SR1555 hydrochloride is the hydrochloride salt form of SR1555. SR1555 hydrochloride is an inverse agonist for retinoic acid receptor-related orphan nuclear receptor γ ( RORγ ) with an IC 50 of 1 μM. SR1555 hydrochloride inhibits the development and function of pro-inflammatory TH17 cell, increases the frequency of anti-inflammatory T regulatory (Treg) cells. SR1555 hydrochloride can be used for research about autoimmune diseases.