Study to Assess Efficacy and Safety of Bulevirtide in Participants With Chronic Hepatitis Delta (CHD): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study to Assess Efficacy and Safety of Bulevirtide in Participants With Chronic Hepatitis Delta (CHD) (NCT03852719), a randomized phase 3 study. The primary outcome is Percentage of Participants With Combined Response at Week 48.

2. Clinical Question

The registry describes a multicenter, randomized, open-label, parallel-group Phase 3 study. It lists 150 participants enrolled. The primary outcome is a percentage, so its reported values describe the proportion meeting the combined definition in each randomized group. The comparison is specific to the Week 48 assessment; it does not by itself answer whether later outcomes persisted after treatment or whether changes in liver stiffness occurred.

3. Trial Design

This was a randomized, open-label, parallel-group Phase 3 clinical study sponsored by Gilead Sciences. The registry lists 150 participants enrolled and chronic hepatitis delta as the condition. Masking was listed as none. The listed treatment arms were delayed treatment, bulevirtide 2 mg/day, and bulevirtide 10 mg/day.

The main comparison was planned around 48 weeks: the study description states that bulevirtide at either dose was compared with delayed treatment over that period. The arm descriptions state that the two bulevirtide groups were assigned treatment through Week 144, followed by up to 96 weeks of follow-up. Participants in the delayed-treatment group had an observational period of 48 weeks, then received bulevirtide 10 mg/day for 96 weeks, with follow-up described through Week 240. The brief study description also says all participants would be followed off-treatment for an additional 96 weeks.

The primary outcome was assessed at Week 48. The Full Analysis Set included participants randomized to delayed treatment or to bulevirtide who received bulevirtide at least once after randomization; participants were analyzed according to randomized treatment. The registry record does not report the original sample-size justification, the detailed randomization procedure, the full statistical analysis plan, or whether interim analyses were planned or conducted. Those details should not be inferred from the phase, allocation, or enrollment information.

The registry status is completed. Its outcome record includes 11 outcome measures and 15 analyses. The primary result is a combined response; secondary outcomes include separate virologic and ALT measures, liver stiffness measurements at several follow-up times, and sustained virological response. The longer-term treatment schedule means that later comparisons do not represent the same treatment contrast as the initial Week 48 comparison.

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: 183 participants were screened.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The Full Analysis Set included participants randomized to delayed treatment arm or randomized to bulevirtide and received bulevirtide at least once after randomization. Participants were grouped according to randomized treatment. The arm titles and descriptions in this outcome measure are entered accordingly.

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: The Full Analysis Set (FAS) included all participants who were randomized to bulevirtide and took at least 1 dose of bulevirtide and those who were randomized to delayed treatment group.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants With Combined Response at Week 48, measured over Week 48.

The primary endpoint is the percentage of participants with a combined response at Week 48. The definition requires both conditions to be met at the same time: HDV RNA must be undetectable, with target not detected below the lower limit of quantification, or show a decrease of at least 2 log10 IU/mL from baseline; and ALT must normalize. A participant meeting only one condition does not meet the combined definition.

A combined endpoint can represent response across two distinct aspects of disease measurement. In this case, it joins a virologic criterion with a biochemical criterion. Requiring both makes the endpoint more restrictive than either component alone, so the reported percentage should not be read as the percentage meeting either criterion separately. The registry also posts separate Week 48 outcomes for undetectable HDV RNA and ALT normalization, which help describe the components, but those do not replace the joint primary endpoint.

The endpoint is expressed as a percentage of participants rather than as a continuous change score. Its meaning depends on the registry’s operational definitions, including the threshold for the viral RNA response and the criterion for ALT normalization. The record gives the combined-response definition, but does not report further details about how borderline or missing measurements were handled. The result describes response status at Week 48; it is not, on its own, a measure of durability after treatment or of later clinical outcomes.

7. Results Posted in the Registry

• Bulevirtide 2 mg/Day: 44.9% (22/49) versus 2.0% (1/51) on control; risk difference 42.9 percentage points (95% CI 28.5 to 57.4), risk ratio 22.90 (3.21–163.42); unadjusted two-proportion z-test p = <0.001.
• Bulevirtide 10 mg/Day: 48.0% (24/50) versus 2.0% (1/51) on control; risk difference 46.0 percentage points (95% CI 31.7 to 60.4), risk ratio 24.48 (3.44–174.14); unadjusted two-proportion z-test p = <0.001.

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 With Undetectable HDV RNA at Week 48

• 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:
  • Bulevirtide 2 mg/Day: 12.2% (6/49) versus 0.0% (0/51) on control; risk difference 12.2 percentage points (95% CI 3.1 to 21.4); unadjusted two-proportion z-test p = 0.010.
  • Bulevirtide 10 mg/Day: 20.0% (10/50) versus 0.0% (0/51) on control; risk difference 20.0 percentage points (95% CI 8.9 to 31.1); unadjusted two-proportion z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for Bulevirtide 2 mg/Day than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for Bulevirtide 10 mg/Day than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Percentage of Participants With Alanine Aminotransferase (ALT) Normalization at Week 48

• 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:
  • Bulevirtide 2 mg/Day: 51.0% (25/49) versus 11.8% (6/51) on control; risk difference 39.3 percentage points (95% CI 22.7 to 55.8), risk ratio 4.34 (1.95–9.65); unadjusted two-proportion z-test p = <0.001.
  • Bulevirtide 10 mg/Day: 56.0% (28/50) versus 11.8% (6/51) on control; risk difference 44.2 percentage points (95% CI 27.9 to 60.6), risk ratio 4.76 (2.16–10.50); unadjusted two-proportion z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for Bulevirtide 2 mg/Day than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for Bulevirtide 10 mg/Day than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Percentage of Participants With Undetectable HDV RNA 24 Weeks After Scheduled End of Treatment (Sustained Virological Response)

• 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:
  • Bulevirtide 10 mg/Day: 26.0% (13/50) versus 18.4% (9/49) on control; risk difference 7.6 percentage points (95% CI -8.7 to 23.9), risk ratio 1.42 (0.67–3.01); unadjusted two-proportion z-test p = 0.361.
  • Delayed Treatment/Bulevirtide 10 mg/Day: 18.0% (9/50) versus 18.4% (9/49) on control; risk difference -0.4 percentage points (95% CI -15.6 to 14.8), risk ratio 0.98 (0.42–2.26); unadjusted two-proportion z-test p = 0.962.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Bulevirtide 10 mg/Day and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Delayed Treatment/Bulevirtide 10 mg/Day and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcomes cover separate Week 48 measures of undetectable HDV RNA and ALT normalization, as well as sustained virological response after scheduled treatment and liver stiffness assessments at multiple follow-up times. These outcomes help place the combined primary response in context: the primary definition requires both a virologic response and ALT normalization, while the secondary measures separate those components or address different measurements and follow-up periods.

At Week 48, the posted arm percentages for undetectable HDV RNA and ALT normalization are higher in each bulevirtide group than in delayed treatment. These separate component outcomes do not guarantee a combined response for an individual, because the primary definition requires both conditions simultaneously. The later sustained-response outcome is assessed at Week 168, after treatment schedules have diverged and treatment has ended for the relevant groups. It therefore addresses a different question from the initial Week 48 comparison. Liver stiffness outcomes are also distinct from response percentages and are measured at several later time points.

Secondary analyses are generally less definitive than a single primary analysis when many outcomes, time points, or comparisons are examined. Testing multiple hypotheses increases the chance that at least one apparently notable result could arise by chance. The registry record does not report whether a multiplicity adjustment was planned or applied to secondary analyses. Unless such control is documented, secondary p-values should be treated as exploratory evidence rather than as confirmatory findings. The posted estimates remain useful for describing patterns and uncertainty, but they do not carry the same interpretive weight as the designated primary endpoint.

The registry lists 11 outcome measures and 15 analyses. The presence of several outcome measures underscores why a single nominal p-value should not be interpreted in isolation. The detailed protocol for ranking outcomes, controlling multiplicity, and handling repeated measurements is not reported in the registry record.

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

• Percentage of Participants With Undetectable HDV RNA at Week 48
• Percentage of Participants With Alanine Aminotransferase (ALT) Normalization at Week 48
• Change From Baseline in Liver Stiffness, as Measured by Elastography at Week 48
• Change From Baseline in Liver Stiffness, as Measured by Elastography at Week 96
• Change From Baseline in Liver Stiffness, as Measured by Elastography at Week 144
• Change From Baseline in Liver Stiffness, as Measured by Elastography at Week 192
• Change From Baseline in Liver Stiffness, as Measured by Elastography at Week 240
• Percentage of Participants With Undetectable HDV RNA 24 Weeks After Scheduled End of Treatment (Sustained Virological Response)

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary at the participant level: each participant either meets the combined-response definition at Week 48 or does not. The arm-level result is presented as a percentage. The risk difference compares the response proportions between two groups by subtracting one proportion from the other; its direction depends on the order of the groups. The posted recalculated risk differences use the delayed-treatment group as the reference and are expressed as proportions, not as percentages.

What does a confidence interval describe?

General statistical explanation: A confidence interval gives a range of values compatible with the observed data under the interval’s statistical method. It conveys estimation uncertainty, not the range of individual participant outcomes and not the probability that the true value lies in the particular interval. Wider intervals indicate less precision than narrower intervals, all else being comparable. The registry reports 95% intervals for arm percentages and the recalculated comparisons; its primary sponsor analyses report 96% intervals for differences in percentages.

What does the p-value address?

General statistical explanation: A p-value describes how unusual data at least as incompatible with a specified null hypothesis would be if that hypothesis and the test assumptions held. It is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. The recalculated primary comparisons report p < 0.001. The registry’s reported Fisher Exact analyses give p < 0.001. These values are evidence against a no-difference null in the respective analyses, but they do not capture uncertainty about every design or analysis choice.

Why can a binary endpoint be analyzed in different ways?

General statistical explanation: A group comparison can be expressed as a difference in response proportions, a relative risk, an odds ratio, or a test of association. These measures answer related but not identical questions. A risk difference expresses an absolute contrast on the proportion scale; relative measures compare the groups multiplicatively. When events are uncommon or group sizes are limited, estimates of relative measures can be especially imprecise. The posted primary recalculation emphasizes risk differences, while the registry reports Fisher Exact analyses of differences in percentages.

What is Fisher Exact?

General statistical explanation: Fisher Exact is a method for testing association in a two-by-two arrangement of event and non-event counts across two groups. It calculates probabilities under a null model rather than relying on a large-sample normal approximation for the test. The registry identifies Fisher Exact as the method for its reported primary comparisons. The record does not provide enough detail to reconstruct all choices used for its confidence intervals or any additional adjustments.

What does unadjusted mean?

General statistical explanation: An unadjusted comparison uses the observed group outcomes without controlling for other variables. It is straightforward to interpret as a group-level contrast, but it does not account for possible imbalances in participant characteristics or other covariates. The recalculated values are unadjusted re-calculations from posted summary statistics. The registry’s full modeling choices beyond the analyses it reports are not reported in the registry record.

Why does the outcome definition matter?

General statistical explanation: A composite or combined endpoint counts a response only when all required components are satisfied. Its result can differ from results for the individual components because each component may have a different response pattern. Here, the combined endpoint requires a virologic criterion and ALT normalization. Separate secondary results for those outcomes are informative about the components, but they cannot be substituted for the primary combined response.

Interpretation also depends on who is included in the analysis. The Full Analysis Set definition includes randomized participants who received bulevirtide at least once after randomization, with participants grouped according to randomized treatment. This is the population definition stated for the primary outcome. The registry does not report further information about exclusions, missing outcome handling, imputation, or sensitivity analyses for the primary endpoint.

11. Confidence Intervals and Precision

The primary arm estimates are based on 51 participants in delayed treatment, 49 in bulevirtide 2 mg/day, and 50 in bulevirtide 10 mg/day. The corresponding combined-response percentages are 2.0%, 44.9%, and 48.0%. Their 95% confidence intervals are 0.0 to 10.4, 30.7 to 59.8, and 33.7 to 62.6. The intervals express uncertainty in each arm’s estimated percentage; they do not imply that the true value is equally likely to be any point within the interval.

For the recalculated risk differences, the 95% confidence interval is 0.285 to 0.574 for bulevirtide 2 mg/day versus delayed treatment, and 0.317 to 0.604 for bulevirtide 10 mg/day versus delayed treatment. Both intervals exclude zero, the value corresponding to no difference on the risk-difference scale. The registry’s own reported analyses use a different presentation: a 96% confidence interval for each difference in percentages. Those reported intervals are 27.0 to 58.5 for the 2 mg/day comparison and 30.5 to 61.4 for the 10 mg/day comparison.

Precision is limited by the size of the groups and the number of observed responses, particularly in the delayed-treatment group. A percentage based on relatively few events can change noticeably with a small change in the event count. The intervals are therefore important alongside the point estimates. The two active-group estimates are also close relative to their uncertainty, and the reported primary comparisons do not directly test one active dose against the other.

General statistical explanation: Confidence intervals describe uncertainty under their statistical assumptions. They do not account for every possible source of uncertainty, such as missing-data decisions, endpoint measurement issues, or selective reporting. The registry record does not report enough detail to assess those aspects fully.

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 sample-size figures are planning illustrations based on the observed effect, not the trial’s original design justification. For these binary outcomes, the entries are participants per arm, not total events. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is defined as a stated fraction of the observed effect.

The 80% power column gives the estimated participants per arm under those assumptions for a design with an 80% chance of detecting the specified effect if that effect were true. The 90% power column gives the corresponding planning count for a 90% chance. In ordinary terms, greater planned power means a greater chance of detecting the assumed effect, but it generally requires a larger planned sample. These are planning quantities, not observed power.

Rows for 100%, 75%, and 50% of the observed effect illustrate how the planning count changes when the assumed target effect is reduced. A smaller effect is harder to distinguish from random variation, so it requires more participants under otherwise comparable assumptions. The observed effect is not guaranteed to recur in another study, and using it as a planning input can yield optimistic illustrations when the observed estimate is imprecise.

The registry record does not report the original sample-size justification or confirm that these planning assumptions were used to design the trial. The illustrations should therefore be read as conditional calculations tied to their stated assumptions, not as evidence about the trial’s design adequacy or the probability that its observed result is correct.

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 = 0.020; treatment proportion p₁ = 0.449; average p̄ = 0.234.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.5990 = 1.1740.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5164 = 0.4346.
4. n = (1.1740 + 0.4346)² / (0.4294)² = 14.0, rounded up to 15 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 <- 0.0196078431372549                          # control proportion
p1 <- 0.448979591836735                          # 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(3852719)
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 = 15 (80% power), 19 (90% power)
 75% of observed effect: n per arm = 22 (80% power), 28 (90% power)
 50% of observed effect: n per arm = 37 (80% power), 49 (90% power)
power.prop.test: 14 
Simulated power at n = 15 per arm: 0.896 (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’s reported primary analyses use Fisher Exact and present differences in percentages. For bulevirtide 10 mg/day versus delayed treatment, the reported difference is 46.0, with a 96% confidence interval from 30.5 to 61.4 and p < 0.001. For bulevirtide 2 mg/day versus delayed treatment, the reported difference is 42.9, with a 96% confidence interval from 27.0 to 58.5 and p < 0.001.

The simple recalculations use the posted event counts and group sizes to estimate unadjusted risk differences. They report 0.460 for the 10 mg/day comparison and 0.429 for the 2 mg/day comparison, with 95% confidence intervals and p < 0.001 for each. The registry’s analyses and the recalculations are different presentations and use different stated confidence levels; the values should not be compared without keeping those distinctions in mind. The registry record does not flag a discrepancy.

The sponsor’s analysis is the registry-reported analysis. The recalculation is a transparent, unadjusted check based on summary counts and does not replace the sponsor’s analysis or reproduce any unreported model or analysis choices. The record does not give enough detail to reconcile every methodological difference between the reported and recalculated intervals.

15. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when a study examines several outcomes, time points, or group comparisons. Even when each statistical test uses a conventional threshold, the chance of at least one false positive across a collection of tests can be greater than for a single test. Common approaches include designating a primary hypothesis, adjusting thresholds, or using a hierarchical testing plan. The registry identifies a primary outcome and posts multiple secondary measures and analyses, but a multiplicity strategy is not reported in the registry record. It cannot be assumed that adjustment was or was not used in analyses beyond what the record states.

The primary population is defined as the Full Analysis Set, including participants randomized to delayed treatment or bulevirtide who received bulevirtide at least once after randomization, analyzed according to randomized treatment. This definition helps establish which participants contribute to the primary outcome. However, the record does not report the number with missing Week 48 outcome data, the reasons for missingness, or whether missing values were imputed or treated as non-response. It also does not describe sensitivity analyses assessing alternative missing-data assumptions.

Missingness matters because participants without an observed endpoint may differ from those with an observed endpoint. The effect of missing data depends on how much is missing, why it is missing, and the analysis approach. Without the relevant details, the registry percentages should be interpreted as posted results for the stated analysis population, not as proof that missing data could not affect the estimates.

The record also does not report the detailed statistical analysis plan, adjustment covariates, interim-analysis procedures, or whether any changes to planned analyses occurred. These omissions limit assessment of prespecification and robustness. They do not invalidate the reported results, but they constrain how fully readers can evaluate the analysis process and the strength of confirmatory claims.

16. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hepatitis d (8.7%), covid-19 pneumonia (4.0%), anaemia (2.2%), oesophageal varices haemorrhage (2.2%), hepatitis acute (2.2%).

The registry reports serious adverse events and other adverse events by treatment period and group. From baseline to Week 48, serious adverse events were reported for 1 of 51 participants in delayed treatment, 2 of 49 in bulevirtide 2 mg/day, and 1 of 50 in bulevirtide 10 mg/day. The registry reports zero deaths in each of those groups for that period. The corresponding counts for other adverse events were 30, 35, and 41 participants.

Later periods have different exposure and follow-up windows. The registry reports serious-event counts of 3 in the 2 mg/day group and 6 in the 10 mg/day group from baseline to Week 144; for the delayed-treatment/bulevirtide 10 mg/day period from Week 48 to Week 144, it reports 3 serious events and 1 death. After end of treatment, the listed serious-event counts are 7, 7, and 8 across the three stated groups, with zero deaths in those groups.

These are counts of participants with events in the listed periods, not estimates of comparative risk adjusted for exposure or follow-up. The registry lists serious-event terms including Hepatitis D, Covid-19 pneumonia, Anaemia, Oesophageal varices haemorrhage, Hepatitis acute, and Hepatocellular carcinoma, with percentages. It does not provide enough information in this record to attribute those listed terms to a specific arm or assess causal relationships. Safety counts should be read descriptively and separately from efficacy outcomes.

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

The Week 48 result describes the proportion of participants meeting the registry’s combined definition in each randomized group. The posted combined-response percentage was higher in each bulevirtide group than in the delayed-treatment group, and the recalculated risk-difference intervals excluded zero. The result is evidence of a group-level difference for this particular endpoint and assessment time under the analyses reported.

It does not mean that every participant in a bulevirtide group met the response definition, or that no participant in delayed treatment did. It does not establish a dose difference: the primary analyses compare each dose with delayed treatment, not the two bulevirtide doses directly. Similar observed response percentages in the active groups are not proof that the doses are equivalent, because equivalence requires a prespecified margin and an appropriate analysis, neither of which is reported in the registry record.

The endpoint is not a direct measure of every aspect of health or disease progression. It combines an HDV RNA criterion and ALT normalization at Week 48. A response on this definition does not, by itself, establish lasting response after treatment, changes in liver stiffness, or effects on outcomes that the registry does not report. Longer-term observations and secondary outcomes address some different questions but have their own uncertainties and treatment contrasts.

Statistical evidence is not the same as a clinical recommendation. These results do not determine whether a treatment is appropriate for any particular person. The registry record also does not supply enough information to evaluate all details of missing-data handling, multiplicity control, or the original design assumptions. Those limits matter when judging how broadly and confidently the posted estimates can be interpreted.

18. Why This Trial Matters Statistically

This trial illustrates how a registry result can combine a clearly defined binary endpoint with several layers of statistical interpretation. The primary outcome is not simply one laboratory measure: it requires a virologic response and ALT normalization at the same time. That makes the estimand—the precise quantity being compared—important. Separate component outcomes can help explain the pattern, but they answer different questions from the combined endpoint.

The result also shows why point estimates should be read with confidence intervals and group sizes. The percentages summarize observed group outcomes, while intervals communicate uncertainty around those estimates. Multiple presentations of the comparison, including a difference in percentages and an unadjusted risk difference, can be informative, but the confidence level and method must be kept clear. The sponsor-reported Fisher Exact analyses and simple recalculations are related evidence, not identical analyses.

Longer follow-up adds another statistical issue: the groups’ treatment schedules change after Week 48. Later comparisons therefore cannot be interpreted as a continuation of the original delayed-treatment contrast without considering the treatment switch and follow-up periods. Secondary outcomes and safety counts likewise differ in definition, timing, and exposure context.

Finally, the record demonstrates the value of distinguishing reported details from unreported design details. The registry identifies the randomized open-label design, primary endpoint, analysis population, and posted comparisons, while leaving the original sample-size justification, multiplicity plan, and missing-data approach unreported. Recognizing those boundaries supports a careful reading of the numerical findings without overstating what the record can establish.

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 registry record leaves several trial-specific details unavailable for independent assessment. It does not report the original sample-size justification, the detailed statistical analysis plan, the randomization procedure, or whether interim analyses were planned or conducted. It also does not report a multiplicity strategy for the set of secondary outcomes and analyses. These gaps limit assessment of prespecification and the strength of confirmatory interpretation.

The primary analysis population is described, but the record does not provide detailed information about missing Week 48 measurements, participant-level exclusions, imputation, or sensitivity analyses. As a result, the potential influence of missing outcomes cannot be evaluated from the posted record alone. The recalculated comparisons are unadjusted and use summary counts; they cannot account for covariates or reproduce unreported sponsor methods.

The study is open-label, with no masking listed. This does not by itself establish bias, but awareness of treatment assignment can be relevant to some aspects of care, measurement, and reporting. The primary endpoint includes laboratory-based criteria, but the registry record does not report enough procedural detail to assess all possible measurement influences.

Longer-term results require particular care because participants assigned to delayed treatment changed to bulevirtide after Week 48, while the other groups received treatment from the outset. Post-treatment follow-up also occurs after different treatment histories. These periods do not preserve a simple untreated comparator. The registry provides selected outcome results and adverse-event summaries, but does not contain the full participant-level data needed to assess alternative analyses, subgroup patterns, or all sources of uncertainty.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Study to Assess Efficacy and Safety of Bulevirtide in Participants With Chronic Hepatitis Delta (CHD) — NCT03852719.
• Registry record last updated 2025-08-22; status last verified 2025-08.
• Results first posted 2022-10-28.
• 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

The registry record describes a completed, randomized, open-label, parallel-group Phase 3 study of bulevirtide in chronic hepatitis delta, with 150 participants enrolled. The primary endpoint was the percentage meeting a combined HDV RNA and ALT response definition at Week 48. The posted percentages were 2.0% for delayed treatment, 44.9% for bulevirtide 2 mg/day, and 48.0% for bulevirtide 10 mg/day.

The recalculated unadjusted risk differences versus delayed treatment were 0.429 and 0.460, respectively, with both 95% confidence intervals excluding zero. The registry’s own Fisher Exact analyses reported differences in percentages of 42.9 and 46.0, with p < 0.001 for both comparisons. Secondary outcomes and safety counts cover additional measures and follow-up periods, but require separate interpretation. The record does not report the original sample-size justification, full statistical plan, multiplicity approach, or detailed missing-data methods.