Compounds for nucleic acid cleavage

A bifunctional compound of formula (I) or a pharmaceutically acceptable salt or solvate thereof:

• wherein:
• C is a cleavage group as defined herein;
• L is a linker;
• and
• B is a non-covalent binding group
• with the proviso that C is not:
• (i) an imidazole (1,3-diazole) group that is optionally substituted with one, two or three (1-6C)alkyl groups, which may be the same or different;
• or
• (ii) a nucleic acid cleavage group of the formula Z:
• wherein:
• denotes the point of attachment to L;
• Ring A is absent or a nitrogen-containing heteroaryl or heterocyclic ring which is optionally further substituted with one or more substituent groups selected from halo, trifluoromethyl, trifluoromethoxy, cyano, hydroxyl, (1-4C)alkyl, (1-4C)haloalkyl, (1-4C)hydroxyalkyl, ORc, C(O)Rc, C(O)ORc, OC(O)Rc, C(O)N(Rd)Rc, N(Rd)C(O)Rc, S(O)yR, (wherein y is 0, 1 or 2), SO2N(Rd)Rc, N(Rd)SO2Rc, or NRcRd, wherein Rc and Rd are selected from hydrogen or (1-4C)alkyl;
• integer a1 is 0, 1, 2 or 3;
• Ra and Rb are each independently selected at each occurrence from hydrogen or (1-2C)alkyl;
• R1 and R2 are each independently selected from hydrogen, (1-6C)alkyl, heterocyclic ring, heterocycle-(1-3C)alkyl, heteroaryl, heteroaryl-(1-3C)alkyl, (3-6C)cycloalkyl, or (3-6C)cycloalkyl-(1-3C)alkyl, each of which is optionally substituted with one or more substituent groups selected from halo, trifluoromethyl, trifluoromethoxy, cyano, hydroxyl, ORe, C(O)Re, C(O)ORe, OC(O)Re, C(O)N(Rf)Re, N(Rf)C(O)Re, S(O)yRe (wherein y is 0, 1 or 2), SO2N(Rf)Re, N(Rf)SO2Re, or NReRf, wherein Re and Rf are selected from hydrogen or (1-4C)alkyl, or
• R1 and R2 are linked such that, together with the atoms to which they are attached, they form a 4-6 membered heterocycle or a 5- or 6-membered heteroaryl, wherein any 4-6 membered heterocycle or 5- or 6-membered heteroaryl is optionally substituted with one or more substituent groups selected from halo, trifluoromethyl, trifluoromethoxy, cyano, hydroxyl, (1-4C)alkyl, (1-4C)haloalkyl, (1-4C)hydroxyalkyl, ORg, C(O)Rg, C(O)ORg, OC(O)Rg, C(O)N(Rh)Rg, N(Rh)C(O)Rg, S(O)yRg (wherein y is 0, 1 or 2), SO2N(Rh)Rg, N(Rh)SO2Rg, or NRgRh, wherein Rg and Rh are selected from hydrogen or (1-4C)alkyl;
• wherein, when ring A is absent, R1 and R2 are each independently selected from hydrogen, heterocyclic ring, heterocycle-(1-3C)alkyl, heteroaryl, heteroaryl-(1-3C)alkyl, (3-6C)cycloalkyl, or (3-6C)cycloalkyl-(1-3C)alkyl, each of which is optionally substituted with one or more substituent groups selected from halo, trifluoromethyl, trifluoromethoxy, cyano, hydroxyl, ORe, C(O)Re, C(O)ORe, OC(O)Re, C(O)N(Rf)Re, N(Rf)C(O)Re, S(O)yRe (wherein y is 0, 1 or 2), SO2N(Rf)Re, N(Rf)SO2Re, or NReRf, wherein Re and Rf are selected from hydrogen or (1-4C)alkyl, provided that R1 and R2 are not both hydrogen.