A Study to Assess if Mirikizumab is Effective and Safe Compared to Secukinumab and Placebo in Moderate to Severe Plaque Psoriasis (OASIS-2): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study to Assess if Mirikizumab is Effective and Safe Compared to Secukinumab and Placebo in Moderate to Severe Plaque Psoriasis (OASIS-2) (NCT03535194), a randomized phase 3 study. The primary outcome is Percentage of Participants With a Static Physician's Global Assessment (sPGA) of (0,1) With at Least a 2-point Improvement From Baseline.

2. Clinical Question

This question concerns a defined clinical assessment at a fixed time, not an overall measure of every aspect of psoriasis or a long-term outcome. The sPGA is the physician's overall assessment of lesions, based on induration, erythema, and scaling. A response requires both a low post-baseline score and improvement from baseline, so the endpoint combines final status with change. The registry describes the study as assessing efficacy and safety; the posted primary outcome is specifically the Week 16 sPGA response.

3. Trial Design

OASIS-2 is a Phase 3, randomized, double-blind, parallel-group study. The registry record describes a multicenter, placebo-controlled comparison of mirikizumab with secukinumab and placebo in moderate-to-severe plaque psoriasis. It lists total enrollment as 1484, and the trial status as completed. The recorded study start is 2018-06-26 and primary completion is 2020-03-05.

The reported primary outcome is assessed at Week 16. Registry arms include placebo, 300mg secukinumab, and 250mg Q4W mirikizumab. The arm descriptions indicate that the mirikizumab regimen involved dosing every four weeks during induction and every eight weeks during maintenance; these descriptions also list different maintenance regimens. The record includes a Japan GPP/EP group and a placebo-to-mirikizumab sequence. These additional groups and schedules are not the three groups displayed for the primary Week 16 comparison.

For the primary result, the displayed analysis populations are 112 participants for placebo, 448 for secukinumab, and 905 for mirikizumab. The primary endpoint states that its population is all randomized participants. The registry reports 1484 total enrollment, but does not explain the relationship between total enrollment and these outcome denominators. Nor does the record explain the allocation ratios or provide a detailed participant-flow account in the registry record. The protocol's original sample-size justification, randomization procedure, and detailed analysis plan are not reported in the registry record.

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.

Induction Period

Reasons for not completing this period:

Maintenance Period

Reasons for not completing this period:

Post-Treatment Followup Period

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All randomized participants.

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 Percentage of Participants With a Static Physician's Global Assessment (sPGA) of (0,1) With at Least a 2-point Improvement From Baseline, measured over Week 16.

The primary endpoint is the percentage of participants with an sPGA score of 0 or 1 at Week 16 and at least a 2-point improvement from baseline. The sPGA is a physician assessment of psoriasis lesions, with scores from 0, clear, through 5, very severe. The assessment considers induration, erythema, and scaling.

This response definition has two requirements: the Week 16 score must indicate clear or minimal disease, and the score must have improved by at least 2 points from the participant's baseline. It therefore distinguishes participants who reach a low score after a meaningful improvement from those who meet only one of those conditions. The endpoint is binary at the participant level: each participant either meets the response definition or does not. The reported group percentage is the proportion meeting it.

A fixed-time responder outcome is straightforward to communicate and compare across randomized groups. However, it condenses a graded clinical assessment into a yes-or-no result. It does not show the full distribution of sPGA scores, the size of improvement for every participant, or how outcomes evolve after Week 16. The registry record identifies the assessment and response rule, but further details about how missing Week 16 assessments were handled are not reported in the registry record.

7. Results Posted in the Registry

• 300mg Secukinumab: 76.3% (342/448) versus 6.2% (7/112) on control; risk difference 70.1 percentage points (95% CI 64.1 to 76.1), risk ratio 12.21 (5.95–25.07); unadjusted two-proportion z-test p = <0.001.
• 250mg Q4W Mirikizumab: 79.7% (721/905) versus 6.2% (7/112) on control; risk difference 73.4 percentage points (95% CI 68.2 to 78.6), risk ratio 12.75 (6.22–26.14); unadjusted two-proportion z-test p = <0.001.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Percentage of Participants Achieving a 75% Improvement in PASI 75

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • 300mg Secukinumab: 89.5% (401/448) versus 8.0% (9/112) on control; risk difference 81.5 percentage points (95% CI 75.7 to 87.3), risk ratio 11.14 (5.95–20.86); unadjusted two-proportion z-test p = <0.001.
  • 250mg Q4W Mirikizumab: 89.5% (810/905) versus 8.0% (9/112) on control; risk difference 81.5 percentage points (95% CI 76.1 to 86.9), risk ratio 11.14 (5.95–20.85); unadjusted two-proportion z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for 300mg Secukinumab than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for 250mg Q4W Mirikizumab than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Percentage of Participants With ≤1% of Body Surface Area (BSA) With Psoriasis Involvement

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • 300mg Secukinumab: 54.5% (244/448) versus 1.8% (2/112) on control; risk difference 52.7 percentage points (95% CI 47.5 to 57.9), risk ratio 30.50 (7.70–120.76); unadjusted two-proportion z-test p = <0.001.
  • 250mg Q4W Mirikizumab: 53.1% (481/905) versus 1.8% (2/112) on control; risk difference 51.4 percentage points (95% CI 47.3 to 55.4), risk ratio 29.76 (7.53–117.70); unadjusted two-proportion z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for 300mg Secukinumab than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for 250mg Q4W Mirikizumab than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Percentage of Participants With a Psoriasis Symptoms Scale (PSS) Symptom Score of 0 in Those With PSS Symptom Score of ≥1 at Baseline

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • 300mg Secukinumab: 28.7% (119/414) versus 1.9% (2/108) on control; risk difference 26.9 percentage points (95% CI 21.8 to 31.9), risk ratio 15.52 (3.90–61.78); unadjusted two-proportion z-test p = <0.001.
  • 250mg Q4W Mirikizumab: 25.0% (212/849) versus 1.9% (2/108) on control; risk difference 23.1 percentage points (95% CI 19.3 to 27.0), risk ratio 13.48 (3.40–53.49); unadjusted two-proportion z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for 300mg Secukinumab than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for 250mg Q4W Mirikizumab than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The posted secondary outcomes cover several aspects of psoriasis response and participant-reported or function-related measures. They include PASI 75, body surface area involvement, symptom score, skin-related quality of life, palmoplantar, scalp, and nail assessments, and the physical component of the SF-36. The three secondary results with detailed Week 16 comparisons in the registry show higher response percentages for both active groups than for placebo on the binary outcomes reported. Their pattern is broadly consistent with the primary sPGA response contrast, while representing distinct measures rather than repetitions of the same endpoint.

These outcomes help show whether the primary finding is accompanied by changes in other clinical domains. They are not interchangeable: a physician-rated global score, extent of body surface area involved, symptoms, and quality-of-life measures capture different aspects of the condition. Some outcomes also apply only to participants meeting baseline criteria, such as having a baseline symptom score or involvement at a specific body site.

The registry lists 17 outcome measures and reports 15 secondary outcomes, but only a subset has detailed estimates and comparisons in the registry record. Results across many endpoints raise the possibility of multiplicity: when many hypotheses are tested, some may appear statistically notable by chance. The registry record does not report a multiplicity adjustment or a hierarchy governing secondary testing. Thus, unadjusted secondary results generally carry less confirmatory weight than a prespecified primary result with a stated analysis. They can provide supporting context, but should not be treated as independent proof for every outcome or as a replacement for the primary analysis.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Percentage of Participants Achieving a 75% Improvement in PASI 75
• Percentage of Participants With ≤1% of Body Surface Area (BSA) With Psoriasis Involvement
• Percentage of Participants With a Psoriasis Symptoms Scale (PSS) Symptom Score of 0 in Those With PSS Symptom Score of ≥1 at Baseline
• Percentage of Participants Achieving a Dermatology Life Quality Index (DLQI) Total Score of (0,1) With at Least a 5-Point Improvement (Reduction) From Baseline in Participants With a Baseline DLQI Total Score ≥5
• Change From Baseline in Palmoplantar Psoriasis Severity Index (PPASI) Total Score in Participants With Palmoplantar Involvement at Baseline
• Change in Psoriasis Scalp Severity Index (PSSI) Total Score in Participants With Scalp Involvement at Baseline
• Change From Baseline in Nail Psoriasis Severity Index (NAPSI) Total Score in Participants With Fingernail Involvement at Baseline
• Change From Baseline on the 36-Item Short-Form Health Survey (SF-36) Physical Component Summary (PCS)

9. Statistical Interpretation

10. Statistical Methods Explained

What does a responder percentage represent?

For a binary endpoint, each participant is classified according to whether the specified event occurred. Here, the event is meeting the sPGA response definition at Week 16. The group percentage describes the frequency of that event within the stated analysis group. It does not preserve all the detail in the original scale: two participants counted as responders may have different baseline and follow-up scores while both satisfy the same rule.

What is a risk difference?

A risk difference subtracts one group's event proportion from another group's event proportion. It is expressed in percentage points when the proportions are presented as percentages. For example, the sponsor-reported mirikizumab-versus-placebo risk difference is 73.5 percentage points. A positive value in this comparison means the estimated response proportion was higher in the mirikizumab group than in the placebo group. This is an absolute contrast, not a relative measure.

The unadjusted re-calculations are simple comparisons from posted summary statistics. They are not the same as the sponsor's Cochran-Mantel-Haenszel analysis. The registry-reported estimate uses that named method and is the appropriate value to quote as the sponsor's analysis. The re-calculated values can provide a check on the broad size of the contrast, but do not replace the analysis reported in the registry.

Why use the Cochran-Mantel-Haenszel method?

In general, the Cochran-Mantel-Haenszel method combines information across strata to estimate an association or contrast while accounting for the stratification used in an analysis. The registry names this method for the reported mirikizumab-versus-placebo primary comparison. The particular strata and the detailed implementation are not reported in the registry record, so no more specific account of the adjustment can be inferred.

What does a p-value communicate?

In general, a p-value describes how compatible observed data are with a specified null model, under the assumptions of the analysis. The registry reports p < 0.001 for the sponsor's primary comparison. This is not the probability that the null hypothesis is true, nor is it a measure of the size or clinical importance of the estimate. Interpretation should consider the estimate, its confidence interval, the endpoint definition, and the analysis plan as well as the p-value.

What does a confidence interval communicate?

In general, a confidence interval gives a range of estimates compatible with the data and the method used to construct the interval. The reported 95% confidence interval for the primary risk difference extends from 68.2 to 78.7 percentage points. Its width reflects statistical uncertainty under the analysis assumptions. It does not capture every possible source of uncertainty, such as limitations in measurement, missing outcomes, or choices in the analysis plan.

Randomization is intended to support fair comparison by assigning participants to groups without choosing assignment according to their expected outcomes. Double masking is intended to reduce the influence of knowledge of assigned treatment on care and outcome assessment. The registry identifies the trial as randomized and double-blind, but does not report detailed procedures for allocation concealment, maintenance of masking, stratification, or handling of deviations.

11. Confidence Intervals and Precision

The primary estimates are accompanied by 95% confidence intervals. For the group response percentages, the registry reports 6.3 for placebo, with an interval from 1.8 to 10.7; 76.3 for secukinumab, with an interval from 72.4 to 80.3; and 79.7 for mirikizumab, with an interval from 77.0 to 82.3. These intervals show the uncertainty around each estimated group percentage under the registry's methods.

For the sponsor-reported mirikizumab-versus-placebo risk difference, the estimate is 73.5 percentage points and the 95% confidence interval runs from 68.2 to 78.7. The interval is compatible with a range of positive absolute differences, rather than a single known effect. Precision is about the range of plausible estimates under the statistical procedure, not certainty about what any individual participant will experience.

The unadjusted re-calculated risk difference has a 95% confidence interval from 68.2 to 78.6. Its slight variation from the sponsor-reported interval is consistent with the use of a different calculation. The sponsor's own analysis takes precedence for reporting the sponsor result. Intervals from different methods should not be treated as interchangeable merely because their endpoints are close.

Confidence intervals do not address all limitations. They do not account for possible bias from missing data, choices in endpoint definition, deviations from the intended analysis, or selective reporting. Information about the missing-data approach and full statistical plan is not reported in the registry record. Likewise, the intervals describe the specified Week 16 outcome and should not be read as intervals for long-term response or other outcomes.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size illustrations use the observed effect as a reference and show hypothetical planning requirements under stated assumptions. For these binary outcomes, the figures are participants per arm, not total events. The illustrations assume two-sided significance level 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set at the stated fraction of the observed effect. The trial's own original design assumptions and sample-size justification are not reported in the registry record.

The 80% power column gives the planned number of participants per arm for a design that, under the illustration's assumptions and specified effect, would have an 80% chance of detecting that effect at the stated significance level. The 90% power column uses a higher target probability of detecting the specified effect. These are design calculations for hypothetical studies, not guarantees about a future result.

Rows based on a smaller fraction of the observed effect represent a more modest difference to detect. Smaller effects generally require more participants to distinguish them from random variation with the same target power and significance level. The numbers depend on the assumed event rates, allocation, test approximation, and effect used in the illustration, so they should not be transferred directly to a different trial without reconsidering those assumptions.

This is not observed power. It is a planning illustration based on the effect estimate after the trial results are known, not a measure of the probability that the completed trial's conclusion is correct. The registry record does not report whether these illustration assumptions resemble the sponsor's original design calculations.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.062; treatment proportion p₁ = 0.763; average p̄ = 0.413.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6963 = 1.3647.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.4891 = 0.4116.
4. n = (1.3647 + 0.4116)² / (0.7009)² = 6.4, rounded up to 7 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.0625                          # control proportion
p1 <- 0.763392857142857                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(3535194)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 7 (80% power), 9 (90% power)
 75% of observed effect: n per arm = 12 (80% power), 15 (90% power)
 50% of observed effect: n per arm = 22 (80% power), 29 (90% power)
power.prop.test: 6.4 
Simulated power at n = 7 per arm: 0.858 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The registry reports a sponsor analysis for mirikizumab versus placebo using the Cochran-Mantel-Haenszel method. The reported risk difference is 73.5 percentage points, with a 95% confidence interval from 68.2 to 78.7 and p < 0.001. This is the result to use when describing the sponsor's recorded primary analysis.

The unadjusted re-calculation based on the posted group summaries gives a risk difference of 73.4 percentage points, with a 95% confidence interval from 68.2 to 78.6. It is a simple summary-statistic calculation and does not reproduce the named sponsor method. Its closeness to the sponsor estimate supports the same broad description of the observed contrast, but does not make it the sponsor's analysis.

The registry's analysis listing specifies the groups, method, estimate, interval, and p-value, but does not give enough detail to reconstruct the full analysis procedure, including any stratification details. The re-calculation should therefore be treated as a transparent descriptive check, not a correction to the sponsor analysis. The registry record does not report a sponsor analysis for the primary secukinumab-versus-placebo comparison in the registry record.

15. Multiplicity, Missing Data and Analysis Populations

The registry lists numerous outcome measures, including a primary outcome and multiple secondary outcomes. Testing multiple outcomes can increase the chance of at least one apparently notable result arising by chance if each test is considered separately. In general, a prespecified testing hierarchy or multiplicity adjustment can help control that concern. The registry record does not report whether such a strategy was used, how endpoints were ordered, or whether secondary p-values were adjusted. The reported secondary p-values should therefore be read with caution and should not automatically be interpreted as confirmatory findings.

The primary analysis population is described as all randomized participants. However, the registry entries available do not specify the analysis set in more detail, explain exclusions after randomization, or describe the handling of missing Week 16 observations. Missing-data choices can affect a binary response percentage if outcome status is unknown for some participants. The registry record does not report whether missing outcomes were counted as nonresponse, imputed, or handled by another method.

The record identifies a randomized, double-blind, parallel design, but does not report the full statistical analysis plan, interim analyses, detailed stratification factors, or procedures for protocol deviations. These points matter because they define how the posted estimate relates to the planned analysis and how robust the inference is to analytic choices. Their absence in the registry record does not establish that the procedures were absent from the trial; it means they are not reported in the registry record.

16. 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: cataract (5.6%), radius fracture (5.6%), pustular psoriasis (5.6%), angina pectoris (5.3%), irritable bowel syndrome (5.3%).

The registry reports serious adverse events, other adverse events, and deaths by group and study period. During induction, the listed serious adverse event counts were 0 among 112 participants in the placebo group, 11 among 448 in the secukinumab group, and 15 among 904 in the mirikizumab group. The Japan GPP/EP induction group is reported separately, with 2 serious adverse events among 19 participants. One death is listed in the 250mg mirikizumab Q4W induction group; the other listed groups show no deaths.

These are counts and denominators for the period-specific groups, not an adjusted comparison of safety risks. Groups and denominators differ, and later maintenance and follow-up entries represent different periods and populations. The record lists serious adverse event terms with percentages, but the registry entries available do not state the denominator or analysis basis for those term percentages. They should not be read as a complete accounting of all events or as evidence that a particular event was caused by treatment.

Adverse-event summaries are descriptive. The registry does not provide a statistical comparison or detailed event narratives in the registry record. No conclusion about comparative safety should be drawn from these counts alone.

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

The primary result describes a substantial difference in the observed Week 16 sPGA response percentages between the mirikizumab group and placebo in this randomized study. The sponsor-reported analysis gives a 73.5 percentage-point risk difference, with a 95% confidence interval from 68.2 to 78.7 and p < 0.001. The outcome is a specific response rule requiring an sPGA score of 0 or 1 and at least a 2-point improvement from baseline.

The result does not mean that every participant responded or that all participants experienced the same degree of change. A percentage compresses individual outcomes into a group summary. It also does not establish the duration of response, because the primary endpoint is reported at Week 16. The secondary outcomes address additional domains, but they do not answer every question about symptoms, quality of life, or longer-term outcomes.

The primary comparison against placebo does not establish how mirikizumab compares directly with secukinumab. Although the registry reports Week 16 group percentages for both active groups, the sponsor-reported primary analysis listed in the registry record is mirikizumab versus placebo. An apparent difference or similarity between two arm percentages is not a substitute for a direct, prespecified comparative analysis.

Statistical evidence also does not resolve the importance of all possible sources of uncertainty. The registry does not report detailed missing-data procedures, multiplicity handling, or the full analysis plan in the registry record. The results should be understood as evidence about the specified endpoint in the trial population and setting, not as a complete statement about treatment effects in every population, time period, or outcome.

18. Why This Trial Matters Statistically

OASIS-2 offers a useful example of how a responder endpoint can be interpreted alongside absolute group percentages, a risk difference, and a confidence interval. The endpoint's rule is clinically legible: it requires both a low physician-assessed severity score and improvement from baseline. That makes the response measure more informative than a final score threshold alone, while still simplifying a graded assessment to a binary outcome.

The registry also illustrates why the method attached to an estimate matters. A sponsor-reported Cochran-Mantel-Haenszel analysis and an unadjusted re-calculation from summary statistics can yield nearby but not identical estimates. Reporting both distinctly prevents a descriptive check from being mistaken for the trial's own analysis. The confidence interval adds information about precision that a p-value alone does not provide.

Finally, the trial has multiple outcome measures, distinct treatment schedules, and adverse-event summaries spanning induction, maintenance, and follow-up periods. These features make careful attention to population, endpoint, time point, and analysis method essential. The posted primary result is one part of a broader evidence record; secondary outcomes and safety counts provide context but require their own interpretation. The registry's missing detail about multiplicity, missing data, and the original planning assumptions also illustrates why statistical significance is not the same as a complete account of evidential strength.

19. 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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

The registry information available for these results leaves several trial-specific questions unanswered. It does not describe the original sample-size justification or the assumptions used to plan the trial. The sample-size illustrations are retrospective planning examples based on observed effects and should not be mistaken for the sponsor's original design calculations.

The reported primary analysis is for mirikizumab versus placebo. The registry also provides arm-level Week 16 estimates for secukinumab, but the registry entries available do not list a sponsor-reported primary comparison between secukinumab and placebo or between the two active treatments. The arm percentages alone do not supply a formal direct comparison.

The record lists total enrollment of 1484 and primary outcome denominators of 112, 448, and 905, but does not explain the denominator relationship or provide a detailed flow of participants through the analysis. The safety summaries use different denominators across periods and groups. The detailed handling of missing outcomes and the exact analysis populations beyond the primary population description are not reported in the registry record.

Multiplicity procedures, interim analyses, detailed stratification, and the full statistical analysis plan are also not reported in the registry record. The results concern Week 16 and cannot establish durability. These limitations describe what cannot be determined from the registry information available; they do not imply that unreported procedures were not conducted.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: A Study to Assess if Mirikizumab is Effective and Safe Compared to Secukinumab and Placebo in Moderate to Severe Plaque Psoriasis (OASIS-2) — NCT03535194.
• Registry record last updated 2021-03-30; status last verified 2020-08.
• Results first posted 2021-03-30.
• 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.

23. Record Summary

OASIS-2 is a completed Phase 3, randomized, double-blind, parallel-group study of mirikizumab, secukinumab, and placebo in moderate-to-severe plaque psoriasis. The registry reports total enrollment of 1484.

The primary outcome is the percentage of participants meeting the sPGA response definition at Week 16: a score of 0 or 1 and at least a 2-point improvement from baseline. The sponsor-reported mirikizumab-versus-placebo risk difference is 73.5 percentage points, with a 95% confidence interval from 68.2 to 78.7 and p < 0.001, using the Cochran-Mantel-Haenszel method.

The registry lists multiple secondary outcomes and period-specific adverse-event summaries. Detailed information about multiplicity, missing-data handling, and the original sample-size justification is not reported in the registry record.