The present invention relats to inhibitors of ras farnesylation of Formula (I) wherein: R1 is for example H and further values as defined in the specification; R2 is for example H and further values as defined in the specification; R3 is for example H or a substituent having values as defined in the specification; p is 0-3 in which R3 values can be the same or different; L is a linking moiety for example —CH2—NH— and further values as defined in the specification; A is selected from phenyl; naphthyl; a 5-10 membered monocyclic or bicyclic heteroaryl ring containing up to 5 heteroatoms where the heteroatoms are independently selected from O, N and S; or a —S—S— dimer thereof when R2=H; or a N-oxide or a pharmaceutically-acceptable salt, prodrug or solvate thereof. Processes for their preparation, their use as therapeutic agents and pharmaceutical compositions containing them. A particular use is in cancer therapy.