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 Efficacy and Microfilaricidal Kinetics of Imatinib for the Treatment of Loa Loa (NCT02644525), a randomized phase 2 study. The primary outcome is Percent of Baseline Loa Loa Microfilariae.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02644525 |
| Phase | Phase 2 |
| Condition | Loiasis |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 20 |
| Arms in the primary outcome | n/a |
| Lead sponsor | National Institute of Allergy and Infectious Diseases (NIAID) |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned adults ages 18–65 with non-severe Loa loa infection who were otherwise healthy, as described in the registry record. The trial enrolled 20 participants. The record’s background describes microfilariae in the blood and notes that Loa loa infection can be important when people are treated for other parasitic infections. The posted endpoint concerns measured microfilariae, rather than a patient-reported symptom or a clinical complication.
Intervention
Participants were assigned to single-dose imatinib arms of 200mg, 400mg, or 600mg, taken orally, according to the arm descriptions. This was a dose-escalation study, but the registry record does not report the rules used to move between doses or other dose-escalation procedures.
Comparator
The comparator was placebo, described as a vitamin placebo. The trial was randomized, placebo-controlled, parallel-group, and quadruple-masked. The registry record does not identify who was included in the quadruple masking.
Primary question
The registered primary endpoint was the percent of baseline Loa loa microfilariae, measured by concentrated peripheral blood smear. The endpoint was followed on Days 1–7, 14, and 21. The central question was whether the measured microfilariae changed after imatinib compared with placebo, while examining different imatinib doses and the timing of change. Numerical endpoint results and an analysis comparing the arms are not reported in the registry record.
3. Trial Design
The registry describes a Phase 2, pilot study of imatinib for Loa loa infection. It was randomized, placebo-controlled, quadruple-masked, and used a parallel-group design. Four arms are listed: placebo and single oral doses of imatinib 200mg, 400mg, or 600mg. The record lists enrollment of 20. The adverse-event entries give five participants at risk in each arm. The registry does not give further detail about the randomization procedure, allocation concealment, or the identity of the groups included in quadruple masking.
The primary completion date is recorded as 2020-12-31, and the study status is terminated. The registry record does not report why the study was terminated, whether termination occurred before or after planned completion, or whether the planned enrollment was reached as intended. Those explanations should not be inferred from status alone. The listed sponsor is the National Institute of Allergy and Infectious Diseases (NIAID).
The primary measure was assessed repeatedly: daily during Days 1–7, followed by measurements on Days 14 and 21. The registry notes missing values in two cases, at Day 2 for the Imatinib 200mg arm and Day 7 for the Imatinib 400mg arm. It does not describe the total number of measurements expected, the reasons for missing values, or how those values were handled in analysis.
The record lists one primary outcome measure but no posted analysis results. It therefore gives the broad design and endpoint, but not enough information to reconstruct the analysis plan or determine how the dose groups were compared over time. Statistical methods beyond the outcome’s use of a geometric mean and 95% confidence interval 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.
Group 1
| Stage | Placebo | Imatinib 200mg | Imatinib 400mg | Imatinib 600mg |
|---|---|---|---|---|
| STARTED | 2 | 5 | 0 | 0 |
| COMPLETED | 2 | 5 | 0 | 0 |
| NOT COMPLETED | 0 | 0 | 0 | 0 |
Group 2
| Stage | Placebo | Imatinib 200mg | Imatinib 400mg | Imatinib 600mg |
|---|---|---|---|---|
| STARTED | 2 | 0 | 5 | 0 |
| COMPLETED | 2 | 0 | 5 | 0 |
| NOT COMPLETED | 0 | 0 | 0 | 0 |
Group 3
| Stage | Placebo | Imatinib 200mg | Imatinib 400mg | Imatinib 600mg |
|---|---|---|---|---|
| STARTED | 1 | 0 | 0 | 5 |
| COMPLETED | 1 | 0 | 0 | 5 |
| NOT COMPLETED | 0 | 0 | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: In a two cases (Day 2 for Imatinib 200mg, Day 7 for Imatinib 400mg), some values were missing.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Placebo | Imatinib 200mg | Imatinib 400mg | Imatinib 600mg | Total |
|---|---|---|---|---|---|---|
| Participants analysed | 5 | 5 | 5 | 5 | 20 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 5 | 5 | 5 | 5 | 20 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 | 0 | 0 |
| Age, Continuous | years | 50 (41 to 64) | 51 (32 to 64) | 50 (19 to 65) | 45 (29 to 65) | 49 (19 to 65) |
| Sex: Female, Male: Female | Participants | 1 | 0 | 0 | 2 | 3 |
| Sex: Female, Male: Male | Participants | 4 | 5 | 5 | 3 | 17 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 5 | 5 | 5 | 5 | 20 |
| Race (NIH/OMB): White | Participants | 0 | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 | 0 | 0 |
| Region of Enrollment: Cameroon | participants | 5 | 5 | 5 | 5 | 20 |
| Loa loa mid-day blood microfilariae count | microfilariae/mL | 1447 (520 to 3120) | 1329 (760 to 2340) | 2154 (1000 to 6540) | 1328 (640 to 3060) | 1532 (520 to 6540) |
6. Primary Endpoint
The registry lists the primary outcome as Percent of Baseline Loa Loa Microfilariae, measured over Days 1-7, 14, 21.
| Element | Registry entry |
|---|---|
| Result type | Geometric Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | percentage of baseline microfilariae |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the percent of baseline Loa loa microfilariae, determined from concentrated peripheral blood smears. It is reported as a geometric mean with a 95% confidence interval. Measurements were scheduled during Days 1–7 and again on Days 14 and 21. The registry describes daily measurements during the first week, followed by the later measurements.
Expressing the count as a percentage of baseline frames follow-up measurements relative to the participant’s starting measurement. This can make the amount and timing of change easier to describe across people whose starting microfilariae counts differ. A geometric mean is a summary appropriate to data analyzed on a multiplicative scale; it differs in interpretation from an arithmetic average. These are general statistical explanations, not additional claims about the analysis used in this trial.
The time course matters because the study’s stated objective concerned the kinetics of microfilariae after treatment. Repeated measurements can describe whether the measured endpoint changes soon after dosing and how it looks at later scheduled visits. However, a time series alone does not establish a treatment contrast: interpretation also requires the observed values, uncertainty estimates, and a defined comparison among arms. Those numerical endpoint results and comparisons are not reported in the registry record. The record notes missing values at Day 2 for Imatinib 200mg and Day 7 for Imatinib 400mg, without reporting how they were handled.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the intended endpoint and the basic treatment structure, but it does not provide the numerical primary outcome results. The outcome is percent of baseline Loa loa microfilariae, summarized as a geometric mean with a 95% confidence interval at multiple scheduled times. Without those estimates, it is not possible to describe the observed microfilariae trajectory in any arm, quantify uncertainty around it, or state how the arms compared. No treatment effect estimate or endpoint p-value is reported in the registry record.
The comparison is also not reduced to one contrast. There are three imatinib dose arms and a placebo arm, while the endpoint is measured repeatedly. Different statistical questions could concern a particular dose versus placebo, differences among doses, or variation over time. These are not interchangeable questions. A result at one dose or visit would not, by itself, establish a pattern across all doses and visits. The registry record does not report which contrasts were prespecified or which were used in an analysis.
The posted safety counts are descriptive. The registry records serious adverse events in 0 of 5 participants at risk in the placebo group, 1 of 5 in Imatinib 200mg, 2 of 5 in Imatinib 400mg, and 1 of 5 in Imatinib 600mg. Deaths are recorded as zero in each group. Other adverse events are recorded in 4 of 5 participants at risk for placebo and 5 of 5 in each imatinib arm. These counts do not include enough detail to assess event timing, duration, severity beyond the serious-event classification, or attribution to study treatment. The serious-event term list includes Hypertension, Neutropenia, and Pulmonary embolism, each with a listed percentage of 20.0%; the registry record does not clarify the denominator or how these terms map to individual groups.
Because each listed arm has five participants at risk in the safety entries, the counts are limited in how precisely they describe event occurrence. Small group counts can be compatible with substantial uncertainty, and a difference in observed counts should not be interpreted as a reliable estimate of comparative risk. The record does not report a statistical comparison of adverse events.
The study status is terminated, but the reason and its implications for the endpoint data are not reported in the registry record. Consequently, readers cannot determine from this information whether endpoint follow-up was complete, whether the number of observations matched the plan, or whether termination affected the analysis. The outcome estimates, analysis population, and handling of missing observations are also not reported. These gaps limit interpretation independently of the randomized, masked design.
9. Statistical Methods Explained
What does the geometric mean describe?
A geometric mean summarizes observations using a multiplicative scale rather than adding the values and dividing by their number. It is often useful when measurements are naturally interpreted as relative changes or have a skewed distribution. For an endpoint expressed as a percentage of baseline, this summary describes a typical relative level on the scale used for the analysis. It should not be read as the arithmetic average of individual percentages. This is a general explanation; the registry record does not provide the underlying observations or describe any transformation used to calculate the posted summaries.
How should a confidence interval be read?
A confidence interval communicates uncertainty around an estimated quantity. In general, a narrower interval indicates greater precision for that estimate, while a wider interval indicates less precision. A 95% confidence interval is a frequentist interval procedure: across repeated samples under the method’s assumptions, intervals constructed in this way would contain the target quantity at the stated rate. It is not a guarantee that a particular interval contains the true value with a 95% probability. The registry identifies 95% confidence intervals for the endpoint, but numerical interval bounds are not reported in the registry record, so the precision of the endpoint estimates cannot be assessed.
Why do repeated measurements need careful analysis?
Measurements from the same participant are generally related to one another; they are not independent observations in the way measurements from unrelated participants might be. An analysis of repeated endpoint values should account for that dependence if it estimates an overall time pattern or compares treatment trajectories. Different methods can target different quantities, such as a contrast at a particular visit or an average contrast across visits. Those choices affect interpretation. The registry reports the visit schedule but does not report the statistical model, the target contrast, or whether repeated observations were analyzed jointly.
What does dose escalation contribute?
Including three imatinib dose levels and placebo allows the study to examine more than one dose. In general, an analysis might compare each dose with placebo, assess a dose pattern, or describe each arm separately. Those approaches answer different questions and can involve different uncertainty. The registry record calls this a dose-escalation pilot study, but it does not report a formal dose-response method, the sequence of dose assignment, or rules for escalation. No particular dose-selection procedure should be inferred from the arm labels alone.
Why does multiplicity matter?
When multiple doses, visits, or contrasts are examined, the chance of at least one apparently notable result can increase if each test is treated as a separate unadjusted test. General approaches include defining a primary contrast in advance, controlling an overall error rate, or treating multiple results as exploratory. The registry record does not report whether any multiplicity procedure was planned or applied. With several visits and treatment arms, an isolated result would need to be interpreted in light of the full analysis strategy, which is not reported.
Why does over-dispersion matter?
Over-dispersion occurs when observed variability exceeds what a statistical model assumes. If a model understates variability, confidence intervals can be too narrow and tests can appear more decisive than warranted. This is a general consideration for count data and other variable clinical measurements, not a claim that over-dispersion occurred in this trial. The registry provides no individual measurements, model diagnostics, or description of a variance model, so this issue cannot be evaluated for the posted endpoint.
Overall, the available statistical description is limited to the endpoint definition, its geometric-mean summary, the 95% confidence interval, and the scheduled assessment times. The registry record does not report a statistical analysis plan, model specification, treatment contrasts, p-values, or numerical endpoint estimates. General statistical concepts can help explain what these methods would mean, but they cannot fill in the trial’s unreported analysis details.
10. Multiplicity, Missing Data and Analysis Populations
The primary outcome is one named measure, but it is assessed repeatedly across Days 1–7, 14, and 21 and across four arms. That structure creates multiple possible summaries and comparisons. For example, separate dose-versus-placebo contrasts at different visits answer distinct questions from a single overall comparison of trajectories. The registry record does not report a prespecified primary contrast, an approach to multiplicity, or whether any adjustment was applied. It would therefore be inappropriate to assume that reported tests controlled a family-wise error rate or that one visit was designated as the sole inferential focus.
Missing values are noted in two cases: Day 2 for Imatinib 200mg and Day 7 for Imatinib 400mg. The registry does not report why these observations were missing, whether other endpoint observations were missing, or whether the analysis used complete cases, imputation, a repeated-measures model, or another method. Missing-data methods rely on assumptions about why values are absent; the choice can affect estimates and uncertainty. Without the method and supporting information, the consequences of the missing values cannot be assessed.
The analysis populations are not reported in the registry record. It is therefore unclear whether the endpoint analysis included all randomized participants, only participants with observed measurements, or another defined group. The record also does not report exclusions, protocol deviations, or the number contributing data at each visit. These omissions limit assessment of whether the analysis preserved the randomized comparison and how representative the analyzed observations were of those enrolled.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Placebo | 0 | 5 | 0.0% |
| Imatinib 200mg | 1 | 5 | 20.0% |
| Imatinib 400mg | 2 | 5 | 40.0% |
| Imatinib 600mg | 1 | 5 | 20.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Placebo | 0 of 5 |
| Imatinib 200mg | 0 of 5 |
| Imatinib 400mg | 0 of 5 |
| Imatinib 600mg | 0 of 5 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Placebo | 4 of 5 |
| Imatinib 200mg | 5 of 5 |
| Imatinib 400mg | 5 of 5 |
| Imatinib 600mg | 5 of 5 |
Most frequent serious adverse event terms
| Event term | Organ system | Placebo | Imatinib 200mg | Imatinib 400mg | Imatinib 600mg |
|---|---|---|---|---|---|
| Neutropenia | Immune system disorders | 0 of 5 | 1 of 5 | 1 of 5 | 0 of 5 |
| Hypertension | Cardiac disorders | 0 of 5 | 0 of 5 | 0 of 5 | 1 of 5 |
| Pulmonary embolism | Blood and lymphatic system disorders | 0 of 5 | 0 of 5 | 1 of 5 | 0 of 5 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Placebo | Imatinib 200mg | Imatinib 400mg | Imatinib 600mg |
|---|---|---|---|---|---|
| Neutrophil count decreased | Blood and lymphatic system disorders | 2 of 5 | 4 of 5 | 3 of 5 | 3 of 5 |
| Hypertension | Cardiac disorders | 2 of 5 | 3 of 5 | 3 of 5 | 1 of 5 |
| Anemia | Blood and lymphatic system disorders | 1 of 5 | 2 of 5 | 2 of 5 | 3 of 5 |
| Aspartate aminotransferase increased | Hepatobiliary disorders | 4 of 5 | 2 of 5 | 1 of 5 | 1 of 5 |
| Headache | General disorders | 2 of 5 | 1 of 5 | 2 of 5 | 0 of 5 |
| Alkaline phosphatase increased | Hepatobiliary disorders | 1 of 5 | 0 of 5 | 1 of 5 | 2 of 5 |
| Arthralgia | Musculoskeletal and connective tissue disorders | 1 of 5 | 2 of 5 | 0 of 5 | 1 of 5 |
| Fatigue | General disorders | 2 of 5 | 2 of 5 | 0 of 5 | 0 of 5 |
| Lymphocyte count increased | Blood and lymphatic system disorders | 1 of 5 | 1 of 5 | 2 of 5 | 0 of 5 |
| Myalgia | Musculoskeletal and connective tissue disorders | 1 of 5 | 2 of 5 | 1 of 5 | 0 of 5 |
Serious events with the highest arm-level rate: hypertension (20.0%), neutropenia (20.0%), pulmonary embolism (20.0%).
The registry records serious adverse events among five participants at risk in each group: 0 in placebo, 1 in Imatinib 200mg, 2 in Imatinib 400mg, and 1 in Imatinib 600mg. It records other adverse events in 4 participants in the placebo group and 5 participants in each imatinib group, with five at risk in every group. Deaths are recorded as zero in all four groups.
These are participant counts, not estimates adjusted for time at risk or other factors. With only five participants at risk per group, the counts describe what was recorded in this small study but provide limited precision for comparing groups. They do not establish that an event was caused by the study drug, nor do they establish the absence of risk when no serious event was recorded in a group.
The registry lists Hypertension, Neutropenia, and Pulmonary embolism among the top serious-event terms, each at 20.0%. The record does not clarify the denominator for those percentages or connect each term to a particular arm. No broader event narratives, timing, or statistical comparison are reported.
12. What the Result Does, and Does Not, Mean
The record describes a randomized, placebo-controlled pilot study designed to examine imatinib dose levels and the timing of changes in Loa loa microfilariae. It defines a repeated-measures primary endpoint and lists four study arms. Those design details explain what the study set out to examine, but they do not establish what the outcome was. Numerical endpoint values and confidence intervals are not reported in the registry record, so neither the direction nor size of any observed change can be described.
The safety entries report serious-event counts, other-event counts, and zero deaths in each arm. These are descriptive records from five participants at risk per arm. They are not, on their own, a precise comparison of safety between treatments, and they do not establish causation. The serious-event term percentages lack a reported denominator in the registry record, further limiting their interpretation.
The study’s terminated status also needs to be kept separate from an outcome conclusion. The reason for termination is not reported in the registry record. It does not show, by itself, whether the study stopped early, whether planned observations were completed, or what effect termination had on the analysis.
Accordingly, the registry information supports a description of the research question, design, endpoint schedule, and recorded safety counts. It does not support a conclusion about the efficacy of imatinib, the comparative effect of any dose, or the precision of a treatment effect. Such conclusions would require the endpoint results and analysis details, which are not reported in the registry record. This distinction is especially important for a pilot study: its design may generate information about feasibility or patterns, but the record’s available outcome information does not permit those patterns to be evaluated statistically.
13. Why This Trial Matters Statistically
This trial is statistically interesting because its question combines dose variation with a changing biological measurement over time. The four-arm design includes placebo and three imatinib doses, while the endpoint is scheduled repeatedly during the first week and at later visits. A suitable analysis must distinguish treatment differences from changes over time and account for the fact that repeated measurements come from the same participants. The registry record identifies the ingredients of that problem, but does not report how it was addressed analytically.
The endpoint is expressed as a percentage of baseline and summarized by a geometric mean with a 95% confidence interval. That choice highlights relative change and uncertainty rather than a single raw count at one visit. It also makes it important to know how the endpoint values were distributed and how the analysis handled within-participant dependence. The underlying observations, model, and numerical estimates are not reported in the registry record, so these methodological choices cannot be assessed beyond the registered description.
The safety information illustrates a separate statistical issue: sparse group counts. Five participants were at risk in each arm, so a small change in the count corresponds to a potentially substantial change in the apparent proportion. Descriptive counts remain useful for understanding what was recorded, but they should not be mistaken for precise comparative risk estimates.
Finally, the design has several possible comparisons, including multiple doses and time points. Prespecification and transparent reporting of contrasts and multiplicity handling are important for interpreting such results. Those details and the primary endpoint analyses are not reported in the registry record. The study therefore provides a clear example of why a registered design and outcome definition are not substitutes for complete statistical results.
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 largest limitation for interpretation is that numerical results for the primary endpoint are not reported in the registry record. Although the outcome, summary measure, confidence interval type, and schedule are identified, the recorded information does not give arm-specific endpoint values, confidence limits, or treatment comparisons. This prevents assessment of the size, direction, and precision of any observed change.
The design includes multiple dose arms and repeated measurements, but the analysis plan is not reported. The record does not identify the primary contrast, statistical model, multiplicity strategy, or analysis population. It also does not explain how repeated observations from a participant were handled. These omissions make it impossible to reconstruct the intended inferential approach or assess whether the reported analysis, if any, matched it.
The record notes missing endpoint values at Day 2 for Imatinib 200mg and Day 7 for Imatinib 400mg, but not their reasons or treatment in analysis. The extent of missingness at other visits is not reported. Without this information, the potential influence of missing data is unclear.
Safety counts are based on five participants at risk in each arm, which limits the precision of comparisons. The registry does not report event timing, participant-level detail, causality assessments, or statistical comparisons. It also lists serious-event terms with percentages but does not clarify their denominator or arm assignment. The study is marked terminated, while the reason and consequences for data collection are not reported. These limitations prevent stronger conclusions about either the endpoint or safety.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Efficacy and Microfilaricidal Kinetics of Imatinib for the Treatment of Loa Loa — NCT02644525.
- Registry record last updated 2022-06-07; status last verified 2021-03.
- Results first posted 2022-06-07.
- 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 registry describes a Phase 2 randomized, placebo-controlled, quadruple-masked, parallel-group pilot study of imatinib for Loa loa infection. Enrollment is listed as 20, with placebo and imatinib 200mg, 400mg, and 600mg arms. The primary endpoint is percent of baseline Loa loa microfilariae, summarized by geometric mean with a 95% confidence interval and assessed during Days 1–7, 14, and 21.
The study status is terminated, and the primary completion date is 2020-12-31. The registry notes missing endpoint values at Day 2 for Imatinib 200mg and Day 7 for Imatinib 400mg. Safety entries list five participants at risk in each arm, serious and other adverse-event counts, and zero deaths in every group.
Numerical primary endpoint estimates, treatment comparisons, analysis methods, analysis populations, missing-data handling, and the reason for termination are not reported in the registry record. The available record therefore describes the study design and selected safety counts but does not establish the primary outcome results.