Patent ID: 8722032

Claim:
A method for a preparing a conjugate, said method comprising: reacting a water-soluble polymer, POLY-L 0,1 -E, comprising a water-soluble polymer segment (“POLY”), an optional linker, “L,” and having one terminus activated with an electrophile (“-E”) with a symmetrical disulfide reagent, (NU—Y—S-) 2 ,wherein NU is a nucleophile (“-NU”) Y is a linear group (“-Y-”) and S and is a sulfur atom, under conditions effective to promote reaction between said electrophile and said nucleophile to form a polymer product of the structure POLY-L 0,1 -X—Y—S—S—Y—X-L 0,1 -POLY, wherein the molecular mass of the water-soluble polymer segment is from 1,000 Daltons to 50,000 Daltons; reducing the disulfide bond in POLY-L 0,1 -X—Y—S—S—Y—X-L 0,1 -POLY to form POLY-L 0,1 -X—Y-SH and reacting the POLY-L 0,1 -X—Y—SH with a biologically active agent comprising a thiol group, to thereby result in a conjugate.