Progammable polymeric drugs

A compound having the following structure (II):

• or a stereoisomer, pharmaceutically acceptable salt or tautomer thereof, wherein:
• G is, at each occurrence, independently a moiety comprising a reactive group capable of forming a covalent bond with a complementary reactive group, the reactive group is selected from the group consisting of:
• an aldehyde, oxime, hydrazone, alkyne, amine, azide, acylazide, nitrile, nitrone, sulfhydryl, disulfide, sulfonyl halide, isothiocyanate, imidoester, activated ester, ketone, α,β-unsaturated carbonyl, alkene, maleimide, α-haloimide, epoxide, aziridine, tetrazine, tetrazole, phosphine, biotin and thiirane;
• L1a is, at each occurrence, independently an optional alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene or heteroatomic linker;
• L1, L2, L3 and L4 are, at each occurrence, independently an optional heteroalkylene linker, wherein at least one of L1 and L4 is present;
• R1 is, at each occurrence, independently a side chain of a natural or unnatural amino acid;
• R2 is —NH2;
• R3 is —H, —OH, —SH, alkyl, alkoxy, alkylether, heteroalkyl, alkylaminyl, alkylcarbonyl, alkoxycarbonyl, Q or a protected form thereof, or L′, wherein the alkyl, alkoxy, alkylether, heteroalkyl, alkylaminyl, alkylcarbonyl and alkyloxycarbonyl are optionally substituted with hydroxyl, amino, sulfhydryl, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether or thiophosphoalkylether, or combinations thereof;
• Q is, at each occurrence, independently a moiety comprising a sulfhydryl, disulfide, activated ester, isothiocyanate, azide, alkyne, alkene, diene, dienophile, acid halide, sulfonyl halide, phosphine, α-haloimide, biotin, amino or maleimide functional group, wherein the activated ester is an N-succinimide ester, imidoester or polyflourophenyl ester, and wherein the azide is an alkyl azide or acyl azide;
• L′ is, at each occurrence, independently a linker comprising a covalent bond to Q, a targeting moiety, a linker comprising a covalent bond to a targeting moiety, a linker comprising a covalent bond to a solid support or solid support residue, a linker comprising a covalent bond to a solid support or solid support residue or a linker comprising a covalent bond to a further compound of structure (II);
• m is, at each occurrence, independently an integer of zero or greater;
• and
• n is an integer of one or greater.