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 Siplizumab for Sickle Cell Disease Transplant (NCT06078696), a na phase 1, phase 2 study. The primary outcome is Failure Rate.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT06078696 |
| Phase | Phase 1, Phase 2 |
| Condition | Anemia, Sickle Cell |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 1 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Columbia University |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns patients with advanced sickle cell disease undergoing allogeneic hematopoietic stem cell transplantation. The condition listed in the registry record is sickle cell anemia. The record reports enrollment of 1 participant, but does not disclose participant-level characteristics or summary-level outcome data.
Intervention
The intervention was a siplizumab-based transplant conditioning approach. The treatment plan describes 5 siplizumab infusions: the first 14 days before stem cell infusion, the second 6 days before, and the remaining doses on the day before, the day of, and the day after stem cell infusion. The study summary also describes premedication to reduce allergic-reaction risks. Other listed interventions include exchange transfusion, total body irradiation, stem cell infusion, cyclophosphamide, mesna, sirolimus, and rituximab or a biosimilar.
Comparator
There was no concurrent comparator group. The registry classifies the study as single-group, with allocation recorded as not applicable. Consequently, the design does not provide a randomized or like-for-like comparison of siplizumab-based conditioning against another approach.
Primary question
The primary question was whether the defined failure endpoint occurred after transplantation. The endpoint combines graft failure, grades III-IV graft-versus-host disease (GVHD), or death at 100 days. The stated assessment timeframe is 12 months after stem cell transplant. The registry describes failure rate as a safety endpoint and says the participant’s data were not analyzed or disclosed to protect confidentiality.
3. Trial Design
NCT06078696, titled Siplizumab for Sickle Cell Disease Transplant, is a phase 1 and phase 2 study sponsored by Columbia University. The official title describes siplizumab-based conditioning for hematopoietic stem cell transplantation in patients with advanced sickle cell disease. The study started on 2023-09-28, had a listed primary completion date of 2024-12-11, and is recorded as terminated.
The design is classified as single-group, with allocation marked not applicable and masking recorded as none. This is not a randomized comparison, and there is no control arm. The single-group structure means the registry record cannot support a direct comparison between the listed transplant approach and a separate treatment strategy. Enrollment is recorded as 1.
The intervention description places siplizumab within a transplant regimen rather than describing it as a stand-alone treatment. Participants were to receive 5 infusions at specified times around stem cell infusion. The study summary also describes medications before siplizumab to reduce allergic-reaction risks. Other listed drugs and procedures include exchange transfusion, total body irradiation, stem cell infusion, cyclophosphamide 50mg, mesna, oral sirolimus, and rituximab or a biosimilar. The intervention list describes what was included in the study record; it does not establish which components the participant completed.
The registry lists one primary endpoint and secondary outcomes addressing engraftment, GVHD, transplant-related toxicities and infections, donor chimerism, and immune reconstitution. It reports zero analyses. The protocol’s detailed statistical analysis plan, sample-size justification, interim-analysis approach, and analysis-population definitions are not reported in the registry record.
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.
Overall Study
| Stage | Siplizumab |
|---|---|
| STARTED | 1 |
| COMPLETED | 1 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Data was not analyzed or disclosed in an effort to protect participant confidentiality (n=1). Additionally, since there is only one participant, it is not possible to report summary level data.
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: Data was not analyzed or disclosed in an effort to protect participant confidentiality (n=1).
| Characteristic | Unit | Siplizumab |
|---|---|---|
| Participants analysed | 0 | |
| Age, Categorical: <=18 years | — | |
| Age, Categorical: Between 18 and 65 years | — | |
| Age, Categorical: >=65 years | — | |
| Sex: Female, Male: Female | — | |
| Sex: Female, Male: Male | — | |
| Ethnicity (NIH/OMB): Hispanic or Latino | — | |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | — | |
| Ethnicity (NIH/OMB): Unknown or Not Reported | — | |
| Race (NIH/OMB): American Indian or Alaska Native | — | |
| Race (NIH/OMB): Asian | — | |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | — | |
| Race (NIH/OMB): Black or African American | — | |
| Race (NIH/OMB): White | — | |
| Race (NIH/OMB): More than one race | — | |
| Race (NIH/OMB): Unknown or Not Reported | — | |
| Region of Enrollment: United States | participants | — |
6. Primary Endpoint
The registry lists the primary outcome as Failure Rate, measured over 12 Months Post Stem Cell Transplant.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is called failure rate and is designated as a safety endpoint. It is a composite: failure is defined by graft failure, grades III-IV GVHD, or death at 100 days. The listed endpoint timeframe is 12 months after stem cell transplant.
Graft failure includes two definitions. Primary graft rejection is the absence of donor cells, defined as donor cells < 5%, assessed by bone marrow or peripheral blood chimerism assays by Day 42. Late graft rejection is the absence of donor hematopoietic cells, defined as <5%, beyond Day 42 in a patient who had initial evidence of hematopoietic recovery with > 20% donor cells. The record specifies that grades III-IV GVHD are assessed using Center for International Blood and Marrow Transplant Research and NIH Consensus Criteria.
A composite endpoint can capture more than one clinically important type of safety event under a common outcome definition. Its interpretation depends on understanding each component: the endpoint does not reveal which event occurred unless component-level results are reported. The registry record does not disclose or analyze the participant’s endpoint data, so it gives no estimate of the failure rate and no account of any individual component. The stated endpoint definition therefore describes what was intended to be assessed, not an observed finding.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The record establishes the study question, the transplant regimen’s described components, and the endpoint definition. It does not provide an analyzed outcome result. The registry explicitly states that data were not analyzed or disclosed to protect participant confidentiality and that summary-level data could not be reported because enrollment was 1. As a result, there is no posted estimate of failure rate, no uncertainty interval, and no reported account of whether the composite endpoint or its individual components occurred.
This absence of an outcome estimate is not evidence that the endpoint was absent. Nor does the record establish that the endpoint occurred. The appropriate reading is that the registry record does not permit an assessment of the observed primary outcome. The same caution applies to the listed secondary outcomes, including time to engraftment, GVHD of any grade, transplant-related toxicities, significant infections, donor chimerism, and immune reconstitution.
The study’s single-group design also limits what could be concluded even if an outcome estimate were available. Without a concurrent comparator, an outcome could be described for the studied participant, but the design would not directly estimate how outcomes differ under another conditioning strategy. A single-group observation cannot by itself separate the effects of siplizumab from those of the other transplant procedures and medications listed in the record, or from the broader transplant context.
The registry lists the study as terminated and provides start and primary-completion dates. Those administrative details do not explain why the study was terminated, whether the participant completed the regimen, or whether follow-up was complete. The reason for termination and those details are not reported in the registry record.
The planning illustrations described for this analysis should be understood as design calculations, not as evidence about participant outcomes or as observed power. Their stated assumptions include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, even though the registered trial itself is single-group. The illustrations are not a substitute for trial-specific results, and no inferential conclusion about safety or efficacy follows from them.
In short, the registry record supports a description of the intended safety question and study structure, but not an estimate of the endpoint or a treatment-effect conclusion. The disclosed information is too limited to quantify risk, characterize precision, or compare this regimen with another approach.
9. Statistical Methods Explained
What does a single-group design establish?
A single-group study follows participants receiving the study approach without a concurrent control group. It can describe what was planned and, when outcome data are available, what was observed in that group. It does not directly compare outcomes with those under an alternative approach. Random allocation is not part of this study: allocation is listed as not applicable, and the design is classified as single-group. Thus, there is no randomized contrast to interpret.
In this study, the intervention is a transplant regimen with multiple listed procedures and medications, including siplizumab. If an event were observed, a single-group design would not isolate the contribution of each regimen component. More generally, comparisons across different groups can be affected by differences in who enters each group and how care is delivered. Randomized allocation is one method used to support a fair comparison, but it is not used.
What does the composite endpoint capture?
The primary endpoint combines graft failure, grades III-IV GVHD, or death at 100 days. Composite endpoints can be useful when a study aims to capture several types of important outcome under one definition. They can also make interpretation less direct: an overall composite result does not identify which component drove it. Component-level reporting is needed to distinguish graft rejection from severe GVHD or death. In this record, neither the composite outcome nor component results are disclosed.
The endpoint definition includes timing and laboratory criteria for graft failure. Primary graft rejection refers to absence of donor cells, defined as donor cells < 5%, assessed by bone marrow or peripheral blood chimerism assays by Day 42. Late graft rejection refers to absence of donor hematopoietic cells (<5%) beyond Day 42 after initial evidence of hematopoietic recovery with > 20% donor cells. The record also identifies the criteria used to assess grades III-IV GVHD. These definitions clarify what would count as an event; they do not indicate that an event occurred.
How should uncertainty be understood?
In general, an estimate describes the observed data, while a confidence interval conveys the range of values compatible with those data under the statistical method used. A narrow interval indicates greater precision than a wide interval, but neither an estimate nor its interval removes limitations in study design or measurement. Here, the endpoint data are not analyzed or disclosed, so no endpoint estimate or confidence interval is reported. There is consequently no statistical precision to assess for the primary outcome.
In general, small amounts of data provide limited information about how outcomes might vary across a broader population. That matters particularly for uncommon or serious outcomes: observing no event in a small study would not, by itself, establish that the event cannot occur. In this record, even that kind of observation cannot be made because the participant’s outcome data are withheld. The absence of a reported event count must not be treated as a zero event count.
What are the planning calculations for?
Planning calculations address how much information a future study might need to detect a specified effect under stated assumptions. The described illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the target effect is expressed as a stated fraction of the observed effect. These are planning assumptions, not descriptions of the registered study’s actual design. The registered study has one group and no like-for-like control arm.
Such calculations are not observed power. Observed power is sometimes calculated after a study using its estimated effect, but it does not supply missing evidence or replace an estimate with its uncertainty. A planning illustration is a hypothetical design aid: its meaning depends on the assumed effect, allocation, outcome type, and statistical model. The registry record does not report the trial’s own sample-size justification or statistical plan. The assumptions stated for the illustrations should therefore not be attributed to the sponsor’s protocol.
For time-to-event outcomes, the described planning approach expresses the requirement as a total number of events using the Schoenfeld method. For other outcome types, it expresses a requirement as participants per arm. These conventions describe the calculation format, not an observed requirement or an enrollment target for this single-group study. No unreported calculation values should be inferred from those methodological descriptions.
Why does over-dispersion matter in general?
For count outcomes, a simple statistical model may assume that the variability is tied closely to the average count. Over-dispersion occurs when the observed variability is greater than that assumption allows. If it is ignored, standard errors can be too small and confidence intervals or tests can appear more decisive than warranted. More flexible modeling can account for extra variability. The registry record does not report a count-outcome analysis or a modeling approach for over-dispersion, so this is general statistical context rather than a description of the study’s analysis.
Overall, the registry record contains outcome definitions and design details but no disclosed primary-outcome analysis. Statistical methods can explain how estimates, uncertainty, composite outcomes, and planning calculations are generally interpreted; they cannot recover the missing participant-level result or establish a treatment effect.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary safety endpoint and secondary outcomes covering time to engraftment, GVHD of any grade, other transplant-related toxicities, significant transplant-related infections, donor chimerism, and immune reconstitution. It reports zero analyses. The specific statistical procedures used to analyze these outcomes, any hierarchy among secondary outcomes, and any adjustment for multiple testing are not reported in the registry record.
Multiplicity arises when researchers assess several outcomes or conduct several statistical tests. The more inferences made, the greater the chance that at least one result may appear noteworthy by chance if no adjustment or testing strategy is used. In general, prespecifying a primary outcome and a testing strategy helps readers understand which result is confirmatory and how secondary findings should be interpreted. The registry identifies a primary endpoint, but does not report enough of the analysis plan to determine how multiplicity was handled.
The primary endpoint data were not analyzed or disclosed in an effort to protect participant confidentiality. The registry states that summary-level data cannot be reported because enrollment was 1. It does not report the reason for termination, whether all planned observations were collected, how missing observations were handled, or which analysis population would have been used. Those details are not reported in the registry record.
Missing or undisclosed data should not be interpreted as an absence of events. Without reported participant flow, outcome availability, or analysis-population definitions, it is not possible to assess completeness of follow-up or potential bias from missingness. No imputation method, sensitivity analysis, or missing-data assumption is reported.
11. What the Result Does, and Does Not, Mean
The record means that a phase 1 and phase 2, single-group study was registered to assess a siplizumab-based conditioning approach for allogeneic transplantation in sickle cell disease. Its primary safety endpoint was defined using graft failure, grades III-IV GVHD, or death at 100 days, with an endpoint timeframe of 12 months after transplant. The study is recorded as terminated, and its enrollment is 1.
The record does not disclose an analyzed primary outcome or summary-level outcome data. It therefore does not show an estimated failure rate, whether any of the endpoint components occurred, or how precisely an outcome could be estimated. It also does not establish that no events occurred. The listed secondary outcomes likewise do not have reported analyses.
The design does not include a comparator group, so it cannot provide a randomized estimate of how outcomes differ from another transplant-conditioning strategy. The regimen includes several listed interventions, and the single-group design cannot separate the effect of siplizumab from other components of care. These limits apply independently of whether results are disclosed.
The record also does not explain the reason for termination, the completion of the planned regimen, or the completeness of follow-up. These omissions prevent conclusions about the course of the study beyond the administrative status and dates recorded. General statistical principles and planning illustrations do not fill those gaps. They can clarify what would be needed to estimate an outcome or plan a future comparison, but they do not establish safety, efficacy, or a treatment effect for this study.
12. Why This Trial Matters Statistically
This study is statistically notable because its question concerns a complex transplant regimen, while its design is single-group and its enrollment is 1. That combination sharply limits the information available for estimating an outcome and does not permit a concurrent treatment comparison. The registry record is a reminder that a clearly defined endpoint and detailed intervention description are not substitutes for analyzable outcome data.
The primary endpoint combines distinct events: graft failure, grades III-IV GVHD, and death at 100 days. A composite can collect important safety outcomes into one measure, but interpretation depends on reporting which components occurred. Since the participant’s data were not analyzed or disclosed, neither the overall endpoint nor its components can be characterized in the registry record.
Transparency about unavailable data also matters for statistical interpretation. The record explains the confidentiality rationale for withholding participant-level data and states that summary-level data could not be reported. It does not report an analysis plan, sample-size justification, or analysis populations. Readers should distinguish these gaps from a negative finding: missing results are not evidence of no risk or no event.
The stated planning assumptions illustrate a separate statistical purpose. Hypothetical sample-size calculations can inform future research design, but they are not observed power and cannot create evidence about outcomes in this study. Because the planning assumptions describe equal allocation between two arms while the registered study is single-group, they should not be read as the trial’s actual design.
For biostatisticians and clinical researchers, the central lesson is to keep design, endpoint definition, analysis, and disclosure distinct. The record supplies detail on the first two, but not the outcome analysis needed to estimate the primary endpoint.
13. 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 important trial-specific limitation is that enrollment was 1 and the registry reports no analyzed or disclosed outcome data. The stated confidentiality rationale prevents summary-level reporting, leaving no estimate of the primary endpoint and no reported results for the listed secondary outcomes. Consequently, precision, event patterns, and outcome completeness cannot be assessed.
The single-group design has no concurrent comparator. Even with complete outcome reporting, it would not provide a randomized comparison against another conditioning approach. The intervention is also a multi-component transplant regimen: exchange transfusion, total body irradiation, stem cell infusion, and multiple drugs are listed alongside siplizumab. The record does not support attributing a hypothetical outcome to siplizumab alone.
The study is recorded as terminated, but the reason for termination is not reported in the registry record. The record does not state whether the participant received all planned infusions or whether follow-up through the stated endpoint timeframe was complete. It also does not report missing-data handling, analysis-population definitions, the sponsor’s sample-size justification, interim analyses, or a detailed statistical analysis plan.
The endpoint combines different safety events, and no component-level results are available. Although the endpoint definition gives criteria for graft failure and identifies GVHD grading criteria, the registry does not report how events were adjudicated or how outcome data were analyzed. The absence of these details limits interpretation of the endpoint beyond its stated definition.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Siplizumab for Sickle Cell Disease Transplant — NCT06078696.
- Registry record last updated 2026-06-10; status last verified 2026-06.
- Results first posted 2026-02-27.
- 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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17. Record Summary
NCT06078696 is a Columbia University phase 1 and phase 2 study of siplizumab-based conditioning for allogeneic stem cell transplantation in advanced sickle cell disease. It is classified as single-group, with allocation not applicable and no masking. Enrollment is recorded as 1. The study started on 2023-09-28, has a primary completion date of 2024-12-11, and is listed as terminated.
The primary safety endpoint is failure rate, defined by graft failure, grades III-IV GVHD, or death at 100 days, with a stated timeframe of 12 months after transplant. The registry says the data were not analyzed or disclosed to protect participant confidentiality and that summary-level data could not be reported. It lists secondary outcomes but reports zero analyses. The reason for termination, outcome estimates, and detailed statistical analysis plan are not reported in the registry record.