serum of a pregnant female. According to the Federal Circuit, the existence of cffDNA is a natural phenomenon and in contrast to the ‘929 patent, identifying its presence was merely claiming the natural phenomena itself.

The Federal Circuit further held that even if the ‘929 patent claims were not found eligible at step one of the Mayo test, they would be found eligible at step two, as they recite an improved process for preserving hepatocytes for future use. In addition, while each of the claims’ individual steps (freezing, thawing, and separating) were known independently in the art, this does not make the claim unpatentable as it is the particular combination of steps that is patentable here.

This affirmation of patent-eligible subject matter is welcomed, as the scope of patentable subject matter in the Life Sciences continues to be a contentious issue in the U.S. The decision confirms that applications of natural discoveries are patentable and that even if a claim recites a natural law, additional claim elements can provide a new and useful product or method.