FK506 Phase 3 Study: a Study for Steroid Non-resistant Myasthenia Gravis (MG) Patients

Inclusion Criteria: * Clinically diagnosed as myasthenia gravis * Those whose MG symptoms are well-controlled by the treatment with prednisone * Steroid non-refractory Myasthenia Gravis: ≧20mg and ≦40mg / alternate day of steroid dose required to maintain Exclusion Criteria: * Those who have thymoma or the history of thymoma (Masaoka stage III or IV) * Patients who received steroid pulse therapy, plasma exchange therapy, globulin therapy or radiation therapy within 12 weeks prior to the initiation of test drug * Patients who started the immunosuppressant therapy or increased the dose of immunosuppressant within 12 weeks prior to the initiation of test drug. * Patients who had undergone thymectomy within 24 weeks prior to the initiation of test drug. * Pancreatitis or diabetes * Serum creatinine≦1.5mg/dL