Appeal No. 2001-1580 Page 9
Application No. 08/955,090
F.2d 303, 313, 203 USPQ 245, 254 (CCPA 1979) (“An obviousness rejection
based on similarity in chemical structure and function entails the motivation of
one skilled in the art to make a claimed compound, in the expectation that
compounds similar in structure will have similar properties.”). Here, by contrast,
the evidence shows that circular permutation has an unpredictable effect on a
ligand’s activity. Thus, even though a circularly permuted ligand has some
structural similarity to the native ligand, that similarity does not carry with it an
expectation that the two compounds will share similar properties.
Pastan’s disclosure that one circularly permuted ligand has improved
properties may have made it obvious to try circularly permuting other ligands, but
none of the cited references suggests any reason to circularly permute flt3 ligand
specifically. In addition, the prior art as a whole shows that the effect of circular
permutation was unpredictable. Thus, the evidence of record does not show that
a skilled artisan, with no knowledge of the claimed invention, would select the
known circular permutation method and the known flt3 ligand for combination in
the manner claimed. Cf. Ecolochem, Inc. v. Southern Calif. Edison Co., 227 F.3d
1361, 1375, 56 USPQ2d 1065, 1075 (Fed. Cir. 2000) (An adequate showing of
motivation to combine requires “evidence that ‘a skilled artisan, confronted with
the same problems as the inventor and with no knowledge of the claimed
invention, would select the elements from the cited prior art references for
combination in the manner claimed.’”). The cited references therefore do not
support a prima facie case of obviousness.
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