Long-Term Safety of IDP-118 Lotion in the Treatment of Plaque Psoriasis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Long-Term Safety of IDP-118 Lotion in the Treatment of Plaque Psoriasis (NCT02462083), a na phase 3 study. The primary outcome is Percentage of Participants Who Experienced Grade 3 Local Skin Reactions.

2. Clinical Question

3. Trial Design

This was a Phase 3, multicenter, open-label, single-group study of IDP-118 lotion for plaque psoriasis. The registry record lists enrollment of 555 and study status as completed. The recorded start date is 2015-08-11, and the primary completion date is 2017-01-31. Allocation is listed as NA, and masking as none. No randomized allocation or blinded assessment is described in the registry record.

Participants were assigned no study comparator in the design described. The intervention description specifies topical application to affected areas once daily for 8 weeks and then as needed once daily for up to 1 year. This is a treatment schedule, not evidence that every participant used the lotion for the same duration or with the same frequency. Individual exposure and adherence are not reported in the registry record.

The registry lists one primary outcome measure and zero analyses. The primary measure is the percentage of participants experiencing Grade 3 local skin reactions from baseline up to Week 52. The record defines the safety population as participants who received at least one confirmed dose and had at least one post-baseline safety assessment. For adverse-event reporting, the registry lists a group of 550 at risk for serious events and a group of 550 at risk for other events. These are the denominators attached to those safety summaries; the record does not explain the relationship between these denominators and the enrollment total in further detail.

The open-label, single-group design can describe events observed during treatment, but without a concurrent control group it cannot establish how event occurrence would compare under another treatment or no treatment. The record does not report the protocol, eligibility details, handling of treatment discontinuation, scheduled visit details, interim analyses, or a statistical analysis plan. These omissions limit what can be reconstructed about study conduct and analysis from the registry record alone.

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:

Analysis population for the primary outcome, as defined in the registry: Safety population included all participants who received at least one confirmed dose of study drug and had at least one post-baseline safety assessment.

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 population included all participants who received at least one confirmed dose of study drug and had at least one post-baseline safety assessment.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants Who Experienced Grade 3 Local Skin Reactions, measured over Baseline up to Week 52.

The primary endpoint was the percentage of participants who experienced a Grade 3 local skin reaction at any point following the first application of study drug, over the timeframe from baseline up to Week 52. The reactions included itching, dryness, and burning or stinging. The record defines severe itching as intense itching reported by the participant within the last 24 hours that may interrupt daily activities or sleep. Severe dryness was investigator-assessed and described as marked roughness of the skin. Severe burning or stinging was a hot burning sensation reported within the last 24 hours, causing definite discomfort and potentially interrupting daily activities or sleep.

A binary endpoint records whether each participant did or did not meet a defined event criterion during the observation period. Expressing the result as a percentage can make the frequency of an event easier to interpret in relation to the assessed population. For a safety study, a prespecified severity threshold helps distinguish reactions considered severe from less intense symptoms. This endpoint therefore targets the occurrence of at least one severe local reaction, rather than the number of episodes, duration, or change in symptom intensity.

The registry record does not report the endpoint result, its numerator, an uncertainty interval, or the analysis used to estimate it. It also does not report separate primary results for itching, dryness, and burning or stinging. The definitions clarify what was intended to count, but do not establish how many participants met the criteria.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a single-group, open-label study, with no allocation to a concurrent comparator. That design determines what statistical questions can be answered. A single-group safety study can count events observed among participants under study follow-up. It cannot, by itself, estimate a between-group difference because no other group is included for comparison. Open-label conduct means treatment masking is not part of the design described; the registry does not explain whether individual outcomes were assessed by blinded personnel.

What does a binary percentage represent?

The primary outcome is binary at the participant level: a participant either experienced at least one qualifying Grade 3 local reaction during the defined period or did not. A percentage expresses the number meeting the criterion relative to the relevant assessed population. This kind of measure is useful for summarizing event occurrence, but its interpretation depends on the definition of an event, the observation window, and who is included in the denominator. Here, the registry defines the safety population as participants with at least one confirmed dose and at least one post-baseline safety assessment. It does not provide the primary endpoint numerator or denominator in a result entry.

In general, a confidence interval describes the uncertainty around an estimated quantity under a statistical model. For an event percentage, a confidence interval would communicate how much the estimated frequency could vary because the study observed a finite group of participants. The registry record does not report a confidence interval for the primary endpoint, and there is no reported endpoint estimate from which to interpret one. No uncertainty measure for the primary local-reaction result is available in the record.

Why does the absence of a comparator matter?

In a randomized comparison, treatment groups can be compared under a design intended to balance measured and unmeasured factors on average. No such comparison is described: allocation is listed as NA, and the study model is single group. Therefore, any event frequency in the IDP-118 group is descriptive rather than a randomized estimate of excess or reduced risk. A before-and-after comparison would also require suitable measurements and an analysis plan; those are not reported in the registry record.

Open-label observation can be relevant to long-term safety because events are recorded during ongoing use, but awareness of treatment may influence reporting or assessment. The registry record does not describe procedures to limit this influence, nor does it provide enough information to assess its extent. This is a general consideration about open-label designs, not evidence that any particular reported event was misclassified.

How should adverse-event counts be read?

The registry gives 18 serious adverse events among 550 at risk and 131 other non-serious adverse events among 550 at risk. These are counts of participants affected in the recorded adverse-event categories as presented in the record. They should not be reinterpreted as rates per unit of time, because exposure duration and person-time are not reported. Participants could also have had different treatment durations under the schedule of once daily for 8 weeks and then as needed once daily for up to 1 year. The record does not specify whether individuals could contribute to more than one category or event term.

The six serious-event terms shown with 0.2% each are registry-listed event terms. Their percentages are quoted as recorded and are not independently recalculated. These term-level entries do not provide the full clinical context for each event. A serious-event classification is also distinct from an assessment of treatment causality; the record states that adverse events are presented regardless of causality.

What can planning assumptions tell a reader?

In general, sample-size planning estimates the number of participants needed to detect a specified effect under chosen assumptions about significance, power, allocation, and the statistical model. Such calculations depend on the effect size targeted and the outcome variability. A planning illustration based on an observed effect is not observed power, and it does not describe the trial's original design unless the registry reports that it was used for the design. The record does not report a sample-size justification or say that the study was designed around the stated primary endpoint result. Any planning illustration should therefore be distinguished from enrollment, which was 555, and from observed safety outcomes.

The general assumptions noted for planning illustrations include a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the target effect expressed as a fraction of an observed effect. Those assumptions do not turn this single-group study into a two-arm trial, nor do they establish the study's original design. The registry record does not provide the primary result needed to interpret an observed-effect-based illustration. Time-to-event illustrations use a different event-count basis in general; the primary endpoint in this record is a binary percentage, not a reported time-to-event analysis.

Finally, the registry lists zero analyses. No model, hypothesis test, adjustment method, or uncertainty calculation for the primary endpoint is reported. General statistical methods can explain what such procedures would do, but they cannot fill in the absent result or establish which procedure investigators used. Any inference should remain within the limits of the recorded design and information.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists one outcome measure and zero analyses. It does not report a multiplicity strategy, such as a procedure for controlling the chance of false-positive findings when multiple outcomes or comparisons are tested. Since there is no reported analysis result, the record also does not say whether the primary outcome was tested inferentially or whether any secondary outcomes were included in a prespecified testing sequence. No multiplicity adjustment should be assumed.

The stated primary outcome is a percentage of participants with any Grade 3 local skin reaction over the described period. Its safety population consists of people who received at least one confirmed dose and had at least one post-baseline safety assessment. The registry does not provide the number meeting the endpoint or the denominator used in a result, and it does not report how participants lacking a post-baseline assessment were treated in the analysis.

Missing-data methods are not reported in the registry record. There is no stated approach to missing observations, incomplete follow-up, withdrawals, or treatment discontinuation. The record also does not say whether the primary endpoint required assessment at specific visits or how a missing assessment affected classification over the full observation period. These details matter because participants with limited observation may have fewer opportunities for an event to be detected than participants followed longer. This is a general issue in safety follow-up, not evidence about missingness in this study.

The adverse-event summaries use 550 as the number at risk for serious events and 550 for other events, while total enrollment is 555. A participant-flow explanation and the reasons for this denominator are not reported. The safety population definition does not, by itself, establish how these adverse-event denominators were constructed. Without analysis-population details and a missing-data description, the completeness and comparability of follow-up cannot be fully assessed.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: cellulitis gangrenous (0.2%), diverticulitis (0.2%), sepsis (0.2%), tonsillitis (0.2%), colitis ulcerative (0.2%).

The adverse-event summary lists 18 serious adverse events among 550 participants at risk for serious events, and 131 other non-serious adverse events among 550 at risk for other events. It also lists zero deaths. These are descriptive counts for the IDP-118 Lotion group. The registry record states that serious and other non-serious adverse events are reported regardless of causality, so the counts do not establish that the events were caused by treatment.

Six serious-event terms are listed at 0.2% each: Cellulitis gangrenous, Diverticulitis, Sepsis, Tonsillitis, Colitis ulcerative, and Incarcerated umbilical hernia. These term-level summaries should not be read as a complete event narrative. The registry record does not report event timing, duration, recurrence, individual clinical details, or whether a participant experienced more than one event. The listed percentage is reported as recorded, not recalculated.

The serious-event count is separate from the primary endpoint, which concerns severe local skin reactions. Seriousness and Grade 3 severity are different classifications, and the record does not report a primary endpoint result. The safety summary also lacks a comparator and does not report exposure time, so it cannot establish comparative event rates or adjust for differences in time under observation.

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

The record establishes that a Phase 3, multicenter, open-label, single-group study was conducted to evaluate long-term safety of IDP-118 lotion in plaque psoriasis. It describes a regimen of topical use once daily for 8 weeks, followed by once-daily use as needed for up to 1 year, and defines a primary safety endpoint involving Grade 3 local skin reactions. It also reports adverse-event counts for the treatment group and zero deaths.

The record does not report the primary endpoint result. It therefore cannot show the percentage of participants who experienced severe itching, dryness, or burning or stinging, or how precisely that percentage was estimated. The adverse-event counts cannot fill this gap because they describe separate, broader categories. No result is reported for an analysis comparing treatment with another option, and there was no comparator group in the recorded design.

In general, an event observed while a participant is receiving a treatment is not automatically caused by that treatment. A single-group design does not provide a concurrent estimate of how often those events would occur in comparable participants under another condition. The registry indicates that adverse events are reported regardless of causality; it does not provide a causal assessment for the listed events. The counts should therefore be understood as events recorded during the study, not as proof for or against a causal relationship.

The absence of an endpoint result does not mean that no severe local reactions occurred; it means the registry record does not report how many participants met that endpoint. Likewise, the reported adverse-event counts do not establish that treatment was safe or unsafe in a broader population, nor do they quantify comparative safety. The study's enrollment and recorded follow-up schedule alone cannot resolve these questions without outcome results, details about follow-up completeness, and an appropriate comparison for comparative claims.

The most defensible interpretation is limited: the registry documents the study design, endpoint definitions, and selected safety summaries, but not the primary result or a statistical analysis of it. Any conclusion about event frequency, precision, causality, or comparative effect would go beyond what the registry record reports.

13. Why This Trial Matters Statistically

This study illustrates why a safety question and a comparative treatment question are not interchangeable. The stated objective was long-term safety, and the primary measure focused on severe local skin reactions during treatment. That focus is distinct from testing whether one treatment produces better outcomes than another. With a single group and no comparator, the study can describe reported events in its participants but cannot directly estimate a controlled treatment difference.

The endpoint definitions are also statistically important. Itching, dryness, and burning or stinging are grouped under a severe local-reaction outcome, with specified distinctions between participant-reported and investigator-assessed symptoms. Clear operational definitions determine which observations count as events and make a percentage interpretable. Yet a precise endpoint definition cannot replace a reported result: the registry record does not give the primary event count or percentage.

The safety population and adverse-event denominators raise another general issue: interpretation depends on who was assessed and for how long. Enrollment was 555, while the adverse-event summaries use 550 at risk. Without participant flow, follow-up duration by individual, and missing-data methods, readers cannot fully assess the relationship between enrollment, exposure, and recorded outcomes. A fixed observation period can also mean different amounts of actual treatment exposure when use is as needed after the initial period.

Finally, the registry lists adverse events regardless of causality. This is valuable for describing observations, but causal attribution requires more than temporal occurrence. The record's limitations make it especially important to distinguish recorded safety counts from causal or comparative conclusions. The statistical lesson is to match claims to the design and results that are actually reported.

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 central limitation for interpretation is that the registry record does not report the primary endpoint result, despite specifying the measure and its timeframe. There is no reported numerator, percentage, confidence interval, or analysis for Grade 3 local skin reactions. This prevents evaluation of the frequency and precision of the primary safety outcome.

The study is single group, open label, and has no concurrent comparator. Consequently, recorded event counts cannot provide a randomized comparison with another treatment or estimate a contrast against a control condition. Open-label observation may also affect reporting or assessment in general, although the registry record does not describe whether this occurred or what safeguards were used.

The record reports enrollment of 555, while the adverse-event summaries list 550 at risk for each adverse-event category. It does not give participant flow, explain the denominator, or report how many participants completed follow-up. Individual exposure duration, adherence, withdrawals, and reasons for discontinuation are not reported. The regimen includes as-needed use after 8 weeks, so the described maximum schedule does not establish uniform exposure.

Eligibility criteria, baseline participant characteristics, the protocol, and the statistical analysis plan are not reported in the registry record. Neither are the approach to missing data, interim analyses, multiplicity procedures, nor methods for estimating uncertainty. Adverse events are described regardless of causality, and details about event timing, recurrence, and participant overlap are absent. These limitations restrict assessment of completeness, representativeness, precision, and causal interpretation.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Long-Term Safety of IDP-118 Lotion in the Treatment of Plaque Psoriasis — NCT02462083.
• Registry record last updated 2020-01-27; status last verified 2020-01.
• Results first posted 2020-01-27.
• 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

NCT02462083 is a completed Phase 3, multicenter, open-label, single-group study of IDP-118 lotion for plaque psoriasis. Enrollment was 555. The study dates recorded are 2015-08-11 for start and 2017-01-31 for primary completion. The regimen was once-daily topical use for 8 weeks, then once daily as needed for up to 1 year.

The primary outcome was the percentage of participants with Grade 3 local skin reactions from baseline up to Week 52. The registry record defines the reactions and the safety population, but does not report the primary result or an analysis. The adverse-event summaries report 18 serious events among 550 at risk, 131 other non-serious events among 550 at risk, and zero deaths. Events are reported regardless of causality. No comparator was included, and key details about missing data, participant flow, and statistical methods are not reported in the registry record.