This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for A Clinical Trial To Evaluate PF-05089771 On Its Own And As An Add-On Therapy To Pregabalin (Lyrica) For The Treatment Of Pain Due To Diabetic Peripheral Neuropathy (DPN) (NCT02215252), a randomized phase 2 study. The primary outcome is Daily Pain Numeric Rating Scale (NRS).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02215252 |
| Phase | Phase 2 |
| Condition | Diabetic Neuropathy, Painful |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 141 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
Participants with painful diabetic peripheral neuropathy. The registry record states that the full analysis set included randomized participants who received at least one dose of study medication. The recorded enrollment was 141.
Intervention
PF-05089771 150 mg as monotherapy, or PF-05089771 150 mg combined with pregabalin 300 mg. The intervention listings identify these as drug regimens.
Comparator
The trial included matched placebo for PF-05089771 150 mg and pregabalin 300 mg, as well as pregabalin 300 mg. The official title describes the study as placebo and active controlled.
Primary question
The study was designed to evaluate PF-05089771 as a monotherapy and as an add-on to pregabalin for painful diabetic peripheral neuropathy. The primary measure was average pain based on daily pain numeric rating scale scores during treatment. The registry record does not report numerical results for the primary endpoint, so it does not establish the size or precision of any difference between treatment groups.
3. Trial Design
This was a randomized, double-blind, parallel-group phase 2 study sponsored by Pfizer. Its official title describes placebo and active control and identifies the two treatment approaches under evaluation: PF-05089771 as monotherapy and as an add-on to pregabalin. The listed interventions were PF-05089771 150 mg, matched placebo for PF-05089771 150 mg and pregabalin 300 mg, pregabalin 300 mg, and PF-05089771 150 mg plus pregabalin 300 mg.
The registry record lists enrollment as 141. The recorded study start was 2014-11-10, and primary completion was 2015-07-15; the study status is completed. These details describe the study record and do not provide information about the number of participants who completed treatment or contributed data at each visit.
The primary endpoint was a continuous pain measure assessed at baseline, Week 1, Week 2, Week 3 and Week 4. The record defines the analysis population as randomized participants who received at least one dose of study medication. It does not report arm-specific enrollment, the allocation ratio, treatment adherence, or the number analyzed at each visit.
Several secondary outcomes are listed, including responder rates based on 30% and 50% improvement in mean pain response, and Neuropathic Pain Symptom Inventory measures. The registry record lists 18 outcome measures and 28 analyses. It does not report the detailed protocol, allocation sequence method, or masking procedures beyond identifying the study as double blind.
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 number of 141 participants were the anticipated to be enrolled based on a discontinuation rate calculated from previous Pfizer DPN studies. The study discontinuation rate was lower than anticipated, hence fewer participants were randomized.
Overall Study
| Stage | PF-05089771 150 mg BID | Pregabalin | Placebo |
|---|---|---|---|
| STARTED | 44 | 46 | 45 |
| COMPLETED | 42 | 38 | 41 |
| NOT COMPLETED | 2 | 8 | 4 |
Reasons for not completing this period:
| Reason | PF-05089771 150 mg BID | Pregabalin | Placebo |
|---|---|---|---|
| Adverse Event | 1 | 5 | 2 |
| Lost to Follow-up | 0 | 0 | 1 |
| Does not Meet Entrance Criteria | 0 | 1 | 0 |
| Protocol Violation | 0 | 1 | 0 |
| Withdrawal by Subject | 1 | 0 | 0 |
| Other | 0 | 1 | 1 |
Analysis population for the primary outcome, as defined in the registry: The full analysis set included all randomized participants who received at least one dose of study medication.
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 safety analysis set consisted of all participants who received at least one dose of study medication.
| Characteristic | Unit | PF-05089771 150 mg BID | Pregabalin | Placebo | Total |
|---|---|---|---|---|---|
| Participants analysed | 44 | 46 | 45 | 135 | |
| Age, Continuous | years | 59.3 (SD 9.4) | 58.1 (SD 11.3) | 59.2 (SD 10.9) | 58.9 (SD 10.5) |
| Sex: Female, Male: Female | Participants | 17 | 19 | 14 | 50 |
| Sex: Female, Male: Male | Participants | 27 | 27 | 31 | 85 |
6. Primary Endpoint
The registry lists the primary outcome as Daily Pain Numeric Rating Scale (NRS), measured over Baseline, Week 1, Week 2, Week 3 and Week 4.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | Unit on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was the Daily Pain Numeric Rating Scale (NRS), reported as the mean of the last 7 days' daily pain scores during the treatment period. The registry describes the scale as an 11-point scale, where 0 means no pain and 10 means worst possible pain. The stated assessment times were baseline, Week 1, Week 2, Week 3 and Week 4.
A daily record can capture changes in a participant's experience over time rather than relying only on a single retrospective rating. Averaging daily scores over the stated period can also smooth day-to-day variation. These are general features of repeated symptom measurement, not evidence that this particular endpoint is more reliable or informative than other measures in this study.
The endpoint is continuous: its stated parameter is a mean, and its dispersion is a standard deviation. A mean describes the group average, while a standard deviation describes variation among observed scores. The record gives the endpoint definition but does not report the group means, standard deviations, estimated treatment contrasts, or confidence intervals. It therefore does not permit a numerical assessment of the primary outcome from the registry record alone.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes the study's question and endpoint but does not report numerical primary-endpoint results. The primary outcome has several categories or time points and is not reduced in the record to one comparison. Consequently, no treatment-group mean, mean difference, confidence interval, or primary-outcome p-value can be stated from this record. The direction, magnitude, and precision of any primary-endpoint difference are not reported in the registry record.
This distinction matters because a design description is not a result. Randomization, double masking, and a parallel-group design describe how the trial was organized; they do not themselves show whether observed pain scores differed between groups. Similarly, the study's phase and completed status do not convey the size or statistical uncertainty of an effect.
The endpoint was assessed at baseline and several follow-up visits. Repeated measurements can provide information about the course of pain during treatment, but interpretation depends on the reported estimates and on how the repeated observations were analyzed. The registry record does not report a model for repeated measures, an adjusted or unadjusted contrast, or a stated primary comparison. It also does not report confidence intervals for the endpoint.
The record lists secondary responder outcomes defined using 30% and 50% improvement thresholds, along with Neuropathic Pain Symptom Inventory domains and total score. Their listing identifies outcomes of interest, but without numerical results it does not show how many participants met a threshold or how groups compared. The record lists 18 outcome measures and 28 analyses; it does not explain the relationship between those counts or identify a multiplicity adjustment.
Safety listings are separate from the primary efficacy endpoint. The adverse-event record gives serious and other affected-participant counts for three titled groups, while the intervention list includes four regimens. These counts should be read as descriptive record entries, not as proof of a causal difference. The registry record does not report a statistical comparison for safety, and it does not give deaths as a count. Serious adverse event terms and percentages are listed, but their denominators and detailed analytic context are not reported.
Overall, the available registry information supports a description of the planned clinical question, design, endpoint, and selected safety counts. It does not support a conclusion about the primary outcome's magnitude, statistical significance, or precision.
9. Statistical Methods Explained
The design labels describe distinct features. Randomized means participants were assigned to study groups through a random process, as stated in the registry record. Double blind indicates that the record identifies the study as double blind, but it does not specify who was masked or the practical masking procedures. Parallel group means participants were assigned to a group and assessed under that group's regimen, rather than being described as crossing between regimens. These are general explanations of design terms; detailed procedures are not reported in the registry record.
What does a mean endpoint represent?
The primary outcome is a continuous measure summarized by a mean and standard deviation. In general, a mean gives a central group-level summary, while a standard deviation describes the spread of individual observations around that average. A difference between group means, if reported, would describe an average contrast, not the experience of every participant. The registry record does not report the primary group means or a treatment contrast.
Why does the assessment schedule matter?
The Daily Pain NRS was assessed at baseline, Week 1, Week 2, Week 3 and Week 4. Repeated assessment can characterize a symptom's pattern over time. However, analysis of repeated measurements requires choices about how observations across visits are combined or modeled, and how missing visits are handled. Those choices can affect the estimate and its uncertainty. The analysis method for the repeated pain observations is not reported in the registry record.
How should uncertainty be understood?
In general, a confidence interval gives a range of estimates compatible with the data and the chosen statistical procedure. Its width conveys precision: wider intervals indicate greater uncertainty about the estimated effect, while narrower intervals indicate greater precision. A confidence interval does not by itself establish clinical importance. No primary-endpoint estimate or confidence interval is reported in the registry record, so precision cannot be evaluated for the main outcome.
A p-value, in general, measures how incompatible the observed data are with a specified null model under the assumptions of the analysis. It is not the probability that a treatment is effective, nor does it describe the size of an effect. The registry record does not report a primary-outcome p-value. It also does not identify a primary contrast among the several treatment regimens and visits in a way that would allow a reader to reconstruct a test.
What does over-dispersion mean in general?
For outcomes such as counts or binary responses, a statistical model may assume a particular level of variability. Over-dispersion means the observed variation is greater than the model assumes. If not accounted for, this can make standard errors too small and uncertainty appear lower than it is. This is a general statistical concept; the registry record does not report an over-dispersion assessment or identify a count model for the listed outcomes. The primary endpoint itself is described as a continuous mean, not a count.
How should planning illustrations be read?
The registry record describes a sample-size planning illustration based on the observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. The illustration is framed around detecting a stated fraction of the observed effect. Time-to-event examples are described as total event counts, while other examples are described as participants per arm. No numerical illustration outputs are reported in the record available for this analysis.
Such planning values are hypothetical design calculations, not observed trial findings and not observed power. When planning from an observed effect, the resulting illustration depends on that effect and on the stated assumptions. It should not be interpreted as an independently justified target sample size for this trial. The registry record does not report the trial's own sample-size justification or a protocol-based calculation.
What remains unspecified?
The registry record does not report the statistical model, covariates, handling of baseline values, estimand, treatment-effect contrast, interim analyses, or detailed multiplicity strategy. Those elements should not be inferred from the design labels or endpoint description. The reported details support describing the planned measurement and analysis population, but not reproducing the analysis or its uncertainty.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists 18 outcome measures and 28 analyses. The primary outcome is described across baseline, Week 1, Week 2, Week 3 and Week 4, and the record notes that the primary outcome has several categories or time points and is not reduced to one comparison. Secondary outcomes include responder rates using 30% and 50% improvement thresholds and several Neuropathic Pain Symptom Inventory domains and total score. This range of outcomes and assessments raises a general multiplicity issue: when many comparisons are examined, the chance of at least one apparently unusual result can increase.
Methods for addressing multiplicity can include prespecifying a hierarchy or adjusting inference across selected tests. The registry record does not report whether such a strategy was used, which comparisons were considered confirmatory, or whether the listed analyses were exploratory. No p-values or numerical outcome estimates are reported, so the impact of multiplicity on reported efficacy findings cannot be assessed.
The full analysis set is defined as all randomized participants who received at least one dose of study medication. The registry record does not report how many participants were included in that set, how participants were handled after discontinuing treatment, or whether any other analysis populations were used. It also does not report missing-data methods, reasons for missing observations, or the amount of missing endpoint data at each visit.
These omissions limit interpretation of both the analysis population and repeated pain measurements. In general, missing-data assumptions can influence estimates when outcomes are unavailable, while multiplicity choices affect how evidence across outcomes is interpreted. Neither the assumptions nor the procedures can be inferred from the outcome titles. They 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 |
|---|---|---|---|
| PF-05089771 150 mg BID | 1 | 44 | 2.3% |
| Pregabalin | 1 | 46 | 2.2% |
| Placebo | 0 | 45 | 0.0% |
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 |
|---|---|
| PF-05089771 150 mg BID | 3 of 44 |
| Pregabalin | 12 of 46 |
| Placebo | 10 of 45 |
Most frequent serious adverse event terms
| Event term | Organ system | PF-05089771 150 mg BID | Pregabalin | Placebo |
|---|---|---|---|---|
| Cardiac failure congestive | Cardiac disorders | 0 of 44 | 1 of 46 | 0 of 45 |
| Pneumonia | Infections and infestations | 1 of 44 | 0 of 46 | 0 of 45 |
| Chronic obstructive pulmonary disease | Respiratory, thoracic and mediastinal disorders | 1 of 44 | 0 of 46 | 0 of 45 |
Most frequent non-serious adverse event terms
| Event term | Organ system | PF-05089771 150 mg BID | Pregabalin | Placebo |
|---|---|---|---|---|
| Headache | Nervous system disorders | 2 of 44 | 3 of 46 | 4 of 45 |
| Dizziness | Nervous system disorders | 0 of 44 | 5 of 46 | 2 of 45 |
| Upper respiratory tract infection | Infections and infestations | 1 of 44 | 1 of 46 | 3 of 45 |
| Nausea | Gastrointestinal disorders | 0 of 44 | 3 of 46 | 1 of 45 |
| Vulvovaginal pruritus | Reproductive system and breast disorders | 0 of 17 | 1 of 19 | 0 of 14 |
Serious events with the highest arm-level rate: pneumonia (2.3%), chronic obstructive pulmonary disease (2.3%), cardiac failure congestive (2.2%).
The registry adverse-event listing gives serious-event counts for PF-05089771 150 mg BID, pregabalin, and placebo. The corresponding numbers at risk are 44, 46 and 45, and the numbers with serious adverse events are 1, 1 and 0, respectively. For other adverse events, the numbers at risk are 44, 46 and 45, and the numbers affected are 3, 12 and 10, respectively. These are participant counts in the registry listing, not estimates of treatment effect.
The intervention list includes PF-05089771 plus pregabalin, but the adverse-event groups listed do not include a separate combination-treatment row. The registry record does not report a serious-event count for that regimen in the displayed adverse-event data. Deaths are recorded as null for the listed groups; this should not be converted into a claim that there were no deaths.
The record lists pneumonia and chronic obstructive pulmonary disease at 2.3% each, and cardiac failure congestive at 2.2%, among its top serious terms. The registry record does not report the denominator or further context for these percentages. A serious-event count does not by itself establish that the event was caused by a treatment. These entries are descriptive and do not provide a formal between-group safety comparison.
12. What the Result Does, and Does Not, Mean
The study record identifies a randomized, double-blind, parallel-group phase 2 trial evaluating PF-05089771 alone and with pregabalin for painful diabetic peripheral neuropathy. It specifies a daily pain endpoint, an assessment schedule, an analysis-population definition, selected secondary outcomes, and adverse-event counts. This information helps explain what the trial was intended to evaluate and what kinds of outcomes were registered.
It does not establish whether PF-05089771, pregabalin, or their combination produced a particular change in pain. The registry record does not report numerical primary-endpoint results, treatment contrasts, confidence intervals, or a primary-outcome p-value. It therefore does not show the direction, magnitude, or precision of an efficacy difference. A design description and a completed status are not substitutes for comparative outcome estimates.
The listed secondary outcome names likewise do not reveal the observed responder rates or symptom scores. The adverse-event counts provide descriptive information for the listed groups, but do not establish causation or support a formal comparative safety conclusion. The record does not give a separate adverse-event row for the combination regimen, and its null entries for deaths should not be interpreted as numerical zeroes.
In general, clinical interpretation requires both an estimate of the difference and information about its uncertainty, alongside details about the analysis and the outcome's relevance. Those elements are not reported for the primary endpoint in the registry record. No conclusion about treatment benefit or lack of benefit follows from the available information alone.
13. Why This Trial Matters Statistically
This trial is statistically notable for the structure of its question: it evaluates PF-05089771 as a monotherapy and as an add-on to pregabalin, with placebo and active-control regimens named in the record. That design makes the choice of treatment contrasts important. A monotherapy comparison and an add-on comparison address different questions, and the registry record does not identify a single numerical primary contrast among the regimens.
The outcome plan also illustrates the distinction between a clearly defined measure and a fully reported analysis. The Daily Pain NRS is described by its scale, averaging window, assessment visits, and summary parameter. Yet without estimates, uncertainty intervals, or a stated analysis model, readers cannot assess the size or precision of the primary outcome findings. The definition alone cannot answer the treatment question.
The record lists multiple outcome measures and analyses, making multiplicity and prespecification relevant considerations. It also describes a sample-size planning illustration based on the observed effect and stated assumptions. Such an illustration is useful only as a planning scenario; it is not observed power and does not replace the trial's own sample-size justification, which is not reported in the registry record.
Finally, the gap between the four listed intervention regimens and the three adverse-event groups in the safety listing shows why outcome coverage should be checked across arms before drawing broad comparisons. Statistically, transparent reporting of contrasts, missing-data handling, multiplicity, and uncertainty is essential for interpreting a multi-arm study. Those details are not reported in the registry record.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The central limitation is that numerical results for the primary pain endpoint are not reported in the registry record. Without group summaries, contrasts, or uncertainty estimates, the primary question cannot be answered quantitatively. The endpoint covers several visits, but no repeated-measures analysis method or single primary comparison is stated.
The registry defines the full analysis set but does not report its size, arm-specific analyzed counts, participant flow, or follow-up completeness. Missing-data methods and reasons for missing observations are not reported. These omissions matter for an endpoint collected repeatedly during treatment because the amount and pattern of unavailable data can affect interpretation.
The record lists 18 outcome measures and 28 analyses, but does not explain the analysis plan or multiplicity procedures. It does not report the trial's own sample-size justification. The planning illustration assumptions are described, but no numerical planning outputs are included in the record used for this analysis.
The adverse-event listing covers three groups, while four treatment regimens appear in the intervention list. A separate adverse-event count for the combination regimen is not reported in the listed safety groups. Deaths are null entries, and the record does not clarify them as a numerical count. The context and denominators for the percentages attached to top serious-event terms are also not reported.
Other protocol and analysis details, including allocation procedures, detailed masking arrangements, interim analyses, and the statistical model, are not reported in the registry record. These limitations constrain both reconstruction of the trial analysis and interpretation of its results.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Clinical Trial To Evaluate PF-05089771 On Its Own And As An Add-On Therapy To Pregabalin (Lyrica) For The Treatment Of Pain Due To Diabetic Peripheral Neuropathy (DPN) — NCT02215252.
- Registry record last updated 2017-05-05; status last verified 2017-03.
- Results first posted 2017-05-05.
- 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.
Continue through the Clinical Biostats statistical pathway
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18. Record Summary
NCT02215252 is a completed, randomized, double-blind, parallel-group phase 2 study sponsored by Pfizer. Its stated purpose was to evaluate PF-05089771 as monotherapy and as an add-on to pregabalin for painful diabetic peripheral neuropathy. The recorded enrollment was 141; the study start was 2014-11-10, and primary completion was 2015-07-15.
The primary endpoint was average daily pain NRS, defined from the mean of the last 7 days' daily scores, with assessments at baseline, Week 1, Week 2, Week 3 and Week 4. The record lists 18 outcome measures and 28 analyses, along with responder and Neuropathic Pain Symptom Inventory secondary outcomes.
Numerical primary-endpoint results, analysis methods, missing-data procedures, and a multiplicity strategy are not reported in the registry record. The safety listing gives affected-participant counts for three groups, while the intervention list names four regimens.