A Study of the Effect of SYN-010 on Subjects With IBS-C: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of the Effect of SYN-010 on Subjects With IBS-C (NCT02495623), a randomized phase 2 study. The primary outcome is Change From Baseline in the Area Under the Curve (AUC) of Breath CH4 Production at Day 7.

2. Clinical Question

The trial examined whether two dosage strengths of SYN-010 were associated with different changes in breath methane production over 7 days than placebo among breath methane-positive subjects with irritable bowel syndrome with constipation. The registry identifies the primary endpoint as change from baseline in the area under the curve of breath CH4 production at Day 7, measured in hours*ppm. The comparison is about this continuous breath measurement; the posted primary result is not a symptom outcome.

The registry record identifies the trial as randomized, double-blind, parallel-group, placebo-controlled, and phase 2. Its primary outcome is a measure of breath methane production rather than a direct measure of IBS-C symptoms. The posted results therefore address the specified breath measurement and do not by themselves answer broader questions about symptoms or other outcomes.

3. Trial Design

This was a phase 2, randomized, double-blind, parallel-group, placebo-controlled study sponsored by Theriva Biologics, Inc. The listed interventions were SYN-010 21 mg, SYN-010 42 mg, and placebo. The registry reports enrollment of 63 and status as completed. The recorded study start was 2015-06 and primary completion was 2015-10.

The endpoint summary describes a population of 79 subjects who consented or were randomized, with 63 dosed. These counts are not interchangeable: the primary analysis included 59 subjects with the required baseline and Day 7 CH4 values. The registry specifies 21 placebo subjects, 20 subjects in the 21 mg group, and 18 subjects in the 42 mg group for the Day 7 AUC analysis. Subjects missing CH4 values at baseline or Day 7 were excluded, according to the endpoint description.

The design is described as multi-dose, but the registry record does not report treatment duration beyond the primary endpoint timeframe of 7 days. It does not report the allocation ratio, sequence generation details, concealment procedures, or operational details of blinding. The record also does not report the trial's original sample-size justification or the assumptions used to select enrollment.

The posted primary outcome is the mean change from baseline in breath CH4 AUC at Day 7, with standard deviation as the dispersion measure. No secondary outcomes are posted in the record. No analysis entries are listed. Consequently, the available statistical account is limited to the aggregate primary outcome summaries and the recalculated unadjusted comparisons described in the interpretation and methods.

Randomization and blinding are design features intended to support fair comparison, but their presence alone does not establish that all potential biases were eliminated. The posted information does not describe adherence, protocol deviations, or the detailed analysis population rules beyond the exclusion of subjects missing required CH4 values.

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: 79 subjects were randomized into the study per IVRS. 63 subjects received at least one dose of SYN-010. 16/79 subjects were not administered a single dose of study drug or placebo. We considered the subject truly randomized once the subject had completed the breath methane test, completed the daily diary entries, and were assigned study drug.

Overall Study

Analysis population for the primary outcome, as defined in the registry: 79 subjects consented/randomized to treatment. 63 dosed subjects. 59 subjects (21, 20 \& 18 for the placebo, 21mg and 42mg, respectively) were included for the analysis of AUC on Day 7, and the subjects with missing CH4 values at either baseline or Day 7 were excluded from the analysis since the area under the curve could not be calculated.

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.

6. Primary Endpoint

The registry lists the primary outcome as Change From Baseline in the Area Under the Curve (AUC) of Breath CH4 Production at Day 7, measured over 7 days.

The primary endpoint is change from baseline in the area under the curve of breath CH4 production at Day 7. AUC combines measurements across time into a single summary of the measured breath methane profile; the unit is hours*ppm. The endpoint description gives a timeframe of 7 days and identifies the outcome as a continuous measure reported as a mean with standard deviation.

Breath methane is the measurement named in the trial's primary question. A continuous endpoint retains the scale of that measurement and permits summaries of both the group mean and the variability among participants. A change-from-baseline outcome describes how the measured value differs from its baseline value, rather than reporting only the Day 7 level. These are general features of continuous change outcomes; the record does not give additional detail about the measurement schedule or the exact AUC construction.

The posted analysis included 59 subjects: 21 in the placebo group, 20 in the 21 mg group, and 18 in the 42 mg group. The endpoint description says subjects with missing CH4 values at baseline or Day 7 were excluded from the AUC analysis. The record does not report individual participant trajectories or a separate symptom endpoint. Therefore, the primary endpoint should be read specifically as a breath methane measure, not as a direct summary of constipation, overall IBS-C symptoms, or quality of life.

In general, an objective continuous measurement can support a comparison of group averages, while its interpretation depends on what the measurement represents and how well it captures outcomes of interest. The registry record establishes the measure used for this trial but does not report validation information or a threshold for a clinically meaningful change.

7. Results Posted in the Registry

• Low Dose: mean 99.20 versus 72.70 on control; difference 26.50 (95% CI -15.15 to 68.15), standardized effect d = 0.39; z-test p = 0.212.
• High Dose: mean 57.30 versus 72.70 on control; difference -15.40 (95% CI -45.73 to 14.93), standardized effect d = -0.31; z-test p = 0.320.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: it is the mean change from baseline in Day 7 breath CH4 AUC, measured in hours*ppm. The registry reports a mean and standard deviation for each group. A mean gives the group average on the endpoint's original scale. A standard deviation describes how spread out individual measurements are around that average; it is not the uncertainty in the mean itself.

What does a mean difference represent?

The recalculated comparisons subtract the placebo mean from the mean in each SYN-010 group. The low-dose estimate is 26.5 hours*ppm, based on means of 99.2 and 72.7. The high-dose estimate is -15.4 hours*ppm, based on means of 57.3 and 72.7. A positive estimate means the treatment-group mean is higher than the placebo mean on the recorded change scale; a negative estimate means it is lower. The interpretation of higher or lower values as desirable is not specified by the registry record, so these directions should not be translated into a clinical benefit claim.

These recalculations use aggregate summaries and are unadjusted. They do not account for participant-level covariates, repeated measurements, or other possible features of the data. The record does not report whether the sponsor used a different model or adjustment strategy. No sponsor analysis is listed, and the record does not indicate a discrepancy with the recalculations.

What is a confidence interval?

A confidence interval expresses uncertainty around an estimated comparison under the calculation method. The low-dose 95% confidence interval is -15.15 to 68.15 hours*ppm, and the high-dose 95% confidence interval is -45.73 to 14.93 hours*ppm. In general, a 95% confidence interval is produced by a procedure that, over repeated samples under its assumptions, would cover the target value 95% of the time. It is not a range containing 95% of individual participant values, and it does not assign a probability to the true effect after observing this particular interval.

Both intervals cross zero, which is the value corresponding to no mean difference in these treatment-versus-placebo contrasts. That observation is consistent with the reported unadjusted p-values, 0.212 for low dose and 0.32 for high dose. A p-value is calculated under a null hypothesis and the test assumptions; it is not the probability that the null hypothesis is true, nor a measure of clinical importance. The p-values are unadjusted, and the registry does not report whether any multiplicity procedure was planned or applied.

Why does variability matter?

Each group has a standard deviation that is large relative to the precision of its mean estimate. General statistical reasoning is that greater participant-to-participant variability makes it harder to estimate a group average precisely when group size is fixed. This contributes to wider uncertainty around comparisons. The standard deviations are 79.4 for the low-dose group, 43.1 for the high-dose group, and 53.5 for placebo. Those summaries describe dispersion, not treatment effects by themselves.

The comparison calculations use a pooled standard deviation of 67.37 for low dose versus placebo and 49.0 for high dose versus placebo. Pooling is a general approach that combines variability estimates across two groups for a standardized comparison. The corresponding standardized estimates are 0.393 and -0.314. These values express the estimated differences relative to pooled variability; they do not replace the original-scale mean differences and do not establish clinical relevance. The record does not report a prespecified threshold for interpreting standardized effects.

What do missing endpoint values mean for the analysis?

The endpoint description states that 79 subjects consented or were randomized and 63 were dosed. It then identifies 59 subjects for the Day 7 AUC analysis and says that subjects missing CH4 values at baseline or Day 7 were excluded. The arm counts in that analysis are 21 for placebo, 20 for 21 mg, and 18 for 42 mg. Exclusion of participants with missing measurements can affect the composition of the analyzed groups if missingness is related to participant characteristics or outcomes. That is a general concern; the record does not report why values were missing or whether missingness differed among groups.

The registry does not report imputation, a missing-data sensitivity analysis, an intention-to-treat analysis, or another analysis population definition. It does not report a participant-level model, covariate adjustments, treatment-by-time terms, or diagnostics. Those details should not be inferred from the aggregate outcome summaries.

What can the analysis support?

Random allocation and double masking are design features that can reduce some sources of bias in comparisons, but the posted record does not give procedural details about randomization or masking. The recalculated estimates support description of the observed mean contrasts and their uncertainty under the unadjusted calculation. They do not independently verify the trial conduct, establish a causal mechanism, or resolve the impact of missing endpoint data.

In general, statistical interpretation combines the estimated effect, uncertainty, study design, outcome definition, and analysis choices. Here, interpretation is limited to a single posted primary outcome, two unadjusted comparisons, and the reported analysis group summaries. No secondary results or analysis entries are posted. The statistical account is consequently narrower than a full clinical trial report.

10. Confidence Intervals and Precision

Precision concerns how narrowly the data locate a group difference. The low-dose mean difference versus placebo is 26.5 hours*ppm, with a 95% confidence interval from -15.15 to 68.15. The high-dose mean difference is -15.4 hours*ppm, with a 95% confidence interval from -45.73 to 14.93. Both intervals include zero, the value representing no difference between the group means.

The intervals also include values in both directions. For low dose, compatible values extend from a negative difference to a positive difference; for high dose, they likewise include a range below and above zero. The point estimates therefore do not convey the full uncertainty. The results do not precisely isolate a single direction or magnitude for either comparison.

In general, a confidence interval reflects sampling uncertainty under the statistical method and its assumptions. It is not a guarantee that the true difference lies within the interval, nor a statement about the range of individual responses. The reported intervals are recalculated unadjusted estimates from the posted summary statistics. The registry does not report a sponsor confidence interval or an adjusted analysis.

The analyzed groups were 21 placebo subjects, 20 low-dose subjects, and 18 high-dose subjects. Group size and the observed variability both affect precision in general. The standard deviations were 53.5, 79.4, and 43.1, respectively. These results should therefore be read as uncertain estimates of average differences, not as precise determinations of the size or direction of a treatment effect.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm for 80% power and participants per arm for 90% power, not total events. They are illustrations based on the observed effect, not the trial's original design calculations. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each scenario uses the stated fraction of the observed effect as the effect to detect. The trial's own original design assumptions are not reported in the registry record.

For low dose versus placebo, planning for 100% of the observed effect gives 102 participants per arm for 80% power and 136 participants per arm for 90% power. Planning for 75% of the observed effect gives 181 and 242 participants per arm, respectively. Planning for 50% of the observed effect gives 406 and 544 participants per arm, respectively.

For high dose versus placebo, planning for 100% of the observed effect gives 159 participants per arm for 80% power and 213 participants per arm for 90% power. Planning for 75% of the observed effect gives 283 and 379 participants per arm, respectively. Planning for 50% of the observed effect gives 636 and 851 participants per arm, respectively.

The 80% column describes a planning target in which the assumed effect would be detected by the specified test in 80% of repeated studies under its assumptions. The 90% column uses a higher detection probability target. Smaller effects need more participants to attain either target, which is why the planning counts increase as the assumed fraction decreases. These calculations are not observed power; they are forward-looking illustrations, and their assumptions may not match the original trial design.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 26.500; pooled standard deviation σ = 67.373.
2. n = 2 × (1.96 + 0.842)² × 67.373² / 26.500² = 101.5, rounded up to 102 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 26.5                      # observed difference in means
sigma <- 67.3734026498245                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(2495623)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 102 (80% power), 136 (90% power)
 75% of observed effect: n per arm = 181 (80% power), 242 (90% power)
 50% of observed effect: n per arm = 406 (80% power), 544 (90% power)
power.t.test: 102.4 
Simulated power at n = 102 per arm: 0.800 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The record posts one primary outcome measure and no secondary outcome results. It lists zero analysis entries. Although the primary endpoint has two treatment-versus-placebo comparisons, the registry record does not report whether the trial's statistical plan adjusted for making more than one comparison, used a hierarchy, or specified another multiplicity approach. The recalculated p-values of 0.212 and 0.32 are unadjusted and should be interpreted as such. No adjustment should be assumed.

The endpoint description says that subjects with missing CH4 values at baseline or Day 7 were excluded from the Day 7 AUC analysis. It reports 79 subjects who consented or were randomized, 63 dosed, and 59 included in the analysis. It does not report the reasons for missing values, the number missing in each group, or whether missingness was associated with measured or unmeasured participant characteristics.

The record does not report an imputation method, a sensitivity analysis for missing data, or a comparison of results under alternative missing-data assumptions. It also does not state whether the analysis followed an intention-to-treat population or another prespecified population definition. The 59-subject endpoint population is described, but its relationship to any formal analysis population is not further detailed.

In general, excluding participants with missing outcomes can lead to bias if the participants with observed outcomes differ systematically from those without observed outcomes. That possibility cannot be assessed from the posted aggregate summaries alone. The registry also does not report interim analyses, stopping rules, a detailed statistical analysis plan, or adjustments for baseline covariates. These details are not reported in the registry record, so they should not be inferred from the results.

14. Safety Results

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

Other (non-serious) adverse events

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

Most frequent non-serious adverse event terms

The posted serious-adverse-event figures list 0 affected participants among 22 at risk in the low-dose group, 0 among 19 at risk in the high-dose group, and 0 among 22 at risk in the placebo group. These figures describe the registry's affected-participant counts and denominators; they do not establish that no adverse events of any kind occurred.

For other adverse events, the record lists 2 affected participants among 22 at risk in the low-dose group, 2 among 19 at risk in the high-dose group, and 1 among 22 at risk in the placebo group. The record lists no top serious-event terms. Death counts are not reported in the registry record.

Safety counts should be interpreted alongside the denominators and the specific event category. These are descriptive counts, not adjusted comparisons, and the record does not give event-level detail or a statistical safety analysis. The adverse-event denominators also differ from some primary endpoint analysis counts; they describe the safety groups as posted and should not be substituted for the Day 7 AUC analysis population.

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

The results describe mean changes in breath methane AUC at Day 7 for the placebo, 21 mg, and 42 mg groups. The unadjusted recalculated mean differences versus placebo are 26.5 hours*ppm for low dose and -15.4 hours*ppm for high dose. The corresponding confidence intervals include zero, and the p-values are 0.212 and 0.32. Taken together, the estimates are uncertain and do not precisely determine the direction or magnitude of the group differences.

These findings concern the registry's stated breath methane endpoint. They do not directly report changes in IBS-C symptoms, functioning, quality of life, or any other clinical outcome. No secondary outcome results are posted, and the registry does not report a threshold for a clinically meaningful change in breath methane AUC. It is therefore not possible from these posted results to establish how the measured differences relate to a meaningful change for participants.

The absence of a confidence interval excluding zero is not proof that the groups are identical. Conversely, a point estimate in one direction is not proof of a real difference. The estimates must be read with their uncertainty, the number of participants included, and the endpoint exclusions for missing CH4 values in mind.

The registry record identifies a randomized, double-blind design, but it does not include detailed information about the randomization procedures, analysis plan, multiplicity handling, or missing-data sensitivity analyses. Those gaps limit how fully the reported comparisons can be evaluated. The posted data can support a description of the observed group summaries and unadjusted contrasts; they do not answer every question about treatment effects or trial conduct.

No medical conclusion follows from these statistics alone. They neither establish benefit nor establish lack of benefit. They summarize what was measured and how uncertain the posted comparisons are, within the limits of the registry information.

16. Why This Trial Matters Statistically

This trial illustrates why the endpoint definition matters. The primary measure is breath CH4 AUC, not an IBS-C symptom score. A statistical comparison can be correctly calculated for the selected endpoint while still addressing only that measurement. Readers need to distinguish the measured biomarker from broader clinical outcomes that are not posted.

It also illustrates the importance of considering estimates and uncertainty together. The low-dose comparison has a positive point estimate and the high-dose comparison a negative point estimate, but both confidence intervals include zero and span values on either side of no difference. A point estimate by itself can make a result appear more definite than the data support.

The record provides an opportunity to distinguish trial design information from analysis detail. Randomization and double masking are reported, but the original sample-size justification, multiplicity plan, missing-data sensitivity analyses, and detailed analysis population rules are not. Those omissions matter because design labels do not substitute for knowing how outcomes were handled and how uncertainty was calculated.

Finally, the endpoint analysis includes 59 subjects, compared with 63 dosed and 79 who consented or were randomized. The endpoint description attributes exclusions to missing CH4 values at baseline or Day 7, but does not give reasons or group-specific missingness details. That difference in analysis counts is important context for reading the estimates and their precision.

The statistical value of this example lies in separating what is directly reported from what cannot be established: group means, unadjusted comparisons, and uncertainty are available, while broader outcomes and several analytic decisions are not reported in the registry record.

17. 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.

Interpretation is limited by the small analyzed groups: 21 placebo subjects, 20 low-dose subjects, and 18 high-dose subjects. The confidence intervals are broad and include zero for both unadjusted comparisons, so the observed mean differences are not precise estimates of direction or magnitude.

The Day 7 AUC analysis excluded subjects with missing CH4 values at baseline or Day 7. The record reports 59 analyzed subjects, 63 dosed subjects, and 79 subjects who consented or were randomized, but does not report the number or reasons for missing measurements by group. It does not report an imputation method or sensitivity analyses to assess the effect of exclusions.

The registry reports a single primary outcome measure and no secondary results. The endpoint is breath methane AUC, and the record does not report a threshold for clinical importance or additional symptom outcomes. Thus, the posted result has a narrow outcome scope.

The recalculated comparisons are unadjusted. The registry record does not report whether a multiplicity procedure, covariate adjustment, interim analysis, or other statistical method was part of the original plan. It also does not report the original sample-size justification, the allocation ratio, detailed randomization procedures, or the analysis population definition beyond the missing-value exclusion.

These are limitations of the information available in the registry record. They do not establish that a particular procedure was or was not used; those details are not reported in the registry record.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: A Study of the Effect of SYN-010 on Subjects With IBS-C — NCT02495623.
• Registry record last updated 2018-11-27; status last verified 2018-10.
• Results first posted 2017-03-08.
• 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.

21. Record Summary

NCT02495623 is a completed phase 2 randomized, double-blind, parallel-group, placebo-controlled study of SYN-010 in breath methane-positive subjects with IBS-C. The listed groups received 21 mg SYN-010, 42 mg SYN-010, or placebo. Enrollment was 63; the registry reports 79 subjects consented or randomized, 63 dosed, and 59 included in the Day 7 AUC analysis.

The primary endpoint was change from baseline in breath CH4 AUC at Day 7. The posted group means were 72.7 hours*ppm for placebo, 99.2 for low dose, and 57.3 for high dose. Unadjusted recalculated mean differences versus placebo were 26.5 for low dose and -15.4 for high dose; both 95% confidence intervals included zero. No secondary outcome results or analysis entries are posted.

The registry record does not report the original sample-size justification, detailed statistical plan, multiplicity approach, or missing-data sensitivity analyses. The results describe the posted breath methane endpoint and do not directly establish effects on IBS-C symptoms or other outcomes.