Appeal No. 1999-1155
Application No. 08/241,253
The present invention is directed to monomeric or multimeric metal-chelating
compounds “having enhanced relaxivities.”3 The compounds are “useful in the form of
metal complexes as diagnostic contrast agents,” and “[w]hen the metal in the complex
is paramagnetic, the diagnostic contrast agents are especially suitable for magnetic
resonance imaging (MRI).” Specification, page 1. According to appellants, “[c]ontrast
agents with significantly enhanced relaxivities are of great interest . . . because they
offer improved efficiency at reduced doses for current clinical applications” and “also
because they may provide the sensitivities needed for imaging various biochemical
processes.” Id., at page 11. “In one embodiment of the invention [e.g., claim 1], certain
specific compounds comprise a tetraazacyclododecane macrocycle.” Id., at page 1. In
another embodiment, two or more tetraazacyclododecane monomers may be “linked by
a cyclic bridging group” comprising “a 4- to an 8-membered carbocyclic ring.” Id., at
pages 7 and 8. In yet another embodiment of the invention (e.g., claim 5), the 4- to 8-
membered carbocyclic ring links two or more monomers, wherein each monomer can
be “any moiety capable of chelating a metal atom.” Id., at page 8.
DISCUSSION
3 According to the specification, “[t]he expression ‘relaxivity’ refers to the
effectiveness of a metal chelate to reduce the relaxation time of bulk water in contact
with the metal chelate,” while “[t]he expression ‘enhanced relaxivity’ refers to relaxivity
values made greater than those of well characterized prior art molecules by [] altering
the electronic relaxation rate, Js, through modifications of the of the metal-donor atom
bond vibration frequencies and/or amplitudes, . . . in a multimer by decreasing the
internal molecular motion of one monomer relative to another . . . or, [] by decreasing
the molecular reorientation of a monomer or a multimer attached to a large moiety or
physiological surface.” Pages 3 and 4.
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