Pharmacokinetics of Oral Hydroxyurea Solution: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pharmacokinetics of Oral Hydroxyurea Solution (NCT03763656), a na phase 1, phase 2 study. The primary outcome is Clearance (CL/F).

2. Clinical Question

In practical terms, the study asks how oral hydroxyurea solution is handled over time in the population represented by the pharmacokinetic analysis. Clearance is a pharmacokinetic quantity, not a direct measure of a clinical outcome such as a change in symptoms or disease events. The registry also lists adverse events and laboratory measures as secondary outcomes, including blood counts, bilirubin, hematocrit, and liver function tests. The posted information does not include numerical results for those secondary outcomes. Since there is no concurrent control group, the study description alone cannot separate changes during treatment from changes that might occur over time for other reasons.

3. Trial Design

This was a prospective, open-label, single-group study of an oral hydroxyurea solution. The registry lists the phases as Phase 1 and Phase 2, the study status as completed, and enrollment as 33. Nova Laboratories Limited is listed as the sponsor. The record gives a start date of 2019-01-03 and a primary completion date of 2021-05-19. Those dates describe the registry record and do not, by themselves, establish when all analyses or reporting were completed.

The study treatment was oral hydroxyurea solution at 100 mg/mL. The study summary describes participants from 6 months to 17.99 years of age and a planned treatment period of 12 to 15 months for each participant. It states that treatment at the maximum tolerated dose would last 6 months, with that dose usually reached by 6 months after treatment initiation. For participants whose time to maximum tolerated dose was longer, or who did not reach it, the maximum study-treatment duration was 15 months. These are features described in the registry summary; further protocol details are not reported in the registry record.

Masking is listed as none, and allocation is listed as NA. The arm is named Open Label and is described as the novel oral solution formulation of hydroxyurea. There is no like-for-like control arm, so comparisons between treated and untreated groups are not available from this design. The primary pharmacokinetic population is described as n=32 participants who had received at least one dose of study drug. This differs from the overall enrollment of 33; the reason for the difference is not reported in the registry record. A sample-size justification, detailed statistical analysis plan, and information about interim analyses are not reported in the registry record.

4. Participant Flow and Accounting

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

Before assignment: 33 participants enrolled met the inclusion criteria; 32 initiated treatment with open label Hydroxyurea and one participant discontinued pre-treatment.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Clearance value for patient of 15.05 kg

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: Participant demographics were summarized for all 33 participants. One participant discontinued prior to receiving a first dose of IMP. The remaining safety population consisted of 32 participants who all received at least one dose of the IMP and one valid primary efficacy PK measurement. This safety population was used for all analyses of baseline characteristics, secondary and exploratory outcomes, as well as safety outcomes.

6. Primary Endpoint

The registry lists the primary outcome as Clearance (CL/F), measured over 0, 0.25, 0.5, 1, 1.5, 2, 3, 4, 5, 6, and 12 hours post-dose on Day 1 and Day 2 (Week 20-36).

The primary endpoint is clearance (CL/F), expressed in L/hr. The registry describes it as a model-estimated pharmacokinetic parameter, reported as a mean with a 95% confidence interval. The specified population is a patient of 15.05 kg, and the endpoint description identifies the pharmacokinetic population as n=32 participants who received at least one dose of study drug. The listed sampling timeframe includes 0, 0.25, 0.5, 1, 1.5, 2, 3, 4, 5, 6, and 12 hours post-dose on Day 1 and Day 2 during Week 20-36.

In general, clearance describes how quickly a drug is removed from the body, relative to its concentration. For a drug taken by mouth, CL/F is apparent clearance: F denotes bioavailability, so the estimate reflects clearance in relation to the fraction of the administered dose that reaches the circulation. This is why the endpoint is useful in a pharmacokinetic study: it summarizes drug disposition rather than directly measuring a clinical benefit or harm.

The registry specifies a model-estimated mean and confidence interval, but the numerical estimate and confidence interval bounds are not reported in the registry record. The modeling approach, its assumptions, and the details of how the estimate was derived are also not reported in the registry record. Therefore, the endpoint’s definition and intended interpretation can be described, but its magnitude and precision cannot be assessed from the information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary outcome as a model-estimated mean for clearance (CL/F), with a 95% confidence interval. It does not report the numerical mean, interval bounds, or modeling details. The concepts below are general explanations of how these statistical quantities are usually read; they do not establish which specific modeling decisions were made in this study.

What does a mean represent?

In general, a mean summarizes the central level of a continuous measurement across the observations included in an analysis. Here, the registry identifies clearance as the continuous measure and gives a model-estimated mean for a patient of 15.05 kg. A model-estimated mean is not necessarily the same as a simple arithmetic average of individual observed values: its interpretation depends on the model and the data used. The model specification and estimation procedure are not reported in the registry record, so it is not possible to determine precisely how the reported mean would relate to individual measurements.

The registry describes the endpoint population as n=32 participants who had received at least one dose of study drug. That tells readers which population is named for the pharmacokinetic endpoint, but it does not explain how participants were selected for the model or whether all planned measurements were available for each person. Those details are not reported in the registry record. The endpoint also specifies a patient of 15.05 kg. This anchors the stated estimate to the particular population value in the endpoint description; it should not be silently treated as an estimate for every age or body size represented in the study.

How should a confidence interval be read?

In general, a confidence interval communicates uncertainty around an estimate. A narrower interval indicates greater precision under the statistical model and assumptions used; a wider interval indicates less precision. It is not a range containing every participant’s value, and it is not a guarantee that the true value lies within the reported interval. The registry identifies a 95% confidence interval, but its bounds are not reported in the registry record. As a result, the precision of the clearance estimate cannot be evaluated from the information. The meaning of the interval also depends on the model and its assumptions, which are not described in the registry record.

What does CL/F mean?

In general pharmacokinetic notation, clearance describes drug removal relative to concentration, while F denotes bioavailability. For an oral dose, apparent clearance, CL/F, reflects clearance adjusted for the fraction of the dose that becomes available in the circulation. This is a useful summary for describing drug disposition after oral administration. It is not a direct measure of whether a treatment improves a clinical outcome. The registry reports the endpoint unit as L/hr and identifies post-dose sampling times on Day 1 and Day 2 during Week 20-36. The specific pharmacokinetic model, its parameterization, and the handling of concentrations below measurable levels are not reported in the registry record.

Why does over-dispersion matter in general?

For count outcomes, over-dispersion means that variability is greater than a statistical model’s basic assumptions would predict. If present, it can affect standard errors and confidence intervals, so an analysis may need a method that accommodates the extra variability. This is a general statistical point, not a claim about this study. The primary endpoint is a continuous pharmacokinetic measure, and the registry does not report whether over-dispersion was assessed or relevant to any secondary count analyses.

What is the role of the post-dose sampling schedule?

In general, measurements at multiple times after a dose can help characterize how drug concentrations change over time and can inform pharmacokinetic parameter estimates. The registry lists times from 0 through 12 hours after dosing on Day 1 and Day 2 during Week 20-36. This schedule is part of the endpoint description, but it does not reveal the observed concentration profile. The concentration data, individual profiles, model diagnostics, and the method used to handle missing time points are not reported in the registry record. No additional result should be inferred from the sampling schedule alone.

What can planning calculations tell readers?

In general, a sample-size calculation asks how many participants would be needed for a specified design to detect a specified effect under stated assumptions. Any such calculation is conditional on those assumptions and is not evidence about what the study actually observed. The planning illustration is described as using a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. For time-to-event tables it reports total events; for other tables it reports participants per arm. Those are illustration assumptions, not the trial’s own design: this study is single-group and has no like-for-like randomized comparator. The study’s own sample-size justification is not reported in the registry record. Planning illustrations must not be read as observed power or as a substitute for the missing endpoint estimate and interval.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 32 outcome measures and 0 analyses. It names the primary clearance endpoint and several secondary outcomes, including adverse events, blood counts, platelets, mean corpuscular hemoglobin, hematocrit, bilirubin, and elevation in liver function tests. The available record does not explain how these outcomes were prioritized beyond identifying the primary endpoint, or how multiple statistical comparisons were handled. A multiplicity adjustment or prespecified hierarchy is not reported in the registry record. The absence of a listed analysis is not evidence that a particular method was or was not used outside the registry entry.

Missing-data methods are not reported in the registry record. The record does not describe how missing pharmacokinetic samples, incomplete follow-up, or unavailable laboratory measurements were handled. It also does not state whether any sensitivity analyses assessed the effect of missing observations. The endpoint population is described as n=32 participants who received at least one dose, while enrollment is 33; the reason for the difference is not reported in the registry record. It would be inappropriate to infer why the population differs or what happened to any participant from that difference alone.

The primary outcome specifies a pharmacokinetic population, but definitions for analysis populations for secondary outcomes are not reported in the registry record. The available information does not state whether safety analyses included all participants who received treatment, how exposure was defined, or whether other populations were used. Interim analyses and the statistical analysis plan are also not reported in the registry record. These gaps matter because analysis choices can affect which participants and measurements contribute to each result, and how uncertainty across multiple outcomes is presented. Readers should therefore distinguish the endpoint definition and broad counts that are available from unreported analysis procedures.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: acute chest syndrome (acs) grade 3 (9.4%), vaso-occlusive crisis (voc) (6.2%), acute chest syndrome (acs) grade 2 (3.1%), anemia secondary to scd (3.1%).

The registry lists 32 participants at risk for the oral hydroxyurea group. It records serious adverse events affecting 6 participants, other adverse events affecting 31 participants, and 0 deaths. These are broad participant counts; they do not say how many events occurred, how long events lasted, or when they occurred. The registry also lists selected serious-event terms with percentages: Acute Chest Syndrome (ACS) Grade 3, 9.4%; Vaso-occlusive Crisis (VOC), 6.2%; Acute Chest Syndrome (ACS) Grade 2, 3.1%; and Anemia secondary to SCD, 3.1%. Counts for those individual terms are not reported in the registry record.

These figures are descriptive safety summaries from a single-group, open-label study. They are not comparative risk estimates, because there is no separate control group. The record does not give details about event severity definitions beyond the terms shown, timing, recurrence, attribution to study treatment, resolution, or exposure-adjusted rates. The percentages for selected terms should therefore be read as the registry’s listed summaries, not as evidence that one event type was more or less likely than another. The counts also do not establish whether an event was caused by treatment. The broader list of secondary safety and laboratory outcomes does not include numerical results in the information.

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

This study is described as a prospective, open-label investigation of oral hydroxyurea solution in children, with a primary pharmacokinetic endpoint of model-estimated clearance. The registry provides the endpoint definition, the stated pharmacokinetic population, and the sampling schedule. It does not report the numerical clearance estimate or the bounds of its 95% confidence interval. Those missing results prevent assessment of the estimate’s magnitude and precision. The study description and endpoint definition should not be mistaken for a numerical finding.

The design is single-group, with allocation listed as NA and masking listed as none. It therefore does not provide a randomized comparison against another treatment or a control condition. Even if measurements changed during the study, a single-group design cannot by itself distinguish treatment-related change from other time-related or participant-related influences. The record also does not report enough detail about the pharmacokinetic model or measurement completeness to assess those aspects of the analysis.

The safety summary records 6 participants affected by serious adverse events, 31 affected by other adverse events, and 0 deaths, among 32 listed at risk. Selected serious-event terms are reported with percentages. These are descriptions of events recorded in this study, not evidence of comparative safety or causation. The registry does not include the detail needed to interpret timing, recurrence, attribution, or exposure-adjusted rates. Numerical results for the listed secondary laboratory outcomes are not reported in the registry record.

More generally, this study can contribute a description of pharmacokinetics and safety observations in its enrolled group, subject to the information actually reported. It cannot, on the available registry information, establish a treatment effect relative to a comparator or support a precise interpretation of the primary clearance result. A planning illustration elsewhere on the page is not a result from participants and is not observed power. Readers should treat the page as a guide to the design, endpoint, and limits of the posted results rather than as a basis for treatment decisions.

13. Why This Trial Matters Statistically

The study is statistically notable for centering its primary outcome on pharmacokinetics rather than a direct clinical event. Clearance is a continuous measure intended to summarize drug disposition, and the registry specifies a model-estimated mean with a 95% confidence interval. This makes the estimate’s precision important: an estimate without its interval cannot be judged for uncertainty. In this record, the endpoint definition is available, but the numerical estimate and interval bounds are not reported in the registry record.

The study also illustrates the distinction between enrollment and an endpoint-specific analysis population. Enrollment is 33, while the pharmacokinetic population is n=32 participants who received at least one dose. The registry states both figures, but not why they differ. This is a reminder to identify the population behind each result rather than assume every outcome uses the same participants. The analysis populations for secondary outcomes are not reported in the registry record.

Its single-group, open-label structure sets clear limits on statistical comparisons. There is no randomized control group, and allocation is listed as NA. A reader can describe what was recorded in this group, but cannot interpret the data as a randomized estimate of differences between treatment strategies. The broad safety counts are useful descriptions, while the absence of a control group and further event detail restrict comparative interpretation.

Finally, the registry lists many outcome measures but 0 analyses. This makes it especially important to separate listed outcomes from results and to avoid assuming that unreported multiplicity, missing-data, or model procedures followed a particular approach. Planning illustrations can explain how assumed effects and designs relate to hypothetical sample sizes, but they do not recover unreported findings or describe the trial’s own design. The statistical value of the record is therefore partly in clarifying what was planned and measured, and partly in making visible which conclusions remain unavailable.

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 trial-specific limitation is the lack of a numerical primary endpoint result in the registry information. Although clearance is defined as a model-estimated mean with a 95% confidence interval, neither the estimate nor interval bounds are reported in the registry record. The model and its diagnostics are also not described. Readers therefore cannot evaluate the result’s size, precision, or robustness.

The single-group, open-label design has no concurrent comparator, so it cannot support a randomized between-group estimate. Allocation is listed as NA and masking as none. The registry does not report a detailed protocol or statistical analysis plan, so it is not possible to verify further design or analysis choices. The age range in the study summary is broad, but the actual age distribution and the number of participants in each listed condition are not reported in the registry record. The clearance endpoint is specified for a patient of 15.05 kg, limiting interpretation to the stated endpoint definition rather than establishing how estimates vary across body sizes.

Enrollment is 33, while the endpoint population is n=32. The reason for this difference and the handling of any missing pharmacokinetic observations are not reported in the registry record. The record also does not report the analysis populations or missing-data methods for secondary outcomes. Although 32 outcome measures and several safety outcomes are listed, numerical results for the secondary laboratory outcomes are not present in the information.

The serious-event summary gives broad counts and selected terms, but not timing, recurrence, attribution, event duration, or exposure-adjusted rates. These gaps limit detailed safety interpretation, particularly in a study without a comparator. A sample-size justification, interim analyses, multiplicity approach, and full statistical methods are not reported in the registry record. These limitations concern the available design and reporting information; they do not establish that unreported procedures were not carried out.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Pharmacokinetics of Oral Hydroxyurea Solution — NCT03763656.
• Registry record last updated 2024-10-28; status last verified 2024-08.
• Results first posted 2024-10-28.
• 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

The registry record describes NCT03763656, Pharmacokinetics of Oral Hydroxyurea Solution, as a completed Phase 1 and Phase 2 prospective, open-label, single-group study. It lists enrollment of 33, sponsor Nova Laboratories Limited, and an intervention of oral hydroxyurea solution at 100 mg/mL. The study summary describes children from 6 months to 17.99 years and a treatment period of 12 to 15 months.

The primary outcome is model-estimated clearance (CL/F), reported as a mean with a 95% confidence interval for a patient of 15.05 kg. The endpoint population is n=32 participants who received at least one dose. The numerical estimate and interval bounds are not reported in the registry record. The record lists 32 outcome measures and 0 analyses.

For safety, 6 of 32 participants are listed as affected by serious adverse events, 31 of 32 by other adverse events, and deaths as 0. The design has no comparator group. Details about the analysis plan, missing-data handling, and the reason the endpoint population differs from enrollment are not reported in the registry record.