A Safety and Efficacy Study of Tralokinumab in Adults With Asthma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Safety and Efficacy Study of Tralokinumab in Adults With Asthma (NCT01402986), a randomized phase 2 study. The primary outcome is Annual Asthma Exacerbation Rate (AER).

2. Clinical Question

The study focused on exacerbations, defined in the registry as worsening asthma symptoms that remained troublesome after rescue medication and led to systemic corticosteroid use or an increase in a stable maintenance dose for at least 3 consecutive days. The definition also included participant-initiated systemic corticosteroids for at least 3 consecutive days. Events were treated as resolved after the specified interval following the last corticosteroid dose; a later course could count as a separate event. The primary endpoint therefore represents a rate of qualifying events over follow-up, rather than a simple count of participants who ever experienced an exacerbation.

The comparison is between each active dosing schedule and pooled placebo, not a direct comparison of the two tralokinumab schedules. Results can describe the observed rate estimates and their precision in this study, but they do not establish that the schedules are equivalent or that any difference is clinically important.

3. Trial Design

This completed Phase 2b study was randomized, double-blind, and quadruple-masked, with a parallel-group model. The registry reports enrollment of 689 participants. The study began in 2011-08, and primary completion was recorded in 2013-06. Adults with uncontrolled, severe asthma were studied, with the stated purpose of evaluating tralokinumab added to standard asthma medication.

The four regimens were matching placebo Q2W, tralokinumab 300 mg Q2W, matching placebo Q2/4W, and tralokinumab 300 mg Q2/4W. In Cohort 1, injections were given every 2 weeks for a total of 26 doses up to 50 weeks. In Cohort 2, injections were given every 2 weeks for 12 weeks and then every 4 weeks for 38 weeks, for a total of 16 doses. The registry’s primary endpoint results combine the two placebo arms as Placebo Total, while retaining separate results for each tralokinumab schedule.

The primary outcome timeframe runs from Week 1 up to Week 53. The primary population is described as intent-to-treat and includes all randomized participants. The reported primary arm counts are 151 for Placebo Total, 150 for the Q2W tralokinumab regimen, and 151 for the Q2/4W regimen. These outcome counts should be read as the counts associated with the reported endpoint, not as a replacement for the enrollment figure. Further details about randomization procedures, masking implementation, or the rationale for the enrollment target 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.

Before assignment: A total of 689 participants were screened, out of which 452 participants were randomized into this study

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The intent-to-treat (ITT) population included all participants who were randomized into the study.

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: The intention-to-treat (ITT) population included all participants who were randomized into the study.

6. Primary Endpoint

The registry lists the primary outcome as Annual Asthma Exacerbation Rate (AER), measured over Week 1 up to Week 53.

The primary endpoint is the annual asthma exacerbation rate, expressed as AER events/person-year, assessed using data up to Week 53. It measures the frequency of qualifying exacerbation events over participants’ observed time, rather than merely recording whether an individual had at least one event. That distinction matters because participants can have different follow-up time and can experience more than one qualifying event.

The registry defines an exacerbation as a progressive increase in asthma symptoms that does not resolve after rescue medication and remains troublesome, leading to systemic corticosteroid use or an increase in a stable maintenance dose for at least 3 consecutive days, or to participant-initiated systemic corticosteroids for at least 3 consecutive days. An event was considered resolved 7 days after the last oral corticosteroid dose, or 10 days after an injectable corticosteroid dose. A later corticosteroid course was considered a separate event. These rules determine which episodes contribute to the rate.

A rate endpoint is useful when the question concerns recurrent events across follow-up, because it incorporates the number of qualifying events and the person-time basis of the rate. The reported estimates are accompanied by 95% confidence intervals, which communicate uncertainty in the estimated rates. The registry reports Poisson regression rate ratios for the comparisons with placebo. The detailed covariates, model diagnostics, and handling of any over-dispersion are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports Poisson regression for the primary rate-ratio comparisons. General explanation: Poisson regression is commonly used for counts of events, particularly when an analysis accounts for the time during which events could occur. A rate ratio compares estimated event rates between groups. A value of 1 corresponds to equal rates; values below or above 1 indicate lower or higher estimated rates in the numerator group, depending on the comparison’s specified order. The registry’s reported estimates and intervals should be interpreted using the stated comparison with Placebo Total.

What does the confidence interval convey?

General explanation: a confidence interval describes statistical uncertainty around an estimate under the assumptions of the analysis. It is not a range that guarantees where the true effect lies, and it does not express the probability that the particular interval contains that effect. For the primary comparisons, the reported 95% confidence intervals include 1. This means the results are compatible with equal rates as well as with rate ratios below or above 1, within the intervals. The interval width is also important: uncertainty is not captured by looking only at the point estimate or p-value.

How should the p-values be read?

General explanation: a p-value measures how incompatible the observed data are with a specified null model, given the analysis assumptions. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of a difference. The registry reports p = 0.709 and p = 0.904 for the primary comparisons. Those values do not provide strong statistical evidence against equal rates under the fitted analyses. They should not be translated into proof of no effect or equivalence. The registry record does not report a prespecified threshold for declaring success or a detailed statistical analysis plan.

Why might event-rate models need additional attention?

General explanation: count models often rely on assumptions about how event counts vary around their expected rate. Over-dispersion occurs when observed count variation exceeds what a basic Poisson model assumes; if present and not adequately handled, uncertainty estimates can be affected. The endpoint definition, repeated events, and unequal follow-up are relevant when assessing an event-rate analysis. The registry identifies Poisson regression as the method, but model covariates, diagnostics, any adjustment for over-dispersion, and sensitivity analyses are not reported in the registry record. It is therefore not possible to assess those choices from the record alone.

What do the recalculated summaries add?

General explanation: a simple unadjusted recalculation based on posted summary statistics can offer a descriptive comparison, but it may not reproduce a trial’s prespecified model. Such calculations may not reflect covariate adjustment, analysis populations, missing-data handling, or the study’s multiplicity strategy. In the secondary material, recalculated estimates are identified as unadjusted; they should not be treated as replacements for sponsor analyses where those are reported. The registry’s primary comparisons are reported analyses, and no primary recalculation is needed to interpret them.

The sample-size illustrations use assumptions stated with those calculations: a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is a stated fraction of the observed effect. For time-to-event illustrations, the quantities are total events; for other illustrations, they are participants per arm. These are planning illustrations derived from observed effects, not observed power and not evidence that the original study was planned using those assumptions. The study’s own sample-size justification is not reported in the registry record.

10. Analyses Reported by the Sponsor

The primary endpoint comparisons in the registry are sponsor-reported Poisson regression analyses. For Q2W tralokinumab versus Placebo Total, the reported rate ratio is 0.94, with a 95% confidence interval from 0.67 to 1.31 and p = 0.709. For Q2/4W tralokinumab versus Placebo Total, the reported rate ratio is 1.02, with a 95% confidence interval from 0.71 to 1.46 and p = 0.904. These are the analyses to use when describing the registry’s primary inferential results.

Some secondary outcomes have additional simple unadjusted recalculations based on posted summary statistics. Those calculations are not substitutes for the sponsor’s own analysis and may not reflect the original model or analysis decisions. For example, the registry reports Cox regression analyses for time to first exacerbation; the recalculated summaries do not supersede those reported analyses. No sponsor analysis is listed for the EQ-5D VAS or serum concentration comparisons in the available secondary details, so recalculated results for those outcomes should be described as unadjusted comparisons rather than as trial-confirmatory findings.

The record indicates no discrepancy flag. That does not establish that every methodological detail is available for independent reproduction. The registry record does not report the full analysis plan, covariate specifications, or complete handling of missing data, so the extent to which any recalculation matches the original analytic decisions cannot be determined from the record.

11. Multiplicity, Missing Data and Analysis Populations

The primary outcome is defined for the intent-to-treat population, which the registry describes as all randomized participants. The primary arm counts reported for the rate endpoint are 151 for Placebo Total, 150 for Q2W tralokinumab, and 151 for Q2/4W tralokinumab. The registry’s description of the population clarifies the intended analysis set, but it does not by itself explain how unavailable outcome observations or incomplete follow-up were handled.

The record does not report the amount or pattern of missing primary endpoint data, reasons for missingness, imputation methods, or sensitivity analyses addressing missing data. It also does not report whether every randomized participant contributed the same amount of follow-up time to the rate calculation. These omissions limit assessment of how robust the estimates are to incomplete observation. They are not evidence that missing data were present or that a particular method was or was not used.

Multiplicity is also not described in the registry record. The primary results include comparisons of each active schedule with pooled placebo, and the study reports many secondary outcomes. Without a stated hierarchy or adjustment strategy, the extent to which the reported p-values account for the full set of comparisons is not reported in the registry record. This uncertainty is particularly relevant when interpreting isolated secondary findings, which are generally less persuasive when considered without adjustment across multiple outcomes.

The registry record does not report a detailed statistical analysis plan, interim analyses, or a sample-size justification. The planning illustrations based on observed effects are not evidence about how the trial was originally designed. The endpoint method is identified as Poisson regression, but covariate adjustment, model diagnostics, and any approach to over-dispersion are not reported. These gaps prevent a complete audit of the prespecified analysis and its assumptions. They should be treated as limits on what can be concluded from the registry record, not as proof that the trial’s analyses were inappropriate.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: asthma (6.6%), pneumonia (2.0%), cardiac failure (1.3%), road traffic accident (1.3%), tibia fracture (1.3%).

The registry reports serious adverse events affecting 21 of 151 participants in Placebo Total, 18 of 150 in the Q2W tralokinumab group, and 25 of 151 in the Q2/4W group. The figures are counts of affected participants and the corresponding group sizes, not measures of event severity beyond the registry’s serious-event classification. They do not establish that any difference between groups is attributable to treatment.

The most frequently listed serious adverse event term is Asthma at 6.6%, followed by Pneumonia at 2.0%. Cardiac failure, Road traffic accident, Tibia fracture, and Osteoarthritis are each listed at 1.3%. The registry record does not specify in these details whether terms overlap within participants, so the percentages should not be added or treated as mutually exclusive categories. Death counts are not reported in the registry record.

Safety counts need context, including duration of exposure, event definitions, severity, timing, and the method used to collect and code events. The available record does not provide enough information to determine causality or to make a complete comparative safety assessment. Counts from this study describe reported events in its groups; they do not alone establish that a regimen is safe or unsafe.

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

The primary results describe annualized exacerbation rates in the randomized groups over the period from Week 1 up to Week 53. The reported point estimates are 0.9 events/person-year for Placebo Total, 0.91 for Q2W tralokinumab, and 0.97 for Q2/4W tralokinumab. The reported rate-ratio intervals include 1 for both comparisons with placebo, and the p-values are 0.709 and 0.904. Taken together, these results do not show statistically persuasive evidence of a difference in the reported primary analyses.

That interpretation is not the same as demonstrating equivalence, proving there is no effect, or ruling out differences that could matter. Confidence intervals reflect uncertainty, and the primary intervals include a range of possible rate ratios on either side of 1. A nonsignificant result can arise when the estimated difference is small, when uncertainty is substantial, or both; the registry results alone do not establish which explanation accounts for the findings.

The endpoint is a rate of qualifying exacerbation events, not a measure of all asthma symptoms, lung function, quality of life, or the proportion of participants with any event. Secondary outcomes address some of those other domains, but they should be interpreted according to their own definitions and analyses. The study’s findings also pertain to the trial population, dosing schedules, and follow-up described in the registry; applicability to other populations or settings is not established by these data alone.

Finally, a registry result is not a complete account of every analytic decision. Details about missing data, model diagnostics, multiplicity, and the sample-size rationale are not reported in the registry record. The fairest conclusion is therefore bounded: the posted primary estimates and their uncertainty do not provide strong statistical evidence of a difference from pooled placebo, while leaving uncertainty about the size and direction of any underlying difference.

14. Why This Trial Matters Statistically

This trial illustrates why a clinical endpoint’s statistical form matters. Annualized exacerbation rate captures recurrent qualifying events over person-time, rather than reducing the outcome to whether a participant ever experienced an event. That makes the rate ratio a natural summary for the reported primary comparison, while also making interpretation dependent on event definitions, follow-up, and count-model assumptions.

It also shows why point estimates, confidence intervals, and p-values should be read together. The primary rate-ratio estimates are close to 1, but the confidence intervals extend across 1. The p-values do not offer strong evidence against equal rates, yet the intervals do not prove equivalence. A conclusion based only on whether a p-value crosses a threshold would lose information about the range of effects compatible with the data.

The study includes two active dosing schedules and a placebo comparison in which the placebo arms are pooled for the primary result. That arrangement makes the exact comparator important: the reported estimates address each active schedule versus Placebo Total, not a direct test between the active schedules. It is also a reminder that multiple outcomes and comparisons require a clear multiplicity strategy before isolated secondary findings can be treated as confirmatory.

For clinical researchers and biostatisticians, the record is useful both for its reported estimates and for the questions it leaves open. The registry identifies the population, endpoint definition, analysis method, and follow-up period, but does not report every detail needed to reconstruct the analysis. Separating the evidence that is posted from the methodological information that is not reported supports a more measured interpretation of the trial.

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.

Several trial-specific details limit interpretation. The registry reports Poisson regression for the primary rate-ratio analyses but does not describe the model covariates, any exposure-time offset, diagnostic checks, or handling of over-dispersion. These details can affect uncertainty in an event-rate analysis, but their absence from the record does not show that the analyses omitted them.

The primary comparisons pool the placebo schedules while keeping the tralokinumab schedules separate. The record does not provide a direct primary comparison between the active schedules, so the reported results cannot answer whether one active regimen differs from the other. The primary endpoint also depends on a detailed corticosteroid-based definition of exacerbation and event resolution; changing those rules could change which events count, but alternative definitions are not reported.

The registry record does not report missing-data methods, the amount of missingness, sensitivity analyses, interim analyses, the statistical analysis plan, or the sample-size justification. It also does not report a multiplicity strategy for the primary comparisons and many secondary outcomes. These gaps make it difficult to assess prespecification, robustness, and the strength of isolated secondary findings.

The enrollment figure is 689, whereas the reported primary endpoint group counts are 151, 150, and 151. The record does not explain the relationship between enrollment and those endpoint counts in the available details, so reasons for the difference should not be inferred. Likewise, deaths are not reported in the registry record. These limitations constrain interpretation but do not themselves establish bias or invalidate the posted estimates.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Safety and Efficacy Study of Tralokinumab in Adults With Asthma — NCT01402986.
• Registry record last updated 2017-04-04; status last verified 2017-03.
• Results first posted 2017-03-06.
• 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

This completed randomized, double-blind, quadruple-masked Phase 2b parallel study evaluated tralokinumab 300 mg on Q2W and Q2/4W schedules against matching placebo in adults with uncontrolled, severe asthma. The primary endpoint was annual asthma exacerbation rate from Week 1 up to Week 53, analyzed in the intent-to-treat population using Poisson regression.

The reported rate ratios versus Placebo Total were 0.94 for Q2W and 1.02 for Q2/4W; both 95% confidence intervals included 1. The registry record does not report a multiplicity strategy, missing-data methods, or a complete statistical analysis plan. Secondary outcomes and safety counts add context but do not replace the primary comparison or resolve those reporting limitations.