A Study of Galcanezumab in Healthy Participants: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of Galcanezumab in Healthy Participants (NCT02576951), a randomized phase 1 study. The primary outcome is Part A: Number of Participants With an Injection Site Adverse Event.

2. Clinical Question

The broader study had two distinct aims. Part A evaluated tolerability of the galcanezumab solution formulation. Part B compared how much of the lyophilized formulation entered the bloodstream and how long it took the body to eliminate it, relative to the solution formulation. The registry also describes pharmacodynamic outcomes involving plasma CGRP. Those aims provide context, but they should not be conflated with the primary safety endpoint, which concerns injection-site events in Part A.

3. Trial Design

This was a randomized, double-masked, parallel Phase 1 study of galcanezumab in healthy participants. The registry lists overall enrollment as 178 and the study status as completed. The recorded study dates are 2015-10-19 for start and 2016-09-03 for primary completion. The summary says each part lasted about six months and that a participant could enroll in only one part.

The study had two parts with different comparisons. Part A included a single subcutaneous injection of galcanezumab solution and a single subcutaneous injection of placebo. The primary endpoint was a safety count from this part. Part B included a single subcutaneous injection of galcanezumab in either a lyophilized formulation or a solution formulation. Part B’s stated purpose was to compare absorption and elimination, with pharmacodynamic outcomes also listed.

The reported Part A endpoint counts are based on 15 galcanezumab participants and 3 placebo participants. The adverse-event results list 80 participants at risk in each Part B formulation group. These are the group sizes recorded for the respective results; the registry record does not explain how they relate to overall enrollment or describe participant flow between enrollment, dosing, and analysis.

Randomization and double masking are recorded, but the randomization procedure, allocation concealment, and who was masked are not reported in the registry record. The registry also does not report how the two parts were organized operationally beyond their different treatments and stated purposes. Consequently, design features beyond the recorded labels should not be assumed.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All randomized participants who received at least one dose of study drug in Part A and had at least one post dose safety assessment.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: All randomized participants.

6. Primary Endpoint

The registry lists the primary outcome as Part A: Number of Participants With an Injection Site Adverse Event, measured over Part A: Predose through 48 hours post dose.

The primary endpoint is the number of participants with an injection-site adverse event in Part A. It covers the period from predose through 48 hours post dose. When an injection-site reaction was present, the registry description says it would be characterized, including erythema, induration, pain, and itching. The reported endpoint values are counts of participants, rather than a measure of how many separate reactions each participant experienced.

In general, an event count is a direct way to describe how often a defined safety event occurred in the population being assessed. It gives a readily interpretable summary of observed events during a specified period. For this endpoint, the relevant record population comprises randomized participants who received at least one dose in Part A and had at least one post-dose safety assessment.

The measure does not, by itself, describe the intensity, duration, or clinical consequences of an event. Nor does a participant count establish that treatment caused an event. The registry description says that injection-site reactions were to be characterized, but the primary endpoint result itself is a count. The posted counts are 3 participants with an event among the 15 in the galcanezumab group and 0 among the 3 in the placebo group. No comparative estimate or confidence interval is reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry records a randomized, double-masked, parallel design. These labels describe features of the study structure, but the record does not give the randomization method, masking procedures, or a detailed statistical analysis plan. In particular, it does not report the method used to compare the Part A event counts, if a formal comparison was conducted outside the registry posting.

What does a participant count represent?

The primary outcome is a binary event at the participant level: a participant either had at least one injection-site adverse event during the defined period or did not. The reported values are counts of participants with an event. In general, an event count is not the same as a count of all event episodes, because a participant with multiple episodes may still be counted once for a participant-level outcome. The registry describes the endpoint as number of participants and does not post a separate episode count.

The outcome’s population definition matters. The registry says the primary endpoint includes randomized participants who received at least one dose in Part A and had at least one post-dose safety assessment. Thus, the relevant denominator is tied to dosing and assessment, not merely to the total enrollment figure. The record gives 15 and 3 participants for the Part A endpoint groups, but does not provide a detailed accounting of screened, randomized, dosed, assessed, or excluded participants.

What can be inferred from the posted counts?

Descriptive counts show what was observed in the recorded groups. They do not alone quantify how precisely the underlying event frequencies are known, or whether a between-group difference is compatible with chance variation. A confidence interval, in general, expresses a range of values consistent with the data and a specified method. No interval for the primary endpoint is reported in the registry record. A p-value, in general, summarizes how incompatible data are with a specified null model under its assumptions; it is not a measure of clinical importance or the probability that a hypothesis is true. No p-value or inferential test for the primary comparison is posted.

With a small group, particularly one with no observed events, uncertainty can remain substantial even when the observed count is zero. In general, the absence of observed events in a finite sample does not demonstrate absence of risk. Any formal estimate would depend on the selected statistical method and assumptions, neither of which is documented for this endpoint in the registry record.

What does masking add?

In general, masking can reduce the influence of expectations on assessments and reporting, depending on who is masked and how the masking is maintained. The registry labels the study double-masked, but does not identify which roles were masked or describe procedures for preserving masking. It is therefore appropriate to report the design label without adding details about its implementation.

Why do the study parts need separate interpretation?

Part A and Part B address different questions and use different comparisons. Part A’s primary outcome is injection-site safety after solution formulation or placebo. Part B compares two galcanezumab formulations and has pharmacokinetic and pharmacodynamic aims. Combining the groups across parts would not answer the primary endpoint question and could obscure the distinct comparisons. The registry does not post numerical results for the listed pharmacodynamic outcomes, so no inference about those measures can be drawn from their names alone.

How should planning calculations be read?

In general, a sample-size planning illustration asks how many participants per arm might be needed under specified assumptions to detect an effect of a chosen size. The registry record describes planning illustrations based on the observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. Such calculations are planning illustrations, not observed power and not evidence that the trial was designed with those assumptions. The record does not report the trial’s own sample-size justification. No planning count should be treated as a participant count observed in this trial.

The record indicates that no analyses are posted for the outcome results. It does not document whether analyses were conducted but not entered in the registry, nor does it describe adjustments, covariates, model choices, interim analyses, or a prespecified hierarchy of tests. Those details are not reported in the registry record and cannot be inferred from the design labels or outcome list.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("240 mg Galcanezumab - Part A", "Placebo - Part A")
n      <- c(15, 3)
events <- c(3, 0)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  240 mg Galcanezumab - Part A  15  3  20.0  4.3  48.1  7.0  45.2  7.3  45.6
ARM  Placebo - Part A  3  0  0.0  0.0  70.8  0.0  56.1  0.6  60.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists six secondary pharmacodynamic outcomes across the two study parts, in addition to the primary safety endpoint. The listed measures include plasma CGRP time to maximum concentration, maximum concentration, and area under the concentration-versus-time curve. The registry record does not report numerical results for these secondary outcomes or explain whether or how multiplicity was addressed.

In general, testing multiple outcomes can increase the chance of at least one apparently notable result if each is assessed separately. Approaches to multiplicity can include adjusting significance thresholds or specifying a hierarchy, but no such approach is reported in the registry record. Because no analyses are posted, there are no reported secondary-outcome tests to interpret.

Missing-data handling is also not reported in the registry record. The primary population definition requires at least one dose and at least one post-dose safety assessment, but the record does not give participant-level completion information, counts excluded from the endpoint population, or reasons for missing assessments. It does not describe imputation, censoring, or sensitivity analyses. The extent and potential effect of missing data therefore cannot be assessed from the registry information.

The record does not detail the analysis population for the secondary outcomes or state whether all randomized participants were included in each analysis. The primary endpoint’s stated population should not be assumed to apply to every other outcome. Likewise, the registry’s absence of posted analyses does not establish that no analyses were performed; it means the analysis methods and results needed to evaluate those questions are not reported in the registry record.

12. 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: cellulitis (33.3%), atrial fibrillation (1.2%).

The serious adverse event counts are reported separately by study group. In Part A, the registry lists 0 serious adverse events among 15 participants in the galcanezumab group and 1 among 3 participants in the placebo group. In Part B, it lists 1 among 80 participants in the lyophilized formulation group and 0 among 80 in the solution formulation group. No deaths are listed in any of these groups.

These are observed counts, not estimates of comparative risk. The Part A groups are small, and the registry does not report a statistical comparison or uncertainty interval for serious adverse events. A count of zero means none was recorded in that group in the posted safety results; it does not establish that the event risk is zero. The registry description states that serious adverse events are summarized regardless of causality, so the counts should not be read as events judged to have been caused by the study treatment.

The registry’s list of top serious-event terms includes cellulitis at 33.3% and atrial fibrillation at 1.2%. The record does not provide enough context alongside those percentages to infer a group-specific rate or denominator. They should therefore be read as listed terms and percentages, not as a basis for comparing treatment groups.

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

The primary endpoint gives a limited, direct account of injection-site adverse events observed after dosing in Part A: 3 participants in the galcanezumab group and 0 in the placebo group. It answers a narrow descriptive question within a defined safety population and timeframe. It does not provide a precise estimate of the difference between groups, because the registry record reports no comparative analysis or confidence interval.

The zero count in the placebo group should not be interpreted as proof that injection-site events cannot occur with placebo. More generally, a zero observed count in a small sample can coexist with uncertainty about the underlying event frequency. The same caution applies to serious adverse event counts. The posted safety numbers describe what was recorded in the trial groups, not a guarantee about outcomes beyond those participants and observation conditions.

The broader study had pharmacokinetic and pharmacodynamic objectives, including comparison of lyophilized and solution formulations in Part B and plasma CGRP outcomes. The registry’s listing of these outcomes does not establish what their results were. Numerical results for those measures are not reported in the registry record, so no conclusion about formulation exposure, elimination, or CGRP response can be drawn from the endpoint names alone.

The trial was conducted in healthy participants and included single subcutaneous injections. The primary safety endpoint covers predose through 48 hours post dose. These features define the scope of the reported result. The result does not by itself establish longer-term tolerability, findings in other populations, or a treatment effect on a clinical condition. It is also not a substitute for a complete safety profile: other nonserious and serious adverse events are recorded separately, and their counts have their own limitations.

The most defensible reading is therefore descriptive and bounded: the registry records the specified event counts and group sizes, while leaving comparative precision and the broader outcome analyses unreported.

14. Why This Trial Matters Statistically

This trial illustrates why the question being asked and the outcome being measured must be kept distinct. The primary endpoint is a short-term injection-site safety count in Part A. The trial’s wider objectives include pharmacokinetic and pharmacodynamic assessment, primarily in Part B. Those aims call for different outcomes and comparisons; results from one should not be used as a stand-in for another.

It also demonstrates the importance of denominators and analysis populations. Overall enrollment is 178, while the primary endpoint groups contain 15 and 3 participants and the Part B safety groups each list 80 at risk. Without a participant-flow account, these figures cannot be reconciled into a fuller explanation of enrollment and analysis. Stating the endpoint-specific groups is essential for understanding what the counts describe.

For a binary safety outcome in small groups, descriptive counts can be informative while still leaving substantial uncertainty. A zero in one group is not proof of zero underlying risk, and a raw count does not quantify the precision of a comparison. Confidence intervals and a clearly described analysis would help express that uncertainty, but they are not reported for the primary endpoint in the registry record.

Finally, registry completeness is itself relevant to statistical interpretation. The record provides design labels, endpoint definitions, and selected safety counts, but does not report an analysis plan, missing-data methods, multiplicity handling, or numerical secondary pharmacodynamic results. Readers can identify the intended questions and the posted observations, but should not fill the gaps with assumptions about methods or findings.

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.

The main limitation for interpreting the primary result is the small number of participants in the Part A groups, especially the placebo group. The posted event counts are therefore descriptive, and the registry record does not report a confidence interval, p-value, or formal comparison to show the precision of a difference.

The primary endpoint is restricted to injection-site adverse events from predose through 48 hours post dose. It does not capture longer-term events by its stated timeframe, and the result does not describe all dimensions of a reaction. Although the endpoint description lists features such as erythema, induration, pain, and itching for characterization, the posted primary result is a participant count rather than a detailed account of severity or duration.

The registry record does not provide a participant-flow diagram or a full accounting of missing assessments and exclusions. It defines the primary population by dosing and post-dose safety assessment, but does not report how many participants failed to meet those criteria or why. Missing-data procedures and sensitivity analyses are not reported.

Further limitations include the absence of a posted statistical analysis for the primary endpoint, no reported multiplicity strategy for the secondary outcomes, and no numerical results for the listed pharmacodynamic measures. The randomization and masking procedures are not described beyond the recorded design labels. The registry also does not state the trial’s sample-size justification. These omissions limit assessment of analysis choices and precision; they do not establish that procedures or analyses were absent from the study itself.

Finally, the results concern healthy participants and the specified formulations and dosing conditions. Generalization beyond that study setting is not supported by the posted record alone.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Study of Galcanezumab in Healthy Participants — NCT02576951.
• Registry record last updated 2019-02-26; status last verified 2018-02.
• Results first posted 2019-02-26.
• 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

The registry record describes a completed, randomized, double-masked, parallel Phase 1 study of galcanezumab in healthy participants, with overall enrollment of 178. Part A assessed solution-formulation tolerability against placebo; Part B compared lyophilized and solution formulations and included pharmacokinetic and pharmacodynamic objectives. Participants could enroll in only one part.

The primary endpoint was the number of Part A participants with an injection-site adverse event from predose through 48 hours post dose. The record reports 3 participants in the 240 mg galcanezumab group and 0 in the placebo group. It also posts serious and other nonserious adverse-event counts by group. No inferential analysis, confidence interval, or p-value for the primary comparison is reported in the registry record. Numerical results for the listed secondary pharmacodynamic outcomes, analysis methods, missing-data handling, and the trial’s sample-size justification are not reported.