G-CSF + antithymocyte globulin + cyclophosphamide + prednisolone

This is a combination therapy consisting of four agents:

• Granulocyte colony-stimulating factor (G-CSF): A cytokine that stimulates the bone marrow to produce neutrophils and other granulocytes, used to reduce infection risk in patients with neutropenia.
• Antithymocyte globulin (ATG): A polyclonal antibody preparation targeting human T lymphocytes, leading to T-cell depletion via complement-mediated cytotoxicity or apoptosis. Used as an immunosuppressant primarily in transplantation and certain autoimmune conditions.
• Cyclophosphamide: An alkylating agent that crosslinks DNA, leading to cell death. It is used as an immunosuppressant and chemotherapeutic agent.
• Prednisolone: A synthetic glucocorticoid corticosteroid with anti-inflammatory and immunosuppressive properties.

This combination is designed for potent immunosuppression, often considered in severe autoimmune diseases or hematological disorders such as severe aplastic anemia or for certain transplant protocols. The rationale is synergistic suppression of immune responses through multiple mechanisms—T-cell depletion (ATG), broad leukocyte suppression (cyclophosphamide), anti-inflammatory effects (prednisolone), and support of granulopoiesis/recovery from neutropenia (G-CSF).