When trying to overcome an obviousness rejection of a patent claim, an argument that two or more cited references cannot be combined may be used.  For example, it can be argued that the combination is improper because the modification of a reference completely changes its “fundamental principle of operation.”  However, it can be difficult to overcome obviousness rejections using this argument, which is highlighted in a recent Federal Circuit decision in University of Maryland v. Presens.  In this case, the court affirmed an inter partes reexamination (IPR) decision of the Patent Trial and Appeal Board (PTAB) that affirmed the examiner’s rejection of claims in U.S. Patent 6,673,532 (“’532 patent) as obvious despite the plaintiff’s “changes the principle of operation” argument. Although the decision is non-precedential, it provides helpful information to patent practitioners and litigators for arguing obviousness based on changes to a reference’s fundamental principle of operation.

The ’532 patent discloses an optical method of monitoring various cell culture parameters. Claim 1 of the ’532 patent, deemed as representative, reads as follows:

1. A method of measuring at least two cultivation parameters in a cell culture, comprising:

• (a) providing a cultivation vessel, wherein the cultivation vessel comprises, walls that define a single continuous volume or a non-planar surface that defines a single continuous volume, and at least two types of optical chemical sensors posi­tioned within the single continuous volume;

• (b) placing a continuous culture medium within the single continuous volume of the cultivation vessel such that the continuous culture medium is in contact with at least one of the walls that define the single continuous volume of the cultivation vessel or the non-planar surface that defines the single continuous volume of the cultivation vessel, wherein the optical chemical sensors are positioned such that they are in contact with the continuous culture medium;

• (c) establishing a cell culture in the continuous culture medium;

• (d) exciting the optical chemical sensors to generate emission and/or light absorption, wherein the optical chemical sensors are excited using at least one excitation source per optical chemical sensor;

• (e) detecting the emission and/or absorption generated by the at least two optical chemical sensors in (d) by at least one detector for each type of optical chemical sensor used; and

• (f) analyzing the detected emission and/or absorption detected in (c) to assess the at least two cultivation parameters measured.

As affirmed by the Board, the examiner rejected the claims as obvious over two journal articles referred to as Bambot and Weigl.  The court stated that “Bambot described optical methods of measuring analytes such as glucose, pH, and oxygen and carbon dioxide levels in bioreactors.  The methods in Bambot implemented the same set of components as the ’532 patent.  Various cultivation vessels housed sensors excitable by several types of excitation sources, and the sensors’ emissions could be measured by several different detectors.”  Similarly, as stated by the court, “Weigl described a triple sensor device for measuring pH, oxygen, and carbon dioxide in a cultivation vessel. In Weigl, however, the sensors were located in individual flow-through units outside the cultivation vessel. Each unit had a dedicated excitation source and detector. Given the teachings of Bambot and Weigl in combination, the examiner concluded that the claims of the ’532 patent would have been obvious over the references at the time the invention was made.”

The 1959 decision In re Ratti is the case typically cited in support of finding obviousness under a “changes the principle of operation” argument.  Maryland argued that Ratti did not support a finding of obviousness here because the combination of Bambot and Weigl would completely change Weigl’s principle of operation since Weigl’s sensors are outside its cultivation vessel.

On appeal, the court affirmed the Board’s decision despite the plaintiff’s “changes the principle of operation” argument.  The Board, agreeing with Presens, held that Maryland misapplied Ratti and that Weigl was relied upon in the rejection for parameters measured by the sensors rather than the configuration of the sensors. The court noted that a “person of ordinary skill is ‘not an automaton’ limited to physically combining references” and that the two cited references “taught every element of the claimed invention and the combination of the references accords with their teachings.”

As such, this case highlights the difficulty that may arise in overcoming obviousness rejections using the “changes the principle of operation” argument and that careful consideration of how references are being applied and accordant use of such argument is advised.