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 Doxy-Post-exposure Prophylaxis (NCT05853120), a randomized phase 4 study. The primary outcome is Doxycycline Concentrations in Rectal Tissues.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05853120 |
| Phase | Phase 4 |
| Condition | Sexually Transmitted Diseases |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 45 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Emory University |
| Results posted | Yes |
2. Clinical Question
Population
Healthy people assigned male or female sex at birth who were not using gender-affirming hormone therapy and were willing to undergo study procedures. The record describes the target population; it does not report detailed eligibility criteria or the characteristics of the participants who contributed endpoint samples.
Intervention
Doxycycline 200 mg, administered according to the assigned study schedule. The record describes initial doses at the clinic on days 0 and 3, followed by doses at home on days 7 and 10.
Comparator
Doxycycline 100 mg, administered on the same schedule described in the record: initial doses at the clinic on days 0 and 3, followed by doses at home on days 7 and 10.
Primary question
What rectal-tissue doxycycline concentrations were measured on Day 2, 24 hours after the initial dose, in participants assigned to each dose? This is a pharmacokinetic question about tissue concentration. It is not a direct test of prevention of HIV or sexually transmitted infections.
The study’s stated purpose was to collect information about whether different oral doxycycline doses penetrate mucosal tissues in men and women. The broader research aim was to inform possible combinations of doxycycline with antiretrovirals for event-driven, multipurpose prevention strategies. Those aims provide context, but the posted primary endpoint is a measurement of drug concentration in rectal tissue. The registry record does not report a clinical prevention endpoint or an analysis of protection against infection.
The posted results give a median and full range for each dose group. They do not report a statistical test or confidence interval for the difference between groups. Accordingly, the clinical question addressed by these results is descriptive: what concentrations were observed among participants who completed the relevant visit and provided samples for processing?
3. Trial Design
The registry describes a Phase 4, randomized, parallel-group study with no masking. The listed intervention is doxycycline, and the two posted arms are labelled Doxycycline 100 mg and Doxycycline 200 mg. The record gives a total enrollment of 45. The number contributing samples to the primary endpoint differs from that total: the endpoint results list 16 participants for the 100 mg arm and 11 for the 200 mg arm. The record defines the endpoint population as participants who completed the corresponding study visit and provided samples for processing.
The arm descriptions state that participants received their first assigned dose at the clinic on days 0 and 3, and that the other three doses were taken at home on days 7 and 10. These descriptions are reproduced as recorded; further detail about adherence or the rationale for the schedule is not reported in the registry record. The study is unmasked, so the record does not describe masking of participants or study personnel.
The listed condition is sexually transmitted diseases. The study summary describes recruitment of healthy people assigned male or female sex at birth who were not using gender-affirming hormone therapy. It also describes in-person and online recruitment approaches, including community venues and online platforms. The record does not give a detailed account of participant characteristics in the endpoint groups.
The study is marked completed. The listed start date is 2023-05-31, and the primary completion date is 2024-09-25. These record details describe study administration, not the strength or certainty of the concentration findings. The registry record does not report the protocol’s sample-size justification, a planned interim analysis, or a statistical analysis plan. The posted primary results are descriptive summaries rather than a reported inferential comparison of the randomized groups.
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.
Overall Study
| Stage | Doxycycline 100 mg | Doxycycline 200 mg |
|---|---|---|
| STARTED | 26 | 19 |
| COMPLETED | 14 | 13 |
| NOT COMPLETED | 12 | 6 |
Reasons for not completing this period:
| Reason | Doxycycline 100 mg | Doxycycline 200 mg |
|---|---|---|
| Lost to Follow-up | 4 | 4 |
| Physician Decision | 3 | 0 |
| Withdrawal by Subject | 5 | 2 |
Analysis population for the primary outcome, as defined in the registry: Participants who completed the corresponding study visit and provided samples for processing.
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.
| Characteristic | Unit | Doxycycline 100 mg | Doxycycline 200 mg | Total |
|---|---|---|---|---|
| Participants analysed | 26 | 19 | 45 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 26 | 19 | 45 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Age, Continuous | years | 40.7 (SD 12.1) | 35.4 (SD 9.2) | 38.5 (SD 11.2) |
| Sex: Female, Male: Female | Participants | 7 | 10 | 17 |
| Sex: Female, Male: Male | Participants | 19 | 9 | 28 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 1 | 1 | 2 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 25 | 18 | 43 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 1 | 1 | 2 |
| Race (NIH/OMB): Asian | Participants | 1 | 2 | 3 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 13 | 9 | 22 |
| Race (NIH/OMB): White | Participants | 8 | 6 | 14 |
| Race (NIH/OMB): More than one race | Participants | 3 | 1 | 4 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | Participants | 26 | 19 | 45 |
6. Primary Endpoint
The registry lists the primary outcome as Doxycycline Concentrations in Rectal Tissues, measured over Day 2.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Full Range |
| Unit | µg/g |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is titled Doxycycline Concentrations in Rectal Tissues. It measures the concentration of doxycycline in rectal biopsy samples, in µg/g. The registry specifies a median as the summary measure and a full range as the accompanying description of spread. Samples were collected 24 hours after administration of the initial dose, at the Day 2 timeframe. The endpoint population comprises participants who completed the corresponding study visit and provided samples for processing.
A tissue concentration endpoint is used to describe drug penetration into a mucosal tissue. That fits the study’s stated aim of collecting information about doxycycline concentrations in mucosal tissues to inform research on possible prevention strategies. A measured tissue concentration is a pharmacokinetic observation: it describes drug measured in a sample at a specified time. It is not itself a measure of whether an infection was prevented, nor does it establish a concentration threshold associated with a clinical outcome. Such a threshold or relationship is not reported in the registry record.
The registry reports the 100 mg arm’s median as 0.863 µg/g, with a full range of 0.4 to 7.459, among 16 participants. For the 200 mg arm, it reports a median of 2.193 µg/g, with a full range of 1.283 to 3.766, among 11 participants. The range describes the observed spread of values in each group; it is not a confidence interval for the median. The registry record does not provide a confidence interval, a standard deviation, or a test of the difference between the dose groups.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary endpoint is a descriptive comparison of rectal-tissue concentrations on Day 2. The median reported for the 100 mg arm is 0.863 µg/g, and the median for the 200 mg arm is 2.193 µg/g. These are group summaries among participants with endpoint samples, not estimates adjusted for other variables. The results also give a full range of 0.4 to 7.459 for the 100 mg arm and 1.283 to 3.766 for the 200 mg arm. The displayed ranges show that observed values varied within both groups; they should not be read as measures of precision around the medians.
The endpoint results list 16 participants in the 100 mg arm and 11 in the 200 mg arm. These counts are smaller than the total enrollment of 45. The registry defines the endpoint population by visit completion and provision of samples, but does not explain why participants were not represented in these endpoint summaries. It does not report a missing-data analysis or say whether the endpoint values were available for all randomized participants.
No statistical analysis comparing the arm summaries is posted. In particular, the registry record does not report a test statistic, p-value, confidence interval for an arm contrast, or adjusted estimate. The tables and plots should therefore be read as ways to view the descriptive results, not as evidence that a formal between-group hypothesis test was conducted. The registry record also indicates that values were missing or not estimable for a two-arm comparison of the kind used for the related planning illustrations. No recalculated comparison is available to interpret.
The difference in the reported medians is a descriptive feature of these posted summaries; no new contrast is calculated. Without an inferential analysis and an uncertainty estimate for the contrast, the precision of any between-arm difference cannot be assessed from the posted results. Randomization describes how allocation was assigned, but does not by itself provide a statistical result or resolve missing endpoint information.
These data address drug concentration in rectal tissue at one specified post-dose time. They do not show whether either regimen prevents HIV or other sexually transmitted infections, and they do not establish how concentrations change at other times or in other tissues. The study summary describes broader research goals involving mucosal penetration and possible combinations with antiretrovirals, but those goals should not be confused with outcomes measured in the posted primary results. The registry record does not report a clinical outcome linking these concentrations to protection.
9. Statistical Methods Explained
The registry presents a randomized, parallel-group study without masking. In a randomized design, allocation is assigned by chance according to the study process. General statistical context: random assignment can support a fair comparison of groups, but it does not guarantee that every participant contributes data to every endpoint, and it does not substitute for reporting an analysis. The posted primary results summarize participants who completed the relevant visit and provided samples. No inferential comparison of the randomized groups is reported in the registry record.
What does the median summarize?
The primary endpoint is summarized by the median. General statistical explanation: the median is the middle value when observations are ordered. It describes a typical position in the observed sample and is less affected by an unusually high or low value than the arithmetic mean. Here, the registry reports a median of 0.863 µg/g for the 100 mg group and 2.193 µg/g for the 200 mg group. The record does not report the mean or a model-based estimate.
The reported full range gives the lowest and highest observed values in the endpoint group. General statistical explanation: a range is useful for showing the extent of observed values, but it can be strongly influenced by the most extreme observations and does not show how values are distributed between the endpoints. The registry reports 0.4 to 7.459 for the 100 mg group and 1.283 to 3.766 for the 200 mg group. These ranges are not confidence intervals and do not quantify uncertainty about a population median or a difference between groups.
How should sample counts be read?
The primary endpoint results list 16 participants for the 100 mg arm and 11 for the 200 mg arm. These are the group counts attached to the posted concentration summaries. The registry describes the relevant endpoint population as participants who completed the corresponding visit and provided samples for processing. General statistical explanation: a summary based on a subset of randomized participants describes the observed subset unless the analysis provides a method for handling missing outcomes. The registry record does not report such a method or explain the difference between the total enrollment and the endpoint counts.
The safety figures use different group counts from the primary endpoint summaries. Those figures list 26 participants at risk in the 100 mg group and 19 in the 200 mg group. Endpoint and safety denominators can differ because they refer to different reported data. The record does not provide enough detail to account for the difference, so the counts should remain tied to their respective results rather than treated as interchangeable.
What is not reported about the comparison?
The registry gives medians and ranges but does not report a statistical test, confidence interval, or adjusted analysis comparing the dose groups. General statistical explanation: an inferential comparison would typically describe both an estimated contrast and its uncertainty, so readers can assess how compatible the data are with a range of possible group differences. A p-value alone would not describe the size or precision of an effect, and a descriptive difference between medians is not a substitute for an uncertainty estimate. No such comparison is available in this record.
The record classifies the results as not reduced to one comparison and notes that values were missing or not estimable for a two-arm comparison. This is why a recalculated contrast or associated planning illustration should not be interpreted as an analysis of these data. The registry record does not report a model, distributional assumption, adjustment variables, or a method for calculating uncertainty for the primary endpoint.
What do planning illustrations mean?
General statistical explanation: a sample-size calculation is a planning exercise that asks how many participants might be needed under specified assumptions. It is not a measure of the power achieved by a completed study. The assumptions described for the planning illustrations include a two-sided significance level of 0.05, equal allocation, a normal approximation, and an effect defined as a stated fraction of an observed effect. The record does not provide a usable two-arm effect estimate for this endpoint, so planning values are not available to interpret. Any planning illustration elsewhere on the page is distinct from the trial’s actual design justification; the protocol’s own justification is not reported in the registry record.
General statistical explanation: over-dispersion means observed variability is greater than a chosen model expects. If a model ignores that extra variability, its uncertainty estimates may be too small. That concept is relevant when selecting and checking statistical models, but the registry record does not identify a model for these concentration data or report an over-dispersion assessment. It would not be appropriate to infer a method from the type of endpoint or from the arm summaries alone.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 10 outcome measures, while no secondary outcome results are posted. The primary endpoint is rectal-tissue doxycycline concentration at Day 2. The record does not provide results for the other listed measures in a way that supports their interpretation here, nor does it report a prespecified hierarchy among outcomes or an adjustment for multiple comparisons. Whether multiplicity was addressed in the protocol or in analyses is not reported in the registry record.
Multiplicity matters in general when researchers conduct several statistical tests: considering many results can increase the chance that at least one appears notable by chance. Possible approaches depend on the study objectives and analysis plan. Since no inferential results are reported for this primary endpoint, and no secondary results or multiplicity procedure are posted, there is no basis to assess how multiple testing may have been handled.
The endpoint population is described as participants who completed the corresponding visit and provided samples for processing. The registry reports 16 endpoint participants in the 100 mg group and 11 in the 200 mg group, compared with total enrollment of 45. It does not report why some enrolled participants are absent from the endpoint summaries, how many lacked samples, or whether any values were excluded or not estimable. It also does not report imputation, sensitivity analyses, or another missing-data strategy.
General statistical explanation: missing outcomes can affect interpretation if the people with observed measurements differ in relevant ways from those without measurements. The amount and pattern of missingness, along with the assumptions used to address it, help determine how confidently results can be generalized to the randomized groups. Those details are not reported in the registry record, so the posted summaries should be understood as describing the endpoint observations available for analysis, rather than as a documented estimate for every randomized participant.
The record does not report whether the endpoint analysis followed an intention-to-treat, per-protocol, or other analysis-population definition. Its stated endpoint population definition is the information available for interpreting the displayed summaries; a broader analysis-population rule is not reported in the registry record.
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 |
|---|---|---|---|
| Doxycycline 100 mg | 0 | 26 | 0.0% |
| Doxycycline 200 mg | 0 | 19 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Doxycycline 100 mg | 0 of 26 |
| Doxycycline 200 mg | 0 of 19 |
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 |
|---|---|
| Doxycycline 100 mg | 0 of 26 |
| Doxycycline 200 mg | 0 of 19 |
The posted safety figures list 26 participants at risk in the Doxycycline 100 mg group and 19 in the Doxycycline 200 mg group. In the registry’s serious adverse event fields, zero affected participants are reported in each group. The other adverse event fields also report zero affected participants in each group, and deaths are reported as zero in both groups. No top serious adverse event terms are listed.
These figures are counts in the safety record, not the denominators used for the primary concentration summaries. The safety counts at risk are 26 and 19, whereas the primary endpoint results list 16 and 11 participants. The registry record does not explain why the group counts differ. Keeping these denominators distinct is important when describing what each result represents.
General statistical explanation: observing zero reported events in a study does not establish that the underlying event risk is zero. A safety table describes events recorded in the population and period covered by that table; interpretation also depends on follow-up, event definitions, completeness of reporting, and the number of people observed. Further details about safety monitoring and the exact observation period are not reported in the registry record. These posted counts should therefore be read as the registry’s reported safety results, not as proof that no adverse events could occur.
The registry record does not report a comparative statistical analysis of safety between the groups. These counts alone do not establish that one dose has a different safety profile from the other.
12. What the Result Does, and Does Not, Mean
The posted results describe measured rectal-tissue doxycycline concentrations 24 hours after the initial dose. The 100 mg arm has a reported median of 0.863 µg/g, with a full range of 0.4 to 7.459, among 16 participants. The 200 mg arm has a reported median of 2.193 µg/g, with a full range of 1.283 to 3.766, among 11 participants. These are descriptive summaries of the endpoint observations included in the registry.
The medians are not accompanied by confidence intervals or a reported statistical test of the arm contrast. As a result, the registry does not quantify the precision of a difference between dose groups. The range in each arm describes observed values, not uncertainty around the median. The endpoint counts also do not match total enrollment, and the reasons for the difference are not reported. These limitations constrain what can be concluded from the descriptive summaries.
The endpoint is a measure of drug concentration in rectal tissue at a particular time. It is not a clinical outcome measuring infection, symptoms, or prevention. Although the study summary identifies broader interest in strategies to protect against HIV and sexually transmitted infections, this posted endpoint does not establish whether either dose prevents infection. The registry record does not report a link between the measured concentrations and a clinical protection threshold.
Nor do the results establish how concentration changes over time, what concentrations would be measured in other mucosal tissues, or how the drug would perform in a combination with antiretrovirals. Those are broader research questions described in the study summary; they are not answered by the posted primary results. The figures should be interpreted narrowly as concentration measurements at the specified endpoint time in the participants with samples.
In general, randomized allocation is a useful feature for comparing groups, but it does not turn descriptive summaries into a formal statistical test. Without a reported analysis and uncertainty estimate, readers should not infer a precise treatment effect from the observed medians. The registry record also does not report the protocol’s sample-size justification or statistical analysis plan, which limits assessment of how the posted analysis relates to the study’s original design.
13. Why This Trial Matters Statistically
This trial is statistically interesting because it links randomized dose assignment to a tissue concentration endpoint rather than a clinical infection outcome. That makes the interpretation depend on being clear about what is measured: the endpoint is doxycycline concentration in rectal biopsy samples at Day 2, 24 hours after the initial dose. It offers a descriptive view of tissue drug levels at that time, in the participants who completed the visit and provided samples.
The record also illustrates why endpoint denominators matter. Total enrollment is 45, while the concentration summaries list 16 participants in the 100 mg arm and 11 in the 200 mg arm. Safety tables list different at-risk counts. These are not interchangeable populations, and the reasons for the differences are not reported. Readers need to keep the population for each result in view when interpreting summaries.
Another statistical distinction is the difference between a descriptive contrast and an inferential comparison. The medians differ in the posted summaries, but the registry does not report a test or confidence interval for the arm comparison. The figures can show the observed data as summarized, but do not quantify uncertainty around a difference or establish how compatible it is with other possible effects.
The study’s broader motivation concerns mucosal penetration and possible future prevention strategies. Statistically, keeping that motivation separate from the endpoint is essential: a concentration measure is not evidence of clinical prevention unless the relationship to clinical outcomes is evaluated. The registry record does not report such an evaluation. The page therefore matters as an example of how pharmacokinetic results can inform research questions while leaving clinical efficacy and comparative precision unresolved.
Finally, the absence of a reported analysis plan, missing-data approach, and multiplicity procedure limits evaluation of the analysis beyond the posted summaries. These omissions do not invalidate the reported measurements; they define the boundaries of what the record allows readers to assess.
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 endpoint summaries are based on 16 participants in the 100 mg arm and 11 in the 200 mg arm, while total enrollment is 45. The registry states that the endpoint population consists of participants who completed the corresponding visit and provided samples for processing, but does not explain the difference between enrollment and endpoint counts. It does not describe whether missing samples, withdrawals, or other reasons account for participants absent from the summaries.
The results are medians with full ranges. No confidence intervals, standard deviations, or inferential comparison are reported for the primary endpoint. The posted summaries therefore do not quantify uncertainty around the group medians or an arm contrast. The broad ranges also show that observed concentrations varied, but the record does not provide individual-level data or a fuller distributional description.
The endpoint is limited to rectal tissue at Day 2, 24 hours after the initial dose. It does not report measurements at other time points or in other tissues. Although the study summary describes broader interest in mucosal penetration, the posted primary result cannot establish a time course or a relationship between tissue concentration and prevention of infection.
The study is randomized but unmasked. The registry record does not give further detail about blinding of sample processing or outcome assessment. It also does not report the protocol’s sample-size justification, statistical analysis plan, interim analyses, missing-data methods, or multiplicity approach. The registry lists 10 outcome measures but posts no secondary outcome results.
Finally, the safety figures use at-risk counts of 26 and 19, distinct from the primary endpoint counts, and the record does not explain the difference. Details about safety follow-up and event ascertainment are not reported in the registry record. These limitations apply to interpretation of the posted record and do not, on their own, establish how the full study was conducted beyond what is described there.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Doxy-Post-exposure Prophylaxis — NCT05853120.
- Registry record last updated 2025-09-11; status last verified 2025-09.
- Results first posted 2025-09-11.
- 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 describes a completed, randomized, unmasked, parallel-group Phase 4 study of doxycycline 100 mg and 200 mg. Total enrollment is 45. The study summary describes healthy people assigned male or female sex at birth who were not using gender-affirming hormone therapy and states that the research aim was to examine mucosal penetration in support of future prevention-strategy research.
The primary endpoint is median doxycycline concentration in rectal tissue, measured in µg/g on Day 2, 24 hours after the initial dose. The posted summaries are 0.863 µg/g, with a full range of 0.4 to 7.459, among 16 participants in the 100 mg arm, and 2.193 µg/g, with a full range of 1.283 to 3.766, among 11 participants in the 200 mg arm. No inferential comparison is reported.
Safety results report zero serious adverse events, zero other adverse events, and zero deaths in the listed groups, with 26 and 19 participants at risk. The registry record does not report a statistical analysis plan, a missing-data approach, or a sample-size justification. The posted primary results describe tissue concentrations; they do not report clinical prevention outcomes.