Stabilized polymeric thiol reagents

1. A polymer conjugate comprising the structure:

POLY-[Y—S—S-A] x

wherein:

POLY is a water soluble polymer which is a polyethylene glycol;

Y is a divalent linking group consisting of a saturated hydrocarbon backbone which is 4 to 6 carbon atoms in length and has substitutents selected from the hydrogen and methyl;

S—S is a disulfide group attached to an sp 3 hybridized carbon of Y; and

A is a covalently linked residue of a pharmacologically active molecule; and

x is 1 or 2.

2. The conjugate of claim 1 , wherein said conjugate is water soluble.

3. The conjugate of claim 1 , wherein each of R 1 and R 2 is hydrogen.

4. The conjugate of claim 1 , wherein said pharmacologically active molecule has a reactive thiol group in its unconjugated form and is selected from the group consisting of proteins, peptides, and small molecules.

5. The conjugate of claim 1 , comprising the structure A-S—S-Y-POLY-Y-S—S-A.

6. The conjugate of claim 5 , wherein the Y groups are identical.

7. The conjugate of claim 1 , in combination with a pharmaceutical excipient.

8. The conjugate of claim 7 , wherein said pharmaceutical excipient is an aqueous carrier.

9. The conjugate of claim 1 , wherein x is 1.

10. The conjugate of claim 1 , wherein x is 2.

11. A composition comprising, in a pharmaceutically acceptable carrier, a conjugate having the structure:

POLY-[Y—S—S-A] x

wherein:

POLY is a water soluble polymer which is a polyethylene glycol;

Y is a divalent linking group consisting of a saturated hydrocarbon backbone which is 4 to 6 carbon atoms in length and has substitutents selected from the hydrogen and methyl;

S—S is a disulfide group attached to an sp 3 hybridized carbon of Y; and

A is a covalently linked residue of a pharmacologically active molecule, wherein said pharmacologically active molecule has a reactive thiol group in unconjugated form; and

x is 1 or 2.