This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for A Study to Evaluate Efficacy and Safety of VX-864 in Participants With the PiZZ Genotype (NCT05643495), a non-randomized phase 2 study. The primary outcome is Change in Blood Functional Alpha-1 Antitrypsin (AAT) Levels.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05643495 |
| Phase | Phase 2 |
| Condition | Alpha-1 Antitrypsin Deficiency |
| Allocation | Non-Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 14 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Vertex Pharmaceuticals Incorporated |
| Results posted | Yes |
2. Clinical Question
Population
The study enrolled participants with alpha-1 antitrypsin deficiency who had the PiZZ genotype. The registry record lists enrollment as 14. It does not report further eligibility details in the information available for this analysis.
Intervention
Participants received VX-864 every 12 hours. Group A was scheduled to continue dosing for 48 weeks or until study drug dosing was terminated. The study was open-label, so masking was not used.
Comparator
There was no randomized control group. The study used a nonrandomized, parallel design with two groups. Group B had liver biopsies before treatment and again at Week 24 or Week 48; Group A did not have this biopsy schedule described.
Primary question
The primary endpoint asked how blood functional alpha-1 antitrypsin levels changed from baseline at Week 48. The registry record states that no data were collected for this endpoint because dosing was terminated before any participant reached Week 48. Consequently, the record cannot answer the planned primary question.
3. Trial Design
This was a Phase 2, open-label, nonrandomized, parallel study of VX-864 in participants with alpha-1 antitrypsin deficiency and the PiZZ genotype. The registry record lists enrollment as 14 and gives the study status as terminated. It records a start date of 2023-02-23 and a primary completion date of 2024-08-19. The reason for termination is not reported in the registry record.
Both groups were assigned VX-864 every 12 hours, with treatment intended to continue for 48 weeks or until dosing was terminated. Group B had a liver biopsy before treatment and a second biopsy at Week 24 or Week 48. The record describes the groups differently in this respect, but does not establish a randomized or like-for-like comparison. The safety listings identify Group A and Group B as VX-864 500 mg groups; that designation does not create a control group.
Because the study was open-label, participants and study personnel were not masked to treatment assignment. Because allocation was nonrandomized, differences between the groups could reflect factors other than treatment or biopsy schedule. The registry record does not report the allocation procedure, baseline characteristics, or a protocol rationale for the group structure. Most importantly for interpreting efficacy, the primary Week 48 measure was not collected: dosing ended before any participant reached that endpoint time. The design therefore describes a planned treatment study, but the posted record does not contain a Week 48 primary outcome result.
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 14 participants were enrolled from 23 February 2023 to 03 November 2023 in this study. Study drug dosing and efficacy assessments were terminated early due to Sponsor decision, therefore evaluation of efficacy outcome measure was not completed.
Overall Study
| Stage | Group A VX-864 500 mg | Group B VX-864 500 mg |
|---|---|---|
| STARTED | 10 | 4 |
| COMPLETED | 9 | 2 |
| NOT COMPLETED | 1 | 2 |
Reasons for not completing this period:
| Reason | Group A VX-864 500 mg | Group B VX-864 500 mg |
|---|---|---|
| Adverse Event | 0 | 1 |
| Withdrawal of consent (not due to AE) | 1 | 1 |
Analysis population for the primary outcome, as defined in the registry: Data was not collected for this Outcome Measure as the study drug dosing was terminated prior to any participant reaching Week 48.
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) is defined as all enrolled participants who have received at least 1 dose of study drug.
| Characteristic | Unit | Group A VX-864 500 mg | Group B VX-864 500 mg | Total |
|---|---|---|---|---|
| Participants analysed | 10 | 4 | 14 | |
| Age, Continuous | years | 52.8 (SD 14.2) | 50.8 (SD 10.4) | 52.2 (SD 12.9) |
| Sex: Female, Male: Female | Participants | 8 | 3 | 11 |
| Sex: Female, Male: Male | Participants | 2 | 1 | 3 |
| Race/Ethnicity, Customized: White | Participants | 10 | 4 | 14 |
| Race/Ethnicity, Customized: Not Hispanic or Latino | Participants | 10 | 4 | 14 |
6. Primary Endpoint
The registry lists the primary outcome as Change in Blood Functional Alpha-1 Antitrypsin (AAT) Levels, measured over From Baseline at Week 48.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint was change in blood functional alpha-1 antitrypsin (AAT) levels from baseline at Week 48. It was intended to quantify the change in the functional form of AAT in blood over the treatment period. The registry also lists blood antigenic AAT and blood Z-polymer levels among secondary outcomes, distinguishing those measures from the primary functional measure.
General explanation: a functional measurement describes activity or function, while an antigenic measurement concerns the presence of a substance recognized by an assay. Using both kinds of measure can address different aspects of a biological response; they are not interchangeable endpoints. The registry record does not provide a detailed assay description or explain the endpoint-selection rationale, so the specific measurement procedures and reasons for choosing Week 48 are not reported in the registry record.
The planned endpoint cannot be interpreted as an observed change. The record explicitly says data were not collected because study drug dosing was terminated before any participant reached Week 48. It reports no estimate of change, variability, confidence interval, or statistical test for this primary measure. Thus, the endpoint’s clinical or statistical pattern cannot be assessed from the posted results.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central result for the planned primary question is the absence of a Week 48 measurement. The primary endpoint was change in blood functional AAT from baseline at Week 48, but the registry record states that dosing was terminated before any participant reached Week 48 and that data were not collected. This is not a result showing no change; it is an unavailable outcome. No direction or size of the Week 48 effect can be inferred.
The registry record lists six outcome measures and no outcome analyses. It names secondary measures involving blood functional AAT, blood antigenic AAT, blood Z-polymer, liver Z-polymer accumulation in Group B, and adverse events and serious adverse events. The record does not give quantitative results for the biochemical outcomes in the information available for this analysis. Without estimates and measures of uncertainty, no comparison of response magnitude or precision can be made for those outcomes.
The safety listings report serious adverse events for 1 of 10 participants at risk in Group A and 0 of 4 participants at risk in Group B. Other adverse events were reported for 10 of 10 at risk in Group A and 4 of 4 at risk in Group B. Deaths were recorded as 0 in each group. The registry lists diverticulitis at 10.0% among the top serious terms. These are descriptive safety counts, not evidence that VX-864 caused or prevented any event. The nonrandomized design and absence of a control group also prevent a like-for-like treatment comparison.
The open-label, terminated study therefore offers limited grounds for estimating efficacy. Its planned primary endpoint is unavailable, the reported safety counts do not establish causality, and the registry record does not supply an inferential analysis. Any planning calculations based on observed effects should be understood as illustrations under stated assumptions, not as observed power or confirmation of an effect. The posted information is best read as a record of the design, termination, and available safety counts rather than as a completed estimate of the primary treatment effect.
9. Statistical Methods Explained
Statistical interpretation depends first on what was measured and when. The primary outcome was defined as change in blood functional AAT from baseline at Week 48. Since dosing was terminated before any participant reached Week 48, the registry record reports no collected data for that outcome. No statistical method can recover a Week 48 measurement that was not collected without additional assumptions and information. The record does not report an imputation method or an alternative primary time point.
What does a confidence interval describe?
General explanation: a confidence interval describes uncertainty around an estimated quantity under a specified statistical model and analysis procedure. It is not a guarantee that the true effect lies within the displayed interval, and its width is influenced by the amount and variability of information available. For this study’s primary endpoint, there is no reported Week 48 estimate or interval to interpret. The absence of an interval is not evidence of a precise zero effect; it reflects that the endpoint data were not collected.
Why does the design matter?
The trial was nonrandomized and had no like-for-like control comparison. In a randomized comparison, assignment is designed to balance measured and unmeasured participant characteristics on average. Without random assignment, group differences can be associated with baseline characteristics, care, or other factors as well as treatment. This limitation applies even when groups receive the same named intervention. The registry record does not report adjusted outcome analyses that might address measured differences, and it provides no primary outcome data to analyze in any case.
The study was also open-label, meaning masking was not used. General explanation: awareness of assignment can influence behavior, reporting, or assessment, particularly for outcomes that rely on judgment or participant reporting. The record does not describe blinded outcome assessment, so whether any assessment was independently masked is not reported in the registry record.
How should planning calculations be read?
General explanation: sample-size calculations estimate the amount of information a future study might need under assumptions about the effect to detect, variability, significance level, allocation, and analysis method. The planning illustration associated with this study uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is expressed as a stated fraction of an observed effect. Such calculations are conditional illustrations, not evidence that the study had a particular probability of finding a result. They are not observed power.
The illustration is not the trial’s own design justification. The registry record does not report a sample-size justification, and the nonrandomized groups should not be treated as a randomized comparison for interpreting such planning scenarios. If a calculation is based on an observed effect from posted data, its relevance depends on what outcome and analysis produced that effect. The primary Week 48 result is unavailable, so it cannot serve as an observed primary effect. The registry record does not identify an effect estimate for the planning illustration in the information available for this analysis.
General explanation: calculations based on a normal approximation rely on assumptions about the sampling distribution of the estimate. For event-time outcomes, the stated Schoenfeld approach concerns the total number of events needed, whereas other planning calculations are expressed as participants per arm. The listed outcomes do not establish that every calculation applies to every endpoint. The registry record does not describe an event-time primary endpoint.
What can descriptive safety counts establish?
Counts of participants with events describe what was recorded in the listed groups. They do not, by themselves, estimate a causal treatment effect. A comparison of event proportions would be particularly difficult to interpret in this nonrandomized study without details about participant characteristics, observation time, event definitions, and handling of follow-up. The registry record does not provide those details in the information available for this analysis. The safety counts should therefore be read as descriptive registry data, not as a test of safety differences.
Finally, no inferential analysis is listed for the outcome measures. There are no reported estimates, standard errors, confidence intervals, or p-values for the primary endpoint in the posted results. Any statistical explanation must preserve that distinction: methods can describe how an analysis might be conducted, but they cannot substitute for the absent Week 48 observations.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists multiple outcomes, including several measures of AAT and Z-polymer levels, a liver measure for Group B, and safety outcomes. When a study examines multiple outcomes or time points, the chance of at least one apparently noteworthy result can increase if each is tested independently. General explanation: multiplicity procedures can control the overall error rate or organize analyses hierarchically, but the choice depends on the study’s prespecified questions and analysis plan. A multiplicity strategy is not reported in the registry record.
The record lists no outcome analyses. In particular, it reports no Week 48 primary endpoint data because study drug dosing ended before any participant reached that time. The reason for termination is not reported in the registry record, and there is no reported interim-analysis plan or information about whether interim analyses occurred.
The endpoint’s unavailability should be distinguished from a reported analysis of missing individual values. The registry record says no data were collected for the primary outcome because no participant reached the specified time point; it does not describe imputation, sensitivity analyses, or another method for addressing missing outcome data. Those methods are not reported in the registry record.
The analysis population is also not reported in the registry record. The safety listings identify the participants at risk for those outcomes, but those counts do not establish which population would have been used for efficacy analyses. Definitions such as intention-to-treat, per-protocol, or a safety population are not reported in the registry record. Without these details, the analysis set and handling of incomplete follow-up cannot be evaluated.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Group A VX-864 500 mg | 1 | 10 | 10.0% |
| Group B VX-864 500 mg | 0 | 4 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Group A VX-864 500 mg | 0 of 10 |
| Group B VX-864 500 mg | 0 of 4 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Group A VX-864 500 mg | 10 of 10 |
| Group B VX-864 500 mg | 4 of 4 |
Most frequent serious adverse event terms
| Event term | Organ system | Group A VX-864 500 mg | Group B VX-864 500 mg |
|---|---|---|---|
| Diverticulitis | Infections and infestations | 1 of 10 | 0 of 4 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Group A VX-864 500 mg | Group B VX-864 500 mg |
|---|---|---|---|
| Nausea | Gastrointestinal disorders | 3 of 10 | 2 of 4 |
| Diarrhoea | Gastrointestinal disorders | 2 of 10 | 2 of 4 |
| Photosensitivity reaction | Skin and subcutaneous tissue disorders | 3 of 10 | 0 of 4 |
| Vomiting | Gastrointestinal disorders | 1 of 10 | 1 of 4 |
| Blood creatine phosphokinase increased | Investigations | 1 of 10 | 1 of 4 |
| Arthralgia | Musculoskeletal and connective tissue disorders | 1 of 10 | 1 of 4 |
| Dizziness | Nervous system disorders | 2 of 10 | 0 of 4 |
| Blister | Skin and subcutaneous tissue disorders | 2 of 10 | 0 of 4 |
| Porphyria non-acute | Congenital, familial and genetic disorders | 0 of 10 | 1 of 4 |
| Abdominal distension | Gastrointestinal disorders | 1 of 10 | 0 of 4 |
Serious events with the highest arm-level rate: diverticulitis (10.0%).
The registry record lists serious adverse events for 1 of 10 participants at risk in Group A and 0 of 4 participants at risk in Group B. It reports other adverse events for 10 of 10 participants at risk in Group A and 4 of 4 participants at risk in Group B. The death count is 0 in each group. These figures describe the recorded participants with events in each group; they do not show how many separate events occurred or establish that treatment caused an event.
Diverticulitis is listed as a top serious adverse event term at 10.0%. The registry information available for this analysis does not specify the term’s group attribution or provide its event-level context, so that percentage should not be used to infer a group-specific rate. Seriousness criteria, event timing, duration, outcomes, and exposure time are not reported in the registry record. Because allocation was nonrandomized and there was no control group, the group counts are not a controlled comparison of safety.
12. What the Result Does, and Does Not, Mean
The registry record supports a clear statement about the planned primary endpoint: the study did not collect the Week 48 change in blood functional AAT because study drug dosing was terminated before any participant reached that time point. That means the posted record cannot estimate the planned primary effect. It does not show that the effect was zero, beneficial, harmful, or statistically significant.
The listed adverse-event counts document events among participants at risk in the two VX-864 groups. These counts can describe what was recorded, but the study’s nonrandomized design, lack of a control group, and limited event context prevent a causal interpretation. The record does not establish that VX-864 produced or prevented any listed event. The counts also do not establish comparative safety between groups.
The study’s status as a Phase 2 trial and its intended 48-week treatment period describe its design, not its findings. The termination status is relevant because it explains why the planned primary endpoint is unavailable, but the reason for termination is not reported in the registry record. The registry also does not report the sample-size rationale, analysis population, multiplicity plan, or missing-data approach, so the intended inferential framework cannot be fully assessed.
Planning calculations are hypothetical illustrations that depend on assumptions and should not be confused with power observed in this study. They do not fill the gap left by the absent primary endpoint, and they do not turn descriptive event counts into treatment comparisons. The most defensible reading is that the posted record documents a nonrandomized, open-label study that ended before its primary assessment time and includes limited descriptive safety information. It does not provide a quantitative estimate of the planned primary treatment effect.
13. Why This Trial Matters Statistically
This trial is statistically informative in part because it illustrates the difference between a planned endpoint and an observed result. A primary outcome can be clearly specified yet remain unavailable when the study ends before the assessment time. In that situation, the appropriate interpretation is not a null finding or a negative result; it is that the planned question cannot be answered from the recorded outcome data.
The record also demonstrates why study design shapes interpretation. Nonrandomized allocation and the absence of a control group limit causal comparisons, even when treatment schedules are described for two parallel groups. Open-label conduct adds another consideration because masking was not used. Those design features matter independently of whether descriptive counts are available.
The safety listings are useful as a record of what was reported among participants at risk, but they cannot substitute for a controlled safety comparison. Understanding those counts requires attention to group denominators, event definitions, follow-up time, and attribution—details not fully reported in the registry record. Likewise, planning illustrations can help explain how assumptions influence a future sample-size calculation, but they are not evidence of the trial’s observed power or efficacy.
For researchers, the key statistical lesson is to separate three things: the design that was intended, the outcomes that were actually collected, and the inferences those data can support. Here, the planned primary Week 48 measurement was not collected, so the most prominent efficacy question remains unanswered in the posted record. Keeping that boundary explicit avoids treating absence of a result as a result in itself.
14. 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 primary limitation is that the planned endpoint, change in blood functional AAT from baseline at Week 48, was not collected. The registry record attributes this to study drug dosing being terminated before any participant reached Week 48. As a result, there is no primary effect estimate or associated measure of precision to interpret. The reason for termination is not reported in the registry record.
The nonrandomized design and absence of a like-for-like control group restrict comparisons between the two groups. Both groups received VX-864, and Group B had an additional biopsy schedule. Any group differences could reflect factors other than the intervention or biopsy schedule. The record does not provide details about baseline comparability or adjusted analyses.
The study was open-label, with no masking. The registry record does not describe whether outcome assessment was independently masked. It also does not report the sample-size justification, analysis populations, multiplicity approach, interim analyses, or method for handling missing outcomes. These omissions limit assessment of the planned inferential framework.
For safety, the record supplies participant counts with events, but the event definitions, timing, duration, exposure time, and group attribution for the listed serious term are not reported in the registry record. The data therefore support only a descriptive reading. The record lists multiple outcome measures but no outcome analyses, leaving the biochemical outcomes without quantitative results in the information available for this analysis.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Study to Evaluate Efficacy and Safety of VX-864 in Participants With the PiZZ Genotype — NCT05643495.
- Registry record last updated 2025-09-08; status last verified 2025-08.
- Results first posted 2025-09-08.
- 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.
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18. Record Summary
The registry record describes a Phase 2, open-label, nonrandomized, parallel study of VX-864 in participants with alpha-1 antitrypsin deficiency and the PiZZ genotype. Enrollment is listed as 14, and the study status is terminated. Participants were scheduled to receive VX-864 every 12 hours for 48 weeks or until dosing ended; Group B also had planned liver biopsies.
The primary endpoint was change in blood functional AAT from baseline at Week 48. The registry states that no data were collected because dosing ended before any participant reached Week 48. The safety listings report serious and other adverse-event counts, as well as 0 deaths in each group. The record lists no outcome analyses. Its posted information does not provide a quantitative primary efficacy result or a controlled treatment comparison.