Patent ID: 7834138

Claim:
A composition comprising (i) a pharmaceutical carrier and (ii) a conjugate of a water soluble polymer and a pharmacologically active agent, wherein the pharmacologically active agent is covalently attached to the water soluble polymer via a functional group Y, and wherein the water soluble polymer comprises: (a) a first water soluble polymer segment which is at least 4 and at most about 2000 monomeric units in length (POLY A ), wherein POLY A is end-capped with a capping group selected from C 1 -C 20 alkoxy and C 1 -C 20 aryloxy; (b) a second water soluble segment which is 1 to about 120 monomeric units in length (POLY B ), wherein the molecular weight of POLY A is at least four times that of POLY B; (c) a linkage X, which covalently attaches POLY A to POLY B and is distinct from the monomeric units of the polymer segments, wherein X is an amide, a carbamate, an ester, a urea, an amine, a thioether, or a disulfide linkage; one or more optional spacer groups linking X to POLY A or to POLY B , wherein such a spacer group is hydrolytically stable and includes bonds selected from alkyl, ether, keto, amide, urea, and sulfide; and (d) said functional group, Y, attached to POLY B at a terminus or branch point which is distal to linkage X; wherein each of POLY A and POLY B independently comprises one monomer or up to three different monomers selected from the group consisting of alkylene glycol, olefinic alcohol, vinylpyrrolidone, hydroxyalkylmethacrylamide, hydroxyalkylmethacrylate, saccharide, α-hydroxy acid, phosphazene, oxazoline, and N-acryloylmorpholine.