Biotinidase-resistant biotinylated compound and methods of use thereof

DETAILED DESCRIPTION This invention relates to biotinidase-resistant biotinylated compounds containing a chemical fragment having the structure: ##STR2## wherein R.
sub.
1 and R.
sub.
3 are independently hydrogen, carboxyl or lower alkyl and R.
sub.
2 is O or NH and X is S or a chemical bond.
The biotinylated compounds of the present invention are stable in vivo and capable of binding avidin and streptavidin.
In a preferred embodiment, the chemical fragment has the structure: ##STR3## and is covalently bound, directly or by a linker to a moiety which is useful in diagnosis or therapy.
In a preferred embodiment, the moiety is a chelating agent, a halogenating agent, a toxin, a chemotherapeutic drug, a fluorophore or an enzyme.
The present invention provides biotinylated compounds having the formula: ##STR4## wherein the negative charge on the carboxylate is balanced by a cation and wherein R.
sup.
1 and R.
sup.
3 are independently hydrogen, carboxyl or lower alkyl; R.
sub.
2 is O or NH; X is a chemical bond or a linking group and M is a diagnostic or therapeutic moiety.
In a preferred embodiment, R.
sub.
1 and R.
sub.
3 are H, R.
sub.
2 is 0, X is S-Y wherein Y is a chemical bond, acetyl or a C1-C6 alkylene chain, and M is a chelating agent, a halogenating agent, a toxin, a chemotherapeutic drug, a fluorophore or an enzyme.
The present invention further provides the biotinylation reagent N-cysteinyl-biotin.
A further aspect of the present invention provides a method for biotinylating a molecule wherein said method comprises reacting the molecule with N-cysteinyl-biotin.
A further aspect of the present invention provides a method of delivering a diagnostic or therapeutic agent to a target site.
The method of delivery of a diagnostic agent comprises administering an avidin or streptavidin conjugated targeting agent to a host in an amount sufficient to bind to a target site, followed by administering a detectable biotinylated compound of the present invention under conditions to form a complex with said avidin or streptavidin conjugated targeting agent and at a dose sufficient for detection