dissenting.
Although the majority opinion traces through a very unclear Board decision and tries with a substantial degree of specificity to supply a reasoned basis for the Board’s decision, I respectfully dissent from the majority opinion because there is no reasoned basis for the Board’s decision and there is no substantial evidence to support the PTO’s finding of obviousness. SEC v. Chenery Coup., 332 U.S. 194, 195, 67 S.Ct. 1575, 91 L.Ed. 1995 (1947); Colorado Interstate Gas Co. v. FPC, 324 U.S. 581, 595, 65 S.Ct. 829, 89 L.Ed. 1206 (1945). But see In re Huston, 308 F.3d 1267 (Fed.Cir.2002).
The Board held claims 64-73 of the Vel-ander '184 application unpatentable for obviousness. Velander argues on appeal that there is no substantial evidence to support the Board’s finding that one of ordinary skill in the art had a reasonable expectation of success regarding the production of fibrinogen in the milk of a transgenic mammal. Whether an invention is obvious is ultimately a legal conclusion. We must determine if “the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art to which said subject matter pertains.” 35 U.S.C. § 103. The factual inquiries underlying obviousness include (1) the scope and content of the prior art, (2) the differences between the prior art and the claims at issue, (3) the level of ordinary skill in the art at the time the invention was made, and (4) any objective evidence of nonobvi-ousness. Graham v. John Deere Co., 383 U.S. 1, 17-18, 86 S.Ct. 684, 15 L.Ed.2d 545 (1966). “The consistent criterion for determination of obviousness is whether the prior art would have suggested to one of ordinary skill in the art that this process should be carried out and would have a reasonable likelihood of success, viewed in the light of the prior art.” In re Dow Chem. Co., 837 F.2d 469, 473 (Fed.Cir.1988). Obviousness requires one of ordinary skill in the art have a reasonable expectation of success as to the invention — “obvious to try” and “absolute predictability” are incorrect standards. In re O'Farrell, 853 F.2d 894, 903 (Fed.Cir.1988). The presence of a reasonable expectation of success is measured from the perspective of a person of ordinary skill in the art at the time the invention was made. Life Techs., Inc. v. Clontech Labs., Inc., 224 F.3d 1320, 1326 (Fed.Cir.2000). To this end, the ultimate success of the invention is irrelevant. Id.
The Board’s decision should pave the way to meaningful appellate review. In its decision, the Board is obligated not only to make the requisite findings based on the evidence of record, but also to explain the reasoning underlying its findings. In re *1380Lee, 277 F.3d 1338, 1344-45 (Fed.Cir.2002). Our review of the Board’s decision for substantial evidence should be restricted to the grounds relied on by the Board. See id. (“[Rjeview of an administrative decision must be made on the grounds relied on by the agency. ‘If those grounds are inadequate or improper, the court is powerless to affirm the administrative action by substituting what it considers to be a more adequate or proper basis.’ ” (quoting Chenery, 332 U.S. at 196, 67 S.Ct. 1575)); see also In re Zurko, 258 F.3d 1379, 1385 (Fed.Cir.2001) (rejecting the PTO’s argument for this court to consider additional references not relied on by the Board in reaching its conclusion of obviousness because the references did not support the Board’s conclusion and, moreover, “would constitute a new ground for rejection, not considered or relied upon by the Examiner or the Board”).
Here, the Board explicitly supported its finding of reasonable expectation of success on the Hennighausen review and Meade patent. In particular, the Board found persuasive the fact that both references discussed the production of blood proteins via transgenic animals:
The Hennighausen review in particular touts the use of transgenic animals for the very class of pharmaceutical proteins (blood serum proteins) to which fibrinogen belongs. Similarly, Meade obtained a patent for production of a blood protein in transgenic mammal milk. The problems identified in the art are not presented as insurmountable or unique to blood proteins.
The Board thus found that one of ordinary skill in the art1 would have believed, on the critical date,2 that there was a reasonable chance of producing fibrinogen in view of the fact that the expression of other blood proteins in transgenic animals was disclosed in the Hennighausen review and Meade patent.
This finding, however, was unsupported by substantial evidence because it was based on the Board’s unsupported assumption, or alternatively, unsupported finding, as to the second Graham factor: the difference between the prior art and the claims at issue, as viewed from the vantage point of one of ordinary skill in the art. The Board’s decision reveals its implicit assumption that one of ordinary skill in the art would have perceived the difference between the disclosed blood proteins and fibrinogen to be insignificant. Even assuming that this implicit assumption constituted an actual “finding” by the Board, it was unsupported by any evidence, let alone substantial evidence, that one of ordinary skill in the art would have agreed that the mere disclosure of blood proteins in the prior art would have led one of ordinary skill in the art to believe that fibrinogen could be expressed in transgenic non-human mammals. As we explained in Zurko:
As an administrative tribunal, the Board clearly has expertise in the subject matter over which it exercises jurisdiction. ... With respect to core factual findings in a determination of patentability, however, the Board cannot simply reach conclusions based on its own understanding or experience- — or on its assessment of what would be basic knowledge or common sense. Rather, the Board must point to some concrete evi*1381dence in the record in support of those findings. To hold otherwise would render the process of appellate review for substantial evidence on the record a meaningless exercise.
Zurko, 258 F.3d at 1385-86 (citing Baltimore & Ohio R.R Co. v. Aberdeen & Rockfish R.R. Co., 393 U.S. 87, 91-92, 89 S.Ct. 280, 21 L.Ed.2d 219 (1968)).
While we cannot step into the shoes of one of ordinary skill in the art, I believe that the Board’s functional definition, accepted by the majority, of fibrinogen as a blood protein was misguided. The Board implies that the mere disclosure of the production of blood proteins, in general, via transgenic animals renders obvious the expression of any other blood protein in the same way, even where the target blood protein is so much more structurally complex that one of ordinary skill in the art would be hard-pressed to determine how to produce it via transgenic means. For example, the blood protein that could be encoded from multiple genes is large and requires post-translational processing that is not controlled by any human mammary genes. Potential problems faced by one of ordinary skill might include co-integration of the three genes encoding the fibrinogen protein into the foreign genome, proper assembly and bonding of the six chains of the protein once expressed, and proper secretion of the protein from the mammary gland into the milk of the lactating animal.3 The Board’s classifieatory framework of fibrinogen as blood protein seems irrelevant to resolving such potential issues.
The Board failed to determine (1) the difference, if any, between the prior art and the claims at issue as perceived by one of ordinary skill in the art, and (2) whether that difference, if any, is so significant that one of ordinary skill in the art would not entertain a reasonable expectation of success of expressing fibrinogen in transgenic non-human mammals.
For these reasons, I respectfully dissent.
. The Board adopted Velander’s definition of one of ordinary skill in the art as of the critical date as having been "knowledgeable and experienced in the expression of heterolo-gous proteins in the milk of transgenic animals," and not just having mere familiarity with transgenics.
. The critical date for determining patentability under 35 U.S.C. §§ 102(b) and 103 is February 18, 1993, one year before the filing date of the '068 application.
. Velander raises exactly these sorts of issues on appeal, arguing that one of ordinary skill in the art would have perceived the expression of fibrinogen in transgenic animals as a formidable task due to the structural complexity of fibrinogen. For example, Velander notes that fibrinogen is not only (1) much larger than the disclosed proteins in the prior art produced in the milk of transgenic animals, but (2) derived from three genes, as opposed to one or two. Velander claims that the fact that three separate genes are necessary to produce the alpha, beta and chains of the fibrinogen protein creates unique considerations as to the transgenic production of fibrinogen. In this last regard, Velander’s experts testified that the assembly of the six chains of fibrinogen was uncertain due to additional difficulties of co-integrating the genes and assembling the final protein. The Board did not acknowledge these relevant arguments in its decision.