Hydrogels with biodegradable crosslinking

1. A method to prepare a drug-releasing degradable hydrogel, which method comprises:

(a) providing a first multi-armed polyethylene glycol (PEG) polymer wherein each arm is terminated by a group comprising orthogonal first and second functional groups, which first orthogonal functional group is different from said second orthogonal functional group, and wherein the group comprising said first orthogonal functional group and said second orthogonal functional group comprises cysteine, lysine, or aspartate;

(b) reacting said first multi-armed PEG polymer of step (a) with a linker-drug conjugate wherein said conjugate comprises a third functional group that reacts with only the first orthogonal functional group to obtain a derivatized first polymer; and

(c) reacting the derivatized first polymer obtained in step (b) with a crosslinker coupled to a second multi-armed PEG polymer wherein said crosslinker comprises a fourth functional group that reacts with only the second orthogonal functional group present on said derivatized first polymer to obtain said drug-releasing degradable hydrogel, or

(d) reacting said first multi-armed PEG polymer of step (a) with a crosslinker coupled to a second multi-armed PEG polymer wherein said crosslinker comprises a fourth functional group that reacts only with the second orthogonal functional group of said first multi-armed PEG polymer to obtain a crosslinked polymer, and

(e) reacting the crosslinked polymer of step (d) with a linker-drug conjugate, wherein said conjugate comprises a third functional group that reacts with only the first orthogonal functional group of said first multi-armed PEG polymer to obtain a said drug-releasing degradable hydrogel,

wherein the crosslinker of step (c) or step (d) is of formula (1)

wherein

m of formula (1) is 0 or 1;

X of formula (1) is

wherein

T* is O, S, or NR 6 ;

z is 1-6;

Y is (OCH 2 CH 2 ) p , wherein p is 1-100; and

Z 2 is a functional group coupled to the second multi-armed PEG polymer, and one of R 1 , R 2 and R 5 of formula (1) comprises the fourth functional group that reacts with only the second orthogonal functional group present on said first multi-armed PEG polymer of step (a) or said derivatized first multi-armed PEG polymer of step (b);

or

Z 2 is the fourth functional group that reacts with only the second orthogonal functional group present on said first multi-armed PEG polymer of step (a) or said derivatized first multi-armed PEG polymer of step (b), and one of R 1 , R 2 and R 5 of formula (1) comprises a functional group coupled to the second multi-armed PEG polymer;

with the proviso that:

(1) when one of R 5 of formula (1) comprises the fourth functional group or the functional group coupled to the second multi-armed PEG polymer, the remaining R 5 of formula (1) is H, optionally substituted alkyl, optionally substituted alkenylalkyl, optionally substituted alkynylalkyl, (OCH 2 CH 2 ) p O-alkyl wherein p=1-1000, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted heteroaryl, or optionally substituted heteroarylalkyl; and

(a) R 1 and R 2 of formula (1) are independently CN, NO 2 , optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkenyl, optionally substituted alkynyl, COR 3 , SOR 3 , SO 2 R 3 , or SR 4 ;

(b) R 1 and R 2 of formula (1) may be joined to form a 3-8 membered ring;

(c) R 1 of formula (1) is CN, NO 2 , optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkenyl, optionally substituted alkynyl, COR 3 , SOR 3 , SO 2 R 3 , or SR 4 ; and R 2 of formula (1) is H, optionally substituted alkyl, optionally substituted arylalkyl, or optionally substituted heteroarylalkyl; or

(d) R 2 of formula (1) is CN, NO 2 , optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkenyl, optionally substituted alkynyl, COR 3 , SOR 3 , SO 2 R 3 , or SR 4 ; and R 1 of formula (1) is H, optionally substituted alkyl, optionally substituted arylalkyl, or optionally substituted heteroarylalkyl; or

(2) when R 1 of formula (1) comprises the fourth functional group or the functional group coupled to the second multi-armed PEG polymer: R 2 of formula (1) is CN, NO 2 , optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkenyl, optionally substituted alkynyl, COR 3 , SOR 3 , SO 2 R 3 , or SR 4 ; and each R 1 of formula (1) is independently H, optionally substituted alkyl, optionally substituted alkenylalkyl, optionally substituted alkynylalkyl, (OCH 2 CH 2 ) p O-alkyl wherein p=1-1000, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted heteroaryl, or optionally substituted heteroarylalkyl; or

(3) when R 1 of formula (1) comprises the fourth functional group or the functional group coupled to the second multi-armed PEG polymer: R 1 of formula (1) is CN, NO 2 , optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkenyl, optionally substituted alkynyl, COR 3 , SOR 3 , SO 2 R 3 , or SR 4 ; and each R 5 of formula (1) is independently H, optionally substituted alkyl, optionally substituted alkenylalkyl, optionally substituted alkynylalkyl, (OCH 2 CH 2 ) p O-alkyl wherein p=1-1000, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted heteroaryl, or optionally substituted heteroarylalkyl;

wherein the linker-drug conjugate of step (b) or step (e) is of formula (3)

wherein

m of formula (3) is 0 or 1;

D of formula (3) is a drug;

Y of formula (3) is NH or NBCH 2 , wherein B is H, optionally substituted alkyl, optionally substituted arylalkyl, optionally substituted heteroaryl, or optionally substituted heteroarylalkyl;

either R 1 , R 2 or one of R 5 of formula (3) comprises the third functional group coupled to the first orthogonal functional group of the first multi-armed PEG polymer;

with the proviso that:

(1) when one of R 5 of formula (3) comprises the third functional group, the remaining R 5 of formula (3) is H, optionally substituted alkyl, optionally substituted alkenylalkyl, optionally substituted alkynylalkyl, (OCH 2 CH 2 ) p O-alkyl wherein p=1-1000, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted heteroaryl, or optionally substituted heteroarylalkyl; and

(a) R 1 and R 2 of formula (3) are independently CN, NO 2 , optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkenyl, optionally substituted alkynyl, COR 3 , SOR 3 , SO 2 R 3 , or SR 4 ;

(b) R 1 and R 2 of formula (3) may be joined to form a 3-8 membered ring;

(c) R 1 of formula (3) is CN, NO 2 , optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkenyl, optionally substituted alkynyl, COR 3 , SOR 3 , SO 2 R 3 , or SR 4 ; and R 2 of formula (3) is H, optionally substituted alkyl, optionally substituted arylalkyl, or optionally substituted heteroarylalkyl; or

(d) R 2 of formula (3) is CN, NO 2 , optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkenyl, optionally substituted alkynyl, COR 3 , SOR 3 , SO 2 R 3 , or SR 4 ; and R 1 of formula (3) is H, optionally substituted alkyl, optionally substituted arylalkyl, or optionally substituted heteroarylalkyl; or

(2) when R 1 of formula (3) comprises the third functional group: R 2 of formula (3) is CN, NO 2 , optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkenyl, optionally substituted alkynyl, COR 3 , SOR 3 , SO 2 R 3 , or SR 4 ; and each R 5 of formula (3) is independently H, optionally substituted alkyl, optionally substituted alkenylalkyl, optionally substituted alkynylalkyl, (OCH 2 CH 2 ) p O-alkyl wherein p=1-1000, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted heteroaryl, or optionally substituted heteroarylalkyl; or

(3) when R 2 of formula (3) comprises the third functional group: R 1 of formula 3) is CN, NO 2 , optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkenyl, optionally substituted alkynyl, COR 3 , SOR 3 , SO 2 R 3 , or SR 4 ; and each R 5 of formula (3) is independently H, optionally substituted alkyl, optionally substituted alkenylalkyl, optionally substituted alkynylalkyl, (OCH 2 CH 2 ) p O-alkyl wherein p=1-1000, optionally substituted aryl, optionally substituted arylalkyl, optionally substituted heteroaryl, or optionally substituted heteroarylalkyl,

wherein each said orthogonal functional group independently comprises N 3 , NH 2 , NH-CO 2 t Bu, SH, S t Bu, maleimide, CO 2 H, CO 2 t Bu, 1,3-diene, cyclopentadiene, furan, alkyne, cyclooctyne, acrylate, or acrylamide, and wherein

when one orthogonal functional group comprises N 3 the other does not comprise alkyne or cyclooctyne,

when one orthogonal functional group comprises SH the other does not comprise maleimide, acrylate, or acrylamide, when one orthogonal functional group comprises NH 2 the other does not comprise CO 2 H,

when one orthogonal functional group comprises 1,3-diene or cyclopentadiene the other does not comprise furan.

2. The method of claim 1 , wherein the linker-drug conjugate is degradable by a beta elimination reaction.

3. The method of claim 1 , wherein the crosslinker is degradable by a beta elimination reaction.

4. The method of claim 1 , wherein in Formula (1)

R 2 is H; and/or

one of R 5 is H and the other is (CH 2 ) n Z wherein n is 1-6 and Z is said fourth functional group.

5. The method of claim 1 , wherein the first and/or second multi-armed PEG polymer comprises the formula [—(CH 2 ) s (CH 2 CH 2 O) n ] t Q, wherein

n is 10-1000;

s is 0-2;

t is 2, 4, 8, 16 or 32 and represents the number of arms of said polymer; and

Q is a core group having a valency t.

6. The method of claim 5 , wherein t is 4.

7. The method of claim 5 , wherein Q is pentaerythritol, tripentaerythritol, or hexaglycerin.