Appeal No. 2002-2279 Page 7
Application No. 08/556,667
density of the cells of interest” (see e.g., claims 4 and 5) and we too conclude that the
examiner has not made out a prima facie case of obviousness.
As explained in In re Kotzab, 217 F.3d 1365, 1369-70, 55 USPQ2d 1313, 1316
(Fed. Cir. 2000):
A critical step in analyzing the patentability of claims pursuant to section
103(a) is casting the mind back to the time of invention, to consider the
thinking of one of ordinary skill in the art, guided only by the prior art
references and the then-accepted wisdom in the field. [ ] Close adherence
to this methodology is especially important in cases where the very ease
with which the invention can be understood may prompt one “to fall victim
to the insidious effect of a hindsight syndrome wherein that which only the
invention taught is used against its teacher.” [ ]
We have no doubt that the prior art could be modified in a manner consistent with
appellants’ specification and claims. The fact that the prior art could be so modified,
however, would not have made the modification obvious unless the prior art suggested
the desirability of the modification. In re Gordon, 733 F.2d 900, 902, 221 USPQ 1125,
1127 (Fed. Cir. 1984).
In this case, the claims on appeal place a specific limitation on the particles used
in the claimed methods - the particles must have a density at least twice that of the cells
of interest. The fact that the claims do not specify a particular “starting material” or cell
of interest as a reference point for the density of the particles does not mean that the
limitation can be met by any particles which happen to have a density twice that of
some cell type. Assuming that one skilled in the art would have been motivated to use
the methods and materials of Grenier or Pry to purge Reynolds’ bone marrow cells of
neuroblastoma cells, there must still have been some reason or suggestion in the prior
art to use particles at least twice as dense as Reynolds’ bone marrow cells (the “starting
material” or reference point in this case) in order to meet the limitations of the claims.
We do not find evidence of such a reason or suggestion in the references relied
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