 As a thymidylate synthase inhibitor, OSI-7904 noncompetitively binds to thymidylate synthase, resulting in inhibition of thymine nucleotide synthesis and DNA replication.OSI-7904L is a liposome-encapsulated formulation of OSI-7904.Liposome encapsulation improves the efficacy and increases the half-life of OSI-7904.