The bioactive tetrapeptide goralatide which corresponds to the N-terminus of Thymosin β₄, is a physiological regulator of hematopoiesis and inhibits the entry into the S-phase of murine and human hematopoietic stem cells. Ac-SDKP has been shown to reduce the damage to specific compartments in the bone marrow resulting from treatment with chemotherapeutic agents, ionizing radiations, hyperthermy, or phototherapy. It protects from doxorubicin-induced toxicity. Ac-SDKP is a physiological substrate of angiotensin I- converting enzyme (ACE).