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 The Maraviroc Central Nervous System (CNS) Study (NCT00982878), a na phase 1 study. The primary outcome is CSF (Cerebrospinal Fluid) : Plasma Ratio of Maraviroc 1H Magnetic Resonance Spectroscopy (1H-MRS).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00982878 |
| Phase | Phase 1 |
| Condition | HIV Infections |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 13 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Imperial College London |
| Results posted | Yes |
2. Clinical Question
The study asked about central nervous system exposure to maraviroc in HIV-1 infected subjects receiving a stable antiretroviral regimen that included maraviroc at steady state. Its registered primary outcome was the cerebrospinal-fluid-to-plasma ratio of maraviroc, assessed in connection with cerebral magnetic resonance spectroscopy. The outcome timeframe was 15 days.
This is a pharmacokinetic question: it concerns drug exposure in the central nervous system relative to exposure in plasma. It is not a comparison of maraviroc with another treatment, nor does the registry describe a clinical efficacy question. The record identifies a single-group model and no allocation to different treatment groups. It therefore does not set up a randomized treatment contrast or a like-for-like control comparison.
Population
HIV-1 infected subjects receiving stable antiretroviral therapy, including maraviroc. The registry lists enrollment of 13.
Intervention
Maraviroc, recorded as the study drug. The study purpose concerns CNS exposure while participants were receiving a stable regimen that included maraviroc at steady state.
Comparator
No comparator group is described. Allocation is listed as NA, and the study model is single group.
Primary question
What was the CSF-to-plasma ratio of maraviroc, as registered for assessment over 15 days using cerebral magnetic resonance spectroscopy?
The registry record does not report the numerical ratio, its variability, or an estimate of how precisely it was measured. It also does not report a comparison with a reference value or an alternative regimen. Consequently, the question can be described from the registered objective and endpoint, but the magnitude of CNS exposure cannot be determined from the outcome information in this record.
3. Trial Design
This is a Phase I study sponsored by Imperial College London. The registry lists it as completed, with a start date of 2009-09 and primary completion in 2010-07. Enrollment is listed as 13. The study is classified as a single-group model, with allocation recorded as NA and masking recorded as none.
Those design features matter when interpreting the purpose and reach of the study. A single-group pharmacokinetic study can describe measurements made in participants receiving the study drug, but it does not create a treatment contrast with a concurrent control group. The record does not describe randomized assignment or masking. It therefore does not support a randomized comparison between maraviroc and another regimen.
The brief summary says that the purpose was to describe CNS exposure in HIV-1 infected subjects on stable antiretroviral therapy, including maraviroc, at steady state. The intervention is listed as the drug maraviroc. No separate comparator arm or alternative intervention is listed. Although enrollment is reported as 13, the registry does not explain the relationship between that enrollment figure and the safety population, for which 12 are listed as at risk.
The primary outcome is a CSF-to-plasma ratio, with a mean as the parameter and full range as the dispersion measure. The stated timeframe is 15 days. The record lists a secondary outcome of number of participants with adverse events. It lists two outcome measures and zero analyses. Numerical results for the primary measure are not reported in the registry record, and details such as the analysis population, handling of missing measurements, and statistical analysis plan are not reported in the registry record.
The registry record does not report a sample-size justification, interim analyses, or protocol details beyond the information described. Sample-size calculations appearing alongside the results should be understood as planning illustrations under stated assumptions, not as evidence about the study's original design or its observed power.
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
| Stage | Maraviroc |
|---|---|
| STARTED | 13 |
| COMPLETED | 12 |
| NOT COMPLETED | 1 |
Reasons for not completing this period:
| Reason | Maraviroc |
|---|---|
| Physician Decision | 1 |
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 | Maraviroc |
|---|---|---|
| Participants analysed | 12 | |
| Age, Continuous | years | 42 (SD 7.9) |
| Sex: Female, Male: Female | Participants | 3 |
| Sex: Female, Male: Male | Participants | 9 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 7 |
| Race (NIH/OMB): White | Participants | 4 |
| Race (NIH/OMB): More than one race | Participants | 1 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United Kingdom | participants | 12 |
| Years since HIV diagnosis | years | 11 (SD 4.6) |
| Baseline CD4 cell count | cells/ul | 503 (SD 199) |
| BMI | kg/m^2 | 28 (SD 3.5) |
6. Primary Endpoint
The registry lists the primary outcome as CSF (Cerebrospinal Fluid) : Plasma Ratio of Maraviroc 1H Magnetic Resonance Spectroscopy (1H-MRS), measured over 15 days.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Full Range |
| Unit | ratio |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is titled “CSF (Cerebrospinal Fluid) : Plasma Ratio of Maraviroc 1H Magnetic Resonance Spectroscopy (1H-MRS).” Its stated purpose is to describe CNS exposure in HIV-1 infected subjects receiving a stable antiretroviral regimen, including maraviroc, at steady state. The endpoint is expressed as a ratio, with the mean listed as the summary parameter and full range as the measure of dispersion. The timeframe is 15 days.
In general, a CSF-to-plasma ratio expresses one measured quantity relative to another, allowing exposure in cerebrospinal fluid to be considered in relation to plasma exposure. A mean describes the average of observed values, while a full range describes the lowest and highest observed values. The range can communicate how far observations extend, but it does not by itself show how values are distributed between the extremes or how precisely the mean is estimated.
The registry description says assessment used in vivo cerebral 1H magnetic resonance spectroscopy. It also describes cerebral MRS imaging with T1- and T2-weighted images on a Phillips Achieva 1.5 Tesla MR scanner, studied by an experienced neuroradiologist. These details characterize the registered assessment approach. The actual ratio, its full range, and any estimate of precision are not reported in the registry record. Thus, the endpoint definition is available, but the observed level of CNS exposure cannot be evaluated from the numerical results in this record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record gives the study objective and the definition of its primary endpoint, but it does not report a numerical result for the CSF-to-plasma ratio. The listed endpoint summary is a mean with full range as the dispersion measure, yet the mean and range themselves are not reported in the registry record. No confidence interval, standard error, or other precision estimate for this endpoint is reported in the registry record either. The direction and magnitude of the measured ratio therefore cannot be interpreted from this record.
The design also sets a clear boundary on what can be concluded. This is a single-group study, with allocation recorded as NA and no masking. There is no registered comparator group. Consequently, the objective is descriptive CNS exposure rather than an estimate of a treatment difference. Even if the ratio result were available, this design would not establish how that measurement differs from another treatment or from an untreated state.
Enrollment is listed as 13, while the safety group lists 12 at risk. The record does not explain this difference, and it does not report how many participants contributed to the primary endpoint. The safety figures therefore should not be used to infer the number included in the pharmacokinetic analysis.
The registry lists zero analyses. This means the record does not present a statistical analysis result for the primary outcome. It does not establish that no analysis was performed outside the registry; it indicates only that no analyses are listed in this record. Details of a statistical analysis plan, including the handling of repeated or incomplete measurements, are not reported in the registry record.
For adverse events, the Maraviroc group lists 12 at risk and zero affected for both serious and other adverse events, with zero deaths. These are the recorded counts for the stated safety group. They do not establish that no adverse events could occur, and the registry does not provide event-level descriptions or additional information about ascertainment in the record. The absence of reported events in these fields should be read as a description of the recorded observations, not as proof of no risk.
Any sample-size illustration associated with this study is distinct from the trial's observed findings. Its stated assumptions include a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects defined as fractions of an observed effect. Those are hypothetical planning conditions, not the design of this single-group study. The observed effect needed to anchor such an illustration is not reported in the registry record, and the illustrations are not observed power.
9. Statistical Methods Explained
The registered outcome is a ratio summarized by a mean and a full range. These choices describe the intended form of the endpoint summary, but they do not supply the underlying participant measurements. Since the registry does not report the observed mean or range, the actual distribution of the endpoint cannot be reconstructed from the record.
What does a mean describe?
In general, a mean is an arithmetic summary of observed values. It can provide a compact description of the center of a set of measurements, but its interpretation depends on the values contributing to it. A mean alone does not show whether most measurements are close to the center, whether values are skewed, or whether a small number of extreme values have substantial influence. Those considerations matter for ratios as well as for other continuous outcomes. The registry does not report participant-level values or a distributional summary beyond the specified full range.
What does the full range add?
In general, a full range reports the two observed extremes. It can show the span of measured values, but it is sensitive to extremes and does not describe the pattern of observations between them. It is not a confidence interval and should not be interpreted as one. A range also does not, on its own, show the precision of a mean estimate. Here, the record identifies full range as the dispersion measure but does not provide its endpoint values.
How should a ratio be read?
In general, a ratio places a numerator in relation to a denominator. For a CSF-to-plasma ratio, the registered concept is CNS-related exposure relative to plasma exposure. Interpretation requires the observed ratio and enough methodological context to understand how the underlying measurements were obtained. The record identifies the ratio and describes cerebral MRS assessment, but it does not report the numerical ratio or additional assay and calculation details. No direction or magnitude should be inferred in the absence of the result.
What would a confidence interval mean?
In general, a confidence interval expresses uncertainty around an estimated quantity under a specified statistical procedure. A narrower interval indicates greater precision under that procedure, while a wider interval indicates less precision. An interval is not a range of participant observations and does not guarantee that the true value lies within its endpoints. No confidence interval is reported for the primary outcome in the registry record. Nor does the record give a standard error or another estimate from which that precision could be assessed.
Why does the design shape the analysis?
A single-group design describes observations within the group receiving the study drug. Without a comparator group, it does not estimate a between-group treatment contrast. Allocation is listed as NA and masking as none. The record describes a pharmacokinetic objective at steady state on stable antiretroviral therapy that included maraviroc; it does not describe a randomized comparison. Therefore, inferential statements about differences between treatment strategies would not be supported by the registered design.
The record lists zero analyses. No model, hypothesis test, or adjustment procedure for the primary endpoint is reported in the registry record. The endpoint's mean and full range are specified as summary choices, but these alone do not define a complete analysis plan. In general, a statistical analysis description would clarify which participants and measurements contribute, how missing observations are handled, and what uncertainty estimates are calculated. Those details are not reported in the registry record.
What is over-dispersion, and is it relevant?
In general, over-dispersion occurs when variability in data is greater than a statistical model assumes. It can make model-based uncertainty estimates unreliable if the extra variability is ignored. This concept is especially relevant to certain count-data models. The primary endpoint in this study is a ratio summarized by a mean and range, and the registry does not report a model or participant-level data that would allow assessment of over-dispersion. It should not be assumed to be present or absent in this study.
The record also lists a sample-size planning illustration. Its stated conditions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a stated fraction of the observed effect. These conditions describe an illustration for planning, not the actual single-group design. The record does not report the observed effect used for that illustration or a sample-size justification for the study itself. Such planning quantities are not observed power and do not change the interpretation of the registered outcome.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary outcome concerning the CSF-to-plasma ratio of maraviroc and a secondary outcome concerning the number of participants with adverse events. It also lists two outcome measures and zero analyses. The record does not describe a family of confirmatory hypotheses, a testing sequence, or an adjustment for multiple comparisons. Whether multiplicity was addressed in a separate analysis plan is not reported in the registry record.
Missing-data handling is not reported in the registry record. The record does not state how incomplete endpoint measurements were handled, whether participants could be excluded from an analysis, or how the analysis population was defined. Enrollment is listed as 13, while 12 are listed as at risk for the safety group; the reason for this difference and its relation to primary endpoint availability are not reported in the registry record. No participant flow details are given that would resolve this issue.
In general, missing observations can affect the interpretation of a mean if the participants with available measurements differ from those without them. A clear analysis-population definition and a description of missingness help readers assess that possibility. No such details are available in the registry record, so the number of observations contributing to the primary endpoint and the implications of any missing measurements cannot be assessed.
The record identifies a single-group study and does not report an analysis population such as an intention-to-treat or per-protocol population. Those labels and the criteria for inclusion are not reported in the registry record. The absence of these details is a limitation of the registry information; it does not establish how the study team handled missing data or populations elsewhere.
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 |
|---|---|---|---|
| Maraviroc | 0 | 12 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Maraviroc | 0 of 12 |
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 |
|---|---|
| Maraviroc | 0 of 12 |
The Maraviroc safety group lists 12 participants at risk. For serious adverse events, zero are listed as affected; for other adverse events, zero are listed as affected; and deaths are listed as zero. These figures describe the counts recorded for the safety group. The registry does not list top serious-event terms.
These counts should be read as recorded observations, not as proof that an event is impossible or that the drug has no safety risks. A zero count in a group of this size can coexist with uncertainty about uncommon events, and the registry record does not provide additional detail about event ascertainment, duration of safety observation, or event-level reporting. Those details are not reported in the registry record.
Enrollment is listed as 13, whereas the safety group lists 12 at risk. The registry does not explain why the figures differ. It is therefore not appropriate to assume that the safety denominator represents all enrolled participants or to infer a reason for the difference. The safety counts also do not indicate how many participants contributed to the primary pharmacokinetic endpoint.
12. What the Result Does, and Does Not, Mean
The record describes a Phase I study intended to characterize CNS exposure to maraviroc among HIV-1 infected subjects receiving stable antiretroviral therapy that included maraviroc at steady state. It identifies a CSF-to-plasma ratio as the primary outcome, with the mean and full range specified as summary measures. The assessment description refers to in vivo cerebral 1H magnetic resonance spectroscopy and imaging.
However, the numerical result for the primary endpoint is not reported in the registry record. Without the mean, range, or an uncertainty estimate, the magnitude and precision of the measured ratio cannot be evaluated. The registry therefore documents the question and the planned form of the outcome summary, but does not provide the result needed to quantify CNS exposure.
The study is single group, with allocation recorded as NA and masking as none. It does not include a registered comparator group. Its design can inform description of measurements within the group, but it cannot establish a randomized treatment difference or show how the ratio compares with another regimen. No efficacy outcome is described as the primary question in this record.
The adverse-event fields list zero affected for serious events and for other events among 12 at risk, and zero deaths. These counts are limited to the safety information recorded; they do not establish an absence of risk. The reason the safety denominator differs from the enrollment figure is not reported in the registry record.
More broadly, the registry lists zero analyses and does not report missing-data methods, analysis-population definitions, or the statistical plan. Any conclusions beyond the registered objective and recorded safety counts would require information not reported in the registry record. The findings should not be framed as proof for or against a treatment effect.
13. Why This Trial Matters Statistically
This study illustrates the distinction between a pharmacokinetic description and a clinical treatment comparison. The registered aim is to describe CNS exposure to maraviroc in HIV-1 infected subjects on stable antiretroviral therapy that includes maraviroc at steady state. The primary outcome is a CSF-to-plasma ratio. That focus is different from testing whether one treatment improves a clinical outcome relative to another.
It also highlights the importance of reporting endpoint values, not just endpoint definitions. The registry specifies a mean and full range, but does not report either the numerical mean or the range. Without those values, readers cannot assess the observed level of exposure or its variability. A confidence interval or another precision estimate is also not reported in the registry record, limiting evaluation of how precisely the outcome was estimated.
The record is useful for understanding the design boundaries. It identifies a single-group model, no allocation, and no masking. Those details prevent the study from being mistaken for a randomized controlled comparison. Statistical interpretation depends not only on the endpoint, but also on the structure of the evidence and the comparison the design can support.
Finally, the record demonstrates why denominators and analysis populations need explanation. Enrollment is listed as 13, whereas the safety group lists 12 at risk. The reason for that difference, and the number contributing to the primary endpoint, are not reported in the registry record. Clear participant accounting would help readers understand which observations underlie each result. The listed safety counts can be described, but should not be extended beyond their recorded denominator.
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 most important limitation for interpreting the primary outcome is that its numerical result is not reported in the registry record. Although the endpoint is defined as a CSF-to-plasma ratio summarized by a mean and full range, neither the mean nor the range is available. No confidence interval or other precision measure is reported. The level and variability of CNS exposure therefore cannot be assessed from this record.
The single-group design also limits interpretation. There is no comparator group, allocation is listed as NA, and masking is listed as none. The record supports description of the study objective, but not a randomized comparison or a treatment-effect estimate against another regimen.
Enrollment is reported as 13, while 12 are listed as at risk in the safety group. The registry does not explain this difference or report how many participants contributed to the primary endpoint. Participant flow, analysis-population definitions, and missing-data methods are not reported in the registry record. These omissions make it difficult to assess the population underlying any endpoint summary.
The registry lists zero analyses and does not report the statistical analysis plan, interim analyses, or sample-size justification. The record also does not provide additional measurement details beyond the stated MRS assessment description. The duration and method of safety ascertainment are not reported in the registry record. These limitations concern the information available in the registry record and should not be taken as evidence that the study team did not address them elsewhere.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: The Maraviroc Central Nervous System (CNS) Study — NCT00982878.
- Registry record last updated 2019-11-04; status last verified 2019-10.
- Results first posted 2019-11-04.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
The Maraviroc Central Nervous System Study is a completed Phase I, single-group pharmacokinetic study sponsored by Imperial College London. It enrolled 13 and examined CNS exposure to maraviroc in HIV-1 infected subjects receiving stable antiretroviral therapy that included maraviroc at steady state. Allocation is listed as NA, masking as none, and the primary outcome timeframe as 15 days.
The primary outcome is the CSF-to-plasma ratio of maraviroc, described using a mean and full range and assessed with cerebral 1H magnetic resonance spectroscopy. Its numerical result is not reported in the registry record. The registry lists a secondary adverse-event outcome and zero analyses. Safety fields list 12 at risk, zero affected for serious adverse events, zero affected for other adverse events, and zero deaths. The difference between enrollment and the safety denominator is not explained in the registry record.