Appeal No. 2006-0656 Page 5
Application No. 10/086,637
to excess free, dual specificity conjugate” inasmuch as “multiple simultaneous binding to
receptors distributed at the external side of the . . . target cells may be much stronger
than monovalent binding to the same receptors in solution” (id., column 4, lines 22-31).
According to the examiner, “[i]t would have been obvious to one of ordinary skill
in the art to modify the methods of radiodiagnosis disclosed by Goldenberg by
administering a radiolabeled hapten and a bispecific antibody having a second binding
site to the hapten” because Barbet teaches that “methods of radiodiagnosis . . . can be
made more effective by [ ] a two-step approach of administering a bispecific antibody
and a labeled hapten, wherein the bispecific antibody has a binding site for both the
target . . . and the hapten” (Examiner’s Answer, page 4).
Even if we were to accept the examiner’s reasoning regarding a “two-step”
versus “one-step” approach, however, we note that, at a minimum, the examiner has
not adequately addressed the claims’ requirement for “a bispecific antibody fragment or
subfragment with a molecular weight of 85,000 daltons or less” (e.g., claim 183).
It is fair to say that both Goldenberg and Barbet teach “that antibody fragments
(such as[ ] Fab and Fab’ fragments . . .) are [ ] useful and/or art recognized equivalents
to other antibodies” and their use “is commonplace in radioimmunodiagnostics”
(Examiner’s Answer, page 8). It is also the case that Fab and Fab’ fragments have
molecular weights of less than 85,000 daltons. However, Fab and Fab’ fragments are
monovalent, and therefore, cannot possibly meet the present claims’ requirement for a
“bispecific antibody fragment” with “a first antibody binding site which specifically binds
to an antigen . . . and [ ] a second antibody binding site which specifically binds to a
hapten” (e.g., Claim 183).
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