Catalysis of the reaction: 7,8-dihydroneopterin 3'-triphosphate = 6-pyruvoyl-5,6,7,8-tetrahydropterin + H+ + triphosphate.
2-amino-4-oxo-6--7,8-dihydroxypteridine triphosphate-lyase (6-pyruvoyl-5,6,7,8-tetrahydropterin-forming)