Celltrion has reported preliminary results from a pre-clinical study, which showed the anti-Covid-19 monoclonal antibody treatment regdanvimab (CT-P59) neutralised the South African variant (B.1.351) of SARS-CoV-2 in an in vivo model.

This study used a clinically relevant dose to evaluate the neutralisation effect of CT-P59 against the South African variant.

According to the results, the treatment showed a reduction in the binding affinity against the receptor-binding domain (RBD) in the three mutations (K417N, E484K and N501Y substitutions) of the South African variant.

Furthermore, CT-P59 demonstrated a low susceptibility against the South African variant in a live virus and pseudo-virus assay in vitro study.

In the study, no substantial difference was noticed in the respiratory viral infection in the upper and lower respiratory tracts on exposure to SARS-CoV-2 wild type and the South African variants.

Celltrion noted that the diminished effect in in vitro neutralisation of CT-P59 is not likely to compromise the in vivo therapeutic potency against the variant in the respiratory tract, especially at a clinical dose.

The CT-P59 treatment at a clinically relevant dose also lowered SARS-CoV-2 viral load significantly.

Celltrion Healthcare Medical and Marketing Division head Dr HoUng Kim said: “We are encouraged by the new data, which reinforces that Celltrion’s CT-P59 treatment could be effective against the South African variant and variant mutations.

“We have commenced the development of a neutralising antibody cocktail with CT-P59 against new emerging strains in the UK and South Africa and we will continue to further investigate the neutralising antibodies and other responses to protect against current SARS-CoV-2 strains and emerging variants.”

The company is currently analysing the efficacy and safety of CT-P59 in a global Phase III clinical trial being carried out in 13 countries including the US, Spain and Romania. This trial has concluded patient enrolment of 1,300 subjects.

Celltrion will also begin further studies to assess the neutralisation activity of CT-P59 against other emerging variants.