Celltrion Healthcare Co., Ltd. announced new results from an in vivo efficacy study showing that regdanvimab (CT-P59) has a strong neutralising effect against the rapidly spreading Delta variant. The pre- clinical in vivo study assessed the neutralisation effect of CT-P59 against the Delta variant, using a clinically relevant dose. The study demonstrated that CT-P59 treatment results in a 100% survival rate from COVID-19 compared to 0% for the placebo group, with significant protection against body weight loss shown after viral challenge also seen. In addition, a therapeutic dosage of CT-P59 significantly reduced the viral load of SARS-CoV-2 and inflammation in the lungs compared to non-treated controls with virus eradication from all animals treated with CT-P59. Taken together, CT-P59 has shown in vivo efficacy against Delta variant following Beta (B.1.351, first identified in South Africa)2 and Gamma variant (P.1, first identified in Brazil)3, which was comparable to that against wild type SARS-CoV-2, thus demonstrating that despite the reduced in vitro neutralising activity against Variants of Concern (VOC), CT-P59 retained its therapeutic potency in vivo setting. The monoclonal antibody CT-P59 also demonstrated strong neutralising capability against the Lambda variant (C.37,first identified in Peru) in a cell-based pseudo- virus assay study performed by the National Institutes of Health (NIH), U.S.