This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for A Study to Evaluate the Efficacy and Safety of Oxabact in Patients With Primary Hyperoxaluria (NCT03116685), a randomized phase 3 study. The primary outcome is Change From Baseline in Plasma Oxalate Concentration After 52 Weeks of Treatment.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03116685 |
| Phase | Phase 3 |
| Condition | Primary Hyperoxaluria |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 25 |
| Arms in the primary outcome | n/a |
| Lead sponsor | OxThera |
| Results posted | Yes |
2. Clinical Question
Population
Patients with primary hyperoxaluria were eligible for this study. The registry record gives enrollment as 25. The primary endpoint description specifies a full analysis set, but further eligibility criteria and the number of participants included in that analysis are not reported in the registry record.
Intervention
Oxabact OC5 capsules, described as Oxabact OC5 - Oxalobacter formigenes HC-1. The study evaluated the intervention over 52 weeks for its primary endpoint.
Comparator
Placebo capsules. The record describes randomized allocation and a parallel-group design; it does not provide further details about allocation procedures or the masking roles.
Primary question
What was the change from baseline in mean plasma oxalate concentration after 52 weeks of treatment, and how did the outcome compare between the Oxabact OC5 and placebo groups? The registry record identifies this endpoint but does not report the numerical results needed to answer the comparison.
The endpoint concerns total plasma oxalate concentration, measured in micromole/liter. It is a continuous measure, and the planned summary is the mean change from baseline. The record lists kidney function change and frequency of kidney stone events as secondary outcomes, but it does not provide numerical results for those outcomes either.
The study is registered as completed, with enrollment of 25. Completion and enrollment describe the conduct of the study; they do not establish what the treatment comparison found. Without group-level estimates and their uncertainty, the direction, size, and precision of the primary comparison cannot be assessed from the registry record.
3. Trial Design
This is a Phase III, randomized, parallel-group study comparing Oxabact OC5 capsules with placebo capsules in patients with primary hyperoxaluria. The record describes quadruple masking. It does not specify which people involved in the study were masked, how the randomization sequence was generated, or how allocation was concealed; those details are not reported in the registry record.
The study is listed as completed. Enrollment was 25, the recorded start date was 2018-01-09, and primary completion was 2021-04-15. These are registry entries, not evidence about the size or precision of the treatment effect. The record gives no numerical group results for the primary endpoint, and it reports no analysis entries.
The primary endpoint was change from baseline in total plasma oxalate concentration after 52 weeks of treatment. It was defined as a mean change, with standard deviation as the dispersion measure and micromole/liter as the unit. The primary analysis population is described as the full analysis set. A mixed repeated measures model for change is named in the endpoint description as the approach used for missing data.
The registry lists change from baseline in kidney function and frequency of kidney stone events as secondary outcomes. It also reports three outcome measures, but the numerical results and detailed analysis methods for those measures are not reported in the registry record. The record does not describe a sample-size justification, planned interim analyses, or a detailed statistical analysis plan.
Randomization and masking are design features intended to reduce bias in treatment comparisons. In general, randomization helps balance measured and unmeasured characteristics across groups on average, while masking can limit influences on care, assessment, and reporting. These design features do not replace outcome estimates: the numerical results and their uncertainty are needed to assess what the trial observed.
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 | Oxabact OC5 Capsules | Placebo Capsules |
|---|---|---|
| STARTED | 13 | 12 |
| COMPLETED | 13 | 11 |
| NOT COMPLETED | 0 | 1 |
Reasons for not completing this period:
| Reason | Oxabact OC5 Capsules | Placebo Capsules |
|---|---|---|
| Physician Decision | 0 | 1 |
Analysis population for the primary outcome, as defined in the registry: Full analysis set using a mixed repeated measures model for change for missing data
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 | Oxabact OC5 Capsules | Placebo Capsules | Total |
|---|---|---|---|---|
| Participants analysed | 13 | 12 | 25 | |
| Age, Categorical: <=18 years | Participants | 10 | 8 | 18 |
| Age, Categorical: Between 18 and 65 years | Participants | 3 | 4 | 7 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Age, Continuous | years | 12.9 (SD 6.4) | 18.3 (SD 16.5) | 15.5 (SD 12.4) |
| Sex: Female, Male: Female | Participants | 9 | 5 | 14 |
| Sex: Female, Male: Male | Participants | 4 | 7 | 11 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 1 | 0 | 1 |
| Race (NIH/OMB): White | Participants | 12 | 12 | 24 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: Belgium | participants | 1 | 2 | 3 |
| Region of Enrollment: United States | participants | 0 | 1 | 1 |
| Region of Enrollment: United Kingdom | participants | 1 | 2 | 3 |
| Region of Enrollment: Tunisia | participants | 3 | 1 | 4 |
| Region of Enrollment: Germany | participants | 2 | 4 | 6 |
| Region of Enrollment: Spain | participants | 6 | 2 | 8 |
| Primary Hyperoxaluria Type: PH Type I | Participants | 13 | 11 | 24 |
| Primary Hyperoxaluria Type: PH Type II | Participants | 0 | 1 | 1 |
| Stage of Chronic Kidney Disease: Stage I | Participants | 1 | 2 | 3 |
| Stage of Chronic Kidney Disease: Stage II | Participants | 11 | 5 | 16 |
| Stage of Chronic Kidney Disease: Stage III | Participants | 1 | 5 | 6 |
6. Primary Endpoint
The registry lists the primary outcome as Change From Baseline in Plasma Oxalate Concentration After 52 Weeks of Treatment, measured over 52 weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | micromole/liter |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is change from baseline in total plasma oxalate concentration after 52 weeks of treatment. It is a continuous laboratory measure reported in micromole/liter. The registry specifies the mean as the summary measure and standard deviation as the measure of dispersion. The endpoint description identifies the full analysis set and a mixed repeated measures model for change for missing data.
Change from baseline expresses the endpoint relative to each participant's starting measurement rather than describing only the later measurement. In general, a baseline-referenced outcome can account for differences in starting values when treatment groups are compared. The mean describes the average change within a group; the standard deviation describes how spread out individual changes are around that average. Neither measure alone establishes how precisely the between-group contrast has been estimated.
Plasma oxalate concentration is the selected primary measure in this study of primary hyperoxaluria. The registry record names the endpoint but does not report the group means, standard deviations, treatment contrast, confidence interval, or test result. Thus, the magnitude and precision of the observed comparison cannot be evaluated from the record.
The 52-week timeframe is the assessment point specified for the primary endpoint. The record does not provide more detail about measurement schedules, laboratory procedures, or how endpoint data were summarized at other time points. A clinical interpretation should therefore remain tied to the defined measure and timeframe, without treating it as a direct measure of every aspect of the condition.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a randomized comparison of Oxabact OC5 and placebo, with change from baseline in plasma oxalate concentration after 52 weeks as the primary endpoint. It does not report the numerical primary-outcome results. In particular, the record contains no group estimates, treatment contrast, confidence interval, or p-value for this endpoint. The efficacy comparison therefore cannot be characterized by direction, magnitude, or statistical precision from the registry record.
This absence matters because an endpoint definition is not an outcome result. Knowing the measure, unit, timeframe, and planned summary does not reveal whether the observed group averages differed, how large any difference was, or how variable the measurements were. The record's description of the analysis population and missing-data approach likewise does not supply the estimated treatment effect.
Three outcome measures are listed, and the registry names kidney function change and frequency of kidney stone events as secondary outcomes. Numerical results for these outcomes are not reported in the registry record. The registry also indicates that the primary outcome has several categories or time points and is not reduced to one comparison. The record does not specify those categories or time points in the posted results, so a single effect estimate cannot be presented from this information.
For any treatment comparison, a confidence interval would describe the range of values compatible with the data and model under the stated analysis. A narrow interval would indicate greater precision than a wide one, while neither width nor statistical significance alone establishes clinical importance. These are general statistical principles; no interval or p-value for the primary outcome is reported in the registry record.
The study's enrollment of 25 and its completed status do not answer the efficacy question. Enrollment is not a substitute for the number analyzed, and the record does not give the primary analysis count. Nor can the result be inferred from the study design or from adverse-event counts. The record describes the comparison that was planned and provides some safety counts, but without numerical primary efficacy results, no conclusion about the comparative plasma oxalate outcome can be drawn from the posted results.
Any interpretation should also distinguish the intended model-based analysis from a simple comparison of raw summaries. The endpoint description names a mixed repeated measures model for change in the full analysis set. Model estimates can depend on the data included and assumptions used to address missing measurements. Further model specifications and diagnostics are not reported in the registry record, so the analysis cannot be independently reconstructed from this information.
9. Statistical Methods Explained
The record describes a randomized, parallel-group design with quadruple masking. Randomization is a method for assigning participants to groups by chance. In general, it aims to make the groups comparable at the start of a trial, although chance imbalances can still occur, especially in a small study. Masking is intended to reduce the possibility that knowledge of treatment assignment influences participant behavior, care, outcome assessment, or reporting. The record does not explain the specific randomization procedure or which roles were masked.
What does the endpoint summary represent?
The primary outcome is continuous: change from baseline in plasma oxalate concentration after 52 weeks. The registry specifies a mean and standard deviation. The mean is the arithmetic average of participants' changes in a group. The standard deviation describes the spread of those changes around the group mean; it is not the uncertainty of the mean or of the treatment contrast. In general, uncertainty about a group comparison is conveyed by a standard error or confidence interval, neither of which is reported for this endpoint.
A treatment comparison commonly focuses on the difference between groups in their mean changes. Such a contrast is not reported in the registry record. It would be inappropriate to construct a contrast from unreported group values, or to treat a study's endpoint definition as if it were evidence of a particular result.
What does the model description tell us?
The endpoint description names a mixed repeated measures model for change for missing data and identifies the full analysis set. In general, repeated-measures models can use measurements collected across time and account for the correlation among observations from the same participant. A mixed model can also accommodate some incomplete outcome records, subject to its model structure and assumptions. The registry does not give the model formula, covariance structure, fixed effects, estimation method, or assumptions about why measurements are missing. It is therefore not possible to determine the exact implementation or independently reproduce the analysis from the record.
The phrase “for missing data” does not itself state how much data were missing or establish that the model's assumptions were met. General missing-data methods rely on assumptions about the relationship between observed and unobserved outcomes. Those assumptions and supporting diagnostics are not reported in the registry record. The number of participants contributing to the primary analysis is also not reported.
How should precision and significance be understood?
In general, a confidence interval describes uncertainty around an estimate under a statistical model. It gives a range of effect sizes compatible with the observed data and assumptions; it does not guarantee that the true effect lies within that interval. A p-value, when reported, summarizes how incompatible the observed data are with a specified null model under the analysis assumptions. Neither quantity describes clinical importance on its own. No confidence interval or p-value for the primary comparison is reported in the registry record, so neither precision nor statistical significance can be assessed.
Over-dispersion is a general concern when data vary more than a model's assumed distribution allows, which can make uncertainty estimates unreliable if not addressed. The named primary endpoint is continuous, and the record does not indicate that over-dispersion was a concern or describe a method to assess it. It should not be assumed to be relevant to this trial's analysis without further evidence.
What can be said about planning?
Sample-size calculations are planning exercises based on assumptions about the target effect, variability, significance level, allocation, and analysis. They are distinct from observed results and do not establish what a trial found. The record states general assumptions for planning illustrations, including a two-sided significance level of 0.05, equal allocation, and a normal approximation, but it does not report a trial-specific sample-size justification. No numerical planning illustrations are available in the registry record. Such illustrations, if considered, would not be observed power or a substitute for an effect estimate and its confidence interval.
Overall, the record provides a limited description of the primary endpoint and model approach, but no numerical efficacy analysis. Additional statistical details, including the complete analysis plan, model specification, and treatment-effect estimates, are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists three outcome measures and identifies the primary endpoint as change from baseline in plasma oxalate concentration after 52 weeks. It also names change from baseline in kidney function and frequency of kidney stone events as secondary outcomes. The record indicates that the primary outcome has several categories or time points and is not reduced to one comparison. The specific categories or time points are not described in the posted results.
When a study tests multiple outcomes, time points, or comparisons, the chance of at least one apparently unusual result can increase. General approaches to multiplicity include defining a primary comparison in advance, adjusting significance thresholds, or using a hierarchical testing plan. The registry record does not report whether any such approach was prespecified or used, nor does it provide a testing hierarchy or adjusted results. No claim about multiplicity control can therefore be made.
For missing data, the primary endpoint description says the full analysis set was analyzed using a mixed repeated measures model for change. This identifies the stated population and a model approach, but the number analyzed, the extent of missingness, and the assumptions or sensitivity analyses are not reported in the registry record. In general, model-based handling of incomplete measurements depends on assumptions about the missingness process and the specified model. The record does not provide enough detail to evaluate those assumptions.
The registry lists no analysis entries. It does not report whether additional analysis populations were used, how protocol deviations were handled, or whether sensitivity analyses were conducted. These absences limit assessment of the robustness of the primary analysis; they do not establish that such analyses were or were not performed outside the posted record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Oxabact OC5 Capsules | 3 | 13 | 23.1% |
| Placebo Capsules | 4 | 12 | 33.3% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Oxabact OC5 Capsules | 0 of 13 |
| Placebo Capsules | 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 |
|---|---|
| Oxabact OC5 Capsules | 13 of 13 |
| Placebo Capsules | 11 of 12 |
Most frequent serious adverse event terms
| Event term | Organ system | Oxabact OC5 Capsules | Placebo Capsules |
|---|---|---|---|
| Calculus urinary | Renal and urinary disorders | 0 of 13 | 2 of 12 |
| Renal colic | Renal and urinary disorders | 1 of 13 | 1 of 12 |
| Nephrolithiasis | Renal and urinary disorders | 0 of 13 | 1 of 12 |
| Renal impairment | Renal and urinary disorders | 0 of 13 | 1 of 12 |
| Ureterolithiasis | Renal and urinary disorders | 1 of 13 | 0 of 12 |
| Urinary tract obstruction | Renal and urinary disorders | 0 of 13 | 1 of 12 |
| Bacterial pyelonephritis | Infections and infestations | 0 of 13 | 1 of 12 |
| Escherichia urinary tract infection | Infections and infestations | 1 of 13 | 0 of 12 |
| Pyelonephritis acute | Infections and infestations | 1 of 13 | 0 of 12 |
| Flank pain | Musculoskeletal and connective tissue disorders | 0 of 13 | 1 of 12 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Oxabact OC5 Capsules | Placebo Capsules |
|---|---|---|---|
| Vomiting | Gastrointestinal disorders | 1 of 13 | 4 of 12 |
| Nasopharyngitis | Infections and infestations | 2 of 13 | 2 of 12 |
| Tonsillitis | Infections and infestations | 2 of 13 | 2 of 12 |
| Flank pain | Musculoskeletal and connective tissue disorders | 2 of 13 | 2 of 12 |
| Pyrexia | General disorders | 2 of 13 | 2 of 12 |
| Urinary tact infection | Infections and infestations | 1 of 13 | 2 of 12 |
| Calculus urinary | Renal and urinary disorders | 1 of 13 | 2 of 12 |
| Nephrolithiasis | Renal and urinary disorders | 1 of 13 | 2 of 12 |
| Renal colic | Renal and urinary disorders | 2 of 13 | 1 of 12 |
| Abdominal pain | Gastrointestinal disorders | 2 of 13 | 1 of 12 |
Serious events with the highest arm-level rate: calculus urinary (16.7%), renal colic (8.3%), nephrolithiasis (8.3%), renal impairment (8.3%), urinary tract obstruction (8.3%).
The safety record lists serious adverse events and other adverse events separately for Oxabact OC5 capsules and placebo capsules. In the Oxabact OC5 group, 3 participants were affected by a serious adverse event among 13 at risk; in the placebo group, 4 were affected among 12 at risk. Other adverse events affected 13 of 13 at risk in the Oxabact OC5 group and 11 of 12 at risk in the placebo group. No deaths were recorded in either group.
These are participant counts, not counts of all individual events. A participant may experience more than one event, and the registry does not provide event-level totals in this record. The listed serious-event terms are Calculus urinary (16.7%), Renal colic (8.3%), Nephrolithiasis (8.3%), Renal impairment (8.3%), Urinary tract obstruction (8.3%), and Bacterial pyelonephritis (8.3%). The denominator and coding details for these term percentages are not reported in the registry record.
In general, a serious adverse event is a regulatory safety category and does not, by itself, establish that treatment caused the event. These counts are descriptive. The registry record does not report a comparative statistical analysis of safety, event timing, severity details beyond seriousness, or attribution to study treatment. The group counts should therefore not be interpreted as proving a treatment-related difference.
12. What the Result Does, and Does Not, Mean
The registry record establishes the design and planned primary endpoint of a completed randomized Phase III study: comparison of Oxabact OC5 with placebo on change from baseline in plasma oxalate concentration after 52 weeks. It also gives enrollment, the analysis population description, and the named missing-data model. These registry entries describe the study framework, not its primary efficacy result.
The primary outcome's numerical results are not reported in the registry record. Without group estimates, a between-group contrast, and uncertainty around that contrast, the posted information cannot show the direction or size of any difference or how precisely it was estimated. The same limitation applies to the secondary outcomes named in the record, for which numerical results are also not reported.
The safety counts provide descriptive information about participants affected by serious and other adverse events, and the record reports no deaths in either group. Such counts do not establish causation or provide a complete comparative safety assessment. The registry does not provide the additional event details or statistical comparisons needed for those conclusions.
In general, clinical interpretation combines the estimated effect, its precision, the endpoint's meaning, and the study's conduct and limitations. Statistical significance, if it had been reported, would not alone establish that a difference was important to patients. Conversely, a result that is not statistically significant would not by itself demonstrate equivalence. No primary-outcome estimate or test result is available in the registry record to support either interpretation.
The appropriate conclusion is therefore limited: the registry describes the trial question and selected methods, but the posted results do not allow assessment of the primary treatment comparison. This is not a conclusion that the intervention did or did not change plasma oxalate concentration. It is a statement about what can be interpreted from the information recorded.
13. Why This Trial Matters Statistically
This trial is statistically notable as a randomized, quadruple-masked Phase III comparison with a defined continuous primary endpoint and a stated model approach for missing data. Those design features give readers a framework for understanding how the study intended to compare Oxabact OC5 with placebo. The registry also identifies kidney function change and frequency of kidney stone events as secondary outcomes, indicating that the study recorded more than one outcome domain.
At the same time, the record illustrates why design information and outcome reporting have distinct roles. A randomized design can support a fair comparison in principle, but it does not disclose the observed effect. The primary endpoint is named and its timeframe and unit are given, yet the numerical estimates and measures of uncertainty are not reported. Without them, readers cannot assess the effect's magnitude, precision, or consistency with a statistical hypothesis.
Reporting the analysis population and a missing-data method is useful, but fuller detail is needed to assess how the model was implemented and what assumptions supported it. The registry does not give the primary analysis count, model specification, or sensitivity analyses. It also does not report how multiple outcomes or time points were handled statistically.
These limitations are especially relevant when enrollment is 25: the count describes the study enrollment, but it cannot substitute for outcome estimates or reveal their precision. This general point does not imply a particular result or explain why the record lacks numerical results. The statistical importance of the record lies in the contrast between a clearly named clinical question and the absence of posted numerical findings needed to answer it.
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 principal limitation for interpreting efficacy is that numerical primary-endpoint results are not reported in the registry record. Group means, standard deviations, treatment contrast, confidence interval, and p-value are absent. The registry also does not report numerical results for the secondary outcomes it names. Consequently, effect direction, magnitude, and precision cannot be assessed from the posted information.
The record describes the primary analysis population as the full analysis set and names a mixed repeated measures model for change for missing data, but it does not state the number analyzed or the extent of missing outcome data. Details of the model specification, missing-data assumptions, diagnostics, and sensitivity analyses are not reported in the registry record. These omissions prevent independent assessment of the analysis implementation and its robustness.
The registry indicates that the primary outcome has several categories or time points and is not reduced to one comparison. It does not specify those categories or time points in the posted results. It also does not report a multiplicity strategy for the several outcomes and comparisons, or the study's sample-size justification and interim-analysis plan.
For safety, counts of participants affected and deaths are available, along with listed serious-event terms. The record does not provide event-level detail, timing, attribution, or comparative statistical analyses. The serious-event term percentages have no reported denominator or additional coding context. These limits mean the safety information should be read descriptively, not as evidence of causation or a definitive comparative assessment.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Study to Evaluate the Efficacy and Safety of Oxabact in Patients With Primary Hyperoxaluria — NCT03116685.
- Registry record last updated 2021-12-10; status last verified 2021-10.
- Results first posted 2021-12-09.
- 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
NCT03116685 is a completed, randomized, quadruple-masked, parallel-group Phase III study of Oxabact OC5 capsules versus placebo capsules in patients with primary hyperoxaluria. Enrollment was 25. The recorded study start date was 2018-01-09, and primary completion was 2021-04-15.
The primary endpoint was change from baseline in total plasma oxalate concentration after 52 weeks, measured in micromole/liter and summarized as a mean with standard deviation. The full analysis set and a mixed repeated measures model for change for missing data are specified. The registry names kidney function change and frequency of kidney stone events as secondary outcomes.
Numerical efficacy results and detailed statistical-plan information are not reported in the registry record. Safety counts include serious and other adverse events by group, with no deaths recorded in either group. These counts are descriptive and do not establish causation.