A Phase 3B, Open-label, Single-arm Study of the Efficacy and Safety of Apremilast, in Subjects With Plaque Psoriasis That is Not Adequately Controlled by Topical Therapy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Phase 3B, Open-label, Single-arm Study of the Efficacy and Safety of Apremilast, in Subjects With Plaque Psoriasis That is Not Adequately Controlled by Topical Therapy (NCT03930186), a na phase 3 study. The primary outcome is Percentage of Participants Who Achieved an sPGA Score of Clear (0) or Almost Clear (1) at Week 16.

2. Clinical Question

The clinical question concerns response during treatment with apremilast added to existing topical therapy in adults whose plaque psoriasis was not adequately controlled by topicals alone. The primary endpoint focuses on the overall appearance and severity of psoriasis at a specified assessment, rather than on a comparison between treatments. The sPGA response category combines scores of clear and almost clear.

Because the study had a single group, its results can describe outcomes among enrolled participants, but the design does not provide a randomized estimate of how those outcomes compare with what would have occurred under another treatment or without apremilast. The registry record identifies secondary outcomes concerning scalp assessment, body surface area, pruritus, nail psoriasis, quality of life, and PASI. Their numerical results are not reported in the record information available for this analysis.

3. Trial Design

This was a phase 3b, open-label, single-arm study of apremilast in participants with plaque psoriasis not adequately controlled by topical therapy. The registry lists 152 participants as enrolled and the study status as completed. The study started on 2019-06-17, with primary completion on 2020-05-08. These dates describe the registry record and do not supply results for the primary endpoint.

All participants received apremilast alongside their existing topical therapy. The regimen description states that, after a 5-day titration, participants received apremilast 30 mg tablets orally twice daily for up to 32 weeks. At week 16, participants were permitted to decrease topical therapy at their own discretion under direction. The record therefore describes a treatment strategy that included both apremilast and ongoing topical treatment, with permitted changes to topical use during follow-up.

The study was open-label, meaning the record does not describe blinding of participants or investigators. It was also single-arm, with no randomized allocation or concurrent control arm. The registry explicitly lists allocation as not applicable and masking as none. These design features matter when interpreting outcomes: observed changes or response rates describe the enrolled group during the study, but cannot isolate the contribution of apremilast from other influences, including topical therapy, time, or expectations.

The registry lists 14 outcome measures. The primary measure was the percentage of participants who achieved an sPGA score of clear or almost clear at week 16. Secondary outcomes covered other clinical and patient-reported measures and additional assessment times. The numerical primary result, its confidence interval, and numerical results for secondary outcomes are not reported in the registry record. The registry record also does not report a statistical analysis plan or a sample-size justification.

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.

Weeks 0 to 16

Reasons for not completing this period:

Weeks 16 to 32

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The enrolled population; missing values through week 16 were imputed using the multiple imputation (MI) method.

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: All enrolled participants

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants Who Achieved an sPGA Score of Clear (0) or Almost Clear (1) at Week 16, measured over Week 16.

The primary endpoint is the percentage of participants who achieved an sPGA score of clear or almost clear at week 16. The investigator’s sPGA assessment describes overall disease severity at the time of evaluation. It considers erythema, induration, and desquamation, with each component scored on a 5-point scale from 0, clear, to 4, severe. The overall static PGA score is calculated by averaging the total-body scores for those components. The response threshold groups an overall score of 0, clear, with a score of 1, almost clear.

A threshold-based endpoint gives a clinically interpretable description of the proportion of participants meeting a specified response category at a defined assessment. It is different from an average change score: it classifies participants according to whether they met the response definition. The endpoint’s usefulness depends on consistent assessment and transparent reporting of the response estimate, its uncertainty, and the population analyzed.

For this outcome, the registry says the percentage was estimated using multiple imputation from 100 imputed data sets, with missing values through week 16 imputed. The registry identifies the enrolled population as the population for the endpoint. However, it does not report the resulting response percentage or 95% confidence interval. Thus, the endpoint definition and stated handling of missing values can be described, but the magnitude and precision of the observed response cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a binary percentage endpoint: participants either met the sPGA response definition at week 16 or did not. The primary measure is the percentage achieving a score of clear or almost clear. For this kind of endpoint, an estimate expresses the observed proportion in the analyzed population. A confidence interval describes uncertainty around that estimate under the analysis method. It does not guarantee that the true response lies within its limits, and it is not a measure of the probability that a treatment is effective.

For this study, the response estimate and its 95% confidence interval are not reported in the registry record. That absence means the endpoint cannot be interpreted quantitatively from the available registry information. The record identifies the endpoint, assessment time, population, and missing-data approach, but those details do not substitute for the response estimate and interval.

What does multiple imputation mean?

The registry states that the percentage was estimated using multiple imputation from 100 imputed data sets, and that missing values through week 16 were imputed. Multiple imputation is a general statistical approach for addressing missing outcome values. Instead of assigning a single fixed value to every missing observation, the method uses a model to create multiple completed data sets that reflect uncertainty about those missing values. Estimates from the completed data sets are then combined so that uncertainty from imputation is represented in the final analysis.

The method depends on assumptions about the process that led to missing data and on the model used to generate imputations. The registry record does not report the imputation model, its variables, the assumptions used, or diagnostic checks. It also does not report how many week-16 values were missing. Consequently, the stated use of multiple imputation can be described, but its implementation and sensitivity to assumptions cannot be evaluated from the record.

What does the single-arm design allow?

In a single-arm study, outcome summaries describe the group receiving the study regimen. They do not supply a randomized comparison with another treatment. General statistical interpretation distinguishes an outcome observed during treatment from a treatment effect, which requires a comparison that addresses what would have happened under an alternative. Without a control group in this trial, potential influences such as concurrent topical treatment, changes over time, and expectations cannot be separated from the effect of apremilast.

Open-label conduct also means the study was not masked, according to the registry. The sPGA is an investigator assessment, and knowledge of treatment can be relevant to the possibility of assessment or reporting influences. This is a general design consideration; the registry does not report evidence that any such influence occurred.

What can be said about statistical significance?

The registry record does not report a primary hypothesis test, p-value, or comparison estimate. With no comparator arm, a between-group treatment contrast is not available in the design described. A confidence interval for a single-group percentage would express uncertainty about that percentage, but would not create a randomized comparison. The registry record does not report an inferential analysis that could be used to make a comparative claim.

The record lists 14 outcome measures, but does not report a multiplicity strategy or an analysis plan specifying how multiple outcomes were to be handled. In general, when many outcomes or tests are considered, the chance of at least one apparently notable finding can increase unless the analysis plan addresses that issue. The extent of any such concern cannot be assessed without the planned testing hierarchy and numerical results.

How should planning illustrations be understood?

Any sample-size figures associated with this study are planning illustrations based on an observed effect, rather than the trial’s own design justification. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is expressed as a fraction of the observed effect. The registry record does not report the trial’s own sample-size justification. Such illustrations do not represent observed power, and they do not establish that this single-arm study was designed to test a randomized two-arm contrast.

General power calculations describe the probability of detecting a specified effect under stated assumptions if that effect exists. They do not measure the probability that a study’s conclusion is correct, and a retrospective calculation based on an observed effect is especially unsuitable as evidence that a study was adequately powered. The relevant planning assumptions can help explain an illustration, but no such calculation replaces the missing primary estimate, its uncertainty, or a prespecified analysis plan.

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("Apremilast")
n      <- c(152)
events <- c(66)
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  Apremilast  152  66  43.4  35.4  51.7  35.8  51.4  35.8  51.4

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 14 outcome measures, including the primary week-16 sPGA response and secondary measures relating to sPGA at week 32, scalp assessment, body surface area, pruritus, nail psoriasis, quality of life, and PASI. The registry record does not report a multiplicity adjustment, testing hierarchy, or other strategy for interpreting results across these outcomes. In general, multiplicity matters when several outcomes or tests are examined because the chance of finding at least one apparently notable result can rise as the number of tests increases. The record does not provide enough information to assess how that issue was addressed in the study analysis.

For the primary endpoint, the registry says missing values through week 16 were handled with multiple imputation using 100 imputed data sets. It identifies the enrolled population as the population for that endpoint. It does not report the amount or pattern of missing data, the imputation model, the assumptions underlying imputation, or sensitivity analyses. These omissions prevent an assessment of how robust the estimate would be to alternative assumptions about missing outcomes. The primary estimate itself is not reported in the registry record.

The registry record does not report other analysis populations, such as a per-protocol population, or details of how participants who stopped treatment or deviated from treatment were handled. It also does not report the statistical analysis plan. The registry lists 0 analyses, so the analysis details and numerical outcome results are not available in the record information. The stated imputation approach is therefore the principal reported detail about the primary endpoint’s analysis population and missing data.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: deafness unilateral (0.7%), gastroenteritis (0.7%), thoracic vertebral fracture (0.7%), blood creatine phosphokinase increased (0.7%), depression (0.7%).

The registry reports a single safety group, Apremilast 30 mg. Serious adverse events affected 4 participants among 152 at risk; other adverse events affected 84 participants among 152 at risk. The record lists 0 deaths. These are counts of participants, not counts of every event, and the registry information does not describe whether individual participants experienced more than one event.

The serious-event terms listed are deafness unilateral, gastroenteritis, thoracic vertebral fracture, blood creatine phosphokinase increased, and depression. Each term is reported as 0.7%. The record does not give further details about timing, duration, severity beyond the serious-event classification, outcomes, or attribution. The terms should therefore be read as registry safety listings, not as evidence that the study treatment caused the events.

These figures describe the study group and do not provide a comparison with an untreated or alternative-treatment group. They cannot establish whether event frequency was higher or lower than it would have been under another strategy. The registry record also does not provide a fuller account of adverse-event definitions or ascertainment in the information. Safety counts are useful for describing what was recorded, but they do not by themselves determine comparative safety or causation.

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

The registry record establishes that a completed, phase 3b, open-label, single-arm study enrolled 152 participants with plaque psoriasis not adequately controlled by topical therapy. Participants received apremilast alongside existing topical therapy, with apremilast given twice daily after a 5-day titration for up to 32 weeks. The primary outcome was defined as achieving an sPGA score of clear or almost clear at week 16, and missing values through that assessment were handled using multiple imputation.

Those design and methods details do not reveal how many participants met the primary response definition. The primary percentage and its 95% confidence interval are not reported in the registry record. As a result, the magnitude of the response and its statistical precision cannot be assessed. Enrollment size alone cannot establish either quantity.

Even if a response estimate were reported, this single-arm study would describe outcomes in participants treated with apremilast plus topical therapy rather than establish a randomized treatment effect. The design does not distinguish the contribution of apremilast from topical treatment, time-related changes, or other influences. The permitted change in topical use at week 16 is also part of the treatment context. No conclusion about comparative efficacy follows from this design alone.

The record reports selected safety counts, including serious adverse events in 4 of 152 participants at risk and 0 deaths. These figures describe recorded events in this group. With no comparator group and limited event detail in the registry information, they do not establish that treatment caused or prevented any particular event, or determine comparative safety.

The registry identifies several additional outcomes, but their numerical results and the statistical plan for handling multiple outcomes are not reported. Therefore, the available information supports an account of the study’s question, design, endpoint definition, missing-data method, and selected safety summaries. It does not support a numerical conclusion about the primary response or a comparative claim about treatment effects.

14. Why This Trial Matters Statistically

This study is statistically informative as an example of the distinction between an outcome definition and an outcome result. The registry specifies a clear threshold for the primary endpoint, names the assessment time, and describes how missing values were handled. Yet the primary percentage and confidence interval are not reported in the registry record. A well-defined endpoint is essential for interpretation, but it cannot show the size or precision of a response without the numerical estimate.

The design also illustrates why the presence of a treatment group does not automatically provide a treatment comparison. This was an open-label, single-arm study. Its observations can describe participants receiving apremilast with topical therapy, but there is no randomized group to represent an alternative treatment strategy. That distinction helps prevent a response observed during treatment from being mistaken for a causal treatment effect.

The study further highlights the importance of understanding the treatment context. Participants continued existing topical therapy, and were permitted to reduce topical use at week 16 at their own discretion under direction. Thus, outcomes relate to a regimen that included both study medication and topical care, with possible changes in topical use. The registry does not report data that would separate those components.

Finally, the record names multiple secondary outcomes and a multiple-imputation approach for the primary endpoint, while leaving the analysis plan, multiplicity handling, and numerical outcome results unreported. Those gaps show why statistical interpretation relies on more than endpoint labels: readers need estimates, uncertainty, analysis details, and a design capable of addressing the question being asked. The reported safety counts add descriptive context but do not supply a comparative safety assessment.

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 principal limitation for interpreting efficacy is that the registry record does not report the primary response percentage or its 95% confidence interval. Without the estimate, the observed frequency of clear or almost clear status at week 16 and its precision are unknown from the record. The enrolled count does not fill that gap.

The single-arm, open-label design provides no randomized control group. Any outcomes describe participants receiving apremilast in addition to topical therapy, rather than a contrast with another treatment. The design cannot isolate the contribution of apremilast from topical treatment or other influences. Because topical therapy could be reduced at week 16 at participants’ discretion under direction, the background treatment could also vary during follow-up; the registry record does not quantify this variation.

For the primary endpoint, multiple imputation was used for missing values through week 16, but the record does not report the amount or pattern of missingness, the imputation model, or sensitivity analyses. The impact of missing-data assumptions therefore cannot be evaluated. The registry also does not report a statistical analysis plan, multiplicity handling for the 14 listed outcome measures, or numerical secondary outcome results. It does not provide a sample-size justification for the study.

Safety information is limited to the reported event counts and listed serious-event terms. The record does not provide further detail sufficient to assess event timing, attribution, or comparative risk. These limitations concern the registry information; they do not establish that additional analyses or details are absent from sources outside the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Phase 3B, Open-label, Single-arm Study of the Efficacy and Safety of Apremilast, in Subjects With Plaque Psoriasis That is Not Adequately Controlled by Topical Therapy — NCT03930186.
• Registry record last updated 2022-01-20; status last verified 2021-12.
• Results first posted 2022-01-20.
• 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 completed phase 3b, open-label, single-arm study of apremilast added to topical therapy in adults with plaque psoriasis not adequately controlled by topicals alone. The study enrolled 152 participants. Apremilast was given at 30 mg orally twice daily after a 5-day titration for up to 32 weeks. The primary endpoint was the percentage achieving an sPGA score of clear or almost clear at week 16; the percentage and 95% confidence interval are not reported in the registry record. Missing primary endpoint values through week 16 were handled with multiple imputation from 100 imputed data sets. The safety record lists serious adverse events in 4 of 152 participants at risk, other adverse events in 84 of 152, and 0 deaths. The absence of a randomized comparator limits interpretation to description of outcomes in the study group.