Sickle Cell DiseasePhase 3034OLENCT03573882
Study to Assess the Effect of Long-term Treatment With Voxelotor in Participants Who Have Completed Treatment in Study GBT440-031
A Phase 3 study testing Voxelotor in people with Sickle Cell Disease, run by Pfizer at 60 sites in 11 countries.
Trial summary
Open Label Extension Study of Voxelotor Clinical Trial Participants with Sickle Cell Disease Who Participated in Voxelotor Clinical Trials Read more about this study
- Who is it for?
- Ages 12 to 65 years
- 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
- 179 participants
- Where
- 60 sitesin 11 countries
- Study dates
- 6 Jun 2018to 12 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 12 to 65 years
- All sexes
- No healthy volunteers
- Child, Adult, Older adult
Who may be able to join
- Male or female study participants with SCD who participated and received study treatment in Study GBT440-031.
- Note: Participants in GBT440-031 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.
- Females of child-bearing potential are required to have a negative urine pregnancy test prior to dosing on Day 1.
- Female participants of child-bearing potential must use highly effective methods of contraception to 30 days after the last dose of study drug. Male participants must use barrier methods of contraception to 30 days after the last dose of study drug.
- Participant has provided written informed consent or assent (the ICF must be reviewed and signed by each participant; in the case of pediatric participants, both the consent of the participant's legal representative or legal guardian, and the participant's assent must be obtained).
Who cannot join
- Female who is breast-feeding or pregnant.
- Participant withdrew consent from Study GBT440-031.
- Participant was lost to follow-up from Study GBT440-031.
- Participant requiring chronic dialysis.
- Any medical, psychological, safety, or behavioral conditions, which, in the opinion of the Investigator, may confound safety interpretation, interfere with compliance, or preclude informed consent.
Trial locations and contacts
60 sites in 11 countries.
60 sites in 11 countries
United States34 sites
Children's Healthcare of Atlanta - Scottish Rite
Atlanta, Georgia, 30342
Johns Hopkins University/Sickle Cell Infusion Center
Baltimore, Maryland, 21287
St. Jude Affiliate Clinic Baton Rouge
Baton Rouge, Louisiana, 70808
Our Lady of the Lake Physician Group-Medical Oncology
Baton Rouge, Louisiana, 70809
Brigham and Women's Hospital
Boston, Massachusetts, 02115
Brigham and Women's Hospital Research Pharmacy
Boston, Massachusetts, 02215
Dana Farber Cancer Institute
Boston, Massachusetts, 02215
UNC Hospitals
Chapel Hill, North Carolina, 27514
Clinical and Translational Research Center (CTRC)
Chapel Hill, North Carolina, 27599
Medical University of South Carolina - Comprehensive Sickle Cell Clinic
Charleston, South Carolina, 29425
Medical University of South Carolina: Investigational Drug Services Pharmacy
Charleston, South Carolina, 29425
University of Illinois at Chicago Clinical Research Center
Chicago, Illinois, 60612
University of Illinois Hospital and Health Science System
Chicago, Illinois, 60612
Children's Hospital of Michigan
Detroit, Michigan, 48201
Duke University Medical Center
Durham, North Carolina, 27710
Investigational Drug Service, Duke University Hospital
Durham, North Carolina, 27710
Texas Children's Hospital - Investigational Pharmacy
Houston, Texas, 77030
Texas Children's Hospital
Houston, Texas, 77030
Indiana Hemophilia and Thrombosis Center
Indianapolis, Indiana, 46260
Arkansas Primary Care Clinic, PA
Little Rock, Arkansas, 72204
Methodist Comprehensive Sickle Cell Clinic
Memphis, Tennessee, 38104
Jackson Memorial Hospital (Investigational Drug Services)
Miami, Florida, 33136
Jackson Memorial Hospital
Miami, Florida, 33136
University of Miami Hospital & Clinics/SCCC, Research Pharmacy (Investigational Drug Services)
Miami, Florida, 33136
University of Miami
Miami, Florida, 33136
University Medical Center New Orleans
New Orleans, Louisiana, 70112
Columbia University Medical Center - Herbert Irving Pavilion
New York, New York, 10032
Newark Beth Israel Medical Center
Newark, New Jersey, 07112
UCSF Benioff Children's Hospital Oakland
Oakland, California, 94609
Lynn Health Science Institute
Oklahoma City, Oklahoma, 73112
Thomas Jefferson University
Philadelphia, Pennsylvania, 19107
University of Pittsburgh Medical Center (UPMC)
Pittsburgh, Pennsylvania, 15232
Clinical Research Services Unit- Virginia Commonwealth University
Richmond, Virginia, 23298
Montefiore - Einstein Center for Cancer Care
The Bronx, New York, 10461
Egypt6 sites
Alexandria Clinical Research Center, Faculty of Medicine, Alexandria University
Alexandria
Alexandria Clinical Research Center, Faculty of Medicine
Alexandria
Zagazig University Hospital
Alsharkia
Abu El Rich Hospital,Cairo University Hospital
Cairo, 11541
Ain Shams University Hospital
Cairo
The Egyptian Thalassemia Association ( E.T.A)
Cairo
United Kingdom6 sites
Guys and St. Thomas Hospital NHS Foundation Trust
Great Maze Pond, London, SE1 9RT
Barts Health NHS Trust
London, Greater London, E1 1BB
Homerton University Hospital NHS Foundation Trust
London, Greater London, E9 6SR
King's College Hospital
London, SE5 9RS
Imperial College Healthcare NHS Trust, Hammersmith Hospital
London, W12 0HS
McMillan Cancer Centre
London, WC1E 6AG
Kenya3 sites
KEMRI/CRDR - Kenya Medical Research Insititute - Center for respiratory Disease Research
Nairobi, 00101
Gertrude's Children's Hospital
Nairobi
Centres for Disease Control and Prevention
Siaya, Kisumu County
Turkey (Türkiye)3 sites
Adana Acibadem Hospital
Adana, 01130
Erciyes Universitesi Tip Fakultesi
Kayseri, 38039
Mersin Universitesi Tip Fakultesi Saglik Arastirma ve Uygulama Hastanesi
Mersin, 33343
Netherlands2 sites
Academic Medical Center(AMC)
Amsterdam, 1105 AZ
ErasmusMC
Rotterdam, 3015 CN
Canada1 site
Toronto General Hospital-University Health Network
Toronto, Ontario, M5G 2C4
About this study
Official title: An Open Label Extension Study of Voxelotor (GBT440) Administered Orally to Participants With Sickle Cell Disease Who Have Participated in Voxelotor Clinical Trials
Open Label Extension Study of Voxelotor Clinical Trial Participants with Sickle Cell Disease Who Participated in Voxelotor Clinical Trials
Read the detailed description
This open label extension (OLE), multi-center study will be conducted at approximately 100 clinical sites globally and will be available to eligible participants from study GBT440-031.
The study will enroll participants from GBT440-031 (approximately 435) under any of the following conditions:
- Participant has completed 72 weeks of treatment regardless of dose selection for GBT440-031
- Dose selection has occurred for GBT440-031 and participant is on non-selected dose on GBT440-031
- GBT440-031 study interim data analysis and/or study modifications have occurred
- GBT440-031 study has completed
The objective of this open-label extension (OLE) study is to assess the long-term safety and treatment effect of voxelotor in participants who have completed treatment in study GBT440-031, using the following parameters:
- Safety based upon AEs, clinical laboratory tests, physical examinations (PE) and other clinical measures.
- Frequency of sickle cell disease (SCD)-related complications.
- Hemolytic anemia as measured by hematological laboratory parameters (e.g. hemoglobin, reticulocytes and unconjugated bilirubin).
All participants will receive daily voxelotor treatment.
Participants may receive study drug as long they continue to receive clinical benefit which outweighs risk as determined by the Investigator and/or until the participant has access to voxelotor from an alternative source (i.e., commercialization or through a managed access program).
- Conditions
- Sickle Cell Disease
- Being tested
- Voxelotor
- Keywords
- Open Label Extension
- 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
300mg or 500mg Tablet, Oral, With or Without Food
| Study group | Role | What they receive |
|---|---|---|
| Voxelotor | Other | Participants will receive voxelotor (GBT440) at the highest dose (either 900 mg or 1500 mg) deemed safe by the Data Safety Monitoring Board (DSMB). Receives: Drug: Voxelotor |
What is being measured
The primary outcome is the main question the study is designed to answer.
Number of Participants With Sickle Cell Disease (SCD)-Related Treatment Emergent Adverse Events (TEAEs)
An AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. TEAEs were defined as AEs with onset on or after the date of informed consent until 28 days after last dose of study drug. SCD-related TEAEs included preferred terms (PTs) of sickle cell anaemia with crisis, acute chest syndrome (ACS), pneumonia, priapism, and osteonecrosis. The number of participants with any SCD-related TEAEs was reported in this outcome measure.
Measured: From date of informed consent up to 28 days after last dose of study drug (maximum up to 300.7 weeks)
Number of Participants With Non- SCD-Related TEAEs
An AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. TEAEs were defined as AEs with onset on or after the date of informed consent until 28 days after last dose of study drug. Non-SCD-related TEAEs included all the PTs of TEAEs other than SCD- related TEAEs. The number of participants with any non-SCD-related TEAEs was reported in this outcome measure.
Measured: From date of informed consent up to 28 days after last dose of study drug (maximum up to 300.7 weeks)
Number of Participants With SCD-Related Treatment Emergent Serious Adverse Events (TESAEs)
An SAE is an AE at any dose, in view of investigator resulted in any of following outcomes: death; life-threatening AE; inpatient hospitalization/prolongation of existing hospitalization; persistent/significant incapacity or disability; a congenital anomaly/birth defect and important medical events (IME) that may not result in death, be immediately life threatening; or require hospitalization may be considered serious when based upon medical judgement, they may jeopardize study participant and may require medical or surgical intervention to prevent one of outcomes listed in definition. TESAEs were defined as SAEs with onset on or after the date of informed consent until 28 days after last dose of study drug. Number of participants with SCD-Related TESAEs was reported in this outcome measure.
Measured: From date of informed consent up to 28 days after last dose of study drug (maximum up to 300.7 weeks)
Number of Participants With Non-SCD-Related TESAEs
An SAE is an AE at any dose, in view of investigator resulted in any of following outcomes: death; life-threatening AE; inpatient hospitalization/prolongation of existing hospitalization; persistent/significant incapacity or disability; a congenital anomaly/birth defect and IME that may not result in death, be immediately life threatening; or require hospitalization may be considered serious when based upon medical judgement, they may jeopardize study participant and may require medical or surgical intervention to prevent one of outcomes listed in definition. TESAEs were defined as SAEs with onset on or after the date of informed consent until 28 days after last dose of study drug. Number of participants with non-SCD related TESAEs was reported in this outcome measure.
Measured: From date of informed consent up to 28 days after last dose of study drug (maximum up to 300.7 weeks)
Annualized Incidence Rate (Events Per Person Years) of SCD-Related Complications
Annualized incidence rate was defined as total number of events (i.e. complications observed for all participants) divided by total person years. Total person-years= sum of participant summary period in years where summary period=date of informed consent until the earlier of 28 days after last dose of study drug or end of study date. SCD related complications included acute chest syndrome, cerebrovascular accident, hepatic sequestration, ocular icterus, osteonecrosis, pneumonia, priapism, pulmonary hypertension, retinopathy, sickle cell anaemia with crisis, skin ulcer and splenic sequestration. The 95% CI was based on exact Poisson confidence limits. Incidence rate of all SCD related complications is reported in this outcome measure.
Measured: From date of informed consent up to earlier of 28 days after last dose of study drug or end of study date (maximum up to 300.7 weeks)
Annualized Incidence Rate (VOC Events Per Person Years) of On-Treatment Vaso-occlusive Crisis (VOCs)
Annualized incidence rate was defined as total number of VOC events divided by total person years. Total person-years= sum of participant summary period in years where summary period=date of informed consent to last dose of study drug. VOC during the treatment period was defined as composite of acute painful crisis or acute chest syndrome (ACS) and included the following: moderate to severe pain lasting at least 2 hours; no explanation other than VOC; required oral or parenteral opioids, ketorolac, or other analgesics prescribed or directed by a healthcare professional. The 95% CI was based on exact Poisson confidence limits.
Measured: From date of informed consent to last dose of study drug (maximum up to 296.7 weeks)
Secondary outcomes (4)
Change From Baseline in Hemoglobin Level at Week 48
Change from baseline in hemoglobin at Week 48 was reported in this outcome measure. Baseline value was defined as the last available value (including Week 72, end of treatment [EOT], or end of study [EOS] visits in the parent study GBT440-031 [NCT03036813]) collected on or prior to first dose in GBT440-034.
Measured: Baseline, Week 48
Percent Change From Baseline in Reticulocytes Percentage at Week 48
Percent change from baseline in reticulocytes percentage at Week 48 was reported in this outcome measure. Baseline value was defined as the last available value (including Week 72, EOT, or EOS visits in the parent study GBT440-031 [NCT03036813]) collected on or prior to first dose in GBT440-034.
Measured: Baseline, Week 48
Percent Change From Baseline in Absolute Reticulocytes at Week 48
Percent change from baseline in absolute reticulocytes at Week 48 was reported in this outcome measure. Baseline value was defined as the last available value (including Week 72, EOT, or EOS visits in the parent study GBT440-031 [NCT03036813]) collected on or prior to first dose in GBT440-034.
Measured: Baseline, Week 48
Percent Change From Baseline in Indirect Bilirubin at Week 48
Percent change from baseline in indirect bilirubin at Week 48 was reported in this outcome measure. Baseline value was defined as the last available value (including Week 72, EOT, or EOS visits in the parent study GBT440-031 [NCT03036813]) collected on or prior to first dose in GBT440-034.
Measured: Baseline, Week 48
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted29 Jun 2018
- Study start6 Jun 2018
- Primary completion12 Nov 2024
- Study completion12 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
- Masking
- None (open label)
- Enrolment
- 179 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
- NCT03573882
- Sponsor's protocol ID
- GBT440-034
- Other IDs
- C5341022
- Acronym
- 034OLE
- Status last verified
- Nov 2025
- First submitted
- 15 May 2018
- Last updated
- 18 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 18 Nov 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- An Open Label Extension Study of Voxelotor (GBT440) Administered Orally to Participants With Sickle Cell Disease Who Have Participated in Voxelotor Clinical Trials
- ClinicalTrials.gov ID
- NCT03573882
- Acronym / sponsor ID
- 034OLE / GBT440-034
- Conditions
- Sickle Cell Disease
- Keywords
- Open Label Extension
- 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
- 179 participants (actual)
- Lead sponsor
- PfizerIndustry (pharma, biotech, devices)
- Study start
- 6 Jun 2018 (actual)
- Primary completion
- 12 Nov 2024 (actual)
- Study completion
- 12 Nov 2024 (actual)
- First posted
- 29 Jun 2018 (actual)
- Results
- Posted 18 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 Clinical Trial Participants with Sickle Cell Disease Who Participated in Voxelotor Clinical Trials
Detailed description
This open label extension (OLE), multi-center study will be conducted at approximately 100 clinical sites globally and will be available to eligible participants from study GBT440-031.
The study will enroll participants from GBT440-031 (approximately 435) under any of the following conditions:
- Participant has completed 72 weeks of treatment regardless of dose selection for GBT440-031
- Dose selection has occurred for GBT440-031 and participant is on non-selected dose on GBT440-031
- GBT440-031 study interim data analysis and/or study modifications have occurred
- GBT440-031 study has completed
The objective of this open-label extension (OLE) study is to assess the long-term safety and treatment effect of voxelotor in participants who have completed treatment in study GBT440-031, using the following parameters:
- Safety based upon AEs, clinical laboratory tests, physical examinations (PE) and other clinical measures.
- Frequency of sickle cell disease (SCD)-related complications.
- Hemolytic anemia as measured by hematological laboratory parameters (e.g. hemoglobin, reticulocytes and unconjugated bilirubin).
All participants will receive daily voxelotor treatment.
Participants may receive study drug as long they continue to receive clinical benefit which outweighs risk as determined by the Investigator and/or until the participant has access to voxelotor from an alternative source (i.e., commercialization or through a managed access program).
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Voxelotor | Other | Drug: VoxelotorParticipants will receive voxelotor (GBT440) at the highest dose (either 900 mg or 1500 mg) deemed safe by the Data Safety Monitoring Board (DSMB). |
Who may qualify
- Ages
- 12 to 65 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child, Adult, Older adult
Key inclusion criteria (5 listed)
- Male or female study participants with SCD who participated and received study treatment in Study GBT440-031.
- Note: Participants in GBT440-031 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.
- Females of child-bearing potential are required to have a negative urine pregnancy test prior to dosing on Day 1.
- Female participants of child-bearing potential must use highly effective methods of contraception to 30 days after the last dose of study drug. Male participants must use barrier methods of contraception to 30 days after the last dose of study drug.
- Participant has provided written informed consent or assent (the ICF must be reviewed and signed by each participant; in the case of pediatric participants, both the consent of the participant's legal representative or legal guardian, and the participant's assent must be obtained).
Key exclusion criteria (5 listed)
- Female who is breast-feeding or pregnant.
- Participant withdrew consent from Study GBT440-031.
- Participant was lost to follow-up from Study GBT440-031.
- Participant requiring chronic dialysis.
- Any medical, psychological, safety, or behavioral conditions, which, in the opinion of the Investigator, may confound safety interpretation, interfere with compliance, or preclude informed consent.
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: GBT440300mg or 500mg Tablet, Oral, With or Without Food | Drug | Voxelotor |
Primary outcome
Number of Participants With Sickle Cell Disease (SCD)-Related Treatment Emergent Adverse Events (TEAEs)
Time frame: From date of informed consent up to 28 days after last dose of study drug (maximum up to 300.7 weeks)
An AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. TEAEs were defined as AEs with onset on or after the date of informed consent until 28 days after last dose of study drug. SCD-related TEAEs included preferred terms (PTs) of sickle cell anaemia with crisis, acute chest syndrome (ACS), pneumonia, priapism, and osteonecrosis. The number of participants with any SCD-related TEAEs was reported in this outcome measure.
Number of Participants With Non- SCD-Related TEAEs
Time frame: From date of informed consent up to 28 days after last dose of study drug (maximum up to 300.7 weeks)
An AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. TEAEs were defined as AEs with onset on or after the date of informed consent until 28 days after last dose of study drug. Non-SCD-related TEAEs included all the PTs of TEAEs other than SCD- related TEAEs. The number of participants with any non-SCD-related TEAEs was reported in this outcome measure.
Number of Participants With SCD-Related Treatment Emergent Serious Adverse Events (TESAEs)
Time frame: From date of informed consent up to 28 days after last dose of study drug (maximum up to 300.7 weeks)
An SAE is an AE at any dose, in view of investigator resulted in any of following outcomes: death; life-threatening AE; inpatient hospitalization/prolongation of existing hospitalization; persistent/significant incapacity or disability; a congenital anomaly/birth defect and important medical events (IME) that may not result in death, be immediately life threatening; or require hospitalization may be considered serious when based upon medical judgement, they may jeopardize study participant and may require medical or surgical intervention to prevent one of outcomes listed in definition. TESAEs were defined as SAEs with onset on or after the date of informed consent until 28 days after last dose of study drug. Number of participants with SCD-Related TESAEs was reported in this outcome measure.
Number of Participants With Non-SCD-Related TESAEs
Time frame: From date of informed consent up to 28 days after last dose of study drug (maximum up to 300.7 weeks)
An SAE is an AE at any dose, in view of investigator resulted in any of following outcomes: death; life-threatening AE; inpatient hospitalization/prolongation of existing hospitalization; persistent/significant incapacity or disability; a congenital anomaly/birth defect and IME that may not result in death, be immediately life threatening; or require hospitalization may be considered serious when based upon medical judgement, they may jeopardize study participant and may require medical or surgical intervention to prevent one of outcomes listed in definition. TESAEs were defined as SAEs with onset on or after the date of informed consent until 28 days after last dose of study drug. Number of participants with non-SCD related TESAEs was reported in this outcome measure.
Annualized Incidence Rate (Events Per Person Years) of SCD-Related Complications
Time frame: From date of informed consent up to earlier of 28 days after last dose of study drug or end of study date (maximum up to 300.7 weeks)
Annualized incidence rate was defined as total number of events (i.e. complications observed for all participants) divided by total person years. Total person-years= sum of participant summary period in years where summary period=date of informed consent until the earlier of 28 days after last dose of study drug or end of study date. SCD related complications included acute chest syndrome, cerebrovascular accident, hepatic sequestration, ocular icterus, osteonecrosis, pneumonia, priapism, pulmonary hypertension, retinopathy, sickle cell anaemia with crisis, skin ulcer and splenic sequestration. The 95% CI was based on exact Poisson confidence limits. Incidence rate of all SCD related complications is reported in this outcome measure.
Annualized Incidence Rate (VOC Events Per Person Years) of On-Treatment Vaso-occlusive Crisis (VOCs)
Time frame: From date of informed consent to last dose of study drug (maximum up to 296.7 weeks)
Annualized incidence rate was defined as total number of VOC events divided by total person years. Total person-years= sum of participant summary period in years where summary period=date of informed consent to last dose of study drug. VOC during the treatment period was defined as composite of acute painful crisis or acute chest syndrome (ACS) and included the following: moderate to severe pain lasting at least 2 hours; no explanation other than VOC; required oral or parenteral opioids, ketorolac, or other analgesics prescribed or directed by a healthcare professional. The 95% CI was based on exact Poisson confidence limits.
4 secondary outcomes
Change From Baseline in Hemoglobin Level at Week 48
Time frame: Baseline, Week 48
Percent Change From Baseline in Reticulocytes Percentage at Week 48
Time frame: Baseline, Week 48
Percent Change From Baseline in Absolute Reticulocytes at Week 48
Time frame: Baseline, Week 48
Percent Change From Baseline in Indirect Bilirubin at Week 48
Time frame: Baseline, Week 48
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 18 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
60 sites in 11 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 60 sites in 11 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 5 inclusion and 5 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 18 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 60 sites in United States, Egypt, United Kingdom, Kenya, Turkey (Türkiye) and 6 more countries. 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 18 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 Sickle Cell Disease (SCD)-Related Treatment Emergent Adverse Events (TEAEs) (time frame: From date of informed consent up to 28 days after last dose of study drug (maximum up to 300.7 weeks)). The study lists 6 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 18 Nov 2025.