アストラゼニカ社 新型コロナワクチンにより接種者の体内で作成されるスパイクたんぱく質の弊害を軽減する抗体カクテルEvusheldを開発か

 

AstraZeneca’s new Covid treatment: what is it and how does it work?

Evusheld could offer higher protection against variants and help vulnerable people ward off virus

Australia’s drugs regulator, the Therapeutic Goods Administration (TGA), has granted “provisional determination” to pharmaceutical company AstraZeneca for a long-acting antibody cocktail which has shown promise in preventing Covid-19 in adults.

Provisional determination is an early step in the drugs approval process and means AstraZeneca can now submit further data to the TGA from human trials about how the treatment works and its safety. Once the TGA has scrutinised the data, and if it is satisfied with it, it may grant Evusheld “provisional approval” for use in Australia in limited circumstances. Further data must be collected and given to the TGA even if this occurs.

What is the treatment?

This treatment consists of two laboratory-made antibodies, tixagevimab and cilgavimab. These antibodies bind to the spike protein of the virus, stopping the virus from entering the body’s cells and causing an infection.

Because each of the antibodies attach to different parts of the protein, using them in combination may be more effective than using either alone. It is also hoped this will offer good protection against variants, since the virus would have to mutate in multiple ways to escape both antibodies’ actions.

Evusheld is being considered for use as a Covid-19 preventive in Australians aged 18 years and older. In August, AstraZeneca released the results of a trial of the treatment involving 5,197 participants from the US, UK, Spain, France and Belgium who did not have Covid-19. Seventy-five per cent of participants had comorbidities, including medical conditions that often mean vaccination is weak or ineffective. Two-thirds of participants received Evusheld, and the rest were given a placebo.

The trial found Evusheld reduced the risk of developing symptomatic Covid-19 by 77% compared to the placebo. There were no cases of severe Covid-19 or related deaths in those given Evusheld. In the placebo group, there were three cases of severe Covid-19, which included two deaths.

The results now need to be replicated more widely in further trials, which is why regulators such as the TGA require AstraZeneca to submit ongoing data.

Is it a vaccine?

No. A vaccine trains the body’s immune system to respond to the virus if a person becomes infected in the future. Evusheld provides antibodies directly to the body via two intra-muscular injections administered consecutively. It immediately targets and neutralises the virus, preventing the virus from entering cells and causing an infection in the first place.

If approved, Evusheld will be the first long-acting antibody available for Covid-19 prevention in vulnerable populations who are unable to mount an adequate immune response to the virus from vaccination alone, for example people with cancer, and some elderly people.

Who will benefit from it?

Associate Prof Nada Hamad, a haematologist in Sydney, said Evusheld and similar treatments under development are designed to fill a gap left by vaccines, and by antibody treatments like Sotrovimab.

Sotrovimab is given to people already diagnosed with Covid-19 who are at high risk of developing severe disease. Sotrovimab needs to be administered early after someone is diagnosed to be effective.

“But Sotrovimab is very short-acting,” Hamad said. “It just lasts as we wait for the virus to dissipate. Once you get over the virus, the treatment doesn’t hang around in your body.

“Evusheld is a longer-acting antibody, and the hope is it will prevent the infection.”

Why not roll it out to the general population as well?

Clinical trials to date show Evusheld may provide six to 12 months of protection from the virus. This is significantly shorter than vaccines. Even though the protection offered by vaccines does slowly wane over time, they are still effective at preventing severe disease, death and hospitalisation months down the track.

“Evusheld and similar treatments being examined should be seen as a major advancement in protecting the very vulnerable, but not a vaccine alternative,” Hamad said.

Evusheld also takes longer to administer, is more expensive, needs to be given by a trained doctor or nurse, and patients may need longer monitoring afterwards than the 15 minutes required for a vaccine. It is not something that can be quickly given in a pharmacy or hub, so it is not ideal for widespread, fast rollout, Hamad said. Plus, further data from ongoing trials is still needed, while the efficacy and safety of the vaccines are now well known.

Evusheld has also shown promise in preventing severe disease when given early as a treatment to those infected with Covid-19, similar to Sotrovimab.

https://www.theguardian.com/australia-news/2021/nov/10/astrazenecas-new-covid-treatment-what-is-it-and-how-does-it-work

まあ更なる別の弊害がほぼ確実に発生するでしょうけどね。（爆ｗｗｗｗｗｗｗｗｗ