The U.S. Food and Drug Administration approved Oxbryta™ (voxelotor) for the treatment of sickle cell disease (SCD) in adults and pediatric patients aged 12 years and older. The oral agent is the first to directly inhibit sickle hemoglobin polymerization.
Improved hemoglobin response compared with placebo
The approval was based on the results of a double-blind, multicenter clinical trial that included 274 patients with SCD: 90 patients received voxelotor 1,500 mg, 92 received voxelotor 900 mg, and 92 received placebo. At the start of the study, two-thirds (65%) of patients were receiving hydroxyurea.
The hemoglobin response rate (defined as hemoglobin increase of at least 1 g/dL from baseline to week 24; primary endpoint) was 51.1% in the voxelotor 1,500 mg cohort compared with 6.5% in the placebo group (P<0.0001).
The voxelotor 1,500 mg voxelotor cohort had a mean change in hemoglobin of 1.14 g/dL compared with –0.08 g/dL in the placebo group. Voxelotor-treated patients also had better percent change in indirect bilirubin (–29.08% vs. –3.16%, respectively) and percent reticulocyte count (–19.93% vs. 4.54%, respectively) compared with placebo.
Common adverse events associated with voxelotor include headache, diarrhea, abdominal pain, nausea, fatigue, rash, and pyrexia.