Effectiveness of casirivimab and imdevimab, and sotrovimab during Delta variant surge: a prospective cohort study and comparative effectiveness randomized trial
Authors: Huang David T. , McCreary Erin K. , Bariola J. Ryan , Minnier Tami E. , Wadas Richard J. , Shovel Judith A. , Albin Debbie , Marroquin Oscar C. , Kip Kevin E. , Collins Kevin , Schmidhofer Mark , Wisniewski Mary Kay , Nace David A. , Sullivan Colleen , Axe Meredith , Meyers Russell , Weissman Alexandra , Garrard William , Peck-Palmer Octavia M. , Wells Alan , Bart Robert D. , Yang Anne , Berry Lindsay R. , Berry Scott , Crawford Amy M. , McGlothlin Anna , Khadem Tina , Linstrum Kelsey , Montgomery Stephanie K. , Ricketts Daniel , Kennedy Jason N. , Pidro Caroline J. , Zapf Rachel L. , Kip Paula L. , Haidar Ghady , Snyder Graham M. , McVerry Bryan J. , Yealy Donald M. , Angus Derek C. , Seymour Christopher W. 
Published: December 2021

AbstractIMPORTANCEThe effectiveness of monoclonal antibodies (mAbs), casirivimab and imdevimab, and sotrovimab, for patients with mild to moderate COVID-19 from the Delta variant is unknown.OBJECTIVETo evaluate the effectiveness of mAbs for the Delta variant compared to no treatment, and the comparative effectiveness between mAbs.DESIGN, SETTING, AND PARTICIPANTSTwo parallel studies among patients who met Emergency Use Authorization criteria for mAbs from July 14, 2021 to September 29, 2021: i.) prospective observational cohort study comparing mAb treatment to no mAb treatment and, ii.) Bayesian adaptive randomized trial comparing the effectiveness of casirivimab-imdevimab versus sotrovimab. In the observational study, we compared eligible patients who received mAb at an outpatient infusion center at UPMC, to nontreated patients with a positive SARS-CoV-2 test. In the comparative effectiveness trial, we randomly allocated casirivimab-imdevimab or sotrovimab to patients presenting to infusion centers and emergency departments, per system therapeutic interchange policy.EXPOSUREIntravenous mAb per their EUA criteria.MAIN OUTCOMES AND MEASURESFor the observational study, risk ratio estimates for hospitalization or death by 28 days were compared between mAb treatment to no mAb treatment using propensity matched models. For the comparative effectiveness trial, the primary outcome was hospital-free days (days alive and free of hospital) within 28 days, where patients who died were assigned -1 day) in a Bayesian cumulative logistic model, adjusted for treatment location, age, sex, and time. Inferiority was defined as a 99% posterior probability of an odds ratio <1. Equivalence was defined as a 95% posterior probability that the odds ratio is within a given bound.RESULTSAmong 3,558 patients receiving mAb, the mean age was 54 (SD 18 years), 1,511 (43%) were treated in an infusion center, and 450 (13%) were hospitalized or died by day 28. In propensity matched models, mAb treatment was associated with reduced risk of hospitalization or death compared to no treatment (risk ratio (RR)=0.40, 95% CI: 0.28–0.57). Both casirivimab and imdevimab (RR=0.31, 95% CI: 0.20–0.50), and sotrovimab (RR=0.60, 95% CI: 0.37–1.00) reduced hospitalization or death compared to no mAb treatment. Among patients allocated randomly to casirivimab and imdevimab (n=2,454) or sotrovimab (n=1,104), the median hospital-free days were 28 (IQR 28–28) for both groups, 28-day mortality was 0.5% (n=12) and 0.6% (n=7), and hospitalization by day 28 was 12% (n=291) and 12% (n=140), respectively. Compared to casirivimab and imdevimab, the median adjusted odds ratio for hospital-free days was 0.88 (95% credible interval, 0.70–1.11) for sotrovimab. This odds ratio yielded 86% probability of inferiority of sotrovimab versus casirivimab and imdevimab, and 79% probability of equivalence.CONCLUSIONS AND RELEVANCEIn non-hospitalized patients with mild to moderate COVID-19 due to the Delta variant, casirivimab and imdevimab and sotrovimab were both associated with a reduced risk of hospitalization or death. The comparative effectiveness of mAbs appeared similar, though prespecified criteria for statistical inferiority or equivalence were not met.TRIAL REGISTRATIONClinicalTrials.gov: NCT04790786Key PointsQuestionIn non-hospitalized patients with mild to moderate COVID-19 due to the Delta variant, what is the effectiveness of monoclonal antibodies (mAb) compared to no treatment, and what is the comparative effectiveness between mAb?FindingsAmong 3,069 patients, mAb treatment (casirivimab and imdevimab or sotrovimab) was associated with reduced risk of hospitalization or death by 28 days compared to no treatment (risk ratio=0.40, 95% CI: 0.28–0.57). In a Bayesian randomized comparative effectiveness trial of casirivimab and imdevimab vs. sotrovimab in 3,558 patients, the median hospital–free days were 28 days for both groups. Compared to casirivimab-imdevimab, the median adjusted odds ratio for hospital-free days was 0.88 (95% credible interval, 0.70–1.11) for sotrovimab, an 86% probability of inferiority of sotrovimab versus casirivimab and imdevimab, and 79% probability of equivalence.MeaningIn non-hospitalized patients with mild to moderate COVID-19 due to the Delta variant, casirivimab and imdevimab and sotrovimab were associated with reduced risk of hospitalization or death compared to no treatment. The comparative effectiveness of mAbs appeared similar, though prespecified criteria for statistical inferiority or equivalence were not met.