Farnesyltransferase inhibitors and their potential role in therapy for myelodysplastic syndromes and acute myeloid leukaemia

Novel strategies are required for treatment of acute myeloid leukaemia (AML) and higher risk myelodysplastic syndrome (MDS) patients who are not eligible for intensive chemotherapy and/or allogenic stem cell transplantation. As activating RAS mutations are frequent in these diseases, one novel approach, consisting of interfering with isoprenylation of RAS proteins by farnesyltransferase inhibitors (FTIs), has been proposed. Clinical phase II studies with the oral FTIs tipifarnib and lonafarnib in previously untreated AML, MDS and chronic myelomonocytic leukaemia yielded rather encouraging results while results in relapsed and/or refractory AML were disappointing. Results of a phase III trial in untreated AML in the elderly with tipifarnib were also disappointing. Clinical responses were not related to RAS mutations, suggesting additional actions of FTIs on other molecular targets. The combination of existing FTIs with other treatments, such as chemotherapy (in AML) and hypomethylating agents (in MDS and AML), is under investigation. Ongoing studies will also determine if gene profiling analysis may help to identify patients that will respond to FTIs.