Real-world evidence to supplement randomized clinical trials: Tocilizumab for severe COVID-19 pneumonia versus a cohort receiving standard of care.

Randomized controlled trials (RCT) remain the gold standard for evaluating treatment efficacy, but real-world evidence can supplement RCT results. Tocilizumab was not found to reduce 28-day mortality in a phase 3, double-blind, placebo-controlled trial (COVACTA) among hospitalized patients with severe COVID-19 pneumonia. We created a real-world external comparator arm mirroring the COVACTA trial to confirm findings and assess the feasibility of using an external comparator arm to supplement an RCT. Eligible COVACTA participants in both the tocilizumab treatment and placebo arms were matched 1:1 using propensity score matching to persons without tocilizumab exposure in an external comparator arm. Adjusted Cox proportional hazard models estimated differences in 28-day mortality comparing COVACTA participants to matched external comparator arm participants. Patients in the COVACTA tocilizumab treatment arm had a similar risk of death compared to patients in the external comparator arm (hazard ratio [HR], 1.09, 95% confidence interval [CI], 0.64-1.84) with similar estimated 28-day mortality in the COVACTA tocilizumab treatment arm compared to the external comparator arm (18%, CI 13-24 versus 19%, CI 13-24; p >0.9). COVACTA placebo treatment arm participants had a similar risk of mortality (aHR 0.69; CI 0.32-1.46) compared to the external comparator arm. Using an external comparator arm has the potential to supplement RCT data and support results of primary RCT analyses.