Sickle CellNCT03685721
Genotype -Phenotype Correlation of PKLR Variants With Pyruvate Kinase, 2,3-Diphosphglycerate and Adenosine Triphosphate Activities in Red Blood Cells of People With Sickle Cell Disease
An observational study of Sickle Cell and PKLR Variants, run by National Heart, Lung, and Blood Institute (NHLBI) at 1 site in United States.
Trial summary
Background: Some people with the same disorder on a genetic level have more complications than others. Researchers want to look for a link between the PKLR gene and sickle cell disease (SCD) symptoms. Read more about this study
- Who is it for?
- Ages 18 to 80 yearsHealthy volunteers can take part
- Conditions the study is for
- Sickle Cell, PKLR Variants, Adenosine Triphosphate Activities
- How many people
- 800 participants
- Where
- 1 siteUnited States
- Study dates
- 11 Oct 2018to 1 Jul 2027
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
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 18 to 80 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Study population: The study will be listed on the clinicaltrials.gov, Clinical Center research studies, and the National Heart, Lung and Blood Institute patient recruitment websites. Patients who are followed on other NHLBI sickle cell protocols may be asked to participate in this study, particularly subjects enrolled in the Natural History of Sickle Cell Disease (NCT00081523; 04-H-0161).
Who may be able to join
None listed.
Who cannot join
- Self-reported history of blood transfusion within the last 8 weeks
- Known to have pyruvate kinase deficiency and be on AG348
- All volunteers will undergo the consent process under this protocol to allow for eligibility assessment. Once they have been consented to participate, they will undergo procedures per Protocol.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
National Institutes of Health Clinical Center
Bethesda, Maryland, 20892
For more information at the NIH Clinical Center contact Office of Patient Recruitment (OPR), 800-411-1222 ext. TTY8664111010, prpl@cc.nih.gov
About this study
Official title: Genotype -Phenotype Correlation of PKLR Variants With Pyruvate Kinase, 2,3-Diphosphglycerate and ATP Activities in Red Blood Cells of Patients With Sickle Cell Disease
Background:
Some people with the same disorder on a genetic level have more complications than others. Researchers want to look for a link between the PKLR gene and sickle cell disease (SCD) symptoms. The PKLR gene helps create a protein, called pyruvate kinase that is essential in normal functioning of the red blood cell. Differences in the PKLR gene, called genetic variants, may cause some changes in the pyruvate kinase protein and other proteins, that can affect functioning of the red blood cell adding to the effect of SCD. Researchers can study these differences by looking at DNA (the material that determines inherited characteristics).
Read more
Objective:
To study how the PKLR gene affects sickle cell disease.
Eligibility:
Adults ages 18-80 of African descent. They may have sickle cell disease or not. They must not have had a transfusion recently or have a known deficiency of pyruvate kinase. They cannot be pregnant.
Design:
Participants will be screened with questions.
Participants will have blood drawn by needle in an arm vein. The blood will be genetically tested. Not much is known about how genes affect SCD, so the test results will not be shared with participants or their doctors.
...
Read the detailed description
Polymerization of deoxy-sickle-hemoglobin (deoxy-HbS), the root cause of sickle cell disease (SCD) is influenced by a few factors, a key factor is 2,3-diphosphoglycerate (2,3-DPG) concentration in the red blood cells. 2,3-DPG is an allosteric effector on hemoglobin oxygen binding with a greater binding affinity to deoxygenated hemoglobin than to oxygenated hemoglobin, thus favoring polymerization of deoxy-HbS. In addition, increased 2,3-DPG concentration decreases intracellular pH in red blood cells which further promotes HbS polymerization.
2,3-DPG is an intermediate substrate in the glycolytic pathway, the only source of ATP production in red blood cells. Pyruvate kinase (PK) is a key enzyme in the final step of glycolysis; PK converts phosphoenolpyruvate (PEP) to pyruvate, creating 50% of the total red cell adenosine triphosphate (ATP) that is essential for maintaining integrity of the red cell membrane. Indeed, PK deficiency (PKD) caused by mutations in the PKLR gene that encodes red cell PK, leads to chronic hemolytic anemia. Reduced PK activity leads to accumulation of the upstream enzyme substrates, including 2,3-DPG. While increased 2,3-DPG concentration and reduction of hemoglobin oxygen affinity is beneficial in anemia caused by PKD, increased 2,3-DPG levels combined with decreased intracellular red cell pH can be detrimental in the presence of HbS, as it favors deoxy-HbS polymerisation, and thereby intravascular sickling. Indeed, the combination of PK deficiency and sickle cell trait causing an acute sickling syndrome has been previously reported in two cases.
PKLR mutations, however, are rare but intraerythrocytic PK enzyme levels form a spectrum which suggest that PKLR is likely to be a quantitative trait gene. A genetic diversity in PKLR with a range of SNPs, including several loss-of-function variants have been described in malaria-endemic populations, some of which have been associated with a significant reduction in attacks with Plasmodium falciparum malaria. These observations suggest that similar to HbS, malaria has led to positive selection of PKLR variants in the same geographic regions.
This study seeks to determine the PKLR genetic diversity in our sickle cell cohort, and whether PKLR variants modify PK levels, and activities of 2,3-DPG and ATP, key players in the sickle pathology. If so, PKLR could be another genetic determinant of SCD severity and phenotype; and increasing PK-R activity, which leads to a decrease in intracellular 2,3-DPG concentration, presents an attractive therapeutic target for SCD.
Several approaches have been considered for targeting the polymerization of deoxy-HbS, the root cause of SCD. In addition to agents inducing fetal hemoglobin, other agents that target HbS polymerization through increasing affinity of hemoglobin for oxygen (eg. GBT440), are in clinical trials (NCT03036813; NCT02850406). The results of this study could form the basis for a clinical trial of AG348, an allosteric activator of PK that is already in clinical Phase 2/3 studies for PK deficiency (NCT02476916), for treating acute sickle cell pain.
- Keywords
- ATP, Trait, GDP, Genetics, Natural History
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
| Study group | Role | What they receive |
|---|---|---|
| HbAS | HbAS genotype, of African American descent;Between 18 and 80 years of age | |
| Healthy control | African American descent;Between 18 and 80 years of age | |
| SCD | HbSS, HbSC, HbSbeta-thal has sickle cell disease and is of African American descent;Between 18 and 80 years of age |
What is being measured
The primary outcome is the main question the study is designed to answer.
Genotype the 4 PKLR intron-2 variants
To have genotyped the 4 PKLR intron-2 variants in SCD patients from the NHLBI cohort using genomic DNA and compare them to a cohort of healthy ethnic-matched non-SCD controls and a cohort of sickle cell trait carriers, with those reported in 1000 genome project (http://www.1000genomes.org).
Measured: Upon enrollment of each subject
Analysis of PK-R transcriptome in red blood cells
Have a correlated profile of the PK-R RNA sequence with the 4 PKLR intronic genetic variants.
Measured: Interim analysis performed for each group N=125
Correlation of 2,3-DPG, ATP and pyruvate kinase activities with PKLR intron-2 variants
Assess correlation between the quantitative assays and genotype
Measured: Interim analysis performed for each group N=125
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted26 Sep 2018
- Study start11 Oct 2018
- Primary completion1 Jul 2027 (estimated)
- Study completion1 Jul 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for Sickle CellStudies of the same condition, open and under way.
- More trials run by National Heart, Lung, and Blood Institute (NHLBI)The 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
- Observational
- Observational model
- Case-control
- Time perspective
- Cross-sectional
- Enrolment
- 800 participants (estimated)
Sponsor and investigators
- Sponsor type
- US National Institutes of Health
- Responsible party
- Sponsor
- Investigators
- Swee Lay Thein, M.D., Principal investigator, National Heart, Lung, and Blood Institute (NHLBI)
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT03685721
- Sponsor's protocol ID
- 180146
- Other IDs
- 18-H-0146
- Status last verified
- 23 Oct 2026
- First submitted
- 25 Sep 2018
- Last updated
- 27 Oct 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Publications
Wang X, Asomaning N, Li H, Lundt M, Thein SL. Probing Red Blood Cell Deformability in Sickle Cell Disease, Sickle Cell Trait, and Healthy Controls by Ektacytometry. EJHaem. 2026 Oct 9;7(5):e70416. doi: 10.1002/jha2.70416. eCollection 2026 Oct.
PubMed 42859572
Study at a glance
From the registry record, last updated by the sponsor on 27 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Genotype -Phenotype Correlation of PKLR Variants With Pyruvate Kinase, 2,3-Diphosphglycerate and ATP Activities in Red Blood Cells of Patients With Sickle Cell Disease
- ClinicalTrials.gov ID
- NCT03685721
- Acronym / sponsor ID
- 180146
- Keywords
- ATP, Trait, GDP, Genetics, Natural History
- Study type
- Observational
- Recruitment status
- Recruiting
- Enrolment
- 800 participants (estimated)
- Lead sponsor
- National Heart, Lung, and Blood Institute (NHLBI)US National Institutes of Health
- Study start
- 11 Oct 2018 (actual)
- Primary completion
- 1 Jul 2027 (estimated)
- Study completion
- 1 Jul 2027 (estimated)
- First posted
- 26 Sep 2018 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Background:
Some people with the same disorder on a genetic level have more complications than others. Researchers want to look for a link between the PKLR gene and sickle cell disease (SCD) symptoms. The PKLR gene helps create a protein, called pyruvate kinase that is essential in normal functioning of the red blood cell. Differences in the PKLR gene, called genetic variants, may cause some changes in the pyruvate kinase protein and other proteins, that can affect functioning of the red blood cell adding to the effect of SCD. Researchers can study these differences by looking at DNA (the material that determines inherited characteristics).
Objective:
To study how the PKLR gene affects sickle cell disease.
Eligibility:
Adults ages 18-80 of African descent. They may have sickle cell disease or not. They must not have had a transfusion recently or have a known deficiency of pyruvate kinase. They cannot be pregnant.
Design:
Participants will be screened with questions.
Participants will have blood drawn by needle in an arm vein. The blood will be genetically tested. Not much is known about how genes affect SCD, so the test results will not be shared with participants or their doctors.
...
Detailed description
Polymerization of deoxy-sickle-hemoglobin (deoxy-HbS), the root cause of sickle cell disease (SCD) is influenced by a few factors, a key factor is 2,3-diphosphoglycerate (2,3-DPG) concentration in the red blood cells. 2,3-DPG is an allosteric effector on hemoglobin oxygen binding with a greater binding affinity to deoxygenated hemoglobin than to oxygenated hemoglobin, thus favoring polymerization of deoxy-HbS. In addition, increased 2,3-DPG concentration decreases intracellular pH in red blood cells which further promotes HbS polymerization.
2,3-DPG is an intermediate substrate in the glycolytic pathway, the only source of ATP production in red blood cells. Pyruvate kinase (PK) is a key enzyme in the final step of glycolysis; PK converts phosphoenolpyruvate (PEP) to pyruvate, creating 50% of the total red cell adenosine triphosphate (ATP) that is essential for maintaining integrity of the red cell membrane. Indeed, PK deficiency (PKD) caused by mutations in the PKLR gene that encodes red cell PK, leads to chronic hemolytic anemia. Reduced PK activity leads to accumulation of the upstream enzyme substrates, including 2,3-DPG. While increased 2,3-DPG concentration and reduction of hemoglobin oxygen affinity is beneficial in anemia caused by PKD, increased 2,3-DPG levels combined with decreased intracellular red cell pH can be detrimental in the presence of HbS, as it favors deoxy-HbS polymerisation, and thereby intravascular sickling. Indeed, the combination of PK deficiency and sickle cell trait causing an acute sickling syndrome has been previously reported in two cases.
PKLR mutations, however, are rare but intraerythrocytic PK enzyme levels form a spectrum which suggest that PKLR is likely to be a quantitative trait gene. A genetic diversity in PKLR with a range of SNPs, including several loss-of-function variants have been described in malaria-endemic populations, some of which have been associated with a significant reduction in attacks with Plasmodium falciparum malaria. These observations suggest that similar to HbS, malaria has led to positive selection of PKLR variants in the same geographic regions.
This study seeks to determine the PKLR genetic diversity in our sickle cell cohort, and whether PKLR variants modify PK levels, and activities of 2,3-DPG and ATP, key players in the sickle pathology. If so, PKLR could be another genetic determinant of SCD severity and phenotype; and increasing PK-R activity, which leads to a decrease in intracellular 2,3-DPG concentration, presents an attractive therapeutic target for SCD.
Several approaches have been considered for targeting the polymerization of deoxy-HbS, the root cause of SCD. In addition to agents inducing fetal hemoglobin, other agents that target HbS polymerization through increasing affinity of hemoglobin for oxygen (eg. GBT440), are in clinical trials (NCT03036813; NCT02850406). The results of this study could form the basis for a clinical trial of AG348, an allosteric activator of PK that is already in clinical Phase 2/3 studies for PK deficiency (NCT02476916), for treating acute sickle cell pain.
Study design
- Observational model
- Case-control
- Time perspective
- Cross-sectional
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| HbAS | – | –HbAS genotype, of African American descent;Between 18 and 80 years of age |
| Healthy control | – | –African American descent;Between 18 and 80 years of age |
| SCD | – | –HbSS, HbSC, HbSbeta-thal has sickle cell disease and is of African American descent;Between 18 and 80 years of age |
Who may qualify
- Ages
- 18 to 80 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
- Study population
- The study will be listed on the clinicaltrials.gov, Clinical Center research studies, and the National Heart, Lung and Blood Institute patient recruitment websites. Patients who are followed on other NHLBI sickle cell protocols may be asked to participate in this study, particularly subjects enrolled in the Natural History of Sickle Cell Disease (NCT00081523; 04-H-0161).
Key inclusion criteria (0 listed)
Key exclusion criteria (3 listed)
- Self-reported history of blood transfusion within the last 8 weeks
- Known to have pyruvate kinase deficiency and be on AG348
- All volunteers will undergo the consent process under this protocol to allow for eligibility assessment. Once they have been consented to participate, they will undergo procedures per Protocol.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Primary outcome
Genotype the 4 PKLR intron-2 variants
Time frame: Upon enrollment of each subject
To have genotyped the 4 PKLR intron-2 variants in SCD patients from the NHLBI cohort using genomic DNA and compare them to a cohort of healthy ethnic-matched non-SCD controls and a cohort of sickle cell trait carriers, with those reported in 1000 genome project (http://www.1000genomes.org).
Analysis of PK-R transcriptome in red blood cells
Time frame: Interim analysis performed for each group N=125
Have a correlated profile of the PK-R RNA sequence with the 4 PKLR intronic genetic variants.
Correlation of 2,3-DPG, ATP and pyruvate kinase activities with PKLR intron-2 variants
Time frame: Interim analysis performed for each group N=125
Assess correlation between the quantitative assays and genotype
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 27 Oct 2026.
- Derived from this study: PubMed 42859572Wang X, Asomaning N, Li H, Lundt M, Thein SL. Probing Red Blood Cell Deformability in Sickle Cell Disease, Sickle Cell Trait, and Healthy Controls by Ektacytometry. EJHaem. 2026 Oct 9;7(5):e70416. doi: 10.1002/jha2.70416. eCollection 2026 Oct.
- NIH Clinical Center Detailed Web PageLink provided by the sponsor.
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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.
Swee Lay Thein, M.D. principal investigator
National Heart, Lung, and Blood Institute (NHLBI)
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Sickle Cell and PKLR Variants, run by National Heart, Lung, and Blood Institute (NHLBI) at 1 site in United States.
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 0 inclusion and 3 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: looking for participants now, as of the sponsor's last update on 27 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. 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.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Dianna S Lovins ((301) 480-3765, dianna.lovins@nih.gov), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Genotype the 4 PKLR intron-2 variants (time frame: Upon enrollment of each subject). 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?
On the ClinicalTrials.gov record for NCT03685721, which also lists 1 linked publication.
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 27 Oct 2026.