Suplatast is a novel immunomodulator that can adjust the imbalance in the Th1/Th2 immune response and shows clear clinical efficacy against bronchial asthma (BA). Suplatast tosilate helps to suppress the production of IgE, to block the production of cytokines and to suppress allergy-related eosinophils. Clinical studies on the efficacy of Suplatast were carried out in Japan. Suplatast showed adequate efficacy for the treatment of BA, allergic rhinitis and atopic dermatitis. Suplatast is now available for the management of BA as a controller of the Th2-dependent allergic inflammation. Suplatast tosilate is not approved in the United States, but is available in Japan as Tosilart® and IPD Capsules®. IPD-1151T (suplatast tosilate) was originated by Taiho and is being developed for the treatment of interstitial cystitis and chronic non-bacterial prostatitis as additional indications. IPD-1151T treatment for 1 year resulted in a significantly increased bladder capacity and decreased symptoms, such as urinary urgency, frequency and lower abdominal pain, in patients with nonulcerative interstitial cystitis.