A Proof of Concept Pilot Trial of Alpha-1-Antitrypsin for Pre-Emption Of Steroid-Refractory Acute GVHD: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Proof of Concept Pilot Trial of Alpha-1-Antitrypsin for Pre-Emption Of Steroid-Refractory Acute GVHD (NCT03459040), a na phase 2 study. The primary outcome is Number of High Risk Patients Who Develop Steroid Refractory GVHD.

2. Clinical Question

3. Trial Design

This was a completed Phase 2 proof-of-concept pilot trial of AAT for pre-emption of steroid-refractory acute GVHD. It used a single-group design, with no random allocation and no masking. Enrollment was 30. The registry lists the study start as 2018-08-17 and primary completion as 2020-08-21.

The treatment strategy began with blood testing after transplant to identify patients considered at high risk for severe GVHD. Testing could take place at one week and two weeks after bone marrow transplant. High-risk patients were to receive AAT: 16 doses through a catheter over eight weeks, administered two times per week in hospital or an outpatient clinic. The registry does not report how many participants were classified as high risk or how many received the full treatment course.

The primary endpoint was the number of high-risk patients who developed steroid-refractory GVHD by Day 100 after hematopoietic cell transplant. The registry also lists outcomes concerning survival, non-relapse mortality, relapse, GVHD severity and response, chronic GVHD requiring systemic steroid treatment, and serious infections. Numerical results for these outcomes are not reported in the registry record.

Follow-up for severe GVHD was described as extending up to four months from transplant, with routine clinic follow-up continuing for up to one year. This is a descriptive account of the planned study structure; the registry record does not report participant flow, adherence, or the completeness of follow-up. With no concurrent control group, the design can describe outcomes among participants in the study but cannot isolate the effect of AAT from other influences.

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:

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 High Risk Patients Who Develop Steroid Refractory GVHD, measured over Day 100 post HCT..

The primary endpoint counts high-risk patients who developed steroid-refractory GVHD by Day 100 after hematopoietic cell transplant. It is a participant count, not a measure of how severe each case was or how long it lasted. The registry’s definition classifies GVHD as steroid-refractory if a participant did not achieve complete or partial response by day 28 of systemic steroid treatment, or if additional immunosuppression beyond steroids was given for GVHD before 28 days of steroid treatment.

Complete response requires all evaluable organs—skin, liver, and gastrointestinal tract—to be at stage 0. Partial response means improvement in at least one organ involved with GVHD symptoms without worsening in other organs. For either response to count on day 28, the patient must be in that response state on that day and must not have received intervening additional GVHD therapy.

As a general statistical rationale, a defined endpoint can translate a clinical question into an outcome that can be counted consistently across participants. The day-100 time point sets the period in which the event is assessed, while the response criteria specify what qualifies as steroid-refractory disease. The registry record does not report the observed count, the denominator used for the primary analysis, or an estimate of uncertainty around the result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count convey?

The primary outcome is a count of participants meeting a defined event criterion. Counts are useful because they are directly interpretable: they state how many people experienced the endpoint. But a count alone is incomplete. Its interpretation depends on the population at risk, the analysis denominator, the observation period, and whether all eligible participants had outcome information. In this study, the endpoint is framed among high-risk patients by Day 100 after transplant. The registry record does not report the numerical endpoint result or the number of high-risk patients used as its denominator.

As a general statistical concept, an event proportion pairs the number of participants with the event with the number assessed. An interval estimate, such as a confidence interval, communicates uncertainty around an estimate rather than treating a sample result as exact. It can help readers understand how compatible the data are with a range of underlying event frequencies. No primary endpoint proportion or confidence interval is reported in the registry record, so none can be interpreted for this trial.

Why does the design matter?

This is a single-group study without random allocation or masking. A single-group result can describe what happened among those observed under the study strategy. It does not create a concurrent estimate of outcomes under an alternative strategy. General causal interpretation requires a credible comparison that accounts for differences between groups; randomization is one way to make those groups comparable on average. Since this trial has no randomized comparison, its design does not separate an AAT effect from other factors that may influence GVHD or its treatment.

The intervention also follows a risk-identification step. Participants were to have blood testing after transplant, and those judged high risk were to receive AAT. Interpretation therefore depends on who was tested, who met the high-risk definition, and who proceeded to treatment. The record describes the testing schedule and treatment course but does not report the numbers at each step. It also does not report how risk status was operationalized beyond the general description of the blood test.

What is the role of the endpoint definition?

Clear outcome rules can improve consistency in deciding whether an event occurred. Here, the definition combines response status at day 28 of systemic steroid treatment with whether additional immunosuppression was given before 28 days. Complete and partial response are defined using organ involvement and the absence of intervening additional GVHD therapy. These criteria help specify what is counted, but they do not reveal the observed result. The record does not report how endpoint assessments were conducted, whether they were independently reviewed, or how ambiguous or unavailable assessments were adjudicated.

The endpoint also depends on clinical events and treatment decisions. A participant may meet the definition through lack of complete or partial response, or through additional immunosuppression before the specified time. As a general methodological point, an endpoint that includes a treatment decision can reflect both disease status and clinician decisions. The registry record does not report whether treatment decisions followed a standardized protocol or how variation in practice was addressed.

How should statistical uncertainty be approached?

For a binary event outcome, methods commonly estimate an event frequency and its uncertainty, with the choice of method depending on the design, denominator, and data structure. A confidence interval is not a guarantee that the true value lies within its limits; rather, it expresses the uncertainty associated with an estimate under the method’s assumptions. When samples are limited, estimates can be imprecise, and a count can be compatible with a broad range of underlying event rates. No trial-specific interval or model result is reported in the registry record, so the degree of uncertainty cannot be quantified from the posted primary outcome information.

Statistical testing is not a substitute for design. A small p-value, if one had been reported, would not by itself resolve the absence of a control group or establish causation. Likewise, a non-significant result would not demonstrate equivalence or absence of an effect. The registry record lists zero analyses and does not report a hypothesis test, model, adjustment strategy, or inferential result for the primary endpoint.

The record describes sample-size assumptions for planning illustrations, including a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Those assumptions are not a description of the actual single-group trial design. A planning illustration is not evidence of observed power, and the registry record does not report the trial’s own sample-size justification. An illustration based on a hypothetical two-arm comparison cannot be interpreted as a trial result or as proof that the single-group study was adequately powered.

What can safety summaries establish?

Safety counts describe participants recorded with adverse events, but they are not automatically measures of treatment-attributable risk. General safety interpretation considers the observation period, event definitions, severity, timing, exposure, and whether events could occur as part of the underlying disease or transplant course. The registry lists participants at risk and affected for serious and other adverse events, along with deaths and selected serious-event terms. It does not report a comparative safety analysis or causal attribution for these summaries.

Multiple event terms may represent different clinical descriptions, and a participant may experience more than one event. The record does not explain whether listed terms overlap at the participant level, how event coding was performed, or whether all events were included in the displayed term list. Therefore, term percentages should be read as the registry’s reported summaries, not combined or treated as mutually exclusive categories.

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("Alpha-1-antitrypsin (AAT)")
n      <- c(30)
events <- c(6)
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  Alpha-1-antitrypsin (AAT)  30  6  20.0  7.7  38.6  9.5  37.3  9.6  37.5

11. Multiplicity, Missing Data and Analysis Populations

The registry lists several secondary outcomes in addition to the primary endpoint. They cover survival at 6 months and 1 year, non-relapse mortality, relapse, clinically relevant GVHD states including Grade II-IV GVHD, overall response, severe gastrointestinal GVHD at stage 3 or 4, chronic GVHD requiring systemic steroid treatment, and serious infections. The record reports 9 outcome measures, but numerical results for these listed outcomes are not reported in the registry record.

When a study considers multiple outcomes, repeated comparisons can increase the chance of finding an apparently notable result by chance. General approaches include identifying a primary endpoint in advance, specifying a hierarchy of outcomes, or applying a multiplicity adjustment. The record identifies a primary endpoint but does not report a statistical analysis plan, a testing hierarchy, or a multiplicity adjustment. It therefore does not establish how any secondary outcome analyses would have been interpreted relative to one another.

The registry lists zero analyses. Analysis populations are not reported in the registry record: it does not specify whether the primary endpoint was assessed among all enrolled participants, only those classified as high risk, those who received AAT, or another defined group. The number with missing primary outcome information and the method used to handle missing data are also not reported. It is not possible to assess whether missingness could have affected the endpoint estimate or whether follow-up differed among participants.

The record describes follow-up for severe GVHD through up to four months from transplant and routine clinic follow-up for up to one year. It does not report the amount of follow-up actually completed, losses to follow-up, or how participants without an observed endpoint by Day 100 were treated in an analysis. These omissions limit assessment of the completeness and interpretability of both primary and secondary outcome data.

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 serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: gvhd (13.3%), bronchopulmonary hemorrhage (dah) (6.7%), pneumonitis (6.7%), pulmonary edema (6.7%), relapse (6.7%).

For the AAT group, the registry lists 30 participants at risk for serious adverse events and 14 affected. It also lists 30 at risk for other adverse events and 9 affected. The record separately reports 8 deaths. These are registry counts; they do not establish that AAT caused the events or deaths. The record does not report a causal assessment, event timing, or a comparison with an untreated group.

The serious-event terms listed include GVHD (13.3%), bronchopulmonary hemorrhage (DAH) (6.7%), pneumonitis (6.7%), pulmonary edema (6.7%), relapse (6.7%), and engraftment syndrome (3.3%). The percentages should be read as posted, without converting them into counts or combining them. The registry record does not explain whether participants could appear under more than one term, whether these are all serious-event terms, or how the percentages were calculated.

Adverse-event summaries are distinct from the primary endpoint, which concerns steroid-refractory GVHD by Day 100. They also do not provide a comparison of risk between treatment strategies. Interpretation is limited by the absence of reported event-level timing, exposure details, and causal attribution in the registry record.

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

This trial asks a focused proof-of-concept question: among patients judged at high risk after transplant, how many developed steroid-refractory GVHD by Day 100 after receiving the AAT strategy? The registry provides the endpoint definition and describes the planned screening, treatment, and follow-up. It does not report the numerical primary endpoint result, so the outcome cannot be characterized as frequent or infrequent on the basis of this record.

The design matters to what can be concluded. Because the trial is single-group and has no concurrent control, any observed outcomes would describe participants in this study rather than establish what AAT changed relative to another strategy. The registry record also does not report the number of high-risk participants, the primary endpoint denominator, or a statistical analysis. Those gaps prevent a precise estimate of the primary outcome from the posted information.

The recorded adverse-event summaries give counts and selected event terms, but they do not establish that the events were caused by AAT. Without comparative safety data and reported causal assessment, the listed events should be treated as descriptive safety information rather than estimates of excess risk due to treatment.

More generally, absence of a reported result is not evidence that no event occurred, and absence of a reported statistical test is not evidence for or against an effect. The registry record supports understanding the study’s question and design, but not a conclusion about whether AAT prevented steroid-refractory GVHD or altered safety outcomes. Such a conclusion would require interpretable outcome results, denominators, and an appropriate basis for comparison.

14. Why This Trial Matters Statistically

This pilot is statistically informative as an example of how a clinical question, a risk-identification step, and an endpoint definition fit together. The study does not enroll an unselected transplant population for the stated primary question: AAT is directed to patients identified as high risk by blood testing. That makes the high-risk classification and the number of patients entering treatment important parts of the interpretation, not merely administrative details.

The primary endpoint is operationally defined by both response to systemic steroids and use of additional immunosuppression. That definition makes clear which clinical events count, while also drawing attention to how assessment and treatment decisions may influence endpoint classification. The record’s description allows readers to understand the intended outcome even though it does not report its observed value.

The single-group design is central to the statistical lesson. Descriptive event counts can characterize what occurred in the enrolled group, but a treatment effect requires a credible comparison. The registry record reports no primary outcome analysis or numerical result, so it cannot support an estimate of treatment effect. The safety counts similarly describe recorded events without establishing causation.

The record also illustrates why enrollment alone is not enough to judge a study’s precision. The number enrolled is 30, but the number classified as high risk and the denominator for the primary endpoint are not reported. Without those quantities and an outcome estimate, readers cannot assess the uncertainty around the result. A clearly stated endpoint is valuable, but the endpoint result, analysis population, and missing-data information are needed to interpret the evidence.

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.

The most immediate limitation for interpretation is that the registry record does not report a numerical result for the primary endpoint. It also does not report an estimate of uncertainty, a p-value, or an analysis model. The primary question is therefore defined but not answerable from the posted outcome information.

The single-group design has no concurrent comparator, and allocation is listed as not applicable. Outcomes cannot be attributed to AAT by comparing this group with a randomized alternative. The registry also does not report participant characteristics or details sufficient to assess how representative the enrolled group was of other transplant patients.

Although enrollment was 30, the number of participants identified as high risk, treated, and included in the endpoint analysis is not reported. The record does not give participant flow, treatment completion, outcome availability, losses to follow-up, or missing-data handling. These omissions prevent assessment of the denominator and whether incomplete follow-up could influence interpretation.

The blood test’s operating characteristics and the criteria used to classify patients as high risk are not reported in the registry record. Details of endpoint assessment, including review procedures and handling of uncertain classifications, are also not reported. The record does not state how concomitant or additional treatments were managed beyond the endpoint definition’s reference to additional immunosuppression.

Finally, a statistical analysis plan, analysis populations, and multiplicity procedures are not reported. Safety summaries lack reported causal attribution and a comparative group. These limitations concern what can be learned from the registry record; they do not establish that unreported procedures or analyses were absent from study conduct.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Proof of Concept Pilot Trial of Alpha-1-Antitrypsin for Pre-Emption Of Steroid-Refractory Acute GVHD — NCT03459040.
• Registry record last updated 2021-07-12; status last verified 2021-06.
• Results first posted 2021-05-24.
• 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

NCT03459040 is a completed Phase 2, single-group pilot trial of alpha-1-antitrypsin for pre-emption of steroid-refractory acute GVHD. Enrollment was 30. Participants identified as high risk after blood testing following transplant were to receive 16 AAT doses over eight weeks. The primary endpoint was the count of high-risk patients who developed steroid-refractory GVHD by Day 100 after hematopoietic cell transplant.

The registry record does not report a numerical primary endpoint result, a primary analysis, or analysis populations. It lists 14 participants affected by serious adverse events, 9 affected by other adverse events, and 8 deaths in the AAT group, with 30 at risk for each adverse-event listing. Selected serious-event terms and percentages are also recorded. The single-group design and absence of a reported primary result limit conclusions about treatment effect.