A new treatment could soon help protect people from developing severe COVID. AstraZeneca has just released results from a phase 3 clinical trial the final stage of testing before a drug is authorized that suggests its new COVID treatment, AZD7442 is effective at reducing severe disease or death in non-hospitalized COVID patients.
The treatment contains antibodies, which are usually produced naturally in response to a COVID infection or vaccination. They work by recognizing specific parts of SARS-CoV-2 the virus that causes COVID and either attack these directly or bind to them to stop the virus from working and flag it for destruction by other parts of theimmune system.
After they've done their job of clearing the virus, the antibodies remain in the body for a period of time, making up part of our immunological memory. If what they target is encountered again, they can leap into action.
The new treatment, AZD7442, uses special antibodies called monoclonal antibodies. These are antibodies produced in a lab that imitate the body's natural defenses, in this case mimicking the immune system's response to COVID.
Artificially developing antibodies to fight disease isn't a new technique. This technology is already used to treat many diseases, including leukemia,breast cancer and lupus. In fact, this isn't even the first time the technique has been used for COVID. The first COVID monoclonal antibody treatment was approved in the UK in August 2021.
How does AstraZeneca's treatment work?
AZD7442 is a cocktail of two monoclonal antibodies tixagevimab and cilgavimab that are designed to reduce the severity of a SARS-CoV-2 infection and so prevent people from getting severely ill.
Both of these antibodies bind to different parts of the virus's spike proteins, which cover its outer surface and are what the virus uses to infect cells. It's thought that attaching to these proteins is what gives the medicine its effect, as this stops the virus from being able to get inside cells and reproduce.
The two monoclonal antibodies in the cocktail are based on antibodies taken from patients who survived COVID. Scientists at AstraZeneca took blood samples from patients and isolated immune cells called B cells, which are the antibody factories of the human body. They then grew more of these B cells in the lab and used them to make large quantities of the two antibodies, which they had identified as specifically targeting the coronavirus's spike protein.
But the key difference between this and other antibody-based treatments is that in AZD7442, the antibodies have been modified so they stay in the body for longer.
Studies using similarly modified antibodies against another respiratory virus respiratory syncytial virus have shown that this approach gives long-term protection, with the modified antibodies having triple the durability of conventional antibodies. It's hoped that a single dose of AZD7442 could offer 12 to 18 months of protection from severe COVID, though we'll have to wait to see exactly how long protection lasts.
How well does it work?
AstraZeneca's phase 3 trial investigated the effectiveness of the treatment when given to patients who were infected with SARS-CoV-2.