A Phase 3 Study of Solosec® for the Treatment of Trichomoniasis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Phase 3 Study of Solosec® for the Treatment of Trichomoniasis (NCT03935217), a randomized phase 3 study. The primary outcome is Microbiological Cure at the TOC Visit.

2. Clinical Question

3. Trial Design

The registry describes a completed Phase 3 study that was multicenter, prospective, randomized, placebo-controlled, and parallel-group. The official title describes the study as double-blind, while the registry’s masking classification is quadruple. The registry record does not identify which roles were masked, so the exact masking arrangements cannot be characterized further from this information.

The interventions were a single oral dose of Solosec containing 2 grams of secnidazole and a single oral dose of placebo. Both were administered with applesauce. The study title and record describe delayed treatment, but details of that process, including its timing, are not reported in the registry record. Allocation is listed as randomized; the method used to generate or conceal the allocation sequence is not reported in the registry record.

The registry lists enrollment as 147 and status as completed. For the primary outcome, the reported groups were Solosec 2 Grams, with 64 participants, and placebo, with 67 participants. These are the endpoint denominators; the registry record does not explain the relationship between those denominators and the enrollment figure. They should not be treated as interchangeable.

The primary outcome was microbiological cure at the test-of-cure visit, assessed during Study Day 6-12. It was defined by a vaginal culture negative for T. vaginalis and was evaluated in the modified intent-to-treat population of patients with a positive culture at baseline. The registry record lists one outcome measure and no posted secondary outcomes. Details such as recruitment sites, treatment adherence, and the original statistical design assumptions 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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Modified Intent to Treat Population (Patients with culture positive for T. vaginalis at baseline)

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: Safety Population

6. Primary Endpoint

The registry lists the primary outcome as Microbiological Cure at the TOC Visit, measured over Study Day 6-12.

The primary endpoint was microbiological cure at the test-of-cure visit, or TOC. Cure was defined as a vaginal culture negative for T. vaginalis at that visit. The stated assessment window was Study Day 6-12, and the outcome was a count of participants meeting the definition.

A culture-based endpoint records whether the organism was detected in the collected vaginal sample at the specified assessment. It therefore captures a microbiological finding at that time, rather than a broader measure of symptoms, quality of life, or later recurrence. The registry record does not report additional endpoint definitions or later follow-up results.

The primary analysis population was the modified intent-to-treat population: patients whose culture was positive for T. vaginalis at baseline. Restricting this outcome population to participants with a positive baseline culture makes the follow-up culture result interpretable as a change in microbiological status among those who had evidence of infection at entry. However, the term “modified intent-to-treat” does not itself explain how participants with missing follow-up cultures or other protocol deviations were handled. Those details are not reported in the registry record.

Microbiological cure is a direct, defined endpoint for comparing the culture findings between randomized groups at the scheduled visit. It does not, on its own, establish the duration of the observed status or address outcomes that were not measured or posted.

7. Results Posted in the Registry

• Solosec 2 Grams: 92.2% (59/64) versus 1.5% (1/67) on control; risk difference 90.7 percentage points (95% CI 83.5 to 97.9), risk ratio 61.77 (8.82–432.65); unadjusted two-proportion z-test p = <0.001.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary: each participant either met the microbiological-cure definition at the TOC visit or did not. For a binary endpoint, the event count and the number assessed in each group provide the basis for describing the observed event proportion. The registry reports 59 cures among 64 participants in the Solosec group and 1 among 67 participants in the placebo group. The corresponding reported proportions are 0.922 and 0.015. The analysis population is not all enrolled participants by definition; it is the modified intent-to-treat population with a positive baseline culture.

What does the risk difference express?

A risk difference subtracts the event probability in one group from the event probability in the comparison group, with the direction determined by how the groups are ordered. Here the posted comparison is Solosec 2 Grams versus placebo and reports a risk difference of 0.907. In plain language, this is an absolute contrast between the reported probabilities of microbiological cure at the specified visit. It keeps the comparison on the probability scale rather than expressing it as a relative multiple.

The registry gives a confidence interval from 0.835 to 0.979 for the risk difference. A confidence interval is a range of values compatible with the observed data under the method used to calculate it. It conveys uncertainty about the estimated contrast; it is not a range containing a known fixed proportion of individual participant outcomes. The interval is relatively narrow compared with the estimate’s scale, but that description does not establish that the analysis is free of bias or that the endpoint represents outcomes outside the stated visit. The interval construction method is not reported in the registry record.

How do relative measures differ?

The risk ratio compares the event probabilities as a ratio. The posted risk ratio is 61.77, with an interval from 8.818 to 432.7. The odds ratio compares the odds of the event rather than the probabilities; the posted odds ratio is 778.8, with an interval from 88.43 to 6859.0. Because the placebo group had only 1 recorded cure, the relative comparisons are especially sensitive to the sparse event count in that group. Relative measures can be much larger than an absolute difference and can have wide intervals when one group has very few events. They should not be read as though they were percentage-point differences.

These estimates are different summaries of the same binary comparison, not independent findings. They do not add separate evidence beyond the outcome counts. The registry record does not report the model, continuity correction, or interval method used for the relative measures, so those methodological details cannot be inferred from the values alone.

What does the p-value address?

The unadjusted p-value is <0.001. In general, a p-value describes how incompatible the observed data, or data more extreme, are with a specified null hypothesis under the assumptions of the test. It is not the probability that the null hypothesis is true, nor does it measure the size or practical importance of an effect. The registry labels this p-value unadjusted. The test and its assumptions are not reported in the registry record, so the p-value should be interpreted as the posted unadjusted result rather than as a fully documented analysis.

Random allocation and a placebo comparator provide the design for a between-group comparison. In general, randomization can reduce systematic differences between groups at assignment, while masking can reduce some forms of biased assessment or behavior. The record lists randomized allocation and quadruple masking, and the official title says double-blind. It does not describe allocation procedures, masking roles, deviations, or whether the primary analysis adjusted for any baseline variables. No specific benefits beyond those general design principles can be established from the posted summary.

Why can sparse outcomes matter?

When an event is rare in a group, relative estimates can be unstable: a small change in event count can substantially alter a ratio. This is a general statistical issue, particularly relevant to an outcome with 1 recorded cure in the placebo group. The wide intervals for the reported risk ratio and odds ratio are consistent with considerable uncertainty on those relative scales. The risk difference provides an absolute-scale summary and is also accompanied by a confidence interval, but none of these summaries removes uncertainty about missing observations, endpoint measurement, or the analysis choices that are not documented.

Over-dispersion is a general concern when counts vary more than a statistical model expects, which can make standard errors too small if the model does not account for that extra variation. The primary endpoint is reported as a binary participant count rather than a repeated count or rate, and the registry does not report a model that would allow assessment of over-dispersion. It is therefore not possible to say whether or how this issue was evaluated in the trial analysis.

The registry reports no adjusted analysis and no secondary outcomes. It also does not report the primary test specification, missing-data approach, prespecified analysis plan, or sensitivity analyses. The posted results support a description of the reported endpoint counts and comparison, but not reconstruction of the full analysis pathway.

10. Confidence Intervals and Precision

The risk-difference estimate is 0.907, with a confidence interval from 0.835 to 0.979. The interval gives a range of values compatible with the observed data under the calculation method used. Its endpoints are both positive, so the reported interval does not include a risk difference of zero. The statistical method and confidence level used to construct it are not reported in the registry record; they should not be inferred.

Precision depends on the amount and distribution of outcome information, not only on the total number enrolled. The primary analysis includes 64 participants in the Solosec group and 67 in the placebo group, with 59 and 1 cures, respectively. The imbalance in event counts is particularly important for relative measures. The risk-ratio interval, from 8.818 to 432.7, and odds-ratio interval, from 88.43 to 6859.0, are wide. They indicate that the relative magnitude is much less precisely pinned down than a single point estimate might suggest.

The absolute-scale interval is also an estimate from this specific trial population and visit window. It does not account for sources of uncertainty that are not represented in the calculation, such as unreported missing-data handling, measurement procedures, or analysis choices. The registry does not report whether any sensitivity analyses were conducted. Precision in the statistical sense therefore should not be confused with certainty about generalizability, durability, or outcomes outside the endpoint definition.

The reported p-value, <0.001, addresses evidence against a null comparison under the test used, while the confidence interval communicates a range of effect estimates. Neither quantity describes the probability that a future trial will produce the same result. The interval method and test are not described in the registry record, which limits independent assessment of their assumptions.

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 sample-size figures are planning illustrations based on the observed effect, not the trial’s own design. For this binary outcome, figures are participants per arm, not total events. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning scenario uses the stated fraction of the observed effect as the effect to detect. The original trial’s own design assumptions and sample-size justification are not reported in the registry record.

The 80% power column gives the illustrative number of participants per arm for a design with an 80% chance of detecting the specified effect under the planning assumptions, if that effect and those assumptions held. The 90% power column gives the corresponding figure for a 90% chance. These are design concepts, not guarantees about a future study or statements about the probability that the observed result is true.

The listed figures are 4 participants per arm for 80% power and 4 for 90% power when planning for 100% of the observed effect; 7 and 9 when planning for 75% of the observed effect; and 13 and 17 when planning for 50% of the observed effect. The figures increase as the effect to detect becomes smaller: smaller effects are harder to distinguish from random variation and generally require more participants under otherwise comparable assumptions.

These estimates are calculated from the observed effect, which is unusually large in the posted comparison and based on sparse cures in the placebo group. Consequently, the illustrations should not be treated as a reconstruction of the trial’s enrollment target or as a recommendation for a future study. This is not observed power; it is a planning calculation based on stated assumptions.

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, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.015; treatment proportion p₁ = 0.922; average p̄ = 0.468.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.7057 = 1.3831.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.2945 = 0.2478.
4. n = (1.3831 + 0.2478)² / (0.9069)² = 3.2, rounded up to 4 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
p0 <- 0.0149253731343284                          # control proportion
p1 <- 0.921875                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^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 (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(3935217)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 4 (80% power), 4 (90% power)
 75% of observed effect: n per arm = 7 (80% power), 9 (90% power)
 50% of observed effect: n per arm = 13 (80% power), 17 (90% power)
power.prop.test: 3.2 
Simulated power at n = 4 per arm: 0.954 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-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 registry lists one outcome measure and no posted secondary outcomes. The primary endpoint is microbiological cure at the TOC visit during Study Day 6-12. No multiplicity adjustment is described in the registry record. With only one posted outcome measure, there is no documented family of posted outcome tests for which an adjustment can be evaluated, but the record does not establish the complete set of analyses that may have been planned or conducted.

The comparison reports an unadjusted p-value of <0.001. Whether the primary analysis was prespecified, whether there were interim analyses, or whether any other comparisons were examined is not reported in the registry record. The registry also does not provide a statistical analysis plan, so the treatment of multiple testing and outcome selection cannot be independently assessed.

The primary population is the modified intent-to-treat population, defined as patients with a positive baseline culture for T. vaginalis. The group denominators for this endpoint are 64 for Solosec and 67 for placebo. The registry record does not report how missing TOC cultures, withdrawals, protocol deviations, or participants without an evaluable follow-up result were handled. It does not state whether missing outcomes were treated as failures, excluded, imputed, or addressed through sensitivity analyses.

The modified intent-to-treat definition clarifies one eligibility condition for the primary outcome analysis, but it does not provide the complete participant flow or explain all analysis exclusions. The relationship between the registry enrollment of 147 and the outcome denominators is not described. Details about the full analysis population, per-protocol analyses, and adjustments for baseline characteristics are not reported in the registry record.

These gaps limit assessment of how robust the result is to missing data, analysis choices, or multiplicity. They do not change the reported counts, but they restrict interpretation of how the posted comparison was constructed and whether other analyses could affect the overall evidence.

14. 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 2% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse events for separate safety groups. In the Solosec group, 0 serious adverse events were recorded among 74 participants at risk; in the placebo group, 0 were recorded among 73 participants at risk. Deaths were recorded as 0 in both groups. These are counts in the registry record and do not establish that no unrecorded events occurred.

Other adverse events were reported for 6 of 74 participants at risk in the Solosec group and 14 of 73 in the placebo group. The record does not provide the specific terms for serious adverse events, and no top serious-event terms are listed. It also does not report event timing, duration, severity categories beyond the serious-event distinction, relatedness to treatment, or the method used to collect events.

The safety-group denominators differ from the primary endpoint denominators. They describe the safety reporting population and should not be substituted for the modified intent-to-treat population used for microbiological cure. These counts do not by themselves establish comparative safety or determine whether an event was caused by treatment.

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

The posted result describes microbiological culture status at a particular follow-up visit among patients who had a positive culture at baseline. In that population, the registry reports 59 cures among 64 participants assigned to Solosec 2 Grams and 1 among 67 assigned to placebo. The reported risk difference is 0.907, with a confidence interval from 0.835 to 0.979, and the unadjusted p-value is <0.001. These statistics describe a marked difference in the observed endpoint between the randomized groups.

The endpoint is not a measure of every aspect of infection or patient experience. A negative vaginal culture at the TOC visit during Study Day 6-12 does not, by itself, report symptoms, later culture results, recurrence, or long-term outcomes. No such results are posted in the registry record. The result also pertains to the defined modified intent-to-treat population, not automatically to every person enrolled or every population of interest.

The comparison is not a guarantee that an individual participant will have a particular outcome. Group-level event proportions and effect estimates describe patterns across the analyzed participants. The confidence interval conveys statistical uncertainty under the method used, but the method is not reported. The wide intervals for relative measures also counsel against treating their point estimates as precise descriptions of the magnitude on a relative scale.

The registry identifies a randomized, placebo-controlled design, but does not report allocation procedures, missing-data methods, or the statistical analysis plan. It also does not explain the relationship between enrollment and the analysis denominators. Those gaps limit evaluation of possible bias and the completeness of outcome assessment. Safety counts are reported separately and should not be conflated with microbiological cure or interpreted as proof of absence of risk.

Accordingly, the result supports a description of the posted between-group difference for this endpoint and assessment window. It does not, on its own, answer questions about outcomes not measured or reported, the durability of the result, or the result’s applicability beyond the studied analysis population.

16. Why This Trial Matters Statistically

This trial illustrates how a randomized placebo comparison can be summarized using an absolute risk difference alongside relative measures. For microbiological cure, the reported risk difference is 0.907. The risk ratio and odds ratio express the same binary comparison on relative scales and have much wider intervals. Reading the absolute and relative summaries together helps distinguish the observed difference in probabilities from the relative magnitude, which can be especially unstable when one group has very few events.

The outcome definition also matters. The endpoint was a negative vaginal culture at the TOC visit during Study Day 6-12, in participants with a positive baseline culture. That definition makes the statistical result specific and interpretable, but it also sets boundaries on what the result can establish. It does not supply information about later outcomes or measures that were not posted.

The record provides a useful contrast between outcome denominators and safety denominators. The primary analysis uses 64 participants in the Solosec group and 67 in placebo, while the safety groups report 74 and 73 participants at risk. Keeping these populations distinct is essential when reading event counts and avoids treating different analysis sets as if they were the same.

The planning illustrations show another statistical lesson: sample-size calculations depend on the effect size chosen for planning. The listed requirements rise when planning for a smaller fraction of the observed effect. Because the calculations are based on the observed effect rather than the trial’s original design assumptions, they should be read as hypothetical planning examples, not as evidence about the trial’s power or as a design justification.

Finally, the record demonstrates why a small p-value is only one part of interpretation. Effect estimates, interval width, endpoint definition, analysis population, missing-data handling, and reporting completeness all matter. Here, some of those details are not reported in the registry record, so the posted numerical comparison can be described without claiming a complete account of its statistical analysis.

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.

The registry record leaves several trial-specific details unreported. It does not describe the randomization sequence, allocation concealment, masking roles, treatment adherence, or the conduct and timing of delayed treatment. Although it lists quadruple masking and the official title says double-blind, the masking procedures cannot be characterized further. The record also does not explain the relationship between the enrollment of 147 and the endpoint analysis denominators.

Details of the primary analysis are limited. The record does not identify the statistical test, interval construction method, adjustment strategy, or missing-data approach. It does not report whether participants with missing TOC cultures were excluded, counted as not cured, or handled another way. No sensitivity analyses are posted, and the original statistical analysis plan and sample-size justification are not reported in the registry record.

The primary result is restricted to the modified intent-to-treat population of patients with a positive baseline culture and to a culture assessment during Study Day 6-12. The registry lists no posted secondary outcomes, so the record does not provide a broader set of clinical outcomes or later follow-up results. The safety summary supplies counts but not event terms, timing, severity details beyond serious status, or treatment relatedness.

The relative estimates have wide confidence intervals, particularly the risk ratio and odds ratio, and the placebo group had 1 recorded cure. These features limit precision about the magnitude on relative scales. The sample-size illustrations use the observed effect and are not a substitute for the trial’s original design rationale. Taken together, these limitations mean that the posted results are best interpreted as a specific endpoint comparison rather than a complete account of all trial methods and outcomes.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: A Phase 3 Study of Solosec® for the Treatment of Trichomoniasis — NCT03935217.
• Registry record last updated 2023-10-04; status last verified 2023-09.
• Results first posted 2023-10-04.
• 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

The registry record describes a completed, randomized, parallel-group Phase 3 study of a single oral dose of Solosec containing 2 grams of secnidazole versus placebo for trichomoniasis in female patients. Both interventions were administered with applesauce. The primary endpoint was microbiological cure, defined as a negative vaginal culture for T. vaginalis at the TOC visit during Study Day 6-12, in the modified intent-to-treat population with a positive baseline culture.

The endpoint counts were 59 of 64 in the Solosec group and 1 of 67 in the placebo group. The reported risk difference was 0.907, with a confidence interval from 0.835 to 0.979, and the unadjusted p-value was <0.001. The record lists no posted secondary outcomes. Serious adverse events and deaths were recorded as 0 in both safety groups; other adverse events were reported for 6 of 74 participants at risk in the Solosec group and 14 of 73 in placebo.

Important details, including the missing-data approach, statistical analysis plan, and original sample-size assumptions, are not reported in the registry record.