Trial Design and Oversight
CARDEA was a phase 2, randomized, double blind, placebo-controlled trial that tested the addition of Auxora to corticosteroids and standard of care in patients with severe COVID-19 pneumonia (ClinicalTrials.gov identifier, NCT04345614). Patients were randomized 1:1 to Auxora plus standard of care or placebo plus standard of care. Randomization was stratified by baseline imputed PaO2/FiO2 ratio of >200 vs ≤200 through a central, concealed, web-based, automated system. An independent statistician created the randomization schedule with stratified block randomization method using SAS proc plan procedure. Within each stratum, the treatment codes were assigned at a 1:1 ratio of Auxora and placebo with the block size of 4. The PaO2/FiO2 was imputed using a non-linear equation from a SpO2/FiO2 ratio obtained using pulse oximetry. The baseline PaO2/FiO2 was the worst value in the 24 hours prior to screening.
Auxora was administered by a 4-hour IV infusion at 2.0 mg/kg (1.25 mL/kg) at 0-hour and 1.6 mg/kg (1 mL/kg) at 24 and 48 hours. Placebo was dosed at 1.25 mL/kg at 0-hour and 1 mL/kg at 24 and 48 hours. Patients were assessed immediately before each infusion. Seventy-two hours after the start of the first infusion, patient assessment occurred every 24 hours (±4 hours) until 240 hours and then continued every 48 hours until Day 30 or discharge. The ordinal scale was assessed daily for patients in a standardized manner as described in the electronic case report form. Patients discharged before Day 25 were contacted at Day 30 (±5 days). All patients were contacted for a follow-up safety and mortality assessment at Day 60 (±5 days). Public information (e.g., death reports, governmental information) was used by sites to ascertain Day 60 mortality status in patients who refused direct contact or had withdrawn from the trial. All patients were required to receive dexamethasone or equivalent dose of another corticosteroid as well as pharmacological prophylaxis against development of venous thromboembolic disease. Remdesivir use was recommended for all patients, and convalescent plasma administration was allowed according to local standard of care. Other immunomodulators for the treatment of COVID-19 pneumonia, including tocilizumab and JAK inhibitors, were prohibited due to regulatory guidance.
An institutional review board at each site approved the trial protocol. Informed consent was obtained from the patient or the patient’s legally authorized representative if the patient was unable to provide consent. The trial was conducted in accordance with Good Clinical Practice guidelines and the principles of the Declaration of Helsinki, and was sponsored by CalciMedica, Inc (La Jolla, CA). An independent data monitoring committee (IDMC) provided trial oversight. Operational support was provided by Bionical-Emas (Paulsboro, NJ) and Princeton Pharmatech (San Francisco, CA) performed the statistical analyses. All authors vouch for the accuracy and completeness of the data and for the fidelity of the trial adherence to the protocol.
The IDMC first reviewed unblinded safety data once 57 patients were randomized, then again after 70 patients with a baseline imputed PaO2/FiO2 ≤200 completed 60 days of the trial, and finally after randomization of 209 patients with a baseline imputed PaO2/FiO2 ≤200. The IDMC also performed an interim sample size re-estimation based on the recovery rate ratio after 70 patients with a baseline imputed PaO2/FiO2 ≤200 reached Day 60.
The trial was initially designed to enroll up to 400 patients, with a maximum of 80 patients having a baseline imputed PaO2/FiO2 >200. The Sponsor capped the number of patients with a baseline imputed PaO2/FiO2 >200 at the time of the first IDMC review because a blinded analysis showed that no patients in this subgroup required mechanical ventilation or died during hospitalization. Due to declining rates of US COVID-19 hospitalizations in the spring of 2021, and the more frequent use of tocilizumab in CARDEA candidate patients at many trial sites following recommendations by the National Institutes of Health’s COVID-19 Treatment Guidelines Panel,30 the Sponsor elected to stop the trial early following discussions at the third IDMC review.
Eligible patients were adults with a laboratory-confirmed diagnosis of COVID-19 determined by polymerase chain reaction or other assay and pneumonia as documented by chest imaging. Patients were required to have ≥1 symptom consistent with COVID-19 and respiratory failure, defined as baseline imputed PaO2/FiO2 ≤300, requiring oxygen therapy using either a high flow (HFNC) or low flow nasal cannula. Patients with a baseline imputed PaO2/FiO2 ≤75 and those receiving either non-invasive mechanical ventilation or invasive mechanical ventilation and current treatment with immunosuppressive medications or immunotherapy were excluded from the trial. Full entry criteria are available in the Supplementary Appendix.
The primary endpoint was time to recovery through Day 60, defined as meeting the criteria for category 6 (Hospitalized, not requiring supplemental oxygen or ongoing medical care), category 7 (Discharged, requiring supplemental oxygen), or category 8 (Discharged, not requiring supplemental oxygen) using an 8-point ordinal scale. The key secondary endpoint of all-cause mortality at Day 60 was requested by regulatory guidance. Additional secondary endpoints evaluated in the efficacy set included all-cause mortality at Day 30, the proportion of patients requiring invasive mechanical ventilation or death through Day 60, the proportion of patients requiring invasive mechanical ventilation through Day 60, and differences in outcomes measured by the 8-point ordinal scale through Day 60. Safety endpoints included the occurrence and severity of treatment-emergent adverse events (TEAEs) and serious AEs (SAEs).
The primary and key secondary endpoints were also evaluated in pre-specified subgroups of patients who required oxygen therapy via either HFNC or low flow nasal cannula at baseline or patients having an imputed PaO2/FiO2 ≤100 or 101-200 at baseline, and in all randomized patients. The safety endpoints were evaluated in all patients who received study drug, including those with an imputed PaO2/FiO2 >200.
The efficacy set was pre-specified, consisting of those patients with a baseline imputed PaO2/FiO2 ≤200. A two-group log-rank test with a 0.05 two-sided significance level would have 90% power to detect a difference in the recovery rate ratio of approximately 1.49 in the 320 patients with a baseline imputed PaO2/FiO2 ≤200 who were randomized 1:1 to Auxora or placebo. The Sponsor elected to not change the sample size after the IDMC performed the sample size re-estimation.
Time to recovery through Day 60 was compared between the Auxora and placebo groups using log-rank test stratified by baseline imputed PaO2/FiO2 ≤100 vs. 101-200 and displayed using a Kaplan-Meier estimate. Patients were censored at the last ordinal scale assessment if no recovery event was observed during the study.
All-cause mortality at Day 60 was compared between the Auxora and placebo groups using a Cochran-Mantel- Haenszel test stratified by the baseline imputed PaO2/FiO2 ≤100 vs. 101-200. In addition, a sensitivity analysis was performed that estimated the 60-day death rate with hypothesis testing based on the Kaplan-Meier estimates and standard errors estimated by Greenwood formula using the log-log transformation of the survival function stratified by the baseline imputed PaO2/FiO2 of ≤100 vs. 101-200.
To protect the trial level type 1 error rate at α=5% (two sided) between the primary endpoint analysis and the key secondary endpoint analysis, the Benjamini and Hochberg testing strategy was used as test statistics of time to recovery and all-cause mortality at Day 60 were positively correlated.
Role of funding source
The funder of the study had primary responsibility for the study design, protocol development, study monitoring, data management and interpretation, and statistical analyses. The funder also contributed to the drafting of the manuscript and decision to submit.