Compounds of formula (I): wherein X is selected from CRX and N; RN1 is selected from H and C1-4
alkyl, which may be substituted by SH or halo; RG1 is selected from H and SH; RC2 is selected from H and optionally substituted C1-7
alkyl; RC3 is selected from H and optionally substituted C1-7
alkyl; Rx is selected from H, OH and NH2; RC4 is selected from: (i) an optionally substituted C3-12 N-containing heterocyclyl; (ii) C(═O)NRN5RN6, where RN5 and RN6 are independently selected from H, optionally substituted C1-7 alkyl, optionally substituted C3-20 heterocyclyl and optionally substituted C5-20
aryl or RN5 and RN6 and the
nitrogen atom to which they are attached form an optionally substituted N-containing C5-7 heterocyclyl group; (iii) C(═O)ORO1, where RO1 is selected from H, optionally substituted C1-7 alkyl, optionally substituted C3-20 heterocyclyl and optionally substituted C5-20
aryl; (iv) C(═O)NHNHSO2RS1, where RS1 is selected from H, optionally substituted C1-7 alkyl, optionally substituted C3-20 heterocyclyl and optionally substituted C5-20
aryl; (v) OC(═O)RC8, where RC8 is selected from H, optionally substituted C1-7 alkyl, optionally substituted C3-20 heterocyclyl and optionally substituted C5-20 aryl; (vi) OC(═O)NRN7RN8, where RN7 and RN8 are independently selected from H, optionally substituted C1-7 alkyl, optionally substituted C3-20 heterocyclyl and optionally substituted C5-20 aryl or RN7 and RN8 and the
nitrogen atom to which they are attached form an optionally substituted N-containing C5-7 heterocyclyl group; and (vii) C(═O)CH2NH C(═O)NHNH2, CHC(CN)2, CHC(CN)C(═O)NH2, and carboxy; RC5 is selected from H, OH and NH2; or RC4 and RC5 together with the carbon atoms to which they are bound form an optionally substituted aromatic ring containing either 5 or 6 ring atoms, of formula: where Q represents O, N, or CRQ1═CRQ2, where RQ1 and RQ2 are independently selected from H, OH and NH2; RC6 is selected from H, OH and NH2; and RC7 is selected from optionally substituted C3_12 N-containing heterocyclyl, NHC(═O)RC9, CH2NRN2RN3 and NHC(═S)NHRN4, where RC9 is selected from optionally substituted C1-7 alkyl, optionally substituted C3-20 heterocyclyl and optionally substituted C5-20 aryl, RN2 and RN3 are independently selected from H, optionally substituted C1-7 alkyl, optionally substituted C3-20 heterocyclyl and optionally substituted C5-20 aryl or RN2 and RN3 and the
nitrogen atom to which they are attached form an optionally substituted N-containing C5-7 heterocyclyl group, and RN4 is selected from optionally substituted C1-7 alkyl, optionally substituted C3-20 heterocyclyl and optionally substituted C5-20 aryl, and when RC4 and RC5 are not bound together, RC3 may additionally be selected from OR02, where RO2 is a C1-4 alkyl group, and C(═O)ORO3, where RO3 is a C1-4 alkyl group and RC2 may additionally be selected from halo, for use in stabilising a p53
protein carrying a Y220C
mutation.