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 Long-Term Open-Label, Safety Study Of Sitaxentan Sodium In Japanese Pulmonary Arterial Hypertension Patients (NCT01210443), a non-randomized phase 3 study. The primary outcome is Number of Participants With Adverse Events.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01210443 |
| Phase | Phase 3 |
| Condition | Hypertension, Pulmonary |
| Allocation | Non-Randomized |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 2 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
Japanese subjects with pulmonary arterial hypertension were the intended population. The registry record reports enrollment of 2 participants. The safety analysis set is defined as all subjects who received at least one dose of study drug during the extension study; the record does not state how many participants received a dose or confirm how many met that definition.
Intervention
The intervention was sitaxentan, described as sitaxentan sodium in the study title and summary. The summary describes investigation of 100 mg once daily, alone or in combination with another medication. The registry record does not give participant-level dosing, treatment duration, or details of any concomitant medication actually used.
Comparator
There was no comparator arm. The study is listed as non-randomized, open-label, and single-group. Consequently, it does not provide a randomized comparison with another treatment, placebo, or usual care.
Primary question
The primary endpoint counts participants with adverse events, including severe and serious adverse events, during follow-up described as up to 22 days, ending at the last participant discontinuation. The record’s posted safety figures report 0 participants with serious adverse events and 1 with other adverse events in the sitaxentan group.
The clinical question is therefore descriptive: what safety events were recorded among the participants in this small, uncontrolled study? Its design can document events that occurred during the observed study period, but it cannot establish whether an event was caused by treatment or compare event frequency against a control group. The record also lists clinical worsening, change in 6-minute walk distance, change in World Health Organization functional class, and change in blood concentration of NT-pro BNP as secondary outcomes. Numerical results for those outcomes are not reported in the registry record.
3. Trial Design
This was a Phase 3, multi-center, open-label study of sitaxentan sodium in Japanese subjects with pulmonary arterial hypertension. Its registered design was single-group and non-randomized, with no masking. The intervention listing names sitaxentan, and the arm is called Sitaxentan treatment. No separate control arm is described.
The registry reports enrollment of 2 and a status of terminated. The recorded study start is 2010-11, and primary completion is recorded as 2010-12. These registry dates do not by themselves explain the circumstances of termination, how much treatment each participant received, or why enrollment was limited; those details are not reported in the registry record.
The primary safety timeframe is up to 22 days, ending at the last participant discontinuation. The safety analysis set is defined as participants who received at least one dose during the extension study. The registry record does not report participant-level follow-up times or state how many enrolled participants received a dose.
The design is appropriate to describe events observed in the treated group, but it does not support a randomized treatment contrast. Open-label status means masking was not used; the record does not describe additional procedures to reduce subjective assessment or reporting effects. The reason for selecting a single-group design, the protocol’s sample-size justification, and any planned interim analyses are not reported in the registry record. The record lists secondary outcomes concerning clinical worsening, functional capacity, functional class, and NT-pro BNP, but numerical findings for them are not reported.
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: Participants received one 100 mg film-coated tablet of sitaxentan daily for 12 weeks in preceding B1321052 study.
Overall Study
| Stage | Sitaxentan Treatment |
|---|---|
| STARTED | 2 |
| COMPLETED | 0 |
| NOT COMPLETED | 2 |
Reasons for not completing this period:
| Reason | Sitaxentan Treatment |
|---|---|
| Study terminated by sponsor | 2 |
Analysis population for the primary outcome, as defined in the registry: The safety analysis set is defined as all subjects who receive at least one dose of study drug during this extension study.
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 | Sitaxentan Treatment |
|---|---|---|
| Participants analysed | 2 | |
| Age, Customized: <=18 years | Participants | 0 |
| Age, Customized: 19-64 years | Participants | 1 |
| Age, Customized: >=65 years | Participants | 1 |
| Sex: Female, Male: Female | Participants | 2 |
| Sex: Female, Male: Male | Participants | 0 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants With Adverse Events, measured over Up to 22 days (last participant discontinuation).
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the number of participants with adverse events. Its description includes any adverse events, severe adverse events, and serious adverse events. The unit is participants, so the endpoint concerns how many people experienced an event rather than how many event episodes occurred. The registry gives a timeframe of up to 22 days, tied to the last participant discontinuation.
Safety endpoints are used to characterize events observed while participants receive or are followed after an intervention. Counts can make clear whether any events were recorded in a study group and can distinguish serious events from other adverse events when the registry reports those categories. Such counts are descriptive: in an uncontrolled study, they do not determine whether the intervention caused an event, nor do they estimate how the event rate compares with an untreated or differently treated group.
The posted safety grouping reports 0 participants with serious adverse events and 1 participant with other adverse events, with 2 at risk in each category. It does not provide a separate count for severe adverse events, despite severe events being included in the endpoint description. Specific serious adverse event terms are not listed, and deaths are not reported as a numerical value. Further endpoint definitions, including event collection and coding procedures, are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry reports a total enrollment of 2 and a single sitaxentan treatment group. In the posted safety figures, 2 participants are listed as at risk for serious adverse events, with 0 affected. For other adverse events, 2 are listed as at risk and 1 affected. These are counts from a very small group, not comparative estimates. The record does not report a control group against which to judge whether the observed counts differ from what would otherwise have occurred.
The zero serious-event count is a description of the observations recorded for this group and timeframe. It should not be read as evidence that serious events cannot occur, or as a precise estimate of the underlying risk. In a small study, a count can change substantially with the experience of an additional participant. No confidence interval or other uncertainty estimate for these counts is reported in the registry record, so the precision of an underlying event frequency is not quantified there.
The other-adverse-event count indicates that an event was recorded for 1 participant. The registry excerpt does not identify the event term, severity, timing, duration, or relationship to treatment. It is therefore not possible to characterize the clinical nature of that event from the posted information. The endpoint description mentions severe adverse events, but a separate severe-event count is not reported.
The study is listed as terminated, and its primary safety timeframe is up to 22 days, ending at the last participant discontinuation. The short stated observation window and limited enrollment constrain interpretation. The record does not explain the reason for termination or provide detail about the duration of observation for each participant. It also does not report numerical results for the secondary outcomes on clinical worsening, 6-minute walk distance, functional class, or NT-pro BNP.
These findings should be read as a brief record of observed safety counts, not as a test of treatment efficacy or a definitive assessment of safety. No statistical analyses are reported in the registry record. The results do not establish causation, comparative safety, or a stable estimate applicable to a broader population.
9. Statistical Methods Explained
The registry describes a single-group safety study and reports participant counts rather than a randomized contrast. The statistical meaning of those counts is limited by the design and the amount of information available. General explanations below describe how such data are usually interpreted; they do not imply that an unreported analysis was performed for this trial.
What does a participant count represent?
A count of participants with an event records how many people experienced at least one event in the relevant category. This differs from a count of event episodes: a participant may experience more than one event, but the endpoint is expressed in participants. The record reports 0 participants with serious adverse events and 1 with other adverse events, with 2 at risk in each category. It does not give event-level details that would allow episodes to be counted or described.
Counts are often paired with a denominator to convey how many people were observed for an outcome. Interpretation depends on who qualified for that denominator and how long they were followed. Here, the endpoint timeframe is up to 22 days, and the safety analysis set is defined by receipt of at least one dose. The record does not state how many enrolled participants received a dose or provide individual observation times. The posted at-risk counts describe the groups used in the safety summary, but do not explain whether follow-up was complete for every participant.
Why is a comparison important?
General statistical principle: a treatment effect is usually assessed by comparing outcomes under different treatment conditions, with randomization helping balance known and unknown prognostic factors on average. This study is listed as non-randomized and single-group, so it has no concurrent control arm. The adverse-event counts describe what was recorded in the sitaxentan group; they cannot isolate a treatment effect from the underlying condition, other medication, background event occurrence, or other influences. The registry does not report a planned external comparison.
How should uncertainty be understood?
General statistical principle: a confidence interval gives a range of values compatible with the observed data under a specified statistical model and sampling assumptions. It is used to communicate how uncertain an estimate is, rather than to guarantee that the true value lies within a particular interval. For event counts, uncertainty is especially important when the number of observed participants is limited. The registry record does not report a confidence interval, standard error, or other uncertainty estimate for the posted safety counts, so no numerical precision assessment can be quoted.
Over-dispersion is a general concern when data vary more than a simple model assumes. For example, participants may differ in exposure, susceptibility, or observation time, and events may cluster rather than occur independently. Such variation can make model-based uncertainty estimates too narrow if it is ignored. The registry record does not report a model for the adverse-event data, and the posted counts do not permit assessment of over-dispersion.
What do planning calculations mean?
General principle: sample-size calculations describe how much information a proposed study might need under stated assumptions. The planning illustration associated with this record is described as using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with an effect defined as a stated fraction of the observed effect. Those are illustration assumptions, not evidence that the trial used two arms or was planned with that design. The registered study is single-group, and its enrollment is 2. The protocol’s own sample-size justification is not reported in the registry record.
A planning calculation is not observed power. Observed power is not a substitute for an uncertainty interval around a result, and a retrospective calculation based on an observed effect can be unstable. Any sample-size values based on the illustration should therefore be understood as hypothetical planning quantities under its assumptions, not as properties of the completed study or as proof that the study could detect a particular effect. No planning result can remedy the absence of a comparator or the limited information in the posted safety counts.
What analyses are documented?
The registry record reports no statistical analyses. It does not state that hypothesis tests, adjusted models, subgroup analyses, or interim analyses were performed. The analysis population definition is available for safety, but other analysis-population details, missing-data rules, and analysis procedures are not reported. Accordingly, the interpretation should remain close to the observed counts and should not imply inferential findings that the record does not provide.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary safety endpoint and secondary outcomes concerning clinical worsening, 6-minute walk distance, change in World Health Organization functional class, and change in NT-pro BNP. When a study evaluates multiple outcomes, general statistical practice considers whether the chance of false-positive findings across tests needs to be controlled. The registry record does not report a multiplicity adjustment, a hierarchy among secondary outcomes, or a statistical testing plan. It also reports no analyses, so no multiplicity-adjusted or unadjusted test results can be interpreted.
Missing-data handling is not reported in the registry record. It does not describe how incomplete follow-up, absent endpoint assessments, or withdrawal would be handled. The safety analysis set includes participants who received at least one dose, but the record does not state how many enrolled participants received a dose or whether outcome data were available for every person in that set. The endpoint timeframe of up to 22 days does not provide individual follow-up detail.
The primary endpoint is described as a participant count, but no analysis population beyond the safety-set definition is given for the secondary outcomes. The record does not report whether those outcomes were analyzed for all enrolled participants, only treated participants, or another population. Numerical secondary-outcome results are not reported. These omissions limit assessment of selective availability, missingness, and the comparability of analysis populations. No assumptions about missing values or unreported analyses should be added to the posted counts.
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 |
|---|---|---|---|
| Sitaxentan Treatment | 0 | 2 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Sitaxentan Treatment | 1 of 2 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Sitaxentan Treatment |
|---|---|---|
| Diarrhoea | Gastrointestinal disorders | 1 of 2 |
| Headache | Nervous system disorders | 1 of 2 |
The safety summary lists 2 participants at risk for serious adverse events and 0 affected. For other adverse events, it lists 2 at risk and 1 affected. These are participant counts, not event episode totals. The registry describes the primary endpoint as covering any, severe, and serious adverse events, but it does not provide a separate numerical count for severe events.
Seriousness and severity are not interchangeable concepts. In general, seriousness is a regulatory classification based on consequences or criteria, while severity describes intensity. The registry’s reported serious-event category should therefore not be treated as a complete account of event intensity. No serious adverse event terms are listed. The numerical value for deaths is not reported in the registry record, so it should not be interpreted as a reported zero.
The counts do not identify the other adverse event or establish whether an event was related to sitaxentan. The record does not provide event timing, duration, treatment action, or participant-level details. With enrollment of 2 and a timeframe of up to 22 days, the figures describe only the recorded experience in this study and do not precisely characterize risk in a broader population.
12. What the Result Does, and Does Not, Mean
The results mean that the registry reports a small amount of observed safety information from a single-group study: 0 participants with serious adverse events and 1 participant with other adverse events, with 2 at risk for each category. The study enrolled 2 participants, and the stated primary safety timeframe was up to 22 days. These registry entries describe what the record reports; they do not establish a treatment effect.
The absence of a serious adverse event in the posted count is not proof that the intervention is free of serious risk. The limited enrollment and observation window mean the study contains little information about uncommon events or longer-term safety. The one participant listed with other adverse events cannot be characterized because the event term and its clinical details are not reported. Nor can the record establish whether the event was caused by treatment.
The study also cannot answer a comparative question. Its single-group, non-randomized design includes no control arm, so observed events cannot be compared under randomized treatment conditions. The record’s phase designation and the stated study intent do not change that limitation. Numerical results for the listed secondary outcomes are not reported, so no efficacy conclusion can be drawn from those outcomes.
The record does not explain the study’s terminated status, the reason for its enrollment, or how complete the follow-up was. It defines the safety population as participants receiving at least one dose, but does not state how many participants met that definition. In practical terms, these results are a descriptive safety snapshot, not a definitive assessment of benefit, harm, comparative performance, or population-level event frequency.
13. Why This Trial Matters Statistically
This trial illustrates why design and scale matter when interpreting clinical safety data. A participant count can accurately describe the recorded experience in a study group, yet remain too limited to characterize the range or frequency of events with precision. Here, enrollment was 2, and the registry reports a single treatment group with no randomized comparator. The findings are therefore descriptive rather than comparative.
The study also demonstrates the distinction between a stated endpoint and the results available for each part of that endpoint. The primary description includes any, severe, and serious adverse events, while the posted figures distinguish serious events from other adverse events. A separate severe-event count and event terms are not reported. Knowing which pieces of an endpoint are available is essential to avoiding a broader interpretation than the record supports.
Registry details also shape reproducibility. The safety-set definition and timeframe are stated, but participant-level exposure, follow-up completeness, missing-data methods, and the analysis plan are not reported. Without those details, readers cannot fully assess how the recorded counts were assembled or how sensitive they might be to incomplete observation.
Finally, planning assumptions should not be mistaken for the actual design. A planning illustration based on equal allocation between two arms does not describe this registered single-group study. Keeping planning calculations separate from observed results and trial design is a central part of sound statistical interpretation.
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 limitation is the very limited enrollment: the registry reports 2 participants. The single-group, non-randomized design offers no concurrent comparison and cannot separate treatment-associated events from background events or other influences. Open-label conduct also means masking was not used; the registry does not describe steps to address possible effects on event reporting or assessment.
The stated primary safety timeframe is up to 22 days, but participant-level exposure and follow-up are not reported. The record does not explain why the study was terminated, why enrollment was limited, or whether all enrolled participants received study drug. Although the safety analysis set is defined as participants receiving at least one dose, the number in that set is not separately stated.
Reporting is incomplete for interpreting safety in detail. The registry reports counts for serious and other adverse events, but no serious event terms, no separate severe-event count, and no numerical death count. It does not report event timing, duration, seriousness criteria, or relationship to treatment. Statistical analyses, uncertainty intervals, missing-data methods, and the protocol’s sample-size justification are also not reported in the registry record.
Numerical findings for the listed secondary outcomes are absent. As a result, the record does not support interpretation of clinical worsening, change in 6-minute walk distance, functional class, or NT-pro BNP. These limitations mean that the posted information should be treated as a narrow descriptive account rather than a complete evaluation of safety or efficacy.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Long-Term Open-Label, Safety Study Of Sitaxentan Sodium In Japanese Pulmonary Arterial Hypertension Patients — NCT01210443.
- Registry record last updated 2011-12-14; status last verified 2011-06.
- Results first posted 2011-12-14.
- 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
The registry describes a Phase 3, multi-center, open-label, non-randomized, single-group study of sitaxentan sodium in Japanese subjects with pulmonary arterial hypertension. It lists Pfizer as sponsor, enrollment of 2, and status as terminated. The recorded start is 2010-11 and primary completion is 2010-12.
The primary endpoint counts participants with adverse events, including severe and serious events, over a timeframe of up to 22 days. The safety group lists 2 at risk for serious adverse events, with 0 affected; for other adverse events, it lists 2 at risk and 1 affected. The record does not report statistical analyses or numerical results for the listed secondary outcomes. It also does not report the reason for termination, missing-data procedures, or the protocol’s sample-size justification. The findings are descriptive and do not provide a randomized comparison.