A Phase III Study of TMC435 in Genotype 1, Hepatitis C-infected Participants Who Failed to Respond to Previous IFN-based Therapy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Phase III Study of TMC435 in Genotype 1, Hepatitis C-infected Participants Who Failed to Respond to Previous IFN-based Therapy (NCT01288209), a randomized phase 3 study. The primary outcome is The Percentage of Participants With a Sustained Virologic Response at the End of Treatment (EOT) and 12 Weeks After the Last Dose of Treatment (SVR12).

2. Clinical Question

The comparison concerns two treatment strategies that differ in the planned duration of TMC435, while both include peginterferon alfa-2a and ribavirin. It is not a comparison of TMC435 against no TMC435, or of the combination against another drug regimen. Because the study was open-label, participants and study personnel were not masked to the assigned strategy. The clinical question is therefore specific to the selected population, these regimens, and the registry’s definition and timing of SVR12.

3. Trial Design

This was a randomized, open-label, parallel, two-arm Phase III study conducted in Japan. The registry record lists enrollment as 106 and status as completed. It gives a study start of 2011-02 and primary completion of 2012-09. The sponsor was Janssen Pharmaceutical K.K.

Both groups received TMC435 with peginterferon alfa-2a and ribavirin. In the first arm, TMC435 was planned for 12 weeks, with peginterferon alfa-2a and ribavirin continuing until Week 24. In the second arm, all three study drugs were planned for 24 weeks. The arm descriptions refer to treatment stopping at Week 24 under specified HCV RNA response conditions, but the descriptions in the registry record are incomplete, so the full stopping criteria are not reported in the registry record.

Random assignment can support a fair comparison by reducing systematic differences between groups at the start of a trial, though the registry record does not report the sequence-generation method, allocation concealment, or details of stratification. Open-label conduct can affect behavior, co-interventions, and assessment; the registry record does not describe procedures used to limit those risks. The primary outcome is based on a laboratory measure of HCV RNA, but details about assay procedures and masking of outcome assessors are not reported in the registry record.

The primary outcome population was the Full Analysis Set: participants who received at least one dose of study drug, met major eligibility criteria, and had efficacy data available after treatment. The primary results list 53 participants in each arm. How participants without post-treatment efficacy data were handled beyond the stated Full Analysis Set definition is not reported in the registry record. The registry lists 11 outcome measures, with 10 secondary outcomes posted, but the broader statistical analysis plan and the trial’s original sample-size justification 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.

Before assignment: Participants with genotype 1 HCV-infection who failed a previous course of interferon (IFN) based therapy received TMC435 100 mg once daily with PegIFNα-2a and ribavirin (PR) until Week 12 (OR Week 24), followed by PR until Week 24/48 based on response-guided treatment (RGT).

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The Full Analysis Set (FAS) consisted of all participants who received at least one dose of study drug during the study except for those who did not meet the major eligibility criteria for the study and participants who did not have efficacy data available after treatment with study medication.

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 The Percentage of Participants With a Sustained Virologic Response at the End of Treatment (EOT) and 12 Weeks After the Last Dose of Treatment (SVR12), measured over EOT (Week 24 or 48) and Week 36 or 60.

The primary endpoint is the percentage of participants with a sustained virologic response 12 weeks after the last dose of treatment. The registry defines SVR12 as undetectable plasma HCV RNA at the end of treatment and again at 12 weeks after the final dose. The specified assessment points are the end of treatment at Week 24 or Week 48 and follow-up at Week 36 or Week 60.

This endpoint uses a laboratory measure of virus in plasma rather than a symptom score. Requiring undetectable HCV RNA at both the end of treatment and the later follow-up distinguishes a response that persists after treatment from a result measured only during or at the end of treatment. It is a binary outcome for each participant: the participant either meets the stated undetectable-RNA definition at both assessment points or does not.

In the posted primary results, the percentage was 52.8% for the 12-week TMC435 arm and 35.8% for the 24-week TMC435 arm. The registry reports the Full Analysis Set definition as the analysis population. It does not report the assay’s detection threshold, the handling of missing measurements, or further details of the endpoint analysis in the registry record. Consequently, interpretation should stay tied to the stated endpoint and analysis population rather than assume additional rules for classifying incomplete assessments.

7. Results Posted in the Registry

• TMC435 100 mg 24 Wks + PR24/48: 35.8% (19/53) versus 52.8% (28/53) on control; risk difference -17.0 percentage points (95% CI -35.6 to 1.7), risk ratio 0.68 (0.44–1.05); unadjusted two-proportion z-test p = 0.078.

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.

The Percentage of Participants With a Sustained Virologic Response 24 Weeks After the End of Treatment (EOT) and 24 Weeks After the Last Dose of Treatment (SVR24)

• 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:
  • TMC435 100 mg 24 Wks + PR24/48: 35.8% (19/53) versus 50.9% (27/53) on control; risk difference -15.1 percentage points (95% CI -33.7 to 3.6), risk ratio 0.70 (0.45–1.10); unadjusted two-proportion z-test p = 0.117.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between TMC435 100 mg 24 Wks + PR24/48 and the control. The interval gives the range of effects that remain compatible with the data.

The Number of Participants With Viral Breakthrough During the Study

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • TMC435 100 mg 24 Wks + PR24/48: 11.3% (6/53) versus 13.2% (7/53) on control; risk difference -1.9 percentage points (95% CI -14.4 to 10.6), risk ratio 0.86 (0.31–2.38); unadjusted two-proportion z-test p = 0.767.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between TMC435 100 mg 24 Wks + PR24/48 and the control. The interval gives the range of effects that remain compatible with the data.

The Number of Participants Demonstrating Viral Relapse During the Study

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • TMC435 100 mg 24 Wks + PR24/48: 51.1% (23/45) versus 38.6% (17/44) on control; risk difference 12.5 percentage points (95% CI -8.0 to 33.0), risk ratio 1.32 (0.83–2.12); unadjusted two-proportion z-test p = 0.237.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between TMC435 100 mg 24 Wks + PR24/48 and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcomes provide supporting context around the primary SVR12 result, rather than a separate, definitive answer to the same question. SVR24 is another sustained-response measure with a later follow-up interval, and its observed comparison follows the same direction as SVR12. Viral breakthrough and viral relapse describe different events during or after treatment and should not be treated as alternative definitions of the primary endpoint. Their estimates do not establish a consistent difference across all outcomes.

The registry also lists outcomes based on HCV RNA changes and undetectable RNA during treatment, ALT normalization, and meeting response-guided treatment criteria. These are relevant to describing treatment response and course, but their numerical results are not reported in the registry record. A complete assessment of the overall secondary-outcome pattern is therefore not possible from the results recorded. The secondary outcome list alone does not indicate the magnitude or direction of results for endpoints without posted values.

Unadjusted secondary comparisons carry less weight because many outcomes can be examined, increasing the chance that an apparently notable finding arises by chance. The registry record does not report a multiplicity strategy, a hierarchy for confirmatory testing, or reported analyses for these secondary outcomes. The posted secondary comparisons are recalculated from summary statistics and should be read as descriptive. They do not independently confirm the primary comparison, especially when endpoints are related and may reflect overlapping participant responses.

Secondary results are most useful for understanding whether the primary observation sits within a broader pattern, while keeping differences in endpoint definition, timing, and denominator in view. They should not be combined informally into a single score or used to select only the findings that support a preferred interpretation. In this trial, the posted results offer some context, but the missing numerical results for other listed outcomes and the absence of a reported multiplicity plan limit how strongly the secondary evidence can be interpreted.

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

• The Percentage of Participants With a Sustained Virologic Response 24 Weeks After the End of Treatment (EOT) and 24 Weeks After the Last Dose of Treatment (SVR24)
• The Percentage of Participants Who Achieved a Greater Than or Equal to 2 log10 IU/mL Drop From Baseline in Plasma Hepatitis C Virus Ribonucleic Acid (HCV RNA) at Each Time Point During Treatment and Follow-up
• The Percentage of Participants With Undetectable Plasma Hepatitis C Virus Ribonucleic Acid (HCV RNA) During Treatment and at the End of Treatment (EOT)
• The Percentage of Participants With Undetectable Plasma Hepatitis C Virus (HCV) Ribonucleic Acid (RNA) Levels During Treatment for Participants Who Did Not Achieve Undetectable Plasma HCV RNA Levels at Week 12
• The Number of Participants With Viral Breakthrough During the Study
• The Number of Participants Demonstrating Viral Relapse During the Study
• The Number Participants With Abnormal Alanine Aminotransferase (ALT) Levels at Baseline Who Achieved Normal ALT Levels at the End of Treatment (EOT)
• The Percentage of Participants Who Met Response Guided Treatment (RGT) Criteria and Completed Treatment With Peginterferon Alpha-2a (PegIFNα-2a) and Ribavirin (RBV) at Week 24

9. Statistical Interpretation

10. Statistical Methods Explained

The main comparison is between two percentages: the proportion meeting the SVR12 definition in each assigned group. For a binary outcome, each participant contributes either a response or a non-response under the endpoint definition. The arm-level percentage is a compact summary of how often that response was observed in the analysis population. It does not by itself describe the uncertainty in the difference between groups, which is why a contrast and confidence interval are also useful.

What does the risk difference describe?

The posted risk difference is the percentage-point contrast expressed as a proportion, with the 24-week TMC435 arm compared against the 12-week TMC435 arm. Its estimate is -0.170. The negative sign means that the observed response percentage was lower in the 24-week arm under this subtraction order. This is an unadjusted comparison of the posted group summaries, not a model-adjusted estimate. It describes the absolute difference on the probability scale, rather than a relative comparison.

Risk differences are often useful for clinical interpretation because they keep the comparison on the same scale as the underlying event probabilities. Relative measures, such as a risk ratio or odds ratio, answer different questions and can give a different impression of the magnitude. The registry record includes recalculated relative measures, but the primary interpretation is anchored to the absolute risk difference and its uncertainty. None of these measures establishes a causal effect beyond the limits of the trial design and the quality of the available data.

How should the confidence interval be read?

A confidence interval expresses the range of estimates that are reasonably compatible with the observed data under the method used to calculate it. It is not a range containing a known true effect with certainty, and it is not a prediction interval for individual participants. The primary interval runs from -0.356 to 0.017. Because it includes zero, the posted unadjusted data are compatible with no difference as well as with differences in either direction within that range. The breadth of the interval also matters: it shows that the trial does not estimate the difference very narrowly.

The registry record does not report the original statistical method used by the sponsor for the primary endpoint, or details such as any covariate adjustment. The posted comparison is a simple unadjusted recalculation from the group summaries. The unadjusted p-value of 0.078 should be understood in that same limited context. It is not a substitute for considering the effect estimate, confidence interval, design, and analysis population together.

Why does the Full Analysis Set matter?

The registry defines the Full Analysis Set as participants who received at least one dose of study drug, met major eligibility criteria, and had efficacy data available after study medication. The primary results list 53 participants in each arm. This definition excludes people who did not meet major eligibility criteria and those without post-treatment efficacy data. Such exclusions can affect how closely an analysis reflects the randomized comparison. The registry record does not describe the number or characteristics of participants excluded from the Full Analysis Set, the reasons for missing efficacy data, or sensitivity analyses addressing missing outcomes.

Randomization aims to make assigned groups comparable at baseline, but analysis choices after randomization can weaken that protection if participants are excluded differently or for reasons related to outcome. The Full Analysis Set definition is therefore important context, not a guarantee that missing data have no effect. A full intention-to-treat analysis definition, adherence analyses, and missing-data procedures are not reported in the registry record.

What does open-label design imply?

In an open-label trial, participants and investigators know which treatment strategy is assigned. Knowledge of assignment can influence behavior, treatment adherence, additional care, and judgments about outcomes. SVR12 is based on HCV RNA measurements, which is less subjective than a self-reported outcome, but laboratory endpoint procedures and assessor masking are not reported in the registry record. The absence of masking does not invalidate the result, but it is relevant when considering possible sources of bias.

The registry describes randomization and a parallel two-arm design, but does not report the randomization method or allocation concealment. Allocation concealment concerns whether upcoming assignments could be known before enrollment; masking concerns knowledge after assignment. These are different safeguards, and the registry record does not give enough detail to evaluate the former.

What can secondary outcomes add?

Secondary outcomes can provide context about related response measures and events, including SVR24, viral breakthrough, and viral relapse. They may help describe whether the primary pattern is accompanied by similar or contrasting observations. However, many outcomes create more opportunities for chance findings, particularly when tests are not adjusted for multiple comparisons. The registry record lists no reported analyses for these secondary outcomes, and a multiplicity plan is not reported in the registry record. The secondary comparisons should therefore be considered descriptive rather than treated as independent proof.

The registry lists other secondary measures, including HCV RNA response at treatment time points, ALT normalization, and response-guided treatment criteria. Results for these are not included in the registry entries used for this analysis, so their numerical findings are not reported in the registry record. Likewise, the protocol’s prespecified analysis methods, any interim analyses, and the original sample-size justification are not reported in the registry record.

11. Confidence Intervals and Precision

The primary risk-difference estimate is -0.170, with a 95% confidence interval from -0.356 to 0.017. The interval includes zero, so the data do not rule out no difference between the arms under the recalculated unadjusted method. It also includes estimates on either side of zero, making the direction of the underlying difference uncertain. The point estimate alone should not be read as a precise measure of the treatment-duration contrast.

Precision depends in part on the amount of information available and how frequently the outcome occurs. The primary outcome denominators are 53 in each arm, and the observed response counts are 28 and 19. With these group sizes and outcomes, the confidence interval remains broad relative to the point estimate. The registry record does not report a prespecified precision target or an original sample-size justification, so the width cannot be evaluated against a documented design goal.

The same caution applies to secondary comparisons. For SVR24, the recalculated risk difference is -0.151 and the interval is -0.337 to 0.036. For viral breakthrough, the estimate is -0.019 with an interval from -0.144 to 0.106. For viral relapse, the estimate is 0.125 with an interval from -0.080 to 0.330. Each interval includes zero. These intervals describe uncertainty for separate outcomes; they are not interchangeable and do not collectively guarantee a particular overall conclusion.

Confidence intervals are most informative when read alongside the estimates and the endpoint definitions. They do not establish that all values in an interval are equally plausible, and they do not account for unreported design or analysis limitations. The posted intervals are recalculated unadjusted comparisons, not confidence intervals from a reported sponsor model. The registry record does not report a multiplicity-adjusted interval for the primary or secondary outcomes.

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 design assumptions. The stated calculation 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 planning figures for these binary outcomes are participants per arm, not total events.

The 80% power column gives the number of participants per arm that the planning calculation estimates would be needed to have an 80% chance of detecting the specified effect under those assumptions, if that effect were the true one. The 90% power column describes the corresponding participant count for a 90% chance. These are design-planning probabilities under a statistical model, not probabilities that the observed trial result is correct and not probabilities that a treatment works.

The displayed scenarios consider planning for 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. Smaller effects require more participants to distinguish them from no difference with the same planned power and significance level. This relationship is why the participant requirements rise as the assumed effect fraction becomes smaller. The observed group sizes in the trial were 53 per arm, whereas the planning illustrations are calculations for future studies under their specified assumptions.

These figures are not observed power. Observed power calculated after a trial is complete largely restates the observed effect and its uncertainty; it does not replace interpretation of the estimate and confidence interval. The registry record does not report the original sample-size calculation or the assumptions used when this trial was designed.

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 = 0.528; treatment proportion p₁ = 0.358; average p̄ = 0.443.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.7026 = 1.3770.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6922 = 0.5826.
4. n = (1.3770 + 0.5826)² / (-0.1698)² = 133.2, rounded up to 134 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 <- 0.528301886792453                          # control proportion
p1 <- 0.358490566037736                          # 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(1288209)
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 = 134 (80% power), 178 (90% power)
 75% of observed effect: n per arm = 240 (80% power), 321 (90% power)
 50% of observed effect: n per arm = 543 (80% power), 727 (90% power)
power.prop.test: 133.2 
Simulated power at n = 134 per arm: 0.813 (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. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint and multiple secondary outcomes, but it does not report a plan for handling multiplicity. When several outcomes are tested, the chance of at least one apparently unusual result can increase. Prespecified hierarchies, adjusted significance thresholds, or other multiplicity strategies can help control that issue. Whether any such approach was used in this trial is not reported in the registry record.

The posted comparisons are unadjusted recalculations from summary statistics. The registry lists no reported analyses for the primary or secondary outcomes in the analysis listing used for these results. The primary risk difference and its p-value should therefore not be mistaken for a documented sponsor model or a multiplicity-adjusted confirmatory test. The registry record does not report the full statistical analysis plan, covariate adjustments, subgroup analyses, or interim analyses.

Missing data also affect interpretation. The primary endpoint population is the Full Analysis Set, which excludes participants without efficacy data available after study medication, as well as those who did not meet major eligibility criteria. The primary outcome results list 53 participants per arm. The registry record does not report the number of randomized participants omitted from the Full Analysis Set, reasons for missing efficacy data, or methods for handling missing assessments. It also does not report sensitivity analyses exploring alternative assumptions about missing outcomes.

These details matter because the risk of bias from missing data depends on why data are missing and whether the reasons differ by group or relate to the endpoint. The stated population definition alone does not answer those questions. The registry record also does not report a complete intention-to-treat analysis population or the treatment of participants who discontinued or deviated from assigned treatment.

Without a reported multiplicity plan and fuller information on missingness and analysis populations, the primary comparison remains a useful summary of the posted data, but the certainty of broader confirmatory claims is limited. These gaps should be distinguished from the numerical uncertainty reflected in the confidence interval: statistical precision and potential bias are related considerations, but they are not the same issue.

15. 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: laceration (1.9%), erythema multiforme (1.9%), anaemia (1.9%), pyelonephritis acute (1.9%), hypoaesthesia (1.9%).

The registry reports serious adverse events in 2 participants in the 12-week TMC435 arm and 3 participants in the 24-week TMC435 arm. The recorded at-risk group size is 53 for each arm. These figures describe participants with serious adverse events, not the total number of all adverse events or their duration. The registry also lists serious adverse event terms, each with a reported frequency of 1.9%: laceration, erythema multiforme, anaemia, acute pyelonephritis, hypoaesthesia, and ureteric calculus. The record does not assign these listed terms to a particular arm in the registry record used for this analysis.

Serious adverse event counts are not a complete summary of safety. They do not capture the severity or frequency of non-serious events, timing, duration, causality assessments, or how events affected treatment. Death counts are not reported in the registry record. The posted counts should be read as descriptive observations in the study groups, not as proof of a safety difference or equivalence. The registry record does not report a statistical comparison of serious adverse events, and the study size does not support strong conclusions about uncommon harms.

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

The primary result is an observed comparison of SVR12 percentages between two regimens in Japanese participants with genotype 1 hepatitis C who had failed previous interferon-based therapy. The 12-week TMC435 arm had a higher posted percentage than the 24-week TMC435 arm. The recalculated unadjusted risk difference is negative when expressed as the 24-week arm minus the 12-week arm, but its confidence interval includes zero and extends in both directions around that possibility. The result is therefore uncertain in magnitude and does not precisely establish the direction of the population difference.

This finding does not show that one regimen works or fails. It does not compare TMC435-containing treatment with no treatment or another treatment regimen, and it cannot be generalized automatically to people outside the specified study population. It also does not answer questions about outcomes beyond the endpoints and follow-up periods recorded in the registry. A difference in observed response percentages can arise from sampling variability as well as from a true difference between strategies.

The trial’s randomized design is relevant to comparison, but interpretation also depends on implementation and analysis. The registry record does not report important details such as allocation concealment, the original statistical analysis plan, how missing outcomes were handled, or a multiplicity strategy. The open-label design and Full Analysis Set definition also require attention. These limitations do not erase the posted observations; they constrain how confidently those observations can be extended.

Secondary outcomes add descriptive context but cannot repair uncertainty in the primary endpoint or serve as independent confirmation without an appropriate prespecified analysis. The serious adverse event counts are likewise descriptive and are not a complete safety assessment. The most defensible reading is therefore narrow: the registry records different observed SVR12 percentages for the two assigned treatment strategies, alongside an unadjusted interval that does not exclude no difference. The data do not establish a definitive treatment-duration advantage or a complete account of benefit and harm.

17. Why This Trial Matters Statistically

This trial illustrates why an observed difference between group percentages should be interpreted together with its uncertainty. The primary point estimate favors the 12-week TMC435 strategy in direction, but the risk-difference interval includes zero. A reader who focuses only on the percentages may overstate what the trial establishes; a reader who focuses only on a p-value may miss the range of effects compatible with the data. Considering the estimate and interval together gives a more balanced account.

The study also highlights the distinction between a randomized design and the analysis population used for the reported endpoint. Randomization is intended to support comparable groups, while exclusion of participants without post-treatment efficacy data can affect that comparison. The Full Analysis Set definition and the absence of reported missing-data methods are therefore central statistical context, not administrative details.

Comparing two active treatment strategies with different planned TMC435 durations raises a focused question, but it does not isolate every possible mechanism or answer broader comparative-treatment questions. Open-label conduct, unreported analysis details, and secondary outcomes without a reported multiplicity plan all shape the strength of inference. The listed planning illustrations further show how required group sizes depend on the effect a future study aims to detect; they are not evidence about the power achieved in this completed trial.

Overall, the record is a useful example of reading clinical-trial results at several levels: endpoint definition, group percentages, absolute contrast, confidence interval, analysis population, missingness, and safety description. Each contributes distinct information. None alone is sufficient to support a broad conclusion about efficacy or safety.

18. 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.

Several limitations are specific to what is recorded for this trial. The study was open-label, and the registry record does not describe masking of outcome assessors or laboratory procedures. Although randomization is recorded, the method for generating assignments and allocation concealment are not reported in the registry record. These omissions limit assessment of possible selection and assessment biases.

The primary analysis is defined using a Full Analysis Set that excludes participants without post-treatment efficacy data and those who did not meet major eligibility criteria. The record does not report how many randomized participants were excluded, why data were unavailable, or whether missing outcomes differed by arm. No sensitivity analyses for missing data are reported in the registry record.

The posted comparison is an unadjusted recalculation, and no sponsor analyses are listed for the outcomes discussed. The original analysis plan, model specification, and any prespecified covariate adjustments are not reported in the registry record. The trial’s original sample-size justification and interim analysis plans are also not reported. Planning illustrations based on observed effects cannot resolve whether the original design had adequate precision for its intended question.

There are also limits to the secondary evidence. The registry lists multiple secondary outcomes, but numerical results for several listed measures are not reported in the registry record. A multiplicity strategy is not reported, and the listed secondary comparisons should not be treated as confirmatory. The serious adverse event summary is brief: death counts are not reported in the registry record, and the listed serious event terms are not assigned to an arm in the registry record used for this analysis. These gaps prevent a comprehensive interpretation of safety and of the full outcome pattern.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: A Phase III Study of TMC435 in Genotype 1, Hepatitis C-infected Participants Who Failed to Respond to Previous IFN-based Therapy — NCT01288209.
• Registry record last updated 2014-01-24; status last verified 2013-12.
• Results first posted 2014-01-24.
• 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.

22. Record Summary

The registry describes a completed, randomized, open-label, parallel Phase III study in Japan of TMC435 with peginterferon alfa-2a and ribavirin in genotype 1 hepatitis C participants who failed previous interferon-based therapy. The primary posted outcome is SVR12. The observed percentages were 52.8% for TMC435 for 12 weeks with peginterferon alfa-2a and ribavirin continuing to Week 24, and 35.8% for TMC435 with the accompanying drugs for 24 weeks.

The recalculated unadjusted risk difference, comparing the 24-week arm with the 12-week arm, is -0.170, with a 95% confidence interval from -0.356 to 0.017 and an unadjusted p-value of 0.078. The interval includes no difference, so the estimate is uncertain. Secondary results provide limited descriptive context; a multiplicity plan, missing-data procedures, and the original statistical design assumptions are not reported in the registry record.