This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record.
1. Trial at a Glance
MATINEE was a randomized, double-blind, parallel-group phase 3 trial comparing mepolizumab 100 mg with placebo as add-on treatment in people with chronic obstructive pulmonary disease (COPD) characterized by frequent exacerbations and an eosinophil-based entry criterion. Its primary endpoint was the annualized rate of moderate or severe exacerbations up to Week 104.
| Feature | MATINEE |
|---|---|
| Phase | Phase 3 |
| Condition | Pulmonary disease, chronic obstructive (COPD) |
| Design | Randomized, parallel-group, double-masked, placebo-controlled; primary purpose treatment |
| Arms | 2: Mepolizumab 100 mg (biological) and placebo (drug) |
| Enrollment | 806 |
| Primary endpoint | Annualized rate of moderate or severe exacerbations, up to Week 104 |
| Primary analysis | Covariate-adjusted negative binomial model; rate ratio mepolizumab 100 mg / placebo |
| Analysis population | Modified intent-to-treat (mITT) |
| Dates | Start 2019-10-30; primary completion 2024-08-08 |
| ClinicalTrials.gov | NCT04133909 |
| Sponsor | GlaxoSmithKline (industry) |
2. Clinical Question
The central question was whether adding mepolizumab 100 mg to existing treatment reduces the rate of moderate or severe COPD exacerbations compared with placebo, in a population selected for a history of frequent exacerbations and an eosinophil-level criterion. Because exacerbations are recurrent events, the question is framed as a comparison of event rates over time rather than of the proportion of participants who ever have an event.
Population
Participants with COPD characterized by frequent exacerbations and an eosinophil-level criterion, as described in the registry title. The registry record does not list the eligibility thresholds among its results.
Intervention
Mepolizumab 100 mg, a biological, given as add-on treatment.
Comparator
Placebo, under double masking, given as add-on treatment.
Primary question
Is the annualized rate of moderate or severe exacerbations up to Week 104 lower with mepolizumab 100 mg than with placebo?
3. Trial Design
Mepolizumab 100 mg
- Mepolizumab 100 mg (biological)
- Added to existing COPD treatment
- Double-masked
Placebo
- Placebo (drug)
- Added to existing COPD treatment
- Double-masked
Double masking matters particularly for this endpoint. A moderate exacerbation is defined by a treatment decision (oral or systemic corticosteroids and/or antibiotics), so knowledge of the assigned arm could plausibly influence whether an episode is treated and therefore counted. Blinding protects the comparison from this kind of ascertainment bias.
4. Analysis Population and Covariate Adjustment
All efficacy analyses posted to the registry used the modified intent-to-treat (mITT) population: all randomized participants who received at least one dose of trial medication, analyzed by randomized treatment. For the patient-reported responder endpoints, only participants with baseline data available were analyzed. The analysis descriptions for those endpoints also refer to an mITT2 population, which the registry does not define in its posted analysis summaries.
| Analysis population | Definition / role |
|---|---|
| mITT | All randomized participants who received at least one dose of trial medication, analyzed by randomized treatment; used for the primary and secondary efficacy analyses. |
| mITT with baseline data | Subset of the mITT population with available baseline scores; used for the CAT, SGRQ and E-RS: COPD responder analyses. |
| Safety summary | Participants at risk: 403 (mepolizumab 100 mg) and 401 (placebo). |
The exacerbation and time-to-event models adjusted for the same set of baseline covariates:
Prior exacerbation history is usually the strongest single predictor of future exacerbations, so adjusting for it reduces unexplained between-participant variation and sharpens the treatment estimate. In a randomized trial, covariate adjustment is not primarily about correcting imbalance; it is about precision. The responder models adjusted for treatment group, smoking status, geographic region and the baseline score of the relevant questionnaire.
5. Endpoints
Primary endpoint
| Endpoint | Registry definition | Time frame |
|---|---|---|
| Annualized Rate of Moderate or Severe Exacerbations | Moderate exacerbations: clinically significant exacerbations that require treatment with oral or systemic corticosteroids and/or antibiotics. Severe exacerbations: clinically significant exacerbations that require in-patient hospitalization (≥24 hours) or result in death. | Up to Week 104 |
Secondary endpoints with posted statistical analyses
| Endpoint | Time frame | Unit / effect measure |
|---|---|---|
| Time to First Moderate or Severe Exacerbation | Assessed at Weeks 8, 16, 24, 32, 40, 48, 52, 56, 64, 72, 80, 88, 96 and 104 | Percentage of participants; hazard ratio |
| CAT responders (≥2 point reduction from baseline) at Week 52 | Baseline and Week 52 | Percentage of participants; odds ratio |
| SGRQ total score responders (≥4 point reduction from baseline) at Week 52 | Baseline and Week 52 | Percentage of participants; odds ratio |
| E-RS: COPD responders (≥2 point reduction from baseline) | Baseline and 4 weeks prior to Week 52 | Percentage of participants; odds ratio |
| Annualized Rate of Exacerbations Requiring ED Visit and/or Hospitalization | Up to Week 104 | Exacerbations per year; rate ratio |
These endpoints use three distinct data types: counts of recurrent events (analyzed as rates), a time to first event (analyzed with a hazard model), and binary responder status derived from continuous questionnaire scores (analyzed with logistic regression). Each effect measure answers a different question and cannot be directly compared in magnitude with the others.
6. Primary Result: Annualized Rate of Moderate or Severe Exacerbations
Rate ratio, mepolizumab 100 mg / placebo
95% CI: 0.66–0.94 (two-sided) · P = 0.011
Negative binomial model · mITT population · superiority hypothesis · up to Week 104
| Item | Posted value |
|---|---|
| Outcome | Annualized rate of moderate or severe exacerbations (exacerbations per year) |
| Comparison | Mepolizumab 100 mg vs placebo |
| Method | Negative binomial model with covariates of treatment group, geographic region, prior-year exacerbations (≤2, 3, ≥4 as ordinal), baseline % predicted FEV1 and smoking status; offset log(time on- and off-treatment) |
| Effect measure | Rate ratio (mepolizumab 100 mg / placebo) |
| Estimate (95% CI) | 0.79 (0.66–0.94) |
| P-value | 0.011 |
The registry's statistical analysis reports the ratio and its test rather than the arm-level adjusted annualized rates, so the absolute number of exacerbations avoided per participant-year cannot be read off this comparison alone.
What the estimate means. A rate ratio of 0.79 means that, after adjustment for the model covariates, the estimated annualized rate of moderate or severe exacerbations in the mepolizumab 100 mg arm was 79% of the rate in the placebo arm, i.e. a 21% lower estimated rate. It is a ratio of population-average event rates, estimated on the log scale and exponentiated.
What it does not mean. It does not mean that 21% of participants were spared an exacerbation, nor that each participant had 21% fewer exacerbations. Exacerbation counts are highly variable between individuals; the ratio summarizes the arm-level rate, not an individual response. It is also a relative measure: the same ratio corresponds to a larger absolute reduction in a population with a higher baseline rate.
Precision. The 95% confidence interval of 0.66–0.94 excludes 1, and its range spans estimated rate reductions of roughly 6% to 34%. The data are therefore compatible with anything from a modest to a moderately large relative reduction; the point estimate is the single best guess, not a precise value.
The p-value. P = 0.011 indicates that data this far from a rate ratio of 1 would be unusual if mepolizumab had no effect on the exacerbation rate. It says nothing about how large the effect is; a smaller p-value could arise from a bigger trial with the same rate ratio. The confidence interval, not the p-value, carries the information about magnitude.
Cautions. The negative binomial model accounts for overdispersion (participants differing in their underlying exacerbation propensity), which a Poisson model would ignore and which would make its intervals too narrow. The offset uses time on- and off-treatment, so follow-up after treatment discontinuation contributes to the analysis; the estimate therefore reflects the effect of being assigned to mepolizumab rather than the effect under perfect adherence. The mITT population excludes randomized participants who received no dose, a small departure from a strict intention-to-treat analysis.
7. Secondary Endpoint Results
Time to first moderate or severe exacerbation
Hazard ratio, mepolizumab 100 mg vs placebo
95% CI: 0.64–0.93 (two-sided) · P = 0.009
Cox proportional hazards model · mITT population · superiority hypothesis
The Cox model adjusted for treatment group, geographic region, prior-year exacerbations (≤2, 3, ≥4 as ordinal), baseline % predicted FEV1 and smoking status. A hazard ratio of 0.77 corresponds to a 23% lower estimated instantaneous rate of a first moderate or severe exacerbation in the mepolizumab arm. This endpoint discards all events after the first, so it answers a narrower question than the primary rate analysis: how long participants remained free of any exacerbation. The two estimates pointing in the same direction with similar magnitude is reassuring about consistency, but they are not independent confirmations; they are derived from overlapping events in the same participants.
The single hazard ratio summarizes the relative hazard across the whole follow-up and is most interpretable if the hazards are roughly proportional over time. The registry does not report a test of proportionality. The interval 0.64–0.93 excludes 1, and P = 0.009 again reflects compatibility with the null rather than size of effect.
Exacerbations requiring an emergency department visit and/or hospitalization
Rate ratio, mepolizumab 100 mg / placebo
95% CI: 0.43–0.96 (two-sided) · P = 0.032
Negative binomial model · mITT population · up to Week 104
The point estimate corresponds to a 35% lower estimated rate of exacerbations requiring ED care and/or hospitalization. The confidence interval is noticeably wider than for the primary endpoint (0.43–0.96 versus 0.66–0.94), which is expected: these more severe events are rarer, and fewer events mean less information and less precision. The upper limit lies close to 1, so the data remain compatible with a small effect. The registry notes that estimates were based on weighting each level of the class variables by their observed proportions, which produces marginal (population-averaged) rates rather than rates for a single reference covariate profile.
Patient-reported responder endpoints at Week 52
| Responder definition | Odds ratio, mepolizumab vs placebo | 95% CI | P-value |
|---|---|---|---|
| CAT, ≥2 point reduction from baseline | 0.81 | 0.60–1.09 | 0.161 |
| SGRQ total score, ≥4 point reduction from baseline | 1.17 | 0.87–1.57 | 0.291 |
| E-RS: COPD, ≥2 point reduction from baseline | 0.82 | 0.60–1.12 | 0.209 |
All three odds ratios have confidence intervals that include 1, and none of the p-values is below conventional thresholds. The point estimates do not point in a consistent direction: the SGRQ odds ratio is above 1, while the CAT and E-RS: COPD odds ratios are below 1. The appropriate reading is that these analyses did not show a difference in the odds of achieving the responder thresholds; it is not evidence that mepolizumab has no effect on symptoms or health status, because the intervals are wide enough to include modest effects in either direction.
The display places different effect measures on one ratio axis purely to compare precision and direction relative to 1. Rate ratios, hazard ratios and odds ratios are not interchangeable, and their magnitudes should not be compared with each other directly.
8. Safety: Serious Adverse Events
| Arm | Participants with ≥1 serious adverse event | Participants at risk |
|---|---|---|
| Mepolizumab 100 mg | 101 | 403 |
| Placebo | 115 | 401 |
The registry reports 101 of 403 participants with a serious adverse event in the mepolizumab 100 mg arm and 115 of 401 in the placebo arm. No formal statistical comparison of serious adverse events is posted, which is typical: safety tables are descriptive, and trials are rarely powered to test differences in specific adverse events. In COPD, serious adverse events include hospitalized exacerbations, so the serious adverse event count partly overlaps with the efficacy outcome and should not be read as a separate, independent signal.
9. Statistical Methodology
Negative binomial regression for exacerbation rates
The primary and ED/hospitalization endpoints are counts of events accumulated over different lengths of follow-up. A negative binomial model treats each participant's count as arising from a Poisson process whose rate varies between participants according to a gamma distribution. This extra-Poisson variation (overdispersion) is characteristic of exacerbation data: some participants have many events and many have none.
Here Yi is the number of exacerbations, ti the follow-up time (on- and off-treatment) entering as an offset, Xi the baseline covariates and k the dispersion parameter. The rate ratio is exp(β1), reported as 0.79 for the primary endpoint.
Why the offset matters
Participants are followed for different lengths of time, for example because of withdrawal. Including log(follow-up time) as an offset converts the model from one for counts to one for rates, so a participant followed for one year is compared fairly with one followed for two. Because the offset includes off-treatment time, events after stopping study drug are still counted, consistent with a treatment-policy view of the effect.
Cox proportional hazards model
For time to first moderate or severe exacerbation, the Cox model estimates the ratio of hazards between arms without specifying the shape of the baseline hazard, adjusting for the same covariates as the rate model. Participants without an exacerbation are censored at the end of their follow-up and contribute information up to that point.
An HR below 1 indicates a lower estimated instantaneous rate of a first exacerbation among participants still exacerbation-free. It is not a relative risk, and it is not the proportion of participants who avoid an exacerbation.
Logistic regression for responder endpoints
For CAT, SGRQ and E-RS: COPD, each participant was classified as a responder or not using a prespecified minimum change from baseline. Logistic regression then estimated the odds ratio of being a responder, adjusted for treatment group, smoking status, geographic region and the baseline score. Adjusting for the baseline score is important because participants with worse baseline scores have more room to improve by a fixed number of points.
Dichotomizing a continuous score loses information, which is one reason responder analyses often have wide confidence intervals.
Modified intent-to-treat analysis
Participants were analyzed according to randomized treatment, preserving the comparability created by randomization. The modification, requiring at least one dose, is common in double-blind trials, where dosing status is unlikely to depend on the assigned arm; it usually excludes few participants and has little effect on the comparison.
10. Statistical Methods Explained
Why was a negative binomial model used instead of a t-test or a Poisson model?
Exacerbations are counts, not continuous measurements, and follow-up time differs between participants, so comparing mean counts with a t-test would ignore exposure and the skewed distribution. A Poisson model handles counts and exposure but assumes the variance equals the mean. Exacerbation counts are overdispersed, and a Poisson model would understate uncertainty, producing confidence intervals that are too narrow and p-values that are too small. The negative binomial model adds a dispersion parameter to fix this.
What does a rate ratio of 0.79 mean in practical terms?
It means the adjusted annualized rate of moderate or severe exacerbations was estimated to be 21% lower with mepolizumab 100 mg than with placebo. To translate that into exacerbations avoided per year, one needs the placebo-arm rate: the same relative reduction yields more avoided events in a population with a higher underlying rate.
Why do the primary rate ratio (0.79) and the time-to-first-event HR (0.77) differ?
They measure different things. The rate ratio uses every exacerbation over follow-up; the hazard ratio uses only the first. A treatment that delays the first event but affects later events differently could produce different values. Here the two are close, suggesting that the relative effect is broadly similar whether measured by first events or by all events.
Why was the ED/hospitalization rate ratio (0.65) smaller but less precise?
A smaller ratio indicates a larger estimated relative reduction for the more severe events. But these events are less frequent, and the precision of a rate ratio depends mainly on the number of events. With fewer events, the 95% CI widens to 0.43–0.96, so the data are compatible with anything from a large reduction to a small one.
Why do the responder odds ratios not show a difference when exacerbations do?
Symptom and quality-of-life questionnaires, dichotomized at a threshold change, are a different outcome with higher measurement variability and less statistical information than a count of clinical events over two years. The CAT (0.81, 95% CI 0.60–1.09), SGRQ (1.17, 0.87–1.57) and E-RS: COPD (0.82, 0.60–1.12) intervals all include 1. That is an absence of evidence for a difference in responder odds, not evidence of absence.
Is a p-value of 0.011 stronger evidence of benefit than a p-value of 0.032?
Only in the narrow sense of being less compatible with the null hypothesis. Neither p-value measures the size of the effect. The ED/hospitalization endpoint (P = 0.032) actually has the larger estimated relative effect but a less precise estimate. Effect size should be judged from the estimate and its confidence interval.
11. Limitations
- Relative measures only: the posted analyses report ratios. Without the arm-level adjusted rates, the absolute number of exacerbations avoided cannot be judged from the ratio alone.
- Selected population: the trial enrolled people with frequent exacerbations and an eosinophil criterion. Results apply to that population; they do not establish the effect in COPD without these features.
- Endpoint definition depends on treatment decisions: moderate exacerbations are defined by prescription of corticosteroids and/or antibiotics, so local prescribing practice influences what counts as an event. Blinding and adjustment for region reduce but do not remove this source of variation.
- Multiplicity: the registry does not describe how type I error was controlled across secondary endpoints, so their nominal p-values should be read cautiously.
- Proportional hazards: the Cox hazard ratio assumes a roughly constant relative hazard over time, which the registry does not report testing.
- Responder dichotomization: converting continuous questionnaire scores to responder status reduces statistical power and depends on the chosen threshold.
- Missing data: the registry does not describe how missing questionnaire data were handled beyond requiring baseline data; the responder analyses may therefore be sensitive to how participants without Week 52 data were classified.
- Unreported detail: the registry's posted analyses do not include subgroup results, so possible heterogeneity of the treatment effect cannot be assessed.
12. Why This Trial Matters Statistically
MATINEE is a useful teaching case for recurrent-event endpoints. It shows how a single clinical question, whether a treatment reduces exacerbations, can be approached with three different models, each targeting a different estimand, and how the results of those models should be read side by side rather than as interchangeable.
| Concept | How it appears in MATINEE |
|---|---|
| Negative binomial regression | Primary analysis of the annualized exacerbation rate, allowing for overdispersion |
| Offset for exposure time | log(time on- and off-treatment) converts counts to rates and follows a treatment-policy approach |
| Rate ratio | 0.79 for moderate/severe and 0.65 for ED/hospitalization exacerbations |
| Cox model and hazard ratio | Time to first moderate or severe exacerbation, HR 0.77 |
| Logistic regression and odds ratio | CAT, SGRQ and E-RS: COPD responder analyses |
| Covariate adjustment | Region, prior exacerbations, baseline FEV1, smoking status and baseline scores |
| Confidence intervals | Precision differs by event frequency: narrower for all exacerbations, wider for severe ones |
| Modified intent-to-treat | Analysis by randomized arm among those receiving at least one dose |
| Multiplicity | Several secondary endpoints tested, with nominal p-values requiring cautious reading |
13. Related Tutorials
Learn more about the methods used in this trial:
14. Related Calculators
15. Sources
- ClinicalTrials.gov: NCT04133909. Mepolizumab as Add-on Treatment IN Participants With COPD Characterized by Frequent Exacerbations and Eosinophil Level (MATINEE).
Continue exploring Clinical Biostats
Connect the endpoints and methods in this trial to deeper statistical tutorials and to calculators for count, time-to-event and binary outcomes.
16. Record Summary
MATINEE compared mepolizumab 100 mg with placebo in 806 enrolled participants with COPD characterized by frequent exacerbations and an eosinophil criterion. The primary negative binomial analysis estimated a rate ratio of 0.79 (95% CI 0.66–0.94; P = 0.011) for moderate or severe exacerbations up to Week 104, supported by a hazard ratio of 0.77 (0.64–0.93; P = 0.009) for time to first exacerbation and a rate ratio of 0.65 (0.43–0.96; P = 0.032) for exacerbations requiring ED care and/or hospitalization. Responder analyses for CAT, SGRQ and E-RS: COPD produced odds ratios with confidence intervals including 1. The most useful reading combines relative effects, their uncertainty intervals, the estimand each model targets and the design features, blinding, covariate adjustment and a treatment-policy offset, that shape causal interpretation.