Efficacy of Abrocitinib for Reducing Pruritus in Adults With Prurigo Nodularis and Chronic Pruritus of Unknown Origin: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy of Abrocitinib for Reducing Pruritus in Adults With Prurigo Nodularis and Chronic Pruritus of Unknown Origin (NCT05038982), a non-randomized phase 2 study. The primary outcome is Percent Change in Weekly Average Peak Pruritus Numeric Rating Scale (PP-NRS) From Baseline to Week 12.

2. Clinical Question

The study’s stated objective was to assess the efficacy, safety, and tolerability of abrocitinib in the two diagnosis groups. The question is therefore about itch ratings over time in participants receiving the study intervention, not about a randomized estimate of the difference between abrocitinib and an untreated or active-comparator group. The diagnosis groups may be described separately, but their outcomes would not establish a causal comparison between diagnoses or between treatments.

The primary measure is a patient-reported rating. Its change from baseline is intended to capture how participants’ reported itch severity varied during follow-up. A within-group change can describe what happened among participants assessed in the study, but without a randomized control it cannot by itself distinguish an intervention effect from other explanations for change, such as time, expectations, or changes in participants’ experience. The registry record does not report the primary result or enough analysis details to assess those possibilities quantitatively.

3. Trial Design

This is a completed Phase 2 study sponsored by Johns Hopkins University. The registry record lists a non-randomized allocation, no masking, and a parallel model. Enrollment was 20. The study start date is 2021-09-09, and the primary completion date is 2022-07-11. The listed conditions include prurigo nodularis, pruritus, chronic pruritus, chronic prurigo, and skin diseases.

Participants are grouped by diagnosis: prurigo nodularis (PN) and chronic pruritus of unknown origin (CPUO). The record describes 10 participants at risk in each group for the adverse-event summaries. Because allocation is non-randomized and the two groups have different diagnoses, they should not be treated as randomized treatment and control arms. The registry record does not describe a separate control intervention.

The arm descriptions state that participants in each diagnosis group undergo a 4-week washout of other therapies that could affect pruritus. For the PN group, the description names antihistamines, topical steroids, systemic antipruritic therapies, and immunosuppressants. The CPUO description is truncated in the registry record; its complete list of therapies is not reported there. The record does not state the abrocitinib dose or schedule in the registry record for this analysis.

The primary outcome is assessed through Week 12. Secondary outcomes include changes in itch severity, quality of life, pruriginous lesions, itch-scratching behavior, nodule count, and nodule severity, using the listed PP-NRS, 5-D Pruritus Scale, Dermatology Quality of Life Index, Prurigo Activity Score, Patient Reported Outcomes Measurement Information System, and EuroQoL 5-Dimension measures. The registry record lists 17 outcome measures and 33 analyses. It does not report the full analysis plan, participant flow, or analysis populations.

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: 25 patients were assessed for eligibility and screening; four patients failed screening due to laboratory values or presence of uncontrolled disease. One patient left the study voluntarily. Therefore, 20 patients were enrolled in the study

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 Percent Change in Weekly Average Peak Pruritus Numeric Rating Scale (PP-NRS) From Baseline to Week 12, measured over Up to 12 weeks.

The primary endpoint is percent change in weekly average PP-NRS from baseline to Week 12, with a timeframe of up to 12 weeks. PP-NRS is described as a single self-report item on an 11-point scale from 0 to10, where 0 is “No itch” and 10 is “the Worst itch imaginable.” A weekly average uses participants’ ratings over a week to represent itch severity, while the percent-change measure expresses the Week 12 value relative to baseline.

Patient-reported itch severity is relevant to this study because pruritus is the symptom named in its objective and the primary measure directly records participants’ experience of itch. Repeated ratings can capture change over the study period rather than relying only on a single rating. The registry record specifies a mean and a 95% confidence interval for the primary endpoint, but the numerical estimate and interval are not reported in the information available for this analysis.

Percent change requires a baseline value as its reference. The registry record does not report how missing ratings were handled, how the weekly average was constructed when some daily ratings were unavailable, or how values were treated if a participant had a baseline score that made a percent change difficult to interpret. Those details are not reported in the registry record. Without the endpoint estimate, its confidence interval, and the analysis details, the magnitude and precision of the observed change cannot be evaluated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies the primary outcome as a continuous measure: percent change in weekly average PP-NRS from baseline to Week 12. It specifies that the summary parameter is a mean and that uncertainty is to be described with a 95% confidence interval. These labels indicate the kind of statistical summary intended, but the numeric mean and interval are not reported in the registry record.

What does a mean describe?

A mean combines observed values into a single summary of their central level. For a continuous outcome such as percent change, it gives an overall average across the participants included in the relevant analysis. It does not show how much participants differed from one another. Participants may have had changes near the mean or substantially different changes; the mean alone cannot reveal that distribution. The registry record does not report a separate measure of variation for the primary endpoint in the registry record for this analysis.

What does a confidence interval describe?

In general, a confidence interval describes statistical uncertainty around an estimate under the assumptions of the analysis. A 95% confidence interval is not a range that is guaranteed to contain the true value, nor is it a range intended to cover 95% of individual participants’ outcomes. Its width depends in part on the variability in the data and the amount of information contributing to the estimate. Because the interval values are not reported in the registry record, its precision cannot be assessed.

A confidence interval is often more informative than a point estimate alone because it shows a range of values compatible with the data and analysis assumptions. Interpretation also depends on the clinical context and on what size of change would be meaningful. The registry record does not report a threshold for meaningful change. No conclusion about whether the estimated change is large, small, or clinically important can be drawn without the estimate, the interval, and a suitable context for judging them.

How should the study design affect interpretation?

General statistical interpretation of a non-randomized study requires attention to the lack of randomized allocation. Randomization can help balance measured and unmeasured factors between treatment groups, on average; this study is not listed as randomized. A before-and-after change in a treated group can describe change during follow-up, but it does not automatically estimate what would have happened over the same period without the intervention. A comparison between PN and CPUO participants would also compare different diagnoses, rather than treatment assignment under otherwise comparable conditions.

The record also lists no masking. In general, awareness of treatment or study participation can influence self-reported outcomes, expectations, reporting, or study conduct. That possibility is relevant to an itch rating because PP-NRS is a self-report measure. This is a design consideration, not evidence that reporting was biased in this study. The registry record does not describe procedures intended to reduce or assess such effects.

What do the planning assumptions mean?

The planning illustration is described as a calculation based on an observed effect, not as the trial’s own design justification. Its 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 a stated fraction of the observed effect. For non-time-to-event outcomes, the illustration is expressed as participants per arm for 80% or 90% power. Such values, when shown, are hypothetical planning quantities: they estimate a sample size under assumptions and are not observed results or evidence that the completed study had a particular probability of finding an effect.

General power calculations depend on assumptions about the effect size, variability, significance level, allocation, and analysis. A calculation based on an observed effect can be especially sensitive to uncertainty in that effect. The planning illustration does not replace the trial’s own sample-size justification, which is not reported in the registry record. It should not be described as observed power, and it cannot establish whether the study was adequately sized for its primary question.

Why can over-dispersion matter?

General statistical explanation: over-dispersion occurs when observed variability is greater than a statistical model assumes. When that happens, standard errors can be underestimated and confidence intervals can be too narrow if the model does not account for the extra variation. Over-dispersion is most directly relevant to count or rate outcomes and their models; the primary endpoint is described as a continuous mean. The registry record does not identify a model for the primary analysis or report an over-dispersion assessment, so it would be inappropriate to claim that over-dispersion was present or affected the primary result.

More generally, the analysis details matter for a mean percent change. Choices about which participants contribute, how repeated ratings are summarized, how missing observations are handled, and whether any adjustment is used can affect an estimate and its uncertainty. The registry record does not report these details in the information available for this analysis. Consequently, a full appraisal of the statistical methods cannot be made from the stated endpoint definition alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists 17 outcome measures and 33 analyses. When a study assesses multiple outcomes or performs multiple analyses, the chance of observing a seemingly notable result among them can increase. General approaches to this issue include specifying a primary endpoint in advance, defining a hierarchy among outcomes, or adjusting inference to account for multiple comparisons. The primary endpoint is identified in the record, but a multiplicity strategy is not reported in the registry record.

That omission does not establish that no multiplicity approach was used; it means the approach cannot be assessed from the registry information available for this analysis. The registry record also does not identify which secondary measures were confirmatory versus exploratory, or how many analyses contributed to any specific conclusion. Secondary findings should therefore be interpreted with attention to their role in the analysis plan, which is not reported.

Missing-data methods are also not reported in the registry record. For repeated self-reported itch ratings, incomplete observations could affect both the weekly average and the baseline-to-Week 12 comparison. Different methods for handling missing ratings can make different assumptions about the unobserved values. The record does not specify whether participants with missing ratings were excluded, whether values were imputed, or whether sensitivity analyses were conducted.

The analysis populations are not reported in the registry record. It is not stated which participants contributed to the primary analysis, whether all enrolled participants were included, or how participants who discontinued or lacked endpoint measurements were treated. These details are important for understanding how the reported estimate would relate to the enrolled population. The registry record also does not report interim analyses or a statistical analysis plan. Their presence or absence cannot be inferred from the endpoint description or the completed status.

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 registry safety summaries list 10 participants at risk in each diagnosis group. In the PN group, 0 participants were affected by serious adverse events, and 4 were affected by other adverse events. In the CPUO group, 0 participants were affected by serious adverse events, and 2 were affected by other adverse events. No deaths are listed in either group.

These are counts of participants, not counts of all individual event occurrences. The registry entries available for this analysis do not list terms for serious adverse events. A recorded count of zero means that the registry summary lists no affected participants in that category; it does not demonstrate that the risk is absent. With 10 participants at risk in each group, the summaries are limited descriptions of events recorded during this study, not precise estimates of uncommon harms.

“Other adverse events” is distinct from “serious adverse events” in these summaries. The registry information does not provide the event terms, severity, timing, or duration for the other events. There is also no randomized control group for a like-for-like comparison. The counts therefore cannot establish whether the intervention caused an event or compare event risk against a control treatment.

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

The registry record documents a completed Phase 2 study of abrocitinib in adults with prurigo nodularis or chronic pruritus of unknown origin. It defines a patient-reported primary itch outcome and identifies other measures of itch, quality of life, lesions, and nodules. It also reports selected adverse-event counts. Those details describe what the study set out to assess and what safety categories were summarized.

The record does not report the numerical primary endpoint result. Without the mean percent change and its 95% confidence interval, the direction, size, and precision of the primary finding cannot be stated. The record also does not provide a threshold for meaningful change. Completion of the study and the presence of an outcome definition are not substitutes for the result itself.

Even if a baseline-to-Week 12 change were available, this non-randomized design would not by itself show what would have happened in comparable participants without abrocitinib. The two diagnosis groups are not randomized control groups and do not provide a direct treatment-versus-control contrast. Lack of masking is another design consideration for a self-reported outcome, but it does not prove that the ratings were biased.

The safety counts indicate that no participants in either group were recorded as having a serious adverse event, while other adverse events were recorded for participants in both groups. These are descriptive findings from a small study and do not establish comparative safety or exclude uncommon events. They should be read alongside the absence of detailed event terms in the registry information available for this analysis.

Accordingly, the registry record supports a description of the design, intended measurements, and selected safety summaries, but not a conclusion about the magnitude or precision of the primary outcome. It also does not provide the analysis details needed to evaluate missing data, multiplicity, or the population included in the primary analysis.

13. Why This Trial Matters Statistically

This study is statistically informative as an example of a clinically focused question evaluated with a patient-reported continuous measure. The primary endpoint uses weekly average PP-NRS to capture itch severity over time, and the registry record specifies a mean with a 95% confidence interval. This makes clear what type of estimate would be useful for describing change, while also showing why the estimate and its uncertainty are essential to interpretation.

The design highlights the distinction between observing change and estimating a treatment effect. With non-randomized allocation and no described control group, a within-group change cannot isolate the intervention’s contribution. The PN and CPUO groups are clinically different categories, so their comparison is not equivalent to a randomized comparison of treatment strategies. These distinctions matter when interpreting a study objective framed around efficacy.

The registry also lists a range of secondary outcomes and multiple analyses, bringing multiplicity into view. Without a reported plan for prioritizing or adjusting those analyses, readers cannot determine how secondary findings were positioned relative to the primary question. Missing-data methods and analysis populations are likewise important because the primary measure relies on repeated self-reported ratings, yet these methods are not reported in the registry record.

Finally, the small enrolled cohort and limited safety summaries illustrate the difference between recording no serious events and establishing that serious harms cannot occur. The counts provide a transparent description of the registry’s recorded events, but they cannot provide a precise comparative safety estimate. The study’s value for statistical interpretation therefore lies in examining its measurement and design alongside the limits of what the record reports, rather than treating completion or endpoint definition as a result.

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 principal limitation for interpreting the primary outcome is that its numerical result is not reported in the registry record. Neither the mean percent change nor its 95% confidence interval is available in the registry record for this analysis. The magnitude and precision of change therefore cannot be assessed, and no conclusion about the primary endpoint should be inferred.

The non-randomized allocation, absence of masking, and lack of a described control group limit causal interpretation. The two groups are defined by different diagnoses, so they are not interchangeable treatment and control populations. Any comparison between them would need to account for the different clinical groups, and the registry record does not describe an adjusted comparison.

The record lists 20 participants, with 10 in each diagnosis group for safety summaries. This cohort provides limited information about less common outcomes. The safety information available for this analysis reports participant counts but not event terms for other adverse events, their timing, severity, or duration. No serious adverse event participants or deaths are listed, but these summaries cannot establish that such events are impossible.

Several analysis details are not reported in the registry record: the primary analysis population, missing-data methods, the full statistical plan, any multiplicity strategy, and any interim analyses. The CPUO arm description is truncated, so the complete washout therapy list for that group is not available. The abrocitinib dose and schedule are also not reported in the registry record for this analysis. These omissions constrain reproducibility and appraisal of the primary estimate, even if a numerical result is reported elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Efficacy of Abrocitinib for Reducing Pruritus in Adults With Prurigo Nodularis and Chronic Pruritus of Unknown Origin — NCT05038982.
• Registry record last updated 2023-07-03; status last verified 2023-06.
• Results first posted 2023-07-03.
• 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

NCT05038982 is a completed, non-randomized Phase 2 study sponsored by Johns Hopkins University. The listed intervention is abrocitinib, and enrollment was 20 adults in parallel diagnosis groups: prurigo nodularis and chronic pruritus of unknown origin. The registry record lists no masking and identifies percent change in weekly average PP-NRS from baseline to Week 12 as the primary outcome.

The primary measure is a self-reported itch rating on an 11-point scale from 0 to10. Secondary measures cover itch, quality of life, lesions, itch-scratching behavior, and nodules. The primary numerical result, statistical analysis plan, analysis populations, and missing-data methods are not reported in the registry record.

For safety, no serious adverse event participants or deaths are listed in either group. Other adverse events affected 4 participants in the PN group and 2 in the CPUO group. These are descriptive counts without a randomized control comparison.