A Study To Monitor Long-Term Treatment With PF-00547659: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study To Monitor Long-Term Treatment With PF-00547659 (NCT01298492), a na phase 2 study. The primary outcome is Number of Participants With On-Treatment Adverse Events (AEs), AEs Led to Withdrawal, and Serious Adverse Events (SAEs).

2. Clinical Question

The study's stated purpose was to provide open-label treatment to eligible patients who had completed a prior PF-00547659 study. The registry identifies the prior study as A7281006 and says participants were to be stratified according to responder status based on change in CDAI in that study, without unblinding treatment assignment from A7281006. The full details after this description are not reported in the registry record.

The primary question is descriptive: what safety events were recorded among people treated in this extension? Because the design has one treatment group and no concurrent control, the observed event counts do not establish how those counts would compare under another treatment or without study treatment. The registry record also does not report an efficacy question as the primary objective; its brief summary identifies long-term safety as the primary endpoint.

3. Trial Design

This was a Phase 2, multicenter, open-label extension study of PF-00547659 in participants with Crohn's disease. The official title identifies it as OPERA II and describes its purpose as assessing long-term safety. The study is listed as completed, with a single-group model and allocation recorded as NA. The registry reports enrollment of 268 participants.

Participants were eligible after completing a prior study of PF-00547659. The arm description refers to completion of the 12 week double blind induction period in study A7281006 and stratification by responder or non-responder status based on change in CDAI in that study. It also states that treatment assignment from A7281006 was not to be unblinded. The rest of the arm description is incomplete in the registry record, so additional eligibility or treatment details are not reported in the registry record.

The listed intervention is PF-00547659, with a treatment group titled PF-00547659 75 mg. Treatment was open label, so the registry does not describe masking in this extension. No separate control or comparison arm is recorded. As a result, safety findings are observations within the treated group, not estimates from a randomized comparison.

The study start is recorded as 2011-07-01, and primary completion as 2016-07-27. The primary safety timeframe runs from the start of study treatment up to Week 72. Those dates describe the study record; they do not establish that every participant had the same duration of exposure or follow-up. Participant-level follow-up and treatment duration distributions are not reported in the registry record.

The registry identifies 268 participants at risk for both serious and other adverse events. It defines the primary safety population as the modified intent-to-treat population: all enrolled participants who received at least 1 dose of investigational product. Details about exclusions from other analysis populations, adherence, treatment discontinuation, or procedures for handling incomplete follow-up are not reported in the registry record.

4. Participant Flow and Accounting

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

Before assignment: A total of 268 participants (225 participants from Feeder Study A7281006 \[NCT01276509\] and 43 participants from Feeder Study A7281008 \[NCT01387594\]) were enrolled and overall 149 participants completed the study.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The modified intent-to-treat (mITT) population included all enrolled participants who received at least 1 dose of investigational product.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: The modified intent-to-treat (mITT) population included all enrolled participants who received at least 1 dose of investigational product.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With On-Treatment Adverse Events (AEs), AEs Led to Withdrawal, and Serious Adverse Events (SAEs), measured over From start of study treatment up to Week 72 (Treatment Period).

The primary endpoint is the number of participants with on-treatment adverse events, adverse events leading to withdrawal, and serious adverse events. The specified timeframe is from the start of study treatment up to Week 72. The registry describes adverse events broadly: these included adverse drug reactions, illnesses with onset during the study, worsening of previous illnesses, clinically significant changes in physical examination findings, and abnormal objective test findings such as ECG or laboratory findings.

The registry defines a serious adverse event as an adverse event at any dose that resulted in death; was life threatening, meaning immediate risk of death; required in-subject hospitalization or prolonged an existing hospitalization; resulted in persistent or significant disability or incapacity; or resulted in a congenital anomaly or birth defect. These criteria distinguish serious events by their consequences, not simply by how frequently an event occurs.

A participant count is useful for describing how many people experienced an event during the stated period. It is not the same as a count of every event episode: a participant may experience more than one event, while the endpoint is framed around participants. Counts also depend on the number of people observed and the completeness of event collection. The registry does not report a rate adjusted for time at risk.

The posted results include counts for participants with serious and other adverse events, but do not give a withdrawal count for the endpoint. Consequently, the full endpoint cannot be reconstructed from the reported counts. The use of safety events as the primary endpoint matches the stated long-term safety purpose; it does not, by itself, provide a comparison with an untreated or alternative-treatment group.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count represent?

A binary safety outcome classifies each participant according to whether the specified event occurred during the defined observation period. The summary can then report the number of participants who met that definition. This differs from counting every event episode: repeated events in one participant may still contribute one person to a participant-based count. The primary endpoint title is explicitly framed around participants, and the registry identifies the outcome type as participants with an event.

Counts need a population denominator to be interpreted in context. The registry lists 268 participants at risk for serious and other adverse events and reports 118 affected by serious adverse events and 206 affected by other adverse events. No new proportions are calculated. A proportion would require dividing an event count by a clearly defined denominator, and an estimate of risk over time would also require clarity about follow-up. The registry does not report a time-adjusted rate.

Why do definitions and observation windows matter?

An adverse event definition determines which experiences enter a safety summary. This record includes illnesses beginning during the study, worsening of previous illnesses, adverse drug reactions, clinically significant physical examination changes, and abnormal objective findings such as ECG or laboratory findings. A serious event is defined by specified consequences, including death, life-threatening status, hospitalization, significant disability or incapacity, or congenital anomaly or birth defect. Applying these definitions consistently is important because counts depend on what is classified and how events are collected.

The stated period runs from treatment start up to Week 72. An observation window specifies when events are eligible for inclusion; it is not evidence that every participant was observed for an identical duration. The registry does not report participant-level follow-up lengths, time at risk, or the timing of individual events. Without those details, comparisons of event frequency over exposure time cannot be made from this record.

What can a confidence interval add?

In general, a confidence interval describes the uncertainty associated with an estimate under a statistical model. For a participant-level event proportion, it can indicate a range of values compatible with the observed data and the chosen method. A narrow interval indicates greater precision than a wide interval, while neither interval establishes causation. This registry record reports no confidence intervals, so the precision of the event counts as estimates of a broader population is not quantified.

Inferential tests and p-values address questions defined by a statistical model, commonly whether data are compatible with a specified null hypothesis. They do not make a single-group study into a randomized comparison, and they cannot remove unmeasured differences or other sources of bias. No inferential analyses are listed in the registry record. The absence of recorded analyses means no p-value or model-based comparison should be inferred from the descriptive counts.

Why does the single-group design constrain inference?

Random allocation to concurrent groups can, under appropriate conditions, help balance measured and unmeasured characteristics between groups. This study is recorded as single group, with allocation listed as NA; it therefore has no randomized comparison within the extension. A historical or external comparison would require additional design and analysis choices, and none is reported in the registry record. The counts describe the treated group but cannot identify how many events would have occurred in the absence of the study treatment.

Open-label treatment means treatment was not masked in the extension as described in the record. In general, knowledge of treatment can influence event reporting, clinical assessment, or decisions to stop treatment. The extent of any such influence cannot be determined from the registry entry. The description that treatment assignment from A7281006 was not unblinded refers to that prior study and does not establish masking procedures in this extension.

What do the planning assumptions mean?

The registry describes planning illustrations based on a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. For time-to-event illustrations it specifies total events, and for other illustrations it specifies participants per arm. These are assumptions for hypothetical planning calculations, not features of the single-group allocation recorded for this study. The registry does not report a trial-specific sample-size justification, and no numerical planning results or observed-power estimate are reported in the registry record.

In general, a sample-size calculation estimates the amount of information a future design might need under stated assumptions. Its output depends on the target effect, variability, error rate, allocation, and analysis method. A planning illustration based on an observed effect is not evidence that a study had a particular probability of detecting an effect after it was completed. Here, no numerical planning output is recorded, and the assumptions involving two arms do not turn this extension into a two-arm trial.

How should repeated or clustered event data be handled?

Some safety datasets contain repeated episodes per participant or clustering by site. General count models may need to account for such dependence; over-dispersion matters when event-count variability exceeds what a simpler model assumes, because standard errors can otherwise be too small. Those concepts are most relevant to event episode counts or clustered observations. The endpoint recorded is a count of participants with an event, and the registry does not report event-level data, site-level analyses, a repeated-event model, or an over-dispersion assessment. No such analysis can be attributed to this study from the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry records three outcome measures: the primary safety endpoint and two secondary outcomes, positive anti-drug antibodies and serum trough concentrations versus time. It does not report results for the secondary outcomes. Nor does it report a statistical analysis plan describing how multiple outcomes were prioritized or whether any adjustment for multiple testing was planned or applied. A multiplicity procedure is therefore not reported in the registry record.

Multiplicity arises when several outcomes or comparisons are tested: the chance of at least one apparently notable finding can increase if each is assessed separately. In general, prespecifying a primary outcome and setting an analysis strategy can help readers interpret a collection of results. The record identifies a primary endpoint, but the handling of multiple outcomes beyond that designation is not reported in the registry record. No claims about adjusted significance should be inferred.

The defined population is the modified intent-to-treat population, consisting of all enrolled participants who received at least 1 dose of investigational product. The adverse event summaries list 268 participants at risk. Details about how incomplete safety follow-up, missing outcome information, or participants who did not complete treatment were handled are not reported in the registry record. The reasons for missing observations and their potential effect on the results cannot be assessed.

In general, missing data can affect safety summaries if participants with incomplete follow-up have different event experience from those observed for the full period. A complete-case summary can also represent a selected subset if missingness is related to health status or treatment discontinuation. No imputation method, sensitivity analysis, or missing-data assumption is reported in the registry record. The number of participants lost to follow-up or with incomplete endpoint data is also not reported.

The record lists no analyses. Consequently, it does not describe adjusted models, subgroup analyses, interim analyses, or a strategy for repeated measurements. These procedures should not be assumed from the endpoint descriptions alone.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: crohn's disease (16.4%), anal abscess (3.7%), anal fistula (2.6%), ileus (1.5%), small intestinal obstruction (1.5%).

The registry lists 118 participants with serious adverse events among 268 at risk, and 206 participants with other adverse events among 268 at risk. The listed serious-event terms are Crohn's disease at 16.4%, anal abscess at 3.7%, anal fistula at 2.6%, ileus at 1.5%, small intestinal obstruction at 1.5%, and pneumonia at 1.5%. These percentages are reported as event-term summaries; the record does not state their denominator or whether participants could contribute to more than one term.

The record separately lists 2 deaths. It does not report their causes, timing, relationship to treatment, or relationship to the listed event terms. The presence of a serious event during treatment does not by itself establish that the treatment caused it. Crohn's disease is also among the listed serious-event terms, and the registry does not provide case-level detail to distinguish underlying disease activity from other explanations.

The primary endpoint includes adverse events leading to withdrawal, but a withdrawal count is not reported in the registry record. These summaries are descriptive counts for one open-label group; there is no concurrent control group for comparison. They should not be read as comparative risks or as evidence about what would have happened under another treatment.

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

The results describe safety events recorded among participants enrolled in a single-group, open-label extension study of PF-00547659. The registry reports 118 participants affected by serious adverse events and 206 affected by other adverse events, with 268 participants at risk for each summary. It also lists 2 deaths and several serious-event terms with percentages. These observations provide a description of what was recorded in the study population during the specified treatment period.

The figures do not establish that PF-00547659 caused any particular event. A safety event occurring during treatment may have multiple possible explanations, including the underlying illness, other health circumstances, or treatment. The registry does not provide case-level details, event timing, or attribution that would resolve those explanations. Likewise, the record does not offer a concurrent comparison group, so it cannot quantify how the observed event burden differs from another treatment or from no study treatment.

The posted counts do not fully represent every component of the named primary endpoint because the number of adverse events leading to withdrawal is not reported. No confidence intervals, inferential results, or time-adjusted event rates are reported, so the statistical precision of the counts is not available. The denominator for the serious-event term percentages is also not reported in the registry record.

The study was designed as an extension for eligible participants who had completed a prior PF-00547659 study. That context is important: participants entering an extension are selected through prior study participation and eligibility, and the registry record does not describe people who did not enter. Accordingly, the safety summaries should not automatically be generalized to all people with Crohn's disease or to other treatment settings.

The results are best interpreted as a record of observed safety events in the enrolled treatment group, using the registry's definitions and timeframe. They do not establish comparative safety, treatment efficacy, or causal attribution. Results for the listed secondary outcomes are not reported in the registry record.

13. Why This Trial Matters Statistically

Long-term safety questions often require careful description of who was observed, what counted as an event, and how long events were collected. This record makes the primary safety objective explicit and defines both adverse events and serious adverse events. It also names a treatment period extending up to Week 72. Those details help readers understand the intended scope of the safety summaries rather than treating all adverse events as interchangeable.

The study also illustrates why design determines the questions that can be answered. A single-group extension can document event experience among participants who received treatment, but it cannot provide a randomized treatment contrast. This is especially relevant in a condition where the disease itself may be part of the serious-event profile; Crohn's disease is listed among the serious-event terms. Without a comparator and case-level attribution, observed events remain descriptive.

Statistically, a count is only one part of an interpretable safety result. The population at risk, event definition, observation period, missing follow-up, and uncertainty all matter. The registry records the modified intent-to-treat population and the at-risk counts, but does not report confidence intervals, time-adjusted rates, or missing-data methods. Identifying these omissions helps readers distinguish available evidence from questions the record cannot answer.

The extension context is also relevant for interpretation. Participants had completed a prior study before entering, and the registry describes stratification based on prior response status. Selection into an extension can limit how broadly its observations apply. A statistically careful reading therefore considers both the strengths of a defined safety objective and the limitations imposed by single-group follow-up and incomplete reporting.

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 central design limitation is the absence of a concurrent comparator. Allocation is listed as NA and the model is single group, so the event counts cannot support a like-for-like comparison with another treatment. Open-label observation also leaves the possibility that knowledge of treatment could affect event recognition or reporting; the magnitude of any such influence is not reported in the registry record.

The participant population is selected: eligible participants had completed a prior PF-00547659 study before entering the extension. The registry does not describe the characteristics of people who did not enroll, nor does it provide enough detail to assess how selection into the extension affects generalizability. The arm description is incomplete after its statement about additional participants, and those additional eligibility details are not reported in the registry record.

The primary endpoint includes adverse events leading to withdrawal, but a corresponding result is not reported. The listed serious-event percentages have no stated denominator in the registry record, and the summaries do not describe whether participants could contribute to multiple event terms. The two deaths are not described by cause, timing, or treatment attribution. These gaps limit interpretation of the adverse-event profile.

Follow-up completeness and exposure time are also unclear. The registry specifies a timeframe up to Week 72, but does not report participant-level duration, event timing, losses to follow-up, missing outcome data, or methods for handling incomplete records. No confidence intervals, inferential analyses, subgroup results, or statistical analysis plan are reported. Results for the two secondary outcomes are not reported in the registry record.

Finally, the record's planning assumptions describe hypothetical two-arm sample-size illustrations, while the extension itself is single group. No trial-specific sample-size justification or numerical planning output is reported. The recorded enrollment should not be treated as evidence of a particular precision or statistical power.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study To Monitor Long-Term Treatment With PF-00547659 — NCT01298492.
• Registry record last updated 2021-06-03; status last verified 2021-05.
• Results first posted 2017-08-31.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT01298492 is a completed Phase 2, multicenter, open-label, single-group extension study of PF-00547659 in Crohn's disease. The official title identifies it as OPERA II. The registry reports 268 enrolled participants and lists the treatment group as PF-00547659 75 mg. Participants were eligible after completing a prior study of PF-00547659.

The primary endpoint is the number of participants with on-treatment adverse events, adverse events leading to withdrawal, and serious adverse events, from treatment start up to Week 72. The record lists 118 participants with serious adverse events, 206 with other adverse events, and 2 deaths. It does not report the withdrawal count, inferential analyses, confidence intervals, or results for the two secondary outcomes.

Because the study has no concurrent comparator, the safety results are descriptive observations within the enrolled group. The registry does not report enough information to establish event attribution, quantify statistical precision, or compare these findings with another treatment.