or a pharmaceutically acceptable salt thereof, wherein

COMP is a residue of the anti-ROR1 antibody comprising one or more non-natural amino acids;

L¹ is —C_1-6 alkylene-;

Y is —X¹—C_1-6 alkylene-[X¹—C_1-6 alkylene]_n-[X¹]_p—, —X¹—C_2-6 alkenylene-[X¹—C_2-6 alkenylene]_n-[X¹]_p—, —X¹—C_2-6 alkynylene-[X¹—C_2-6 alkynylene]_n-[X¹]_p—, wherein at least one alkylene, alkenylene or alkynylene in Y is substituted with one or more substituents selected from R⁵⁰; and

wherein the alkylene, alkenylene, or alkynylene in Y is optionally substituted with one or more substituents selected from R⁵¹;

R⁵⁰ is —C_1-6 alkylene-X²—[C_1-6 alkylene]_m-POLY, —C_2-6 alkenylene-X²—[C_2-6 alkenylene]_m-POLY, or —C_2-6 alkynylene-X²—[C_2-6 alkynylene]_m-POLY, wherein each alkylene, alkenylene or alkynylene of R⁵⁰ is optionally substituted with one or more substituents selected from halogen, —CN, —NO₂, —OH, —N(R¹⁰)₂, —C(O)N(R¹⁰)₂, —C(O)—, —C(S)—, —C(O)OCH₂C₆H₅, —NHC(O)OCH₂C₆H₅, C_1-10 alkyl, C_2-10 alkenyl, C_2-10 alkynyl, C_3-12 carbocycle, 3- to 12-membered heterocycle, and C_1-10 haloalkyl;

R⁵¹ is independently selected from halogen, —CN, —NO₂, —OH, —N(R¹⁰)₂, —C(O)N(R¹⁰)₂, —C(O)—, —C(S)—, —C(O)OCH₂C₆H₅, —NHC(O)OCH₂C₆H₅, C_1-10 alkyl, C_2-10 alkenyl, C_2-10 alkynyl, C_3-12 carbocycle, 3- to 12-membered heterocycle, and C_1-10 haloalkyl;

X¹ and X² are independently selected from —C(O)— and —N(R¹⁰)C(O)—;

R¹⁰ is independently selected at each occurrence from hydrogen, C_1-10 alkyl, C_2-10 alkenyl, C_2-10 alkynyl, C_3-12 carbocycle, 3- to 12-membered heterocycle, and C_1-10 haloalkyl;

POLY is a water-soluble polymer;

n is an integer selected from zero, one, two, and three;

m is an integer selected from zero and one;

p is an integer selected from zero and one;

Su is a hexose form of a monosaccharide;

D is a drug moiety; and

RL is a reactive group residue.