A Study To Evaluate The Mechanism Of Action Of CP-690,550 In Patients With Rheumatoid Arthritis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study To Evaluate The Mechanism Of Action Of CP-690,550 In Patients With Rheumatoid Arthritis (NCT00976599), a randomized phase 2 study. The primary outcome is Change From Baseline in Synovial Tissue Messenger Ribonucleic Acid (mRNA) Expression at Day 28.

2. Clinical Question

This was an exploratory study of pharmacodynamic effects: it sought to examine whether the treatment groups differed in biological measurements in synovial tissue. The study also states that it evaluated safety, tolerability, and efficacy. Those aims should not be conflated with a demonstrated clinical benefit. The primary endpoint is a tissue-level measure, while listed secondary outcomes include clinical response definitions and disease-activity scores. The registry record gives the outcome names, but does not provide numerical results for the primary endpoint or the listed secondary outcomes.

3. Trial Design

The study is identified as a randomized, double-blind, placebo-controlled, multicenter phase 2a trial with a parallel-group design. It enrolled 29 participants and is recorded as completed. The study began in 2009-11, and primary completion is recorded as 2011-07. The official title describes four weeks of oral CP-690,550 given twice daily. The two interventions were CP-690,550 plus methotrexate and placebo plus methotrexate.

Random allocation is intended to make treatment groups comparable on average, while masking can reduce the influence of expectations on care, assessment, and reporting. The registry describes masking as quadruple, but does not specify the roles covered by that designation in the information available for this analysis. The record also does not report the allocation ratio, the randomization procedure, or details of how masking was maintained.

The primary outcome was change from baseline in synovial-tissue messenger RNA expression at Day 28. The stated measurement timeframe includes Day -7 as baseline and Day 28. Secondary outcomes include ACR response measures and disease-activity measures using DAS28 with CRP or ESR, including some change-from-baseline and threshold outcomes at Day 28 and Day 35. The registry lists 91 outcome measures, but numerical results for the primary and secondary outcomes are not reported in the registry record. The record lists no analysis entries. Further detail about the statistical analysis plan, sample-size justification, interim analyses, and handling of protocol deviations is 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.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Full analysis set (FAS) included all randomized participants who received at least 1 dose of the study medication. Analyses of tumor necrosis factor alpha(TNFα), receptor activator of nuclear factor kappa-B ligand(RANKL), osteoprotegerin(OPG) were not performed due to insufficient samples and lack of appropriate method to process/analyze samples.

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.

6. Primary Endpoint

The registry lists the primary outcome as Change From Baseline in Synovial Tissue Messenger Ribonucleic Acid (mRNA) Expression at Day 28, measured over Day -7 (Baseline), Day 28.

The primary endpoint is change from baseline in synovial-tissue messenger RNA expression at Day 28. Synovial tissue was sampled by biopsy, and the record describes measuring gene expression by quantitative PCR using a standard-curve method. Expression was normalized to control genes and reported as relative expression within synovial tissue, in relative expression units. The stated timeframe identifies Day -7 as baseline and Day 28 as the follow-up.

The markers named include IL-1beta, IL-6, MMP3, CD19, CD3E, JAK1, JAK2, JAK3, STAT1, ISG15, CXCL10, CCL2, phospho-STAT1, and phospho-STAT3. The primary outcome description also names TNFalpha, RANKL, and OPG, but says their analyses were not performed because of insufficient samples. The endpoint is therefore a group of biological measurements rather than one single value that captures all aspects of rheumatoid arthritis.

In general, tissue gene-expression measures can be used to explore biological response to an intervention. They are not the same as symptoms, function, or a clinical disease-activity score. The registry record does not report the numerical changes, group means, variability, or treatment comparisons for the primary endpoint, so the direction and precision of the measured changes cannot be assessed from this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary endpoint summarize?

The primary outcome is described as a mean of a continuous measure: change from baseline in gene-expression values. A mean provides a central summary of measured values across participants. The registry also identifies standard deviation as the dispersion measure. In general, a standard deviation describes how spread out individual observations are around the mean; it is not the same as the uncertainty in a treatment-group comparison. The registry record does not provide the endpoint means or standard deviations, so neither the group distributions nor the contrast between groups can be reviewed.

The expression values are relative expression units, normalized to control genes. Such a measure represents expression relative to the normalization reference, rather than a direct count of clinical symptoms or a standalone measure of disease severity. The record describes quantitative PCR using a standard curve generated by linear regression of log threshold cycle against log cell number. This explains the measurement approach, but does not supply the observed values or establish how reliably each marker was measured in this study.

How should uncertainty be understood?

In general, an estimate describes the result in the observed study, while a confidence interval describes a range of values compatible with the data under the assumptions of the statistical method. A narrow interval indicates greater precision than a wide interval, although neither interval alone determines clinical importance. A p-value, when used, addresses compatibility with a specified null model; it is not the probability that a treatment works or that a result is true. No confidence intervals or p-values for the primary comparison are reported in the registry record. Therefore the precision and statistical evidence for any difference cannot be evaluated.

Standard deviations and confidence intervals answer different questions. Standard deviations describe variability among observed measurements, whereas confidence intervals express uncertainty around an estimate. A treatment comparison would normally need an estimate of the difference between groups and an uncertainty measure. Neither is available for the primary outcome in the registry record. There is thus no basis for interpreting the size or precision of an effect from the endpoint description alone.

What does randomization and masking contribute?

In general, randomization assigns participants to groups by chance and can reduce systematic differences at the start of a trial. It does not guarantee that every characteristic is balanced, particularly in a study with limited enrollment. Masking can reduce bias arising when knowledge of group assignment affects participant reports, clinical decisions, outcome assessment, or analysis. The record classifies the study as randomized and quadruple masked, but does not describe the specific methods or people included in the masking designation. These design features support a fair comparison in principle, but they do not replace reported results or resolve uncertainty caused by missing outcome data.

The parallel design means participants were assigned to one regimen rather than being described as receiving each regimen in sequence. The placebo-plus-methotrexate group provides the stated comparator to CP-690,550 plus methotrexate. The record does not report an allocation ratio or numerical primary-outcome results, so group-level biomarker comparisons cannot be reconstructed from the information recorded.

How should multiple outcomes be considered?

In general, testing many outcomes or markers raises multiplicity concerns: the more comparisons considered, the greater the opportunity for chance findings. Possible approaches can include prespecifying a primary comparison, adjusting inference for multiple tests, or treating exploratory findings as hypothesis-generating. Which approach was used, and whether the analysis accounted for multiple markers or outcome measures, is not reported in the registry record. The primary endpoint itself names several molecular markers, and the record lists 91 outcome measures overall. These registry entries warrant caution about selecting individual positive results, but no specific multiplicity procedure can be attributed to this trial from the record.

What can sample-size calculations tell readers?

In general, a sample-size calculation estimates the number of participants needed to detect a prespecified effect under stated assumptions about the significance level, allocation, and statistical model. It is a planning exercise, not a measure of the probability that a completed trial detected an effect. The registry's planning description refers to a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects expressed as fractions of an observed effect. It also distinguishes event totals for time-to-event calculations from participants per arm for other outcomes. The resulting numerical planning estimates are not reported in the registry record. The record does not state that these assumptions formed the trial's original design, and no sample-size justification is reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 91 outcome measures, including multiple molecular markers in the primary endpoint and several secondary clinical outcomes. Considering many outcomes can complicate interpretation because chance variation may produce apparently notable results among numerous comparisons. In general, a statistical analysis plan may address this through prespecification, adjustment, or an explicitly exploratory interpretation. Whether the trial used any such approach is not reported in the registry record. The record lists no analysis entries, so it does not identify a testing hierarchy or a multiplicity adjustment.

The primary analysis population is described as the full analysis set: randomized participants who received at least one dose of study medication. This definition does not by itself explain how participants with missing measurements, treatment discontinuation, or protocol deviations were handled. The number of participants contributing primary biomarker data, the amount and pattern of missing data, and any imputation or other missing-data method are not reported in the registry record.

The primary outcome description states that analyses of TNFalpha, RANKL, and OPG were not performed because of insufficient samples. The record does not provide the number of samples available for those markers or the implications for the remaining marker analyses. Details of any exclusions from individual analyses and the reasons for them are not reported in the registry record. These gaps matter because an analysis population defined by dosing does not necessarily equal the population with complete data for every biomarker.

11. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 2% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse events for two groups. For CP-690,550, 15 participants were at risk and zero were affected by serious adverse events. For placebo, 14 participants were at risk and zero were affected. The record does not list serious adverse-event terms. It reports other adverse events affecting 7 participants in the CP-690,550 group and 10 participants in the placebo group, with 15 and 14 participants at risk, respectively. Death counts are not reported in the registry record.

These are event counts as entered in the registry, not a complete description of event severity, timing, duration, or causal attribution. A count of zero recorded serious events does not establish that the risk was absent, especially when the registry does not provide further detail about follow-up or event ascertainment. The other-adverse-event counts do not indicate how many events each affected participant experienced, and the record does not provide event terms for those counts. Without comparative estimates and uncertainty intervals, these figures should be read descriptively rather than as a precise estimate of relative safety.

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

This trial is relevant as an exploratory study of biological measurements in synovial tissue in people with active rheumatoid arthritis. Its randomized, placebo-controlled design compared CP-690,550 plus methotrexate with placebo plus methotrexate, and its primary endpoint focused on change in messenger RNA expression from baseline to Day 28. The record also identifies clinical response and disease-activity measures as secondary outcomes.

What the record does not establish is the size or direction of the primary biomarker changes, whether the groups differed, or how precise any such difference was. Numerical outcome results, estimates of uncertainty, and statistical tests are not reported in the registry record. The clinical outcome names likewise cannot be interpreted as evidence that participants achieved those outcomes. No treatment conclusion should be drawn from the study title, design, or outcome definitions alone.

In general, a biomarker change can help describe biological activity, but its meaning is not automatically equivalent to a change in symptoms, function, or other clinical outcomes. This trial's registry record does not provide the results needed to connect the listed tissue markers with the listed clinical measures. It also does not report a multiplicity strategy or details of missing-data handling, both of which would be relevant to judging a set of exploratory measurements.

The safety counts are limited descriptive information. Zero recorded serious adverse events in either group does not prove absence of risk, and the other-event counts alone do not provide a precise comparative safety estimate. The available record therefore supports understanding the trial's design, measurements, and some event counts, while leaving the central treatment-effect questions unresolved.

13. Why This Trial Matters Statistically

Statistically, the study illustrates the distinction between a mechanistic or pharmacodynamic question and a clinical efficacy question. Its primary outcome concerns gene expression in synovial tissue, while its secondary outcomes include response criteria and disease-activity scores. These outcomes describe different aspects of a trial and should not be treated as interchangeable. A molecular measurement may be informative about biological processes, but its relevance to clinical outcomes must be evaluated with outcome data rather than assumed.

The record also highlights the complexity of interpreting a set of molecular endpoints. It names numerous markers and lists 91 outcome measures overall. In general, a larger set of comparisons increases the importance of prespecification, transparent reporting, and careful treatment of multiplicity. Here, no analysis entries or multiplicity procedures are reported in the registry record. The results needed to examine whether individual markers changed, and how those changes compare across groups, are also absent.

The study's randomized and masked design provides an appropriate framework for comparing regimens, but design quality and result reporting are separate considerations. Randomization can support causal interpretation when outcomes are adequately measured and analyzed; it cannot compensate for missing estimates, missing uncertainty measures, or unclear handling of incomplete data. The stated full analysis set helps define who was intended for analysis, while the record does not explain the availability of data for each marker.

Finally, the listed safety counts demonstrate why counts need context. Participants at risk and affected counts are useful descriptive information, but without event detail and uncertainty they cannot establish a precise comparative safety profile. The record is therefore statistically useful for identifying what was planned and measured, and for recognizing important reporting gaps, but it does not support numerical conclusions about treatment effects.

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 for interpreting this trial from the registry record is the absence of numerical results for the primary outcome. There are no reported group means, standard deviations, between-group estimates, confidence intervals, or p-values for the synovial-tissue expression measures. Numerical results for the listed secondary outcomes are also not reported in the registry record. As a result, the direction, magnitude, and precision of treatment-group differences cannot be evaluated.

The primary outcome covers multiple markers, and the record lists 91 outcome measures overall, but it does not report how multiplicity was addressed. It also lists no analysis entries. The registry record does not describe missing-data procedures, the number of participants with usable measurements for each marker, or whether all planned analyses were completed. It states that TNFalpha, RANKL, and OPG analyses were not performed because of insufficient samples.

The record identifies the full analysis set as randomized participants who received at least one dose, but does not provide further details about adherence, discontinuations, protocol deviations, or participant flow. Allocation ratio, the randomization procedure, masking implementation, and the statistical analysis plan are not reported in the registry record. The planning assumptions are described, but numerical planning estimates and the trial's own sample-size justification are not reported.

Safety reporting is also limited: the record gives affected counts for serious and other adverse events but does not provide serious-event terms, event timing, or death counts. These limitations restrict interpretation of both efficacy-related and safety-related findings.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study To Evaluate The Mechanism Of Action Of CP-690,550 In Patients With Rheumatoid Arthritis — NCT00976599.
• Registry record last updated 2013-01-09; status last verified 2012-12.
• Results first posted 2013-01-09.
• 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

NCT00976599 is a completed, randomized, quadruple-masked, placebo-controlled, parallel-group phase 2a study in rheumatoid arthritis. It enrolled 29 participants and compared CP-690,550 plus methotrexate with placebo plus methotrexate. The official title describes oral dosing twice daily for four weeks.

The primary outcome was change from baseline in synovial-tissue messenger RNA expression at Day 28. The registry describes quantitative PCR and relative-expression units, and lists multiple markers. It states that TNFalpha, RANKL, and OPG analyses were not performed because of insufficient samples. Secondary outcomes include ACR responses and DAS28 measures.

Numerical primary and secondary outcome results, the statistical analysis plan, missing-data methods, and multiplicity procedures are not reported in the registry record. The record lists serious adverse events affecting zero participants in each group, other adverse events affecting 7 and 10 participants, and does not report death counts.