5-[[[[2-[[(4S)-4-[[4-[[(2-Amino-1,4-dihydro-4-oxo-6-pteridinyl)methyl]amino]benzoyl]amino]-4-carboxy-1-oxobutyl]amino]ethyl]amino]thioxomethyl]amino]-2-(6-hydroxy-3-oxo-3H-xanthen-9-yl)benzoic acid sodium salt