Phase 2a Study of CG400549 for the Treatment of cABSSSI Caused by Methicillin-resistant Staphylococcus Aureus: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Phase 2a Study of CG400549 for the Treatment of cABSSSI Caused by Methicillin-resistant Staphylococcus Aureus (NCT01593761), a na phase 2 study. The primary outcome is Status of Subject's Clinical Responses.

2. Clinical Question

The registry frames the primary objective as a preliminary assessment of efficacy. That objective does not make the study a controlled test of treatment effect: without a comparison group, the observed clinical course cannot be contrasted with an outcome under another treatment or under a control condition. The record does not report the primary endpoint count or proportion, so the clinical-response result itself cannot be described from the posted information. The trial also lists pharmacokinetics, bacterial susceptibility, microbial eradication, and adverse events among its secondary aims or outcomes. These provide context for the study’s scope, but they do not replace the missing primary response result.

3. Trial Design

This was a completed Phase 2a, repeated-dose, open-label, single-arm study of CG400549 for cABSSSI caused by MRSA. The registry lists CrystalGenomics, Inc. as the sponsor. The study start is recorded as 2012-06 and primary completion as 2012-09. Enrollment is listed as 20. The intervention is CG400549, and the arm description says all patients received it. The primary objective specifies a daily dose of 960 mg.

There was no masking and no randomized allocation. The trial therefore has no concurrent control arm with which to compare clinical response or adverse events. In a single-arm study, the observed outcomes describe the participants treated in the study; they do not isolate the effect of treatment from other influences on the clinical course. Open-label assessment also means the registry does not describe blinded assessment of the primary clinical response. Whether any assessment procedures were standardized beyond the stated investigator criteria is not reported in the registry record.

The primary endpoint was recorded among the mMITT population. The registry states that, among 20 participating subjects, 11 had confirmed MRSA and qualified for that population. The safety record separately gives adverse-event counts for subjects proven MRSA in mMITT and for subjects who received CG400549 in MITT. These are registry-defined populations, and the record does not give further population definitions or explain how participants with missing assessments were handled.

The stated sample-size illustration is not the study’s own design justification. Its assumptions describe an illustrative two-arm calculation with equal allocation and a normal approximation, based on a fraction of the observed effect. The study itself is listed as single-arm. A sample-size justification for the actual design, and whether any planning assumptions informed enrollment, are not reported in the registry record. No interim analysis or statistical analysis plan is described there.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Among 20 participated subjects, 11 subjects had confirmed MRSA and qualified for the mMITT population

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.

6. Primary Endpoint

The registry lists the primary outcome as Status of Subject's Clinical Responses, measured over Early Clinical Evaluation (ECE, 48 to 72 hours after enrollment).

The primary outcome is the status of participants’ clinical responses at Early Clinical Evaluation, defined as 48 to 72 hours after enrollment. The endpoint concerns whether the infection was judged stable or improving by the investigator. The registry’s definition includes cessation of spread of redness, edema, and/or induration, or a reduction in the size of these lesion features. It also requires absence of fever, defined in the record as < 37.7 °C.

This is a binary clinical-status outcome: a participant is assessed against the stated response criteria, and the registry identifies the outcome unit as participants. In general, a binary endpoint can summarize whether a specified clinical state was reached by a defined assessment time. Such an endpoint can be clinically interpretable when the criteria and assessment timing are clear. Here, the record gives both the timing window and the investigator-based criteria, although details on assessor training, adjudication, or handling of borderline assessments are not reported in the registry record.

The registry does not state the number of participants meeting the primary response definition, nor does it provide an estimate with a confidence interval or a statistical test. Therefore, the primary endpoint’s observed result and its precision are not reported in the registry record. The endpoint definition alone describes what was measured; it does not establish how many participants achieved the response.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Reading this study statistically begins with distinguishing the design from the endpoint. The design is open-label and single-arm, with no randomized allocation and no masking. The primary endpoint is a participant-level clinical status assessed in a defined early time window. The registry presents the endpoint unit as participants and gives its clinical criteria, but it does not report the endpoint result or a statistical comparison.

What does a single-arm result describe?

In general, a single-arm study describes outcomes among participants who received the study intervention. It can document what happened in that enrolled group and can inform later study planning. It does not, by itself, estimate a difference between treatment and control. A comparison requires an appropriate reference, and this trial has no concurrent comparator arm. Historical or external comparisons would need their own information and assumptions; none is reported in the registry record.

The open-label design is also relevant to a clinical endpoint assessed by an investigator. In general, when treatment assignment is known, expectations or knowledge of treatment can influence subjective assessments. The stated response criteria include observable lesion features and absence of fever, but the registry does not report blinded adjudication, independent confirmation, or procedures to limit assessment bias. This does not establish that assessment was biased; it means the record does not document protections that would allow a reader to evaluate that possibility.

How should a binary endpoint be read?

In general, a binary endpoint classifies each participant into an outcome category, such as meeting or not meeting a specified response definition. The event count and the number assessed are both needed to interpret the observed frequency. An estimate of uncertainty, such as a confidence interval, helps communicate how imprecisely a frequency has been estimated. The registry identifies the endpoint’s unit and definition but does not provide its response count, denominator for the primary analysis, confidence interval, or test result. Those quantities are therefore not reported in the registry record.

The endpoint timing matters as well. The primary assessment is specified at Early Clinical Evaluation, 48 to 72 hours after enrollment. This defines the intended point of assessment, but the registry does not describe how assessments outside that window were treated, whether there were repeat assessments, or how a participant with no assessment in the window was classified. Those details affect how a binary endpoint can be reproduced and interpreted.

What do the safety counts mean?

In general, an adverse-event count should be read alongside the population at risk, the event definition, and the period of observation. The registry lists serious events and other events separately for two populations. The serious-event counts are 0 among 11 subjects proven MRSA in mMITT and 0 among 20 subjects who received CG400549 in MITT. The other-event counts are 10 among 11 in the former population and 13 among 20 in the latter. The registry does not report the safety follow-up period or the event-level detail for the other-event counts. It also does not list serious adverse-event terms, and the death count is not reported in the registry record.

These population-specific counts should not be treated as a comparison of risk. The groups are not randomized treatment arms, and they represent different registry population labels. The record does not explain their overlap in detail. General statistical reasoning: comparing raw counts across different populations can be misleading when denominators, eligibility, or observation time differ. No comparative safety estimate is reported.

What can the planning illustration tell readers?

The record describes a sample-size illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It states that the effect to detect is a specified fraction of the observed effect. The illustration is explicitly separate from the study’s own design, which is single-arm. It is therefore a planning exercise under stated hypothetical assumptions, not a description of the trial’s enrollment process or an observed-power result.

In general, a planning calculation estimates the amount of information that might be needed for a future study under chosen assumptions. Its result depends on the assumed effect, variability or event frequency, analysis, and design. A calculation based on the observed effect can be optimistic because an observed estimate may be imprecise. The registry does not report numerical planning outputs in the registry record for this account, and its actual sample-size rationale is not reported in the registry record. No sample-size illustration can be used to infer the missing primary response result.

What analyses are documented?

The registry lists five outcome measures and zero analyses. The primary outcome is clinical response; secondary outcomes include clinical response status, microbial eradication response, adverse events, and the CG400549 plasma concentration-time profile. The record does not state a statistical analysis plan, the model used for any outcome, adjustment for baseline characteristics, handling of missing observations, or multiplicity procedures. It also does not report a primary endpoint estimate or inferential test. These omissions limit reproducibility and prevent assessment of whether the posted results follow a prespecified analysis approach.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures and zero analyses. The primary measure concerns clinical response, and the secondary outcomes include clinical response status, microbial eradication response, adverse events, and mean plasma concentration-time profile. The record does not report which outcomes were designated for formal hypothesis testing, whether any outcome was exploratory, or whether results were adjusted for multiple testing. A multiplicity procedure or hierarchy for interpreting outcomes is not reported in the registry record.

In general, evaluating multiple outcomes can increase the chance of finding an apparently notable result by chance if each is tested separately. A prespecified testing strategy can clarify which outcomes are confirmatory and how results should be interpreted. The absence of a reported strategy does not show that no strategy existed; it means the registry record does not document one. No collection of outcome labels should be treated as evidence that each outcome was tested or statistically significant.

Missing-data handling is also not reported in the registry record. The record identifies 20 participants and states that 11 with confirmed MRSA qualified for mMITT, but does not say how missing primary endpoint assessments were handled, whether any assessments were missing, or whether all eligible participants were included in the analysis. It does not report imputation, sensitivity analyses, or reasons for any unavailable measurements.

The population labels need to be kept distinct. The primary endpoint description refers to the mMITT population; safety counts are also listed for subjects received in MITT. Further definitions of those populations are not reported in the registry record. Without those details, the relation between the populations and the handling of participants who did not meet a population definition cannot be fully assessed.

11. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse-event counts for two populations: 0 among 11 subjects proven MRSA in mMITT, and 0 among 20 subjects who received CG400549 in MITT. It reports other adverse events for those populations as 10 among 11 and 13 among 20, respectively. These are counts within the listed populations, not a comparison between treatment arms. The study had no control arm, and the two population labels should not be interpreted as randomized groups.

No serious adverse-event terms are listed. The death count is not reported in the registry record; a missing death field should not be read as a reported zero. The safety observation period, event definitions beyond the category labels, and event attribution procedures are not reported in the registry record. Consequently, these counts do not establish how long participants were monitored or provide detailed descriptions of the events included in the other-event category.

In general, a zero count in a study population does not establish that an event is impossible or that risk is absent. Counts from a limited study population have uncertainty, and a safety interpretation also depends on follow-up and event ascertainment. The posted safety figures should be understood as descriptive registry counts for the stated populations, not as proof of comparative safety or a complete safety profile.

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

The registry record documents a Phase 2a investigation of CG400549 in participants with cABSSSI caused by MRSA, with early investigator-assessed clinical response as the primary endpoint. It gives the response criteria and assessment window, but does not report the primary endpoint result. Therefore, the posted information does not establish how many participants met the clinical response definition, nor how precisely that result was estimated.

The record also reports adverse-event counts in mMITT and MITT populations. Those counts describe events recorded for the stated groups. They are not a controlled comparison, and the study design does not permit a randomized estimate of the difference between treatment and an alternative. The counts also do not convey the complete event profile or duration of safety monitoring, details that are not reported in the registry record.

In general, a clinical study can contribute descriptive information even when it cannot establish a comparative treatment effect. Such information may help define endpoints, describe observed outcomes, or inform later research. Those broader roles should not be confused with evidence that the intervention caused a particular outcome. Here, the open-label single-arm design and missing primary result leave especially important limits on efficacy interpretation.

The record does not report a statistical analysis plan, a confidence interval for the primary endpoint, or an inferential result. It also does not report missing-data procedures, multiplicity handling, or the study’s own sample-size justification. These gaps do not show that the study failed to collect the relevant information; they mean the registry record does not permit those aspects to be evaluated. The sample-size illustration described in the record is planning-oriented and does not supply the absent clinical-response result or constitute observed power.

Accordingly, the appropriate reading is descriptive and cautious: the registry identifies the population, regimen, endpoint definition, and some safety counts, while leaving the primary efficacy outcome unreported. Neither a positive nor a negative conclusion about the primary clinical response can be supported from the posted results described in the record.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between a clearly specified endpoint and a reported endpoint result. The registry defines early clinical response using investigator-assessed lesion status and absence of fever, and sets an assessment window of 48 to 72 hours after enrollment. That information helps explain what the study intended to measure. However, the response count and its uncertainty are not reported, so the endpoint definition cannot answer the primary clinical question on its own.

The design also illustrates why single-arm results have a different interpretive role from randomized comparisons. Outcomes observed in participants receiving CG400549 can be described, but without a concurrent comparator the study cannot separate treatment-associated outcomes from other explanations. Open-label assessment is another consideration for an investigator-rated clinical endpoint. These are design features to account for when interpreting evidence; they are not proof that any particular result is biased.

Safety reporting offers a related lesson. Counts need to be interpreted with their population labels and follow-up context. The record gives serious and other adverse-event counts for mMITT and MITT populations, but does not report the observation period or detailed event terms for the other-event category. The distinction between a recorded count and a complete safety characterization is important.

Finally, the stated sample-size illustration should not be mistaken for the study’s design justification or for observed power. It uses assumptions for a two-arm planning calculation, whereas the trial is listed as single-arm. This mismatch makes the distinction between a statistical illustration and the design actually conducted particularly salient. The record’s missing analysis details also show why prespecification, outcome reporting, and transparent population definitions matter for reproducibility and interpretation.

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 for interpreting the main clinical question is that the registry does not report the primary response result. Although the endpoint, timing, and mMITT population are described, there is no response count, denominator for the primary analysis, or estimate of precision. The clinical outcome therefore cannot be reconstructed from the registry record.

The single-arm, open-label design limits causal and comparative interpretation. There is no control group, randomization, or masking. Because the endpoint is based on investigator assessment, the absence of reported blinded adjudication or other assessment safeguards leaves that aspect of outcome ascertainment unclear. The record does not state whether treatment duration, concomitant care, or other features of clinical management could be evaluated.

There is limited information about the enrolled population beyond the stated infection type, the total participation count, and the confirmed-MRSA mMITT count. Further eligibility criteria, baseline characteristics, participant flow, and reasons for any exclusions or discontinuations are not reported in the registry record. The record also does not explain the definitions of mMITT and MITT in detail or how their membership relates to one another.

For safety, the observation period and detailed definitions are not reported. Serious adverse-event terms are not listed, and deaths are not reported in the registry record. The other-event counts do not include event-level descriptions in the available record. These reporting gaps prevent a detailed assessment of event types, timing, or attribution.

Finally, no statistical analysis plan, missing-data procedure, multiplicity approach, primary endpoint test, confidence interval, or design-specific sample-size justification is reported in the registry record. The two-arm planning assumptions are not the same as the single-arm study design. These limitations concern what can be concluded from the registry record and do not establish what analyses or procedures may have been conducted outside it.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Phase 2a Study of CG400549 for the Treatment of cABSSSI Caused by Methicillin-resistant Staphylococcus Aureus — NCT01593761.
• Registry record last updated 2022-09-10; status last verified 2022-08.
• Results first posted 2022-07-06.
• 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.

18. Record Summary

NCT01593761 is a completed Phase 2a, repeated-dose, open-label, single-arm study of CG400549 for cABSSSI caused by MRSA. The sponsor is CrystalGenomics, Inc.; the recorded study start is 2012-06, and primary completion is 2012-09. Enrollment is listed as 20, and the primary objective specifies CG400549 at 960 mg daily.

The primary endpoint is investigator-assessed clinical response at Early Clinical Evaluation, 48 to 72 hours after enrollment. The record says 11 of the 20 participants had confirmed MRSA and qualified for mMITT. The primary response result is not reported in the registry record.

Safety counts list 0 serious adverse events among 11 in the proven-MRSA mMITT population and 0 among 20 in the MITT population; other adverse events are listed for 10 of 11 and 13 of 20, respectively. The study has no comparator arm, and the record does not report a statistical analysis plan, missing-data procedures, or multiplicity strategy.