Casirivimab and Imdevimab Treatment in Seropositive, Hospitalized COVID-19 Patients With Non-neutralizing or Borderline Neutralizing Antibodies

We conducted a post-hoc analysis in seropositive patients who were negative or borderline for functional neutralizing antibodies (nAbs) against SARS-CoV-2 at baseline from a phase 1/2/3 trial of casirivimab and imdevimab (CAS+IMD) treatment in hospitalized COVID-19 patients on low-flow or no supplemental oxygen prior to the emergence of Omicron-lineage variants. Patients were randomized to a single dose of 2.4 g CAS+IMD, 8.0 g CAS+IMD, or placebo. Patients seropositive for anti-SARS-CoV-2 antibodies at baseline were analyzed by their baseline nAb status. At baseline, 20.6% (178/864) of seropositive patients were negative/borderline for nAbs. CAS+IMD reduced viral load in patients who were negative/borderline for nAbs versus placebo, but not in patients who were positive for nAbs. We observed a trend in reduction of the proportion of patients who died or required mechanical ventilation (MV), as well as in all-cause mortality, by day 29 with CAS+IMD versus placebo in patients who were negative/borderline for nAbs. In those who were negative/borderline for nAbs, the proportions who died/needed MV from days 1-29 were 19.1% and 10.9%, and the proportions of patients who died from days 1-29 were 16.2% and 9.1%, in the placebo and CAS+IMD combined dose groups, respectively. No measurable harm or benefit in death/MV or all-cause mortality was observed in patients who were positive for nAbs. In hospitalized COVID-19 patients on low-flow or no supplemental oxygen, CAS+IMD reduced viral load, the risk of death or MV, and all-cause mortality in seropositive patients who were negative/borderline for nAbs. ImportanceThe clinical benefit of CAS+IMD in hospitalized seronegative patients with COVID-19 has previously been demonstrated, although these studies observed no clinical benefit in seropositive patients. As the prevalence of SARS-CoV-2 seropositive individuals rises due to both vaccination and previous infection, it is important to understand whether there is a subset of hospitalized patients with COVID-19, who have antibodies against SARS-CoV-2, who could benefit from anti-SARS-CoV-2 monoclonal antibody treatment. This post-hoc analysis demonstrates that there is a subset of hospitalized, seropositive patients with inadequate SARS-CoV-2 nAbs (ie, those who were negative or borderline for nAbs) who may still benefit from CAS+IMD treatment if infected with a susceptible variant. Therefore, utilizing seronegativity status alone to guide treatment decisions for patients with COVID-19 may fail to identify seropositive patients who could benefit from anti-SARS-CoV-2 monoclonal antibody therapies which retain activity against circulating strains, depending on how effectively their endogenous antibodies neutralize SARS-CoV-2.

Effectiveness of Subcutaneous Casirivimab and Imdevimab Relative to no COVID-19 Antibody Treatment Among Patients Diagnosed With COVID-19 in the Ambulatory Setting

ImportanceData on real-world effectiveness of subcutaneous (SC) administration of casirivimab and imdevimab (CAS+IMD) for treatment of COVID-19 are limited. ObjectiveTo assess effectiveness of SC CAS+IMD vs no COVID-19 antibody treatment among patients diagnosed with COVID-19 in ambulatory settings during the Delta-dominant period prior to Omicron emergence. DesignRetrospective cohort study. SettingEncrypted linked data between Komodo Health closed claims database and CDR Maguire Health & Medical database. ParticipantsPatients with COVID-19 in ambulatory settings between August 1, 2021 and October 30, 2021 treated with SC CAS+IMD were exact- and propensity score-matched to up to 5 untreated patients who were treatment-eligible under the Emergency Use Authorization (EUA) ExposureSubcutaneous CAS+IMD. Main Outcomes and MeasuresComposite endpoint of 30-day all-cause mortality or COVID- 19-related hospitalization. Kaplan-Meier estimators were used to calculate composite risk overall and across subgroups including age, COVID-19 vaccination status, immunocompromised, and elevated risk defined as age [≥] 65 years or 55-64 years with body mass index [≥] 35 kg/m2, type 2 diabetes, chronic obstructive pulmonary disease, or chronic kidney disease. Cox proportional- hazards models were used to estimate adjusted hazard ratios (aHR) and 95% confidence intervals (CI). ResultsAmong 13 522 patients treated with SC CAS+IMD, 12 972 (95.9%) were matched to 41 848 EUA-eligible untreated patients; patients were 57-58% female, with mean age between 50 and 52 years. The 30-day composite outcome risk was 1.9% (95% CI, 1.7-2.2; 247 events) and 4.4% (95% CI, 4.2-4.6; 1822 events) in the CAS+IMD-treated and untreated cohorts, respectively; CAS+IMD treatment was associated with a 49% lower risk (aHR 0.51; 95% CI, 0.46-0.58). Treatment was also associated with a 67% lower 30-day risk of all-cause mortality (aHR 0.33, 95% CI, 0.18-0.60). Treatment effectiveness was consistent regardless of vaccination status and across subgroups, including those at elevated risk (aHR 0.51, 95% CI 0.42-0.60) or immunocompromised (aHR 0.34, 95% CI 0.17-0.66). Conclusions and RelevanceSubcutaneous treatment with CAS+IMD is effective for reducing all-cause mortality or COVID-19-related hospitalization in patients diagnosed with COVID-19 and managed in real-world outpatient settings during the Delta-dominant period. Effectiveness is maintained among immunocompromised, vaccinated, and elevated risk patients.

Real-World Effectiveness of Casirivimab and Imdevimab Among Patients Diagnosed With COVID-19 in the Ambulatory Setting: A Retrospective Cohort Study Using a Large Claims Database

ImportanceData on real-world effectiveness of casirivimab and imdevimab (CAS+IMD) for treatment of coronavirus 2019 (COVID-19) are limited, especially with regard to variants of concern such as Delta. ObjectiveTo assess effectiveness of CAS+IMD versus no COVID-19 antibody treatment among patients diagnosed with COVID-19 in the ambulatory setting overall and among subgroups, including patients diagnosed during the Delta-dominant period prior to Omicron emergence. DesignRetrospective cohort study. SettingKomodo Health closed claims database. ParticipantsPatients diagnosed with COVID-19 in ambulatory settings from December 2020 through September 2021 treated with CAS+IMD or untreated but treatment-eligible under the Emergency Use Authorization (EUA). Each treated patient was exact- and propensity score-matched without replacement to up to 5 untreated EUA-eligible patients. ExposureCAS+IMD treatment. Main Outcomes and MeasuresComposite endpoint of 30-day all-cause mortality or COVID-19-related hospitalization. Kaplan-Meier estimators were used to calculate risk of outcome overall and across subgroups defined by age groups, COVID-19 vaccination status, immunocompromised, and timing of COVID-19 diagnosis (December 2020 to June 2021, and July 2021 to September 2021). Cox proportional-hazards models were used to estimate adjusted hazard ratios (aHR) and 95% confidence intervals (95% CI). ResultsAmong 75 159 patients treated with CAS+IMD and 1 670 338 EUA-eligible untreated patients, 73 759 treated patients were matched to 310 688 untreated patients; matched patients had an average age [~]50 years, approximately 60% were women and were generally well-balanced across risk factors. The 30-day risk of the composite outcome was 2.1% and 5.2% in the CAS+IMD -treated and untreated patients, respectively; CAS+IMD treatment was associated with a 60% lower risk of the outcome (aHR 0.40; 95% CI, 0.38-0.42). The effect of CAS+IMD treatment was consistent across subgroups, including those who received a COVID-19 vaccine (aHR 0.48, 95% CI, 0.41-0.56), and those diagnosed during the Delta-dominant period (aHR 0.40, 95% CI, 0.38-0.42). Conclusions and RelevanceThe real-world effectiveness of CAS+IMD is consistent with the efficacy for reducing all-cause mortality or COVID-19-related hospitalization reported in clinical trials. Effectiveness is maintained across patient subgroups, including those who may be prone to breakthrough infections, and was effective against susceptible variants including Delta.{square}

Real-world Effectiveness of Casirivimab and Imdevimab in Patients With COVID-19 in the Ambulatory Setting: An Analysis of Two Large US National Claims Databases

Background In a phase III clinical trial, casirivimab and imdevimab (CAS+IMD) reduced the composite endpoint of COVID-19-related hospitalizations or all-cause mortality in outpatients at risk of severe disease. This study assessed real-world effectiveness of CAS+IMD. Methods Data from Optum(R) Clinformatics(R) Data Mart (CDM) and IQVIA Pharmetrics Plus (PMTX+) were used to identify patients diagnosed with COVID-19 in ambulatory settings between December 2020 and March 2021 (PMTX+) and June 2021 (CDM), and either treated with CAS+IMD or untreated but treatment-eligible under Emergency Use Authorization. CAS+IMD-treated patients were matched to untreated patients and followed up to 30 days for the outcome of all-cause mortality or COVID-19-related hospitalizations (CDM) and COVID-19-related hospitalizations (PMTX+). Kaplan-Meier estimators were used to calculate outcome risks; Cox proportional-hazard models estimated adjusted hazard ratios (aHR) with 95% confidence intervals (CI). Results For CDM, 1116 CAS+IMD-treated patients were matched to 5294 untreated patients; for PMTX+, 3280 CAS+IMD-treated patients were matched to 16,284 untreated patients. The 30-day outcome risk was 2.1% and 5.3% in treated and untreated cohorts, respectively (CDM), and the 30-day risk of COVID-19-related hospitalization was 1.9% and 4.8%, respectively (PMTX+); translating to a 61% lower adjusted outcome risk (CDM aHR 0.39 (95% CI 0.26-0.60; PMTX+ aHR 0.39 (95% CI 0.30-0.51). The benefit of treatment was maintained across multiple subgroups of high-risk patients; earlier intervention was associated with improved outcomes. Conclusions This real-world study further supports randomized clinical trial findings that treatment with CAS+IMD reduces the risk of hospitalization and mortality in patients infected with susceptible variants.

Phase 2 dose-ranging study of the virologic efficacy and safety of the combination COVID-19 antibodies casirivimab and imdevimab in the outpatient setting

BackgroundThe monoclonal antibody combination casirivimab and imdevimab (REGEN-COV(R)) reduced viral load, hospitalisation, or death when administered 1:1 as an intravenous (IV) dose [≥]1200 mg in a phase 3 COVID-19 outpatient study. Availability of subcutaneous (SC) and/or lower IV doses should increase accessibility and/or drug supplies for patients. MethodsThis is a double-blind, placebo-controlled study of SARS-CoV-2-infected outpatients who were asymptomatic, or symptomatic but without risk factors for severe COVID-19. Patients were randomised to single IV dose (517 patients) of REGEN-COV 300, 600, 1200 or 2400 mg or placebo; or a single SC dose (286 patients) of REGEN-COV 600 or 1200 mg or placebo. The primary endpoint was time-weighted average daily change from baseline (TWACB) in viral load from day 1 (baseline) through day 7 in patients seronegative to SARS-CoV-2 at baseline. FindingsAll REGEN-COV treatments showed significant (p<0{middle dot}001 versus pooled placebo) virologic reduction through day 7. Least-squares mean differences in TWACB viral load for the treatments versus placebo ranged from -0{middle dot}56 to -0{middle dot}71 log10 copies/mL. Each REGEN-COV treatment showed significant (p<0{middle dot}001 versus pooled placebo) and similar virologic reduction through day 7. There were no safety concerns, dose-related safety findings, grade [≥]2 infusion related/hypersensitivity reactions, grade [≥]3 injection-site reactions, nor fatalities. Two serious adverse events not related to COVID-19 or the study drug were reported. InterpretationIn asymptomatic and low-risk symptomatic SARS-CoV-2-infected outpatients seronegative for antibodies against SARS-CoV-2 at baseline, REGEN-COV significantly and comparably reduced viral load at all IV and SC doses. FundingRegeneron Pharmaceuticals, Inc. and Hoffman-La Roche RESEARCH IN CONTEXTO_ST_ABSEvidence before this studyC_ST_ABSEarly phase 1/2 data in coronavirus disease 2019 (COVID-19) outpatients (NCT04425629) found that the REGEN-COV(R) antibody combination, casirivimab and imdevimab, administered 1:1 as a single intravenous (IV) dose of 2400 mg or 8000 mg significantly reduced viral load over the first week compared to placebo. Enhanced viral clearance was more pronounced in patients who were seronegative for antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), or who had high viral load at baseline. The phase 3 portion of this outpatient treatment study subsequently evaluated 1200 mg IV and 2400 mg IV doses, demonstrating consistent virologic efficacy, further demonstrating that REGEN-COV treatment reduced risk of COVID-19-related hospitalisation or all-cause death, and shortened time to symptom resolution. Virologic clearance was similar among those treated with any of the three doses (8000 mg, 2400 mg, or 1200 mg); therefore, maximal virologic efficacy may have been achieved at the 1200 mg dose in this treatment setting. These results warranted investigation of lower dose regimens. Added value of this studyThe present dose-ranging study evaluated whether a lower dose regimen could demonstrate virologic efficacy similar to that observed with 1200 mg IV and 2400 mg IV doses in outpatient treatment study. Exploration of a wider dose range will provide further characterisation of the clinical effects of REGEN-COV. Moreover, identifying a lower efficacious dose could bolster the ability to provide an adequate therapeutic supply of REGEN-COV in the setting of a global pandemic. A 1200 mg subcutaneous (SC) dose of REGEN-COV also prevented COVID-19 in household contacts of SARS-CoV-2-infected individuals (NCT04452318). The availability of a SC regimen could improve access for patients who have confirmed SARS-CoV-2 infection but for who IV infusion is not feasible. Implications of all the available evidenceDespite the growing number of therapeutics with authorisation or approval for the treatment and/or prevention of COVID-19, there remains a significant global need for effective COVID-19 therapies. Additional therapeutics and dosing regimens will be required to meet demand and to meet the needs of specific patient populations. Lower IV doses of REGEN-COV, and the option of SC administration, should increase accessibility for patients. This increased availability needs to be weighed against several unanswered questions, including 1) whether the correlation between decreased viral load in the nasopharynx and improvement in clinical outcome holds at lower doses of REGEN-COV, and 2) whether the reduced drug exposure margins are sufficient to prevent viral escape and emergence of variants of concern.

Compassionate Use of REGEN-COV(R) in Patients with COVID-19 and Immunodeficiency-Associated Antibody Disorders

BackgroundPatients with immunodeficiency-associated antibody disorders are at a higher risk of prolonged/persistent COVID-19 infection, having no viable treatment options. MethodsThis is a retrospective analysis of patients with primary and/or secondary immunodeficiency-associated antibody disorders who received casirivimab and imdevimab (REGEN-COV(R)) under emergency compassionate use. The objectives were to describe safety and response to REGEN-COV, with a focus on the subset of patients who had COVID-19 duration [≥]21 days prior to treatment. Quantitative (change in oxygenation status and/or viral load) and/or qualitative (physician-reported clinical status) patient outcomes data are reported. ResultsOutcome data are available from 64 patients who received REGEN-COV. Improvement in [≥]1 outcome measure was observed in 90.6% of the overall patient group. Thirty-seven of these patients had COVID-19 duration [≥]21 days prior to treatment, with a median time from RT-PCR diagnosis to REGEN-COV administration of 60.5 days. Of the 29 patients with COVID-19 duration [≥]21 days prior to treatment who had available outcome data, 96.6% showed improvement in [≥]1 outcome measure evaluated following use of REGEN-COV. In the 14 patients who had post-treatment RT-PCR results available, 11 (78.6%) reported a negative RT-PCR following treatment with REGEN-COV, with 5 patients (45.5%) reporting a negative RT-PCR within 5 days of treatment and 8 (72.7%) reporting a negative RT-PCR within 21 days of treatment. ConclusionsIn this retrospective analysis of immunodeficient patients who were granted REGEN-COV under the compassionate use program, REGEN-COV treatment was associated with rapid viral clearance and clinical improvement in the evaluable patients with long-standing COVID-19. SummaryPatients with immunodeficiency-associated antibody disorders are at a higher risk of prolonged/persistent COVID-19 infection. In this retrospective analysis, compassionate use of REGEN-COV in such patients was associated with rapid viral clearance and/or clinical improvement in the evaluable patients.

REGEN-COV for the Treatment of Hospitalized Patients with Covid-19

BackgroundHospitalized patients with COVID-19 experience high mortality rates, ranging from 10% to 30%. Combined casirivimab and imdevimab (CAS+IMD) is authorized for use in outpatients with COVID-19 and in post-exposure prophylaxis. The UK-based platform RECOVERY study reported improved survival in hospitalized seronegative patients treated with CAS+IMD; however, in most of the world, anti-spike monoclonal antibody therapy is currently not approved for hospitalized patients. MethodsIn this phase I/II/III double-blind placebo-controlled trial, patients hospitalized with COVID-19 were randomized (1:1:1) to 2.4 g or 8.0 g of CAS+IMD or placebo, and characterized at baseline for viral load and SARS-CoV-2 endogenous immune response. Results1336 patients on low-flow or no supplemental oxygen were treated. The primary endpoint was met: in seronegative patients, the least squares mean difference (CAS+IMD vs placebo) for time-weighted average change from baseline viral load was -0.28 log10 copies/mL (95% confidence interval [CI] -0.51 to -0.05; P = .0172). The primary clinical analysis of death or mechanical ventilation from day 6 to 29 in patients with high viral load had a strong positive trend but did not reach significance. CAS+IMD numerically reduced all-cause mortality in seronegative patients through day 29 (relative risk reduction, 55.6%; 95% CI 24.2-74.0; nominal P = .0032). No safety concerns were noted. ConclusionsIn hospitalized patients with COVID-19 on low-flow or no oxygen, CAS+IMD treatment reduced viral load and the risk of death or mechanical ventilation as well as all-cause mortality in the overall population, with the benefit driven by seronegative patients and no harm observed in seropositive patients.

Subcutaneous REGEN-COV Antibody Combination for Covid-19 Prevention

BackgroundCasirivimab and imdevimab (REGEN-COV) markedly reduces risk of hospitalization or death in high-risk individuals with Covid-19. Here we explore the possibility that subcutaneous REGEN-COV prevents SARS-CoV-2 infection and subsequent Covid-19 in individuals at high risk of contracting SARS-CoV-2 by close exposure in a household with a documented SARS-CoV-2-infected individual. MethodsIndividuals [≥]12 years were enrolled within 96 hours of a household contact being diagnosed with SARS-CoV-2 and randomized 1:1 to receive 1200 mg REGEN-COV or placebo via subcutaneous injection. The primary efficacy endpoint was the proportion of participants without evidence of infection (SARS-CoV-2 RT-qPCR- negative) or prior immunity (seronegative) who subsequently developed symptomatic SARS-CoV-2 infection during a 28-day efficacy assessment period. ResultsSubcutaneous REGEN-COV significantly prevented symptomatic SARS-CoV-2 infection compared with placebo (81.4% risk reduction; 11/753 [1.5%] vs. 59/752 [7.8%], respectively; P<0.0001), with 92.6% risk reduction after the first week (2/753 [0.3%] vs. 27/752 [3.6%], respectively). REGEN-COV also prevented overall infections, either symptomatic or asymptomatic (66.4% risk reduction). Among infected participants, the median time to resolution of symptoms was 2 weeks shorter with REGEN-COV vs. placebo (1.2 vs. 3.2 weeks, respectively), and the duration of time with high viral load (>104 copies/mL) was lower (0.4 vs. 1.3 weeks, respectively). REGEN-COV was generally well tolerated. ConclusionsAdministration of subcutaneous REGEN-COV prevented symptomatic Covid-19 and asymptomatic SARS-CoV-2 infection in uninfected household contacts of infected individuals. Among individuals who became infected, REGEN-COV reduced the duration of symptomatic disease, decreased maximal viral load, and reduced the duration of detectable virus. (ClinicalTrials.gov number, NCT04452318.)

Casirivimab and imdevimab in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

BackgroundREGEN-COV is a combination of 2 monoclonal antibodies (casirivimab and imdevimab) that bind to two different sites on the receptor binding domain of the SARS-CoV-2 spike protein. We aimed to evaluate the efficacy and safety of REGEN-COV in patients admitted to hospital with COVID-19. MethodsIn this randomised, controlled, open-label platform trial, several possible treatments were compared with usual care in patients hospitalised with COVID-19. Eligible and consenting patients were randomly allocated (1:1) to either usual standard of care alone (usual care group) or usual care plus a single dose of REGEN-COV 8g (casirivimab 4g and imdevimab 4g) by intravenous infusion (REGEN-COV group). The primary outcome was 28-day mortality assessed first among patients without detectable antibodies to SARS-CoV-2 at randomisation (seronegative) and then in the overall population. The trial is registered with ISRCTN (50189673) and clinicaltrials.gov (NCT04381936). FindingsBetween 18 September 2020 and 22 May 2021, 9785 patients were randomly allocated to receive usual care plus REGEN-COV or usual care alone, including 3153 (32%) seronegative patients, 5272 (54%) seropositive patients and 1360 (14%) patients with unknown baseline antibody status. In the primary efficacy population of seronegative patients, 396 (24%) of 1633 patients allocated to REGEN-COV and 451 (30%) of 1520 patients allocated to usual care died within 28 days (rate ratio 0{middle dot}80; 95% CI 0{middle dot}70-0{middle dot}91; p=0{middle dot}0010). In an analysis involving all randomised patients (regardless of baseline antibody status), 944 (20%) of 4839 patients allocated to REGEN-COV and 1026 (21%) of 4946 patients allocated to usual care died within 28 days (rate ratio 0{middle dot}94; 95% CI 0{middle dot}86-1{middle dot}03; p=0{middle dot}17). The proportional effect of REGEN-COV on mortality differed significantly between seropositive and seronegative patients (p value for heterogeneity = 0{middle dot}001). InterpretationIn patients hospitalised with COVID-19, the monoclonal antibody combination of casirivimab and imdevimab (REGEN-COV) reduced 28-day mortality among patients who were seronegative at baseline. FundingUK Research and Innovation (Medical Research Council) and National Institute of Health Research (Grant ref: MC_PC_19056).

Subcutaneous REGEN-COV Antibody Combination in Early SARS-CoV-2 Infection

ImportanceEasy-to-administer antiviral treatments may be used to prevent progression from asymptomatic infection to COVID-19 and to reduce viral carriage. ObjectiveEvaluate the efficacy and safety of subcutaneous casirivimab and imdevimab antibody combination (REGEN-COV) to prevent progression from early asymptomatic SARS-CoV-2 infection to COVID-19. DesignRandomized, double-blind, placebo-controlled, phase 3 study that enrolled asymptomatic close contacts living with a SARS-CoV-2-infected household member (index case). Participants who were SARS-CoV-2 RT-qPCR-positive at baseline were included in the analysis reported here. SettingMulticenter trial conducted at 112 sites in the United States, Romania, and Moldova. ParticipantsAsymptomatic individuals [≥]12 years of age were eligible if identified within 96 hours of collection of the index cases positive SARS-CoV-2 test sample. InterventionsA total of 314 asymptomatic, SARS-CoV-2 RT-qPCR-positive individuals living with an infected household contact were randomized 1:1 to receive a single dose of subcutaneous REGEN-COV 1200mg (n=158) or placebo (n=156). Main Outcome(s) and Measure(s)The primary endpoint was the proportion of participants who developed symptomatic COVID-19 during the 28-day efficacy assessment period. The key secondary efficacy endpoints were the number of weeks of symptomatic SARS-CoV-2 infection and the number of weeks of high viral load (>4 log10 copies/mL). Safety was assessed in all treated participants. ResultsSubcutaneous REGEN-COV 1200mg significantly prevented progression from asymptomatic to symptomatic disease compared with placebo (31.5% relative risk reduction; 29/100 [29.0%] vs 44/104 [42.3%], respectively; P=.0380). REGEN-COV reduced the overall population burden of high-viral load weeks (39.7% reduction vs placebo; 48 vs 82 total weeks; P=.0010) and of symptomatic weeks (45.3% reduction vs placebo; 89.6 vs 170.3 total weeks; P=.0273), the latter corresponding to an approximately 5.6-day reduction in symptom duration per symptomatic participant. Six placebo-treated participants had a COVID-19-related hospitalization or ER visit versus none for those receiving REGEN-COV. The proportion of participants receiving placebo who had [≥]1 treatment-emergent adverse events was 48.1% compared with 33.5% for those receiving REGEN-COV, including events related (39.7% vs 25.8%, respectively) or not related (16.0% vs 11.0%, respectively) to COVID-19. Conclusions and RelevanceSubcutaneous REGEN-COV 1200mg prevented progression from asymptomatic SARS-CoV-2 infection to COVID-19, reduced the duration of high viral load and symptoms, and was well tolerated. Trial RegistrationClinicalTrials.gov Identifier, NCT04452318 KEY POINTSO_ST_ABSQuestionC_ST_ABSCan treatment with the anti-SARS-CoV-2 antibody combination REGEN-COV prevent COVID-19 and reduce viral load when given to recently exposed and asymptomatic individuals? FindingsIn this randomized, double-blind, phase 3 trial, subcutaneously administered REGEN-COV 1200 mg significantly reduced progression of asymptomatic SARS-CoV-2 infection to symptomatic infection (ie, COVID-19) by 31.5% compared with placebo. REGEN-COV also reduced the overall population burden of high viral load weeks (39.7% reduction vs placebo; 48 vs 82 total weeks; P=.0010). MeaningIn the current pandemic, utilization of subcutaneous REGEN-COV prevents progression of early asymptomatic infection to COVID-19 and reduces viral carriage.

REGEN-COV Antibody Cocktail in Outpatients with Covid-19

BackgroundContinued SARS-CoV-2 infections and COVID-19-related hospitalizations highlight the need for effective anti-viral treatments in the outpatient setting. In a descriptive interim analysis of the phase 1/2 portion of a double-blind phase 1/2/3 trial in COVID-19 outpatients conducted between June 16, 2020 and September 4, 2020, REGEN-COV(R) (casirivimab plus imdevimab) antibody combination reduced SARS-CoV-2 viral load versus placebo. MethodsThis final phase 1/2 analysis comprises 799 outpatients, including 275 from the previous descriptive analysis (group-1) and 524 from phase 2 (group-2). Patients were randomized (1:1:1) to placebo, REGEN-COV 2400mg, or REGEN-COV 8000mg. Prespecified hierarchical analyses of virologic endpoints were performed in group-2. The proportion of patients with [≥]1 COVID-19-related medically attended visit (MAV) through day 29 was assessed in group-1+2. Efficacy was assessed in patients confirmed SARS-CoV-2-positive by baseline nasopharyngeal RT-qPCR. Safety was assessed in all treated patients. ResultsData from 799 outpatients enrolled from June 16, 2020 to September 23, 2020 are reported. Time-weighted average daily reduction in viral load through day 7 was significantly greater in the REGEN-COV combined 2400mg+8000mg group versus placebo in patients with baseline viral load >107 copies/mL (prespecified primary endpoint): -0.68 log10 copies/ml (95% CI, -0.94 to -0.41; P<.0001). This reduction was - 0.73 (P<.0001) and -0.36 (P=.0003) log10 copies/mL in serum antibody-negative patients and in the overall population, respectively. REGEN-COV reduced the proportion of patients with [≥]1 COVID-19-related MAV versus placebo (2.8% [12/434] REGEN-COV combined dose group versus 6.5% [15/231] placebo; P=.024; relative risk reduction [RRR]=57%); in patients with [≥]1 risk factor for hospitalization, the treatment effect was more pronounced (RRR=71%). Adverse events were similar across groups. ConclusionsIn COVID-19 outpatients enrolled prior to the widespread circulation of delta and omicron variants, treatment with REGEN-COV significantly reduced viral load and COVID-19-related MAVs.

In vitro and in vivo preclinical studies predict REGEN-COV protection against emergence of viral escape in humans

Monoclonal antibodies against SARS-CoV-2 are a clinically validated therapeutic option against COVID-19. As rapidly emerging virus mutants are becoming the next major concern in the fight against the global pandemic, it is imperative that these therapeutic treatments provide coverage against circulating variants and do not contribute to development of treatment emergent resistance. To this end, we investigated the sequence diversity of the spike protein and monitored emergence of minor virus variants in SARS-COV-2 isolates found in COVID-19 patients or identified from preclinical in vitro and in vivo studies. This study demonstrates that a combination of non-competing antibodies, REGEN-COV, not only provides full coverage against current variants of concern/interest but also protects against emergence of new such variants and their potential seeding into the population in a clinical setting.