Carboline and betacarboline derivatives for use as hdac enzyme inhibitors

A compound of formula (IA) or (1B), or a salt, hydrate or solvate thereof

• wherein fused rings A1 and A2 are optionally substituted;
• R1 represents a radical of formula -(Alk1)n-(X)m-(Alk2)p-Z wherein
• Z represents a radical of formula —C(═O)NH(OH), or —N(OH)C(═O)Y wherein Y represents hydrogen, C1-C6 alkyl, a phenyl or cycloalkyl ring, or a monocyclic heterocyclic radical having 5 or 6 ring atoms;
• Alk1 represents an optionally substituted, straight or branched, C1-C6 alkylene radical,
• Alk2 represents an optionally substituted, straight or branched, C1-C6 alkylene, C2-C6 alkenylene or C2-C6 alkynylene radical which may optionally contain an ether (—O—), thioether (—S—) or amino (—NRA—) link wherein RA is hydrogen or C1-C3 alkyl;
• X represents an optionally substituted phenyl or 5- or 6-membered heteroaryl ring;
• and
• n, m and p are independently 0 or 1, provided that at least one of n, m and p is 1 and the length of radical -(Alk1)n-(X)m-(Alk2)p- is equivalent to that of a hydrocarbon chain of from 2-10 carbon atoms;
• R12 is hydrogen and R2 is (a) an optional substituent or (b) a radical of formula -(Alk3)r-Q wherein r is 0 or 1, Alk3 represents an optionally substituted, straight or branched, C1-C6 alkylene, C2-C6 alkenylene or C2-C6 alkynylene radical and Q is hydrogen or an optionally substituted carbocyclic or heterocyclic group;
• or R12 and R2 taken together with the carbon atoms to which they are attached form an optionally substituted carbocyclic or heterocyclic ring;
• R13 is hydrogen and R3 is (i) an optional substituent or (ii) a radical of formula -(Alk3)r-Q wherein r is 0 or 1, Alk3 represents an optionally substituted, straight or branched, C1-C6 alkylene, C2-C6 alkenylene or C2-C6 alkynylene radical and Q is hydrogen or an optionally substituted carbocyclic or heterocyclic group;
• or R13 and R3 taken together with the carbon atoms to which they are attached form an optionally substituted carbocyclic or heterocyclic ring;
• and
• R4 is hydrogen or C1-C6 alkyl.