This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for A Phase 3 Study to Evaluate the Long-term Safety, Tolerability and Efficacy of Efgartigimod PH20 SC in Adult Participants With Bullous Pemphigoid (NCT05681481), a na phase 3 study. The primary outcome is Number of Participants With Treatment-emergent AEs, SAEs and AESIs.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05681481 |
| Phase | Phase 3 |
| Condition | Bullous Pemphigoid |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 64 |
| Arms in the primary outcome | n/a |
| Lead sponsor | argenx |
| Results posted | Yes |
2. Clinical Question
Population
Adults with moderate-to-severe bullous pemphigoid who completed ARGX-113-2009 and rolled over to this extension study. The safety analysis set was narrower: participants had to provide informed consent for ARGX-113-2010 and receive at least 1 dose of efgartigimod PH20 SC in the extension. The registry lists enrollment of 64, while the safety data list 50 participants at risk.
Intervention
Efgartigimod PH20 SC, described as being given on top of Prednisone. During the treatment period, participants could receive efgartigimod PH20 SC according to their clinical status. Oral or topical corticosteroids could also be administered at the investigator's discretion.
Comparator
There was no concurrent comparator group. The study is described as open-label and single-group, with no masking and no randomized allocation. Participants who were not receiving efgartigimod PH20 SC could enter an observation period, but this was part of the extension rather than a randomized control arm.
Primary question
Among participants who entered the extension and received at least 1 dose, how many experienced treatment-emergent adverse events, serious adverse events, or adverse events of special interest during a timeframe of up to 56 weeks? The record also lists several remission and relapse outcomes, but it reports no analyses for them.
The central question is therefore about longer-term safety experience in a group continuing from an earlier study, not a comparison of treatment against a control. The registry describes efficacy as an additional aim, with outcomes concerning remission and relapse. Without posted efficacy analyses, those aims cannot be translated into estimates of benefit or change over time. The open-label, single-group design can describe events in the participants observed, but it cannot separate the contribution of study treatment from other influences such as the underlying condition, prior treatment, or corticosteroid use. The record does not report an untreated or alternative-treatment group that could support a like-for-like comparison.
3. Trial Design
This is a Phase 3, open-label extension study of efgartigimod PH20 SC in adults with bullous pemphigoid. Its official title describes an extension of ARGX-113-2009. Eligible participants could roll over from that main study after completing it. The registry lists enrollment of 64. The study began on 2023-03-22, had a primary completion date of 2025-03-20, and is listed as terminated. The reason for termination is not reported in the registry record.
The study has a single group, no masking, and no randomized allocation. The intervention description identifies participants as receiving efgartigimod PH20 SC on top of Prednisone. The brief summary describes a treatment period of up to 48 weeks, during which efgartigimod PH20 SC could be given according to clinical status. Participants not receiving it could enter an observation period; if they relapsed, they could re-enter treatment. A follow-up period of 8 weeks followed the treatment and observation period. Visit timing was described in the record, but actual treatment exposure and time in each period are not reported in the registry record.
Oral or topical corticosteroids could be given at the investigator's discretion. This means participants' treatment was not described as a fixed, identical regimen throughout the extension. That context matters when interpreting event counts and any future efficacy summaries, because treatment status and co-treatment could vary. The registry lists 14 outcome measures and identifies safety as the primary outcome, with a timeframe of up to 56 weeks. It lists no analyses. Details of the statistical protocol, the reason for the planned enrollment, and any planned interim analyses are not reported in the registry record.
The safety analysis set is defined as participants who rolled over from ARGX-113-2009, consented to ARGX-113-2010, and received at least 1 dose of efgartigimod PH20 SC in the extension. That definition differs from the overall enrollment count. The posted safety data use 50 participants at risk, so the two totals should not be treated as interchangeable denominators. The record does not give a participant flow accounting for the difference.
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: The study enrolled participants with bullous pemphigoid (BP) who completed the week-36/end-of-treatment period (EoTP) visit in ARGX-113-2009. A total of 64 participants (of 98 eligible participants) rolled over from ARGX-113-2009.
Overall Study
| Stage | Efgartigimod PH20 SC |
|---|---|
| STARTED | 64 |
| COMPLETED | 17 |
| NOT COMPLETED | 47 |
Reasons for not completing this period:
| Reason | Efgartigimod PH20 SC |
|---|---|
| Adverse Event | 5 |
| Death | 1 |
| Lost to Follow-up | 2 |
| Participant-specified withdrawal criterion met | 1 |
| Physician Decision | 3 |
| Study terminated by sponsor | 26 |
| Withdrawal by Subject | 7 |
| Withdrawal of consent | 2 |
Analysis population for the primary outcome, as defined in the registry: Safety analysis set: all participants who rolled over from ARGX-113-2009, provided informed consent for ARGX-113-2010, and received at least 1 dose of efgartigimod PH20 SC in ARGX-113-2010.
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.
| Characteristic | Unit | Efgartigimod PH20 SC |
|---|---|---|
| Participants analysed | 64 | |
| Age, Continuous | years | 70.6 (SD 10.17) |
| Sex: Female, Male: Female | Participants | 48 |
| Sex: Female, Male: Male | Participants | 16 |
| Race/Ethnicity, Customized: Asian | Participants | 10 |
| Race/Ethnicity, Customized: White | Participants | 52 |
| Race/Ethnicity, Customized: Other | Participants | 2 |
| Race/Ethnicity, Customized: Hispanic or Latino | Participants | 1 |
| Race/Ethnicity, Customized: Not Hispanic or Latino | Participants | 63 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants With Treatment-emergent AEs, SAEs and AESIs, measured over Up to 56 weeks.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the number of participants with treatment-emergent adverse events, serious adverse events, and adverse events of special interest. The registry gives a timeframe of up to 56 weeks and defines the safety analysis set as participants who rolled over from ARGX-113-2009, consented to the extension, and received at least 1 dose of efgartigimod PH20 SC. The record identifies infections and infestations as adverse events of special interest because efgartigimod causes a transient reduction in total IgG levels.
This endpoint is used to describe the safety experience during longer-term exposure and follow-up. Counting participants with events addresses how many people in the safety set experienced an event in a category; it is not the same as counting every event, because one participant may experience more than one event. The registry record does not give event-level timing, exposure-adjusted rates, or detailed rules for assigning events to the treatment-emergent period. It also does not show separate estimates by treatment or observation period.
Counts can help characterize what was observed in the enrolled safety population, but a single-group count cannot establish whether treatment caused an event or whether the count differs from what would have occurred without treatment. Seriousness and special-interest classification describe categories of safety monitoring; they do not by themselves provide a causal conclusion. The endpoint is a safety measure, not a direct test of efficacy. Although the registry lists remission and relapse outcomes, their results are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted safety data list 13 participants with serious adverse events among 50 at risk in the efgartigimod PH20 SC group. They also list 38 participants with other adverse events among 50 at risk and 1 death. These are counts of participants, not counts of all events. The categories may overlap, so they should not be added together to create a total number of affected participants. The record does not report whether the death was considered related to study treatment, nor does it provide a causal assessment for the serious events.
Several serious adverse event terms are listed at 2.0% each: Anaemia, Cardiac failure, Abdominal distension, Condition aggravated, General physical health deterioration, and Oedema peripheral. Those entries describe the listed terms, not a comparative risk. The record does not provide the number of events per term, information about their timing, or an analysis comparing these events with another group. A term appearing in the list does not establish that treatment caused it.
Interpretation is constrained by the design. Participants entered from a preceding study, there was no randomized comparator, and the study was open-label. As a general statistical point, an uncontrolled extension can describe events observed among participants who continue into it, but it cannot isolate a treatment effect from background illness, prior exposure, changes in treatment, or the selection of participants who entered the extension. The allowance for investigator-discretion corticosteroids and treatment according to clinical status adds variation in exposure that is not summarized by the posted counts.
The registry lists enrollment of 64, but the safety data use 50 participants at risk. The safety set required rollover, consent, and receipt of at least 1 dose, so it is not defined as every enrolled participant. The reason for the difference and the disposition of the remaining participants are not reported in the registry record. Counts should therefore be read with the stated safety denominator rather than assumed to represent all enrolled participants.
No efficacy analyses are listed, despite remission and relapse outcomes appearing among the registered measures. The record also does not report confidence intervals, hypothesis tests, adjusted estimates, or other measures of precision for the safety counts. Thus the counts describe the posted safety experience, while the precision and comparative meaning of those observations remain uncertain. The study's terminated status is recorded, but the reason is not reported in the registry record and should not be inferred from the status alone.
Planning illustrations based on an observed effect, where shown in the statistical material, are not observed trial outcomes. The stated assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and detection of a stated fraction of an observed effect. Such hypothetical calculations do not turn this single-group study into a randomized comparison, and they are not observed power. No observed efficacy effect or sample-size illustration values are reported in the registry record.
9. Statistical Methods Explained
What does a count of participants measure?
For this primary outcome, the unit is participants. A count of participants with an event answers how many people in the defined safety set experienced at least one event in the relevant category. It does not state how many event episodes occurred. One person can have multiple events, and one person can meet more than one event category. As a general statistical distinction, participant counts and event counts answer different questions: the former describe how many people were affected, while the latter describe the volume of recorded episodes.
The registry lists 13 participants with serious adverse events, 38 with other adverse events, and 1 death among the efgartigimod PH20 SC group, with 50 at risk. These figures should retain their category labels. They should not be summed, because overlap is not described, and the registry does not establish that the groups are mutually exclusive. The listed serious adverse event terms each have a frequency of 2.0%; the record does not state event timing or provide term-specific event counts in the posted information.
Why does the analysis population matter?
The safety analysis set includes participants who rolled over from ARGX-113-2009, consented to ARGX-113-2010, and received at least 1 dose of efgartigimod PH20 SC in the extension. That is a defined subset, not automatically the same as everyone enrolled. The registry lists enrollment of 64 and 50 participants at risk in the safety data. A denominator must match the population to which a count refers; interpreting the count against a different population would change the question being answered. The registry does not explain the participant flow between enrollment and the safety set.
As a general principle, restricting a safety analysis to people who received treatment can be appropriate for describing exposure-related safety observations. However, the resulting group may differ from all those initially enrolled. The posted record does not report additional analysis populations or describe how participants without a dose were handled in other outcomes.
What can an uncontrolled extension estimate?
A single-group study can summarize the events observed in its participants. It does not directly estimate a difference between treatment and control, because there is no concurrent randomized comparator. In general, random allocation helps balance measured and unmeasured influences between comparison groups, while an open-label design can affect reporting or assessment. Neither feature means that a particular event was caused by treatment; causal attribution requires evidence beyond a group count.
Participants could move between treatment and observation according to their clinical status, and corticosteroids could be administered at the investigator's discretion. The registry gives no analysis stratified by those treatment circumstances. As a general matter, variation in exposure and co-treatment can complicate interpretation of outcomes over time. A count without person-time or event timing cannot show how rates changed across exposure periods.
How should statistical precision be understood?
A confidence interval, in general, is a range of values compatible with the data under a specified statistical model; it conveys uncertainty rather than certainty about the true value. No confidence intervals are reported in the registry record for the primary safety results. Nor are hypothesis tests, adjusted estimates, or exposure-adjusted rates listed. Consequently, the posted counts do not by themselves quantify the precision of an underlying event frequency or support a statistical comparison.
For event-count data, the number of observed people and the underlying risk period both affect precision. Where follow-up time varies, a participant count alone does not account for differing exposure duration. The registry's primary timeframe is up to 56 weeks, but actual follow-up and treatment duration for each participant are not reported in the registry record. This limits interpretation of the counts as a rate over time.
What do the planning illustrations mean?
The statistical material describes planning illustrations based on an observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. The target effect is described as a stated fraction of the observed effect. These are hypothetical planning assumptions, not a description of the study's single-group design. They should not be read as the trial's own sample-size justification, evidence that the study had a particular probability of detecting an effect, or observed power. The registry does not report the actual sample-size rationale, and no numerical planning illustration values or observed efficacy effects are reported in the registry record.
In general, a significance level is a decision threshold used in a testing plan; it does not measure the size or clinical importance of an effect. A planning calculation also depends on its assumed effect and design. Since the registry describes no randomized two-arm comparison and lists no analyses, the stated planning assumptions cannot be used to infer a treatment comparison for this study.
Why can over-dispersion matter in other count analyses?
As a general statistical concept, over-dispersion occurs when count variability is greater than assumed by a model. A model that understates variability can produce uncertainty estimates that are too narrow. This is relevant when analyzing event totals, especially where individuals may have different underlying event tendencies or exposure time. The posted primary result is expressed as participants with events, and no count-model specification or over-dispersion assessment is reported in the registry record. No claim about over-dispersion in this study can therefore be made from the posted information.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 14 outcome measures, including the primary safety endpoint and secondary remission and relapse measures. It lists 0 analyses. No multiplicity strategy is reported in the registry record: there is no stated hierarchy for testing outcomes, adjustment method, or definition of which efficacy outcomes would be treated as confirmatory. As a general statistical point, evaluating multiple outcomes can increase the chance of at least one apparently notable result when each is assessed separately. A prespecified approach can clarify how such results should be interpreted, but none is described in the record.
Missing-data methods are not reported in the registry record. The record does not describe how missing observations, withdrawals, incomplete follow-up, or missing outcome assessments were handled. Nor does it report sensitivity analyses to evaluate the effect of missing data. For outcomes observed over time, missingness may affect how duration, relapse, or remission is summarized; without the analysis details, those implications cannot be assessed.
The primary safety population is specified: participants who rolled over from ARGX-113-2009, consented to the extension, and received at least 1 dose of efgartigimod PH20 SC. The record does not report a corresponding efficacy analysis population or provide participant flow accounting for enrollment of 64 versus 50 at risk in the safety data. The reason for termination and any interim analyses are also not reported in the registry record. These omissions limit assessment of whether the posted outcomes, if later added, would reflect all participants as planned or a selected subset.
No statistical analysis plan is described. Details such as adjustment for baseline characteristics, handling of repeated measures, rules for censoring, and definitions of the analysis sets beyond the stated safety set are not reported in the registry record. Those features should not be inferred from the list of outcomes alone.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Efgartigimod PH20 SC | 13 | 50 | 26.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Efgartigimod PH20 SC | 1 of 50 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Efgartigimod PH20 SC | 38 of 50 |
Most frequent serious adverse event terms
| Event term | Organ system | Efgartigimod PH20 SC |
|---|---|---|
| Anaemia | Blood and lymphatic system disorders | 1 of 50 |
| Cardiac failure | Cardiac disorders | 1 of 50 |
| Abdominal distension | Gastrointestinal disorders | 1 of 50 |
| Condition aggravated | General disorders | 1 of 50 |
| General physical health deterioration | General disorders | 1 of 50 |
| Oedema peripheral | General disorders | 1 of 50 |
| Appendicitis | Infections and infestations | 1 of 50 |
| Gastroenteritis viral | Infections and infestations | 1 of 50 |
| Herpes zoster | Infections and infestations | 1 of 50 |
| Pneumonia | Infections and infestations | 1 of 50 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Efgartigimod PH20 SC |
|---|---|---|
| Arthralgia | Musculoskeletal and connective tissue disorders | 5 of 50 |
| Back pain | Musculoskeletal and connective tissue disorders | 5 of 50 |
| Injection site paraesthesia | General disorders | 4 of 50 |
| Oedema peripheral | General disorders | 4 of 50 |
| Nasopharyngitis | Infections and infestations | 4 of 50 |
| Urinary tract infection | Infections and infestations | 4 of 50 |
| Diarrhoea | Gastrointestinal disorders | 3 of 50 |
| Nausea | Gastrointestinal disorders | 3 of 50 |
| Insomnia | Psychiatric disorders | 3 of 50 |
| Pruritus | Skin and subcutaneous tissue disorders | 3 of 50 |
Serious events with the highest arm-level rate: anaemia (2.0%), cardiac failure (2.0%), abdominal distension (2.0%), condition aggravated (2.0%), general physical health deterioration (2.0%).
The serious adverse event data list 13 affected participants among 50 at risk in the efgartigimod PH20 SC group. The same record lists 38 participants with other adverse events and 1 death. These are participant counts, and the categories may overlap. They are not a count of distinct people across all categories, and the registry does not report whether the death was considered treatment-related.
The serious adverse event terms listed are Anaemia, Cardiac failure, Abdominal distension, Condition aggravated, General physical health deterioration, and Oedema peripheral, each at 2.0%. The entries indicate that these terms were reported in the safety record; they do not establish causation. The record does not provide event-level details, timing, severity grading, or a comparison group. It also does not report exposure-adjusted rates or confidence intervals.
As a general interpretive point, serious adverse events are a classification of events and should not be equated automatically with treatment causation or with a measure of symptom intensity. A count in a single-group extension describes what was recorded among participants in that analysis set. It cannot establish what the event frequency would have been under another treatment or without treatment. The terminated status does not explain the safety observations or their cause; the reason for termination is not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The registry record documents a planned extension study intended to evaluate longer-term safety, tolerability, and efficacy of efgartigimod PH20 SC in adults with bullous pemphigoid who completed ARGX-113-2009. Its posted safety data describe participants with adverse events in a single group. The record lists 13 participants with serious adverse events, 38 with other adverse events, and 1 death among 50 at risk. These observations characterize the recorded safety experience for the stated population and timeframe, but they do not identify the cause of each event.
The record does not report analyses for the listed remission, relapse, or other outcome measures. As a result, it does not establish an efficacy estimate, the degree of change in disease outcomes, or the precision of any such estimate. The record also does not provide comparative results, since there was no randomized control group. The described use of efgartigimod according to clinical status and possible corticosteroid use means that exposure and co-treatment could vary across participants.
As a general statistical principle, an observed event count is descriptive. A comparison group and an analysis plan are needed to support a treatment contrast, and causal conclusions require more than observing events after treatment. The single-group, open-label design is useful for recording experience during an extension but cannot by itself distinguish treatment-related events from events associated with the condition, background risks, or other care.
The enrollment figure and the safety denominator refer to different populations: enrollment is 64, while the safety data list 50 at risk and use a specified safety-set definition. The registry does not explain the participant flow between them. The study is listed as terminated, but no reason is reported in the registry record. These registry entries should be kept separate from conclusions about efficacy or safety, neither of which can be inferred from termination status alone.
13. Why This Trial Matters Statistically
Extension studies address a different statistical question from randomized comparative trials. They can collect longer-term observations among participants who completed an earlier study and continued into follow-up. In this record, participants could receive efgartigimod PH20 SC according to clinical status, enter observation when not receiving it, and re-enter treatment if they relapsed. The design therefore describes ongoing clinical follow-up rather than a fixed comparison between assigned groups.
That design makes clear reporting of analysis populations and exposure important. The registry defines a safety set that required rollover, consent, and at least 1 dose, and lists 50 participants at risk against overall enrollment of 64. The difference is not explained in the record. Understanding how participants entered the analysis and how long they were observed is essential to interpreting counts, but participant-level follow-up duration is not reported.
Statistically, the record is also notable for the gap between registered outcomes and posted analyses. It lists 14 measures, including safety, remission, and relapse outcomes, but lists 0 analyses. That means the safety counts can be described, while efficacy outcomes cannot be evaluated from the posted record. The absence of comparative estimates is particularly important in a single-group, open-label study, where descriptive observations cannot establish a treatment contrast.
The record's value is therefore in defining the intended extension design and documenting a limited set of safety counts. It also illustrates why interpretation depends on the denominator, event classification, follow-up, and comparator structure—not only on the clinical topic or Phase 3 label. Statistical transparency about missing data, multiplicity, analysis populations, and the reason for termination would help readers understand the evidence more fully, but those details are not reported in the registry record.
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.
Several limitations are specific to this trial record. The study is open-label and single-group, with no randomized allocation or concurrent control. As a result, it does not support a like-for-like comparison against another intervention or against no study treatment. Any observed event count is descriptive and cannot alone identify a treatment-caused risk.
Participants entered from ARGX-113-2009, so the extension population consists of people who completed the earlier study and then met the extension's entry and safety-set conditions. This is not necessarily representative of all adults with bullous pemphigoid. The registry lists 64 enrolled participants but 50 at risk in the safety data; participant flow explaining the difference is not reported in the registry record.
Treatment could depend on clinical status, participants could move into observation and return to treatment after relapse, and oral or topical corticosteroids could be administered at investigator discretion. The registry does not report how long each participant received treatment, their individual follow-up time, or outcomes broken down by treatment status or corticosteroid use. These details constrain assessment of exposure and event timing.
The study is listed as terminated, but its reason for termination is not reported in the registry record. Although 14 outcomes are listed, no analyses are listed, and no efficacy results are reported. Missing-data methods, multiplicity handling, interim analyses, and a detailed statistical analysis plan are also not reported. The available safety counts lack reported confidence intervals, comparative estimates, and exposure-adjusted rates. Together, these gaps limit evaluation of precision, completeness, and causal interpretation.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Phase 3 Study to Evaluate the Long-term Safety, Tolerability and Efficacy of Efgartigimod PH20 SC in Adult Participants With Bullous Pemphigoid — NCT05681481.
- Registry record last updated 2026-02-25; status last verified 2026-02.
- Results first posted 2026-02-25.
- 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.
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18. Record Summary
NCT05681481 is a Phase 3 open-label extension study of efgartigimod PH20 SC in adults with bullous pemphigoid who completed ARGX-113-2009. It is a single-group study with no masking or randomized allocation. The registry lists enrollment of 64 and status as terminated; the reason for termination is not reported in the registry record.
The primary outcome is the number of participants with treatment-emergent adverse events, serious adverse events, and adverse events of special interest, over a timeframe of up to 56 weeks. The stated safety set required rollover, consent, and at least 1 dose in the extension. Posted safety data list 13 participants with serious adverse events, 38 with other adverse events, and 1 death among 50 at risk. The record lists 14 outcomes and 0 analyses. Remission and relapse results, missing-data methods, multiplicity procedures, and a detailed statistical plan are not reported in the registry record.