Leukotriene B4 (LTB4) inhibits lymphangiogenesis in the mouse tail model of lymphedema and is elevated in tissue in patients with lymphedema. Ubenimex is an inhibitor of leukotriene A4 hydrolase (LTA4H), the biosynthetic enzyme for LTB4. This proof-of-concept study is designed as a randomized, double-blind, placebo-controlled study comparing ubenimex at 150 mg, 3 times daily (total daily dose of 450 mg) with placebo for 6 months treatment period in patients with leg lymphedema. The primary objectives for the study are: