Disaccharide linker, disaccharide-small molecule drug conjugate and sugar chain fixed-point antibody-drug conjugate, and preparation method therefor and use thereof

A disaccharide linker, which is represented by the following general formula I or general formula II:

• In general formula I,
• G ring represents a structure derived from a monosaccharide molecule, which is connected to the 4-position of N-acetyl-D-glucosamine ring closed in 1,2 positions through a glycosidic bond, wherein the monosaccharide molecule is selected from the group consisting of galactose, N-acetyl-galactose, glucose, mannose, fucose, sialic acid sugar;
• the glycosidic bond is 1,4-glycosidic bond, 2,4-glycosidic bond or 3,4-glycosidic bond;
• Z-Y-X- represents a substituent on the G ring, and the substitution position of Z-Y-X- is any position other than position 1 of the G ring derived from the monosaccharide molecule,
• Wherein, in the structure Z-Y-X-, Z-Y- may or may not exist,
• When Z-Y- does not exist, X is an aldehyde group, a phosphoric acid group, —NH2, —CH2—NH2, —COOH, —CH2SRp, —CH2SeRp, —N3, —CH2—N3, wherein Rp is a protecting group;
• When Z-Y- exists, X is selected from the group consisting of —CH2—, —CH2—O—, —CH2—S—, —CH2—Se—, —CO—NH—, —ON═CH—, —CONH—N═CH—, —NHCH2—, —CH═CH—, and the following structures:
• Y is a divalent linker or a multivalent linker connecting X and Z,
• preferably, Y is selected from the following groups:
• —(CH2)m—(CH-w)n-, —(CH2—CH2—O)m—(CH-w)n-, —(PO4)n—, wherein m and n are independently selected from an integer between 0-30, w is a hydrogen atom or a polyethylene glycol structure with different lengths;
• or a combination of cleavable fragments and the above-mentioned linking fragments;
• Z is selected from the following cases i)-iv):
• i) reactive groups with bioorthogonal reactivity or fragments of functional molecules,
• Preferably, Z is selected from the following reactive groups:
• azide residues, aldehyde residues, thiol residues, alkyne residues, alkene residues, halogen residues, tetrazine residues, nitrone residues, hydroxylamine residues, nitrile residues, hydrazine residues, ketone residues, boronic acid residues, cyanobenzothiazole residues, allyl residues, phosphine residues, maleimide residues, disulfide residues, thioester residues, α-halogenated carbonyl residues, isonitrile residues, sydnones residues, selenium residues, conjugated diene residues, phosphoric acid residues, cycloalkyne residues and cycloalkene residues,
• Alternatively, Z is selected from the following groups:
• Wherein, n is an integer of 1-30, R1 and R2 are independently selected from H, —CH3, —CH2CH3, cyclopropyl or cyclobutyl;
• Preferably, the functional molecules are selected from:
• toxins, drugs, fluorescent probes, polyethylene glycol, lipids, polypeptides, nanobodies, DNA and related drugs, RNA and related drugs, cholesterol, antibiotics or radioisotope labels, contrast agents and MRI agents;
• ii)
• Wherein, L1 is a trivalent linker with three reactive groups,
• Preferably, L1 is a branched-chain amino acid with reactive functional groups which is derived from lysine, aspartic acid, glutamic acid, propargylglycine, cysteine, and the following structures:
• Wherein, n is an integer of 1-30,
• L2 and L3 are divalent or multivalent linkers connecting L1 with Z2 and Z3,
• Preferably, L2 and L3 are independently selected from the following structures:
• —(CH2)m—(CH-w)n-, —(CH2—CH2—O)m—(CH-w)n-, —(PO4)n—, wherein m and n are independently selected from integers between 0-30, w is a hydrogen atom or other side chain structures, such as polyethylene glycol with different lengths;
• or a combination of cleavable fragments and the above-mentioned linking fragments,
• Z′ is a linking fragment coupling L1 to the sugar linker, independently is absent or —(CH2)p—, wherein p is an integer from 1 to 5, or is a group that can react with the Z group in case i),
• For example, Z′ is selected from the following groups:
• Wherein, R1 and R2 are each independently selected from H, —CH3, —CH2CH3, cyclopropyl or cyclobutyl;
• The definitions of Z2 and Z3 are the same as the definitions of Z in case i);
• iii)
• Wherein, L6 is a tetravalent linker with four reactive groups,
• Preferably, L6 is selected from dimerized lysine, dimerized glutamic acid, dimerized aspartic acid, aspartic acid-glutamic acid dipeptide structure, aspartic acid-lysine dipeptide structure, glutamate-lysine structure, or is a structure selected from the following:
• Wherein, n is an integer of 1-30, the definitions of L2, L3, L4 are the same as the definitions of L2, L3 in ii), the definition of Z′ is the same as the definition of Z′ in ii), and the definitions of Z2, Z3, Z4 are the same as the definitions of Z2 and Z3 in ii);
• iv)
• wherein, the definition of L1 is the same as the definition of L1 in ii), the definitions of L2, L3, L4, L5 are the same as the definitions of L2, L3 in ii), the definitions of Z′ is the same as the definition of Z′ in ii), and the definitions of Z2, Z3, Z4, Z5 are the same as the definitions of Z2 and Z3 in ii);
• Or, when Y, Z are absent, X is selected from:
• Wherein, R1 is hydroxyl —OH or azido —N3, R2 is any group, R3 is hydroxyl —OH or any group containing —NH—, R4 is any group, represents the connection position,
• In the above general formula II, X, Y and Z are each as defined as those in formula I.