Observational Safety Study for KALBITOR (Ecallantide) in the Treatment of Acute Attacks of Hereditary Angioedema: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Observational Safety Study for KALBITOR (Ecallantide) in the Treatment of Acute Attacks of Hereditary Angioedema (NCT01059526), a registered phase not stated study. The primary outcome is Occurrence of Anaphylaxis or Other Adverse Events Suggestive of Hypersensitivity.

2. Clinical Question

3. Trial Design

This was a Phase 4, long-term observational safety study of KALBITOR (ecallantide) for acute attacks of hereditary angioedema. Shire is listed as the sponsor. The record gives a start date of 2010-02-01, a primary completion date of 2013-09-01, and a completed status. The enrollment field lists 81 participants.

The study objective was to evaluate antibody formation, allergic reactions, and the risk of hypercoagulability and hypocoagulability in people treated with ecallantide. Its primary outcome concerned anaphylaxis or other adverse events suggestive of hypersensitivity. The endpoint timeframe was 12 months after first treatment. Overall Patient Response Assessment is listed as a secondary outcome.

The record distinguishes patients naive to KALBITOR at enrollment from patients who had previously received it. It does not state how participants were allocated to these groups. This is therefore not a randomized comparison, and the exposure-history groups should not be read as equivalent treatment arms or as a controlled estimate of a treatment effect. Prior exposure may distinguish the groups in ways the registry does not describe.

The primary endpoint population is defined as all patients who received at least one treatment dose of KALBITOR. The adverse-event summary separately lists a safety population with 44 at risk. The registry does not explain how this figure relates to the enrollment field or to the endpoint population definition. Although the record lists four outcome measures, it lists no analyses. The statistical analysis plan, sample-size justification, and details of any interim analyses 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: Subjects were to complete screening/enrollment procedures on a separate day prior to receiving KALBITOR treatment for an acute attack of HAE. The primary and secondary endpoints were analyzed for the Safety population only (all patients who received at least 1 treatment dose of KALBITOR).

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Safety population; defined as all patients who received at least 1 treatment dose of KALBITOR

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: Safety population; defined as all patients who received at least 1 treatment dose of KALBITOR

6. Primary Endpoint

The registry lists the primary outcome as Occurrence of Anaphylaxis or Other Adverse Events Suggestive of Hypersensitivity, measured over 12 months after first treatment.

The primary endpoint is the occurrence of anaphylaxis or other adverse events suggestive of hypersensitivity, expressed as the number of participants. Its timeframe is 12 months after first treatment. The endpoint is based on medical review of multiple treatment-emergent adverse-event terms rather than on a single diagnosis term alone. The listed terms include reports such as anaphylaxis, hypersensitivity, rash, urticaria, dyspnea, and wheezing.

Records matching one or more of the terms were reviewed further. The description says that the review considered timing in relation to dosing, accompanying symptoms, the investigator’s causality assessment, and other available clinical information. The description also says the anaphylaxis subset was determined using criteria established by the NIAID. These steps are intended to distinguish a potential hypersensitivity reaction from a matching term that may not represent such a reaction after clinical review.

General: counting participants with an event makes the endpoint directly interpretable as a safety count in the defined population. A confidence interval conveys the uncertainty around an estimated event frequency; it does not show that the estimate is exact or establish a causal relationship. The registry lists a 95% confidence interval as the endpoint’s dispersion measure, but the result and interval are not reported in the registry record. The endpoint therefore cannot be quantified from the reported primary-outcome information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count measure?

The primary endpoint is a binary outcome at the participant level: a person either meets the endpoint definition during the stated timeframe or does not. Reporting the number of participants with an event makes the outcome a count. It is distinct from an event count, because one person might have more than one event while still counting once for a participant-based endpoint. The registry describes the primary endpoint as the number of participants and gives its population definition, but does not post the observed count.

The endpoint uses clinical review, not merely a search for words in adverse-event reports. The registry description lists multiple treatment-emergent adverse-event terms that could trigger further review. The review considered timing after the start of treatment, accompanying symptoms, the investigator’s causality assessment, and other available clinical information. This distinction matters: a report containing a listed term does not automatically establish that the participant met the endpoint definition. The registry says the anaphylaxis subset used criteria established by the NIAID.

What does a confidence interval add?

The registry identifies a 95% confidence interval as the dispersion measure for the primary outcome. General: a confidence interval presents a range of values compatible with the data under the statistical method used. A narrow interval indicates greater precision than a wide interval, while neither width nor the confidence level removes uncertainty. The interval does not by itself show causation, clinical importance, or whether a result is free from bias. No primary endpoint estimate or interval is reported in the registry record, so its precision cannot be assessed.

Why does the study design affect interpretation?

This is an observational safety study, and allocation is not stated. The record separates participants by whether they had received KALBITOR before enrollment. Such groups are not a randomized comparison or a like-for-like control comparison. General: when groups differ in prior exposure, they may also differ in other characteristics that affect outcomes. Without a stated allocation process and an appropriate analysis addressing relevant differences, a group contrast cannot be interpreted as a causal treatment effect. The record lists no analyses, so it does not establish that any adjustment or comparison was performed.

What can sample-size planning illustrations tell readers?

General: a sample-size calculation describes how much information a planned study might need under specified assumptions. It is not an observed result and is not evidence that a completed study had a particular probability of finding an effect. The registry’s planning assumptions describe 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. The record does not report a sample-size justification as part of the trial’s own design. Any planning illustration based on an observed effect should be read as a hypothetical planning exercise, not as observed power or as evidence of efficacy.

General: normal approximations can be less reliable when event counts are sparse or when the underlying distribution does not fit the approximation well. For counts with extra variability, over-dispersion means the data vary more than a simple model expects; ignoring it can make uncertainty look too small. These are general considerations, not claims that a particular model was used or that over-dispersion was present in this study. The registry record does not report a statistical analysis plan or describe a model for the primary endpoint.

What analysis details are absent?

The record does not report the primary endpoint count, its confidence interval, a hypothesis test, or an analysis comparing the prior-exposure groups. It also does not describe adjustment variables, handling of repeated events, or a method for missing outcome data. Those details are necessary for evaluating how the estimate was produced and how robust it is. They are not recoverable from the endpoint definition alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures, including Overall Patient Response Assessment as a secondary outcome. It lists no analyses. The record does not say whether outcomes were tested using a prespecified hierarchy, whether adjustment for multiple comparisons was planned, or whether any outcomes were considered exploratory. Multiplicity procedures and the analysis plan are not reported in the registry record. Accordingly, a reader cannot determine whether any inferential claims would account for evaluating several outcomes.

The primary endpoint description identifies a safety population as all patients who received at least one treatment dose of KALBITOR. The adverse-event summary lists 44 at risk, while the enrollment field lists 81 participants. The record does not explain the relationship between those figures or give a participant flow accounting for eligibility, treatment exposure, follow-up, and endpoint availability. The reason for any difference is not reported in the registry record.

The registry does not describe how missing follow-up, incomplete adverse-event information, or withdrawals were handled for the primary endpoint. It does not say whether participants without complete follow-up were counted as having no event, excluded, or handled through another method. These are distinct choices that can affect an event estimate, particularly when follow-up is incomplete; no specific approach can be attributed to this study from the registry record.

The endpoint timeframe is 12 months after first treatment, but the registry does not report how much follow-up was available for each participant or whether all participants completed that timeframe. It also does not report interim analyses, stopping rules, or the protocol’s statistical plan. Those omissions limit assessment of outcome selection, analysis populations, and the handling of incomplete data. No assumptions about these procedures should be made.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 3% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: dehydration (4.5%), hereditary angioedema (4.5%), drug ineffective for unapproved indication (2.3%), anaphylactic reaction (2.3%), erythema (2.3%).

The adverse-event summary lists 44 participants at risk in the safety population. It records 6 affected in the serious adverse-event category and 14 affected in the other adverse-event category. These are counts of participants affected, as the record frames the categories; they are not the primary endpoint result. The registry record does not clarify whether a participant could appear in both categories, so the counts should not be added or treated as mutually exclusive.

The serious-term list gives dehydration at 4.5%, hereditary angioedema at 4.5%, drug ineffective for unapproved indication at 2.3%, anaphylactic reaction at 2.3%, and erythema at 2.3%. The denominator for these term-specific percentages is not reported in the registry record. The terms may describe different kinds of events and should not be combined into a single percentage. Nor do these term listings show which reports met the primary endpoint’s clinical-review definition.

The deaths field is not reported in the registry record. This should not be read as evidence that no deaths occurred. More generally, adverse-event summaries describe what was recorded under the stated categories; without details about ascertainment, follow-up completeness, and event-level overlap, they do not establish a causal relationship to treatment.

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

The study addresses a safety question about ecallantide exposure in people with hereditary angioedema, with particular attention to antibody formation and allergic or hypersensitivity events. Its primary endpoint is specifically defined around anaphylaxis or other events suggestive of hypersensitivity, and the registry describes medical review intended to assess those reports. This makes the endpoint definition more clinically specific than a simple count of every report containing a potentially relevant term.

However, the registry record does not report the primary endpoint count or its 95% confidence interval. It therefore does not establish how often participants met that endpoint or how precise an estimate would be. The adverse-event summary’s counts and serious-term percentages provide additional safety information, but they are not a substitute for the primary endpoint result. The registry does not report the denominator for the term percentages, and it does not state whether categories overlap.

The observational design also limits causal interpretation. The groups are defined by prior KALBITOR exposure, allocation is not stated, and the record says they are not a like-for-like control comparison. Differences between such groups cannot be attributed to treatment or prior exposure based on this information alone. No group-comparison analysis is listed.

These points do not mean that the study found no safety events, nor do the listed adverse-event terms by themselves establish that treatment caused them. They mean that the registry record supports a description of the study’s aims, endpoint definition, and some adverse-event summaries, while leaving key information needed for a quantitative interpretation of the primary outcome unreported. The record also does not provide a basis for judging the study’s statistical power or for making conclusions about treatment efficacy.

13. Why This Trial Matters Statistically

Safety studies need endpoints that can distinguish a clinically meaningful event from a broad collection of reported symptoms or diagnostic terms. This record’s primary outcome description makes that distinction explicit: potential hypersensitivity reports were identified using multiple terms and then reviewed in light of timing, symptoms, causality assessment, and other clinical information. That approach highlights an important statistical issue: the operational definition of an outcome determines what is counted and what an estimated frequency would mean.

The record also illustrates why population accounting matters. It lists enrollment of 81 and an adverse-event summary with 44 at risk, while defining the primary endpoint safety population by treatment exposure. Without an explanation linking these figures, readers cannot confidently reconcile the enrolled population with the population represented in the adverse-event summary. Clear participant flow and endpoint availability are central to understanding the scope of a safety estimate.

Observational exposure groups raise a different interpretive issue. Prior treatment history defines the groups, but allocation is not stated and the groups are not a like-for-like control comparison. Statistical comparisons between groups would require careful consideration of baseline differences and the study’s analysis plan. The registry lists no analyses, so it does not show how such concerns were addressed.

Finally, a well-described endpoint is not enough to establish the result. The registry states the outcome timeframe and confidence-interval measure, yet does not report the endpoint estimate or interval. This demonstrates the difference between a study’s question and the evidence available to answer it. Transparent reporting of counts, denominators, uncertainty, and missing-data handling is essential for readers to assess both safety findings and their precision.

14. 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 that the primary endpoint result is not reported. Although the record defines the endpoint, its timeframe, population, and confidence-interval measure, it gives no event count or interval. The primary safety question therefore cannot be answered quantitatively from the registry information.

The relationship between enrollment and the adverse-event summary is also unclear. Enrollment is listed as 81, while the adverse-event summary lists 44 at risk. The record defines the primary endpoint population as participants who received at least one dose, but does not provide a participant-flow explanation reconciling the figures. It does not report whether all eligible participants received treatment or had follow-up through the endpoint timeframe.

The study is observational, and the record does not state allocation. The prior-exposure groups are not a like-for-like control comparison. The registry does not report an analysis comparing these groups, adjustment for possible differences, or a protocol statistical plan. This restricts causal interpretation and prevents assessment of the intended analysis strategy.

Further limitations include the absence of reported missing-data procedures, multiplicity methods, interim-analysis details, and sample-size justification. The serious adverse-event term percentages have no denominator stated in the record, and the record does not explain possible overlap between terms or categories. The deaths field is also not reported. Together, these omissions limit assessment of the completeness, precision, and interpretation of the safety information. They should be treated as reporting gaps, not as evidence that a particular event or analysis did not occur.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Observational Safety Study for KALBITOR (Ecallantide) in the Treatment of Acute Attacks of Hereditary Angioedema — NCT01059526.
• Registry record last updated 2021-06-08; status last verified 2021-05.
• Results first posted 2014-10-06.
• 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.

18. Record Summary

NCT01059526 is a completed Phase 4 observational safety study of ecallantide (KALBITOR) for acute attacks of hereditary angioedema, sponsored by Shire. The record lists a start date of 2010-02-01, a primary completion date of 2013-09-01, and enrollment of 81.

The primary endpoint is the number of participants with anaphylaxis or other adverse events suggestive of hypersensitivity within 12 months after first treatment. It uses a safety population defined by receipt of at least one dose and a 95% confidence interval. The registry record does not report the primary endpoint result or interval. It lists Overall Patient Response Assessment as a secondary outcome and lists no analyses.

The adverse-event summary lists 44 at risk, 6 affected in the serious category, and 14 affected in the other category. Serious-term percentages are reported, but their denominator is not stated. The record does not explain the difference between the enrollment and at-risk figures or report missing-data procedures, multiplicity methods, or the statistical analysis plan.