New phase III data shows investigational antibody cocktail casirivimab and imdevimab reduced hospitalisation or death by 70% in non-hospitalised patients with COVID-19

Regeneron, Press Release, Mar 2021
Death/hospitalization 71% improvement lower risk ← → higher risk Death/hospitalization b 70% Recovery time 29% Recovery time b 29% Casirivimab/i..  Regeneron et al.  EARLY TREATMENT RCT Is early treatment with casirivimab/imdevimab beneficial for COVID-19? RCT 2,696 patients in the USA Lower death/hosp. (p<0.0001) and faster recovery (p=0.0001) c19early.org Regeneron, Press Release, March 2021 0 0.5 1 1.5 2+ RR
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.
No treatment is 100% effective. Protocols combine treatments.
6,300+ studies for 210+ treatments. c19early.org
Press release for new phase III data showing lower hospitalization/mortality, and faster symptom resolution among the subset of patients with at least one risk factor.
Some variants may escape antibodies1.
Efficacy is variant dependent. In Vitro research suggests a lack of efficacy for many omicron variants2-8.
Standard of Care (SOC) for COVID-19 in the study country, the USA, is very poor with very low average efficacy for approved treatments9. Only expensive, high-profit treatments were approved for early treatment. Low-cost treatments were excluded, reducing the probability of early treatment due to access and cost barriers, and eliminating complementary and synergistic benefits seen with many low-cost treatments.
risk of death/hospitalization, 71.3% lower, RR 0.29, p < 0.001, treatment 18 of 1,355 (1.3%), control 62 of 1,341 (4.6%), NNT 30, 2,400mg IV, ≥1 risk factor.
risk of death/hospitalization, 70.4% lower, RR 0.30, p = 0.003, treatment 7 of 736 (1.0%), control 24 of 748 (3.2%), NNT 44, 1,200mg IV, ≥1 risk factor.
recovery time, 28.6% lower, relative time 0.71, p < 0.001, treatment 1,355, control 1,341, 2,400mg IV, ≥1 risk factor.
recovery time, 28.6% lower, relative time 0.71, p < 0.001, treatment 736, control 748, 1,200mg IV, ≥1 risk factor.
Effect extraction follows pre-specified rules prioritizing more serious outcomes. Submit updates
Regeneron et al., 23 Mar 2021, Randomized Controlled Trial, USA, preprint, 1 author.
$0 $500 $1,000+ Efficacy vs. cost for COVID-19 treatment protocols c19early.org December 2025 USA Russia Sudan Angola Colombia Kenya Mozambique Vietnam Peru Philippines Spain Brazil Italy France Japan Canada China Uzbekistan Nepal Ethiopia Iran Ghana Mexico South Korea Germany Bangladesh Saudi Arabia Algeria Morocco Yemen Poland India DR Congo Madagascar Thailand Uganda Venezuela Nigeria Egypt Bolivia Taiwan Zambia Fiji Bosnia-Herzegovina Ukraine Côte d'Ivoire Bulgaria Greece Slovakia Singapore Iceland New Zealand Czechia Mongolia Israel Trinidad and Tobago Hong Kong North Macedonia Belarus Qatar Panama Serbia CAR USA favored high-profit treatments.The average efficacy of treatments was very low.High-cost protocols reduce early treatment, andforgo complementary/synergistic benefits. More effective More expensive 75% 50% 25% ≤0%
$0 $500 $1,000+ Efficacy vs. cost for COVID-19treatment protocols worldwide c19early.org December 2025 USA Russia Sudan Angola Colombia Kenya Mozambique Vietnam Peru Philippines Spain Brazil Italy France Japan Canada China Uzbekistan Nepal Ethiopia Iran Ghana Mexico South Korea Germany Bangladesh Saudi Arabia Algeria Morocco Yemen Poland India DR Congo Madagascar Thailand Uganda Venezuela Nigeria Egypt Bolivia Taiwan Zambia Fiji Ukraine Côte d'Ivoire Eritrea Bulgaria Greece Slovakia Singapore New Zealand Malawi Czechia Mongolia Israel Trinidad and Tobago North Macedonia Belarus Qatar Panama Serbia Syria USA favored high-profit treatments.The average efficacy was very low.High-cost protocols reduce early treatment,and forgo complementary/synergistic benefits. More effective More expensive 75% 50% 25% ≤0%
Please send us corrections, updates, or comments. c19early involves the extraction of 200,000+ datapoints from thousands of papers. Community updates help ensure high accuracy. Treatments and other interventions are complementary. All practical, effective, and safe means should be used based on risk/benefit analysis. No treatment or intervention is 100% available and effective for all current and future variants. We do not provide medical advice. Before taking any medication, consult a qualified physician who can provide personalized advice and details of risks and benefits based on your medical history and situation. IMA and WCH provide treatment protocols.
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