(S)-Hydroxychloroquine ((S)-HCQ) sulfate is an isomer of Hydroxychloroquine. (S)-Hydroxychloroquine sulfate (2.5-20 mg/mL) reduces the rate of insulin degradation in liver homogenates isolated from non-diabetic and diabetic rats. Formulations containing Hydroxychloroquine have been used in the study of malaria, rheumatoid arthritis, and systemic lupus erythematosus.