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 EXPLORE: A Phase II Study to Evaluate the Safety and Efficacy of Two Doses of GT005 (NCT04437368), a randomized phase 2 study. The primary outcome is The Change From Baseline to Week 48 in Geographic Atrophy (GA) - Part 1.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04437368 |
| Phase | Phase 2 |
| Condition | Dry Age-related Macular Degeneration |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 98 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Gyroscope Therapeutics Limited |
| Results posted | Yes |
2. Clinical Question
Population
People with geographic atrophy secondary to age-related macular degeneration. The primary analysis population was described as randomized participants with a valid measurement and without a protocol deviation with impact.
Intervention
A single subretinal injection of GT005, evaluated at a low dose of 2E10 vg and a high dose of 2E11 vg. The high-dose arm was part of Part 1; the low-dose arm was included in Parts 1 and 2.
Comparator
Untreated control, included in Parts 1 and 2. The registry record does not report additional details about care or procedures in the control group.
Primary question
In Part 1, how did geographic atrophy area change from baseline to Week 48 among the randomized participants included in the stated analysis population? The endpoint was measured using fundus autofluorescence.
3. Trial Design
EXPLORE was a Phase II, randomized, parallel-group study of GT005 in people with geographic atrophy secondary to age-related macular degeneration. The registry record lists the study as multicentre and quadruple masked; its official title also describes outcome assessor masking. Enrollment was 98 participants. The record lists the study as terminated, with a start date of 2019-04-26 and a primary completion date of 2024-04-05.
The study compared a low dose of GT005, a high dose of GT005, and an untreated control. The low-dose arm was included in Parts 1 and 2, as was the untreated control. The high-dose arm was included in Part 1. The official title describes GT005 as administered through a single subretinal injection. The registry record does not report the allocation ratio or the number assigned to each arm as part of the trial-design description.
The primary outcome was change from baseline to Week 48 in geographic atrophy area for Part 1, measured by fundus autofluorescence. Other listed outcomes include geographic atrophy changes at later time points, adverse events, geographic atrophy morphology, visual acuity, and low-luminance letter counts. These outcomes span both parts of the study and different follow-up times. The registry record lists 16 outcome measures and 24 analyses.
The record does not report why the study was terminated, the planned recruitment target beyond the listed enrollment, or a detailed account of changes to the study after it began. It also does not report the allocation ratio, the procedures used to maintain masking, or the statistical plan in sufficient detail to determine how every analysis was conducted.
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: The parts were determined by genotype and not treatment. Because genotype may influence disease progression, these parts were considered in the analysis of the efficacy endpoints only, but not safety, and not demographics, as pre-specified in the SAP and protocol.
Overall Study
| Stage | GT005 Low Dose [2E10 vg] | GT005 High Dose [2E11 vg] | Untreated Control |
|---|---|---|---|
| STARTED | 52 | 9 | 37 |
| Randomized Part 1 | 10 | 9 | 14 |
| Randomized Part 2 | 42 | 0 | 23 |
| Randomized and Treated Part 1 | 9 | 9 | 0 |
| Randomized and Treated Part 2 | 18 | 0 | 0 |
| COMPLETED | 6 | 8 | 7 |
| NOT COMPLETED | 46 | 1 | 30 |
Reasons for not completing this period:
| Reason | GT005 Low Dose [2E10 vg] | GT005 High Dose [2E11 vg] | Untreated Control |
|---|---|---|---|
| Death | 3 | 0 | 2 |
| Study terminated by sponsor | 16 | 1 | 25 |
| Withdrawal by Subject | 4 | 0 | 3 |
| Sponsor instructions | 23 | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Full Analysis Set - for randomized participants with a valid measurement without a protocol deviation with impact.
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: Full Analysis Set (FAS) as described in the study protocol, which included all participants who were randomized to GT005 or untreated control. Because genotype may influence disease progression, these parts were considered in the analysis of the efficacy endpoints only, but not safety and not demographics, per the SAP and protocol.
| Characteristic | Unit | GT005 Low Dose [2E10 vg] | GT005 High Dose [2E11 vg] | Untreated Control | Total |
|---|---|---|---|---|---|
| Participants analysed | 52 | 9 | 37 | 98 | |
| Age, Continuous | years | 76.8 (SD 7.33) | 72.7 (SD 8.96) | 75.2 (SD 7.07) | 75.8 (SD 7.41) |
| Sex: Female, Male: Female | Participants | 34 | 5 | 18 | 57 |
| Sex: Female, Male: Male | Participants | 18 | 4 | 19 | 41 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 1 | 0 | 0 | 1 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): White | Participants | 51 | 7 | 35 | 93 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 2 | 2 | 4 |
6. Primary Endpoint
The registry lists the primary outcome as The Change From Baseline to Week 48 in Geographic Atrophy (GA) - Part 1, measured over Baseline, Weeks 12, 24, 36, and 48.
| Element | Registry entry |
|---|---|
| Result type | Least Squares Mean |
| Measure of spread | Standard Error |
| Unit | mm^2 |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the change from baseline to Week 48 in geographic atrophy area, measured in mm^2 using fundus autofluorescence. Geographic atrophy is the retinal condition under study, and area provides a continuous measurement of its extent. A change score describes how that measured area differs at follow-up from the participant’s baseline measurement.
As a general statistical matter, a continuous endpoint retains information about the magnitude of measurements rather than reducing participants to categories such as improved or not improved. Fundus autofluorescence is the measurement method specified for this outcome in the registry record. The endpoint is therefore a quantitative measure of retinal lesion area over the stated follow-up period, not a direct measure of visual function or quality of life.
The registry record describes the primary outcome parameter as a least-squares mean and identifies the dispersion measure as the standard error. A least-squares mean is a model-based estimate of a group mean; the specific model and its covariates are not reported in the registry record. The endpoint description identifies the baseline, Weeks 12, 24, and 48 as measurement time points, while the primary outcome is the change to Week 48. Numerical estimates for the primary comparison are not reported in the registry record, so the size and precision of any between-group difference cannot be described from that record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary endpoint is clearly identified, but the registry record does not report numerical results for the change in geographic atrophy area at Week 48. It therefore does not establish from the posted primary outcome data how the groups compared, the size of any estimated difference, or the precision of an estimate. A treatment-effect estimate, confidence interval, and test result for the primary comparison are not reported in the registry record.
This distinction matters: a trial’s design and endpoint tell readers what was intended to be evaluated, but they do not reveal the observed primary effect. Without the numerical result, readers cannot assess whether the data are compatible with a range of effects, whether the estimate is precise, or whether it is consistent with a negligible difference. The record’s status as terminated does not by itself explain the reason for termination or determine how to interpret an unreported endpoint.
The registry does include adverse-event counts by group. These counts describe reported safety events in the listed groups, but they do not replace the primary efficacy result. Nor do counts alone establish whether an event was caused by study treatment. The registry lists 5 deaths overall; the record does not provide a causal assessment in the registry record for this description. Serious-event and other-event counts should be read as descriptive observations, particularly when group sizes differ and the record does not include a complete account of event timing, exposure, or attribution.
The trial enrolled 98 participants across its listed groups, including a high-dose group with 9 participants at risk for serious and other adverse events. General statistical reasoning cautions that estimates from small groups can be imprecise, and sparse events can make comparisons unstable. The registry record does not report inferential comparisons for the adverse-event counts, so the counts should not be treated as evidence of a statistically established difference between groups.
In short, the registry record describes the study question, design, outcome definitions, and some safety counts. It does not report the numerical primary endpoint results needed to characterize the primary treatment contrast. Conclusions about the magnitude, direction, or precision of that contrast are therefore not supported by the record as described.
9. Statistical Methods Explained
The primary outcome is continuous: it measures geographic atrophy area and its change over time. The registry record identifies the primary parameter as a least-squares mean and the dispersion as a standard error. It does not report the full statistical model, the estimated group means, a treatment contrast, or a confidence interval for the primary outcome. Consequently, the statistical concepts below explain how such quantities are generally interpreted, rather than describing an unreported analysis in this trial.
What does a least-squares mean represent?
In general, a least-squares mean is an estimated group mean from a statistical model. Unlike a simple arithmetic average, it may account for features included in that model, such as baseline values or other covariates. The registry record does not report which covariates, if any, were included, or the model structure used for this outcome. Readers therefore cannot determine from the registry record precisely how the stated least-squares means were adjusted.
For a randomized comparison, an estimate of the difference between groups is usually more informative about the treatment contrast than separate group estimates considered alone. A confidence interval around that contrast communicates the range of values reasonably compatible with the data under the model and assumptions. Its width reflects precision: a wider interval indicates less precision. These are general interpretations; the registry record does not report the primary contrast or its confidence interval.
How is a standard error different from variability?
Generally, a standard error describes uncertainty in an estimated quantity, such as a mean. It is not the same as the spread of individual participants’ measurements. Standard errors are used to assess how precisely a sample estimates a population quantity, while measures such as a standard deviation describe participant-level dispersion. The registry record specifies standard error as the dispersion measure for the primary outcome, but does not provide a numerical value for it in the registry record.
Repeated measurement of geographic atrophy at baseline and later visits can provide information about change over time. The record lists baseline and Weeks 12, 24, and 48 for the primary outcome timeframe. General longitudinal methods can account for correlations among repeated observations from the same participant, but the statistical approach used for these measurements is not reported in the registry record. It would therefore be inappropriate to attribute a particular repeated-measures model or handling of within-participant correlation to this study.
What does the stated analysis population mean?
The primary population is described as the Full Analysis Set for randomized participants with a valid measurement and without a protocol deviation with impact. This description indicates that randomization alone did not define inclusion in the primary analysis: validity of measurement and the specified protocol-deviation condition also mattered. The criteria used to decide that a deviation had impact, the number excluded, and the timing of those decisions are not reported in the registry record.
In general, analysis populations can affect interpretation because excluding participants after randomization may change the balance created by random assignment. A full account of exclusions and reasons is important for judging whether the analyzed groups remain comparable. The registry description gives the stated criteria but does not report participant flow or enough detail to assess the consequences of applying them.
How should planning calculations be read?
General sample-size illustrations estimate how many participants per arm might be needed under specified assumptions to detect a chosen effect with a chosen power. They are planning exercises, not observed power and not evidence that the trial achieved a particular probability of detecting an effect. The planning assumptions described for this study use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; they set the target effect as a fraction of the observed effect. Such illustrations are not the trial’s own design justification. The registry record does not report the trial’s sample-size justification.
For a continuous outcome, the result of a planning calculation depends on the effect size and the variability assumed, among other choices. If the underlying observed effect is uncertain, planning based on it is uncertain too. No sample-size illustration should be interpreted as a guarantee of adequate precision or as a substitute for the primary estimate and its confidence interval. The registry record does not report the trial’s interim-analysis plan, if any, or sufficient statistical-plan detail to determine how the listed analyses were adjusted or selected.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists 16 outcome measures and 24 analyses, covering multiple endpoints, follow-up times, and study parts. Considering many outcomes or time points can raise a multiplicity issue: when many statistical tests are performed, the chance of at least one apparently notable result can increase. General methods for addressing multiplicity include adjusting significance thresholds or distinguishing a prespecified primary analysis from exploratory analyses. The registry record does not report whether or how multiplicity was addressed.
The primary outcome is identified as change in geographic atrophy area to Week 48 in Part 1. Several additional outcomes concern later measurements, morphology, visual acuity, low-luminance letter counts, and adverse events. The presence of multiple outcomes does not itself establish that every outcome was tested, nor does it reveal which analyses were confirmatory. The statistical analysis plan and any hierarchy among secondary outcomes are not reported in the registry record.
The record describes the primary analysis population as randomized participants with a valid measurement and without a protocol deviation with impact. It does not report the number of participants with missing measurements, the reasons for missingness, or the method used to handle missing data. In general, missing-data methods rely on assumptions about why measurements are unavailable; different assumptions can lead to different estimates. No particular missing-data approach can be inferred.
The registry record also does not report the trial’s sample-size justification, any interim analyses, or a detailed account of protocol deviations and exclusions. These omissions limit assessment of how prespecified the analyses were and how robust the results might be to analytic choices. They do not, on their own, demonstrate that the study’s analyses were inappropriate.
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 |
|---|---|---|---|
| GT005 Low Dose [2E10 vg] | 5 | 52 | 9.6% |
| GT005 High Dose [2E11 vg] | 2 | 9 | 22.2% |
| Untreated Control | 4 | 37 | 10.8% |
| Overall | 11 | 98 | 11.2% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| GT005 Low Dose [2E10 vg] | 3 of 52 |
| GT005 High Dose [2E11 vg] | 0 of 9 |
| Untreated Control | 2 of 37 |
| Overall | 5 of 98 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| GT005 Low Dose [2E10 vg] | 19 of 52 |
| GT005 High Dose [2E11 vg] | 9 of 9 |
| Untreated Control | 16 of 37 |
| Overall | 44 of 98 |
Most frequent serious adverse event terms
| Event term | Organ system | GT005 Low Dose [2E10 vg] | GT005 High Dose [2E11 vg] | Untreated Control | Overall |
|---|---|---|---|---|---|
| Visual acuity reduced - Study eye | Eye disorders | 1 of 52 | 0 of 9 | 0 of 37 | 1 of 98 |
| Cellulitis | Infections and infestations | 1 of 52 | 0 of 9 | 0 of 37 | 1 of 98 |
| Gastroenteritis | Infections and infestations | 0 of 52 | 1 of 9 | 0 of 37 | 1 of 98 |
| Pneumonia | Infections and infestations | 1 of 52 | 0 of 9 | 0 of 37 | 1 of 98 |
| Staphylococcal infection | Infections and infestations | 0 of 52 | 0 of 9 | 1 of 37 | 1 of 98 |
| Urinary tract infection | Infections and infestations | 0 of 52 | 0 of 9 | 1 of 37 | 1 of 98 |
| Fall | Injury, poisoning and procedural complications | 1 of 52 | 0 of 9 | 0 of 37 | 1 of 98 |
| Hip fracture | Injury, poisoning and procedural complications | 1 of 52 | 0 of 9 | 0 of 37 | 1 of 98 |
| Rib fracture | Injury, poisoning and procedural complications | 1 of 52 | 0 of 9 | 0 of 37 | 1 of 98 |
| Breast cancer metastatic | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 1 of 52 | 0 of 9 | 0 of 37 | 1 of 98 |
Most frequent non-serious adverse event terms
| Event term | Organ system | GT005 Low Dose [2E10 vg] | GT005 High Dose [2E11 vg] | Untreated Control | Overall |
|---|---|---|---|---|---|
| Retinal pigmentation - Study eye | Eye disorders | 3 of 52 | 6 of 9 | 0 of 37 | 9 of 98 |
| Conjunctival haemorrhage - Study eye | Eye disorders | 6 of 52 | 1 of 9 | 0 of 37 | 7 of 98 |
| Intraocular pressure increased - Study eye | Investigations | 4 of 52 | 3 of 9 | 0 of 37 | 7 of 98 |
| Cataract - Study eye | Eye disorders | 3 of 52 | 2 of 9 | 1 of 37 | 6 of 98 |
| COVID-19 | Infections and infestations | 3 of 52 | 2 of 9 | 1 of 37 | 6 of 98 |
| Cataract - Fellow eye | Eye disorders | 0 of 52 | 1 of 9 | 2 of 37 | 3 of 98 |
| Cataract nuclear - Study eye | Eye disorders | 2 of 52 | 1 of 9 | 0 of 37 | 3 of 98 |
| Eye pain - Study eye | Eye disorders | 1 of 52 | 2 of 9 | 0 of 37 | 3 of 98 |
| Retinal haemorrhage - Study eye | Eye disorders | 2 of 52 | 1 of 9 | 0 of 37 | 3 of 98 |
| Fall | Injury, poisoning and procedural complications | 1 of 52 | 1 of 9 | 1 of 37 | 3 of 98 |
Serious events with the highest arm-level rate: gastroenteritis (11.1%), amyotrophic lateral sclerosis (11.1%), staphylococcal infection (2.7%), urinary tract infection (2.7%), lung neoplasm malignant (2.7%).
The registry record reports serious adverse events and other adverse events by group. For serious adverse events, the listed counts are 5 of 52 in the low-dose group, 2 of 9 in the high-dose group, and 4 of 37 in untreated control; the overall count is 11 of 98. For other adverse events, the listed counts are 19 of 52, 9 of 9, and 16 of 37 in those groups, respectively; the overall count is 44 of 98. The record also lists 3 deaths in the low-dose group, 0 in the high-dose group, 2 in untreated control, and 5 overall.
These are descriptive counts of participants affected, not estimates of comparative risk or evidence that an event was caused by GT005. The record does not report inferential comparisons for these figures. General interpretation should account for the different numbers at risk in the groups and for the fact that event counts alone do not describe timing, duration, or exposure. The listed serious-event terms include gastroenteritis and amyotrophic lateral sclerosis at 11.1% each, and staphylococcal infection, urinary tract infection, lung neoplasm malignant, and cerebrovascular accident at 2.7% each. The registry record does not provide enough information in the registry record to assess attribution or compare the frequency of individual terms across groups.
12. What the Result Does, and Does Not, Mean
The registry record establishes that EXPLORE was a randomized Phase II study evaluating two GT005 doses against untreated control in geographic atrophy secondary to age-related macular degeneration. It also identifies a primary endpoint: change in geographic atrophy area from baseline to Week 48 in Part 1, measured using fundus autofluorescence. That information makes the study question and the intended measurement clear.
However, the numerical primary outcome results are not reported in the registry record. There is no reported estimate of the primary treatment contrast, no confidence interval describing its precision, and no reported test result for that comparison. The registry record therefore does not permit a conclusion about the direction or size of the primary effect, or about how compatible the data are with different possible effects.
The safety counts offer a separate descriptive account of adverse events and deaths in the listed groups. They do not establish that treatment caused an event, and the registry entries do not provide a comparative statistical analysis of those counts. General statistical interpretation distinguishes observed event counts from causal conclusions, which require appropriate study information and analysis.
The listed enrollment is 98, and the groups were not the same size in the reported adverse-event figures. In general, differences in group size affect how directly counts can be compared; even proportions can be imprecise when based on small groups or few events. The high-dose group had 9 participants at risk in the listed safety data, so its counts should be interpreted with particular attention to the limited group size. This does not establish a direction of effect or a treatment-related safety difference.
The registry record also does not explain why the trial was terminated. Termination status alone does not identify the reason, nor does it determine what the primary outcome would have shown. The supported interpretation is therefore limited: the record describes a randomized study and its planned primary measure, but lacks the primary numerical results needed to characterize the efficacy comparison.
13. Why This Trial Matters Statistically
EXPLORE illustrates why reading a trial record requires distinguishing the study question from the results available to answer it. The registry record identifies a randomized, parallel-group Phase II study, its treatment arms, and a continuous primary endpoint. These details allow readers to understand what comparison was intended: change in geographic atrophy area to Week 48 in Part 1.
At the same time, the numerical primary outcome results are not reported in the registry record. A clearly specified endpoint is not a substitute for an estimated effect and its uncertainty. Statistical interpretation depends on both: the endpoint defines what is measured, while the estimate and interval describe what the observed data indicate and how precisely they indicate it. Without those numerical results, the primary comparison cannot be characterized.
The study also highlights the importance of separating efficacy outcomes from safety summaries. Serious adverse events, other adverse events, and deaths are reported as counts by group. Such counts can describe what was observed, but they do not establish treatment causality or statistical differences. Group sizes and the number of events matter when judging how stable a comparison may be.
Finally, the registry record lists multiple outcomes and analyses, while leaving key details about multiplicity, missing data, and the statistical plan unreported. These gaps limit the assessment of analytic choices and the strength of conclusions that might be drawn from the record. The case is a reminder that transparent reporting of estimates, precision, analysis populations, and methods is essential for readers to evaluate clinical trial evidence.
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 main limitation for statistical interpretation is that numerical results for the primary endpoint are not reported in the registry record. Without the group estimates, a between-group contrast, and a measure of uncertainty, the primary efficacy comparison cannot be assessed. The record also does not report a primary-outcome test result.
The stated analysis population includes randomized participants with a valid measurement and without a protocol deviation with impact. The number of participants excluded under these criteria, the reasons for invalid measurements, and how deviations were judged are not reported in the registry record. Participant flow and the handling of missing outcome measurements are also not reported, limiting evaluation of whether the analyzed population remained comparable across randomized groups.
The record lists multiple outcomes and analyses, but does not report a multiplicity strategy or a detailed statistical analysis plan. It does not report the model used to estimate the least-squares mean, any covariate adjustment, or the assumptions applied to repeated measurements. The trial’s sample-size justification and any interim analyses are not reported in the registry record.
For safety, the registry entries include group counts and selected serious-event terms, but not a comparative inferential analysis, event timing, or causal attribution. The high-dose group included 9 participants at risk in the listed safety data, so its descriptive counts are based on a small group. The registry record lists the study as terminated but does not report the reason for termination. These limitations restrict interpretation; they do not establish that any particular result or analysis is biased.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: EXPLORE: A Phase II Study to Evaluate the Safety and Efficacy of Two Doses of GT005 — NCT04437368.
- Registry record last updated 2026-01-27; status last verified 2026-01.
- Results first posted 2025-08-12.
- 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
EXPLORE, registered as NCT04437368, was a Phase II randomized, parallel-group, quadruple-masked study of GT005 in geographic atrophy secondary to age-related macular degeneration. Enrollment was 98, and the registry lists the study as terminated.
The study compared low-dose GT005, high-dose GT005, and untreated control. The primary outcome was change from baseline to Week 48 in geographic atrophy area, measured using fundus autofluorescence in Part 1. The primary analysis population was described as randomized participants with a valid measurement and without a protocol deviation with impact.
The registry record lists safety counts and multiple secondary outcomes, but numerical results for the primary endpoint are not reported in the registry record. The reason for termination, the trial’s sample-size justification, and detailed methods for multiplicity and missing data are also not reported in the registry record.