Trial Design and Oversight
In the Study of Tofacitinib in Hospitalized Patients with Covid-19 Pneumonia (STOP-COVID), we compared tofacitinib with placebo in patients with Covid-19 pneumonia. The trial protocol (available with the full text of this article at NEJM.org) was approved by the institutional ethics board at participating sites. The trial was conducted in accordance with Good Clinical Practice guidelines and the principles of the Declaration of Helsinki.
The trial was sponsored by Pfizer and was designed and led by a steering committee that included academic investigators and representatives from Pfizer. The trial operations and statistical analyzes were conducted by the Academic Research Organization of the Hospital Israelita Albert Einstein in São Paulo. An independent data and safety monitoring board reviewed unblinded patient-level data for safety on an ongoing basis during the trial. Pfizer provided the entire trial budget, which covered all trial-related expenses including but not limited to investigator fees, costs related to investigational product suppliers and importation, insurance, applicable taxes and fees, and funding to support the activities of the data and safety monitoring board.
All the authors vouch for the accuracy and completeness of the data and for the fidelity of the trial to the protocol. The trial committee members and participating investigators are listed in the Supplementary Appendix, available at NEJM.org.
The trial included patients 18 years of age or older who had laboratory-confirmed SARS-CoV-2 infection as determined on reverse-transcriptase – polymerase-chain-reaction (RT-PCR) assay before randomization, who had evidence of Covid-19 pneumonia on radiographic imaging (computed tomography or radiography of the chest), and who had been hospitalized for less than 72 hours. Information regarding the timing of the qualifying RT-PCR assay in relation to symptom onset is provided in Section S3.1 in the Supplementary Appendix. High-flow devices constituted the maximum oxygen support that was allowed for trial inclusion.
The main exclusion criteria were the use of noninvasive or invasive mechanical ventilation or extracorporeal membrane oxygenation (ECMO) on the day of randomization, a history of thrombosis or current thrombosis, known immunosuppression, and any current cancer for which the patient was receiving active treatment. Details of the eligibility criteria are provided in Section S3.2. Written informed consent was obtained from each patient or from the patient’s legally authorized representative if the patient was unable to provide informed consent.
Randomization, Interventions, and Follow-up
Eligible patients were randomly assigned in a 1: 1 ratio to receive either tofacitinib or placebo. Randomization, with stratification according to site, was performed with the use of a central concealed, Web-based, automated randomization system. Patients received either oral tofacitinib at a dose of 10 mg or placebo twice daily for up to 14 days or until hospital discharge, whichever was earlier. If a participant underwent intubation before the end of the 14-day treatment period (or before discharge), they continued to receive tofacitinib or placebo if it was considered to be clinically appropriate by the treating physicians. A reduced-dose regimen of 5 mg of tofacitinib (or matching placebo) twice daily was administered in patients with an estimated glomerular filtration rate of less than 50 ml per minute per 1.73 m2 of body-surface area, in those with moderate hepatic impairment, and in those with concomitant use of a strong CYP3A4 inhibitor or a combination of a moderate CYP3A4 inhibitor and a strong CYP2C19 inhibitor. The rationale for the tofacitinib dosage is provided in Section S3.3.
All the patients were treated according to local standards of care for Covid-19, which could have included glucocorticoids, antibiotic agents, anticoagulants, and antiviral agents. Concomitant use of other JAK inhibitors, biologic agents, potent immunosuppressants, interleukin-1 inhibitors, interleukin-6 inhibitors, or potent CYP450 inducers was prohibited. Patients were assessed daily (up to day 28) while hospitalized. Follow-up visits occurred on day 14 and on day 28 for participants who were discharged before day 14 or 28. Prespecified reasons for permanent discontinuation of the trial intervention are described in Section S3.4.
The primary outcome was death or respiratory failure during the 28 days of follow-up. Death or respiratory failure was determined to occur if participants met the criteria for category 6 (status of being hospitalized while receiving noninvasive ventilation or ventilation through high-flow oxygen devices), 7 (status of being hospitalized while receiving invasive mechanical ventilation or ECMO), or 8 (death) on the eight-level National Institute of Allergy and Infectious Diseases (NIAID) ordinal scale of disease severity (on a scale from 1 to 8, with higher scores indicating a worse condition) (Table S1 in the Supplementary Appendix) . Patients who were enrolled in the trial while they were receiving oxygen through high-flow devices (category 6) were considered to have met the criteria for the primary outcome if they presented with clinical worsening to category 7 or 8. The occurrence of the primary outcome was adjudicated by an independent clinical-events classification committee, whose members were unaware of the group assignments. The protocol and statistical analysis plan used an inverted ordinal scale, which was reversed in this report to be consistent with previous studies.
Secondary efficacy outcomes were the cumulative incidence of death through day 28, the scores on the NIAID ordinal scale of disease severity at day 14 and at day 28, the status of being alive and not using mechanical ventilation or ECMO at day 14 and day 28, the status of being alive and not hospitalized at day 14 and day 28, cure (defined as resolution of fever and cough and no use of ventilatory or oxygen support), the duration of stay in the hospital, and the duration of stay in the intensive care unit (ICU). The occurrence and severity of adverse events were evaluated and coded according to the Medical Dictionary for Regulatory Activities, version 23.1. Details of adverse event reporting, including the reporting of prespecified adverse events of special interest, are described in Section S3.5.
We estimated that the assignment of 260 patients, with randomization performed in a 1: 1 ratio, would provide the trial with 80% power to detect a between-group difference of 15 percentage points in the incidence of the primary outcome, assuming that 15% of the participants in the tofacitinib group and 30% of those in the placebo group would have an event (death or respiratory failure through day 28). The hypothesis of superiority was tested at a two-tailed alpha level of 5%. The efficacy analyzes included all the participants who underwent randomization. Safety analyzes included all the participants who underwent randomization and took at least one dose of tofacitinib or placebo.
The results for the primary efficacy outcome were analyzed by means of binary regression with Firth correction, with trial group and antiviral therapy for Covid-19 as covariates, and are expressed as a risk ratio. The antiviral treatments on day 1 were used in the statistical model. Dichotomous secondary outcomes were analyzed in a manner similar to that used for the primary outcome. The effect of the intervention on death through day 28 is expressed as a hazard ratio derived from Cox regression. For ordinal data, a proportional-odds model with adjustment for baseline antiviral therapy was used. An odds ratio of less than 1.0 represents a clinical improvement as assessed on the ordinal scale. Odds proportionality was assessed with the use of the method of Pulkstenis – Robinson.9 We created Kaplan – Meier survival curves to express the time until the occurrence of the primary outcome, both overall and stratified according to the use of supplemental oxygen at baseline, and the occurrence of death through 28 days.
As a sensitivity analysis, results for the primary outcome were analyzed by means of binary regression with Firth correction, with use of glucocorticoids and antiviral agents at baseline as covariates. In addition, results for the primary outcome were analyzed by means of logistic regression with Firth correction, with adjustment for baseline antiviral therapy. Prespecified subgroup analyzes were performed according to age, sex, concomitant use of antiviral therapy, concomitant use of glucocorticoids, and time from symptom onset to randomization.
For the primary outcome, a two-sided P value of less than 0.05 was considered to indicate statistical significance. The 95% confidence intervals were estimated for all effect measures. The widths of the 95% confidence intervals for the secondary outcomes were not adjusted for multiple comparisons, so the intervals should not be used to infer definitive treatment effects. All the analyzes were performed with the use of SAS software, version 9.4 (SAS Institute), and R software, version 3.6.3 (R Foundation for Statistical Computing). Additional details about the statistical analysis are provided in Section S3.6.