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AstraZeneca antibody fails to prevent COVID in exposed patients

Published on 15/06/21 at 10:36am

AstraZeneca has failed to reach the primary endpoint in their Storm Chaser trial, assessing the safety and efficacy of AZD7442, a long-acting antibody (LAAB) combination, for the prevention of symptomatic COVID-19 in participants recently exposed to the SARS-CoV-2 virus.

Trial participants were all unvaccinated adults with confirmed exposure to a person with a case of the SARS-CoV-2 virus within the past eight days. In the overall trial population, AZD7442 reduced the risk of developing symptomatic COVID-19 by 33% compared to placebo, which was not statistically significant.

The trial included 1,121 participants in a 2:1 randomisation AZD7442-to-placebo, with 23 cases of symptomatic COVID-19 accrued in the AZD7442 arm (23/749) and 17 cases accrued in the placebo arm (17/372).

All participants had a negative SARS-CoV-2 antibody test on the day of dosing to exclude prior infection, and a nasopharyngeal swab was also collected and subsequently analysed for SARS-CoV-2 using an RT-PCR.

Mene Pangalos, Executive Vice President, BioPharmaceuticals R&D, said: “While this trial did not meet the primary endpoint against symptomatic illness, we are encouraged by the protection seen in the PCR negative participants following treatment with AZD7442. We await results from PROVENT, our pre-exposure prevention trial and TACKLE, our treatment trial in preventing more severe disease, to understand the potential role of AZD7442 in protecting against COVID-19.”

AZD7442 is a combination of two LAABs - tixagevimab and cilgavimab - derived from B cells donated by convalescent patients after contracting the SARS-CoV-2 virus. Discovered by Vanderbilt University Medical Center and licensed to AstraZeneca in June 2020, the human monoclonal antibodies bind to distinct sites on the SARS-CoV-2 spike protein2 and were optimised by AstraZeneca with half-life extension and reduced Fc receptor binding.

The half-life extension approximately triples the durability of its action compared to conventional antibodies and could afford six to 12 months of protection from COVID-19 following a single administration. The reduced Fc receptor binding aims to minimise the risk of antibody-dependent enhancement of disease - a phenomenon in which virus-specific antibodies promote, rather than inhibit, infection and/or disease.

Myron J. Levin, Professor of Paediatrics and Medicine, University of Colorado School of Medicine, and principal investigator on the trial, said: “The results of STORM CHASER suggest that AZD7442 may be useful in preventing symptomatic COVID-19 in individuals not already infected.The PROVENT trial will give us more clarity in this patient population.

“While COVID-19 vaccination efforts have been successful, there is still a significant need for prevention and treatment options for certain populations, including those unable to be vaccinated or those who may have an inadequate response to vaccination.”

Kat Jenkins


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