Described herein are salts (e.g., fumarates) of 3-(2, 5-difluorophenyl)-7-[1, 1-bis (methyl-d3) ethyl-2, 2, 2-d3]-6-[(1-methyl-1H-1, 2, 4-triazol-5-yl) methoxy]-1, 2, 4-triazolo [4, 3-b]
pyridazine and salts (e.g., fumarates) of 3-(2, 5-difluorophenyl)-7-[1, 1-bis (methyl-d3) ethyl-2, 2, 2-d3]-6-[(1-methyl-1H-1, 2, 4-triazol-5-yl) methoxy]-1, 2, 4-triazolo [4, 3-b]
pyridazine and salts (e.g., fumarates) The present invention relates to particles of [1, 3-b]
pyridazine or a salt thereof and uses thereof.