<qa>  What is the name of the drug that blocks proteins that make cancer cells grow?The purpose of this study is to characterize the hematological response rate, as well as other parameters of efficacy and safety induced by tipifarnib in patients with high-risk myelodysplastic syndrome MDS. Tipifarnib belongs to a class of drugs called Farnesyl Transferase Inhibitors FTI. It blocks proteins that make cancer cells grow. 