New phase 3 analyses show that a single dose of REGEN-COV® (casirivimab and imdevimab) provides long-term protection against COVID-19

Regeneron, Press Release, NCT04452318, Nov 2021

18th treatment shown to reduce risk in March 2021, now with p = 0.000095 from 34 studies, recognized in 52 countries. Efficacy is variant dependent.

Lower risk for hospitalization, progression, recovery, cases, and viral clearance.

No treatment is 100% effective. Protocols combine treatments.

6,300+ studies for 210+ treatments. c19early.org

Meta Analysis

Long-term results for PEP RCT NCT04452318 (history), with 841 baseline seronegative casirivimab/imdevimab patients and 842 placebo patients, showing significantly lower cases with treatment.

Efficacy is variant dependent. In Vitro research suggests a lack of efficacy for many omicron variants1-7.

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risk of hospitalization, 92.3% lower, RR 0.08, p = 0.03, treatment 0 of 841 (0.0%), control 6 of 842 (0.7%), NNT 140, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), 8 months.

risk of case, 81.5% lower, RR 0.19, p < 0.001, treatment 20 of 841 (2.4%), control 108 of 842 (12.8%), NNT 9.6, months 1-8.

risk of case, 81.6% lower, RR 0.18, p < 0.001, treatment 7 of 841 (0.8%), control 38 of 842 (4.5%), NNT 27, months 2-8.

risk of hospitalization/ER, 88.9% lower, RR 0.11, p = 0.06, treatment 0 of 753 (0.0%), control 4 of 752 (0.5%), NNT 188, relative risk is not 0 because of continuity correction due to zero events (with reciprocal of the contrasting arm), day 29.

risk of symptomatic case, 81.4% lower, RR 0.19, p < 0.001, treatment 11 of 753 (1.5%), control 59 of 752 (7.8%), NNT 16, day 29.

recovery time, 62.5% lower, relative time 0.37, p < 0.001, treatment 753, control 752, short-term followup, relative time with symptoms.

time to viral-, 69.2% lower, relative time 0.31, p < 0.001, treatment 753, control 752, short-term followup, relative time with high viral load.

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1. Liu et al., Striking Antibody Evasion Manifested by the Omicron Variant of SARS-CoV-2, bioRxiv, doi:10.1101/2021.12.14.472719.biorxiv.org, doi.org.

2. Sheward et al., Variable loss of antibody potency against SARS-CoV-2 B.1.1.529 (Omicron), bioRxiv, doi:10.1101/2021.12.19.473354.biorxiv.org, doi.org.

3. VanBlargan et al., An infectious SARS-CoV-2 B.1.1.529 Omicron virus escapes neutralization by several therapeutic monoclonal antibodies, bioRxiv, doi:10.1101/2021.12.15.472828.biorxiv.org, doi.org.

4. Tatham et al., Lack of Ronapreve (REGN-CoV; casirivimab and imdevimab) virological efficacy against the SARS-CoV 2 Omicron variant (B.1.1.529) in K18-hACE2 mice, bioRxiv, doi:10.1101/2022.01.23.477397.biorxiv.org, doi.org.

5. Pochtovyi et al., In Vitro Efficacy of Antivirals and Monoclonal Antibodies against SARS-CoV-2 Omicron Lineages XBB.1.9.1, XBB.1.9.3, XBB.1.5, XBB.1.16, XBB.2.4, BQ.1.1.45, CH.1.1, and CL.1, Vaccines, doi:10.3390/vaccines11101533.mdpi.com, doi.org.

6. Haars et al., Prevalence of SARS-CoV-2 Omicron Sublineages and Spike Protein Mutations Conferring Resistance against Monoclonal Antibodies in a Swedish Cohort during 2022–2023, Microorganisms, doi:10.3390/microorganisms11102417.mdpi.com, doi.org.

7. Uraki et al., Antiviral efficacy against and replicative fitness of an XBB.1.9.1 clinical isolate, iScience, doi:10.1016/j.isci.2023.108147.sciencedirect.com, doi.org.

Regeneron et al., 8 Nov 2021, Double Blind Randomized Controlled Trial, multiple countries, preprint, 1 author, study period 13 July, 2020 - 4 October, 2021, trial NCT04452318 (history).