osi-7904 osi-7904 osi-7904 is a noncompetitive liposomal thymidylate synthase inhibitor. osi-7904 is a benzoquinazoline folate analog with antineoplastic activity. as a thymidylate synthase inhibitor, osi-7904 noncompetitively binds to thymidylate synthase, resulting in inhibition of thymine nucleotide synthesis and dna replication. osi-7904legal statuslegal status investigational identifiers iupac name (2s)-2-quinazolin-9-yl)methylamino]-3-oxo-1h-isoindol-2-yl]pentanedioic acid cas number139987-54-5pubchem cid135403832uniion177zce7mcomptox dashboard (epa)dtxsid70930683 chemical and physical dataformulac27h24n4o6molar mass500.511 g·mol−13d model (jsmol)interactive image smiles cc1=nc2=c(c3=c(c=cc(=c3)cnc4=cc5=c(c=c4)c(=o)n(c5)(ccc(=o)o)c(=o)o)c=c2)c(=o)n1 osi-7904l is a liposome-encapsulated formulation of osi-7904. liposome encapsulation improves the efficacy and increases the half-life of osi-7904. its effect on solid tumors is currently under evaluation.