A Post Approval Commitment Study to Gain More Information on How Safe and Effective KOVALTRY is in Chinese Children, Adolescents /Adults With Severe Hemophilia A: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Post Approval Commitment Study to Gain More Information on How Safe and Effective KOVALTRY is in Chinese Children, Adolescents /Adults With Severe Hemophilia A (NCT04565236), a non-randomized phase 4 study. The primary outcome is Annualized Bleeding Rate (ABR) of All Bleeding Episodes During Prophylaxis Treatment in Part A.

2. Clinical Question

The clinical question is therefore descriptive: what bleeding rate and safety experience were recorded among the participating patients treated with KOVALTRY? The primary endpoint focuses on bleeding during prophylaxis in Part A. It counts spontaneous and trauma-related bleeding episodes and excludes bleeding due to surgery. The record also identifies pharmacokinetic assessment in a subset as a study objective, alongside safety and efficacy assessment.

Because the study has a single-group, non-randomized design, the primary question is not a randomized comparison of KOVALTRY against another treatment. The record does not report a concurrent control group or a comparison estimate. Results, if available, would describe outcomes in the studied groups; by themselves, they would not establish how those outcomes compare with a different treatment or with an untreated group.

3. Trial Design

This is a Phase 4, completed, non-randomized, single-group study sponsored by Bayer. The registry lists an enrollment of 45 participants. The study began on 2020-09-22, had a primary completion date of 2024-03-15, and is marked completed. Masking is listed as none.

The study includes two parts. Part A concerns previously treated patients with severe hemophilia A: PTPs under 12 years and PTPs aged 12 to 65 years. Part B concerns previously untreated or minimally treated patients under 6 years. KOVALTRY is listed for all three treatment groups. The record describes the study objective as collecting information on safety and efficacy for prevention and treatment of bleeds, and assessing pharmacokinetic parameters in a subset.

The primary outcome applies to Part A PTPs and is the annualized rate of all bleeding episodes during prophylaxis treatment. Its timeframe is up to 6 months. The registry lists additional outcomes covering bleeding rates in Part A and Part B, infusions per bleeding episode, physician assessment of hemostasis in minor surgery, Factor VIII recovery, inhibitor development, and treatment-emergent adverse events. The record lists 15 outcome measures overall.

A single-group, non-randomized design can describe observations during treatment but does not create a randomized control comparison. The arms represent distinct age and prior-treatment categories, rather than treatment groups assigned at random for a direct comparison. The record does not report further details of the allocation process, a protocol-defined statistical analysis plan, or a sample-size justification. Those design details are not reported in the registry record.

4. Participant Flow and Accounting

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

Before assignment: A total of 44 subjects were enrolled in Part A of the study. Of these, 2 subjects did not pass screening and 42 subjects participated in Part A. A total of 3 participants were enrolled in Part B of the study, and all of them passed screening.

Overall Study

Reasons for not completing this period:

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.

6. Primary Endpoint

The registry lists the primary outcome as Annualized Bleeding Rate (ABR) of All Bleeding Episodes During Prophylaxis Treatment in Part A, measured over Up to 6 months.

The primary endpoint is the annualized bleeding rate (ABR) of all bleeding episodes during prophylaxis treatment in Part A. It is reported as a mean with standard deviation, in bleeds per year, for previously treated patients. The registry specifies a timeframe of up to 6 months. The endpoint includes spontaneous and trauma-related bleeds and excludes bleeding due to surgery.

Annualizing a count expresses bleeding frequency on a yearly scale, which can make observation periods of differing duration easier to describe on a common rate scale. This is a general statistical explanation; the registry record does not provide the calculation details used for individual participants or the method used to combine their rates.

The mean describes the central value of the participant-level measurements, while the standard deviation describes their spread around that mean. These summaries address different aspects of the data: the mean represents average observed frequency, and the standard deviation indicates how variable the rates are among the observations. General interpretation of a mean and standard deviation does not establish the shape of the data distribution.

Bleeding rate is relevant to the stated study objective of gathering information on prevention and treatment of bleeds. However, the numerical mean and standard deviation for the primary endpoint are not reported in the registry record. The endpoint definition therefore clarifies what was intended to be measured, but the posted record does not support a numerical interpretation of the primary outcome.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a continuous measure summarized by a mean and standard deviation. In general, a mean is the arithmetic average of the observations being summarized. The standard deviation describes how spread out those observations are around the mean. A small standard deviation indicates less dispersion around the mean than a large standard deviation, but neither statistic alone describes every feature of a distribution. In this study, the numerical mean and standard deviation for the primary endpoint are not reported in the registry record.

What does annualized bleeding rate represent?

The endpoint is an annualized rate of all bleeding episodes during prophylaxis treatment. The record defines the included episodes as spontaneous and trauma bleeds and excludes bleeding due to surgery. Annualization places the frequency on a yearly scale even though the stated observation timeframe is up to 6 months. This is a general description of rate interpretation. The registry does not report the participant-level calculation method, handling of differing follow-up durations, or the method used to aggregate individual rates into the reported mean.

A rate should be distinguished from a raw count. A count records how many events occurred during observation; a rate relates event frequency to time at risk or observation time. This distinction matters when participants have different observation periods. General statistical methods can account for exposure time in several ways, but the registry record does not identify a specific model or calculation procedure for this endpoint. No such method should be inferred from the outcome name alone.

Why does the standard deviation matter?

The mean can conceal variation among participants. The standard deviation gives a summary of that variation, but it is not a confidence interval and does not directly show the precision of the mean. A confidence interval is a general method for presenting uncertainty around an estimated quantity. Its calculation depends on the data and analysis method. No confidence interval for the primary outcome is reported in the registry record, so its precision cannot be assessed from the posted primary endpoint information.

Bleeding counts can also vary considerably across individuals, and count data may be more variable than a simple statistical model expects. In general, over-dispersion means that the observed variability exceeds the variability assumed by a model. When present, it can affect standard errors and uncertainty estimates, so an analyst may consider methods that accommodate it. This is general statistical context only. The registry record does not report whether over-dispersion was assessed or whether a count model was used.

What can the study design support?

The registry lists a non-randomized allocation, no masking, and a single-group model. In general, random assignment helps make treatment groups comparable with respect to measured and unmeasured characteristics, on average. This study is not described as using that approach, and it does not list a concurrent randomized control group. Its outcomes can therefore be described within the enrolled groups, but the design does not support a randomized treatment contrast.

The age and prior-treatment categories also define distinct clinical groups. Part A includes PTPs under 12 years and PTPs aged 12 to 65 years; Part B includes PUPs/MTPs under 6 years. Differences between those groups, if reported, would not automatically represent treatment effects. Age and prior treatment distinguish the groups by design, and the record does not describe a statistical adjustment strategy for comparisons across them.

What analysis details are available?

The registry lists 15 outcome measures and zero analyses. The primary outcome description gives the measure, summary type, units, and timeframe, but a full statistical analysis plan is not reported in the registry record. The record does not state the specific model, covariate adjustment, missing-data method, or inferential procedure used for the primary outcome. It also does not report a primary outcome estimate or uncertainty interval.

The record contains a planning-illustration assumption statement: the illustration is based on the observed effect, uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect defined as a fraction of the observed effect. It further distinguishes total events for time-to-event illustrations from participants per arm for other illustrations. These are described as planning assumptions rather than the trial's own design. No numerical planning illustration is reported in the registry record, and the observed primary effect needed to interpret such an illustration is also not reported there.

Planning sample sizes, when presented as illustrations, describe hypothetical design requirements under stated assumptions. They are not observed power and do not describe the actual probability that this completed study detected an effect. This distinction is general statistical guidance. The registry record does not report the trial's own sample-size justification, and no such justification should be inferred from the planning assumptions.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Part A: PTPs ≥12 Years", "Part A: PTPs <12 Years")
n   <- c(12, 30)
m   <- c(1.86, 3.38)
sp  <- c(2.54, 4.17)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Part A: PTPs ≥12 Years  12  1.860  2.540  0.246  3.474
CARM  Part A: PTPs <12 Years  30  3.380  4.170  1.823  4.937

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 15 outcome measures, including bleeding rates, surgery-related assessment, Factor VIII recovery, inhibitor development, and adverse events. Considering multiple outcomes can raise a multiplicity issue: when many statistical tests are conducted, the chance of at least one apparently unusual result can increase. This is a general statistical concern, not a claim that such testing occurred in this study.

The record does not report which outcomes were included in a formal testing hierarchy, whether any multiplicity adjustment was planned, or which outcomes were treated as confirmatory versus descriptive. The number of analyses listed is zero. As a result, the registry record does not give enough information to assess how multiplicity was handled in the analysis, or whether inferential tests were conducted.

Missing-data methods and the extent of missingness for the primary endpoint are not reported in the registry record. The record also does not specify how participants with incomplete follow-up, treatment interruption, or unavailable endpoint measurements were handled. These details matter because the available observations may differ from the observations that would have been collected under complete follow-up. No assumption about missingness or imputation should be made in the absence of a reported method.

The analysis populations are not reported in the registry record. It is therefore unclear from the record which participants were included in each outcome analysis, or whether all enrolled participants contributed to the primary endpoint summary. The registry lists enrollment of 45, but that number alone does not identify the analysis population for each endpoint.

The registry record also does not report an analysis plan specifying covariate adjustment, subgroup testing, or sensitivity analyses. These omissions limit assessment of how the results were generated and how robust they may be. Since the primary outcome result itself is not reported, multiplicity and missing-data considerations cannot be resolved by examining the posted endpoint estimate.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: haemarthrosis (3.3%), epilepsy (3.3%).

The safety figures are organized by the registry's four participant groups: Part A PTPs aged 12 years or older, Part A PTPs under 12 years, Part B PUPs under 6 years, and Part B MTPs under 6 years. The numbers at risk in those groups are 12, 30, 2, and 1, respectively. Serious adverse events affected 0, 2, 0, and 0 participants, respectively. The record lists no deaths in any group.

These are participant counts, not event rates adjusted for time at risk. The figures describe how many participants were listed as affected in each group; they do not indicate how many separate events each affected participant experienced. The registry also lists other adverse events affecting 3, 8, 1, and 1 participants in the respective groups. Those counts should not be combined with the serious-event counts because they represent a separate category in the record.

Haemarthrosis and Epilepsy are listed among the top serious adverse event terms, each at 3.3%. The record does not provide further event-level detail in the registry record for interpretation, such as timing, duration, recurrence, or causal attribution. These safety data are descriptive and, without a control group, do not establish a comparative risk.

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

The study record identifies a completed Phase 4 investigation of KOVALTRY in Chinese participants with severe hemophilia A. It describes a primary endpoint relevant to bleeding during prophylaxis in previously treated patients, and it lists additional safety, efficacy, and pharmacokinetic outcomes. The record also provides safety counts for the listed patient groups.

However, the primary endpoint's numerical mean and standard deviation are not reported in the registry record. There is no posted primary estimate from which to describe the observed annualized bleeding rate, and no reported confidence interval or p-value to characterize its uncertainty. The outcome definition and timeframe explain what the study aimed to measure, but they do not supply the result.

The study was non-randomized and single-group, with no separate control group listed. Accordingly, the posted record does not establish a treatment effect relative to another therapy or a control condition. The group structure separates participants by age and prior treatment, so differences between these groups would not by themselves constitute a randomized comparison.

The adverse-event counts provide a limited descriptive account of safety in the study groups. They do not show a comparative safety profile, and the registry's listed serious event terms do not by themselves establish whether an event was caused by treatment. The record lists no deaths.

These limits do not negate the value of the information the registry does contain. The record identifies the intended population, intervention, study structure, outcome definitions, timeframe, and selected safety counts. It does mean that a statistical conclusion about the primary bleeding outcome or a comparative treatment effect cannot be drawn from the posted results. Outcomes without numerical results are not reported in the registry record.

14. Why This Trial Matters Statistically

This study is statistically relevant because it concerns a defined population and a clinically interpretable outcome: annualized bleeding episodes during prophylaxis among previously treated patients with severe hemophilia A. The registry's age and prior-treatment group descriptions also make clear that the study includes distinct patient categories rather than a single undifferentiated population.

It is equally important to distinguish a well-defined endpoint from a reported result. The registry specifies the endpoint's content, summary type, units, and timeframe, but does not report its numerical mean or standard deviation. Without those values, the study's primary outcome cannot be quantitatively described from the registry record. This is a central limitation for statistical interpretation, rather than a minor reporting detail.

The design also illustrates why study structure matters. A non-randomized, single-group study can document observations in treated participants, but it does not by itself provide a randomized comparison. The distinction prevents descriptive data from being mistaken for comparative evidence. The record's completion status and enrollment figure do not change that design limitation.

Finally, the gap between the listed outcome measures and the absence of posted analyses highlights the need to report estimates, uncertainty, analysis populations, and methods. Those details allow readers to assess both the magnitude and precision of an outcome and the way the analysis handled incomplete or variable data. For this record, several of those items are not reported in the registry record, so interpretation must remain focused on the design and descriptive safety information that is available.

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 trial-specific limitation in the registry record is the absence of numerical results for the primary endpoint. Although the endpoint is defined as a mean annualized bleeding rate with standard deviation, the posted record does not report either value. The record also reports zero analyses, so there is no primary analysis estimate or uncertainty measure to interpret.

The non-randomized, single-group design means there is no listed concurrent control group for comparison. The listed groups differ by age and prior-treatment status, so they should not be read as interchangeable treatment arms. The record does not describe an adjustment strategy for any comparisons across groups.

The registry lists 15 outcome measures but does not report a statistical analysis plan, a multiplicity approach, analysis populations, or methods for missing data. The record also does not explain the calculation details for individual annualized rates or how differing follow-up was handled. These omissions make it difficult to evaluate how endpoint summaries would have been constructed, even apart from the lack of a posted estimate.

Safety figures are limited to group-level participant counts and selected serious event terms. The record does not provide further detail on event timing, recurrence, duration, or causal relationship. The small listed Part B groups also mean those group-level counts describe very few participants; interpretation should remain descriptive and should not be generalized beyond what the record reports.

The stated enrollment is 45, but the analysis populations for individual outcomes are not reported in the registry record. It is therefore not possible to determine from the record how many participants contributed to the primary endpoint or each secondary outcome.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Post Approval Commitment Study to Gain More Information on How Safe and Effective KOVALTRY is in Chinese Children, Adolescents /Adults With Severe Hemophilia A — NCT04565236.
• Registry record last updated 2025-04-18; status last verified 2025-04.
• Results first posted 2025-04-18.
• 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 Phase 4, non-randomized, single-group study sponsored by Bayer, with enrollment listed as 45. It evaluates KOVALTRY in Chinese children, adolescents, and adults with severe hemophilia A, organized into previously treated and previously untreated or minimally treated groups. The primary outcome is mean annualized bleeding rate during prophylaxis in Part A PTPs, measured in bleeds per year over up to 6 months.

The record lists 15 outcome measures and zero analyses. The primary endpoint's numerical result is not reported in the registry record. Safety counts are provided by group, and no deaths are listed. Haemarthrosis and Epilepsy are among the top serious event terms, each reported as 3.3%. The single-group design supports descriptive interpretation but does not provide a randomized treatment comparison.