Two new stable non stoichiomeric crystalline solvate forms of Eluxadoline with 4-methylpentan-2-one or methyl tert-butylether are described as well as the process for the production of the same. The solvate form with 4-methylpentan-2-one is defined as "Eluxadoline form gamma" whereas the solvate with methyl tertbutylether is defined as "Eluxadoline form delta". Form gamma may be obtained by slurrying Eluxadoline amorphous form in 4-methylpentan-2-one； form delta may be obtained by slurrying Eluxadoline form gamma in methyl tert-butylether.
