Appeal 2007-1633
Application 09/480,236
relative to each other, it cannot be denied that both have the property of
being an immunotoxin. Accordingly, the immunotoxin properties of the
prior art and claimed immunotoxins have not been ignored on this record.
Now, while Appellants emphasize the differences in activity between
DT and PE based immunotoxins, we note that there is no requirement in
Appellants’ claim 35 that the recombinant immunotoxin polypeptide be used
for any particular purpose or have any activity other than ADP-ribosylating
and translocation functions but substantially diminished cell-binding ability.
Notwithstanding Appellants’ argument that DT and PE based immunotoxins
exhibit different activities relative to one another, there is no requirement in
claim 35 that the recombinant immunotoxin polypeptide perform in a
particular manner relative to another immunotoxin.
Therefore, the issue before this panel is whether it would have been
prima facie obvious to a person of ordinary skill in the art at the time the
invention was made to substitute the DT component of Neville’s
recombinant immunotoxin polypeptide with a PE mutant. In this regard, we
note that Neville teaches that “[i]n contrast with . . . Pseudomonas exotoxin
(PE) based immunotoxins, there is a potential problem using UCHT1-
CRM9, or other DT-based immunotoxins, in the treatment of human
diseases” (Neville, col. 22, ll. 13-16). Specifically, Neville teaches that
“[m]ost people have a pre-existing anti-DT antibody titer which could
potentially inhibit or alter the efficacy of these [DT based] immunotoxins”
(Neville, col. 22, ll. 16-19). Accordingly, Neville goes about making DT
mutants to circumvent “the inhibitory effect of pre-existing anti-DT
antibodies” (Neville, col. 22, ll. 28-34). Thus, Neville recognizes an
advantage in the use of PE relative to DT as a component of an
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