Derivatives of 4-mercaptopyrrolidine as inhibitors of farnesil transferase

Pharmaceutical compositions comprising an inhibitor 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 -CO-NH2- 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 an enantiomer, diastereoisomer, pharmaceutically acceptable salt, prodrug or solvate thereof together with a pharmaceutically acceptable diluent or carrier. A particular use is cancer therapy.