What is the role of voxelotor in the treatment of sickle cell anemia (SCA)?

Updated: May 12, 2021
  • Author: Joseph E Maakaron, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Voxelotor, which was approved by the FDA in November 2019, is the first drug approved by the FDA for sickle cell disease based solely on data showing an increase in hemoglobin. It is indicated for treatment of sickle cell disease in adults and adolescents aged 12 years or older. Voxelotor is a hemoglobin S (HbS) polymerization inhibitor that binds to HbS with a 1:1 stoichiometry and exhibits preferential partitioning to RBCs. By increasing the affinity of Hb for oxygen, voxelotor demonstrates dose-dependent inhibition of HbS polymerization. 

Approval of voxelotor was based on results from a clinical trial that enrolled 274 patients with sickle cell disease and treated them with either 1500 mg or 900 mg PO once daily of voxelotor or placebo. Results showed 51% patients on the higher dose of voxelotor achieved a hemoglobin response, defined as an increase in hemoglobin of at least 1 g/dL after 24 weeks. Just over 6% of the placebo patients had the same hemoglobin response. At week 24, the 1500-mg voxelotor group had significantly greater reductions from baseline in the indirect bilirubin level and percentage of reticulocytes than the placebo group. [63]

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