| CPC A61K 47/6869 (2017.08) [A61K 31/427 (2013.01); A61K 31/5517 (2013.01); A61K 31/661 (2013.01); A61K 47/6803 (2017.08); A61P 35/00 (2018.01)] | 17 Claims |

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1. A conjugate having the chemical structure:
Ab-(L1-D)p,
wherein,
D is a CIDE having the structure;
E3LB-L2-PB,
wherein:
E3LB is covalently bound to L1 and L2, having the structure of
![]() wherein
indicates the attachment point to L2 and indicates the attachment point to L1;L2 is a linker covalently bound to E3LB and PB;
PB is a protein binding group covalently bound to L2 and the PB binds BRD4 or Estrogen Receptor alpha (ERα), or variants, mutations, splice variants, indels or fusions thereof;
Ab is an antibody covalently bound to L1;
L1 is a linker covalently bound to the Ab and the E3LB, wherein L1 has the formula selected from the group consisting of:
![]() wherein, R1 and R2 are independently selected from H and C1-C6 alkyl, or R1 and R2 together with the carbon to which each is attached form a 3, 4, 5, or 6-membered cycloalkyl or heterocyclyl group; R14a is H, haloalkyl, optionally substituted alkyl, methyl, fluoromethyl, hydroxymethyl, ethyl, isopropyl, or cyclopropyl; R15 is optionally substituted heteroaryl or optionally substituted aryl; and R is H, ethyl, isopropyl, tert-butyl, sec-butyl, cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl; optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted hydroxyalkyl, optionally substituted heteroaryl, or haloalkyl; and
p has a value of from 1 to 8.
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