The present invention relates to a compound and composition for use in the stimulation of IL-12 production and IFN-γ production, which compound is selected from: tert-butyl N-[2-{4-[6-amino-5-(2,4-difluorobenzoyl)-2-oxopyridin-1(2H)-yl]-3,5- difluorophenyl}ethyl)-L-alaninate, or a pharmaceutically acceptable salt, hydrate or solvate thereof; and N-[2-{4-[6-amino-5-(2,4-difluorobenzoyl)-2-oxopyridin-1(2H)-yl]-3,5- difluorophenyl}ethyl)-L-alanine.