Study of Vaniprevir Plus PegIntron®/Ribavirin in Japanese Participants With Chronic Hepatitis C Who Relapsed After Treatment (MK-7009-044): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study of Vaniprevir Plus PegIntron®/Ribavirin in Japanese Participants With Chronic Hepatitis C Who Relapsed After Treatment (MK-7009-044) (NCT01405937), a randomized phase 3 study. The primary outcome is Percentage of Participants Achieving Sustained Virologic Response 24 Weeks After Completion of All Study Therapy (SVR24).

2. Clinical Question

3. Trial Design

This was a phase III, randomized, parallel-group study with no masking reported. Its official purpose was to evaluate the safety, tolerability, and efficacy of MK-7009, identified in the study title as vaniprevir, given with peginterferon alfa-2b and ribavirin. The study concerned Japanese patients with chronic hepatitis C infection who had relapsed after previous treatment. The brief description specifies genotype 1 and previous interferon-based therapy.

The two arms differed in the planned duration of vaniprevir. Participants in the 12 Week Arm received vaniprevir at 300 mg twice daily for 12 weeks, while participants in the 24 Week Arm received it for 24 weeks. Both arms received peg-IFN and ribavirin for 24 weeks. Thus, the randomized contrast is between combination regimens with different vaniprevir durations; it does not isolate vaniprevir from the other medicines.

The recorded enrollment was 51. The study started on 2011-08-29, had primary completion on 2013-02-26, and is listed as completed. Allocation is recorded as randomized, and masking as none. The randomization ratio, sequence-generation details, concealment procedures, and any additional design protections are not reported in the registry record.

The primary outcome was assessed 24 weeks after completion of all study therapy, with the timeframe described as up to 48 weeks. A Full Analysis Set was defined for primary reporting as randomized participants who received at least one dose. The registry record does not report the trial’s original sample-size justification or the assumptions used to choose enrollment.

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: 51 participants were randomized to receive 12 or 24 weeks of vaniprevir in combination with 24 weeks of peg-IFN α-2b (peg-IFN) and ribavirin (RBV).

Overall Study

Analysis population for the primary outcome, as defined in the registry: Full Analysis Set (FAS) population; all randomized participants who received at least one dose of study treatment.

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 Percentage of Participants Achieving Sustained Virologic Response 24 Weeks After Completion of All Study Therapy (SVR24), measured over 24 weeks after 24 weeks of study therapy (up to 48 weeks).

The primary endpoint was the percentage of participants achieving sustained virologic response 24 weeks after completion of all study therapy, called SVR24 in the registry. SVR24 was defined as an undetectable HCV RNA level at that follow-up point. The recorded timeframe was 24 weeks after 24 weeks of study therapy, up to 48 weeks.

This is a binary outcome: each participant either met the stated undetectable-RNA definition at the specified assessment or did not. The reported percentage therefore describes the share of the Full Analysis Set achieving the endpoint, with a confidence interval to express uncertainty around that estimate. The definition puts the assessment after treatment has ended rather than only at the end of dosing, so the endpoint asks whether the response is still present at the later, prespecified follow-up.

The study’s primary efficacy hypothesis was that the SVR24 percentage in at least one vaniprevir 300 mg twice-daily regimen would exceed 20%, identified in the brief description as historical standard-of-care data. That benchmark is part of the stated hypothesis, not a concurrently randomized standard-of-care arm. The endpoint can describe the recorded virologic response under each regimen, but the historical benchmark and the randomized regimen comparison answer different statistical questions.

The registry reports 95% Clopper-Pearson exact confidence intervals for each regimen. These intervals communicate the uncertainty associated with the arm-specific percentages; they do not by themselves establish that one regimen differs from the other.

7. Results Posted in the Registry

• Vaniprevir 24 Week Arm: 96.2% (25/26) versus 92.0% (23/25) on control; risk difference 4.2 percentage points (95% CI -8.8 to 17.1), risk ratio 1.05 (0.91–1.20); unadjusted two-proportion z-test p = 0.529.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Percentage of Participants Achieving SVR12

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Vaniprevir 24 Week Arm: 92.3% (24/26) versus 88.0% (22/25) on control; risk difference 4.3 percentage points (95% CI -12.0 to 20.7), risk ratio 1.05 (0.87–1.26); unadjusted two-proportion z-test p = 0.605.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Vaniprevir 24 Week Arm and the control. The interval gives the range of effects that remain compatible with the data.

Percentage of Participants Achieving Rapid Virologic Response (RVR)

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Vaniprevir 24 Week Arm: 88.5% (23/26) versus 88.0% (22/25) on control; risk difference 0.5 percentage points (95% CI -17.2 to 18.2), risk ratio 1.01 (0.82–1.23); unadjusted two-proportion z-test p = 0.959.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Vaniprevir 24 Week Arm and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes extend the assessment beyond SVR24, including SVR12, rapid virologic response at Week 4, complete early virologic response, undetectable HCV RNA at the end of treatment, and mean change from baseline in HCV RNA. The registry lists five secondary outcomes as posted, but detailed arm-level results are included for only SVR12 and rapid virologic response in the record summarized for these results. Values for the other named outcomes are not reported in the registry record.

Across the two secondary endpoints with arm-level results, the observed percentages are numerically higher in the 24 Week Arm, as they are for the primary SVR24 outcome. This broad directional pattern is compatible with the ordering of the primary point estimates, but it does not establish that the longer vaniprevir duration caused better outcomes. The secondary results do not provide a separate basis for a firm between-regimen conclusion.

The recalculated comparisons for the posted secondary proportions are unadjusted. Their intervals include no difference, and the record lists no sponsor-reported analyses for these secondary endpoints. Secondary outcomes can help show whether the primary pattern is echoed across related measures, but multiple outcome assessments create multiple opportunities for an apparently notable result to occur by chance. Without a reported multiplicity plan, unadjusted secondary comparisons should carry less weight than the primary endpoint analysis.

These outcomes also represent different assessment times and definitions. An early response, an end-of-treatment measure, and a response after treatment completion are not interchangeable endpoints. They can give complementary descriptions of the study observations, but they should not be combined into one overall result. The registry does not report detailed analysis methods for every listed secondary outcome or how missing measurements were handled for each one.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Percentage of Participants Achieving SVR12
• Percentage of Participants Achieving Rapid Virologic Response (RVR)
• Percentage of Participants Achieving Complete Early Virologic Response (cEVR)
• Percentage of Participants Achieving Undetectable HCV RNA at the End of Treatment (EOT)
• Mean Change From Baseline in HCV RNA (Log 10)

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is a binary proportion. For each arm, the numerator is the number of participants meeting the SVR24 definition and the denominator is the analysis population for that arm. The registry reports the outcome as a percentage and gives a 95% Clopper-Pearson exact confidence interval. This exact interval is based on the binomial model for an event count among a defined number of participants. It is an interval estimate, not a range in which a fixed percentage is guaranteed to fall.

In general, a confidence interval conveys both the estimate and its precision. A narrower interval indicates less sampling uncertainty under the method’s assumptions; a wider interval indicates more. With a binary outcome and limited arm sizes, the observed percentage can be compatible with a fairly broad range of underlying proportions. The arm-specific intervals reflect that uncertainty. They should be read separately from the question of whether the two arms differ.

The registry also records exact binomial tests for each arm, with p < 0.001 for both. A binomial test evaluates an observed event proportion against a specified reference proportion under a null hypothesis. The study description states a primary hypothesis that at least one vaniprevir regimen would exceed the historical 20% benchmark. The registry does not state the full test specification in the analysis entry, so the exact null and direction should not be inferred beyond the stated hypothesis and the recorded analysis method.

A p-value describes how compatible the observed data are with a specified null model, under the test assumptions. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect. The arm-level p-values should not be read as evidence that one regimen is better than the other: they are reported separately for each arm, not as a direct randomized comparison.

The recalculated comparison uses the arm-level summary statistics to form an unadjusted risk difference. A risk difference expresses the absolute contrast between the two event proportions. A value of zero corresponds to no difference in proportions; an interval containing zero is compatible with no difference at the chosen confidence level. The recalculated p-value for the SVR24 comparison is 0.529. Because the record flags a discrepancy, this simple recalculation is not a replacement for the sponsor’s own analysis.

General statistical principle: a direct comparison in a randomized parallel-group trial is the relevant analysis for asking whether outcomes differ between assigned regimens. Comparing each group separately with a historical threshold does not test that between-regimen contrast. Historical comparisons can also be affected by differences between the trial population, procedures, and the earlier data used to set the benchmark. The registry does not provide details about the source or comparability of that historical information.

The outcome is binary, so concepts such as the mean and standard deviation of a continuous measurement are not the central summaries for this endpoint. The main quantities are the event count, denominator, percentage, and confidence interval. The registry reports the outcome counts implicitly through arm-level information; the primary display gives percentages and exact intervals. The 12 Week Arm had 23 participants meeting SVR24 among 25 in the analysis population, and the 24 Week Arm had 25 among 26. These counts correspond to the posted percentages.

The record lists 95% confidence intervals for both arms, but it does not report a confidence interval for a sponsor-conducted between-arm effect. A recalculated interval can help describe the uncertainty in the absolute comparison, but its unadjusted derivation is not the same as the trial’s full prespecified statistical analysis. The statistical analysis plan, including any adjustments or additional methods, is not reported in the registry record.

Randomization helps define the intended comparison by assigning participants to regimens, but it does not eliminate uncertainty from a small dataset, missing outcomes, or deviations from planned treatment. The record identifies the allocation as randomized and the model as parallel. Details about randomization implementation, concealment, adherence, and handling of protocol deviations are not reported. These details matter when judging how closely the observed outcome contrast reflects the effect of assignment to the two regimens.

General principle: over-dispersion matters when observed variability is greater than the variability assumed by a statistical model, potentially making model-based uncertainty too small. It is not a reported feature of this binary SVR24 analysis, and the registry does not report an over-dispersion adjustment. The recorded arm-level method is an exact binomial approach for confidence intervals and exact tests.

Secondary outcomes include further binary virologic endpoints and a mean change in HCV RNA. Their statistical properties and appropriate summaries differ according to whether an outcome is a proportion or a continuous measurement. The registry record does not include enough information to describe detailed analysis models for every outcome. The interpretation should therefore remain tied to the posted definitions and summaries rather than assume an unreported modeling plan.

11. Confidence Intervals and Precision

The primary arm estimates are 92.0% (95% CI 74.0% to 99.0%) for the Vaniprevir 12 Week Arm and 96.2% (95% CI 80.4% to 99.9%) for the Vaniprevir 24 Week Arm. These confidence intervals are wide relative to the range of possible percentages. They indicate that the observed percentages are not precise estimates of the underlying response proportions, despite their high point estimates.

The interval for the 12-week regimen extends from 74.0% to 99.0%, while the interval for the 24-week regimen extends from 80.4% to 99.9%. Both include a broad range of plausible response percentages. The upper ends are close to 100%, but that does not remove uncertainty at the lower ends. Point estimates should therefore not be read as exact values for the broader population.

The arm-specific intervals describe uncertainty in each percentage, rather than uncertainty in the difference between regimens. For that comparison, the recalculated risk-difference interval includes zero, so the posted summary statistics do not establish a clear between-arm difference. The comparison is unadjusted and the record identifies a discrepancy with the sponsor analysis.

General interpretation: a 95% confidence interval is produced by a procedure that, under its assumptions, would cover the target parameter in 95% of repeated samples. It is not a statement that there is a 95% probability that this particular interval contains the fixed true value. The registry uses exact Clopper-Pearson intervals for the arm percentages. Their breadth is important context for the apparent closeness of the observed results.

12. 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 illustrations based on the observed effect, not the trial’s original enrollment plan. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect set to the stated fraction of the observed effect. The registry record does not report the original design assumptions or sample-size justification.

For a given assumed effect, the 80% power value is the estimated number of participants per arm for a design with an 80% chance of detecting that effect under the listed assumptions, if the assumed effect and statistical model are correct. The 90% power value is the corresponding per-arm estimate for a design with a 90% chance. These are planning quantities, not outcomes observed in this study. They are not observed power.

The entries for 100% of the observed effect use the observed contrast as the planning target. The entries for 75% and 50% of the observed effect represent progressively smaller target effects. Smaller effects are harder to distinguish from random variation, so they require more participants under the same planning assumptions. For SVR24, the listed participants per arm for 80% power are 506 for 100% of the observed effect, 974 for 75%, and 2,356 for 50%. The corresponding figures for 90% power are 677, 1,303, and 3,154.

The listed values are participants per arm, not total enrollment. They are based on an unadjusted recalculation from the observed summary statistics and should not be treated as a recommendation or as evidence about the trial’s actual design. When a planning curve is used alongside these estimates, it expresses the same relationship across assumed effect sizes: as the target effect becomes smaller, the required participant count rises. The estimates depend on the stated assumptions and on the observed effect used as their starting point.

13. 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 = 0.920; treatment proportion p₁ = 0.962; average p̄ = 0.941.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.3338 = 0.6543.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.3325 = 0.2799.
4. n = (0.6543 + 0.2799)² / (0.0415)² = 505.8, rounded up to 506 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 <- 0.92                          # control proportion
p1 <- 0.961538461538462                          # 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(1405937)
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 = 506 (80% power), 677 (90% power)
 75% of observed effect: n per arm = 974 (80% power), 1,303 (90% power)
 50% of observed effect: n per arm = 2,356 (80% power), 3,154 (90% power)
power.prop.test: 505.8 
Simulated power at n = 506 per arm: 0.803 (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.

14. Analyses Reported by the Sponsor

The registry records sponsor analyses for the primary endpoint as exact tests for a binomial proportion, one for each treatment arm, with p < 0.001 in both. The primary hypothesis described in the study summary concerns whether at least one 300 mg twice-daily vaniprevir regimen has an SVR24 percentage greater than the historical 20% benchmark. The recorded arm-level tests are not reported as a direct comparison between the two regimens.

The recalculated between-arm comparison uses posted summary statistics and gives an unadjusted p-value of 0.529. It addresses a different question: whether the observed SVR24 proportions differ between the randomized regimens. Its confidence interval includes no difference. This recalculation should not be confused with either arm’s exact test against a benchmark.

The registry marks a discrepancy between the posted results and the recalculation. In that situation, the sponsor’s own analysis takes precedence. The recalculated comparison is useful as a transparent, unadjusted reading of the arm summaries, but it cannot stand in for a prespecified sponsor analysis or establish what analysis was planned. The registry record does not report a sponsor-conducted direct comparison between the arms.

15. Multiplicity, Missing Data and Analysis Populations

The registry identifies a primary efficacy hypothesis and lists multiple secondary outcomes. It reports 8 outcome measures and 2 analyses in its study-level record, as well as five secondary outcomes posted. Testing or estimating several outcomes raises a multiplicity issue: when many questions are examined, at least one result may appear notable by chance even if no corresponding effect exists. This is a general statistical concern, not a conclusion that any specific result is false.

A plan for controlling multiplicity, such as a testing hierarchy or adjustment to account for multiple comparisons, is not reported in the registry record. Nor is there a stated hierarchy for interpreting the secondary endpoints. The primary endpoint should therefore remain the main efficacy focus, while secondary comparisons are best treated as supportive and exploratory unless a prespecified plan is available.

The primary population is defined as the Full Analysis Set, consisting of all randomized participants who received at least one dose of study treatment. The arm-level primary denominators are 25 and 26. The registry does not report how participants without an SVR24 assessment were classified, whether missing outcomes were imputed, or whether analyses under alternative missing-data assumptions were conducted. It also does not report reasons for missing endpoint data.

Because the Full Analysis Set requires receipt of at least one dose, it is not described as including every randomized participant regardless of treatment exposure. The registry does not provide enough information to determine how many randomized participants, if any, were excluded from the primary analysis or the reasons for any exclusions. The handling of treatment discontinuation and protocol deviations is also not reported.

Interim analyses, stopping rules, and the statistical analysis plan are not reported in the registry record. The original sample-size calculation and its design assumptions are likewise not reported. These gaps limit assessment of prespecification, the potential effects of repeated testing, and the completeness of the primary analysis. They do not change the posted estimates, but they constrain how confidently the reported analyses can be connected to the trial’s original statistical plan.

16. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: appendicitis (4.0%), depression (4.0%), pneumonia aspiration (4.0%), vomiting (3.8%), chills (3.8%).

The registry reports serious adverse events affecting 2 participants in the Vaniprevir 12 Week Arm, with 25 at risk, and 3 participants in the Vaniprevir 24 Week Arm, with 26 at risk. These figures describe participants with at least one serious adverse event as recorded for each arm; they do not identify the causal relationship of an event to a specific study medicine.

Other adverse events are reported for 24 participants in the 12 Week Arm and 26 in the 24 Week Arm, with the same respective at-risk counts. Serious and other adverse-event summaries are distinct categories and should not be added together. A participant may have experienced more than one event, and the registry figures do not establish that each event occurred in a different participant.

The record lists serious-event terms with percentages, including appendicitis, depression, pneumonia aspiration, vomiting, chills, and ankle fracture. These term-level percentages should not be interpreted as treatment-attributable risks without further information about event definitions, timing, severity, and causality. Death counts are not reported in the registry record. The safety summaries are descriptive; they do not by themselves establish comparative safety between regimens.

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

The posted primary results show that most participants in each analysis arm met the registry’s definition of SVR24. The observed percentage was 92.0% in the 12 Week Arm and 96.2% in the 24 Week Arm. The arm-level exact tests are reported as p < 0.001, in the context of the study’s stated hypothesis about exceeding a historical 20% benchmark. These figures describe this study population and its recorded endpoint.

The results do not establish that extending vaniprevir from 12 weeks to 24 weeks produces a higher SVR24 percentage. The observed difference is a point-estimate ordering, while the recalculated comparison has an unadjusted p-value of 0.529 and an interval compatible with no difference. The sponsor’s own analysis takes precedence where the registry flags a discrepancy, and its recorded tests are arm-level rather than a reported direct comparison.

The record also does not establish how the two regimens compare with a concurrent standard-of-care group. The 20% value is a historical benchmark in the stated hypothesis, not a randomized control arm. Differences between historical data and this study’s population or conduct may affect such a comparison, and the registry does not describe the historical data in sufficient detail to assess comparability.

The scope of interpretation is limited to Japanese participants with chronic genotype 1 hepatitis C who relapsed after previous interferon-based treatment, under the specified combination regimens. The study does not directly answer questions about populations or regimens not represented in the record. Missing-data handling, multiplicity procedures, and several details of the statistical plan are not reported, which adds uncertainty to interpretation.

These are statistical descriptions of posted clinical-trial results, not individualized medical guidance. The percentages, confidence intervals, and tests should be considered together: the percentages describe observed outcomes, the intervals convey their precision, and the tests address specified statistical questions. None alone supplies a complete account of benefit, harm, or clinical decision-making.

18. Why This Trial Matters Statistically

This study illustrates why the question behind a p-value matters. The sponsor’s recorded exact binomial tests are arm-specific, while the comparison of the two randomized regimens is a separate question. A result showing that each arm differs from a historical benchmark does not establish that the arms differ from one another. Keeping those hypotheses distinct prevents an arm-level finding from being mistaken for a randomized comparative result.

The primary point estimates are high, yet their confidence intervals remain broad. This is an important statistical distinction: a conspicuous point estimate can coexist with limited precision, especially when the analysis groups are modest in size. The estimated contrast between regimens is also uncertain, so the observed numerical ordering should not be turned into a definitive ranking.

The trial further highlights the role of a concurrent comparator. Its two arms vary in vaniprevir duration while both include peg-IFN and ribavirin; the historical benchmark is not randomized alongside them. The regimen comparison and the historical-threshold hypothesis therefore have different strengths and limitations.

Finally, the record leaves key analysis details unreported, including multiplicity handling, missing-data methods, and the original sample-size rationale. These omissions do not erase the results, but they matter when judging how complete the statistical evidence is and how much weight to place on secondary findings. Clear separation of observed outcomes, uncertainty, and unreported methods is central to responsible interpretation.

19. 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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

The enrolled population was specific: Japanese participants with genotype 1 chronic hepatitis C who had relapsed after previous interferon-based therapy. The results do not directly describe populations with different prior treatment histories or other disease characteristics, which are not represented in the registry description. The record does not provide subgroup results that would show whether outcomes varied across participant characteristics.

The study was randomized but had no masking reported. Lack of masking can be relevant to how subjective outcomes or event reporting are assessed, although the primary endpoint is defined by an HCV RNA measurement. The registry does not provide details about outcome assessment procedures, laboratory masking, or other safeguards, so their role cannot be evaluated from this record.

The comparison involved two active combination regimens with different vaniprevir durations, not a concurrent standard-of-care or placebo arm. The historical threshold used in the primary hypothesis is not a randomized comparator, and information about its source and comparability is not reported. The study can describe the observed outcomes in its arms, but the registry record does not support a direct randomized comparison with the historical benchmark.

Primary confidence intervals are broad, and the recalculated between-arm result is unadjusted. A discrepancy is flagged between the recalculation and sponsor analysis, so the sponsor’s own analysis takes precedence. The record does not report a sponsor-conducted direct comparison between arms. The original sample-size justification, missing-data methods, multiplicity plan, interim analyses, and detailed analysis plan are not reported in the registry record.

Safety data are summarized descriptively, with no death counts reported. The record does not provide enough detail to establish event attribution or a comprehensive comparative safety profile. These limitations call for a restrained reading of the reported outcomes rather than conclusions beyond the population, endpoints, and analyses documented.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Study of Vaniprevir Plus PegIntron®/Ribavirin in Japanese Participants With Chronic Hepatitis C Who Relapsed After Treatment (MK-7009-044) — NCT01405937.
• Registry record last updated 2018-10-18; status last verified 2018-09.
• Results first posted 2014-10-13.
• 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.

23. Record Summary

NCT01405937 is a completed phase III randomized parallel-group study of vaniprevir with peg-IFN and ribavirin in Japanese participants with chronic hepatitis C who relapsed after previous interferon-based treatment. It compared vaniprevir at 300 mg twice daily for 12 weeks versus 24 weeks; both regimens included peg-IFN and ribavirin for 24 weeks. No masking was reported.

The primary outcome was SVR24, defined as undetectable HCV RNA 24 weeks after completion of study therapy. The reported percentages were 92.0% and 96.2%, with 95% exact confidence intervals of 74.0% to 99.0% and 80.4% to 99.9%. Sponsor analyses are recorded as exact binomial tests for each arm, both with p < 0.001. The recalculated unadjusted between-arm comparison has p = 0.529; the record flags a discrepancy, so the sponsor’s own analysis takes precedence.

Important details, including the original sample-size rationale, multiplicity plan, missing-data handling, and full statistical analysis plan, are not reported in the registry record.