A Study Evaluating the Effect of Filgotinib Dose De-escalation in Participants With Ulcerative Colitis (UC) in Remission: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study Evaluating the Effect of Filgotinib Dose De-escalation in Participants With Ulcerative Colitis (UC) in Remission (NCT05479058), a randomized phase 3 study. The primary outcome is Percentage of Participants in Corticosteroid-free Clinical Remission Based on Modified Mayo Clinical Score (mMCS).

2. Clinical Question

The central statistical question was whether the planned dose reduction was associated with a different rate of corticosteroid-free clinical remission than continuing the 200 mg dose. This was a comparison between two assigned dose strategies in participants already in remission, not a study of starting filgotinib or treating active disease.

The registry record says the study was terminated before any participant reached the primary analysis time point. It also says the primary endpoint data were not collected and analyzed. Consequently, the planned question cannot be answered from the posted primary results: there is no Week 48 percentage for either group and no estimate of the difference between them. The record does not report a reason for termination.

3. Trial Design

NCT05479058 was registered as a phase 3, randomized, double-blind, controlled, multicenter, parallel-group study. Its stated purpose was to evaluate the efficacy and safety of reducing orally administered filgotinib among participants with ulcerative colitis in clinical remission. The registry lists an enrollment of 22 and a status of terminated.

The intended study population consisted of participants in stable clinical remission on filgotinib 200 mg once daily in the ongoing SELECTION-LTE study. The plan was for eligible participants to roll over and be randomized. One group was assigned filgotinib 200 mg with matching placebo; the other was assigned filgotinib 100 mg with matching placebo. This matching design was intended to keep the treatment assignments masked. The registry describes masking as quadruple, but does not specify in the record which roles were masked.

The primary endpoint was planned for Week 48. The registry also lists secondary outcomes concerning time to PRO2 flare, time to endoscopist-confirmed UC flare, changes in CRP, FCP, and IBDQ scores, and treatment-emergent adverse events, including serious events and events leading to treatment discontinuation. Although these outcomes are named, the record does not provide analyzed results for them.

The study ended before any participant reached the Week 48 primary analysis time point. The record does not report the reason for termination, the timing of termination relative to each participant’s enrollment, or details of any interim review. It lists 11 participants at risk in each group for the adverse-event summaries. Those safety counts do not substitute for the missing primary endpoint comparison.

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: The clinical trial was originally designed with the primary endpoint to be assessed at Week 48 after which participants would have received unblinded treatment. Due to early termination of the study, none of the participants completed 48 weeks of treatment. All participants participated in blinded treatment period only and the study was unblinded globally after study completion.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: As the study was terminated prior to any participant reaching the primary analysis time point at Week 48, the data for this endpoint was not collected and analyzed.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: Safety Analysis Set included all randomized participants who were administered study drug at least once.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants in Corticosteroid-free Clinical Remission Based on Modified Mayo Clinical Score (mMCS), measured over Week 48.

The primary endpoint was the percentage of participants in corticosteroid-free clinical remission at Week 48, assessed with the modified Mayo Clinical Score (mMCS). The mMCS measures ulcerative colitis disease activity using stool frequency, rectal bleeding, and endoscopy subscores. Each subscore ranges from 0 to 3, and higher values indicate more severe disease activity; the total score ranges from 0 to 9.

Remission was defined as a total mMCS score no more than 2, an endoscopic subscore no more than 1, a stool frequency subscore no more than 1, and a rectal bleeding subscore of 0. Corticosteroid-free remission additionally required being free of corticosteroids for at least 12 weeks.

This endpoint combines clinical symptoms, an endoscopic assessment, and freedom from corticosteroid use over a specified period. A percentage in remission would describe how many participants in each assigned group met the full definition at the planned assessment time. Comparing those percentages would address the study’s dose-de-escalation question. The registry states that termination occurred before any participant reached Week 48; therefore, endpoint data were not collected or analyzed, and no group percentages or comparison are available.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The design described in the registry is a randomized, double-blind, controlled, parallel-group comparison. In general, random assignment is used to make treatment groups comparable, on average, with respect to both measured and unmeasured characteristics. Masking can reduce the influence of treatment knowledge on participant reports, clinical care, and outcome assessment. These design features describe how a study is intended to support a comparison; they do not create an estimate when the outcome is not observed.

Participants were to enter the study while in clinical remission on filgotinib 200 mg once daily in the ongoing SELECTION-LTE study. The planned randomized strategies were continuation of 200 mg once daily or reduction to 100 mg once daily. Placebo matching was described for each assignment. Because the registry reports termination before anyone reached Week 48, it is not possible to assess how the randomized groups compared on the primary endpoint.

What the primary endpoint would estimate

The endpoint was a binary status at Week 48: whether a participant met the complete corticosteroid-free mMCS remission definition. A group percentage would represent the proportion meeting that definition among the relevant analysis population. A treatment contrast could then express how those group outcomes differed. No such values are reported in the registry record, so no effect estimate can be interpreted.

In general, a confidence interval around a treatment contrast conveys uncertainty due to the observed data and the analysis method. A narrow interval indicates greater statistical precision than a wide interval, while the interval’s position relative to a null value is relevant to how the data relate to a no-difference hypothesis. Here, no primary treatment contrast or interval is reported. Thus neither statistical significance nor the range of plausible effects can be assessed from the primary endpoint.

Why the design label is not a result

Randomization and masking are methodological protections, not evidence that a treatment effect was observed. A randomized trial can be well structured in principle but still fail to answer its planned question if the outcome measurements needed for analysis are not obtained. The registry explicitly states that the primary endpoint data were not collected and analyzed because the study ended before the primary analysis time point.

The record identifies the study as phase 3 and lists an enrollment of 22. It does not report a sample-size justification or a statistical analysis plan. In general, a planned sample size is selected to balance the intended precision or ability to detect a specified effect against practical constraints. Without the trial’s own justification and planned analysis details, the enrollment figure alone does not show what effect size the study was designed to detect or whether the design would have provided adequate precision.

Interpreting the safety counts

For each assigned group, the adverse-event summary lists 11 participants at risk for serious events and 11 at risk for other events. No participants are listed as affected by serious events, while 6 are listed as affected by other events. No deaths are listed. These are descriptive counts in the posted record. They do not provide event-level detail or an adjusted comparison, and they should not be used to infer equal risks. General comparisons of rare or uncommon events can be especially uncertain when the number of observed events is small.

Over-dispersion and count outcomes

General statistical note: for outcomes recorded as counts, a simple model may assume that the variability in counts follows a particular relationship to the average count. Over-dispersion occurs when the observed variability is larger than that assumption allows. Ignoring it can make uncertainty estimates too small. This concept may be relevant to count-based outcomes in clinical research, but the registry record does not identify a count model or report an analysis for the listed outcomes. No conclusion about over-dispersion in this trial is possible.

Planning illustrations and observed evidence

General statistical note: sample-size or power calculations are planning exercises tied to assumptions about an effect, variability, allocation, and testing procedure. They are not observed power and cannot replace an analysis of collected outcomes. The registry record does not report the trial’s own sample-size justification, and it contains no primary endpoint estimate from which to interpret a Week 48 effect. Any planning illustration should therefore be kept distinct from evidence about what happened to participants in this study.

Overall, the main methodological fact for interpretation is the absence of the planned Week 48 endpoint data. The registry describes an appropriate randomized comparison as the intended design, but it does not provide the observations and analyses needed to quantify the primary effect or its uncertainty.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint and several secondary outcomes. In general, testing multiple outcomes or multiple time points can increase the chance of obtaining at least one apparently notable result by chance. Statistical plans may address this through a prespecified hierarchy, an adjustment procedure, or a clearly descriptive approach. The registry record does not report whether any multiplicity procedure was planned or used. Since no analyses are reported, there are no outcome-specific test results to interpret in light of multiplicity.

The record says the primary endpoint was not collected and analyzed because the study ended before any participant reached Week 48. It does not report the amount or pattern of missing data for other outcomes, whether any participants had partial follow-up, or how missing observations would have been handled. Those details are not reported in the registry record. In general, missing-data methods rely on assumptions about why values are absent; different assumptions can affect estimated treatment comparisons.

The record also does not specify the analysis populations, such as which participants would have been included in the primary analysis or how deviations from assigned treatment would have been handled. The randomized design is described, but the analysis-set definitions and statistical plan are not reported. No interim analysis details are reported either. Without these items and without outcome analyses, there is no basis for assessing the planned handling of multiplicity, missingness, or analysis populations.

11. 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 adverse-event summary lists 11 participants at risk in the Filgotinib 200 mg group and 11 in the Filgotinib 100 mg group. No participant in either group is listed as affected by a serious adverse event. The summary lists 6 participants affected by other adverse events in each group. It also lists no deaths. The registry does not provide top serious-event terms.

These counts are descriptive, and the record does not give event-level detail, timing, duration, severity beyond the serious/other distinction, or an adjusted comparison. Matching counts do not establish that the groups had identical safety profiles: different event types or patterns could be hidden within an aggregate count, and the record does not provide that detail. Nor do zero listed serious events establish that serious events could not occur. The study ended before the primary analysis time point, and the available safety entries do not replace longer-term or complete safety follow-up information that is not reported in the registry record.

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

The record establishes that NCT05479058 was intended to compare continuing filgotinib 200 mg once daily with reducing the dose to 100 mg once daily among participants already in clinical remission. It also establishes that the study was terminated before any participant reached the planned Week 48 primary analysis time point. The primary endpoint data were not collected and analyzed.

Accordingly, the posted record does not show whether the proportion in corticosteroid-free mMCS remission differed between the assigned groups. It does not provide an effect estimate, a confidence interval, or a primary statistical test. The absence of a result cannot be interpreted as evidence of equivalence, lack of effect, or benefit of either dose strategy.

The adverse-event entries provide limited descriptive information: no serious events or deaths are listed, and 6 participants in each group are listed as affected by other adverse events. The record does not provide enough detail to characterize the events or make a comprehensive comparative safety assessment. Secondary outcomes are named, but their analyses and results are not reported.

In general, a randomized design can support a causal comparison when outcomes are collected and analyzed as planned. Here, the intended design should be distinguished from the evidence actually available. Because the primary outcome was not observed at the planned time point, the registry record leaves the main efficacy question unanswered. It also does not report why the trial was terminated, so the reason for the missing primary endpoint cannot be inferred from this record.

13. Why This Trial Matters Statistically

This trial raises an important statistical distinction between a study’s design and its evidential result. Randomization, masking, and a defined endpoint can specify a credible comparison, but the comparison still depends on outcome data. In NCT05479058, the registry describes the intended design and a precise Week 48 remission definition, yet reports that the endpoint was not collected or analyzed because the trial ended before participants reached that time point.

That distinction matters when interpreting terminated trials. An absent result is not a null result: without outcome observations, the data cannot indicate whether the groups were similar or different. Reporting the missing endpoint explicitly helps prevent readers from treating the intended question as though it had been answered.

The record also highlights the value of separating efficacy and safety evidence. The primary efficacy comparison is unavailable, while a limited set of safety counts is reported. Those counts can be described as posted, but they do not fill the gap in the primary endpoint or establish a full comparative safety profile. Likewise, the names of secondary outcomes do not amount to analyzed findings.

For statistical interpretation, the key information is not only the design label or enrollment but whether the planned outcome was observed, what analysis was performed, and how uncertainty was quantified. The registry does not report a primary estimate, an analysis plan, or the reason for termination. Keeping those absences visible makes the limits of inference clear and avoids drawing conclusions beyond the reported data.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The most important trial-specific limitation is that the study was terminated before any participant reached the Week 48 primary analysis time point. The registry states that the primary endpoint data were not collected and analyzed. As a result, there is no reported primary efficacy comparison and no estimate of its precision.

The record does not report why the study was terminated, how long participants were followed, or whether any interim review informed the decision. It does not report a trial-specific sample-size justification, a statistical analysis plan, multiplicity handling, missing-data methods, or analysis-population definitions. These details are not reported in the registry record and cannot be inferred from the randomized design.

Although secondary outcomes are listed, their results are not reported. The safety summary provides participant counts but not the event-level information needed to describe the types, timing, or severity patterns of events. The registry lists 22 participants enrolled and 11 at risk in each group in the adverse-event summaries; the record does not explain additional details of participant disposition or follow-up.

The trial enrolled participants already in remission on filgotinib 200 mg once daily in another ongoing study, according to the planned rollover description. The results therefore cannot be generalized from this record to populations or treatment settings not described in the study plan. More fundamentally, because the planned primary outcome was not observed, the record cannot support a comparative conclusion about the two dose strategies.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study Evaluating the Effect of Filgotinib Dose De-escalation in Participants With Ulcerative Colitis (UC) in Remission — NCT05479058.
• Registry record last updated 2024-10-04; status last verified 2024-09.
• Results first posted 2024-10-04.
• 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

NCT05479058 was a phase 3 randomized, double-blind, controlled, multicenter, parallel-group study of filgotinib dose de-escalation in participants with ulcerative colitis in clinical remission. The planned comparison was filgotinib 100 mg once daily versus continued filgotinib 200 mg once daily, with matching placebo. Enrollment was 22.

The primary endpoint was corticosteroid-free clinical remission according to the modified Mayo Clinical Score at Week 48. The registry states that the study was terminated before any participant reached that time point, so the endpoint was not collected or analyzed. Secondary outcomes are listed, but analyses are not reported.

The safety summaries list 11 participants at risk in each group, no serious adverse events, 6 participants affected by other adverse events in each group, and no deaths. The reason for termination and the trial’s statistical analysis plan are not reported in the registry record.