On November 25, the U.S. Food and Drug Administration (FDA) granted accelerated approval to voxelotor (Oxbryta) for adults and pediatric patients 12 years of age and older with sickle cell disease.
“[Voxelotor] is an inhibitor of deoxygenated sickle hemoglobin polymerization, which is the central
Richard Pazdur, MD
abnormality in sickle cell disease,” said Richard Pazdur, MD, Director of the FDA’s Oncology Center of Excellence and Acting Director of the Office of Oncologic Diseases in the FDA’s Center for Drug Evaluation and Research. “With [voxelotor], sickle cells are less likely to bind together and form the sickle shape, which can cause low hemoglobin levels due to red blood cell destruction. This therapy provides a new treatment option for patients with this serious and life-threatening condition.”
Efficacy was evaluated in 274 patients with sickle cell disease in HOPE, a randomized, double-blind, placebo-controlled, multicenter trial. Patients were randomly assigned to voxelotor at 1,500 mg (n = 90), 900 mg (n = 92), or placebo (n = 92). Approximately 65% of patients were taking hydroxyurea at trial entry. Patients were enrolled if their baseline hemoglobin was between 5.5 and 10.5 g/dL. Patients on stable hydroxyurea doses continued the drug throughout the trial. Randomization was stratified by whether the patient was already receiving hydroxyurea, by geographic region, and by age. The primary efficacy outcome measure was hemoglobin response rate defined as a hemoglobin increase of more than 1 g/dL from baseline to week 24.
The response rate with voxelotor was 51.1% (46 of 90 patients), compared with 6.5% (6 of 92) with the placebo (P < .0001). Additional efficacy evaluation included change in hemoglobin, percent change in indirect bilirubin, and percent reticulocyte count during this period. In the 1,500-mg voxelotor group, the mean change for hemoglobin, indirect bilirubin, and percent reticulocyte count were 1.14g/dL, –29.08%, and –19.93%, respectively. In the placebo group, the mean change during this time period for hemoglobin, indirect bilirubin, and percent reticulocyte count were –0.08g/dL, –3.16%, and 4.54%, respectively.
The most common adverse reactions (> 10%) reported with voxelotor were headache, diarrhea, abdominal pain, nausea, rash, fatigue, and pyrexia. Product information includes a warning for hypersensitivity and potential laboratory interference.