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 Silmitasertib (CX-4945) in Patients With Severe Coronavirus Disease 2019 (COVID-19) (NCT04668209), a randomized phase 2 study. The primary outcome is Incidence of Treatment Emergent Adverse Events [Safety and Tolerability].
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04668209 |
| Phase | Phase 2 |
| Condition | Coronavirus |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 31 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Arizona |
| Results posted | Yes |
2. Clinical Question
Population
Patients with severe illness caused by SARS-CoV-2 were eligible for the study described in the registry record. The primary endpoint population is identified as the intent-to-treat population: participants assigned to silmitasertib in combination with standard care, or to standard care. The record does not provide further eligibility criteria or a detailed description of the population enrolled.
Intervention
The intervention was standard of care or supportive care combined with silmitasertib (CX-4945). The brief summary describes a 1000 mg BID dose. The endpoint description reports a median silmitasertib treatment duration of 14 days.
Comparator
The comparator was standard of care or supportive care without silmitasertib. The study was described as a randomized, two-arm, parallel-group trial with a planned allocation ratio of 1:1. It was open-label, so masking was not used.
Primary question
The primary question concerned the incidence of treatment-emergent adverse events through Day 60: how many participants experienced such events, and how were the events characterized by type, frequency, severity, timing, seriousness, and relationship to study therapy? The record also lists secondary questions about clinical recovery, clinical status, antiviral activity, and hospital duration. It does not report a primary comparative analysis or results for those secondary questions.
In statistical terms, the primary endpoint is a safety question framed around participants experiencing events, rather than a measure of clinical benefit. The trial also aimed to explore possible clinical benefits, but the registry record does not provide outcome estimates that would answer whether clinical recovery or other clinical outcomes differed between groups. The record lists enrollment of 31 and describes an exploratory study planned for 40 patients. Its status is terminated; a reason for termination is not reported in the registry record. These details set the scope for interpreting the posted information: the study design identifies the comparison, while the available registry results do not establish an estimated treatment contrast for the primary endpoint.
3. Trial Design
This was a Phase II, randomized, investigator-initiated, parallel-group trial. Its official title describes an evaluation of safety and exploration of clinical benefit of silmitasertib in patients with severe COVID-19. The brief summary characterizes it as a multi-center, open-label, prospective exploratory study. Participants were allocated to standard of care or supportive care alone, or to standard of care or supportive care with silmitasertib. The planned allocation ratio was 1:1.
The registry lists the intervention as silmitasertib (CX-4945), with the combination arm receiving it alongside standard care and the control arm receiving standard care. The brief summary specifies a dose of 1000 mg BID. The primary endpoint description reports a median treatment duration of 14 days. Masking was listed as none, so participants and trial personnel were not blinded according to the recorded design.
The record lists enrollment of 31, while the brief summary describes an exploratory study in 40 patients. Those entries describe the recorded enrollment and the planned study size, respectively; they should not be treated as interchangeable. The study began on 2021-01-21, had a primary completion date of 2022-06-30, and is listed as terminated. The reason for termination is not reported in the registry record.
Randomization is intended to support a fair comparison by assigning participants to groups using a chance-based process, reducing the risk that measured and unmeasured participant characteristics systematically determine treatment assignment. That is a general design principle, not evidence that all sources of bias were eliminated in this trial. Open-label assignment can affect care, reporting, and assessment, particularly for outcomes that involve clinical judgment. The registry record does not report details of sequence generation, allocation concealment, or safeguards for outcome assessment. It also does not report a statistical analysis plan, sample-size justification, or interim analyses. Therefore, the design description identifies the intended comparison but does not fill in these unreported methodological details.
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: Of the 31 enrolled participants, 29 met inclusion criteria and were randomized.
Overall Study
| Stage | Silmitasertib (CX-4945) in Combination With Standard of Care | Standard of Care |
|---|---|---|
| STARTED | 15 | 14 |
| COMPLETED | 8 | 6 |
| NOT COMPLETED | 7 | 8 |
Reasons for not completing this period:
| Reason | Silmitasertib (CX-4945) in Combination With Standard of Care | Standard of Care |
|---|---|---|
| Withdrawal by Subject | 2 | 2 |
| Lost to Follow-up | 3 | 4 |
| Subject Expired | 2 | 0 |
| Withdrawn from study | 0 | 1 |
| Adverse Event | 0 | 1 |
Analysis population for the primary outcome, as defined in the registry: Intent to treat population (all participants assigned to Silmitasertib/Combo, or Standard of Care). The median treatment duration of Silmitasertib was 14 days. The treatment Durations (days) = the last administration date - the first administration.
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 | Silmitasertib (CX-4945) in Combination With Standard of Care | Standard of Care | Total |
|---|---|---|---|---|
| Participants analysed | 15 | 14 | 29 | |
| Age, Continuous | years | 48.8 (SD 14.72) | 43.9 (SD 13.04) | 46.4 (SD 13.91) |
| Sex: Female, Male: Female | Participants | 5 | 7 | 12 |
| Sex: Female, Male: Male | Participants | 10 | 7 | 17 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 8 | 8 | 16 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 7 | 6 | 13 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 1 | 1 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 | 2 | 2 |
| Race (NIH/OMB): White | Participants | 15 | 11 | 26 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | participants | 15 | 14 | 29 |
6. Primary Endpoint
The registry lists the primary outcome as Incidence of Treatment Emergent Adverse Events [Safety and Tolerability], measured over Through Day 60.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the incidence of treatment-emergent adverse events through Day 60, expressed as a count of participants. The record describes adverse events occurring from randomization to Day 60 and says they were characterized by type, frequency, severity, timing, seriousness, and relationship to study therapy. Assessment included vital signs, physical findings, clinical laboratory results, and ECG results. Severity was to be graded using Common Terminology Criteria for Adverse Events (CTCAE version 5.0).
A participant-based safety endpoint is useful because it describes how many people experienced an adverse event, rather than only counting repeated events. It can provide a broad view of tolerability over the defined observation period. However, a single participant count does not convey the full clinical pattern: event type, severity, timing, seriousness, and treatment relationship can all matter. The endpoint description therefore names several dimensions of safety assessment, but the registry record does not provide a complete comparative analysis across those dimensions.
The listed primary parameter is a count of participants, and the stated population is intent to treat, including all participants assigned to either study group. The median silmitasertib treatment duration was 14 days, while safety follow-up for this endpoint extended through Day 60. The record does not report a single primary endpoint estimate, uncertainty interval, or formal comparison between groups. Consequently, the endpoint definition is available, but its comparative result is not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a randomized comparison of silmitasertib plus standard care against standard care alone, but it does not report an analysis of the primary endpoint. It lists zero analyses and gives no primary outcome estimate, confidence interval, or statistical test. Thus, the available record does not quantify a comparative effect on treatment-emergent adverse events through Day 60. It also does not provide a result for clinical recovery, clinical status, antiviral activity, or hospital duration.
Selected safety counts are reported. In the silmitasertib combination group, serious adverse events were reported for 3 of 15 participants at risk, other adverse events for 10 of 15, and deaths for 2. In the standard-care group, serious adverse events were reported for 2 of 14 participants at risk, other adverse events for 7 of 14, and deaths for 2. These figures are descriptive counts. They are not accompanied by a comparative estimate or uncertainty interval in the registry record. They should not be read as a complete statistical test of whether groups differ, nor as a complete account of all event characteristics specified in the primary endpoint.
The listed serious adverse-event terms include Tachypnea worsened, Acute hypoxemic respiratory failure, Thrombocytopenia, and Premature atrial contractions, each reported as 7.1%, and Respiratory failure, reported as 6.7%. These are registry-listed terms and percentages; the record does not provide enough accompanying analysis to establish how these terms relate to a treatment effect or to assess their comparative uncertainty.
The enrollment entry is 31, whereas the brief summary describes a planned study in 40 patients. The record does not explain the difference or report why the study was terminated. No conclusion about the reasons for termination follows from the status alone. Similarly, the presence of a randomized design does not supply missing outcome results: randomization describes how the comparison was intended to be made, not what the comparison found.
Confidence intervals, in general, describe the precision of an estimate under a statistical model. Without a posted endpoint estimate and interval, the precision of a treatment contrast cannot be evaluated from this record. The selected counts can be read as recorded safety information, but they do not establish either the direction or the magnitude of a comparative effect. The record therefore supports a description of the design and some safety counts, not a conclusion about clinical benefit or a definitive comparative safety finding.
9. Statistical Methods Explained
Randomization assigns participants to study groups by chance. In general, this approach aims to make groups comparable at the start of a trial, including with respect to characteristics that may not have been measured. It does not guarantee perfect balance in a particular study, and it does not prevent bias arising after assignment. The registry record identifies the trial as randomized but does not describe the sequence-generation method or allocation concealment. Those details are not reported in the registry record.
What does an open-label design mean?
Open-label means that treatment assignment is not masked from participants or relevant study personnel. In general, knowledge of assignment can influence behavior, co-interventions, reporting of symptoms, or clinical assessment. This is especially relevant when outcomes involve subjective judgments. The primary safety endpoint also includes laboratory results, vital signs, and ECG findings, which may be less dependent on subjective reports, but the record does not describe blinded outcome assessment. It would therefore be inappropriate to assume that masking was used for any assessment.
How should participant counts be understood?
The primary endpoint is described as a count of participants who experience treatment-emergent adverse events. A participant count is different from an event count: one person may experience multiple events, while a participant-based measure records whether that person experienced an event under the endpoint definition. The endpoint description also calls for characterization of event type, frequency, severity, timing, seriousness, and relationship to study therapy. Those dimensions cannot all be represented by a single count. The registry record supplies selected safety counts but no overall primary endpoint comparison.
What can a comparative estimate add?
In general, a comparative estimate expresses the difference or other contrast between study groups for an outcome. An uncertainty interval conveys how precisely that estimate is determined under the analysis assumptions. A statistical test can assess compatibility with a specified null hypothesis, but a test result alone does not describe the size or practical importance of an effect. For this trial, the registry record reports no primary comparative estimate, interval, or test. No such result can be inferred from the group counts alone without performing a separate calculation, and no recalculated comparison is reported in the registry record.
Why can event rates be harder to compare?
For a binary endpoint, each participant is classified according to whether an event occurred within the defined period. In general, the observed proportion depends on the event definition, follow-up completeness, and the population included in the analysis. If participants have different durations of observation, a simple proportion may not capture that difference. The record defines a follow-up period through Day 60 and identifies an intent-to-treat population, but it does not report information about missing outcome observations, censoring, or how incomplete follow-up was handled.
Over-dispersion is a general issue for count outcomes when the variation in counts is greater than assumed by a simple statistical model. It can lead to uncertainty estimates that are too narrow if the model does not allow enough variability. The primary endpoint is identified as a count of participants, rather than a rate of repeated events, and the registry record does not report a model or dispersion estimate. No particular over-dispersion adjustment can be attributed to the trial.
What do the planning illustrations represent?
In general, sample-size calculations are planning tools that estimate the number of participants or events needed under specified assumptions. They are not measures of the probability that a completed study detected an effect. The registry record describes planning illustrations based on the observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation; the target effect is framed as a stated fraction of the observed effect. The record does not report that these were the trial's original design calculations. Such illustrations should not be interpreted as observed power or as evidence that the trial was adequately powered for its primary endpoint.
The registry record does not report the trial's statistical analysis plan, a sample-size justification, handling of multiplicity, interim analyses, or a prespecified primary comparison method. These are important because analysis choices influence how results are estimated and interpreted. Without those details or posted analyses, the reader cannot assess whether the reported safety counts were analyzed according to a prespecified plan. The appropriate statistical reading is therefore limited to the recorded design, endpoint definition, and descriptive safety data, with unreported methods treated as unknown rather than inferred.
10. Multiplicity, Missing Data and Analysis Populations
The record lists 23 outcome measures and several secondary outcome descriptions, including clinical recovery, changes in clinical status, preliminary antiviral activity, and number of days hospitalized. It does not report analyses for these outcomes. Because multiple outcomes or repeated assessments can create multiple opportunities to observe an apparently notable result, statistical plans often specify how multiplicity will be addressed. Whether any adjustment, hierarchy, or other multiplicity strategy was planned is not reported in the registry record.
Missing-data handling is also not reported in the registry record. The primary endpoint description identifies an intent-to-treat population consisting of all participants assigned to either group, but that label alone does not explain how unavailable safety assessments or incomplete follow-up would be handled. The record does not describe imputation, exclusions, censoring, or sensitivity analyses. It is therefore not possible to assess the potential influence of missing observations on the primary endpoint.
The record gives no analysis population details beyond the primary endpoint's intent-to-treat description, and it lists zero analyses. It does not report whether the planned analysis used all randomized participants for each secondary outcome, or how participants with incomplete data were treated. These omissions limit evaluation of both the robustness and reproducibility of any comparative findings. No claim about the trial's multiplicity control, missing-data assumptions, or analytic population beyond the stated primary endpoint population is supported by 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 |
|---|---|---|---|
| Silmitasertib (CX-4945) in Combination With Standard of Care | 3 | 15 | 20.0% |
| Standard of Care | 2 | 14 | 14.3% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Silmitasertib (CX-4945) in Combination With Standard of Care | 2 of 15 |
| Standard of Care | 2 of 14 |
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 |
|---|---|
| Silmitasertib (CX-4945) in Combination With Standard of Care | 10 of 15 |
| Standard of Care | 7 of 14 |
Most frequent serious adverse event terms
| Event term | Organ system | Silmitasertib (CX-4945) in Combination With Standard of Care | Standard of Care |
|---|---|---|---|
| Acute hypoxemic respiratory failure | Respiratory, thoracic and mediastinal disorders | 1 of 15 | 1 of 14 |
| Premature atrial contractions | Cardiac disorders | 1 of 15 | 1 of 14 |
| Respiratory failure | Respiratory, thoracic and mediastinal disorders | 1 of 15 | 0 of 14 |
| Tachypnea worsened | Respiratory, thoracic and mediastinal disorders | 0 of 15 | 1 of 14 |
| Thrombocytopenia | Blood and lymphatic system disorders | 0 of 15 | 1 of 14 |
| Acute hypoxemic respiratory failure | Respiratory, thoracic and mediastinal disorders | 1 of 15 | 0 of 14 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Silmitasertib (CX-4945) in Combination With Standard of Care | Standard of Care |
|---|---|---|---|
| Diarrhea | Gastrointestinal disorders | 4 of 15 | 2 of 14 |
| Fatigue | General disorders | 1 of 15 | 2 of 14 |
| Acute hypoxemic respiratory failure | Respiratory, thoracic and mediastinal disorders | 2 of 15 | 1 of 14 |
| Weight loss | Investigations | 1 of 15 | 1 of 14 |
| Thrombocytopenia | Blood and lymphatic system disorders | 0 of 15 | 1 of 14 |
| Premature atrial contractions | Cardiac disorders | 0 of 15 | 1 of 14 |
| Bloody diarrhea | Gastrointestinal disorders | 1 of 15 | 0 of 14 |
| Constipation | Gastrointestinal disorders | 1 of 15 | 0 of 14 |
| Diarrhea worsened | Gastrointestinal disorders | 1 of 15 | 0 of 14 |
| Loose stools | Gastrointestinal disorders | 1 of 15 | 0 of 14 |
Serious events with the highest arm-level rate: tachypnea worsened (7.1%), acute hypoxemic respiratory failure (7.1%), thrombocytopenia (7.1%), premature atrial contractions (7.1%), respiratory failure (6.7%).
The registry reports serious adverse events for 3 of 15 participants at risk in the silmitasertib combination group and 2 of 14 in the standard-care group. Other adverse events are reported for 10 of 15 and 7 of 14, respectively. Deaths are reported as 2 in each group. These are counts as presented in the record, not an adjusted comparison. The record does not provide a statistical test or uncertainty interval for these figures.
The listed serious adverse-event terms and percentages are Tachypnea worsened (7.1%), Acute hypoxemic respiratory failure (7.1%), Thrombocytopenia (7.1%), Premature atrial contractions (7.1%), and Respiratory failure (6.7%). The registry record does not provide further comparative analysis for these terms. A term's listing does not, by itself, show whether an event was caused by study therapy or whether its frequency differed between groups.
The primary safety endpoint is broader than these selected figures: it covers treatment-emergent adverse events through Day 60 and calls for characterization by type, frequency, severity, timing, seriousness, and relationship to therapy. The posted counts therefore should be read as descriptive safety information, not as a complete analysis of every endpoint component.
12. What the Result Does, and Does Not, Mean
The registry record establishes that this was a randomized, open-label Phase II comparison of silmitasertib with standard care against standard care alone in patients described as having severe COVID-19. It defines a safety-focused primary endpoint through Day 60 and reports selected adverse-event and death counts. Those details are useful for understanding what the trial set out to examine and what safety information was recorded.
The record does not report a primary endpoint analysis, a treatment-effect estimate, a confidence interval, or a statistical test. It also does not report analyses for the listed secondary outcomes. Accordingly, the posted information cannot establish the size, direction, or precision of a comparative effect on safety, clinical recovery, clinical status, antiviral activity, or hospital duration. The descriptive counts should not be turned into a claim that one treatment caused more or fewer events.
A randomized design can support a valid group comparison when outcomes and analyses are available, but design alone is not a result. The open-label design may also matter for outcome assessment, and the record does not describe whether any assessments were blinded. The status of terminated and the enrollment of 31, alongside a brief-summary plan for 40 patients, are relevant context, but neither explains the missing analyses or the reason for termination. That reason is not reported in the registry record.
In general, statistical interpretation depends on both the observed estimate and its uncertainty, as well as the endpoint definition and analysis methods. Here, the registry record gives endpoint definitions and selected counts without the comparative analysis needed to evaluate precision. The appropriate conclusion is therefore limited: the record documents the trial design and selected safety observations, but it does not support a conclusion about clinical benefit or a definitive comparative safety effect.
13. Why This Trial Matters Statistically
This trial is statistically relevant because it pairs a randomized comparison with a safety-focused endpoint in a population described as having severe COVID-19. Randomization is a design feature intended to support fair comparisons, while the open-label structure raises questions about how outcomes were assessed and reported. The registry identifies the key design features, allowing readers to understand the intended comparison even though comparative results are not reported.
The record also illustrates why endpoint definitions and analysis results must be considered separately. It defines treatment-emergent adverse events through Day 60 and lists several dimensions for describing them, including severity and relationship to study therapy. Yet a clear definition does not substitute for a reported estimate and its uncertainty. The selected counts offer descriptive context, but cannot alone answer whether the groups differed or how precisely any difference was estimated.
Enrollment of 31 is recorded, while the brief summary describes a planned study in 40 patients. The trial is listed as terminated, and the record does not report why. These registry entries underscore the importance of distinguishing planned design information from the final enrollment entry and of avoiding assumptions about why a trial ended. They also make the absence of a posted outcome analysis important for interpretation.
For biostatistical reading, the key lesson is that a trial's design, endpoint, and results are separate parts of the evidence. The design describes the intended comparison; the endpoint specifies what was to be measured; an analysis would quantify the observed comparison and its precision. In this record, the first two are described, while the primary comparative analysis is not reported. That distinction prevents descriptive safety counts from being mistaken for a conclusive treatment effect.
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 registry record has important limitations for interpreting this trial. It lists zero analyses and does not provide a primary endpoint estimate, uncertainty interval, or formal comparison. Selected safety counts are available, but they do not cover all the characterization dimensions named in the endpoint definition or provide comparative uncertainty. The secondary outcomes are listed without reported analyses.
The trial is described as open-label, and the record does not report whether outcome assessment was blinded. Sequence generation and allocation concealment are also not described. The statistical analysis plan, original sample-size justification, interim analyses, multiplicity approach, and missing-data procedures are not reported in the registry record. The primary endpoint population is described as intent to treat, but that does not resolve how incomplete outcome data were handled.
The registry lists enrollment of 31, while the brief summary describes a planned study in 40 patients. The record does not explain that difference. It is listed as terminated, but the reason is not reported in the registry record. These details limit what can be inferred about completion and analysis, without establishing why enrollment differed from the plan or why the study ended.
Finally, the available information does not support conclusions about clinical benefit, the cause of adverse events, or a definitive comparative safety effect. Such conclusions would require outcome analyses and methodological details not reported in the registry record. The listed counts and event terms are best treated as descriptive information within those limits.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Silmitasertib (CX-4945) in Patients With Severe Coronavirus Disease 2019 (COVID-19) — NCT04668209.
- Registry record last updated 2023-11-07; status last verified 2022-11.
- Results first posted 2023-08-14.
- 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
NCT04668209 is a randomized, open-label Phase II, parallel-group trial sponsored by the University of Arizona. It compared silmitasertib (CX-4945) with standard care against standard care alone in patients described as having severe COVID-19. The brief summary specifies a 1000 mg BID dose and describes an exploratory study planned for 40 patients. The registry lists enrollment of 31, a start date of 2021-01-21, a primary completion date of 2022-06-30, and status as terminated.
The primary endpoint was the incidence of treatment-emergent adverse events through Day 60 in the intent-to-treat population. Selected safety counts and serious adverse-event terms are listed, but no primary or secondary outcome analyses are reported. The reason for termination, statistical analysis plan, missing-data methods, and primary comparative estimate are not reported in the registry record. The available information supports a description of the trial and its posted safety data, but not a conclusion about comparative clinical benefit or a definitive treatment effect.