The present invention provides new salts and crystalline forms of leukadherin LA1 [(Z)-4-(5-((3-benzyl-4-oxo-2-thioxothiazolidin-5-ylidene)methyl)furan-2-yl)benzoic acid] according to Formula I. Methods for preparation of the salts and crystalline forms are also described, as well as methods for treating β2 integrin-mediated diseases and conditions using the salts and crystalline forms.