Quick Review: Effectiveness of REGEN-COV antibody cocktail against B.1.617.2 (delta) variant of SARS-CoV-2

Casirivimab plus imdevimab antibody cocktail (REGEN-COV) has been shown to reduce viral load and prevent symptomatic disease in household contacts of infected people. The objective of this study was to assess the effectiveness of cocktail antibody therapy in high-risk SARS-CoV-2-positive patients.

A single-center prospective observational cohort study included 285 high-risk, RT-PCR-positive SARS-CoV-2 patients, presenting within 7 days from the onset of symptoms. Patients were assigned in a nonrandomized manner to either cocktail group (monoclonal antibody [mAb]; n = 208), which received casirivimab and imdevimab (600 mg each/100 ml saline), or the standard-of-care (SOC; n = 78) group, which received remdesivir (200 mg on Day 1 and 100 mg/day from Days 2–5), based on their choice of therapy. The primary aim was to assess the amount of time taken for resolution of symptoms and change in viral load from baseline through Day 7 (interpreted by Ct values). The results are as followed;

• The mean age (56.46 ± 15.77 vs. 53.51 ± 15 years; p = 0.15), sex (male; 56.52% vs. 57.69%), majority (>98.0%) of patients harbored delta variant (B.1.617.2) comparable to the prevalence in community.
• The number of symptomatic individuals on Day 7 was significantly lower in the cocktail group than in the SOC group (23/108 [21.30%] vs. 39/78 [50.0%]; p = 0.0001).
• Fewer patients tested positive by RT-PCR on Day 7 in cocktail group than in SOC group (28/108 [25.0%] vs. 26/50 [52.0%]; p = 0.0001).
• Among the inflammatory markers, serum ferritin levels (p = 0.027) and absolute neutrophil counts (p = 0.020) were significantly increased on Day 7 in the SOC group.
• A greater increase (1.5 vs. 1.27-fold) in absolute lymphocyte counts was also noted in the cocktail group.
• No mortality/ progression to severe disease was seen in either of the groups on Day 28
• Mean Ct values in those who tested positive were not significantly different between the groups on Day 7, the increase in Ct values was significantly higher in the cocktail group (p = 0.003 [RDRP gene]; p = 0.006 [N gene]).

REGEN-COV antibody cocktail treatment and implications
• Faster resolution of symptoms by Day 3 - indicates an enhanced benefit against worsening in high-risk patients.
• Significantly lower RT-PCR positivity on Day 7 and higher increase in Ct values – reveal enhanced viral clearance.
• Lower serum ferritin and neutrophil counts but higher lymphocyte counts on Day 7 - improved inflammatory profile in the cocktail group.
• Ability to block the entry of delta variant - reducing the viral load.

REGEN-COV antibody cocktail-treated high-risk SARS-CoV-2 patients infected with the delta variant showed faster resolution of symptoms along with reduced viral loads.

Reference:

Kumar V J, Banu S, Sasikala M, Parsa KVL, Sowpati DT, Yadav R, Tallapaka KB, Siva AB, Vishnubhotla R, Rao GV, Reddy DN. Effectiveness of REGEN-COV antibody cocktail against the B.1.617.2 (delta) variant of SARS-CoV-2: A cohort study. J Intern Med. 2021 Nov 1. doi: 10.1111/joim.13408. Epub ahead of print.

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