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Prior Art Combinations Cannot Substantially Reconstruct the Primary Reference – But POSITAs Are Not Limited to Physically Combinable References

Samuel Drezdzon
Haynes and Boone, LLP

In University of Maryland Biotech Institute v. Presens Precision Sensing, Nos. 2016-2745, 2017-1057 (Nov. 3, 2017) (nonprecedential) (“UMBI”), the Federal Circuit affirmed the USPTO Patent Trial and Appeal Board’s (“PTAB”) inter partes reexamination decision that found U.S. Patent No. 6,673,532 (“the ’532 patent”) invalid as obvious over two prior art references.

The Federal Circuit’s decision highlighted that, while “a person of ordinary skill generally would not be motivated to modify a reference by contradicting its basic teachings [or] by making it inoperable for its intended purpose,” portions or elements of a secondary reference may be combined with and adapted to the particular physical arrangement of a primary reference even if the secondary reference discloses a different or incompatible physical arrangement.  Id. at 6 (citations omitted).


The University of Maryland Biotechnology Institute (“UMBI”) owns the ’532 patent, which is directed to methods for measuring and optimizing the parameters of in vitro cell cultivation.  In particular, the ’532 patent’s claims include a cell cultivation bioreactor with optical-chemical sensors that emit light during cultivation when exposed to an excitation source such as an LED; the light from the optical-chemical sensors is then detected and analyzed in order to measure cultivation parameters such as pH, dissolved oxygen, carbon dioxide, or glucose concentration.  Importantly, as it relates to the obviousness challenge, the ’532 patent’s claims recite that the optical-chemical light sensors are located within the cultivation vessels themselves, as opposed to being located outside of the cultivation vessels.  Additionally, the dependent claims recite a separate detector and excitation source for each type of sensor.

In an inter partes reexamination proceeding brought by Presens Precision Sensing (“Presens”), the examiner rejected the claims as obvious in view of a combination of two prior art references.  The combination’s primary reference, “Bambot,” discloses optical methods of measuring analytes such as glucose, pH, and oxygen using a reactor where the light sensors are included within cultivation vessels themselves.  The examiner combined Bambot with a second prior art reference, “Weigl,” for its disclosure of monitoring multiple parameters using a separate detector and excitation source for each type of sensor.  However, in Weigl’s reactor, the light sensors are located outside of the cultivation vessels.

The PTAB affirmed the examiner’s obviousness rejection.  Presens Precision Sensing GmbH v. Univ. of Md. Biotechnology Inst., No. 2015-006297, 2015 WL 9581532 (P.T.A.B. Dec. 29, 2015), reh’g denied, (P.T.A.B. July 29, 2016).  The PTAB agreed that Bambot disclosed the light sensors located inside a cultivation vessel, and in view of Weigl’s teachings it would be obvious to use a separate detector and excitation source for each type of sensor.

Federal Circuit Appeal

On appeal, the appellant UMBI argued that because Weigl’s sensors are located outside of the cultivation vessel, the prior art combination improperly modified Weigl in view of Bambot because it completely changed Weigl’s fundamental principle of operation.  UMBI at 6.

In response, the appellee Presens took the position that UMBI misinterpreted the PTAB’s reliance on Weigl, arguing that the PTAB did not find the claims obvious by modifying the configuration of Weigl’s sensors, but rather based its obviousness conclusion on Bambot’s sensor configuration (not Weigl’s) and relied on Weigl only for its teaching of measuring multiple parameters and using a separate detector and excitation source for each sensor.  Id.

The Federal Circuit agreed with Presens.  First, the Court explained that under its precedent it must “exercise caution before holding a claimed invention obvious when combining references would violate the principle of operation of the modified reference.  This is because a person of ordinary skill generally would not be motivated to modify a reference by contradicting is basic teachings or by making it inoperable for its intended purpose.”  Id. at 5-6 (citations omitted).  Indeed, as stated differently in the case In re Ratti, 270 F.2d 810, 813 (CCPA 1959) relied upon by UMBI, it is improper if the “suggested combination of references would require a substantial reconstruction and redesign of the elements shown” or a “change in [its] basic principles.”  270 F.2d at 813.

However, the Federal Circuit then explained that, at the same time, a person of ordinary skill in the art (“POSITA”) is “not an automaton . . . limited to physically combining references.”  UMBI at 6 (quoting KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 421 (2007)).  In particular, the Court found that UMBI misapplied Ratti because, “even assuming that extra-vessel sensors are a ‘basic principle’ of Weigl, that principle is independent of Weigl’s pertinence to the Board’s obviousness determination.  Id.  The Court further explained that:

“The Board’s findings regarding Weigl are consistent with Bambot’s principle of operation, as substantial evidence also supports the Board’s findings that Bambot taught intra-vessel sensors in addition to multiple types of sensors, detectors, and excitation sources, and that Bambot suggested measuring multiple analytes in cultivation Vessels …  Bambot and Weigl taught every element of the claimed invention and the combination of the references accords with their teachings.  ‘The combination of familiar elements according to known methods is likely to be obvious when it does no more than yield predictable results.’”  Id. at 7 (quoting KSR, 550 U.S. at 416).

In other words, the Federal Circuit concluded that even though physically combining the entirety of Bambot’s bioreactor with the entirety of Weigl’s bioreator may not result in a clearly operational system (as Bambot’s light sensors are located inside a cultivation vessel and Weigl’s are located outside the cultivation vessel, raising the  question of whether that combined system would have its sensors located inside or outside the cultivation vessel), the references may still be combined under obviousness grounds.  Id.  As such, the Court reiterated the Supreme Court’s somewhat nebulous language from KSR that a POSITA is “not an automation,” and this case suggests this means that a POSITA is not limited to only combining systems or structures that could be automatically combined together without any conflicts between the structure and basic elements of the first reference with those of the second reference.  Rather, a POSITA may combine references in a way that may not be automatically apparent when looking at each reference as a whole; a POSITA may thus select one reference as a primary reference and modify part of its structure or functionality to include an element or concept disclosed by a secondary reference.

Additionally, the Court addressed UMBI’s argument that Weigl “teaches away” from the claimed invention because, for example, Weigl’s units have only one sensor and not multiple sensors, and Weigl’s various outlets are also inconsistent with the claimed invention’s “continuous volume” limitation.  Id. at 8.  The Court again agreed with Presens that UMBI’s teaching away arguments did not demonstrate PTAB error.  Specifically, the Federal Circuit found that UMBI’s arguments once again narrowly focused on the physical arrangement of Weigl and that its “mere disclosure of alternative designs does not teach away,” but instead “teaching away requires clear discouragement from implementing a technical feature.”   Id. (citations omitted).


This case highlights that, when combining prior art references to challenge claims as obvious, it is not necessary that the combined system or structure account for and reconcile all elements/structures taught by each reference to result in a fully operational system or structure, no matter how basic or fundamental the irreconcilable element/structure may be.  Instead, Practitioners should also consider prior art combinations where a primary reference is combined with or modified to include just part of the secondary reference’s structure, or merely an idea or concept taught by the second reference.  Utilizing this approach expands the universe of prior art available to Practitioners for forming prior art combinations.

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