Butyrate derivatives. New agents for stimulating fetal globin production in the beta-globin disorders.

Stimulating expression of the normal fetal globin genes is a preferred method of ameliorating sickle cell disease and beta-thalassemia for the majority of patients in North America who do not have appropriate bone marrow donors. Due to increased survival of red blood cells that contain both hemoglobin S and hemoglobin F, as little as 4-8% fetal globin synthesis in the bone marrow can produce levels of hemoglobin F of approximately 20% in the peripheral circulation. Some success has been achieved in stimulating hemoglobin F using chemotherapeutic agents (such as hydroxyurea and 5-azacytidine) and growth factors (erythropoietin) that alter erythroid growth kinetics. However, there is reluctance to treat children with chemotherapeutic agents because of possible undesirable long-term side effects. Butyric acid and butyrate derivatives are generally safe compounds that stimulate the promoters of individual fetal and embryonic globin genes and thus provide a more specific therapy. An initial trial with the parent compound, given as arginine butyrate, has demonstrated rapid stimulation of fetal globin expression to levels that can ameliorate these conditions. Phase I trials of an oral butyrate derivative with a long plasma half-life have begun. These agents may provide a new and specific approach for ameliorating the clinical manifestations of sickle cell disease and beta-thalassemia.