This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for GBT021601-022: A Study of GBT021601 in Participants With Sickle Cell Disease (SCD) (NCT05632354), a na phase 2, phase 3 study. The primary outcome is Number of Participants With Treatment Emergent Adverse Events (TEAEs).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05632354 |
| Phase | Phase 2, Phase 3 |
| Condition | Sickle Cell Disease |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 47 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
Participants with sickle cell disease who had participated in a GBT021601 clinical trial and entered this open-label extension. The safety analysis set was defined as enrolled participants who received at least one dose in the extension study.
Intervention
Osivelotor, administered in dose groups listed as 100 mg, 150 mg, or 200 mg. The record identifies participants with and without delayed start; the details of that timing are not reported in the registry record.
Comparator
There was no randomized control group. The study is listed as a single-group model with allocation recorded as not applicable and no masking. Dose and delayed-start groups are not like-for-like control groups.
Primary question
How many participants experienced a treatment-emergent adverse event during the period from first dose through 56 days after the last dose? The record defines these events but does not report an overall count for this primary endpoint.
This is a safety-focused question in an extension study, not a randomized test of osivelotor against a concurrent comparator. The primary outcome counts participants with treatment-emergent adverse events (TEAEs), including serious and non-serious adverse events. TEAEs were defined as events that were absent before treatment or worsened relative to the pretreatment state during the specified observation period. Whether an event was related to treatment was based on the investigator’s decision.
The registry also lists secondary outcomes concerning vaso-occlusive crises, sickle cell disease-related serious adverse events, and changes in hemoglobin, reticulocytes, lactate dehydrogenase, and unconjugated bilirubin at specified study weeks. Results for those outcomes are not reported in the registry record. Consequently, the posted information cannot establish the frequency or pattern of those outcomes over the extension period.
3. Trial Design
The record describes an open-label extension study of GBT021601 in participants with sickle cell disease who had participated in a GBT021601 clinical trial. Osivelotor is listed as the intervention. The study is categorized as Phase 2 and Phase 3, with a single-group model, no masking, and allocation recorded as not applicable. These design features mean that the posted dose groups should not be interpreted as randomized treatment and control arms.
Enrollment is listed as 47. The study start date is 2023-01-05, primary completion is listed as 2025-02-13, and the status is terminated. The reason for termination is not reported in the registry record. The timing and circumstances of individual participants’ entry into the extension, as well as the criteria for delayed start, are not reported in the registry record.
The safety outcome population included enrolled participants who received at least one dose in the extension study. Participants were analyzed according to the assigned daily maintenance dose on study day 1 in the extension. The registry lists groups with and without delayed start at 100 mg and 150 mg, as well as a group without delayed start at 200 mg. The posted counts therefore describe distinct listed cohorts; they do not create a randomized comparison between doses or against no treatment.
The primary outcome is the number of participants with TEAEs over a period beginning with the first dose and ending 56 days after the last dose, approximately up to 736 days. The record lists 15 outcome measures and zero analyses. It does not report a statistical analysis plan, sample-size justification, interim analyses, or a reason for the listed termination status. Those details should not be inferred from the study’s phase, enrollment, or outcome definitions.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Before assignment: A total of 47 participants from only Part A of the parent study C5351004 \[NCT05431088\] were enrolled in the current study C5351005 \[NCT05632354\]. Study was terminated based on Sponsor's decision. There were no participants enrolled in 'Participants With Delayed Start: Osivelotor 200 mg' group.
Overall Study
| Stage | Participants Without Delayed Start: Osivelotor 100 Milligram (mg) | Participants Without Delayed Start: Osivelotor 150 mg | Participants Without Delayed Start: Osivelotor 200 mg | Participants With Delayed Start: Osivelotor 100 mg | Participants With Delayed Start: Osivelotor 150 mg |
|---|---|---|---|---|---|
| STARTED | 18 | 17 | 1 | 5 | 6 |
| COMPLETED | 0 | 0 | 0 | 0 | 0 |
| NOT COMPLETED | 18 | 17 | 1 | 5 | 6 |
Reasons for not completing this period:
| Reason | Participants Without Delayed Start: Osivelotor 100 Milligram (mg) | Participants Without Delayed Start: Osivelotor 150 mg | Participants Without Delayed Start: Osivelotor 200 mg | Participants With Delayed Start: Osivelotor 100 mg | Participants With Delayed Start: Osivelotor 150 mg |
|---|---|---|---|---|---|
| Adverse Event | 0 | 0 | 0 | 1 | 0 |
| Lost to Follow-up | 1 | 0 | 0 | 0 | 0 |
| Pregnancy | 3 | 0 | 0 | 0 | 0 |
| Study terminated by sponsor | 12 | 16 | 1 | 4 | 6 |
| Withdrawal by Subject | 1 | 1 | 0 | 0 | 0 |
| Non-compliance with study treatment | 1 | 0 | 0 | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Safety analysis set included all enrolled participants who had received at least one dose of study drug in this OLE study. Participants were analyzed according to the assigned daily maintenance dose on study day 1 in the OLE study.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
Population: Safety analysis set included all enrolled participants who had received at least one dose of study drug in this open-label extension (OLE) study. Participants were analyzed according to the assigned daily maintenance dose on study day 1 in the OLE study.
| Characteristic | Unit | Participants Without Delayed Start: Osivelotor 100 mg | Participants Without Delayed Start: Osivelotor 150 mg | Participants Without Delayed Start: Osivelotor 200 mg | Participants With Delayed Start: Osivelotor 100 mg | Participants With Delayed Start: Osivelotor 150 mg | Total |
|---|---|---|---|---|---|---|---|
| Participants analysed | 18 | 17 | 1 | 5 | 6 | 47 | |
| Age, Continuous | Years | 33.4 (SD 13.75) | 27.2 (SD 10.19) | 27.0 (SD NA) | 26.4 (SD 11.70) | 27.8 (SD 14.41) | 29.6 (SD 12.25) |
| Sex: Female, Male: Female | Participants | 9 | 11 | 1 | 3 | 4 | 28 |
| Sex: Female, Male: Male | Participants | 9 | 6 | 0 | 2 | 2 | 19 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 | 0 | 0 | 0 | 0 | 0 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 18 | 17 | 1 | 5 | 6 | 47 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 | 0 | 0 | 0 |
| Race/Ethnicity, Customized: Race – African | Participants | 10 | 12 | 0 | 5 | 6 | 33 |
| Race/Ethnicity, Customized: Race – Black or African American | Participants | 8 | 5 | 1 | 0 | 0 | 14 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants With Treatment Emergent Adverse Events (TEAEs), measured over From first dose of study drug up to 56 days after last dose of study drug (approximately up to 736 days).
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the number of participants with treatment-emergent adverse events (TEAEs). It is a participant count, rather than a count of every individual event. The registry defines an adverse event as an untoward medical occurrence in a participant who has received a pharmaceutical product during a clinical investigation. A TEAE is an event that was absent before treatment or worsened relative to the pretreatment state and occurred between the first dose and 56 days after the last dose.
The stated observation window is approximately up to 736 days. TEAEs include serious and non-serious adverse events. The record defines serious events by criteria including death, life-threatening events, inpatient hospitalization or prolongation of hospitalization, persistent or significant disability or incapacity, congenital anomaly or birth defect, and other medically significant events. Investigators determined whether an adverse event was related to treatment.
General statistical context: a participant-level safety count provides a direct description of how many people experienced at least one qualifying event. It does not by itself describe how many events each person experienced, their duration, or their severity beyond separately classified serious-event information. Nor does a count without a concurrent control group estimate what would have occurred under another treatment or without treatment.
The endpoint definition and analysis population are reported, but the overall primary-endpoint result is not reported in the registry record. The listed serious and other adverse-event counts by cohort are safety information, but they do not supply an overall TEAE count in the record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies treatment-emergent adverse events as the primary endpoint and specifies a safety analysis set. However, an overall result for the number of participants with TEAEs is not reported in the registry record. There are also zero analyses listed. The available information therefore does not provide an estimate with which to quantify the primary endpoint across the study population or to assess its statistical precision.
The posted safety figures are separated by delayed-start status and dose. They report participants at risk, participants with serious adverse events, participants with other adverse events, and deaths for each listed cohort. These counts can be read as descriptive cohort information. They should not be treated as evidence that one dose or start group had a higher or lower risk than another: the study was not a randomized comparison, and the registry explicitly warns that the groups are not like-for-like controls. Differences in group composition, exposure, follow-up, or other factors could affect such counts, and the record does not provide analyses to address those possibilities.
The listed serious-event terms include Pneumonia, Anaemia, Haemolysis, Sepsis, Thermal burn, and Cholecystitis, each with a reported percentage. The denominator and calculation details for those percentages are not reported in the registry record, so they should be read as registry-listed values rather than as estimates whose underlying population can be reconstructed from the record. The listed death counts are not accompanied by causes or an assessment of relationship to treatment.
Secondary outcomes include annualized rate of vaso-occlusive crisis, sickle cell disease-related serious adverse events, and changes from baseline in several laboratory measures at specified weeks. Their results are not reported in the registry record. No conclusion about those outcomes can be drawn from the endpoint list alone.
General statistical context: a confidence interval describes the uncertainty around an estimate under a specified statistical model. A point estimate without an interval can give a less complete picture of precision, while a p-value addresses a particular hypothesis under its assumptions and does not measure clinical importance. The registry record does not report confidence intervals, p-values, or other inferential results for the primary endpoint. The safety counts are therefore descriptive rather than a basis for a claim of comparative effect.
The study’s terminated status is recorded, but its reason is not reported in the registry record. That status alone does not establish why the study ended or imply a particular safety or efficacy finding. Interpretation should remain bounded to the design, endpoint definitions, and descriptive figures that are posted.
9. Statistical Methods Explained
General statistical context: the choice of statistical method depends on the endpoint, design, follow-up, and analysis population. For this study, the primary endpoint is a count of participants with at least one treatment-emergent adverse event, and the record defines a safety set of participants who received at least one study dose. It does not report an inferential analysis for this endpoint. That absence matters: descriptive counts can summarize observed events, but they do not alone quantify uncertainty or support a controlled comparison.
What does a participant count represent?
A participant count records whether each person experienced a qualifying event during the defined observation period. It differs from an event count: one participant can have more than one event, while a participant count generally represents that person once for the relevant outcome. The registry’s primary endpoint is explicitly a number of participants with TEAEs. The posted safety information separately lists participants with serious and other adverse events by cohort, but an overall primary TEAE count is not reported in the registry record.
General statistical context: if a participant-level outcome is expressed as a proportion, its uncertainty depends on the number of participants and the observed frequency, among other modeling choices. A confidence interval can convey a range of values compatible with the data and model. Without the overall endpoint result or an interval, the precision of the primary safety estimate cannot be evaluated from the registry record.
Why does the design limit comparisons?
The study is listed as open-label, single-group, and not randomized, with allocation recorded as not applicable. The dose and delayed-start cohorts are descriptive subgroups, not assigned randomized comparison groups. General statistical context: randomization can help balance measured and unmeasured characteristics between groups, while a nonrandomized comparison may be affected by differences in who entered each group, when exposure began, and how long participants were observed. The record does not report an analysis that adjusts for such differences. It is therefore inappropriate to treat the cohort counts as a controlled estimate of dose effects or treatment effects.
Masking is listed as none. General statistical context: in an open-label study, participants and investigators know the treatment being given. This can affect reporting or assessment of some outcomes, although the registry record does not establish that such effects occurred in this study. The investigator determined relatedness of adverse events to treatment, so that assessment reflects investigator judgment rather than a blinded adjudication stated in the record.
What do the planning assumptions mean?
The sample-size assumptions describe a planning illustration rather than the study’s own design justification. They specify a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. The assumptions also distinguish time-to-event planning, which uses a total event count, from other planning, which uses participants per arm. These are general planning conventions, not evidence that the extension study randomized participants equally or was designed around those assumptions. The record does not report the study’s sample-size justification, and planning illustrations must not be interpreted as observed power or as a result of the trial.
General statistical context: power is a design property calculated under assumptions about the effect, variability, analysis, and sample size. It is not a measure of how likely a result is to be true after the data have been observed. A planning illustration based on an observed effect can help show how required sample size changes under hypothetical assumptions, but it does not substitute for a prespecified design calculation. The underlying numerical planning outputs are not reported in the registry record.
Why can event rates vary in follow-up studies?
General statistical context: event counts can be influenced by how long participants are followed and how much time they remain at risk. An annualized rate attempts to relate events to time, unlike a simple participant count over a fixed observation window. The registry lists an annualized rate of vaso-occlusive crisis as a secondary outcome, but it does not report its result or the analysis details needed to explain how follow-up time was handled.
General statistical context: over-dispersion occurs when variation in event counts is greater than a chosen statistical model expects. If present, it can make standard errors and confidence intervals from a simpler model too small. The registry record does not report an analysis model for the annualized outcome or indicate whether over-dispersion was assessed. No claim about the model used should be inferred from the outcome title.
In summary, the record supplies outcome definitions, the safety population, study design categories, and cohort-level safety counts. It does not report inferential methods or results for the primary endpoint. General explanations of confidence intervals, power, and count models describe statistical concepts; they do not establish which methods were applied in this study.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 15 outcome measures, including the primary TEAE count and secondary safety, vaso-occlusive crisis, and laboratory-change outcomes. It lists zero analyses. A multiplicity plan—such as a prespecified hierarchy, adjustment procedure, or distinction between confirmatory and exploratory tests—is not reported in the registry record. Without such information and without reported inferential results, it is not possible to assess how multiple statistical comparisons were handled.
Missing-data methods are not reported in the registry record. The record does not state how participants who discontinued, missed visits, or had incomplete laboratory measurements were handled for each outcome. Nor does it report imputation methods, sensitivity analyses, or rules for censoring follow-up. These details are important because missingness can affect both the number of participants contributing to an outcome and the interpretation of estimates.
The stated safety analysis set included enrolled participants who received at least one dose in the extension. Participants were analyzed according to the assigned daily maintenance dose on study day 1. The registry does not report a separate intention-to-treat population, a per-protocol population, or the number included in each outcome analysis. It is also not reported whether every participant in the safety set contributed the same duration of observation.
General statistical context: multiplicity refers to the increased chance of false-positive findings when many hypotheses are tested. Missing-data approaches rely on assumptions about why values are unavailable and how missingness relates to observed or unobserved outcomes. These principles explain why the absent analysis details matter, but they do not imply that any particular bias or error occurred in this study.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Participants Without Delayed Start: Osivelotor 100 mg | 5 | 18 | 27.8% |
| Participants Without Delayed Start: Osivelotor 150 mg | 4 | 17 | 23.5% |
| Participants Without Delayed Start: Osivelotor 200 mg | 1 | 1 | 100.0% |
| Participants With Delayed Start: Osivelotor 100 mg | 2 | 5 | 40.0% |
| Participants With Delayed Start: Osivelotor 150 mg | 2 | 6 | 33.3% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Participants Without Delayed Start: Osivelotor 100 mg | 0 of 18 |
| Participants Without Delayed Start: Osivelotor 150 mg | 0 of 17 |
| Participants Without Delayed Start: Osivelotor 200 mg | 0 of 1 |
| Participants With Delayed Start: Osivelotor 100 mg | 1 of 5 |
| Participants With Delayed Start: Osivelotor 150 mg | 0 of 6 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Participants Without Delayed Start: Osivelotor 100 mg | 14 of 18 |
| Participants Without Delayed Start: Osivelotor 150 mg | 13 of 17 |
| Participants Without Delayed Start: Osivelotor 200 mg | 1 of 1 |
| Participants With Delayed Start: Osivelotor 100 mg | 5 of 5 |
| Participants With Delayed Start: Osivelotor 150 mg | 5 of 6 |
Most frequent serious adverse event terms
| Event term | Organ system | Participants Without Delayed Start: Osivelotor 100 mg | Participants Without Delayed Start: Osivelotor 150 mg | Participants Without Delayed Start: Osivelotor 200 mg | Participants With Delayed Start: Osivelotor 100 mg | Participants With Delayed Start: Osivelotor 150 mg |
|---|---|---|---|---|---|---|
| Anaemia | Blood and lymphatic system disorders | 1 of 18 | 1 of 17 | 0 of 1 | 1 of 5 | 1 of 6 |
| Haemolysis | Blood and lymphatic system disorders | 1 of 18 | 0 of 17 | 0 of 1 | 1 of 5 | 0 of 6 |
| Pneumonia | Infections and infestations | 0 of 18 | 1 of 17 | 1 of 1 | 0 of 5 | 0 of 6 |
| Sepsis | Infections and infestations | 0 of 18 | 0 of 17 | 0 of 1 | 1 of 5 | 1 of 6 |
| Tachycardia paroxysmal | Cardiac disorders | 1 of 18 | 0 of 17 | 0 of 1 | 0 of 5 | 0 of 6 |
| Cholecystitis | Hepatobiliary disorders | 0 of 18 | 1 of 17 | 0 of 1 | 0 of 5 | 0 of 6 |
| Gastroenteritis | Infections and infestations | 1 of 18 | 0 of 17 | 0 of 1 | 0 of 5 | 0 of 6 |
| Vestibular neuronitis | Infections and infestations | 0 of 18 | 1 of 17 | 0 of 1 | 0 of 5 | 0 of 6 |
| Thermal burn | Injury, poisoning and procedural complications | 0 of 18 | 0 of 17 | 0 of 1 | 0 of 5 | 1 of 6 |
| Osteonecrosis | Musculoskeletal and connective tissue disorders | 0 of 18 | 1 of 17 | 0 of 1 | 0 of 5 | 0 of 6 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Participants Without Delayed Start: Osivelotor 100 mg | Participants Without Delayed Start: Osivelotor 150 mg | Participants Without Delayed Start: Osivelotor 200 mg | Participants With Delayed Start: Osivelotor 100 mg | Participants With Delayed Start: Osivelotor 150 mg |
|---|---|---|---|---|---|---|
| Malaria | Infections and infestations | 4 of 18 | 7 of 17 | 0 of 1 | 3 of 5 | 3 of 6 |
| Urinary tract infection | Infections and infestations | 2 of 18 | 5 of 17 | 0 of 1 | 3 of 5 | 3 of 6 |
| Pain | General disorders | 2 of 18 | 3 of 17 | 0 of 1 | 0 of 5 | 3 of 6 |
| Asymptomatic bacteriuria | Infections and infestations | 1 of 18 | 2 of 17 | 0 of 1 | 1 of 5 | 0 of 6 |
| Respiratory tract infection | Infections and infestations | 0 of 18 | 2 of 17 | 0 of 1 | 1 of 5 | 0 of 6 |
| Upper respiratory tract infection | Infections and infestations | 2 of 18 | 0 of 17 | 0 of 1 | 0 of 5 | 1 of 6 |
| Hyperkalaemia | Metabolism and nutrition disorders | 0 of 18 | 2 of 17 | 0 of 1 | 1 of 5 | 0 of 6 |
| Arthralgia | Musculoskeletal and connective tissue disorders | 1 of 18 | 0 of 17 | 1 of 1 | 1 of 5 | 0 of 6 |
| Pregnancy | Pregnancy, puerperium and perinatal conditions | 3 of 18 | 0 of 17 | 0 of 1 | 0 of 5 | 0 of 6 |
| Lymphadenopathy | Blood and lymphatic system disorders | 1 of 18 | 0 of 17 | 0 of 1 | 0 of 5 | 1 of 6 |
Serious events with the highest arm-level rate: pneumonia (100.0%), anaemia (20.0%), haemolysis (20.0%), sepsis (20.0%), thermal burn (16.7%).
The registry lists serious adverse event counts by delayed-start status and dose. For participants without delayed start, the 100 mg group lists 18 participants at risk and 5 with serious adverse events; the 150 mg group lists 17 at risk and 4 with serious adverse events; and the 200 mg group lists 1 at risk and 1 with serious adverse event. For participants with delayed start, the 100 mg group lists 5 at risk and 2 with serious adverse events, while the 150 mg group lists 6 at risk and 2 with serious adverse events. The listed death counts are 0, 0, 0, 1, and 0 in those same group descriptions, respectively.
The registry also lists participants with other adverse events in each group: 14, 13, 1, 5, and 5, respectively. These are descriptive counts, not a randomized comparison. A participant may have both serious and other adverse events; the record does not state whether the categories are mutually exclusive, so they should not be added to create a total.
The listed serious-event terms are Pneumonia (100.0%), Anaemia (20.0%), Haemolysis (20.0%), Sepsis (20.0%), Thermal burn (16.7%), and Cholecystitis (5.9%). The denominator and percentage calculation details are not reported in the registry record. Causes of death and treatment relatedness of the serious events are also not reported in these figures.
12. What the Result Does, and Does Not, Mean
The registry record supports a descriptive account of a safety-focused extension study: it identifies the enrolled population, the intervention, the endpoint definition, the safety analysis set, and adverse-event counts across listed dose and delayed-start groups. It also documents that the study was open-label and not a randomized comparison. These features define what the posted information can address and where interpretation must stop.
The record does not report the overall primary endpoint result, inferential analyses, or uncertainty estimates. It therefore does not establish the frequency of TEAEs for the full safety population with a reported estimate and precision, nor does it provide a statistical comparison between dose groups. The serious and other adverse-event counts remain descriptive. They do not show whether any apparent differences are attributable to dose, delayed start, underlying participant characteristics, or exposure and follow-up differences.
The record also lists secondary outcome definitions but does not report their results. The listed outcomes include vaso-occlusive crisis, sickle cell disease-related serious adverse events, and changes in hemoglobin, reticulocytes, lactate dehydrogenase, and unconjugated bilirubin. Their inclusion in the registry is not evidence of a particular result.
General statistical context: an observed event count is not, by itself, a causal estimate. A concurrent randomized comparator can help distinguish treatment effects from background changes and group differences, but this study is not described as having one. Similarly, absence of a reported statistical test is not proof that two groups are equivalent; it means the record does not provide a test or estimate to interpret.
The terminated status is a registry fact, but the reason is not reported in the registry record. It cannot be used to infer a safety concern, a lack of benefit, or a particular study outcome. The defensible interpretation is limited to the study’s stated design, definitions, and posted descriptive counts.
13. Why This Trial Matters Statistically
This study illustrates an important distinction in clinical-trial interpretation: a registry can define a safety endpoint and provide subgroup event counts without reporting the primary endpoint result or an inferential analysis. The definition tells readers what was intended to be counted, while the analysis population clarifies who could contribute. Neither replaces an outcome estimate with information about precision.
The record also makes clear why design labels matter. A single-group, open-label extension can describe safety observations among participants who entered and received study drug. It does not create a randomized control comparison. Dose and delayed-start cohorts may be useful descriptive groupings, but their counts cannot be read as if assignment made the groups exchangeable. This is especially relevant when the groups differ in size and when follow-up duration or entry timing is not fully described.
The registry includes serious and other adverse-event counts, a listed death count in one cohort, and serious-event terms with percentages. These details show why safety reporting requires attention to denominators, categories, and attribution. The record does not explain the denominator for the term percentages or report causes of death and treatment relatedness for the group counts. Careful statistical reading avoids filling those gaps with assumptions.
Finally, 15 outcome measures are listed but zero analyses are listed. Without results, uncertainty intervals, or multiplicity and missing-data methods, the record does not support inferential conclusions about either primary or secondary outcomes. This distinction between outcome registration and outcome reporting is useful for researchers evaluating what a trial record can—and cannot—contribute to an evidence base.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The most immediate limitation is that the overall result for the primary outcome, number of participants with TEAEs, is not reported in the registry record. The record lists cohort-level counts for serious and other adverse events, but does not provide an overall TEAE count, confidence interval, p-value, or inferential analysis. There are zero analyses listed.
The study is open-label and single-group, with no randomized control comparison. Its dose and delayed-start cohorts should not be treated as equivalent groups for estimating a treatment or dose effect. The record does not report adjustment for differences among these cohorts, nor does it provide the details needed to assess comparability or differences in exposure and follow-up.
Enrollment is listed as 47, but the registry record does not report the number contributing to each secondary outcome or the amount of missing data. The duration of observation for each participant, handling of incomplete data, and outcome-specific analysis populations are not reported. The reason for termination is also not reported in the registry record.
The serious-event term percentages are listed without denominator or calculation details. The posted group death counts are not accompanied by causes or a treatment-relatedness assessment. Although the record defines investigator assessment of adverse-event relatedness, the listed counts do not establish which events were considered related. These gaps limit how specifically the safety figures can be interpreted.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: GBT021601-022: A Study of GBT021601 in Participants With Sickle Cell Disease (SCD) — NCT05632354.
- Registry record last updated 2026-03-19; status last verified 2026-03.
- Results first posted 2026-03-19.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
This is an open-label extension study of osivelotor in participants with sickle cell disease who had participated in a GBT021601 clinical trial. The record lists Phase 2 and Phase 3, a single-group model, no masking, enrollment of 47, and terminated status. The primary outcome is the number of participants with treatment-emergent adverse events over a period from first dose through 56 days after last dose, approximately up to 736 days.
The safety population included enrolled participants who received at least one dose. Cohort-level serious and other adverse-event counts and listed serious-event terms are reported. The overall primary endpoint result, secondary outcome results, inferential analyses, missing-data methods, multiplicity approach, and reason for termination are not reported in the registry record.