An Open-Label, Proof-of-Concept Study of Ixekizumab in the Treatment of Pyoderma Gangrenosum: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for An Open-Label, Proof-of-Concept Study of Ixekizumab in the Treatment of Pyoderma Gangrenosum (NCT03137160), a na phase 2 study. The primary outcome is The Proportion of Subjects Achieving 2-point Reduction in the 5-point Investigator Global Assessment (IGA) for the Target Ulcer at Week 12.

2. Clinical Question

This design frames the question as an early proof-of-concept assessment of change within a treated group. The primary outcome focuses on the investigator’s assessment of target-ulcer severity, not on a comparison of outcomes between independently assigned treatment groups. Because the study has no control arm, any change from baseline would describe what happened among participants receiving ixekizumab during the study; by itself, it would not distinguish treatment effects from other explanations for change over time.

The registry record describes the IGA scale as ranging from 0, clear, to 4, severe, with higher scores indicating worse severity. A reduction of at least 2 points was the stated response criterion. The record does not specify additional elements of the clinical question, such as a minimum duration of improvement or a separate patient-reported outcome. Those details are not reported in the registry record.

3. Trial Design

This was an open-label, Phase 2, proof-of-concept study of ixekizumab for pyoderma gangrenosum. The registry record identifies Ohio State University as the sponsor and lists the study as completed. The recorded start date is 2017-05-04, and the primary completion date is 2018-08-16. Enrollment was four participants.

The design was single-group, with one ixekizumab treatment arm and no allocation to a separate control group. Masking was listed as none. Thus, the study did not compare treatment groups under random assignment, and neither participants nor investigators were masked to treatment according to the registry design fields. The arm description characterizes the work as a small pilot study intended to examine interleukin-17 inhibition in pyoderma gangrenosum.

The primary outcome was the proportion of participants who achieved a 2-point reduction in the 5-point Investigator Global Assessment for the target ulcer at week 12 compared with baseline. The registry record specifies a 12-week timeframe. However, it does not report the primary-outcome count, proportion, or an estimate of uncertainty. The outcome description therefore identifies what was to be assessed, but does not establish what the participants’ recorded results were.

The registry record lists one outcome measure and one analysis. It does not report further details of the statistical analysis plan, including the analysis population, handling of missing assessments, or any prespecified inferential procedure. Those omissions limit assessment of how the primary outcome was to be analyzed. The design and enrollment also mean that the study is best read as a small, uncontrolled investigation rather than as a comparative evaluation.

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: These patients will have histological testing to rule out competing etiologies and require 3rd party adjudication/confirmation on agreement of the diagnosis

Overall Study

Analysis population for the primary outcome, as defined in the registry: The proportion of subjects achieving a two point reduction in the five-point investigator global assessment (IGA) for the target ulcer from baseline 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.

Population: These are patients who have been seen by the primary investigator with the diagnosis of pyoderma gangrenosum, typically within Ohio, USA

6. Primary Endpoint

The registry lists the primary outcome as The Proportion of Subjects Achieving 2-point Reduction in the 5-point Investigator Global Assessment (IGA) for the Target Ulcer at Week 12, measured over 12 Weeks.

The primary endpoint was the proportion of participants achieving a 2-point reduction in the 5-point Investigator Global Assessment for the target ulcer at week 12 relative to baseline. The IGA rates disease severity on a scale from 0, clear, through 1, minimal, 2, mild, and 3, moderate, to 4, severe; the record states that 4 is the worst score. A reduction of 2 points is therefore a threshold for a change in the investigator’s severity rating, not a measurement of the size of change for every participant.

In general, a binary endpoint such as this classifies each participant as either meeting or not meeting the response criterion. The resulting proportion gives a compact summary of how often the specified threshold was reached in the study group. It can be easier to interpret than a group average when the clinical question is explicitly about reaching a defined level of improvement. At the same time, it discards information about changes that do not cross the threshold: participants with smaller score reductions are grouped with those whose scores did not improve, while the endpoint does not distinguish among those who do meet the threshold.

The registry record does not report the number meeting the criterion or the resulting proportion, so the endpoint’s observed result cannot be described. It also does not report the baseline and week-12 IGA values for individual participants. The endpoint definition alone describes the planned measure; it is not evidence that participants did or did not achieve the specified change.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary: each participant either meets the stated response criterion or does not. The criterion was a 2-point reduction in the target-ulcer IGA from baseline to week 12. For a binary outcome, a basic summary is the count of participants meeting the criterion and the proportion of all participants assessed. The registry record identifies the measure as a proportion of participants, but does not report the observed count or proportion. A reader therefore cannot recover the primary result from the endpoint definition alone.

In general, a confidence interval describes uncertainty around an estimate. For a proportion, it conveys how imprecise the estimate may be given the number of observations and the observed response count. With very few participants, the interval is typically broad, and each participant’s outcome has considerable influence on the estimate. This is one reason to read a small pilot estimate as preliminary rather than as a precise estimate of a response rate in a broader population. The registry record does not report a confidence interval for the primary outcome.

The endpoint uses a threshold on an ordinal severity scale. The recorded IGA categories run from 0, clear, to 4, severe. An ordinal scale ranks severity, but the distances between adjacent categories are not necessarily equal in a statistical sense. The primary endpoint does not treat the scale as a continuous measure of change; it classifies participants according to whether their score fell by the specified amount. In general, this makes the response definition straightforward to state, while leaving out information about the exact score changes within each response category.

The study compares week-12 assessment with baseline within the same group. Such a before-and-after comparison can describe observed change, but it does not include a contemporaneous control group. In general, a control group helps separate changes associated with the intervention from changes that may occur over time for other reasons. Here, the registry identifies a single-group design and no allocation to a comparator. It also identifies no masking. Thus, the design provides no randomized, masked between-group estimate of the intervention’s effect.

The registry record lists one analysis, but does not report the analysis method, a statistical model, an estimation procedure, or the analysis population. It does not describe how participants with missing week-12 assessments would be handled, nor whether the primary analysis would use all enrolled participants or a defined subset. These are important details for a binary endpoint because the denominator depends on which participants contribute outcome data. In the absence of those details, the intended analysis cannot be reconstructed beyond the stated response definition and timeframe.

Sample-size planning is distinct from analysis of observed trial outcomes. The planning assumptions described for the sample-size illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. Those are hypothetical planning assumptions; they do not describe the actual single-group design. The record also notes that non-time-to-event planning illustrations are expressed as participants per arm. The registry record does not report a sample-size justification for this study’s own design, nor does it report numerical planning scenarios as part of the trial record.

In general, a planning calculation estimates the sample size needed under specified assumptions about the effect, variability or event rate, significance level, and desired power. The answer depends on those assumptions. A planning result does not show that a study had a particular probability of detecting an effect after the data have been observed; observed power is not a substitute for reporting the estimate and its uncertainty. Here, the study enrolled four participants in one group, while the stated illustrations assume two groups. Those illustrations cannot be treated as a description of the trial’s actual design or as an explanation of how its enrollment target was selected.

The registry does not report whether interim analyses were planned or conducted, how multiplicity was handled, or whether any adjustment for multiple testing was intended. Because the record lists one outcome measure and one analysis, that count alone does not establish the full set of outcomes or decisions considered in the protocol. In general, multiplicity concerns arise when several outcomes, timepoints, groups, or analyses are tested; the registry information is insufficient to determine whether any such procedures were relevant or prespecified.

Finally, safety summaries and the primary binary efficacy endpoint answer different questions. The serious-event counts describe the number of participants recorded as affected among those at risk, while the IGA endpoint concerns a change in target-ulcer severity. Neither should be substituted for the other. In general, safety counts in a small group are descriptive and cannot quantify comparative risk without an appropriate comparator and enough information about event definitions, timing, and participant-level overlap. Those additional details are not reported in the registry record.

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("Ixekizumab (Taltz)")
n      <- c(4)
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  Ixekizumab (Taltz)  4  0  0.0  0.0  60.2  0.0  49.0  0.5  52.2

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one outcome measure and one analysis, with the primary endpoint defined as a 2-point reduction in target-ulcer IGA at week 12. It does not report a multiplicity strategy, such as whether any adjustment for multiple endpoints, timepoints, or analyses was planned. The listed number of outcomes and analyses does not establish whether other measures or exploratory analyses were specified elsewhere in the protocol. Such details are not reported in the registry record.

Missing data are also not described. The record does not state how a participant without a week-12 assessment would be classified, whether any imputation method was planned, or whether missing outcomes would be excluded from the primary analysis. For a proportion, the treatment of missing assessments can affect both the response count and the denominator, so this omission prevents a complete reconstruction of the primary analysis.

The registry does not identify the analysis population or say whether the primary analysis was based on all enrolled participants, participants who received treatment, or participants with an evaluable week-12 assessment. It also does not describe protocol deviations or how they would be handled. These are not minor reporting details: they determine which observations contribute to the endpoint summary and how it should be interpreted.

In general, multiplicity procedures control the chance of false-positive findings when multiple statistical claims are considered, while missing-data procedures make explicit how unavailable outcomes enter an analysis. The appropriate choices depend on the prespecified objectives and data structure. Since these procedures are not reported in the registry record, no specific strategy can be attributed to this study.

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: sepsis (25.0%), infection (25.0%).

The registry lists serious adverse events for the Ixekizumab (Taltz) group: 3 participants were affected among 4 at risk. It separately lists other adverse events affecting 4 participants among 4 at risk, and reports 0 deaths. Sepsis and infection appear among the serious adverse event terms, each with a recorded value of 25.0%.

These are descriptive registry entries, not comparisons with another treatment group. The record does not state whether the participants associated with sepsis and infection were the same or different people, so the terms should not be added together or interpreted as a count of distinct participants. It also does not provide event timing, duration, severity grading beyond the serious classification, or participant-level details. Those details are not reported in the registry record.

In general, adverse-event counts indicate how many participants had events under the registry’s reporting definitions; they do not by themselves establish that the intervention caused an event. With one small treatment group and no comparator, the figures cannot estimate a relative or comparative safety effect. They should be read as the recorded experience in this group, with substantial limits on broader interpretation.

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

The registry record establishes that a small, open-label, single-group Phase 2 study evaluated ixekizumab in pyoderma gangrenosum. It identifies the primary question as whether participants achieved a 2-point reduction in the target-ulcer IGA at week 12 compared with baseline. It also reports safety counts for the treatment group. These details describe the design and the outcomes selected for reporting.

The record does not report the primary endpoint result. There is no stated number or proportion of participants meeting the response criterion and no confidence interval for that proportion. Therefore, the available information does not allow a reader to determine the observed primary response rate or how precisely it was estimated. The endpoint definition must not be mistaken for an outcome finding.

Even a reported improvement in a single group would be descriptive rather than a controlled estimate of the treatment effect. In general, a before-and-after change may be influenced by time-related factors, participant characteristics, or assessment decisions. The open-label design and absence of a comparator mean that the registry design does not provide a direct treatment-versus-control contrast. That limitation applies regardless of the direction of any within-group change.

The adverse-event entries indicate what was recorded among the four participants at risk, including serious events affecting 3 participants and 0 deaths. They do not establish comparative risk or explain causality. The listed terms and percentages are also not enough to determine whether event categories overlap at the participant level.

The study can therefore be understood as a proof-of-concept investigation with a defined clinical assessment and a very small enrolled group. It may inform what outcomes were considered and what safety events were recorded, but the registry information does not support a conclusion about the primary endpoint’s observed magnitude, its precision, or a causal treatment effect. Further outcome detail is not reported in the registry record.

14. Why This Trial Matters Statistically

This study matters statistically because it illustrates the difference between defining an outcome and reporting its result. The registry gives a clear threshold-based primary endpoint: a 2-point reduction on the target-ulcer IGA at week 12 relative to baseline. But without the response count, proportion, or uncertainty interval, readers cannot evaluate the endpoint’s observed value. A well-specified question is essential, yet it does not replace transparent reporting of the answer.

The single-group, open-label design also makes the estimand important. The direct descriptive question is how many participants in the ixekizumab group met the response definition. A causal question—what would have happened under a different treatment or no treatment—requires a comparison that this design does not provide. In general, a randomized control group can support that contrast by accounting for outcomes under an alternative assignment; this study had no such arm.

Enrollment of four participants further emphasizes the role of uncertainty. In small studies, an individual outcome can have a large influence on the observed proportion, and estimates are generally imprecise. This does not make pilot studies uninformative: they can examine feasibility and generate preliminary observations. It does mean that numerical results, if available, need cautious interpretation and should not be treated as definitive estimates.

Finally, the planning assumptions described for sample-size illustrations are not the design of the trial. Their hypothetical two-arm framework differs from the single-group study, and a planning calculation cannot substitute for an observed outcome analysis. The record’s omissions regarding the primary result, missing data, and analysis population limit independent statistical appraisal. These features make the record a useful example of why design, estimand, analysis details, and outcome reporting must be read together.

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 study enrolled four participants and used a single ixekizumab group, with no separate comparator and no masking. These features limit both precision and causal interpretation. With so few participants, the primary response proportion, if reported, would be highly sensitive to individual outcomes. The registry record does not report that proportion or an interval estimate, so its magnitude and precision cannot be assessed.

The primary outcome is based on an investigator-assessed severity scale. The study was open-label, and the registry identifies no masking. In general, awareness of treatment can influence subjective assessments, although the record does not report whether or how assessment procedures were standardized. Details on assessor training, reliability, and handling of changes in the target ulcer are not reported in the registry record.

The record does not describe eligibility criteria beyond the condition, baseline participant characteristics, treatment schedule, adherence, or concomitant care. It also does not state how missing week-12 assessments, protocol deviations, or the analysis population were handled. These omissions make it difficult to assess the representativeness of the enrolled group or reconstruct the planned primary analysis.

For safety, the record supplies group-level counts but not event timing, duration, participant-level overlap, or comparative data. The lack of a control arm prevents a comparative safety assessment. Finally, although sample-size planning assumptions are described for hypothetical two-arm illustrations, the registry record does not report a sample-size justification for this single-group study. These limitations are specific to interpreting this study from the available registry information.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: An Open-Label, Proof-of-Concept Study of Ixekizumab in the Treatment of Pyoderma Gangrenosum — NCT03137160.
• Registry record last updated 2024-02-23; status last verified 2024-02.
• Results first posted 2022-06-06.
• 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

The registry record describes NCT03137160, an open-label, Phase 2, proof-of-concept study of ixekizumab for pyoderma gangrenosum, sponsored by Ohio State University. It lists a single treatment group, no masking, enrollment of four participants, and completed status. The recorded start date is 2017-05-04, and the primary completion date is 2018-08-16.

The primary endpoint was the proportion achieving a 2-point reduction in the 5-point target-ulcer IGA at week 12 compared with baseline. The registry does not report the primary endpoint result or its uncertainty. Safety entries list serious adverse events affecting 3 of 4 participants at risk, other adverse events affecting 4 of 4, and 0 deaths. Sepsis and infection are each listed at 25.0% among serious event terms.

The study’s single-group, open-label design and small enrollment constrain interpretation. Analysis-population details, missing-data procedures, and multiplicity methods are not reported in the registry record.