Appeal No. 2003-0177 Page 3
Application No. 09/231,642
restriction requirement, claim 1 has only been examined to the extent that the antibody
is specific to carcinoembryonic antigen (CEA). See Paper No. 8, page 3 ("The claims
encompass non-elected embodiments. These claims will be examined only to the
extent they read on a targeting moiety comprising an antibody specific to CEA linked to
a ligand binding region of IL-13R"."). Thus, it appears that claim 6 reflects the subject
matter which has been examined by the examiner on the merits and thus before us for
review in this appeal.
Eshhar describes a conjugate which also comprises an antibody and a ligand-
binding region of a cellular receptor. Specifically, the antibody portion of the Eshhar
conjugate is a single-chain Fv domain (scFv) of a specific antibody. Eshhar, page 7,
lines 9-16. A preferred embodiment of Eshhar is that the conjugate is to target tumor
cells and the scFv domain is derived from an antibody specific to an epitope expressed
on the tumor cell. Id., page 19, lines 7-9. There is no dispute on this record that CEA
would have been an obvious choice to one of ordinary skill in the art in designing the
conjugate of Eshhar to target tumor cells. As set forth by appellants:
CEA is a glycosylated cell surface protein of approximately 180 kDa,
and is a solid tumor antigen that has been extensively studied clinically,
both as a circulating tumor marker and as an antigenic target for
radiolabeled mAbs for imaging and therapy. A number of anti-CEA
antibodies have been under study in phase I-III clinical diagnostic and
therapeutic trials. Exemplary of an anti-CEA mAb is the MN-14mAb. A
humanized version of this mAb, hMN-14, in which human constant and
framework regions replace the corresponding mouse sequences, has
been constructed and expressed and is the mAb and used in these
clinical trials. A 99mTc-labeled Fab' fragment of another, related anti-CEA
mAb, Immu-4, has received FDA approval for the detection and staging of
colon cancer.
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