A Study to Evaluate the Efficacy and Safety of ABT-493/ABT-530 in Adults With Chronic Hepatitis C Virus (HCV) Genotype 2 Infection: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study to Evaluate the Efficacy and Safety of ABT-493/ABT-530 in Adults With Chronic Hepatitis C Virus (HCV) Genotype 2 Infection (NCT02640482), a randomized phase 3 study. The primary outcome is Percentage of Participants With Sustained Virologic Response 12 Weeks Post-treatment (SVR12) in Arm A DB Active Drug Excluding Prior SOF + Ribavirin (RBV) ± pegIFN Failures: Noninferiority Analysis.

2. Clinical Question

The endpoint is sustained virologic response 12 weeks after treatment, abbreviated SVR12. The registry defines this as plasma HCV RNA below the lower limit of quantification at the specified post-treatment assessment. The primary question is therefore about the proportion meeting a virologic threshold at a defined follow-up time, not about an average change in a laboratory measurement.

The design also included a placebo arm during the double-blind period, and the registry lists further efficacy outcomes concerning SVR12, on-treatment virologic failure, and post-treatment relapse. However, the posted record does not give numerical results for the primary or secondary outcomes. It therefore does not allow readers to see the observed SVR12 percentage, its uncertainty, or the result of the noninferiority analysis.

3. Trial Design

ENDURANCE-2 is recorded as a Phase 3, randomized, double-blind, placebo-controlled, multicenter, parallel study sponsored by AbbVie. The registry lists enrollment of 304 adults with chronic hepatitis C virus infection and describes the study population as adults with genotype 2 infection. The study status is completed.

During the double-blind treatment period, Arm A received ABT-493/ABT-530, coformulated at 300 mg/120 mg once daily for 12 weeks. Arm B received matching placebo once daily for 12 weeks. The arm descriptions also list an open-label active-drug period for Arm B, during which participants received ABT-493/ABT-530 at the same stated dose and schedule. The registry record does not give further details about the transition between periods.

The primary efficacy population is narrower than the full study population: it includes participants randomized to and treated in the active-drug arm, excluding participants with prior failure of sofosbuvir plus ribavirin, with or without pegylated interferon. The primary endpoint description frames the analysis as noninferiority against a historical control rate for the stated standard of care, so the primary question is not described as a direct active-versus-placebo comparison.

The registry lists the study start as 2015-11 and primary completion as 2016-09. These dates describe the record’s study timeline; they do not provide the duration of follow-up for every participant. Although the study is marked completed, its posted record does not include numerical efficacy results for the primary endpoint. The record also does not report the noninferiority margin, the historical control rate used in the analysis, or a detailed statistical analysis plan.

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: A total of 304 subjects were randomized and 302 subjects received at least 1 dose of study drug.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All randomized participants who received at least one dose of study drug in Arm A DB excluding participants with prior SOF + RBV ± pegIFN failures.

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: All participants who received at least one dose of study drug.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants With Sustained Virologic Response 12 Weeks Post-treatment (SVR12) in Arm A DB Active Drug Excluding Prior SOF + Ribavirin (RBV) ± pegIFN Failures: Noninferiority Analysis, measured over 12 weeks after the last actual dose of active study drug.

The primary endpoint is the percentage of participants in the specified active-drug population who achieved sustained virologic response 12 weeks after the last actual dose of active study drug. The registry defines SVR12 by a plasma HCV RNA level below the lower limit of quantification at that assessment. The assessment is therefore a binary outcome for each participant: the participant either meets the stated criterion or does not.

As a general statistical point, a binary endpoint can be summarized as the proportion of participants meeting the criterion. That measure is directly interpretable as the share of the analysis population reaching the defined virologic threshold. Its precision depends on the number of participants included and the observed proportion; an interval estimate would show the range of values compatible with the data under the analysis assumptions. The registry record does not post the primary proportion or an interval estimate.

The stated objective is noninferiority against a historical control rate for patients treated with sofosbuvir plus ribavirin for 12 weeks. In general, a noninferiority analysis asks whether the treatment’s result is not unacceptably worse than a comparator by more than a prespecified margin. The margin and historical rate are not reported in the registry record. Without those quantities and the observed result, readers cannot evaluate the noninferiority conclusion from this record.

The endpoint’s timing is important to its interpretation: it concerns the post-treatment assessment specified as 12 weeks after the last actual dose, rather than response during treatment. The registry lists secondary outcomes related to SVR12, virologic failure during treatment, and relapse after treatment, but does not post their numerical results either.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a randomized, double-blind, parallel study with a placebo-controlled treatment period. Random allocation is intended, in general, to make assigned groups comparable on average at the start of a study, including with respect to factors that may not have been measured. Blinding is intended to reduce the chance that knowledge of treatment assignment influences care, reporting, or outcome assessment. These are general purposes of the design features; the registry record does not describe how randomization was generated, how allocation was concealed, or how blinding was maintained.

What does the primary endpoint summarize?

SVR12 is a binary endpoint: each participant either meets the registry’s HCV RNA criterion at the stated post-treatment assessment or does not. The endpoint is expressed as a percentage of participants, so its natural summary is the proportion meeting the criterion in the analysis population. A confidence interval, when reported, conveys uncertainty around that estimated proportion. A narrow interval indicates greater precision than a wide interval, although neither the interval nor the underlying primary estimate appears in the registry record.

The timepoint is specified as 12 weeks after the last actual dose of active study drug. This anchors the endpoint to treatment completion rather than to a fixed calendar date for every participant. The registry’s wording describes the primary population as active-arm participants who received at least one dose, with prior failures of sofosbuvir plus ribavirin, with or without pegylated interferon, excluded. This eligibility description matters because the result would apply to that defined group, not automatically to every enrolled participant.

How does noninferiority differ from a difference test?

In general, a noninferiority analysis evaluates whether a treatment’s result is sufficiently close to a reference result under a prespecified tolerance. That tolerance is the noninferiority margin. It must be defined before interpreting the result because it sets the largest disadvantage that would still be considered compatible with the study objective. The registry says the primary endpoint was assessed against a historical control rate, but the margin and the control rate are not reported in the registry record.

A result cannot be classified as meeting noninferiority from the endpoint definition alone. Interpretation needs the estimated treatment result, its uncertainty, the reference value, and the margin, together with the analysis approach. These details are not posted in the record. The record also does not report whether the primary analysis used a particular confidence-interval procedure, test statistic, or adjustment for covariates.

What is the role of the placebo arm?

The randomized double-blind period included active drug in Arm A and placebo in Arm B, while the primary endpoint description specifies comparison against a historical control. A direct randomized comparison and a historical-control comparison answer different statistical questions. The former uses concurrent randomized groups; the latter relies on a reference rate from outside the concurrent randomized comparison. The registry record does not provide enough detail to reconcile these two design elements beyond the endpoint description and arm schedule.

The record lists an open-label active-drug period for Arm B after its double-blind placebo period. Open-label means treatment is not blinded during that period. As a general matter, outcomes collected after treatment assignment is known can be subject to different sources of bias than outcomes collected under blinding. The registry record does not describe how such outcomes entered any efficacy analysis, and no results for the open-label period are posted.

How should planning calculations be read?

The sample-size illustrations are planning scenarios, not observed power. The stated calculation assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The scenarios express the effect to detect as a stated fraction of the observed effect. For binary outcomes, the illustrations are expressed as participants per arm; for time-to-event outcomes, the stated convention is total events. These calculations are conditional on their assumptions and do not reveal the trial’s actual design rationale.

In general, a planning calculation estimates the amount of information that would be needed for a specified statistical objective under chosen assumptions. It does not tell readers whether the observed data produced that amount of information, and it is not a substitute for an outcome estimate and confidence interval. The registry record does not report the trial’s own sample-size justification or the assumptions behind its design. The calculated illustrations on the page should therefore be treated as exploratory planning aids rather than as a statement of the trial’s planned or achieved power.

What statistical details remain unavailable?

The registry record does not report the noninferiority margin, historical control rate, primary outcome estimate, confidence interval, or primary test result. It does not give a detailed account of missing-data handling, analysis-set definitions beyond the stated primary population, sensitivity analyses, or multiplicity procedures. It also does not describe interim analyses. These omissions limit independent assessment of the statistical conclusion, even though the primary question and endpoint definition are stated.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Arm A DB Active Drug")
n      <- c(196)
events <- c(195)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Arm A DB Active Drug  196  195  99.5  97.2  100.0  97.2  99.9  97.2  99.9

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary endpoint and several secondary outcomes, including further SVR12 assessments, on-treatment virologic failure, and post-treatment relapse. When a study evaluates multiple outcomes or multiple analyses, multiplicity can increase the chance of a positive finding arising by chance across the set of tests. As a general statistical approach, study plans may address this by specifying a hierarchy, adjustment, or other control strategy. No such strategy is reported in the registry record, so it is not possible to say how multiplicity was handled.

The record identifies a primary efficacy population: active-arm participants who received at least one dose, excluding those with prior sofosbuvir plus ribavirin, with or without pegylated interferon, failure. It does not provide a complete account of analysis populations for all outcomes or explain whether the primary analysis followed any additional population definitions. The registry record also does not report how participants with missing SVR12 measurements were classified or handled, or whether any sensitivity analyses assessed the effect of missing data.

These omissions matter because a percentage depends on both the outcome classification and the denominator. If outcome status is unavailable for some participants, the analysis rule can affect the estimated response proportion and its uncertainty. This is a general point about binary outcomes; the record does not state how missing observations occurred or what assumptions were used.

The record does not report interim analyses or stopping rules, nor does it provide a detailed statistical analysis plan. Their presence or absence cannot be inferred from the registry summary. As a result, readers can identify the stated primary outcome and its described population, but cannot reconstruct the full analysis strategy or assess the impact of missing data and multiple testing from the posted record alone.

12. 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: rheumatoid arthritis (1.0%), haemorrhoids (0.5%), bile duct stone (0.5%), ankle fracture (0.5%), joint dislocation (0.5%).

The registry’s adverse-event summaries list 202 participants at risk in Arm A during the double-blind active-drug period, with 3 affected by serious adverse events and 75 affected by other adverse events. For the double-blind placebo group, it lists 100 at risk, 1 affected by a serious adverse event, and 38 affected by other adverse events. For the open-label active-drug group, it lists 100 at risk, 1 affected by a serious adverse event, and 31 affected by other adverse events. These are the posted group counts; they do not establish that treatment caused an event.

The listed serious-event terms include rheumatoid arthritis (1.0%), haemorrhoids (0.5%), bile duct stone (0.5%), ankle fracture (0.5%), and joint dislocation (0.5%). The record does not provide enough detail to interpret these terms as treatment-related, nor does it explain their timing or clinical context. Death counts are not reported in the registry record.

As a general point, serious adverse events and other adverse events are distinct registry categories, and counts alone do not show comparative risk or causation. The open-label active-drug group is listed separately from the double-blind groups, so its figures should not be treated as a direct randomized comparison with the placebo group. The record does not provide further information on event severity, attribution, or statistical comparison.

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

The registry record establishes that ENDURANCE-2 was designed to evaluate ABT-493/ABT-530 in adults with chronic hepatitis C virus genotype 2 infection, using a randomized, double-blind, placebo-controlled treatment period. It identifies SVR12 as the primary efficacy endpoint and describes a noninferiority objective against a historical control rate. It also lists the treatment schedules, the primary analysis population, secondary outcomes, and adverse-event counts.

What the record does not establish is the observed primary efficacy result. It does not post the SVR12 percentage, an uncertainty interval, the noninferiority margin, the historical control rate, or the analysis conclusion. Without these, readers cannot determine from the registry record whether the primary objective was met, how large the estimated response was, or how precisely it was estimated. The absence of posted results is not evidence that the treatment did or did not meet the objective.

The primary question applies to the specific active-arm population described in the record, excluding participants with the stated prior treatment failures. It should not be generalized beyond that population on the basis of the design description alone. The record also names a placebo arm and an open-label active-drug period, but the primary endpoint description is framed around a historical control, not a reported active-versus-placebo estimate. The posted information does not support substituting one comparison for the other.

The safety counts document events recorded in the listed groups, but they do not establish causation or provide a complete comparison of harms. In particular, the open-label group is listed separately, and the record does not give detailed event attribution or context. Counts and event terms should be read as descriptive registry information rather than proof of a treatment effect.

In short, the record provides useful information about what the trial asked and how its treatment periods were structured. It does not provide the outcome estimates needed to draw a statistical conclusion about efficacy or to quantify the precision of that conclusion.

14. Why This Trial Matters Statistically

This trial is statistically notable for the way its primary question is framed. It is a randomized, double-blind, placebo-controlled study, yet the primary endpoint description specifies a noninferiority assessment against a historical control rate. Those are distinct comparison frameworks: randomization supports comparison between concurrent groups, while a historical-control analysis depends on a reference rate from outside the concurrent treatment comparison. Understanding which comparison answers the primary question is essential to reading the design.

The endpoint is also defined for a specific analysis population rather than for every enrolled participant. Participants with prior failure of sofosbuvir plus ribavirin, with or without pegylated interferon, are excluded from the stated primary population. This restriction affects the scope of any primary result and would need to be kept in view if interpreting an estimate or comparing it with results from a different population.

As a general statistical issue, noninferiority depends on a prespecified margin and an estimate precise enough to evaluate that margin. The registry record identifies the noninferiority objective but does not report the margin, the historical control rate, or the outcome estimate. This makes the record a clear example of why design summaries alone cannot establish a statistical conclusion. A completed study status does not supply the missing result.

The record also illustrates why planned calculations, observed results, and observed power should not be conflated. Planning scenarios can show how sample-size requirements change under chosen assumptions, but they do not reveal the trial’s observed treatment effect or its precision. The stated calculations are illustrations, not the trial’s own design justification.

Finally, the listed placebo and open-label periods call for careful attention to the source and timing of outcome data. The record identifies these periods but does not provide a full analysis plan or explain how each contributed to efficacy analyses. The statistical lesson is to separate what the design intended to compare from what the posted results actually demonstrate; here, the latter are not reported.

15. 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 main trial-specific limitation of the posted record is the absence of numerical efficacy results. Although it defines SVR12 and states a noninferiority objective, it does not report the primary estimate, its uncertainty, or the conclusion. Readers therefore cannot assess the magnitude or precision of the primary result from this record.

The noninferiority framework is incompletely documented. The historical control rate and noninferiority margin are not reported in the registry record. Without them, even a posted response proportion would not be enough to reconstruct the primary decision. The record also does not state the statistical procedure used for that analysis.

The primary analysis population excludes participants with specified prior treatment failures and includes active-arm participants who received at least one dose. The record does not give the number included in this population, the number with an observed SVR12 assessment, or the handling of missing outcomes. It is therefore not possible to evaluate the analysis denominator or the consequences of missing data from the posted information.

The registry lists secondary outcomes but does not post their results or describe multiplicity control. It also does not report a full statistical analysis plan, interim analyses, or the trial’s sample-size justification. The open-label active-drug period is described, but the record does not explain how its data were used in efficacy analyses. These gaps limit the ability to reconstruct or independently assess the full analysis.

Safety information is also limited to group counts and selected serious-event terms. The record does not report death counts, event attribution, timing, or detailed context. The open-label group is not directly equivalent to a blinded randomized comparison. These limitations are specific to what is posted and should not be mistaken for proof that further analyses or information do not exist outside the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Study to Evaluate the Efficacy and Safety of ABT-493/ABT-530 in Adults With Chronic Hepatitis C Virus (HCV) Genotype 2 Infection — NCT02640482.
• Registry record last updated 2021-07-16; status last verified 2021-07.
• Results first posted 2017-09-18.
• 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.

19. Record Summary

ENDURANCE-2 is a completed, randomized, double-blind, placebo-controlled, parallel Phase 3 study sponsored by AbbVie. The registry lists enrollment of 304 adults with chronic hepatitis C virus genotype 2 infection. During the double-blind period, Arm A received ABT-493/ABT-530 once daily for 12 weeks and Arm B received placebo for 12 weeks; the record also describes an open-label active-drug period for Arm B.

The primary endpoint was the percentage achieving SVR12 in the active-arm population excluding participants with specified prior treatment failures. The stated objective was noninferiority against a historical control rate. The registry record does not report the primary efficacy result, the noninferiority margin, or the historical control rate. It lists secondary outcomes and safety counts, but does not provide numerical results for the efficacy outcomes or a full statistical analysis plan.