Early Initiation of Oral Therapy With Cyclosporine and Eltrombopag for Treatment Naive Severe Aplastic Anemia (SAA)

Background: Severe aplastic anemia (SAA) is a rare and serious blood disorder. It causes the immune system to turn against bone marrow cells. Standard treatment for SSA is a combination of 3 drugs (Cyclosporine \[CsA\], Eltrombopag \[EPAG\], and horse anti-thymocyte globulin \[h-ATG\]). Researchers want to see if starting people at a lower dose of CsA with EPAG before giving them h-ATG is helpful. Objective: To learn if early initiation of oral therapy with CsA and EPAG is safe and effective in people who have SAA and have not been treated with a course of immunosuppressive therapy and EPAG. Eligibility: People ages 3 and older with SAA Design: Participants will be screened with: * medical history * physical exam * electrocardiogram * blood tests * family history * bone marrow biopsy * current medicines. Participants may be screened remotely via telephone conference. Participants will take a lower oral dose of CsA and EPAG. They will take CsA twice a day for 6 months. They will take EPAG for 6 months. Those who cannot visit the NIH Clinical Center within 72 hours will start taking the drugs at home. They will have weekly telephone calls with NIH staff until they visit the Clinical Center. Participants may get h-ATG at the Clinical Center for 4 days. For this, they will have a central line placed. It is a plastic tube inserted into a neck, chest, or arm vein. Participants will repeat most screening tests throughout the study. Participants will have follow-up visits at the Clinical Center at 3 months, 6 months, and annually for 5 years after the start of the study....