Abatacept in Treating Adults With Mild Relapsing Wegener's Granulomatosis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Abatacept in Treating Adults With Mild Relapsing Wegener's Granulomatosis (NCT00468208), a na phase 1, phase 2 study. The primary outcome is Safety of Abatacept - Number of Participants With Adverse Events.

2. Clinical Question

The central question is about safety in a pilot setting, rather than whether abatacept performs better than another treatment. The record says the study examined adverse events continuously from screening through the six-month post-treatment visit, with the timeframe extending up to 3 years and 4 months. It identified infection, infusion reactions, cytopenias, transaminase elevation, skin reactions, gastrointestinal side effects, and malignancy as specific events for analysis, while making all adverse events reportable.

Because there is no control group, any adverse events recorded during follow-up cannot be compared within this trial against an untreated or alternative-treatment group. The record lists disease-related secondary outcomes, but their results and the methods used to analyze them are not reported in the registry record. Consequently, the posted information addresses the occurrence of adverse events in this group but does not establish a comparative estimate of safety or efficacy.

3. Trial Design

This was a completed, multicenter, open-label pilot study, listed as Phase 1 and Phase 2. The sponsor was the University of Pennsylvania. The study began in 2008-02, had primary completion in 2011-08, and enrolled 20 participants. The registry classifies the design as single-group, with allocation not applicable and no masking.

Participants received abatacept intravenously at study visits on Days 1, 15, and 29, then once a month thereafter. The record does not describe a parallel control arm, random assignment, or blinded assessment. The absence of a comparator is central to interpreting the results: the group’s event counts are descriptive, not a treatment contrast.

The stated purpose was to examine safety and explore a preliminary efficacy signal in WG. The registry says the sample size of 20 was considered sufficient to begin pilot explorations. It does not report a formal sample-size justification based on a target effect, precision, or statistical power. A distinct sample-size planning illustration may be useful for considering hypothetical future research, but it is not the design used to enroll participants in this single-group trial.

The primary endpoint was the number of participants with adverse events. The registry also lists secondary outcomes of disease remission, disease improvement, meeting common closing, and disease relapse. It identifies five outcome measures overall, but the outcome analyses are not reported in the registry record. The record’s primary-completion date and completed status describe the study’s administrative progress; they do not, on their own, establish that each planned outcome was fully observed or analyzed.

Follow-up for the primary safety endpoint was described as continuous from screening through the six-month post-treatment visit, with the overall timeframe extending up to 3 years and 4 months. The registry does not report participant-level follow-up duration, visit adherence, or the number of participants contributing data at each time point. Those details would help clarify how much observation contributed to the counts.

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: At a screening visit, participants underwent procedures to establish inclusion/exclusion criteria and then signed the informed consent form.

Overall Study

Analysis population for the primary outcome, as defined in the registry: This study intended to examine safety and to explore preliminary signal for efficacy of abatacept in Wegener's granulomatosis. The sample size of 20 was based upon a sufficient number of subjects to begin such pilot explorations.

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 Safety of Abatacept - Number of Participants With Adverse Events, measured over Measured continuously from the screening visit through to the 6 month post-treatment study visit, up to 3 years and 4 months..

The primary endpoint is the number of participants with adverse events. It is a count of people who experienced an event, rather than a count of all event occurrences or a measure of event severity. The registry describes continuous safety monitoring from screening through the six-month post-treatment visit, for a timeframe extending up to 3 years and 4 months.

This endpoint is relevant to a pilot study whose stated purpose includes examining safety. The record says all adverse events were reportable and highlights infection, infusion reactions, cytopenias, transaminase elevation, skin reactions, gastrointestinal side effects, and malignancy as specific events for analysis. Capturing the number of affected participants gives a straightforward description of how many people in the study had events during observation.

However, a participant count alone does not describe how many events each person experienced, how long events lasted, their severity, or whether they led to changes in treatment. Those details are not reported in the registry record. Nor does a single-group count distinguish events associated with the underlying disease or other circumstances from events attributable to treatment. Without a comparator, the endpoint is descriptive evidence about observed participants, not a comparative estimate of treatment-related risk.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count represent?

The primary endpoint is a binary outcome at the participant level: a person either had at least one adverse event during the specified observation period or did not. The posted result is expressed as the number of participants with an event, alongside the number at risk. This is different from counting every event episode. One person could have more than one event, but a participant count would still count that person once for the endpoint. The registry does not provide event-level totals or participant-level records, so those details cannot be reconstructed from the posted counts.

General statistical explanation: binary outcomes are often summarized by counts and proportions. A proportion describes the share of observed participants with the outcome, while an interval estimate can convey uncertainty around that observed proportion. No confidence interval is reported for this endpoint in the registry record. A point estimate alone does not show how much the result might vary across other samples of similar participants.

Why does the single-group design matter?

The study has one open-label group and no separate comparator. Its adverse-event counts therefore describe events observed during abatacept treatment and follow-up, but do not estimate a contrast between treatments. In a comparative trial, a treatment contrast would depend on both groups and the planned analysis. Those ingredients are absent. Differences from other studies or populations cannot be attributed to abatacept on the basis of this registry record, because populations, observation periods, and event ascertainment may differ.

Open-label describes the absence of masking. General statistical explanation: when treatment and study participation are known, expectations and awareness can influence reporting or assessment, particularly for outcomes requiring judgment. The registry does not report blinded outcome assessment or another process intended to address that possibility. This limitation does not mean that reported events are invalid; it means interpretation should account for how the design could affect what is reported and classified.

How should event categories be read?

The registry separates serious adverse events from other adverse events and gives participant counts for both categories. These categories should be kept distinct when describing the posted results. The record also lists selected serious adverse event terms with percentages. It does not explain in the posted information whether a participant could contribute to more than one term, or how the listed terms relate to all serious events. Thus, term-specific percentages should not be added together or treated as mutually exclusive categories.

General statistical explanation: adverse-event profiles can include both the number of affected people and the number, type, timing, and severity of events. Counts of affected participants are easy to interpret, but do not capture all those dimensions. Exposure time can also matter when observation periods vary. The registry describes a safety timeframe extending up to 3 years and 4 months, but does not report participant-specific exposure time or follow-up duration. A rate accounting for person-time cannot be derived from the posted information.

What do the planning illustrations mean?

The accompanying planning illustrations are hypothetical calculations, not analyses conducted as part of the trial. Their stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. They are not the study’s original design, which was single-group, and they are not observed power. They should be read only as planning scenarios for a hypothetical comparison, not as evidence that the trial had a particular probability of detecting an effect.

General statistical explanation: sample-size planning depends on the outcome, the effect a future study aims to detect, variability, allocation, and the chosen error-rate assumptions. A planning result is conditional on those assumptions. If the assumed effect is uncertain, the resulting sample-size illustration is uncertain too. It does not change the precision of the results already observed in this pilot.

What analysis details are unavailable?

The registry record lists five outcome measures and no analyses. It does not report model specifications, adjustment variables, missing-data handling, analysis populations, confidence intervals, or hypothesis tests. Without these details, readers cannot determine whether reported results were based on all enrolled participants, a subset, or a prespecified analysis population. They also cannot evaluate any adjustment for multiple outcomes or the handling of incomplete follow-up. These are unreported analysis details, not evidence that a particular method was or was not used outside the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures, including the primary safety endpoint and secondary disease outcomes, and lists no analyses. It does not report a multiplicity plan, such as whether or how interpretation of several outcomes was adjusted. General statistical explanation: when multiple outcomes are examined, the chance of finding an apparently notable result by chance can increase, depending on the analysis strategy. A prespecified hierarchy or other approach may address this concern, but the registry record does not state whether such a plan was used. Since disease outcome results are not reported, their multiplicity cannot be evaluated from this record.

Missing-data methods are not reported in the registry record. The safety endpoint is described as monitored continuously from screening through the six-month post-treatment visit, with a timeframe up to 3 years and 4 months, but the record does not give the number of participants with complete follow-up or explain how incomplete observations were treated. It also does not report participant-level follow-up or reasons for missing data. General statistical explanation: missing observations can affect interpretation when the likelihood of missingness is related to health status, treatment, or the outcome. The direction and size of any such effect cannot be determined without further information.

The analysis populations are not reported in the registry record. It is therefore unclear which participants contributed to each outcome analysis, beyond the posted adverse-event counts and their at-risk denominators. The record does not describe exclusions, protocol deviations, or how participants who discontinued were handled. No specific approach should be inferred from the absence of these details. These reporting gaps limit assessment of the completeness and reproducibility of the outcome analyses.

11. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: infection - ocular (10.0%), infection - dental (5.0%), infection - lung (5.0%), infection - upper airway (5.0%), infection - gastrointestinal (5.0%).

The posted results report 7 participants with serious adverse events among 20 at risk, and 16 participants with other adverse events among 20 at risk. These figures refer to participants who experienced events, not the total number of event episodes. The registry separately lists serious adverse event terms with percentages: Infection - Ocular, 10.0%; Infection - Dental, 5.0%; Infection - Lung, 5.0%; Infection - Upper airway, 5.0%; Infection - Gastrointestinal, 5.0%; and Obstruction/stenosis of airway, 5.0%.

These term-specific figures should not be read as mutually exclusive categories or combined into a total. The registry does not report whether the same participant contributed to more than one listed term, nor does it provide detailed timing, severity beyond the serious classification, attribution, or outcome for each event. Deaths are not reported in the registry record.

Because the study has no comparator, these counts do not establish how event occurrence compares with another treatment or with no treatment. They describe the posted observations in this group during the reported safety follow-up. The record’s timeframe extends up to 3 years and 4 months, but participant-specific observation time is not reported, which limits interpretation of the counts as rates.

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

The results do show that adverse events were recorded among participants in this open-label abatacept group: the registry reports 7 participants with serious adverse events and 16 with other adverse events, each among 20 at risk. It also identifies selected serious event terms and their reported percentages. These are descriptive safety findings for the participants and observation described in the registry record.

They do not show how those counts compare with a control group, because the trial was single-group and had no comparator. The figures alone do not establish that abatacept caused any particular event, nor do they establish how event occurrence would differ under another treatment or without treatment. The registry does not report detailed event attribution, timing, recurrence, or participant-level follow-up, all of which would inform a fuller interpretation.

The study’s stated purpose also included exploring a preliminary efficacy signal, and disease remission, disease improvement, meeting common closing, and disease relapse are listed as secondary outcomes. Their results are not reported in the registry record. As a result, this record does not support conclusions about those disease outcomes or a comparative treatment effect. The completed status of the study does not substitute for missing outcome results or analysis details.

General statistical explanation: a pilot study can help describe observed events and guide questions for subsequent research, but a small uncontrolled study generally has limited ability to separate treatment effects from chance variation, underlying disease, or other influences. Here, the stated enrollment was 20, and the record says this was considered sufficient to begin pilot explorations. That rationale should not be read as proof of precise estimates or a definitive test.

The most defensible conclusion is limited to what the record reports: participant counts for adverse events in a single open-label group, with no comparative efficacy analysis reported. Any broader inference would require information that is not reported in the registry record, including outcome results, analysis methods, missing-data handling, and a suitable comparison.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between a descriptive pilot study and a comparative efficacy study. Its single-group, open-label design can document adverse events observed during treatment and follow-up, but it does not estimate a between-group effect. That distinction is essential when interpreting any event count: a count is a description of the study group, not a comparative measure of treatment-related risk.

The registry states that enrollment of 20 was intended to provide a sufficient number of participants to begin pilot explorations. That is a development-stage rationale, not a claim of definitive precision or hypothesis-testing capacity. Pilot studies can identify practical and measurement questions, and can inform planning, while still leaving uncertainty about event frequency and treatment effects.

The record also illustrates why registered outcomes and posted results must be distinguished. Several disease outcomes are listed, but their findings and analyses are not reported. Without those results, readers cannot assess the preliminary efficacy aim. Likewise, the absence of reported confidence intervals, analysis populations, and missing-data methods limits a statistical appraisal of the primary safety endpoint beyond its posted counts.

Finally, planning calculations for a hypothetical two-arm study should not be confused with the design or evidential strength of this trial. They address prospective design assumptions; they do not turn a one-group pilot into a randomized comparison or quantify observed power. This distinction is useful whenever planning illustrations accompany results from a study whose actual design is different.

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.

Several limitations specific to this trial shape interpretation. It was a single-group, open-label study with no comparator, so the adverse-event counts are not a relative comparison. The design cannot separate events associated with treatment from events related to WG, other circumstances, or background occurrence. Lack of masking can also affect event reporting or assessment, although the registry does not describe how much this occurred.

The study enrolled 20 participants and was described as a pilot intended to begin safety and efficacy exploration. The posted counts may therefore be imprecise descriptions of the event experience beyond this group. The registry does not report confidence intervals or other uncertainty estimates for the primary outcome. It also does not give participant-level follow-up duration, despite a safety timeframe extending up to 3 years and 4 months; variation in observation time cannot be assessed from the posted information.

Event detail is limited. The record reports counts of participants with serious and other adverse events and lists selected serious event terms with percentages, but does not report event-level counts, timing, duration, severity detail beyond classification, attribution, recurrence, or whether terms overlap within participants. Deaths are not reported in the registry record. These omissions constrain a fuller safety profile.

The listed secondary disease outcomes have no results or analyses reported in the registry record. Analysis populations, missing-data handling, protocol deviations, statistical methods, and multiplicity procedures are also not reported. Accordingly, the record cannot support conclusions about disease outcomes, the handling of incomplete observations, or the robustness of any unreported analysis. These are limits of the available registry information, not proof that the study team did not collect or analyze such information elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Abatacept in Treating Adults With Mild Relapsing Wegener's Granulomatosis — NCT00468208.
• Registry record last updated 2016-01-18; status last verified 2015-12.
• Results first posted 2013-11-26.
• 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.

18. Record Summary

NCT00468208 is a completed, multicenter, open-label pilot study of abatacept in adults with mild relapsing Wegener's granulomatosis. It is listed as Phase 1 and Phase 2, single-group, with no masking and allocation not applicable. The University of Pennsylvania was the sponsor. The study began in 2008-02, had primary completion in 2011-08, and enrolled 20 participants.

Abatacept was given intravenously on Days 1, 15, and 29, then monthly. The primary endpoint was the number of participants with adverse events, monitored from screening through the six-month post-treatment visit, for a timeframe up to 3 years and 4 months. The posted results report 7 participants with serious adverse events and 16 with other adverse events among 20 at risk. Disease outcome results and statistical analyses are not reported in the registry record. With no comparator, the safety counts are descriptive rather than comparative.