FDA OKs Novel Treatment Targeting Cause of Sickle Cell Disease

Officials with the FDA have approved voxelotor (Oxbryta, Global Blood Therapeutics [GBT]) tablets for the treatment of sickle cell disease (SCD) in adults and children age 12 years and older, according to a press release.¹

Voxelotor, the only FDA-approved sickle hemoglobin polymerization inhibitor, is the first treatment specifically targeting the root cause of SCD. According to GBT, voxelotor is expected to be available through their specialty pharmacy partner network within 2 weeks.¹

The approval, which comes 3 months ahead of the FDA’s priority review action date, is based on data from the phase 3 Hemoglobin Oxygen Affinity Modulation to Inhibit HbS PolymErization (HOPE) study. The study, which included 274 patients age 12 years and older with SCD, showed clinically meaningful and statistically significant improvements in hemoglobin levels, accompanied by reductions in red blood cell destruction.²

Patients were randomly assigned to receive a once-daily oral dose of 1500 mg voxelotor, 900 mg of voxelotor, or placebo. In the intention-to-treat analysis, a significantly higher percentage of patients had a hemoglobin response in the 1500-mg voxelotor group (51%; 95% confidence interval [CI], 41 to 61) than in the placebo group (7%;95% CI, 1 to 12), according to the results. Additionally, anemia worsened between baseline and week 24 in fewer patients in each voxelotor dose group than in those receiving placebo.²

After 24 weeks of treatment, 51.1% of patients receiving voxelotor achieved a greater than 1 g/dL increase in hemoglobin compared with 6.5% receiving placebo (p<0.001).²

Overall, the percentage of patients with an adverse event that occurred or worsened during the treatment period was similar across the trial groups, according to the study. The most common adverse reactions occurring in ≥10% of patients receiving voxelotor with a difference of >3% compared with placebo were headache, diarrhea, abdominal pain, nausea, fatigue, rash, and pyrexia.²

“Every person with SCD experiences hemoglobin polymerization and suffers from varying severity of anemia and hemolysis,” Elliot Vichinsky, MD, director of hematology/oncology at UCSF Benioff Children’s Hospital, said in a statement.¹ “With today’s approval, Oxbryta, we now have a therapy that significantly improves hemoglobin levels, has a favorable safety profile, and reduces the anemia and hemolysis that inevitably leads to the long-term and often undetected detrimental effects associated with this chronic genetic condition.”

As a condition of accelerated approval, GBT will continue to study voxelotor in the HOPE-KIDS 2 study, a post-approval confirmatory study using transcranial doppler flow velocity to demonstrate a decrease in stroke risk in children ages 2 to 15 years old, according to the release.¹

REFERENCES

• FDA Approves Oxbryta (Voxelotor), the First Medicine Specifically Targeting the Root Cause of Sickle Cell Disease [news release]. Global Blood Therapeutics’ website. https://ir.gbt.com/news-releases/news-release-details/fda-approves-oxbrytatm-voxelotor-first-medicine-specifically. Accessed November 25, 2019.
• Vinchinsky E, Hoppe CC, Ataga KI, et al. A phase 3 randomized trial of voxelotor in sickle cell disease. New England Journal of Medicine. 2019. Doi: 10.1056/NEJMoa1903212