A Study of Secukinumab for the Treatment of Alopecia Areata: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of Secukinumab for the Treatment of Alopecia Areata (NCT02599129), a randomized phase 2 study. The primary outcome is Number of Subjects Achieving Severity of Alopecia Tool (SALT) Score of 50.

2. Clinical Question

3. Trial Design

The registry describes a randomized, double-masked, parallel Phase 2 study of secukinumab for extensive alopecia areata. Its official title characterizes the study as exploratory and intended to evaluate safety and efficacy. The sponsor was Icahn School of Medicine at Mount Sinai. The record gives a start date of 2015-11 and a primary completion date of 2016-11.

The brief summary states that the study aimed to include 30 participants and run for 28 weeks. The reported enrollment is 11, and the study status is terminated. The registry record does not report why the study was terminated or explain how the actual enrollment relates to the original target. These registry entries matter when interpreting the posted results: the outcome counts cover only a small part of the planned study size, and the reasons for the study’s size and termination cannot be inferred from the record.

The registered arms were secukinumab and matching placebo. The secukinumab intervention is described as 300 mg subcutaneous injections; the placebo is described as matching subcutaneous injections. The record labels the design parallel and double-masked, but does not give further operational details about allocation, concealment, masking, treatment duration, or treatment adherence.

The primary outcome was the number of participants achieving a SALT score of 50 at Week 24. Four secondary outcomes are listed, including SALT score of 90 at Week 24 and Week 28, a Physician’s Global Assessment score of 3 or above, and a Dermatology Life Quality Index score of 3 or above. The record lists five outcome measures in total. It does not post results for the secondary outcomes in the information available for this analysis.

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 Subjects Achieving Severity of Alopecia Tool (SALT) Score of 50, measured over Week 24.

The primary endpoint is a count: the number of participants achieving a Severity of Alopecia Tool (SALT) score of 50 at Week 24. SALT is a measure of the extent of scalp hair loss. A score can therefore represent a clinical state of hair loss, while a count of participants meeting a specified score threshold expresses how many met the endpoint criterion. The registry record does not provide further detail on how the threshold was applied, including whether it required a particular baseline-to-follow-up change. That definition should not be inferred from the endpoint label alone.

A categorical count endpoint can be useful when a study wants to report whether participants meet a defined clinical criterion at a specified follow-up time. It is readily described as the number meeting the criterion and the number assessed. However, that count does not by itself describe the full distribution of SALT scores, the amount of change from baseline, or the experience of participants who do not meet the criterion. Those interpretations require additional outcome definitions and data.

For this endpoint, the registry posts zero participants meeting the criterion in each arm. The outcome denominator is 2 for secukinumab and 1 for placebo. With such sparse outcome data, the counts give little information about how likely the endpoint would be in a broader population or whether the arms differ. The posted information does not include a comparative estimate or confidence interval.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is binary at the participant level: each participant either meets the stated SALT score criterion at Week 24 or does not. The registry reports the endpoint as a count of participants meeting the criterion. This is different from reporting a continuous SALT score for each participant or a change in score from baseline. The registry record does not report individual scores, a summary of score changes, or a detailed endpoint definition beyond the stated score and time point.

What do the posted counts tell us?

A count describes the observed participants in the record. Here, no participant in either posted arm is counted as achieving the primary endpoint. Such a result is compatible with a range of underlying event probabilities, especially when the outcome denominators are very small. The observed count is not a precise estimate of what would happen in a broader population. A confidence interval, when reported for a proportion or treatment contrast, conveys the uncertainty compatible with the observed data under the method used. No confidence interval is reported for this primary comparison.

In general, a comparison of binary outcomes can be expressed using an absolute difference in event probabilities, a relative measure, or a model-based contrast. These approaches describe different aspects of a comparison and can behave poorly when event counts are sparse or absent. No comparative estimate is available in the registry record. A new estimate should not be reconstructed from the posted counts and presented as though it were the sponsor’s analysis. The record specifically flags the binary two-arm comparison as having values missing or not estimable; there is no sponsor analysis reported to supersede that limitation.

Why does sparse data matter?

When only a few participants contribute outcome information, the estimate can change substantially with the result of even one additional participant. When no events are observed, some relative-effect methods cannot produce a finite estimate without special methods or additional assumptions. Those methods can yield materially different answers, so an analyst must state the method and assumptions rather than imply that the data uniquely determine a treatment effect. The registry record does not report such a method or assumptions.

Randomization is intended to make treatment groups comparable on average, but it does not ensure balance in a small study. A randomized design also does not overcome sparse outcomes or missing information. The registered design is randomized, double-masked, and parallel. The record does not report enough implementation detail to assess the randomization process, masking success, or adherence.

What is over-dispersion, and does it apply?

Over-dispersion is a general issue in count-data models: observed variation can exceed what a simple model assumes, often because participants or observation periods differ in ways the model does not capture. It matters when the endpoint is analyzed as a variable count, because underestimated variation can make uncertainty appear too small. This primary endpoint, however, is presented as a count of participants meeting a binary criterion, not as a repeated or exposure-based event count. The registry record does not report an over-dispersion model or a reason to apply one to this endpoint.

What do the planning assumptions mean?

General sample-size calculations estimate how many participants might be needed under stated assumptions to detect a chosen effect with a chosen probability of identifying it. They are planning illustrations, not evidence about the power actually achieved in a completed study. The record describes an illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects expressed as stated fractions of the observed effect. It does not report the numerical planning results in the registry record available for this analysis. Because the observed primary endpoint counts are zero in both arms, a planning exercise based on an observed contrast must be interpreted cautiously; it cannot turn these sparse results into evidence of a treatment effect.

In general, power is the probability that a specified statistical procedure will identify a specified effect under its assumptions. It is not a property that can be read directly from the observed outcome counts after a study, and a retrospective calculation based on the observed effect is not “observed power.” A useful planning calculation depends on the target effect, variability or event rate, allocation, type I error, and chosen power. The registry record does not report the protocol’s original sample-size justification or enough information to reconstruct it. The planned enrollment in the brief summary is not, by itself, a sample-size rationale.

What can be learned from the comparison?

The posted primary endpoint counts permit a plain description of what was recorded in the assessed participants. They do not support a precise estimate of the treatment contrast, and the record does not give an adjusted analysis. In general, an adjusted model may account for prespecified covariates, but it requires a statistical plan and sufficient data. Neither an adjusted analysis nor the details of a statistical analysis plan are reported in the registry record. The registry also does not report interim analyses. Accordingly, the interpretation should remain descriptive and should not imply a model, hypothesis test, or analysis decision that the record does not document.

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("Secukinumab", "Placebo")
n      <- c(2, 1)
events <- c(0, 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  Secukinumab  2  0  0.0  0.0  84.2  0.0  65.8  0.8  70.8
ARM  Placebo  1  0  0.0  0.0  97.5  0.0  79.3  1.3  84.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures in total: the primary SALT endpoint and four secondary outcomes. The secondary outcomes include SALT score of 90 at Week 24 and Week 28, a Physician’s Global Assessment score of 3 or above, and a Dermatology Life Quality Index score of 3 or above. Results for these secondary outcomes are not reported in the registry record available for this analysis.

When a study evaluates multiple outcomes or multiple time points, the chance of at least one apparently unusual result can increase if each is tested separately without an appropriate plan. General approaches include identifying a primary outcome in advance, adjusting inference across a family of tests, or treating secondary analyses as exploratory. The registry record does not report a multiplicity strategy, a hierarchy of tests, or a statistical analysis plan. It is therefore not possible to say how the study intended to control or interpret multiplicity.

The record gives outcome denominators for the primary endpoint, but does not report participant-level missingness, reasons for missing outcomes, or the analysis population definition. It does not state whether the endpoint was analyzed by intention to treat, per protocol, or another approach. The reported enrollment and the endpoint denominators differ, but the record does not explain that difference. No imputation method or sensitivity analysis for missing outcomes is reported. These omissions limit interpretation of who contributed to the primary result and how missing outcomes may have been handled.

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 non-serious adverse event terms

The registry reports serious adverse events for the safety groups separately from the primary endpoint counts. In the secukinumab safety group, zero serious adverse events are reported among 7 participants at risk. In the placebo safety group, zero serious adverse events are reported among 4 participants at risk. The record also reports zero deaths in each safety group.

These are observed counts, not proof that serious adverse events or deaths cannot occur. With small safety groups, a zero count leaves considerable uncertainty about the frequency of uncommon harms. The record also reports one other, non-serious adverse event in each group, with 7 and 4 participants at risk, respectively. Those figures should not be combined with the serious adverse event counts: they describe a separate category. The registry does not provide serious adverse event terms, so the specific events cannot be characterized from this record.

The safety denominators are not the same as the primary endpoint denominators. They refer to the safety groups and should not be substituted for the number contributing to the Week 24 endpoint. The registry record does not explain the difference between these denominators or provide further details about event timing, severity grading, or attribution.

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

The posted primary outcome is narrowly informative: no participant in either arm’s reported endpoint group achieved the stated SALT score of 50 at Week 24. The result is based on an outcome denominator of 2 for secukinumab and 1 for placebo. It describes those recorded observations, not the likely result in a larger population. The very small denominators and absence of a comparative estimate leave substantial uncertainty.

The result does not demonstrate that the treatments are equivalent. A failure to observe an event in either group is not the same as evidence that the event probabilities are equal. It also does not establish that secukinumab is ineffective or that placebo is effective. Such claims would go beyond the posted counts and the information in the registry record.

The trial’s reported enrollment was 11, while the brief summary describes an aim to include 30 participants. The study is marked terminated. These registry entries signal that the available record is not a complete account of the originally described study size, but the record does not explain the termination or its relationship to enrollment and outcome collection. The cause and consequences cannot be inferred.

The secondary outcomes are listed but results are not reported in the registry record available for this analysis. The record also lacks confidence intervals, p-values, a comparative model, a missing-data description, and a statistical analysis plan. Consequently, the posted information cannot establish the precision of a treatment contrast or explain how the investigators intended to address multiple outcomes.

The appropriate statistical reading is descriptive and cautious. The available primary counts are sparse, the comparison is flagged as not estimable, and the record leaves important design and analysis details unreported. These constraints define what can be concluded from the posted results; they do not supply a reason for the study’s termination or a basis for medical advice.

14. Why This Trial Matters Statistically

This trial illustrates why a registered design and a posted result must be read together. The study was described as randomized, double-masked, and parallel, but those design features cannot compensate for very small outcome denominators. Randomization helps address systematic differences between groups in expectation; with limited outcome information, chance imbalance and uncertainty remain important.

It also shows the difference between a count and an estimate of comparative effect. The registry reports zero participants meeting the primary criterion in each arm, but does not provide a treatment contrast or confidence interval. A reader can accurately describe the observed counts while recognizing that they do not establish equal outcomes or a precise effect.

The record also highlights the importance of distinguishing enrollment from outcome-specific denominators. The reported enrollment is 11, whereas the primary endpoint denominators are 2 and 1, and the safety groups have different denominators. Without participant flow and missing-data information, these quantities cannot be reconciled. They answer different questions and should not be treated as interchangeable.

Finally, the study is marked terminated, yet the reason is not reported. Statistical interpretation depends not only on the outcome values but also on how the study proceeded, what analyses were planned, and how missing data were handled. When those details are absent, the most informative account states what is recorded and clearly marks what remains unknown rather than filling gaps with assumptions.

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 primary outcome is recorded as a count of participants achieving a SALT score of 50 at Week 24, but the registry does not give a fuller definition of “achieving” or explain how the criterion relates to baseline. The posted outcome denominators are small, and the record flags the binary two-arm comparison as having values missing or not estimable. No confidence interval or comparative estimate is reported.

Although reported enrollment is 11, the brief summary describes an intended study size of 30. The study status is terminated, but the reason, timing, and consequences of termination are not reported in the registry record. The record does not provide a participant flow account to explain the outcome denominators or show how many participants were assessed at each follow-up.

The four listed secondary outcomes have no posted results in the record available for this analysis. The statistical analysis plan, multiplicity strategy, analysis population, missing-data methods, and any interim analyses are not reported. The registry also does not provide sufficient detail to assess allocation implementation, masking, adherence, or baseline comparability. These trial-specific gaps limit the interpretation of both the primary outcome and the overall study conduct.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Study of Secukinumab for the Treatment of Alopecia Areata — NCT02599129.
• Registry record last updated 2021-03-11; status last verified 2021-02.
• Results first posted 2017-11-30.
• 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 describes a randomized, double-masked, parallel Phase 2 study of secukinumab for extensive alopecia areata, sponsored by Icahn School of Medicine at Mount Sinai. The listed intervention was 300 mg subcutaneous secukinumab; the comparator was matching placebo. The record gives a start date of 2015-11, a primary completion date of 2016-11, reported enrollment of 11, and status terminated. The brief summary describes an intended enrollment of 30 and a 28-week study.

The primary endpoint was the number achieving a SALT score of 50 at Week 24. The posted counts were zero in both arms, with outcome denominators of 2 for secukinumab and 1 for placebo. The registry does not report a comparative analysis and flags the binary comparison as not estimable. Four secondary outcomes are listed without posted results in the record available for this analysis. The reason for termination, missing-data handling, analysis populations, and statistical analysis plan are not reported.