A Study to Evaluate the Efficacy and Safety of Astegolimab in Participants With Chronic Obstructive Pulmonary Disease: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study to Evaluate the Efficacy and Safety of Astegolimab in Participants With Chronic Obstructive Pulmonary Disease (NCT05037929), a randomized phase 2 study. The primary outcome is Annualized Rate of Moderate and Severe COPD Exacerbations Over the 52-Week Treatment Period.

2. Clinical Question

3. Trial Design

This was a Phase IIb, randomized, double-blind, placebo-controlled, multicenter study with a parallel-group design. The registry record lists 1,334 participants as enrolled and the trial status as completed. It began on 2021-10-05, and primary completion was recorded as 2025-02-24.

Participants were assigned to one of three groups: astegolimab every 2 weeks, astegolimab every 4 weeks using alternating astegolimab and placebo injections, or placebo every 2 weeks. The study description places these injections alongside standard-of-care COPD maintenance therapy. The stated population consisted of former or current smokers with COPD and a history of frequent exacerbations.

The primary analysis used the modified intent-to-treat population, defined in the record as randomized participants who received at least one dose of study drug. Participants remained grouped according to their randomized assignment. The number analyzed for an outcome was the number with data available for that analysis. For the primary endpoint, the reported group sizes were 433 for astegolimab Q2W, 437 for astegolimab Q4W, and 431 for placebo.

The registry record identifies the study as randomized and double-masked, but details such as the randomization procedure, allocation concealment, masking roles, site count, and planned stratification factors are not reported in the registry record. The protocol’s original sample-size rationale and the details of any interim monitoring are also not reported in the registry record. These omissions limit how fully the design and conduct can be reconstructed from registry information 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.

Before assignment: Participants were randomized in a 1:1:1 ratio to 1 of 3 treatment arms to receive astegolimab or placebo. After completing the 52-week treatment, eligible participants had the option to participate in open-label extension (OLE) study (NCT05878769) to receive treatment with open-label astegolimab or enter an additional treatment period to continue the same treatment as the 52-week treatment period. Participants who chose none of the above options entered the 12-week safety follow-up (SFU) period.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Modified intent-to-treat (mITT) population included all randomized participants who received at least 1 dose of study drug, with participants grouped according to the treatment assigned at randomization. Overall number analyzed is the number of participants with data available for analysis.

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: Intent-to-treat (ITT) population included all randomized participants, whether or not the participant received the assigned treatment, with participants grouped according to the treatment assigned at randomization.

6. Primary Endpoint

The registry lists the primary outcome as Annualized Rate of Moderate and Severe COPD Exacerbations Over the 52-Week Treatment Period, measured over Baseline up to Week 52.

The primary endpoint was the annualized rate of moderate and severe COPD exacerbations from baseline through Week 52, expressed as exacerbations per patient-year. It captures recurrent events during follow-up while accounting for how long each participant contributed time at risk. The registry’s definition of time at risk runs from first study-drug administration to study completion or discontinuation during the 52-week treatment period, converted to years using 365.25 days.

A moderate exacerbation was defined as new or increased COPD symptoms that led to systemic corticosteroid treatment for at least 3 days at a dose greater than 10 milligrams per day of prednisolone equivalent, and/or antibiotics. A severe exacerbation was defined as new or increased COPD symptoms leading to hospitalization for more than 24 hours or death. The record describes the unadjusted rate as total qualifying exacerbations divided by total patient-years at risk, and says adjusted rates were estimated with negative binomial regression.

As a general statistical point, an event rate can be more informative than a simple proportion when participants may experience multiple events and have different amounts of follow-up. It expresses event frequency relative to exposure time. The outcome therefore addresses the burden of recurrent exacerbations over the treatment period, not simply whether a participant experienced at least one event. The registry record does not report a separate clinical threshold for interpreting the size of a rate difference.

7. Results Posted in the Registry

• Astegolimab Q2W: 1.11 versus 1.31 (exacerbations per patient-year) on control; rate ratio 0.84 (95% CI 0.75–0.95, approximate, Poisson model); p ≈ 0.006.
• Astegolimab Q4W: 1.22 versus 1.31 (exacerbations per patient-year) on control; rate ratio 0.93 (95% CI 0.83–1.05, approximate, Poisson model); p ≈ 0.225.

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.

Annualized Rate of Moderate and Severe COPD Exacerbations Over the 52-Week Treatment Period in Participants With Low Baseline Blood Eosinophil Level (< 300 Cells/uL)

• Endpoint type: Event rate: events per unit of follow-up, compared as a rate ratio.
• Test: Poisson rate ratio, based on the estimated number of events and follow-up time.
• Result:
  • Astegolimab Q2W: 1.12 versus 1.29 (exacerbations per patient-year) on control; rate ratio 0.87 (95% CI 0.76–0.99, approximate, Poisson model); p ≈ 0.032.
  • Astegolimab Q4W: 1.21 versus 1.29 (exacerbations per patient-year) on control; rate ratio 0.93 (95% CI 0.82–1.06, approximate, Poisson model); p ≈ 0.270.
• Interpretation:
  • The 95% confidence interval excludes no difference (a ratio of 1), so the event rate is statistically lower for Astegolimab Q2W than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval includes no difference (a ratio of 1), so these data do not show a statistically significant difference between Astegolimab Q4W and the control. The interval gives the range of effects that remain compatible with the data.

Time to First Moderate or Severe COPD Exacerbation During the 52-Week Treatment Period

• Endpoint type: Time to event: compared as a hazard ratio.
• Test: Hazard ratio as reported by the sponsor (Log Rank); it was not recalculated.
• Result:
  • Astegolimab Q2W vs Placebo: hazard ratio 0.88 (95% CI 0.74–1.06), reported p = 0.169 (as reported in the registry).
  • Astegolimab Q4W vs Placebo: hazard ratio 0.95 (95% CI 0.79–1.13), reported p = 0.566 (as reported in the registry).
• Interpretation:
  • The 95% confidence interval includes no difference (a ratio of 1), so these data do not show a statistically significant difference between Astegolimab Q2W vs Placebo and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference (a ratio of 1), so these data do not show a statistically significant difference between Astegolimab Q4W vs Placebo and the control. The interval gives the range of effects that remain compatible with the data.

Absolute Change From Baseline in Health-related Quality-of-life (HRQoL) at Week 52, as Assessed Through the St. George's Respiratory Questionnaire-COPD (SGRQ-C) Total Score

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • Astegolimab Q2W: mean -6.69 versus -4.89 on control; difference -1.80 (95% CI -3.93 to 0.33), standardized effect d = -0.13; z-test p = 0.097.
  • Astegolimab Q4W: mean -6.38 versus -4.89 on control; difference -1.50 (95% CI -3.62 to 0.63), standardized effect d = -0.10; z-test p = 0.167.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Astegolimab Q2W and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Astegolimab Q4W and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes address several related but distinct aspects of COPD: recurrent exacerbation rates in participants with low baseline blood eosinophil levels, time to a first moderate or severe exacerbation, health-related quality of life, lung function, respiratory symptoms, severe exacerbations, and physical function. The registry lists 12 secondary outcomes, but detailed numerical results are not available in the registry record for every listed measure.

Among the secondary results with estimates, the Q2W low-eosinophil rate comparison has a sponsor-reported rate ratio of 0.867 and a 95% confidence interval of 0.726 to 1.036; the Q4W interval is 0.782 to 1.108 around an estimate of 0.931. For time to first exacerbation, the reported hazard ratios are 0.88 for Q2W and 0.95 for Q4W, and both intervals span 1. The SGRQ-C adjusted mean differences are -1.803 for Q2W and -1.495 for Q4W, with both reported intervals spanning 0. These patterns do not provide uniformly precise evidence across the secondary measures.

The secondary results relate to the primary outcome by examining a subgroup, timing of the first event, and other clinical or functional dimensions. They are not substitutes for the primary recurrent-event endpoint, and their measures cannot be treated as if they answer the same question. The overall direction of some estimates may appear similar to the primary comparison, but uncertainty remains and the results do not establish a consistent effect across all outcomes.

Unadjusted secondary findings carry less weight when many outcomes are examined because the chance of at least one apparently notable result can increase across multiple tests. The registry record does not report a multiplicity adjustment or a hierarchy for the secondary analyses. The unreported estimates for other listed outcomes should not be inferred from the results that are posted.

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

• Annualized Rate of Moderate and Severe COPD Exacerbations Over the 52-Week Treatment Period in Participants With Low Baseline Blood Eosinophil Level (< 300 Cells/uL)
• Time to First Moderate or Severe COPD Exacerbation During the 52-Week Treatment Period
• Absolute Change From Baseline in Health-related Quality-of-life (HRQoL) at Week 52, as Assessed Through the St. George's Respiratory Questionnaire-COPD (SGRQ-C) Total Score
• Percentage of Participants With Improvement in HRQoL at Week 52, as Assessed Through SGRQ-C Total Score
• Absolute Change From Baseline in Post-bronchodilator Forced Expiratory Volume in 1 Second (FEV1) (Liters) at Week 52
• Absolute Change From Baseline in Evaluating Respiratory Symptoms in COPD (E-RS:COPD) Total Score at Week 52
• Annualized Rate of Severe COPD Exacerbations Over the 52-week Treatment Period
• Absolute Change From Baseline in Five-repetition Sit-to-stand (5STS) Time (Seconds) at Week 52

9. Statistical Interpretation

10. Statistical Methods Explained

How an annualized rate works

An event rate relates the number of events to accumulated time at risk. Unlike a participant-level outcome that records only whether an event occurred, an event-rate analysis can include repeated exacerbations for the same participant. The annualized rate expresses that frequency on a patient-year scale. The registry record says its unadjusted rate was calculated from the total qualifying events and total patient-years at risk, with time at risk based on days from first administration until completion or discontinuation within the treatment period.

Annualization makes rates interpretable on a common exposure scale, but it relies on the way exposure time and event counts are defined. It does not mean that every participant was observed for exactly the same duration. The endpoint’s treatment window was baseline through Week 52, and the record specifies how follow-up time was converted into years.

Why negative binomial regression is used

The sponsor used negative binomial regression for the adjusted primary rate analysis. As a general statistical explanation, count outcomes can vary more between participants than a basic Poisson model expects; this is called over-dispersion. A negative binomial model can allow this extra variability. Rate models can also account for differing exposure time, and adjustment can incorporate model terms specified by the analysis plan. The particular covariates, offset specification, and other model details are not reported in the registry record.

The posted adjusted rate ratios and confidence intervals are the sponsor’s model-based results. They are not obtained simply by dividing the two displayed rates. The recalculated comparisons are simple, unadjusted approximations from posted summaries. They use a different approach and should be treated as a check on the scale and direction of the comparison, not as a replacement for the sponsor’s analysis. Since the registry record flags a discrepancy, the sponsor’s own analysis takes precedence.

What the rate ratio means

A rate ratio compares two event rates. A ratio of 1 indicates equal rates under the comparison; a ratio below 1 indicates a lower estimated rate in the first group, and a ratio above 1 indicates a higher estimated rate. A confidence interval describes a range of values compatible with the model and observed data under its assumptions. For a rate ratio, an interval that includes 1 does not rule out equal rates at the confidence level used. The interval’s width also conveys precision: broader intervals allow a wider range of plausible effects.

The sponsor reports separate comparisons of each astegolimab schedule with placebo. They should not be read as a direct comparison of the two dosing schedules. A formal between-schedule comparison is not reported in the registry record. In addition, the endpoint combines moderate and severe exacerbations, so the primary estimate does not separately quantify either category.

How to read the secondary analyses

The secondary outcomes use different statistical scales. A time-to-first-event outcome measures time until a participant’s first qualifying exacerbation and is summarized with a hazard ratio in the posted analyses. A hazard ratio compares the instantaneous event rates over follow-up under the model; it is not the same as a ratio of annualized event counts. The posted log-rank results include confidence intervals, which can be read against 1 as the no-difference reference for a hazard ratio.

The health-related quality-of-life outcome is a change in SGRQ-C total score. Its posted group summaries are mean changes, and the sponsor’s MMRM analysis reports differences in adjusted mean change from baseline. For a mean difference, 0 is the no-difference reference. As general statistical context, a confidence interval spanning 0 leaves uncertainty about the direction and size of the between-group difference. The registry record does not give a threshold for interpreting the clinical importance of these score changes.

These methods address distinct questions and use different assumptions. Event-rate models address recurrent counts and exposure; time-to-event methods account for timing of the first event; and MMRM analyzes repeated continuous measurements. Estimates across these endpoints are not interchangeable, and nominal results across multiple outcomes require cautious interpretation when the multiplicity plan is not reported.

11. Confidence Intervals and Precision

The sponsor-reported primary rate ratio for astegolimab Q2W versus placebo was 0.845, with a 95% confidence interval of 0.715 to 0.998. This interval is relatively close to the no-difference reference of 1 at its upper end. The estimate therefore has limited separation from that reference, even though the reported interval falls just below it. For astegolimab Q4W versus placebo, the rate ratio was 0.930, with a 95% confidence interval of 0.789 to 1.095. This wider span across 1 expresses uncertainty that includes both lower and higher rates than placebo.

A confidence interval is not a guarantee that the true value lies in the displayed range. In general, it is a measure of sampling uncertainty under the analysis model and its assumptions. A narrower interval indicates more precise estimation than a wider interval, while an interval crossing the null value signals that the data do not sharply distinguish the comparison from no difference at the stated confidence level. Precision and clinical importance are separate questions; the registry record does not report a threshold for a clinically important rate-ratio difference.

The secondary estimates also show uncertainty. The reported hazard-ratio intervals for time to first exacerbation span 1 for both schedules. The reported adjusted mean-difference intervals for SGRQ-C change span 0 for both comparisons. For the low-eosinophil exacerbation-rate analysis, the sponsor-reported intervals also span 1. These patterns do not establish equivalence; they indicate that the posted estimates remain compatible with a range of effects.

The recalculated primary comparison is not the basis for the sponsor’s reported interval. The registry flags a discrepancy, and the sponsor’s own adjusted model should be used as the primary inferential result. The record does not report further detail about interval construction beyond the stated analysis methods and confidence levels.

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 planning displays translate an observed effect into illustrative sample-size requirements under stated assumptions. For the rate and continuous outcomes, the figures are participants per arm; for time-to-event outcomes, they are total events, not participants. The calculations assume a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set at 100%, 75%, or 50% of the observed effect. The trial’s original design assumptions and sample-size justification are not reported in the registry record.

The 80% power column gives the number of participants per arm, or total events for time-to-event analyses, that the illustration estimates would be needed to detect the specified effect with 80% power under those assumptions. The 90% column gives the corresponding requirement for 90% power. In plain terms, power is the probability of detecting an effect of the stated size if that effect is present and the assumptions hold. It is not a statement about the probability that the treatment effect is real.

The planning values rise as the target effect is reduced: detecting a smaller effect generally requires more participants or events. For example, the primary Q2W comparison lists 456 participants per arm for 80% power at 100% of the observed effect, and 1,742 per arm at 50% of the observed effect. The time-to-first-exacerbation planning values are total events; for the Q2W comparison, the 100% effect row lists 1,922 total events for 80% power.

These are planning illustrations based on observed effects, not the trial’s own design calculation, and they are not observed power. They should not be read as a retrospective judgment about whether the trial was adequately designed or whether a result is true.

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, λ₀ and λ₁ are event rates per patient-year, and T is follow-up per participant in years. This assumes Poisson counts and equal follow-up.

Worked calculation for this trial

1. Control rate λ₀ = 1.3150; treatment rate λ₁ = 1.1100 events per patient-year; follow-up T = 1.00 years.
2. n = (1.96 + 0.842)² × (1/1.3150 + 1/1.1100) / (1.00 × [ln(0.844)]²) = 455.6, rounded up to 456 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
lambda0 <- 1.315                      # control rate, events per patient-year
lambda1 <- 1.11                      # treatment rate
tt      <- 0.996550402453047                       # follow-up per participant, years
n_per_arm <- function(power, frac = 1) {
  l1 <- lambda0 * (lambda1 / lambda0)^frac   # smaller effect = fraction of the observed log rate ratio
  ceiling(round((z_a + qnorm(power))^2 * (1 / lambda0 + 1 / l1) / (tt * log(l1 / lambda0)^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 = ",")))

# Simulation 1: Poisson counts. Simulation 2: over-dispersed counts (variance = 1.5 x mean), analysed with the matching variance.
set.seed(5037929)
n    <- n_per_arm(0.80)
reps <- 20000
m0 <- lambda0 * n * tt; m1 <- lambda1 * n * tt
x0 <- rpois(reps, m0); x1 <- rpois(reps, m1)
z  <- log(x1 / x0) / sqrt(1 / x0 + 1 / x1)
cat(sprintf("Simulated power, Poisson counts, n = %s per arm: %.3f\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE)))
phi <- 1.5
y0 <- rnbinom(reps, mu = m0, size = m0 / (phi - 1)); y1 <- rnbinom(reps, mu = m1, size = m1 / (phi - 1))
z2 <- log(y1 / y0) / sqrt(phi * (1 / y0 + 1 / y1))
cat(sprintf("Simulated power, over-dispersed counts (phi = 1.5), same n: %.3f\n", mean(abs(z2) > z_a, na.rm = TRUE)))

Output from running the code

100% of observed effect: n per arm = 456 (80% power), 610 (90% power)
 75% of observed effect: n per arm = 792 (80% power), 1,060 (90% power)
 50% of observed effect: n per arm = 1,742 (80% power), 2,333 (90% power)
Simulated power, Poisson counts, n = 456 per arm: 0.804
Simulated power, over-dispersed counts (phi = 1.5), same n: 0.626

The first simulation draws Poisson counts and should land close to the target power. The second allows extra variability (variance 1.5 times the mean, a purely illustrative value), which lowers the power at the same sample size, so rate trials usually need more participants than the Poisson formula suggests.

14. Analyses Reported by the Sponsor

The sponsor’s primary analysis used negative binomial regression and reported adjusted rate ratios. For Q2W versus placebo, the estimate was 0.845 with a 95% confidence interval of 0.715 to 0.998. For Q4W versus placebo, it was 0.930 with a 95% confidence interval of 0.789 to 1.095. Those are the registry’s reported analyses and should anchor interpretation of the primary endpoint.

The recalculation uses posted group rates to form simple unadjusted comparisons. It does not reproduce the sponsor’s adjustment or the negative binomial model. The registry record flags a discrepancy between the recalculated and reported results. Under that circumstance, the sponsor’s own analysis takes precedence; the recalculation is best understood as a transparent approximate check rather than a competing primary analysis.

Differences can arise because adjusted model estimates need not match ratios reconstructed from rounded group summaries, and because the analyses use different modeling assumptions. The record does not report enough detail to identify the particular source of the discrepancy. It also does not report the full statistical analysis plan, including the model’s covariate specification. Therefore, the posted sponsor estimate is the appropriate reported result, while the recalculated value should not be used to revise the trial’s conclusion.

15. Multiplicity, Missing Data and Analysis Populations

The registry record identifies a primary endpoint and multiple secondary outcomes, but does not report a multiplicity-control procedure, a testing hierarchy, or a strategy for interpreting the family of statistical tests. When several outcomes or comparisons are tested, each result may have its own nominal uncertainty level. Without a stated adjustment or prespecified hierarchy, isolated secondary results should be viewed as exploratory rather than as independent confirmatory evidence. The record’s designation of endpoints as primary or secondary does not, by itself, show how the overall type I error was controlled.

The primary outcome includes two comparisons with placebo, one for each astegolimab schedule. The registry record reports the adjusted analyses, but the available information does not describe how multiplicity across these comparisons was handled. It also does not report whether interim analyses were planned or conducted, or whether any stopping boundaries applied. Those details are not reported in the registry record.

For the primary endpoint, the analysis population is described as randomized participants who received at least one dose, grouped according to randomized assignment. The record says the number analyzed reflects participants with data available for analysis. It does not report the amount or pattern of missing outcome data, the method used to address missingness, or sensitivity analyses for missing data. For SGRQ-C, the sponsor reports an MMRM analysis, but the registry record does not give the assumptions about missing repeated measurements or further model details. The same level of missing-data detail is not reported for all secondary outcomes.

The absence of these details does not establish that no procedures were used; it means the registry record does not document them. Protocol and statistical analysis plan details would be needed to evaluate prespecification, missing-data handling, and multiplicity more fully. Results should therefore be read alongside the reported analysis methods and their stated limits, without assuming unreported procedures.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: chronic obstructive pulmonary disease (16.1%), pneumonia (3.3%), atrial fibrillation (1.1%), covid-19 (1.1%), acute kidney injury (1.1%).

The registry reports serious adverse events among 111 of 449 participants at risk in the astegolimab Q2W group, 126 of 442 in the Q4W group, and 137 of 442 in the placebo group. Deaths were reported for 13, 11, and 16 participants, respectively. These are counts of participants with the listed events and the corresponding numbers at risk; they are not adjusted comparisons and should not be interpreted as establishing a cause or treatment relationship.

The most frequently listed serious adverse event term is chronic obstructive pulmonary disease, reported as 16.1%. Other listed terms include pneumonia at 3.3%, atrial fibrillation at 1.1%, COVID-19 at 1.1%, acute kidney injury at 1.1%, and acute respiratory failure at 0.9%. The registry record does not make the denominator for these term percentages explicit in the information, so they should be read as the record’s listed percentages rather than converted into group-specific risks.

Serious adverse-event totals and deaths are important descriptive safety information, but they do not alone establish comparative safety. Interpretation would require details such as event timing, exposure duration, attribution, severity definitions, and statistical comparisons. Those details are not reported in the registry record. The counts should be considered within the study population and follow-up context, not generalized beyond it.

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

The posted primary analysis estimates lower adjusted exacerbation rates for both astegolimab schedules than for placebo, with more uncertainty around the Q4W estimate. The Q2W sponsor-reported interval lies just below the rate-ratio reference of 1, while the Q4W interval spans 1. These data describe the estimated group comparisons over the study’s 52-week treatment period; they do not by themselves establish the clinical importance of the estimated difference.

The result does not establish that the two dosing schedules differ from one another. Each was compared with placebo, and a direct schedule-to-schedule analysis is not reported in the registry record. Nor does the primary endpoint isolate severe events: it combines moderate and severe exacerbations. Secondary outcomes provide other perspectives, but their estimates are uncertain, they address different questions, and the multiplicity plan is not reported.

Statistical evidence and clinical meaning are distinct. A confidence interval describes uncertainty in an estimate under the model, while clinical importance depends on how large a difference matters to patients and clinicians. The registry record does not report a threshold for clinically important change in exacerbation rate or the SGRQ-C score. It also does not provide numerical results for every listed secondary outcome in the information available.

These findings apply to the enrolled study population: former or current smokers with COPD and a history of frequent exacerbations, receiving standard-of-care maintenance therapy. The trial’s duration, analysis population, missing-data details, and generalizability beyond that population all matter. The posted results should therefore be understood as estimates from this particular randomized comparison, not as individual treatment guidance or a complete account of all clinical considerations.

18. Why This Trial Matters Statistically

This trial illustrates several important statistical issues in clinical research. Its primary outcome is a recurrent-event rate, not a simple count of participants with an event. That choice makes exposure time relevant and permits multiple exacerbations to contribute to the outcome. The adjusted negative binomial analysis also reflects the fact that count outcomes may require a model that allows more variability than a basic Poisson model assumes.

The record offers both sponsor-reported adjusted results and simple recalculations from group summaries, and it flags a discrepancy. This is a useful reminder that a summary-statistic reconstruction may not reproduce an adjusted model. Differences in modeling, adjustment, and rounding can matter, so transparent recalculations should be distinguished from the trial’s own inferential analysis. Here, the sponsor’s reported model is the primary basis for interpretation.

The trial also demonstrates why confidence intervals matter alongside point estimates. The Q2W primary estimate is close to the no-difference reference, while the Q4W interval spans it. Describing only the point estimates would hide that distinction in precision. The several secondary outcomes further show why multiplicity and prespecification matter: results from related outcomes can be informative, but should not be treated as a collection of independent confirmations when an adjustment plan is not documented.

Finally, the planning illustrations connect observed effects to future design requirements, while remaining separate from the trial’s original design justification. They show how smaller target effects require more information, but do not establish observed power or retrospectively determine whether the completed study was adequately designed.

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.
• Rate comparisons use a Poisson approximation unless the sponsor posted confidence limits; real event counts are often over-dispersed.

The registry record provides limited detail for independently assessing the full analysis. It does not report the original sample-size justification, complete statistical analysis plan, model covariates, randomization implementation, or any interim-analysis procedures. It also does not report how multiplicity was handled across the two primary comparisons and the many secondary outcomes.

The primary outcome’s adjusted model is identified as negative binomial regression, but the record does not describe all model specifications. The recalculated comparison is an unadjusted approximation and differs from the sponsor’s analysis; the record flags this discrepancy but does not explain its source. The sponsor-reported analysis should therefore be treated as the trial’s primary result, while the available information is insufficient to reconcile every computational detail.

Missing-data reporting is also limited. The mITT definition and the rule that analyzed counts reflect data availability are described, but the amount and pattern of missingness, handling strategy, and sensitivity analyses are not reported in the registry record. Model assumptions for the repeated-measures quality-of-life analysis are not fully documented. Numerical results are not available in the registry record for every secondary outcome listed.

The safety information is descriptive and does not include a complete account of event timing, attribution, exposure-adjusted rates, or formal between-group comparisons. The denominator for the listed serious-event term percentages is not specified in the available record. Finally, the study population was defined by COPD, smoking history, and frequent exacerbations; the posted results alone do not establish how well they apply to people outside that study population.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: A Study to Evaluate the Efficacy and Safety of Astegolimab in Participants With Chronic Obstructive Pulmonary Disease — NCT05037929.
• Registry record last updated 2026-10-16; status last verified 2026-09.
• Results first posted 2026-10-16.
• 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

NCT05037929 is a completed Phase IIb, randomized, double-blind, placebo-controlled, multicenter study of astegolimab in participants with COPD. It compared subcutaneous astegolimab Q2W and Q4W with placebo Q2W, alongside standard-of-care maintenance therapy. The registry lists 1,334 participants enrolled.

The primary endpoint was the annualized rate of moderate and severe COPD exacerbations over 52 weeks. The sponsor’s adjusted negative binomial analysis reported a rate ratio of 0.845 for Q2W versus placebo and 0.930 for Q4W versus placebo. The record flags a discrepancy with simple recalculations, so the sponsor’s analysis takes precedence.

Secondary outcomes include event timing, quality of life, lung function, symptoms, severe exacerbations, and physical function. Multiplicity procedures, the original design assumptions, and several missing-data and model details are not reported in the registry record.