The hydrochloride salt of a liposomal small-molecule glutathione analog inhibitor of glutathione S-transferase (GST) P1-1 with hematopoiesis-stimulating activity. After intracellular de-esterification, the active form of ezatiostat binds to and inhibits GST P1-1, thereby restoring Jun kinase and MAPK pathway activities and promoting MAPK-mediated cellular proliferation and differentiation pathways. This agent promotes the proliferation and maturation of hematopoietic precursor cells, granulocytes, monocytes, erythrocytes and platelets.