Sickle Cell DiseasePhase 3NCT04188509
Open-Label Extension of Voxelotor
A Phase 3 study testing Voxelotor in people with Sickle Cell Disease, run by Pfizer at 20 sites in 5 countries.
Trial summary
Open-label extension study of voxelotor for participants with Sickle Cell Disease who have participated in voxelotor clinical trials. Read more about this study
- Who is it for?
- Ages 6 months and older
- Conditions the study is for
- Sickle Cell Disease
- What is being tested?
- Voxelotor
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 162 participants
- Where
- 20 sitesin 5 countries
- Study dates
- 18 Nov 2019to 1 Nov 2024
- Phase
- Phase 3
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 6 months and older
- All sexes
- No healthy volunteers
- Child, Adult, Older adult
Who may be able to join
- Male or female participant with SCD, who participated and received study drug in a GBT-sponsored voxelotor clinical study.
- Note: Participants who discontinued study drug due to an AE, but who remained on study, may be eligible for treatment in this study provided the AE does not pose a risk for treatment with voxelotor.
- Note: Participants who discontinued Study GBT440-032 as the result of an abnormal transcranial Doppler (TCD) flow velocity assessment (≥ 200 cm/sec) are eligible for treatment in this study.
- Participant has provided written consent/assent (for pediatric participants, both the consent of the participant's legal representative or legal guardian and the participant's assent [where applicable] must be obtained).
Who cannot join
- Female participant who is breastfeeding or pregnant
- Participant withdrew consent from a GBT-sponsored voxelotor clinical study
- Known hypersensitivity to voxelotor or any other components of the study drug
- Use of St. John's wort, sensitive cytochrome P450 (CYP) 3A4 substrates with a narrow therapeutic index, or moderate or strong CYP3A4 inducers within 30 days of Day 1
Trial locations and contacts
20 sites in 5 countries.
20 sites in 5 countries
United States6 sites
Children's Healthcare of Atlanta Scottish Rite
Atlanta, Georgia, 30342
Ann & Robert H. Lurie Children's Hospital of Chicago
Chicago, Illinois, 60611
ECU Physicians, Brody Outpatient Clinic
Greenville, North Carolina, 27834
Children's Mercy Hospital
Kansas City, Missouri, 64108
UPMC Children's Hospital of Pittsburgh
Pittsburgh, Pennsylvania, 15224
Children's National Medical Center
Washington D.C., District of Columbia, 20010
Nigeria5 sites
University of Calabar Teaching Hospital
Calabar, Cross River State, 540281
College of Medicine, University of Ibadan
Ibadan, Oyo State, 200212
Barau Dikko Teaching Hospital/Kaduna State University
Kaduna, 800212
Aminu Kano Teaching Hospital
Kano, 700233
Lagos University Teaching Hospital
Lagos, 100254
Egypt4 sites
Alexandria University Hospital - Clinical Research Center
Alexandria, 21131
Cairo University Hospital, Abu El Rish Hospital
Cairo, 11562
Ain Shams University Hospital - Clinical Research Center (MASRI-CRC)
Cairo
Zagazig University Hospital
Zagazig, Alsharkia
United Kingdom3 sites
University College Hospital NHS Foundation Trust
London, Greater London, NW1 2PG
Barts Health NHS Trust , The Royal London Hospital
London, E1 1BB
Guy'S and St Thomas' Nhs Foundation Trust
London, SE1 7EH
Lebanon2 sites
American University of Beirut - Medical Center
Beirut
Nini Hospital
Tripoli
About this study
Official title: An Open-Label Extension Study of Voxelotor Administered Orally to Participants With Sickle Cell Disease Who Have Participated in Voxelotor Clinical Trials
Open-label extension study of voxelotor for participants with Sickle Cell Disease who have participated in voxelotor clinical trials.
Read the detailed description
Open-label extension (OLE) study of voxelotor for participants with Sickle Cell Disease who have participated in voxelotor clinical trials. Up to approximately 600 participants with sickle cell disease (SCD), will be enrolled at approximately 70 clinical sites globally. All participants will receive voxelotor once daily, administered orally as tablets, dispersible tablets, or powder for oral suspension formulation. The objective of this OLE is to assess the safety of, and SCD-related complications of, long-term treatment with voxelotor, in participants who have completed treatment in a Global Blood Therapeutics (GBT)-sponsored voxelotor clinical study.
- Conditions
- Sickle Cell Disease
- Being tested
- Voxelotor
- Medical subject headings
- Anemia, Sickle Cell
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
VoxelotorDrug
Also called GBT440
All participants will receive voxelotor once daily (QD), administered orally as tablets, dispersible tablets, or a powder for oral suspension formulation (powder formulation packaged as stick packs).
| Study group | Role | What they receive |
|---|---|---|
| Voxelotor | Experimental | All participants will receive voxelotor once daily (QD), administered orally as tablets, dispersible tablets, or a stick pack formulation (powder blend formulation packaged as stick packs). Participants aged ≥ 12 years and/or ≥ 40 kgs will receive a voxelotor dose of 1500 mg QD. Participants aged < 12 years and < 40 kgs will receive weight based dosing of voxelotor. The participant's weight at study entry will be used to determine the starting voxelotor dose in this study. Participants may receive study drug as long they continue to receive clinical benefit that outweighs risk as determined by the investigator and/or until the participant has access to voxelotor from an alternative source. Receives: Drug: Voxelotor |
What is being measured
The primary outcome is the main question the study is designed to answer.
Number of Participants With Treatment Emergent Adverse Events (AEs)
An AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered to be drug related. A treatment emergent AE was defined as an AE with an onset date on or after the date of informed consent until 28 days after discontinuation of drug. AEs included both serious AEs (SAEs) and all non-SAEs. An SAE was an AE or suspected adverse reaction that, at any dose, in the view of the either the investigator or sponsor, resulted in any of the following outcomes: death, was life-threatening, resulted in persistent disability/incapacity; constituted a congenital anomaly/birth defect; was important medical event; required inpatient hospitalization or prolongation of existing hospitalization.
Measured: From date of informed consent until 28 days after last dose of study drug (maximum up to 4.31 years)
Number of Participants With SAEs
An AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered to be drug related. An SAE was an AE or suspected adverse reaction that, at any dose, in the view of the either the investigator or sponsor, resulted in any of the following outcomes: death, was life-threatening, resulted in persistent disability/incapacity; constituted a congenital anomaly/birth defect; was important medical event; required inpatient hospitalization or prolongation of existing hospitalization.
Measured: From date of informed consent until 28 days after last dose of study drug (maximum up to 4.31 years)
Number of Participants With Sickle Cell Disease (SCD) Related TEAEs and SAEs
SCD-related AEs were common complications associated with the study participant's SCD and were not considered to be related to voxelotor unless judged by the investigator to have worsened in severity and/or frequency or changed in nature during the study. SCD-related complications included the following: sickle cell anemia with crisis, acute chest syndrome (ACS), pneumonia, priapism, and osteonecrosis. A treatment emergent AE was defined as an AE with an onset date on or after the date of informed consent until 28 days after discontinuation of drug. An SAE was an AE or suspected adverse reaction that, at any dose, in the view of either the investigator or sponsor, resulted in any of the following outcomes: death, was life-threatening, resulted in persistent disability/incapacity; constituted a congenital anomaly/birth defect; was important medical event; required inpatient hospitalization or prolongation of existing hospitalization.
Measured: From date of informed consent until 28 days after last dose of study drug (maximum up to 4.31 years)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted6 Dec 2019
- Study start18 Nov 2019
- Primary completion1 Nov 2024
- Study completion1 Nov 2024
Why it stopped: Emerging clinical data evaluated by Pfizer and shared with regulatory authorities indicates that the risk profile of voxelotor in people with SCD exceeds the benefits observed in previously generated global research and requires further assessment.
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for Sickle Cell DiseaseStudies of the same condition, open and under way.
- More trials run by PfizerThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 3
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Model description
- Open-Label Extension study available to eligible participants from GBT-sponsored voxelotor clinical studies.
- Masking
- None (open label)
- Enrolment
- 162 participants (actual)
Sponsor and investigators
- Lead sponsor
- Pfizer
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Pfizer CT.gov Call Center, Study director, Pfizer
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04188509
- Sponsor's protocol ID
- GBT440-038
- Other IDs
- 2019-003144-76, C5341023, 2019
- Status last verified
- Oct 2025
- First submitted
- 3 Dec 2019
- Last updated
- 13 Nov 2025
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.
- Expanded access
- Available
Study at a glance
From the registry record, last updated by the sponsor on 13 Nov 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- An Open-Label Extension Study of Voxelotor Administered Orally to Participants With Sickle Cell Disease Who Have Participated in Voxelotor Clinical Trials
- ClinicalTrials.gov ID
- NCT04188509
- Acronym / sponsor ID
- GBT440-038
- Conditions
- Sickle Cell Disease
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- TerminatedReason stopped: Emerging clinical data evaluated by Pfizer and shared with regulatory authorities indicates that the risk profile of voxelotor in people with SCD exceeds the benefits observed in previously generated global research and requires further assessment.
- Enrolment
- 162 participants (actual)
- Lead sponsor
- PfizerIndustry (pharma, biotech, devices)
- Study start
- 18 Nov 2019 (actual)
- Primary completion
- 1 Nov 2024 (actual)
- Study completion
- 1 Nov 2024 (actual)
- First posted
- 6 Dec 2019 (actual)
- Results
- Posted 13 Nov 2025
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Open-label extension study of voxelotor for participants with Sickle Cell Disease who have participated in voxelotor clinical trials.
Detailed description
Open-label extension (OLE) study of voxelotor for participants with Sickle Cell Disease who have participated in voxelotor clinical trials. Up to approximately 600 participants with sickle cell disease (SCD), will be enrolled at approximately 70 clinical sites globally. All participants will receive voxelotor once daily, administered orally as tablets, dispersible tablets, or powder for oral suspension formulation. The objective of this OLE is to assess the safety of, and SCD-related complications of, long-term treatment with voxelotor, in participants who have completed treatment in a Global Blood Therapeutics (GBT)-sponsored voxelotor clinical study.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- Open-Label Extension study available to eligible participants from GBT-sponsored voxelotor clinical studies.
| Arm | Type | Receives |
|---|---|---|
| Voxelotor | Experimental | Drug: VoxelotorAll participants will receive voxelotor once daily (QD), administered orally as tablets, dispersible tablets, or a stick pack formulation (powder blend formulation packaged as stick packs). Participants aged ≥ 12 years and/or ≥ 40 kgs will receive a voxelotor dose of 1500 mg QD. Participants aged < 12 years and < 40 kgs will receive weight based dosing of voxelotor. The participant's weight at study entry will be used to determine the starting voxelotor dose in this study. Participants may receive study drug as long they continue to receive clinical benefit that outweighs risk as determined by the investigator and/or until the participant has access to voxelotor from an alternative source. |
Who may qualify
- Ages
- 6 months and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child, Adult, Older adult
Key inclusion criteria (4 listed)
- Male or female participant with SCD, who participated and received study drug in a GBT-sponsored voxelotor clinical study.
- Note: Participants who discontinued study drug due to an AE, but who remained on study, may be eligible for treatment in this study provided the AE does not pose a risk for treatment with voxelotor.
- Note: Participants who discontinued Study GBT440-032 as the result of an abnormal transcranial Doppler (TCD) flow velocity assessment (≥ 200 cm/sec) are eligible for treatment in this study.
- Participant has provided written consent/assent (for pediatric participants, both the consent of the participant's legal representative or legal guardian and the participant's assent [where applicable] must be obtained).
Key exclusion criteria (4 listed)
- Female participant who is breastfeeding or pregnant
- Participant withdrew consent from a GBT-sponsored voxelotor clinical study
- Known hypersensitivity to voxelotor or any other components of the study drug
- Use of St. John's wort, sensitive cytochrome P450 (CYP) 3A4 substrates with a narrow therapeutic index, or moderate or strong CYP3A4 inducers within 30 days of Day 1
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| VoxelotorAlso: GBT440All participants will receive voxelotor once daily (QD), administered orally as tablets, dispersible tablets, or a powder for oral suspension formulation (powder formulation packaged as stick packs). | Drug | Voxelotor |
Primary outcome
Number of Participants With Treatment Emergent Adverse Events (AEs)
Time frame: From date of informed consent until 28 days after last dose of study drug (maximum up to 4.31 years)
An AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered to be drug related. A treatment emergent AE was defined as an AE with an onset date on or after the date of informed consent until 28 days after discontinuation of drug. AEs included both serious AEs (SAEs) and all non-SAEs. An SAE was an AE or suspected adverse reaction that, at any dose, in the view of the either the investigator or sponsor, resulted in any of the following outcomes: death, was life-threatening, resulted in persistent disability/incapacity; constituted a congenital anomaly/birth defect; was important medical event; required inpatient hospitalization or prolongation of existing hospitalization.
Number of Participants With SAEs
Time frame: From date of informed consent until 28 days after last dose of study drug (maximum up to 4.31 years)
An AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered to be drug related. An SAE was an AE or suspected adverse reaction that, at any dose, in the view of the either the investigator or sponsor, resulted in any of the following outcomes: death, was life-threatening, resulted in persistent disability/incapacity; constituted a congenital anomaly/birth defect; was important medical event; required inpatient hospitalization or prolongation of existing hospitalization.
Number of Participants With Sickle Cell Disease (SCD) Related TEAEs and SAEs
Time frame: From date of informed consent until 28 days after last dose of study drug (maximum up to 4.31 years)
SCD-related AEs were common complications associated with the study participant's SCD and were not considered to be related to voxelotor unless judged by the investigator to have worsened in severity and/or frequency or changed in nature during the study. SCD-related complications included the following: sickle cell anemia with crisis, acute chest syndrome (ACS), pneumonia, priapism, and osteonecrosis. A treatment emergent AE was defined as an AE with an onset date on or after the date of informed consent until 28 days after discontinuation of drug. An SAE was an AE or suspected adverse reaction that, at any dose, in the view of either the investigator or sponsor, resulted in any of the following outcomes: death, was life-threatening, resulted in persistent disability/incapacity; constituted a congenital anomaly/birth defect; was important medical event; required inpatient hospitalization or prolongation of existing hospitalization.
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 13 Nov 2025.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- To obtain contact information for a study center near you, click here.Link provided by the sponsor.
- Individual participant dataSharing planned: Yes. Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Pfizer CT.gov Call Center study director
Pfizer
20 sites in 5 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing Voxelotor in people with Sickle Cell Disease, run by Pfizer at 20 sites in 5 countries.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: stopped early, as of the sponsor's last update on 13 Nov 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 20 sites in United States, Nigeria, Egypt, United Kingdom, Lebanon. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 13 Nov 2025). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Number of Participants With Treatment Emergent Adverse Events (AEs) (time frame: From date of informed consent until 28 days after last dose of study drug (maximum up to 4.31 years)). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 13 Nov 2025.