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 Chronic Hepatitis C Virus Related Thrombocytopenia to Evaluate the Effects of E5501 (NCT01355289), a randomized phase 2 study. The primary outcome is Number of Participants Who Achieved Platelet Response (Greater Than or Equal to 100 x 10^9/L) by Day 21 of Treatment Period A1 of Core Study.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01355289 |
| Phase | Phase 2 |
| Condition | Thrombocytopenia |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 65 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Eisai Inc. |
| Results posted | Yes |
2. Clinical Question
Population
Participants had chronic hepatitis C virus-related thrombocytopenia and were potential candidates for antiviral treatment. The primary endpoint population was the full analysis set, defined in the registry record as all randomized participants in the core study. The endpoint description specifies an average baseline platelet count greater than 20 x 10^9/L and less than or equal to 70 x 10^9/L.
Intervention
The core study included oral avatrombopag at 10 mg, 20 mg, or 30 mg once daily for up to 21 days. The descriptions say doses were preferably taken with food. Participants in the open-label extension started avatrombopag at 20 mg once daily, with dose titration within a minimum of 5 mg and a maximum of 50 mg for up to 48 weeks.
Comparator
The core study included a placebo group, with placebo given orally once daily for up to 21 days. The record identifies a randomized, placebo-controlled, parallel-group design. It does not report the allocation ratio or the sequence used to assign participants to the core-study groups.
Primary question
The primary endpoint asks how many participants achieved a platelet count greater than or equal to 100 x 10^9/L by Day 21 of treatment period A1. The record gives the responder definition but does not report the group-specific response counts, an estimated treatment contrast, or inferential results for that endpoint.
The clinical context in the record is thrombocytopenia related to chronic hepatitis C virus infection in people who might need antiviral treatment. The brief summary says the study aimed to evaluate avatrombopag by measuring platelet response in this population. That aim describes the question motivating the trial; it is not itself evidence of a treatment effect.
The listed interventions also include pegylated interferon, telaprevir, and ribavirin. The registry record does not specify how those antiviral drugs were used or assigned in relation to the core-study groups. It therefore does not establish an antiviral-treatment comparison or allow the platelet endpoint to be interpreted as a comparison of antiviral regimens.
In practical statistical terms, the central comparison is whether the proportion of randomized participants meeting the defined platelet-response threshold differs between the avatrombopag dose groups and placebo at the stated assessment. However, the registry record does not report the response data or the planned method for estimating that comparison. The endpoint definition and trial structure identify the intended question, while the posted information does not provide the result needed to answer it.
3. Trial Design
The registry describes a phase II, randomized, multicenter, placebo-controlled, double-blind, parallel-group core study with an open-label extension. The masking designation is triple. The record does not identify which parties were masked, how masking was maintained, or when masking was ended. Enrollment was 65, and the study status is completed. The recorded start is 2011-11 and primary completion is 2014-02.
Four core-study groups are described: placebo and avatrombopag at 10 mg, 20 mg, or 30 mg. The listed dosing period for these groups is up to 21 days, with once-daily oral administration. The endpoint timeframe is baseline to Day 21 of treatment period A1. The registry record does not report the allocation ratio, individual group assignment counts for the primary endpoint, or whether group assignment was stratified.
The open-label extension had a different treatment arrangement from the blinded core study. Its description starts avatrombopag at 20 mg once daily and allows titration based on an individual participant’s response, within a range from 5 mg to 50 mg, for up to 48 weeks. Because the extension is open label and includes dose titration, its safety data should not be treated as though they came from a concurrent randomized placebo comparison. The record does not report extension eligibility rules or the precise relationship between core-study participation and extension entry.
The listed primary analysis population is the full analysis set, defined as all randomized core-study participants. That description helps identify the intended population for the primary endpoint, but does not explain how the analysis treated participants with missing Day 21 measurements, early discontinuation, or protocol deviations. Those rules are not reported in the registry record.
Although the study title refers to efficacy, safety, and pharmacokinetics, the available endpoint description and adverse-event entries do not provide a complete account of every planned analysis. The statistical analysis plan, sample-size justification, interim analyses, and any adjustments for multiple comparisons are not reported in the registry record. Consequently, the design features can be described, but the detailed methods by which the sponsor intended to draw statistical conclusions cannot be reconstructed from these entries.
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 Screening Period encompassed 14 days ±7 days. Prerandomization assessments took place in all participants who had provided informed consent.
Core Study
| Stage | Placebo (Core Study) | Avatrombopag 10 mg (Core Study) | Avatrombopag 20 mg (Core Study) | Avatrombopag 30 mg (Core Study) | Avatrombopag (Open Label Extension) |
|---|---|---|---|---|---|
| STARTED | 17 | 16 | 18 | 14 | 0 |
| COMPLETED | 16 | 16 | 18 | 12 | 0 |
| NOT COMPLETED | 1 | 0 | 0 | 2 | 0 |
Reasons for not completing this period:
| Reason | Placebo (Core Study) | Avatrombopag 10 mg (Core Study) | Avatrombopag 20 mg (Core Study) | Avatrombopag 30 mg (Core Study) | Avatrombopag (Open Label Extension) |
|---|---|---|---|---|---|
| Adverse Event, Non-Fatal | 1 | 0 | 0 | 0 | 0 |
| Inadequate Therapeutic Effect | 0 | 0 | 0 | 1 | 0 |
| Other | 0 | 0 | 0 | 1 | 0 |
Open Label Extension
| Stage | Placebo (Core Study) | Avatrombopag 10 mg (Core Study) | Avatrombopag 20 mg (Core Study) | Avatrombopag 30 mg (Core Study) | Avatrombopag (Open Label Extension) |
|---|---|---|---|---|---|
| STARTED | 0 | 0 | 0 | 0 | 62 |
| COMPLETED | 0 | 0 | 0 | 0 | 28 |
| NOT COMPLETED | 0 | 0 | 0 | 0 | 34 |
Reasons for not completing this period:
| Reason | Placebo (Core Study) | Avatrombopag 10 mg (Core Study) | Avatrombopag 20 mg (Core Study) | Avatrombopag 30 mg (Core Study) | Avatrombopag (Open Label Extension) |
|---|---|---|---|---|---|
| Adverse Event, Non-Fatal | 0 | 0 | 0 | 0 | 1 |
| Lost to Follow-up | 0 | 0 | 0 | 0 | 1 |
| Inadequate Therapeutic Effect | 0 | 0 | 0 | 0 | 29 |
| Other | 0 | 0 | 0 | 0 | 3 |
Analysis population for the primary outcome, as defined in the registry: Full analysis set (FAS), the group of all randomized participants of core 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 | Placebo (Core Study) | Avatrombopag 10 mg (Core Study) | Avatrombopag 20 mg (Core Study) | Avatrombopag 30 mg (Core Study) | Total |
|---|---|---|---|---|---|---|
| Participants analysed | 17 | 16 | 18 | 14 | 65 | |
| Age, Continuous | Years | 50.2 (SD 7.96) | 55.3 (SD 8.06) | 54.9 (SD 7.38) | 53.6 (SD 7.26) | 53.5 (SD 7.78) |
| Sex: Female, Male: Female | Participants | 3 | 4 | 5 | 5 | 17 |
| Sex: Female, Male: Male | Participants | 14 | 12 | 13 | 9 | 48 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants Who Achieved Platelet Response (Greater Than or Equal to 100 x 10^9/L) by Day 21 of Treatment Period A1 of Core Study, measured over Baseline to Day 21.
| 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 who achieved platelet response by Day 21 of treatment period A1. A responder was defined as having a platelet count greater than or equal to 100 x 10^9/L by Day 21, starting from an average baseline platelet count greater than 20 x 10^9/L and less than or equal to 70 x 10^9/L. The record specifies the full analysis set as all randomized participants in the core study.
This is a binary endpoint at the participant level: each participant either meets the stated response definition or does not. Counting responders can make the result easier to interpret as a proportion of participants meeting a prespecified clinical measurement threshold. It also focuses the endpoint on crossing a defined platelet-count level during the short treatment period rather than on the full pattern of platelet measurements over time.
The registry lists secondary outcomes that include change in local platelet count by visit, participants achieving a count greater than 30 x 10^9/L through Day 21, and participants initiating antiviral treatment by Day 21. These outcomes address different aspects of platelet measurements and treatment progression; they are not substitutes for the specified primary endpoint.
The endpoint definition alone does not show how many participants responded in any group, how large any difference between groups was, or how uncertain an estimate might be. Those results are not reported in the registry record. Nor does the definition establish whether all randomized participants had usable Day 21 measurements or how missing endpoint data were handled.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes what the primary endpoint was intended to measure, but it does not report primary endpoint results. In particular, it gives no group-specific numbers of responders, no estimated comparison between an avatrombopag dose and placebo, and no confidence intervals or p-values for the endpoint. Without those results, the record cannot establish the direction, size, or precision of a primary-endpoint contrast.
This distinction is important: a trial’s objective and endpoint definition describe what investigators set out to assess, not what the assessment found. The study is marked completed, but completion status does not supply an outcome estimate. The enrollment figure of 65 describes the trial’s total enrollment; it cannot be used to infer how many participants met the response definition in each group.
For a binary endpoint, an estimate would ordinarily describe the response frequency in each group and a contrast between groups. A confidence interval expresses the uncertainty around an estimated quantity under the analysis assumptions. A narrow interval generally indicates greater precision than a wide interval, while a broad interval can remain compatible with a range of possible effects. These are general statistical explanations, not descriptions of results reported for this trial: no primary-endpoint interval or contrast is reported in the registry record.
The safety entries are separate from the primary efficacy endpoint. In the core-study groups, the registry reports serious adverse events affecting 0 of 17 participants in the placebo group, 1 of 16 in the 10 mg group, 0 of 18 in the 20 mg group, and 1 of 14 in the 30 mg group. For the open-label extension, it reports serious adverse events affecting 13 of 64 participants. These are descriptive counts from groups with different treatment and follow-up contexts; they do not replace the missing primary response comparison.
For other adverse events, the record reports 6 of 17 participants in the placebo group, 11 of 16 in the 10 mg group, 12 of 18 in the 20 mg group, and 11 of 14 in the 30 mg group, with 55 of 64 in the open-label extension. These counts should be interpreted in light of the group sizes and the distinct extension design. They do not on their own identify event severity, duration, causality, or comparative risk.
Overall, the statistical interpretation is constrained by missing outcome estimates and analysis details. The registry record does not report the planned model or test, the confidence level used for any interval, the handling of missing data, or multiplicity procedures. No claim about the size or statistical significance of the primary treatment comparison can be drawn from the available entries.
9. Statistical Methods Explained
What does a binary endpoint mean?
A binary endpoint places each participant into one of two outcome categories. For this study, the registry’s responder definition classifies a participant according to whether the platelet-count threshold was reached by Day 21, given the stated baseline range. A group result for such an endpoint can be expressed as a count of responders and a proportion of participants assessed. A comparison can then quantify how those response frequencies differ between randomized groups.
Those are general descriptions of common approaches, not a statement that a particular statistical test or estimator was used in this trial. The registry record identifies the endpoint as a count of participants but does not report the primary response counts, the group-specific denominators used in the endpoint analysis, or the method used to compare groups. A count alone is not enough to determine a response proportion or a treatment contrast.
How should uncertainty be understood?
General statistical interpretation relies on estimates as well as uncertainty. A point estimate gives a single summary of the observed comparison, while a confidence interval describes a range of values reasonably compatible with the data and the method’s assumptions. A p-value, when used, assesses how surprising data at least as extreme as those observed would be under a specified null hypothesis. Neither a confidence interval nor a p-value conveys the full clinical importance of an effect, and neither can be interpreted when its estimate and assumptions are unavailable.
No confidence interval, p-value, or treatment-effect estimate for the primary endpoint is reported in the registry record. The record also does not report whether the sponsor used a superiority test, an adjusted analysis, or another inferential procedure. It would be inappropriate to infer a statistical method from the study’s randomized design alone.
Why does the randomized design matter?
In general, random assignment aims to make treatment groups comparable with respect to measured and unmeasured characteristics at the time of allocation, apart from chance variation. A placebo group provides a concurrent comparator for the core study. These design features can support causal interpretation when the analysis follows the design and when outcome ascertainment, follow-up, and missing-data handling are adequately addressed. They do not remove uncertainty or guarantee that groups are balanced in a modest-sized study.
The registry record identifies randomized allocation and a parallel-group model, but does not give the allocation ratio, sequence-generation method, concealment details, or group-specific primary endpoint results. It also labels masking as triple without identifying who was masked. These missing details limit assessment of how allocation and masking were implemented.
What is the role of the analysis population?
The full analysis set is described as all randomized participants of the core study. In general, including randomized participants in their assigned groups helps preserve the advantages of randomization. However, the label alone does not specify how participants without a Day 21 measurement were handled, whether participants were analyzed according to assigned treatment, or how deviations from the protocol were addressed.
The registry record does not report the missing-data method or a sensitivity analysis. This matters because results can depend on whether missing measurements are excluded, imputed, or handled under another prespecified rule. Such methods rely on assumptions about the relationship between missingness and participants’ outcomes. No missingness pattern or assumption is reported for this endpoint.
How should multiple outcomes and groups be considered?
The core study includes several avatrombopag dose groups and a placebo group. The record also lists secondary outcomes. In general, examining multiple groups, outcomes, or assessment times can create multiple opportunities to find an apparently notable result by chance. Statistical plans may address this by specifying a primary comparison, ordering tests, or adjusting inference. The registry record does not report a multiplicity strategy, the primary comparison for statistical testing, or whether any adjustment was made.
There are also secondary platelet outcomes measured by visit, which may involve repeated measurements from the same participant. In general, measurements from one person across visits are correlated rather than independent. A suitable longitudinal analysis can account for that dependence; treating all measurements as unrelated observations can understate uncertainty. The registry record does not report the analysis method for those repeated measurements, so no specific model can be attributed to the study.
What can be learned from the safety counts?
Safety entries report the number of participants affected and the number at risk in each group for serious and other adverse events. These are descriptive summaries. In general, event counts can be compared only with attention to group size, exposure duration, event definitions, and completeness of reporting. The open-label extension differs from the randomized core study in treatment assignment and duration, so its counts are not a randomized placebo comparison. The registry record does not provide event-level exposure times or enough detail to reconstruct an adjusted safety analysis.
The record lists selected serious adverse event terms with percentages, including paraesthesia, thrombocytopenia, anaemia, neutropenia, leukopenia, and pancytopenia. It does not specify the denominator or provide a complete arm-specific breakdown for those terms in the entries available. Those percentages therefore should not be recast as comparative risks for particular treatment groups.
Finally, the registry does not report a sample-size justification, interim-analysis plan, statistical analysis plan, or a model for the primary endpoint. General statistical concepts can clarify what such methods would do, but they cannot fill in methods absent from the registry record. Any recalculated or illustrative estimates would require the outcome data and assumptions needed to calculate them; those primary endpoint inputs are not reported.
10. Multiplicity, Missing Data and Analysis Populations
The registry identifies a primary endpoint and lists several secondary outcomes, but does not report how multiplicity was handled. Multiplicity arises when multiple treatment comparisons, endpoints, or time points are examined. In general, the more opportunities there are for statistical testing, the greater the chance that at least one result may appear notable by chance alone. A prespecified testing order or adjustment can help control that issue, but no such procedure is reported in the registry record.
The primary endpoint is defined for Day 21, while a secondary outcome concerns platelet-count change by visit during treatment period A1. The record does not state which dose-versus-placebo comparisons were designated as confirmatory, whether all dose groups were compared with placebo, or how inference across the secondary outcomes was planned. It also does not report interim analyses. No assumptions about those procedures can be made from the trial title or design description.
Missing-data handling is also not reported. The record defines the full analysis set as all randomized core-study participants, but gives no rule for participants without a Day 21 platelet count, participants who discontinued early, or measurements that were unavailable for other reasons. It does not describe imputation, exclusion, sensitivity analyses, or assumptions about why measurements might be missing.
These omissions matter because an endpoint’s interpretation depends not only on its definition but also on which observations contribute to the analysis and how uncertainty is calculated. The registry’s population label is useful, but it does not provide enough detail to assess whether all randomized participants contributed to the primary analysis or how missing outcomes affected it. The statistical analysis plan and sample-size justification are not reported in the registry record.
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 |
|---|---|---|---|
| Placebo (Core Study) | 0 | 17 | 0.0% |
| Avatrombopag 10 mg (Core Study) | 1 | 16 | 6.2% |
| Avatrombopag 20 mg (Core Study) | 0 | 18 | 0.0% |
| Avatrombopag 30 mg (Core Study) | 1 | 14 | 7.1% |
| Avatrombopag (Open Label Extension) | 13 | 64 | 20.3% |
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 |
|---|---|
| Placebo (Core Study) | 6 of 17 |
| Avatrombopag 10 mg (Core Study) | 11 of 16 |
| Avatrombopag 20 mg (Core Study) | 12 of 18 |
| Avatrombopag 30 mg (Core Study) | 11 of 14 |
| Avatrombopag (Open Label Extension) | 55 of 64 |
Most frequent serious adverse event terms
| Event term | Organ system | Placebo (Core Study) | Avatrombopag 10 mg (Core Study) | Avatrombopag 20 mg (Core Study) | Avatrombopag 30 mg (Core Study) | Avatrombopag (Open Label Extension) |
|---|---|---|---|---|---|---|
| Thrombocytopenia | Blood and lymphatic system disorders | 0 of 17 | 1 of 16 | 0 of 18 | 0 of 14 | 2 of 64 |
| Anaemia | Blood and lymphatic system disorders | 0 of 17 | 0 of 16 | 0 of 18 | 0 of 14 | 2 of 64 |
| Neutropenia | Blood and lymphatic system disorders | 0 of 17 | 0 of 16 | 0 of 18 | 0 of 14 | 2 of 64 |
| Paraesthesia | Nervous system disorders | 0 of 17 | 0 of 16 | 0 of 18 | 1 of 14 | 1 of 64 |
| Leukopenia | Blood and lymphatic system disorders | 0 of 17 | 0 of 16 | 0 of 18 | 0 of 14 | 1 of 64 |
| Pancytopenia | Blood and lymphatic system disorders | 0 of 17 | 0 of 16 | 0 of 18 | 0 of 14 | 1 of 64 |
| Abdominal pain | Gastrointestinal disorders | 0 of 17 | 0 of 16 | 0 of 18 | 0 of 14 | 1 of 64 |
| Hepatic mass | Hepatobiliary disorders | 0 of 17 | 0 of 16 | 0 of 18 | 0 of 14 | 1 of 64 |
| Gastroenteritis | Infections and infestations | 0 of 17 | 0 of 16 | 0 of 18 | 0 of 14 | 1 of 64 |
| Urinary tract infection | Infections and infestations | 0 of 17 | 0 of 16 | 0 of 18 | 0 of 14 | 1 of 64 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Placebo (Core Study) | Avatrombopag 10 mg (Core Study) | Avatrombopag 20 mg (Core Study) | Avatrombopag 30 mg (Core Study) | Avatrombopag (Open Label Extension) |
|---|---|---|---|---|---|---|
| Nausea | Gastrointestinal disorders | 0 of 17 | 3 of 16 | 4 of 18 | 2 of 14 | 20 of 64 |
| Neutropenia | Blood and lymphatic system disorders | 0 of 17 | 2 of 16 | 4 of 18 | 2 of 14 | 20 of 64 |
| Anaemia | Blood and lymphatic system disorders | 0 of 17 | 2 of 16 | 2 of 18 | 1 of 14 | 21 of 64 |
| Fatigue | General disorders | 0 of 17 | 1 of 16 | 3 of 18 | 2 of 14 | 16 of 64 |
| Chills | General disorders | 1 of 17 | 3 of 16 | 3 of 18 | 1 of 14 | 13 of 64 |
| Influenza like illness | General disorders | 2 of 17 | 1 of 16 | 4 of 18 | 3 of 14 | 11 of 64 |
| Pruritus | Skin and subcutaneous tissue disorders | 0 of 17 | 4 of 16 | 0 of 18 | 2 of 14 | 15 of 64 |
| Leukopenia | Blood and lymphatic system disorders | 0 of 17 | 1 of 16 | 3 of 18 | 1 of 14 | 14 of 64 |
| Headache | Nervous system disorders | 1 of 17 | 0 of 16 | 3 of 18 | 2 of 14 | 12 of 64 |
| Insomnia | Psychiatric disorders | 1 of 17 | 1 of 16 | 0 of 18 | 3 of 14 | 13 of 64 |
Serious events with the highest arm-level rate: paraesthesia (7.1%), thrombocytopenia (6.2%), anaemia (3.1%), neutropenia (3.1%), leukopenia (1.6%).
The serious adverse event figures are participant counts within the stated groups. In the core study, the registry reports 0 of 17 participants for placebo, 1 of 16 for avatrombopag 10 mg, 0 of 18 for avatrombopag 20 mg, and 1 of 14 for avatrombopag 30 mg. In the open-label extension, it reports 13 of 64 participants. These entries describe participants affected, not the total number of separate events.
The other adverse event figures are 6 of 17 for placebo, 11 of 16 for avatrombopag 10 mg, 12 of 18 for avatrombopag 20 mg, and 11 of 14 for avatrombopag 30 mg. The open-label extension entry is 55 of 64. The extension was open label, allowed dose titration, and lasted up to 48 weeks, whereas the core-study dosing descriptions are for up to 21 days. Its counts should not be read as a randomized comparison with placebo.
The registry lists selected serious adverse event terms with percentages: paraesthesia, 7.1%; thrombocytopenia, 6.2%; anaemia, 3.1%; neutropenia, 3.1%; leukopenia, 1.6%; and pancytopenia, 1.6%. The entries do not give an arm-specific breakdown or denominator for these terms. Death counts are not reported in the registry record.
These data do not establish whether an event was caused by study treatment. They also do not provide event timing, duration, recurrence, or exposure-adjusted rates. The figures are descriptive safety information and should be interpreted separately from the unreported primary platelet-response comparison.
12. What the Result Does, and Does Not, Mean
The registry record establishes that the trial was designed to evaluate platelet response with avatrombopag in chronic hepatitis C virus-related thrombocytopenia, using a placebo-controlled randomized core study and an open-label extension. It gives a clear primary responder definition and reports some safety counts. Those details describe the research question and parts of the observed safety record.
However, the primary endpoint results are not reported in the registry record. No group-specific responder counts, treatment contrast, confidence interval, or p-value is available in the entries described. As a result, the record does not show whether response frequencies differed among the core-study groups or how precisely any difference was estimated. It also does not establish that the treatment did or did not achieve the endpoint.
The safety counts have a narrower interpretation. They report participants affected by serious and other adverse events within each listed group. Because the extension differs from the blinded randomized core study, its numbers cannot be treated as a direct placebo comparison. The selected serious event percentages are not accompanied by the denominators or treatment-group breakdown needed to interpret them as comparative rates.
More broadly, statistical evidence is not determined by a study’s phase, enrollment, or completion status alone. Interpretation requires outcome estimates, uncertainty measures, and the analysis methods used to obtain them. The registry record does not report the statistical analysis plan, missing-data rules, multiplicity procedures, or sample-size justification. These absent details further limit evaluation of how the investigators planned to draw conclusions.
Accordingly, the defensible reading is descriptive: a randomized phase II trial with a defined Day 21 platelet-response endpoint is registered as completed, but the primary response findings are not reported in the registry record. The safety entries provide counts within the listed groups, subject to the limitations of incomplete comparative detail. No treatment recommendation or conclusion about efficacy follows from these registry entries alone.
13. Why This Trial Matters Statistically
This study illustrates the difference between a well-defined endpoint and a reported result. The registry specifies a participant-level response threshold, a time point, a baseline platelet-count range, and an analysis population. These details make the intended outcome understandable. Yet without group-specific response data and an estimate of the comparison, readers cannot assess the size or precision of the primary result.
The design also makes clear why interpretation depends on more than the endpoint label. A randomized placebo-controlled core study can support a comparative analysis, while masking can reduce some risks of biased care or assessment. But the registry does not explain allocation procedures or who was masked, and it does not report the methods used to analyze the endpoint. Design labels are informative, but they are not a substitute for an analysis record.
There are multiple dose groups and listed secondary outcomes, which raises general questions about how treatment contrasts and statistical testing were prioritized. Without the multiplicity strategy, readers cannot tell how the investigators planned to interpret results across those comparisons. Similarly, the full analysis set definition names a population but does not resolve how missing Day 21 measurements were handled.
The safety entries provide another statistical lesson: counts from a short randomized core study and a longer open-label extension should not automatically be combined into a single comparative interpretation. The extension permits titration and lacks a concurrent placebo group as described. Its participant counts therefore answer a different descriptive question from the randomized core-study counts.
For clinical researchers and biostatisticians, this record demonstrates the value of complete reporting: endpoint results, uncertainty intervals, analysis populations, missing-data rules, multiplicity handling, and safety denominators all contribute to a transparent interpretation. When those elements are absent, the appropriate conclusion is limited to what the registry actually records, rather than filling gaps with assumptions.
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 primary limitation is that the primary endpoint results are not reported in the registry record. Although the responder definition and analysis population are specified, there are no arm-specific response counts or estimated comparisons. That prevents assessment of the primary outcome’s direction, size, and precision.
The statistical methods are also incompletely described. The registry does not report the analysis model or test, confidence-interval method, missing-data procedure, multiplicity strategy, interim analyses, or sample-size justification. It is therefore not possible to determine from the record how the primary endpoint was analyzed or how the investigators planned to account for multiple dose groups and secondary outcomes.
Some design details are absent as well. The allocation ratio and sequence-generation procedures are not reported, and the registry does not identify which parties were included in the triple-masking designation. It also does not describe the handling of protocol deviations or the relationship between core-study participation and extension enrollment.
The safety summaries are limited to participant counts and selected event terms. The record does not report deaths, event-level exposure times, timing or duration of events, or a complete arm-specific distribution for the selected serious adverse event terms. Those gaps limit comparative safety interpretation. The open-label extension is also structurally different from the randomized core study: treatment was not described as placebo controlled there, dose titration was permitted, and treatment could continue for up to 48 weeks.
Finally, the registry lists antiviral agents but does not explain their use or assignment. The entries therefore do not support conclusions about antiviral treatment or its interaction with the platelet-response endpoint. These limitations reflect what is not reported in the registry record, rather than evidence that a particular procedure or result was absent from the study itself.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Chronic Hepatitis C Virus Related Thrombocytopenia to Evaluate the Effects of E5501 — NCT01355289.
- Registry record last updated 2018-02-22; status last verified 2018-01.
- Results first posted 2018-02-22.
- 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
NCT01355289 is a completed phase II randomized, multicenter, placebo-controlled, parallel-group study with triple masking and an open-label extension. Enrollment was 65. The recorded start is 2011-11, and primary completion is 2014-02. The core study included placebo and avatrombopag at 10 mg, 20 mg, or 30 mg once daily for up to 21 days.
The primary endpoint was the number of participants with a platelet count greater than or equal to 100 x 10^9/L by Day 21, among participants whose average baseline platelet count was greater than 20 x 10^9/L and less than or equal to 70 x 10^9/L. The full analysis set is described as all randomized core-study participants. Primary endpoint results and detailed statistical methods are not reported in the registry record.
The extension used open-label avatrombopag with dose titration and treatment for up to 48 weeks. The registry reports serious and other adverse-event participant counts for the core groups and extension, but these entries do not provide a complete comparative safety analysis. Death counts are not reported in the registry record.