A Study of ALXN1830 in Healthy Adult Participants: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of ALXN1830 in Healthy Adult Participants (NCT04730804), a randomized phase 1 study. The primary outcome is Number of Participants With Treatment-Emergent Adverse Events (TEAEs).

2. Clinical Question

3. Trial Design

This was a Phase 1 randomized, double-blind, placebo-controlled, parallel-group study of ALXN1830 in healthy participants. Its registered title describes single and multiple ascending doses administered subcutaneously. The registry lists six cohort descriptions: two single-dose cohorts, three multiple-dose cohorts, and a multiple-dose cohort in a Japanese population. Specific dose amounts and the detailed schedule for each cohort are not reported in the registry record.

The primary outcome was the number of participants with treatment-emergent adverse events (TEAEs). The timeframe began on Day 1 after dosing and continued through follow-up up to approximately 141 days. The primary-outcome population was the Safety Set, defined as all participants who received at least 1 dose of study drug. The registry record gives primary-outcome counts for five ALXN1830 cohorts and placebo; results for the Japanese cohort are not reported in the registry record.

Enrollment is recorded as 34, and the study status is terminated. The registry lists 2021-03-17 as the study start and 2021-12-14 as primary completion. Those dates and status describe the registry record; they do not explain why the study was terminated. The reason for termination, the intended recruitment target, and the protocol’s rationale for its design are not reported in the registry record.

The posted arm counts are small and vary across groups, including a single participant in the single high-dose arm. The registry does not provide an estimable two-arm statistical comparison for the binary primary endpoint. Consequently, the design and results are best read as a descriptive early-phase safety record, not as a basis for a precise comparative estimate.

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 34 participants (25 ALXN1830 treated and 9 placebo-treated) were enrolled and randomized in a 6:2 ratio in 5 cohorts. Healthy, Japanese participants were planned to be dosed in Cohort 6 according to the highest tolerated dose (HTD) established in the non-Japanese cohorts. This cohort was not achieved due to early termination of the study.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The Safety Set included all participants who received at least 1 dose of study drug.

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 Safety Set included all participants who received at least 1 dose of study drug.

Only the first 6 of 7 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Treatment-Emergent Adverse Events (TEAEs), measured over Day 1 (postdose) through follow-up (up to approximately 141 days).

The primary endpoint is the number of participants with treatment-emergent adverse events. The registry defines an adverse event as an untoward medical occurrence in a participant who received study drug; the event need not have a causal relationship to treatment. A TEAE is an adverse event whose start date or time is on or after the first dose of study intervention. The observation period begins on Day 1 after dosing and continues through follow-up up to approximately 141 days.

This endpoint is used to describe the safety experience after exposure. Counting participants with at least one event gives a straightforward summary of how many people in each group experienced an event during the specified period. It does not, by itself, describe the number of events per participant, their severity, duration, or relationship to treatment. Those details require other outcome information.

The registry identifies the Safety Set as participants who received at least 1 dose of study drug. The posted primary results list 6 participants with TEAEs in the single medium-dose cohort, 1 in the single high-dose cohort, 6 in the multiple low-dose cohort, 6 in the multiple medium-dose cohort, 5 in the multiple high-dose cohort, and 7 in the placebo group. These are counts, not rates or adjusted comparisons. A formal comparative estimate for the primary endpoint is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count represent?

The primary endpoint is a binary participant-level outcome: for each participant in the Safety Set, the outcome indicates whether at least one TEAE was recorded during the defined observation period. A group count states how many participants met that condition. It is distinct from a count of all adverse-event episodes, because one participant may have more than one event. The registry’s primary outcome is explicitly a number of participants, not a total number of event reports.

General statistical explanation: binary outcomes are often compared by estimating the difference or ratio between the proportions of participants with an event in two groups. Such an estimate is usually accompanied by a confidence interval, which conveys the range of values reasonably compatible with the data under the analysis assumptions. The posted record does not report such an estimate or interval for this outcome. The listed counts should therefore be read as descriptive results, not as an inferential comparison.

Why does the group structure matter?

The study has several ALXN1830 cohorts, separated by single or multiple dosing and by dose level, alongside placebo. These are not interchangeable groups: their dosing patterns differ, and the registry does not state the dose amounts. A simple pooling of all ALXN1830 cohorts would require a prespecified rationale and an analysis that accounts for those differences. Such a pooled analysis is not reported in the registry record. Nor does the record report an estimable two-arm comparison for the primary binary endpoint.

General statistical explanation: randomization can reduce systematic differences between groups at assignment, but it does not guarantee that small groups will be balanced on every characteristic. With small group sizes, chance variation can have a visible influence on event counts. A count from a cohort with few participants is especially limited as a precise estimate of the event frequency in a broader population. The cohort counts are therefore useful for describing the observed study experience, while uncertainty about underlying event frequencies remains substantial.

How should uncertainty be understood?

General statistical explanation: a confidence interval describes uncertainty in an estimated effect, conditional on the statistical method and assumptions used. A wider interval indicates less precision; a narrower interval indicates greater precision. A p-value, when reported, addresses compatibility of data with a specified null hypothesis under a model. Neither measure alone describes clinical importance or proves causation. No confidence intervals or p-values for the primary endpoint are reported in the registry record, so those forms of comparative uncertainty cannot be assessed from the posted results.

The registry identifies the primary analysis population as the Safety Set: participants who received at least 1 dose of study drug. This differs conceptually from an analysis of everyone randomized, because a participant who never received study drug would not meet this definition. The record does not report a separate randomized-population analysis or explain how participants with incomplete follow-up were handled.

What do planning calculations mean?

General statistical explanation: a sample-size calculation is a planning exercise. It uses assumptions about an effect, variability or event frequency, significance level, allocation, and analysis method to illustrate the amount of information a future study might require. It is not an observed result and does not measure the power achieved by this completed trial. The registry’s stated planning illustration assumptions use a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. Those are described as planning assumptions, not as the trial’s own design justification. The sample-size justification and the trial’s actual statistical plan are not reported in the registry record.

General statistical explanation: over-dispersion is relevant when the variability in observed outcomes is greater than a statistical model assumes. In count outcomes, for example, an analysis that assumes all counts vary according to a simple Poisson model may understate uncertainty if the data are more variable. The primary endpoint in this study is a count of participants with an event, not a count of event episodes, and the registry does not report a model-based analysis or evidence about over-dispersion. It would therefore be inappropriate to infer that such a model was used or needed for the posted primary result.

Overall, the registry record permits a clear description of group-specific TEAE counts, but not a statistical estimate of comparative effect. The absence of reported inferential results is important: the descriptive values do not become evidence of a treatment difference simply because they can be placed side by side.

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("Cohort 1: ALXN1830 Single Medium Dose", "Cohort 2: ALXN1830 Single High Dose", "Cohort 3: ALXN1830 Multiple Low Dose", "Cohort 4: ALXN1830 Multiple Medium Dose", "Cohort 5: ALXN1830 Multiple High Dose", "Placebo")
n      <- c(6, 1, 6, 6, 6, 9)
events <- c(6, 1, 6, 6, 5, 7)
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  Cohort 1: ALXN1830 Single Medium Dose  6  6  100.0  54.1  100.0  61.0  100.0  59.0  99.6
ARM  Cohort 2: ALXN1830 Single High Dose  1  1  100.0  2.5  100.0  20.7  100.0  15.8  98.7
ARM  Cohort 3: ALXN1830 Multiple Low Dose  6  6  100.0  54.1  100.0  61.0  100.0  59.0  99.6
ARM  Cohort 4: ALXN1830 Multiple Medium Dose  6  6  100.0  54.1  100.0  61.0  100.0  59.0  99.6
ARM  Cohort 5: ALXN1830 Multiple High Dose  6  5  83.3  35.9  99.6  43.6  97.0  42.1  96.3
ARM  Placebo  9  7  77.8  40.0  97.2  45.3  93.7  44.4  93.3

11. Multiplicity, Missing Data and Analysis Populations

The registry lists seven secondary outcomes in addition to the primary endpoint. They cover ALXN1830 serum concentration exposure after single and multiple dosing, change from baseline in serum IgG at the early termination visit, FcRN receptor occupancy, and antidrug and neutralizing antibodies. The registry identifies 8 outcome measures overall. Results for the listed secondary outcomes are not included in the registry record described by this record, so their estimates and uncertainty are not reported in the registry record.

Multiplicity arises when several outcomes, time points, or comparisons are evaluated. General statistical explanation: the more tests conducted, the greater the chance that at least one result may appear notable by chance if each test is interpreted independently. A prespecified strategy may address this issue, for example by prioritizing outcomes or adjusting inference, but the multiplicity strategy is not reported in the registry record. The number of posted analyses is 0, and no primary-endpoint comparison is reported.

The registry defines the primary analysis population as the Safety Set, which includes participants who received at least 1 dose of study drug. Missing-data handling, including how incomplete observation periods or unavailable outcome measurements were treated, is not reported in the registry record. The record also does not describe imputation, censoring rules, or sensitivity analyses for missing observations. Those methods should not be assumed.

The primary outcome counts are available for the listed five ALXN1830 cohorts and placebo. Primary-outcome results for the registered Japanese population cohort are not reported in the registry record. The reason for this omission, and whether any additional participants or outcomes were excluded from reporting, 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 non-serious adverse event terms

The serious-adverse-event record lists 0 serious adverse events in each of the five reported ALXN1830 cohorts and in placebo. It lists 0 deaths in each of those groups. The numbers at risk for serious events are 6, 1, 6, 6, 6, and 9, respectively. These values describe the recorded experience within the listed groups and follow-up; they are not evidence that serious events or deaths cannot occur.

For other, nonserious adverse events, the registry reports 6 participants affected in the single medium-dose cohort, 1 in the single high-dose cohort, 6 in the multiple low-dose cohort, 6 in the multiple medium-dose cohort, 5 in the multiple high-dose cohort, and 7 in placebo. These are participant counts. They do not state the number of separate event episodes or provide details about severity, duration, or causal attribution. The primary endpoint definition also makes clear that an event need not be caused by study treatment to count.

These safety figures are descriptive, and no formal comparison is reported in the registry record. The results for the Japanese population cohort are not reported in the registry record. Small group sizes and limited reporting mean that the zero serious-event counts should be interpreted as observations during this study, not as a guarantee about future experience or a definitive comparison between ALXN1830 and placebo.

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

The results show the number of participants recorded as having a TEAE in each reported cohort during the specified follow-up. The registry reports 6 participants in the single medium-dose cohort, 1 in the single high-dose cohort, 6 in the multiple low-dose cohort, 6 in the multiple medium-dose cohort, 5 in the multiple high-dose cohort, and 7 in placebo. It separately reports 0 serious adverse events and 0 deaths in each listed group. These figures describe what was recorded among the participants represented in those groups.

They do not show that ALXN1830 caused every recorded event. The registry definition of an adverse event does not require a causal relationship to study drug. Nor do the counts establish that one dose level is safer or less safe than another. The cohorts differ in dosing pattern and level, and a comparative statistical analysis is not reported. The record also does not give a confidence interval or p-value for the primary endpoint, so the precision of a treatment comparison cannot be judged.

These results do not establish safety for populations beyond the healthy adults studied, and the registry’s Japanese cohort has no reported primary-outcome result in this record. The small group sizes, including the single participant in the single high-dose cohort, limit the amount of information available about uncommon events. A lack of a serious event in a listed group is not proof that such an event could never occur.

The study’s terminated status is part of the registry record, but the reason for termination is not reported in the registry record. It should not be used to infer a safety problem or any other particular cause. Overall, the posted information supports a descriptive account of recorded adverse events in the listed groups; it does not support a definitive claim about comparative effects or future risk.

14. Why This Trial Matters Statistically

This study illustrates a central statistical challenge in early-phase clinical research: the primary purpose of collecting safety outcomes is not the same as having enough information for a precise comparison. The registry reports group-specific TEAE counts and serious-event counts, but it does not report a comparative estimate for the binary primary endpoint. Readers can describe the observations, while recognizing that comparative uncertainty is not quantified in the record.

The multi-cohort structure also matters. Single-dose and multiple-dose cohorts, different dose levels, and the registered Japanese population are distinct parts of the study design. Without dose amounts, detailed cohort procedures, or a reported analysis plan, the counts cannot be treated as a simple dose-response series. The record reports primary results for five ALXN1830 cohorts and placebo, while primary results for the Japanese cohort are not reported in the registry record.

The study is also a useful example of why an event count should not be confused with an event rate, an event burden, or a treatment effect. The primary outcome counts participants with TEAEs; it does not count every episode or establish causality. Separate serious-event counts add information about observed serious outcomes, but zero recorded events in these groups cannot rule out future or uncommon events.

Finally, the record distinguishes descriptive results from planning calculations. A planning illustration based on an observed effect is not the original trial’s sample-size justification and is not observed power. Because the trial’s own statistical plan, termination reason, and missing-data methods are not reported in the registry record, these omissions should remain part of any careful interpretation.

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 reported primary endpoint is a count of participants with TEAEs, and no two-arm estimate or inferential analysis is reported. There are no reported confidence intervals or p-values with which to assess comparative precision. The listed groups are small and unequal in size, and the single high-dose cohort includes 1 participant. Accordingly, the observed counts offer limited information about underlying event frequencies and uncommon outcomes.

The registered design includes six cohort descriptions, including a Japanese population cohort, but primary-outcome results are listed for five ALXN1830 cohorts and placebo. Results for the Japanese cohort are not reported in the registry record. Dose amounts, detailed dosing schedules, and the allocation ratio are also not reported in the registry record, limiting interpretation of patterns across dose groups.

The study status is terminated, but the reason for termination is not reported in the registry record. The record does not report a sample-size justification, interim-analysis approach, or statistical analysis plan. It also does not describe missing-data handling or provide a separate analysis population beyond the Safety Set definition. These gaps prevent assessment of whether the reported analysis followed a prespecified plan or how incomplete follow-up may have affected the results.

The registry defines adverse events without requiring a causal relationship to treatment. The participant counts therefore do not identify which events, if any, were attributed to ALXN1830. Further details on event severity, timing, and duration are not reported in the registry record. The results should consequently be treated as a limited descriptive safety record rather than a comprehensive comparative assessment.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Study of ALXN1830 in Healthy Adult Participants — NCT04730804.
• Registry record last updated 2024-09-19; status last verified 2024-09.
• Results first posted 2024-09-19.
• 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

NCT04730804 is a randomized, double-blind, placebo-controlled Phase 1 study of subcutaneous ALXN1830 in healthy adult participants. The registered design includes single-dose and multiple-dose cohorts and a Japanese population cohort. Enrollment is recorded as 34; the study is listed as terminated. The reason for termination is not reported in the registry record.

The primary endpoint is the number of participants with TEAEs from Day 1 after dosing through follow-up up to approximately 141 days, in the Safety Set of participants who received at least 1 dose. The record reports counts by the five listed ALXN1830 cohorts and placebo, but no estimable two-arm comparison or inferential analysis. It reports 0 serious adverse events and 0 deaths in each listed group. Primary-outcome results for the Japanese cohort, the statistical analysis plan, and missing-data methods are not reported in the registry record.