An antibody active agent conjugate, wherein the antibody has an amino acid motif that can be recognized by an isoprenoid transferase, wherein the active agent is covalently linked to the antibody at the amino acid motif, wherein the amino acid motif is CAAX, XXCC, XCXC, or CXX, wherein C represents cysteine, A represents an aliphatic amino acid, and X represents an amino acid that determines a substrate specificity of the isoprenoid transferase; and wherein the amino acid motif is covalently linked to the active agent via at least one linker, wherein the at least one linker is an isoprenyl derivative that can be recognized by the isoprenoid transferase, whereby the linker is represented by the formula: wherein P 1 and Y are each independently a group containing a first functional group, the FG1 being selected from the group consisting of: acetylene, azide, aldehyde, hydroxylamine, hydrazine, ketone, nitrobenzofurazan, dansyl, fluorescein, biotin, and Rhodamin, L 1 is (CH 2) r X q (CH 2) p, X is oxygen, sulfur, -NR 1 -, -C NR 1 -, -NR 1 C -, -NR 1 SO 2 -, -SO 2 NR 1 -, -(CH=CH)-, or acetylene, R 1 is hydrogen, C 1-6 alkyl, C 1-6 alkyl aryl, or C 1-6 alkyl heteroaryl, r and p are each independently an integer of 0 to 6, q is an integer of 0 to 1, and n is an integer of 1 to 4, wherein the active agent is attached to a group containing a second functional group that can react with the FG1, wherein the FG2 is selected from the group consisting of: acetylene, hydroxylamine, azide, aldehyde, hydrazine, ketone, and wherein the active agent is attached to the group containing an FG2 via -(CH 2) r X q (CH 2) p - or [ZCH 2 CH 2 O(CH 2 CH 2 O) w CH 2 CH 2 Z]-, in which X is oxygen, sulfur, -NR 1 -, -C NR 1 -, -NR 1 C -, -NR 1 SO 2, or -SO 2 NR 1 -, Z is oxygen, sulfur or NR 1, R 1 is hydrogen, C 1-6 alkyl, C 1-6 alkyl aryl, or C 1-6 alkyl heteroaryl, r and p are each independently an integer of 0 to 6, q is an integer of 0 to 1, and w is an integer of 0 to 6, wherein the -(CH 2) r X q (CH 2) p - or -[ZCH 2 CH 2 O(CH 2 CH 2 O) w CH 2 CH 2 Z]- is attached to (i) a peptide(s) that can be cleaved by cathepsin B or (ii) a glucuronide that can be cleaved by β-glucuronidase, wherein the peptide that can be cleaved by cathepsin B is and the glucuronide that can be cleaved by β-glucuronidase is and wherein the antibody is a monoclonal antibody, a target binding antibody fragment, a single chain Fv (scFv) mutant, a multispecific antibody, a bispecific antibody generated from at least two intact antibodies, a chimeric antibody, a humanized antibody, or a human antibody, or a fusion protein comprising a target binding antibody fragment. P 1 and Y are each independently a group containing a first functional group, the FG1 being selected from the group consisting of: acetylene, azide, aldehyde, hydroxylamine, hydrazine, ketone, nitrobenzofurazan, dansyl, fluorescein, biotin, and Rhodamin, L 1 is (CH 2) r X q (CH 2) p, X is oxygen, sulfur, -NR 1 -, -C NR 1 -, -NR 1 C -, -NR 1 SO 2 -, -SO 2 NR 1 -, -(CH=CH)-, or acetylene, R 1 is hydrogen, C 1-6 alkyl, C 1-6 alkyl aryl, or C 1-6 alkyl heteroaryl, r and p are each independently an integer of 0 to 6, q is an integer of 0 to 1, and n is an integer of 1 to 4, wherein the active agent is attached to a group containing a second functional group that can react with the FG1, wherein the FG2 is selected from the group consisting of: acetylene, hydroxylamine, azide, aldehyde, hydrazine, ketone, and wherein the active agent is attached to the group containing an FG2 via -(CH 2) r X q (CH 2) p - or [ZCH 2 CH 2 O(CH 2 CH 2 O) w CH 2 CH 2 Z]-, in which X is oxygen, sulfur, -NR 1 -, -C NR 1 -, -NR 1 C -, -NR 1 SO 2, or -SO 2 NR 1 -, Z is oxygen, sulfur or NR 1, R 1 is hydrogen, C 1-6 alkyl, C 1-6 alkyl aryl, or C 1-6 alkyl heteroaryl, r and p are each independently an integer of 0 to 6, q is an integer of 0 to 1, and w is an integer of 0 to 6, wherein the -(CH 2) r X q (CH 2) p - or -[ZCH 2 CH 2 O(CH 2 CH 2 O) w CH 2 CH 2 Z]- is attached to (i) a peptide(s) that can be cleaved by cathepsin B or (ii) a glucuronide that can be cleaved by β-glucuronidase, wherein the peptide that can be cleaved by cathepsin B is and the glucuronide that can be cleaved by β-glucuronidase is and wherein the antibody is a monoclonal antibody, a target binding antibody fragment, a single chain Fv (scFv) mutant, a multispecific antibody, a bispecific antibody generated from at least two intact antibodies, a chimeric antibody, a humanized antibody, or a human antibody, or a fusion protein comprising a target binding antibody fragment.