This Phase 1-2a study is an open label, dose-ranging study of TLK199 Tablets in patients with all World Health Organization or French-American-British classification types of myelodysplastic syndrome (MDS). In Phase 1, the safety, pharmacokinetics, and hematologic response rate with TLK199 Tablets will be evaluated. The Phase 1 dose-ranging stage is designed to determine the maximum tolerated dose or optimal biologic dose of TLK199 Tablets. Evaluation of the pharmacokinetics of TLK199 Tablets will be conducted. In Phase 1, an additional 12 patients will undergo pharmacokinetic evaluation under fed conditions at the selected Phase 2a dose. In Phase 2a, further safety and hematologic responses by the modified International Working Group MDS response criteria will be studied.
