The present invention relates to crystalline forms and co-crystals of (2R,5S,13aR)-8-hydroxy-7,9-dioxo-N-(2,4,6-triofluorobenzyl)-2,3,4,5,7,9,13,13a-octahydro-2,5-methanopyrido[1',2':4,5]pyrazíno[2,1-b][1,3]oxazepine-10-carboxamide, the pharmaceutical formulations, and the therapeutic uses thereof. The present invention also relates to novel crystalline forms of sodium (2R,5S,13aR)-7,9-dioxo-10-((2,4,6-trifluorobenzyl)carbamoyl)-2,3,4,5,7,9,13,13a-octahydro-2,5-methanopyrido[1',2':4,5]pyrazino[2,1-b][1,3]oxazepin-8-olate Form I.