Appeal No. 2001-1293 Page 5
Application No. 08/464,271
scope of: (1) the tissue types subject to ablation; (2) the organisms in which the
method is carried out; (3) the exogenous enzymes expressed; and (4) the tissue-
specific promoter used.
With respect to the scope of tissue types, organisms, and promoters, the
examiner has not convincingly shown that undue experimentation would have
been required to practice the claimed method. The specification provides a list of
tissue-specific promoters that are expressed only in B-lymphocytes, specific
populations of T-lymphocytes, pituitary cells, and adrenal medullary and
sympathetic neuron cells. See page 8. The specification also states that the
exogenous DNA can be introduced into the appropriate cells by a variety of
known methods, including infection with retroviral constructs, microinjection, or
transfection. See pages 11-12. Finally, the specification provides working
examples showing specific killing, upon exposure to a nucleoside analog, of
spleen and thymus cells (and lymphoma cells in one experiment) in transgenic
mice transformed with a construct encoding HSV-TK under the control of an
immunoglobulin light-chain promoter and heavy-chain gene enhancer. See
pages 23-37.
The examiner has conceded that the specification is enabling for ablation
of lymphoid cells in mice using the exemplified system (Examiner’s Answer, page
6), but asserted that the record lacks evidence to show that “transgenic animals
of any and all species [could be produced] such that specific ablation of a desired
cell population can be achieved without undue experimentation.” Examiner’s
Answer, page 6. The examiner concluded that the enabling scope of the
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