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The results showed that patients who received a single injection of the antibody treatment, known as AZD7442, were 83% less likely to develop symptomatic cases of the coronavirus than participants who received a placebo.
An earlier analysis of the trial, conducted three months after administration of the treatment, had shown that the risk of developing serious disease was reduced by 77%.
Six months after the administration of the treatment, no serious cases of Covid-19 or deaths from the virus had been recorded in the patients who received the cocktail of antibodies. In a group that received the placebo, five participants contracted severe Covid-19 within six months of starting the trial, and there were two Covid-related deaths.
Over 75% of the trial participants had underlying conditions that put them at high risk of contracting severe Covid-19, including those with compromised immune systems and therefore may have a reduced response to vaccination .
The phase three clinical trial was conducted at 87 sites in five countries: the United States, United Kingdom, Spain, Belgium and France. A total of 5,197 people participated, of which 3,460 received 300 mg of AZD7442 and 1,737 a saline placebo.
The six-month assessment included data from 4,991 of the participants, with those who opted out of the trial to be vaccinated being excluded from the data analysis. Subjects will continue to be evaluated for 15 months.
Half of the 903 participants in this trial received 600 mg of AZD7442, while the other half received a placebo.
Ninety percent of people included in the second study were considered to be at high risk of developing severe Covid-19 if they contracted the virus.
The full results of the trial have not yet been peer reviewed, but are expected to be submitted for publication in a peer-reviewed medical journal.
AstraZeneca said both tests showed AZD7442 was “generally well tolerated”.
“These compelling results give me confidence that this long-acting antibody combination can provide my vulnerable patients with the long-lasting protection they urgently need to finally get back to their daily lives,” Hugh Montgomery, Professor of Medicine at intensive care at University College London and lead investigator in the trials, said in a press release Thursday.
Meanwhile, Mene Pangalos, executive vice president of biopharmaceutical research and development at AstraZeneca, said AZD7442 was the only long-acting antibody that had phase three data to demonstrate its efficacy at both in the prevention and treatment of Covid-19 with a single dose.
“We are making progress on regulatory files around the world and look forward to delivering an important new option against SARS-CoV-2 as soon as possible,” he said.
Other companies developing antibody treatments include GSK, Regeneron, and Eli Lilly. All three have received emergency use clearance from the FDA.
In October, AstraZeneca announced that it had applied to the FDA for emergency use authorization for AZD7442 as a preventative treatment. It has not yet been granted.
The pharmaceutical giant has agreed to provide the US government with 700,000 doses of its antibody treatment if this request is accepted. It has also made agreements to supply AZD7442 to other countries.