A review on disease modifying pharmacologic therapies for sickle cell disease

Sickle cell disease (SCD) is an inherited hematologic disease caused by sickle hemoglobin as the predominant RBC hemoglobin or by sickle hemoglobin in combination with other abnormal β-hemoglobin variants like HbC, HbD and others. Sickling of erythrocytes under deoxygenated conditions is the basis of inflammatory and thrombotic cascades which result in multiple serious complications, leading to early morbidity and mortality. While HLA-matched allogeneic bone marrow transplantation is potentially curative, it has considerable limitations due to potential severe toxicities. Despite slow progress towards novel therapeutic strategies for SCD and hydroxyurea being the sole medication that is shown to reduce vaso-occlusive events and mortality for almost 20 years, several pharmacological agents targeting different mechanisms have been examined in clinical trials and recently US- US-FDA-approved, including L-glutamine and crizanlizumab. Voxelotor was previously US-FDA-approved but has been voluntarily withdrawn from the market as the overall benefit did not outweigh the risks. Gene therapies based on CRISPR-Cas9 and lentiviral vectors have been very recently approved. However, excessive costs are a barrier to widespread use. Nonetheless, there is still a large area of unmet needs for patients with SCD, and further research towards better care is warranted.