What the trial was testing
The trial enrolled 274 patients with sickle cell disease. The study was sponsored by Global Blood Therapeutics and tracked outcomes across the full group of patients who matched the trial's eligibility profile.
It was a large trial designed to confirm whether the treatment works well enough for wider use. Trials at this stage are designed to produce evidence regulators and physicians can act on — not just observations to follow up later.
What the results showed
Meaningful increases in hemoglobin across patients regardless of genotype.
Blood · 2025 · NCT04195633
These findings — that showed a hemoglobin increase of more than 1 g/dL after treatment with voxelotor — were published in the Blood and represent the headline result of the study.
Researchers tracked outcomes across 274 patients enrolled in the trial. The result was consistent enough across the group that the team felt confident reporting it.
What this means for patients
For patients with sickle cell disease, this result changes the calculus on what to ask their care team about. Whether it changes day-to-day care depends on factors like disease subtype, prior treatments, and where the patient is in their care journey.
What you can do now
Voxelotor (Oxbryta) received FDA approval for sickle cell disease. Ask your hematologist whether it is appropriate for your situation and genotype.
Eligibility for the treatments mentioned above depends on specific test results and clinical history. Bring this summary, the trial name, and your most recent labs or pathology report to your next visit.
Open sickle cell disease trials
A Safety, Efficacy, and Pharmacokinetic (PK) Study of HBI-002, an Oral Carbon Monoxide (CO) Therapeutic, in Subjects With Sickle Cell Disease (SCD)
This is a multi-center, open label Phase 2a clinical trial in subjects with sickle cell disease to assess safety, tolerability, pharmacokinetics, and pharmacodynamics of HBI-002, an orally administered liquid containing carbon monoxide (CO), with doses daily for 14 days.
Study of Erythrocyte Parameters and Hypercoagulability in Sickle Cell Disease (SCD-TGA)
Sickle cell disease (SCD) is an inherited haemoglobinopathy disorder caused by mutations in HBB gene with amino-acid substitution on β globin chain. The consequence is synthesis of altered haemoglobin S (HbS) which polymerises in red blood cell (RBC) at deoxygenated state. SCD is associated with chronic haemolytic anaemia, vaso-occlusive crisis (VOC) leading to frequent hospitalisation. The aim of the study was to to investigate whether a combination of routine laboratory biomarkers of haemolysis could be used to predict VOC development in confirmed SCD patients.