The discovery of novel uracil phenylethylamines bearing a butyric acid as potent human gonadotropin-releasing hormone receptor (h GnRH-R) antagonists is described. A major focus of this optimization was to improve the CYP3A4 inhibition liability of these uracils while maintaining their GnRH-R potency. R-4-{2-[5-(2-Fluoro-3-methoxyphenyl)-3-(2-fluoro-6- [trifluoromethyl] benzyl)-4-methyl-2, 6-dioxo-3, 6-dihydro-2 H-pyrimidin-1-yl]-1- ...