LY 254155, an antifolate, inhibits hGARFT and binds to mFBP with K_is of 2.1±0.2 and 1.7±0.1 nM, respectively. IC50 & Target: Ki: 2.1±0.2 (hGARFT ), 1.7± 0.1 nM (mFBP)^[1] In Vitro: LY 254155 inhibits recombinant human monofunctional glycinamide ribonucleotide formyltransferase (hGARFT) and binds to membrane folate-binding protein (mFBP) ^[1]. In Vivo: LY 254155 is active against a broad panel of murine and human xenograft solid tumors. LY 254155 (5, 10, 20, and 40 mg/kg) inhibits murine C3H carcinoma growth in C3H mice, with % inhibition of tumor growth is 49%, 71%, 90%, and 94%, respectively^[1].