This clinical trial is focused on studying a condition known as severe aplastic anemia. This is a serious blood disorder where the bone marrow fails to produce enough blood cells. The study is investigating a treatment called REGN7257, which is a type of medication known as a monoclonal antibody. Monoclonal antibodies are proteins designed to target specific parts of the immune system. In this case, REGN7257 targets a part of the immune system called the interleukin 2 receptor subunit gamma, which is involved in the body’s immune response.

The purpose of the study is to assess the safety and tolerability of REGN7257 in patients whose severe aplastic anemia has not responded to or has returned after standard immunosuppressive therapy. The study is divided into two parts. In the first part, the focus is on understanding how safe and tolerable the treatment is. In the second part, the study also looks at how effective the treatment is in patients whose condition has relapsed after previous treatments.

Participants in the study will receive REGN7257 through an injection into a vein, a method known as intravenous use. The study will monitor participants for any side effects and measure how their condition responds to the treatment over time. The study aims to provide insights into whether REGN7257 can be a beneficial treatment option for those with severe aplastic anemia who have limited options due to the ineffectiveness of other therapies.