Using Fostamatinib to Treat Post-Hematopoietic Stem Cell Transplant Immune-mediated Cytopenias: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Using Fostamatinib to Treat Post-Hematopoietic Stem Cell Transplant Immune-mediated Cytopenias (NCT05502783), a na phase 2 study. The primary outcome is Number of Participants Who Were Able to Maintain Hematologic Recovery.

2. Clinical Question

3. Trial Design

This was a phase II, single-group study of fostamatinib for immune-mediated cytopenias after hematopoietic stem cell transplant. The registry records the study as unmasked, with allocation not applicable. It began on 2023-03-10, had a primary completion date of 2023-06-16, and is listed as terminated. Enrollment was 1 participant. These features describe the registered study, but the record does not report why it was terminated.

The intervention was fostamatinib by mouth. The brief description says participants would take tablets twice daily for 12 weeks. The arm description specifies 100 mg BID for 4 weeks and describes a decision at the 4-week evaluation about continuing the same dose if cytopenia improves. The arm description is truncated, so further dose rules should not be inferred. The brief also describes assessments every 2 weeks, with clinic visits at weeks 4 and 12 and other visits potentially by telephone or telehealth.

With no comparator group, the design can describe what happened to the participant who enrolled, but it cannot make a controlled treatment comparison. The lack of masking also means treatment and assessment were not concealed in the registered design. The registry does not report whether any steps were taken to reduce the potential influence of that design on assessments.

The stated primary endpoint assessment times were Baseline, Week 2, Week 4, Week 6, Week 8, and Week 10. The endpoint definition requires improvement in 2 consecutive available readings, while the listed primary time frame does not include Week 12. The record states that the participant withdrew at week 10 and that no data was collected up to week 12. The protocol’s intended handling of this withdrawal or of assessments that were not available is 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: One participant withdrew at week 10 from the study due to lack of efficacy, therefore no data was collected up to week 12.

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.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants Who Were Able to Maintain Hematologic Recovery, measured over Baseline, Week 2, Week 4, Week 6, Week 8, Week 10.

The primary endpoint is the number of participants able to maintain hematologic recovery. It is a count endpoint: it asks whether participants met the recovery definition, rather than estimating the size of an average change across a group. The registry lists assessments at Baseline, Week 2, Week 4, Week 6, Week 8, and Week 10.

Recovery was defined as improvement documented in 2 consecutive available readings, without recent blood product transfusion support in the past 48-72 hours. The criteria depended on the type of cytopenia. For posttransplant anemia, the registry definition states hemoglobin =10 g/dL or at least =2 g/dL above baseline; for symptomatic anemia, it specifies an increase of at least =2 g/dL above baseline. For posttransplant thrombocytopenia, it states platelets = 50 x 10^9/L or at least =20 x 10^9/L above baseline. For posttransplant Evans syndrome, both criteria were required.

A sustained, transfusion-independent recovery definition is intended to distinguish a documented response from a single reading or a reading soon after transfusion support. That is the general statistical rationale for requiring repeated available readings and specifying recent transfusion status. The registry record does not report the observed primary endpoint count, individual readings, or results at any listed assessment. It therefore does not establish how often the endpoint was met.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods help connect a clinical question to a measurable outcome and clarify what conclusions the data can support. In this study, the primary outcome is a count of participants meeting a defined recovery criterion. The registry lists no analyses and does not provide a result for that count. The general concepts below explain how such data are usually interpreted; they do not describe an analysis plan documented for this study.

What does a count endpoint tell the reader?

A count records how many participants meet an outcome definition. It is direct and clinically interpretable when the definition is clear, but its meaning depends on the number assessed and the rules for missing observations. In a larger study, an event count is often considered alongside a denominator and an uncertainty interval. In this record, enrollment is 1, but the primary outcome count and analysis denominator are not reported. It is therefore not possible to estimate an event frequency from the primary outcome record.

The endpoint defines recovery through laboratory thresholds, repeated available readings, and a restriction on recent transfusion support. In general, requiring repeated readings can reduce reliance on a transient measurement. Specifying transfusion status can help distinguish a participant’s own hematologic recovery from a value affected by recent blood product support. Those choices also make consistent measurement and complete assessment important. The registry record does not report how the endpoint was adjudicated or how inconsistent or unavailable readings would be handled.

Why does the single-group design matter?

A comparator provides a reference for interpreting outcomes over the same period. In a randomized comparison, random allocation is intended to make groups comparable on average, so differences between groups can be interpreted with fewer sources of bias than an uncontrolled before-and-after observation. Here, the design is recorded as single-group and allocation as not applicable. There is no within-trial control comparison. The observed course, if reported, could not by itself show what would have happened without fostamatinib.

Masking is another design feature that can affect the interpretation of subjective or judgment-based outcomes. The study is recorded as unmasked. The primary endpoint is based on laboratory criteria, but its definition also includes whether improvement is documented across readings and whether recent transfusion support occurred. In general, prespecified, consistently applied rules can reduce discretionary variation; the registry does not report details of endpoint review or masking of assessors.

What can uncertainty estimates add?

A confidence interval is a general way to express the range of effect sizes compatible with data under a statistical model and its assumptions. It conveys precision as well as direction and magnitude. With very limited data, an interval may be wide, reflecting substantial uncertainty. No confidence interval or other uncertainty estimate for the primary endpoint is reported in the registry record. Given the absence of an outcome result and analysis, a numerical precision assessment cannot be made.

For event counts, some statistical methods assume that observed events vary according to a specified probability model. Over-dispersion is a general concern when the data vary more than a model allows; it can make standard errors too small and intervals too narrow if ignored. This is a concept for interpreting suitable count data, not a claim about the data in this study. The registry does not report a model, variance estimate, or test for over-dispersion.

How should planning illustrations be read?

A sample-size illustration is a planning exercise: it asks what study size might be needed under chosen assumptions about an effect, significance level, allocation, and statistical approximation. It is not an observed result and is not evidence that a completed study had a particular probability of detecting an effect. The registry’s stated illustration assumptions refer to a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect defined as a fraction of the observed effect. Those assumptions do not match the registered single-group design, and no illustration values are reported in the registry record. They must not be read as the trial’s own design or as observed power.

Statistical significance and clinical importance are also different concepts in general. A significance test evaluates data against a null hypothesis under assumptions; it does not establish that an effect is large, durable, or meaningful to patients. An effect estimate with its uncertainty and the endpoint definition are needed to support a fuller interpretation. This registry record reports neither a primary effect estimate nor a primary test result. Consequently, there is no trial-specific significance finding to interpret.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Fostamatinib in Participants Post-Hematopoietic St")
n      <- c(1)
events <- c(0)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Fostamatinib in Participants Post-Hematopoietic St  1  0  0.0  0.0  97.5  0.0  79.3  1.3  84.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 8 outcome measures, including the primary endpoint and secondary outcomes covering hematologic recovery, transfusion and growth-factor requirements, medication doses, chronic GVHD, and steroid dose reduction. Testing or estimating many outcomes can raise multiplicity concerns: when many statistical comparisons are made, the chance of at least one apparently notable result may increase. General approaches include identifying a primary outcome in advance, adjusting inference across selected tests, or treating secondary findings as exploratory. The registry does not report a multiplicity adjustment, a testing hierarchy, or a statistical analysis plan, so the approach cannot be determined from this record.

The registry records 0 analyses. It does not report outcome estimates, test results, confidence intervals, or analysis populations. The primary outcome population note states that one participant withdrew at week 10 due to lack of efficacy and that no data was collected up to week 12. The record does not specify how missing assessments were handled, whether any earlier scheduled measurements were available, or which participants were included in each outcome analysis.

Missing data can affect interpretation when the likelihood of an observation being unavailable is related to the participant’s condition or outcome. That is a general concern, not a conclusion about the withdrawal in this study. The registry gives a reason for the withdrawal but does not report a missing-data method, sensitivity analysis, or imputation procedure. It also does not report whether analyses were intended to include all enrolled participants or only those with particular follow-up. No analysis population should therefore be inferred.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry’s adverse-event summary lists 1 participant at risk for serious adverse events and 0 participants affected by serious adverse events. It records 1 participant at risk for other adverse events and 1 participant affected by other adverse events. Deaths are recorded as 0. These are participant counts, not rates, and the registry does not provide exposure-adjusted estimates.

The categories should be kept distinct: the serious adverse-event count is not the same as the count for other adverse events. The record lists no top serious adverse-event terms. It does not provide the specific other adverse event, its severity, timing, relationship to fostamatinib, or whether it led to a change in treatment. The brief description names potential clinical concerns in its background, but those statements are not reports of events observed in this study.

With enrollment of 1 participant, these safety counts describe only the recorded experience in this study. They cannot characterize how often adverse events might occur in a broader population or establish a comparative safety profile. A count of 0 serious adverse events does not establish that serious harms are absent; the registry does not report enough observations to support that inference.

13. What the Result Does, and Does Not, Mean

The registry describes a phase II study intended to assess fostamatinib for immune-mediated cytopenias after hematopoietic stem cell transplant. Its primary endpoint focused on maintaining hematologic recovery under a specific definition involving repeated readings and recent transfusion support. This provides a clear description of the clinical question the endpoint was designed to address.

The record does not report the observed primary endpoint result. It records enrollment of 1 participant, the study as terminated, and a withdrawal at week 10 due to lack of efficacy, with no data collected up to week 12. Those details describe study conduct and follow-up, but they do not provide a complete account of the participant’s measurements or the endpoint result at earlier times. No conclusion about the frequency of recovery can be drawn from the primary outcome fields.

The design also limits causal interpretation. A single-group study has no concurrent control group, and this study was unmasked. Even if outcome measurements had been reported, changes over time could not be attributed to fostamatinib alone on the basis of this design. Other influences and the natural course of illness would remain possible explanations. This is a general limitation of uncontrolled treatment observations.

The record does not report statistical analyses, uncertainty estimates, or a reason for termination. It does not establish whether the planned assessments were completed or how missing information was treated. The adverse-event summary reports no serious adverse events and one participant affected by other adverse events, but detail about those events is not reported in the registry record. These counts cannot establish the safety profile in a wider population.

Accordingly, the record identifies an important research question and documents a limited study experience, but it does not provide results sufficient to estimate treatment effects or their precision. It neither establishes that fostamatinib improves hematologic recovery nor shows that it does not. Those conclusions would require interpretable outcome data and an appropriate analysis, and a controlled design would be needed for a stronger comparative assessment.

14. Why This Trial Matters Statistically

This study addresses a difficult measurement problem: hematologic recovery after transplant can be defined differently according to the type of cytopenia. The primary endpoint lays out thresholds for anemia, thrombocytopenia, and Evans syndrome, and requires improvement in consecutive available readings without recent blood product support. Such operational definitions matter statistically because they determine which observations count as outcomes and whether results can be compared consistently across participants or studies.

The record also illustrates why trial status and endpoint results should be considered separately. It lists a primary completion date and a terminated status, but the primary outcome result and analyses are not reported. Completion milestones alone cannot answer the efficacy question. A reader needs the outcome observations, a clear denominator, and a description of how incomplete data were handled before interpreting the endpoint.

The single-group design and enrollment of 1 participant make the distinction between descriptive observation and causal evidence especially important. An uncontrolled result, if available, would describe the experience during treatment but could not isolate the effect of treatment from other influences. With very limited enrollment, the record also cannot provide a meaningful account of variation across participants.

Finally, the stated planning assumptions are not a substitute for a documented design or analysis plan. They refer to equal allocation between two arms, whereas the registered study is single-group. Sample-size planning is useful only when its assumptions align with the design and question under study. The record does not report a study-specific statistical plan or explain the relationship between the planning illustration and the registered design. This makes transparent reporting of methods and results particularly important for interpreting the study.

15. 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.

Several limitations are specific to the registry record. Enrollment was 1 participant, the study is listed as terminated, and the primary endpoint result is not reported. The record notes a withdrawal at week 10 due to lack of efficacy and says no data was collected up to week 12, but it does not provide a complete sequence of the participant’s earlier assessments. These omissions prevent an outcome-level assessment of the endpoint.

The study had no comparator group and was unmasked. Therefore, the registry cannot support a controlled estimate of how outcomes differed from what would have happened without fostamatinib. The small enrollment further limits any description of participant-to-participant variation. The registry does not report an analysis plan, uncertainty estimates, missing-data methods, or analysis populations.

The intervention description is incomplete. It states the initial 100 mg BID dose and describes a decision at the 4-week evaluation, but the arm description is truncated. The record therefore does not fully specify the dosing pathway. It also does not report why the study was terminated or provide a detailed account of the non-serious adverse event recorded in the safety summary.

Finally, the registry lists planning assumptions involving two-arm equal allocation, while the registered design is single-group. No planning illustration values or explanation of this mismatch are reported in the registry record. These issues limit interpretation of both the study’s intended statistical design and its observed results.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Using Fostamatinib to Treat Post-Hematopoietic Stem Cell Transplant Immune-mediated Cytopenias — NCT05502783.
• Registry record last updated 2025-12-05; status last verified 2025-10.
• Results first posted 2025-12-05.
• 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.

19. Record Summary

NCT05502783 is a phase II, single-group, unmasked study of fostamatinib for immune-mediated cytopenias after hematopoietic stem cell transplant. The registry lists enrollment of 1 participant, a start date of 2023-03-10, a primary completion date of 2023-06-16, and terminated status.

The primary endpoint was the number of participants able to maintain hematologic recovery, assessed from Baseline through Week 10 under a definition based on repeated readings and recent transfusion support. The registry does not report the primary outcome count or any analyses. It records that one participant withdrew at week 10 due to lack of efficacy and that no data was collected up to week 12.

The adverse-event summary records 0 participants with serious adverse events, 1 participant with other adverse events, and 0 deaths. Further detail about the other adverse event is not reported in the registry record. The design, enrollment, and missing outcome results do not support an estimate of treatment effect or a comparative conclusion.