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 Study in Healthy Adults to Determine the Effect That Food Has on the Absorption and Delivery of the Drug Cystagon™ (NCT01432561), a na na study. The primary outcome is Cysteamine Absorption: Area Under the Plasma Concentration Curve (AUC).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01432561 |
| Phase | NA |
| Condition | Cystinosis, Nephropathic Cystinosis |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 8 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of California, San Diego |
| Results posted | Yes |
2. Clinical Question
Population
The study enrolled 8 normal, healthy adults. Cystinosis and nephropathic cystinosis are listed as conditions of interest, but the study population is described as healthy adults rather than as people being treated for either condition. The registry record does not report further participant characteristics or eligibility details.
Intervention
Participants received cysteamine bitartrate, listed as 500mg once a day for three days. The study examined absorption under different food conditions: fasted, high-fat, and high-protein. The registry record describes sequences of these conditions across three periods.
Comparator
The comparison of interest is between the food conditions, not between separate drug and placebo groups. Participants were randomized to one of two treatment sequences: fasted, high-fat, then high-protein; or high-protein, high-fat, then fasted. The registry record does not report a separate control arm.
Primary question
Does the presence or type of food relate to the rate or extent of cysteamine absorption, as assessed by the area under the plasma concentration curve? The registry record identifies this as the primary outcome but does not report the outcome values or a comparison between conditions.
3. Trial Design
This was a completed, single-group study with an enrollment of 8. Its purpose was to examine a food effect on the absorption of cysteamine bitartrate in healthy adults. The study record lists no phase, no masking, and allocation as NA. These entries do not describe a conventional parallel-group comparison in which participants are assigned to separate intervention and control arms.
Instead, the record describes two possible sequences of food conditions. One sequence was fasted, high-fat, and high-protein; the other was high-protein, high-fat, and fasted. Block randomization assigned participants to one of these sequences, with sequence determining which condition corresponded to Period I, II, and III. Thus, the sequence assignment is randomized, while the conditions are repeated across periods. The registry record does not report the number assigned to each sequence or how many completed each period.
The intervention is listed as cysteamine bitartrate, 500mg once a day for three days. Further details of dosing by period, the timing or composition of meals, washout intervals, and other procedures are not reported in the registry record. The study started in 2011-09 and had a primary completion date of 2011-12.
The record lists three outcome measures and six analyses, but it does not identify all outcomes or analysis methods in the information available. It also does not report a protocol description of the statistical plan, sample-size justification, interim analyses, or analysis populations. The status is completed, which indicates the registry’s recorded study status; it does not by itself establish that results were posted.
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: Screening for liver function and H pylori infection and brief medical history in order to determine if all inclusion and exclusion criteria were met. One enrollee met all inclusion criteria but clinical lab test revealed presence of H Pylori, an exclusion factor. Two enrollees withdrew from the trial prior to assignment due to scheduling conflicts.
Overall Study
| Stage | Cysteamine Bitartrate |
|---|---|
| STARTED | 8 |
| COMPLETED | 8 |
| NOT COMPLETED | 0 |
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 | Cysteamine Bitartrate |
|---|---|---|
| Participants analysed | 8 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 8 |
| Age, Categorical: >=65 years | Participants | 0 |
| Age Continuous | years | 29.9 (SD 8.5) |
| Sex: Female, Male: Female | Participants | 3 |
| Sex: Female, Male: Male | Participants | 5 |
| Region of Enrollment: United States | participants | 8 |
6. Primary Endpoint
The registry lists the primary outcome as Cysteamine Absorption: Area Under the Plasma Concentration Curve (AUC), measured over 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, 180 minutes, and 3.5, 4, 4.5, 5, 6 hours post-dose.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | min*uM |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is cysteamine absorption measured as the area under the plasma concentration curve (AUC), with units of min*uM. Plasma concentration measurements are listed at times from 0 through 180 minutes after dosing and at 3.5, 4, 4.5, 5, and 6 hours post-dose.
In general, AUC summarizes concentration over time. It is used in pharmacokinetic studies to represent the overall systemic exposure captured during a specified observation period. Comparing AUC across food conditions can address whether the extent of measured exposure differs. It does not, by itself, describe every feature of absorption: for example, concentration at a particular time and the timing of peak concentration are distinct characteristics.
The registry record identifies the endpoint as a mean with standard deviation as the dispersion measure. However, it does not report the mean AUC or standard deviation for any food condition, nor a contrast between conditions. The record therefore states what was intended to be measured, but does not allow the size, direction, or precision of any food-condition difference to be described.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record defines a focused pharmacokinetic question: whether food conditions are associated with differences in cysteamine absorption in healthy adults. The primary endpoint is AUC, measured over a series of post-dose time points. The study uses a sequence design in which the fasted, high-fat, and high-protein conditions are ordered across three periods. The registry description says that participants were randomized to one of two possible sequences.
The outcome information needed to interpret the primary question is not reported in the registry record. There are no condition-specific AUC means or standard deviations, no stated differences between conditions, and no confidence intervals or p-values. Consequently, the direction and magnitude of any observed association, and the precision with which it was estimated, cannot be assessed from the record. No conclusion about whether food changed absorption can be drawn from the design description alone.
The enrollment of 8 describes the number enrolled, not necessarily the number with complete endpoint data. The number contributing measurements in each condition and the extent of missing observations are not reported in the registry record. In a repeated-condition study, those details matter because the comparison may depend on measurements from the same participants across periods. A complete-case comparison and an analysis using available repeated measurements can rely on different data and assumptions.
Random assignment to sequence can help distribute period order across participants, but it does not replace reporting the condition-specific data and the method used to compare conditions. The registry record does not state whether the analysis accounted for sequence, period, or within-participant correlation. These are design features that may be relevant to interpretation, but the analysis cannot be reconstructed from the record.
The adverse-event entry reports 0 participants with a serious adverse event among 8 at risk, and 3 participants with other adverse events among 8 at risk. These counts describe the registry’s recorded safety categories; they do not provide event descriptions for the other adverse events or a comparison across food conditions. The death count is not reported in the registry record.
Overall, the record gives the study question, intended primary measure, enrollment, sequence description, and limited safety counts. It does not provide the primary results required to quantify the food-condition comparison. The appropriate statistical reading is therefore about what the study was designed to examine and what the record does and does not document, rather than about an estimated treatment or food effect.
9. Statistical Methods Explained
In general, a food-effect study asks whether a drug’s measured exposure differs when taken under specified food conditions. Here, the registry record identifies fasted, high-fat, and high-protein conditions and names AUC as the primary measure. The study description indicates that participants were randomized to a sequence of conditions, rather than assigned to separate parallel groups. That distinction matters: repeated measurements from the same participant can be related, so methods for independent groups may not be appropriate without accounting for that dependence.
What does AUC represent?
In general, AUC is an integrated measure of concentration over time. It can represent total measured exposure during the observation window. The registry lists sampling times from 0 to 180 minutes and later measurements through 6 hours post-dose. The endpoint description does not state the precise computational method used to obtain each participant’s AUC. That method is not reported in the registry record.
A mean is a summary of the observed values in a condition, while a standard deviation describes how spread out those values are around the mean. These summaries would help show both the average exposure and the variability among participants. The registry record names mean and standard deviation as the endpoint format, but does not report their values. Without them, a reader cannot assess the observed scale or variability of AUC across conditions.
Why does sequence matter?
In general, sequence randomization assigns participants to different orders of repeated conditions. It can reduce systematic differences in the order in which conditions are received. Still, an analysis may need to consider period effects, sequence effects, and correlation among measurements from the same participant. For example, measurements can be correlated because they come from one person rather than from unrelated people. Whether the study’s analysis addressed these features is not reported in the registry record.
The record says block randomization was used to assign participants to the two possible sequences. It does not report block details, sequence-specific enrollment, or whether the planned analysis included sequence and period. It also does not describe washout intervals or other safeguards against carryover between periods. These omissions do not establish that such procedures were absent; they mean the information is not reported in the registry record.
How should uncertainty be described?
In general, a confidence interval gives a range of values compatible with the data and analysis under its assumptions. Its width communicates statistical precision: a wider interval indicates greater uncertainty about the estimated quantity. A p-value, when reported, addresses how compatible the data are with a specified null hypothesis under the analysis model. Neither measure substitutes for the estimated effect and its clinical or scientific context.
No confidence interval, p-value, or condition contrast is reported for the primary endpoint. There is therefore no basis in the registry record to describe the precision of the estimated food-condition differences or to characterize statistical evidence for a difference. The absence of these results is different from evidence that the conditions produced equal outcomes.
What do planning illustrations mean?
In general, sample-size calculations illustrate how many participants may be needed under specified assumptions about an effect, variability, significance level, allocation, and statistical model. The planning assumptions associated with this study use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They describe an effect to detect as a stated fraction of an observed effect. These assumptions are a planning illustration, not evidence that the trial used that design or that its enrollment was justified by those calculations.
The record’s described study is a single-group, repeated-condition design, and it does not report an observed primary effect. Accordingly, the planning assumptions should not be read as a report of the study’s actual analysis or as observed power. Sample-size calculations are not a substitute for the observed estimate and its uncertainty. The trial’s own sample-size justification is not reported in the registry record.
What does over-dispersion mean in general?
Over-dispersion is a general concern for certain statistical models when observed variability is greater than the model expects. It can make standard errors too small if the extra variability is ignored. The registry record does not report a count outcome as the primary endpoint or identify a model for which over-dispersion was assessed. It also does not report whether the analysis used a parametric, nonparametric, or repeated-measures approach.
These general concepts clarify what information would be useful for interpreting a repeated-condition pharmacokinetic analysis. They do not establish which methods were used in this study. The analysis model, handling of within-participant correlation, treatment of missing measurements, and approach to multiple analyses are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists three outcome measures and six analyses. It does not identify all of these outcomes and analyses in the information available, nor does it report a prespecified strategy for controlling multiplicity. In general, when several outcomes, contrasts, or analyses are examined, the chance of finding an apparently notable result can change. A clear analysis plan can distinguish the primary question from secondary or exploratory questions and specify how multiple comparisons are handled. The registry record does not report such details.
Missing-data methods are also not reported in the registry record. The enrollment is 8, but the number with evaluable AUC measurements in each condition, the number completing all periods, and reasons for missing measurements are not stated. In general, missing observations can affect estimates when the likelihood of being missing is related to participants’ characteristics or outcomes. The extent and handling of missing data are therefore relevant to understanding a repeated-condition comparison.
The analysis populations are not reported in the registry record. It is not stated whether analyses included all enrolled participants, only those completing the sequence, or participants with available measurements for particular conditions. Nor is it stated whether any participants were excluded from analyses or how incomplete records were handled. These points should not be inferred from the completed status or enrollment count.
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 |
|---|---|---|---|
| Cysteamine Bitartrate | 0 | 8 | 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 |
|---|---|
| Cysteamine Bitartrate | 3 of 8 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Cysteamine Bitartrate |
|---|---|---|
| Nausea | Gastrointestinal disorders | 3 of 8 |
| Abdominal pain | Gastrointestinal disorders | 1 of 8 |
The registry record lists 8 participants at risk for serious adverse events and 0 participants affected in that category. It lists 8 participants at risk for other adverse events and 3 affected. These are counts in the Cysteamine Bitartrate group. The record does not provide a comparison between food conditions or a separate control group for these safety figures.
The category “other adverse events” is distinct from serious adverse events. The registry record does not list the specific terms for those other events in the information available. It also does not list any top serious adverse-event terms. The death count is not reported in the registry record, so it should not be read as a reported count of zero.
In general, adverse-event counts describe what was recorded during a study and should be interpreted in relation to the participants observed, the duration and completeness of follow-up, and the event definitions used. Those details are not reported in the registry record. The small enrollment also means that these counts alone cannot characterize uncommon events or establish comparative safety across food conditions.
12. What the Result Does, and Does Not, Mean
The record establishes that a completed study enrolled 8 healthy adults to examine cysteamine absorption under fasted, high-fat, and high-protein conditions. It describes randomization to one of two sequences and identifies AUC as the primary endpoint. Those details clarify the scientific question and the broad structure of the design.
The record does not report the AUC results. Without condition-specific means, variability, or contrasts, the magnitude and direction of the observed differences are unknown. Without confidence intervals or other uncertainty estimates, precision is also unknown. A study description cannot answer whether exposure differed across the conditions, and missing results should not be interpreted as evidence of no difference.
The study population is described as normal, healthy adults. The registry record therefore does not directly provide an estimate in people with cystinosis, despite listing cystinosis and nephropathic cystinosis among the conditions. The purpose described is to investigate absorption, not to report clinical outcomes or treatment benefit. The registry record does not report such clinical outcomes.
The safety figures report 0 serious adverse events among 8 at risk and 3 other adverse events among 8 at risk. They are limited counts from this study and do not provide a comparative estimate across food conditions. The death count is not reported in the registry record.
In short, this record supports a description of the planned pharmacokinetic question, sequence design, endpoint, enrollment, and recorded adverse-event counts. It does not support a quantitative conclusion about the food effect, its precision, or its clinical implications. Those conclusions require outcome data and a transparent account of the analysis.
13. Why This Trial Matters Statistically
This trial is statistically interesting because it frames a food-effect question using repeated conditions within a small group, rather than a simple comparison of separate intervention and control arms. The order of fasted, high-fat, and high-protein conditions was assigned through one of two randomized sequences. That design makes the participant and period structure important: each person’s measurements may be related, and the order of conditions may matter to analysis.
The primary endpoint, AUC, is a continuous measure intended to summarize plasma concentration over time. For this kind of endpoint, interpretation depends on more than a mean alone. Variability, the within-participant pattern, the comparison between conditions, and uncertainty around that comparison all contribute to the statistical account. The registry record specifies mean and standard deviation as the endpoint format but does not report the numerical results or the method used to analyze them.
The record also illustrates a distinction between a study’s design description and its results. Randomization to sequence helps describe how order was assigned, but does not itself reveal the size or precision of a food-condition difference. Likewise, a completed status and an enrollment count do not show how many participants contributed complete measurements or how missing data were addressed.
Finally, the study’s small enrollment makes clear why outcome estimates and uncertainty matter. A count of participants alone cannot establish whether an estimate is stable or how broadly it applies. Because the primary results and analysis details are not reported in the registry record, the statistical contribution that can be assessed is principally the question and design, rather than an estimated food effect.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The main limitation for interpreting this trial from the registry record is that the primary outcome results are not reported. No AUC means, standard deviations, condition contrasts, confidence intervals, or p-values are given. As a result, neither the size nor precision of the food-condition comparison can be evaluated.
The enrollment was 8, and the record does not report how many participants completed all three periods or contributed usable measurements in each condition. Sequence-specific enrollment, missing measurements, and reasons for missingness are also not reported. These details would be important for understanding how much information contributed to the repeated-condition analysis.
The record describes randomization to sequence but does not report the analysis model or whether it accounted for period, sequence, or correlation within participants. Details of meal composition, washout, possible carryover, and the calculation of AUC are not reported in the registry record. Their absence from the record limits assessment of how the measured conditions and comparisons were implemented, but does not establish that procedures were absent.
The participants are described as healthy adults. Findings from this population, if reported, would not by themselves establish results in people with cystinosis. The registry record also does not report the complete outcome set, multiplicity procedures, analysis populations, or the study’s own sample-size justification. These gaps limit assessment of both the analysis and the relevance of any potential finding.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study in Healthy Adults to Determine the Effect That Food Has on the Absorption and Delivery of the Drug Cystagon™ — NCT01432561.
- Registry record last updated 2013-10-09; status last verified 2013-09.
- Results first posted 2013-10-09.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT01432561 is listed as a completed study sponsored by the University of California, San Diego. It enrolled 8 healthy adults and examined cysteamine bitartrate absorption under fasted, high-fat, and high-protein conditions. Participants were randomized to one of two sequences across three periods. The intervention is listed as 500mg once a day for three days.
The primary endpoint was AUC, measured in min*uM, with mean and standard deviation specified. The registry record does not report primary outcome values or the analysis comparing conditions. It lists 0 serious adverse events among 8 at risk, 3 other adverse events among 8 at risk, and does not report the death count. Detailed analysis methods, missing-data handling, and analysis populations are not reported in the registry record.