A new open-label extension study will investigate the long-term safety and efficacy of GBT021601 in patients with sickle cell disease (SCD) who have participated in a previous GBT021601 clinical trial. The study is expected to start January 3, 2023, and is not yet recruiting.

The study protocol includes 12 primary outcome measures. Researchers will evaluate the incidence of treatment-emergent adverse events with the daily dosing of GBT021601, the effects of long-term use of GBT021601 on hemolytic anemia (measured as change from baseline in hematological laboratory parameters), and the long-term effects of GBT021601 treatment on inflammation and quality of life (QOL) assessments.

The effects of GBT021601 treatment on inflammation will be assessed as change from baseline in adhesion of whole blood and white blood cells to microfluidic channels. The impact of GBT021601 treatment on QOL will be measured as change from baseline in QOL assessments including Patient Global Impression of Change, Clinical Global Impression of Change, Patient Global Impression of Severity, and Clinical Global Impression of Severity.

Change from baseline in hemoglobin, reticulocytes, lactate dehydrogenase, and unconjugated bilirubin are also primary outcome measures.

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In addition, researchers will evaluate the pharmacokinetic parameters of long-term use of GBT021601 (secondary outcome measure). Blood and plasma concentrations of GBT021601 will be determined during dosing and 1 to 2 hours after dosing.

All outcome measures will be evaluated every 12 weeks from the time of enrollment until the end of treatment (up to 4 years).

The study will enroll 314 participants of both sexes, aged 6 months and older, who had participated and received the study drug or placebo in the previous Global Blood Therapeutics-sponsored GBT021601 clinical trial. Female participants of childbearing potential must have a negative urine pregnancy test prior to dosing. Moreover, sexually active males and females must consistently use highly effective methods of contraception throughout the study and until 120 days after the last dose of GBT021601.


GBT021601-022: a study of GBT021601 in participants with sickle cell disease (SCD). ClinicalTrials.gov. November 30, 2022. Updated November 30, 2022. Accessed December 7, 2022.