Solid forms comprising (s)-2-(2,6-dioxopiperidin-3-yl)-4-((2-fluoro-4-((3-morpholinoazetidin-1-yl)methyl)benzyl)amino)isoindoline-1,3-dione and salts thereof, and compositions comprising and methods of using the same

A process for preparing a solid form of a hydrochloride salt of Compound 1:

• which is characterized by an XRPD pattern comprising peaks at 15.1, 16.3, and 20.7° 2θ±0.2° 2θ, and the process comprise slurrying Compound 1 free base and within 10% of 1 equivalent of hydrochloric acid in a solvent, wherein the solvent is acetone, acetonitrile, anisole, DCM, DMAc, EtOH, EtOAc, ethyl formate, isopropyl acetate, MeOH, MEK, MTBE, 2-MeTHF, nitromethane, NMP, 2-propanol, tetrahydrofuran, toluene, water, a mixture of acetone and water, a mixture of acetonitrile and water, a mixture of 2-PrOH and water, or a mixture of THF and water.