The invention
1. In the "Background and Prior Art" portion of
the specification, we are told that (page 1, lines 18 to page 2,
line 12)(matter in [brackets] added):
Parkinson's disease is associated with the depletion of
dopamine[3] from cells in the corpus striatum. Since
dopamine does not cross the blood brain barrier and cannot
therefore be used to treat Parkinson's disease, its
immediate precursor, levodopa, [4] is used instead because it
penetrates the brain where it is decarboxylated [5] to
dopamine. But levodopa is also decarboxylated to dopamine
in peripheral tissues and consequently only a small portion
of administered levodopa is transported unchanged to the
brain. This reaction can be blocked by carbidopa [6] which
inhibits decarboxylation of peripheral levodopa but cannot
itself cross the blood brain barrier and has no effect on
the metabolism of levodopa in the brain.
The combination of carbidopa and levodopa is considered
to be the most effective treatment for symptoms of
Parkinson's disease (The Medical Letter, 35:31-34, 1993
[copy in the record]). Nevertheless, certain limitations
become apparent within two to five years of initiating
combination therapy. As the disease progresses, the benefit
from each dose becomes short ("the wearing off effect") and
3 The formula of dopamine is shown in entry 3479 from The Merck Index,
CD-ROM, Version 12:1a, ISSN 1359-2947 (12th ed. 1996). A copy of the entry is
found in an Appendix attached to our opinion.
4 The formula of levodopa is shown in entry 5490 from The Merck Index,
CD-ROM, Version 12:1a, ISSN 1359-2947 (12th ed. 1996). A copy of the entry is
found in an Appendix attached to our opinion.
5 Decarboxylate means remove a )COOH group.
6 The formula of carbidopa is shown in entry 1843 from The Merck Index,
CD-ROM, Version 12:1a, ISSN 1359-2947 (12th ed. 1996). A copy of the entry is
found in an Appendix attached to our opinion.
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