SINGAPORE - Supplies of AstraZeneca's antibody drug for the treatment of Covid-19 are expected to arrive by the end of the year, after Singapore signed a new purchase agreement with the drugmaker.

Known as Evusheld, the drug cocktail is a combination of two "long" antibodies - which take longer to metabolise in the body and can provide longer-lasting protection for up to a year, compared with monoclonal antibodies.

Monoclonal antibodies are lab-manufactured proteins that act like antibodies to help the immune system fight the virus.

AstraZeneca said phase three clinical trials showed that the drug is able to reduce the risk of severe Covid-19 or death by 88 per cent when given to patients with mild to moderate Covid-19 within three days of the onset of symptoms.

Preliminary findings in the lab have also shown the drug's effectiveness against variants of concern, including the Delta variant.

The company said that currently available pre-clinical data also suggests the drug's effectiveness should not be "significantly impacted" by the new Omicron variant.

The Health Sciences Authority said in response to queries from The Straits Times that it is in discussions with AstraZeneca to facilitate the regulatory submissions for approval. However, no application has been filed yet.

The two antibodies in the drug are derived from antibody-producing B-cells that were donated by recovering Covid-19 patients.

Both antibodies have been modified to provide long-lasting protection of up to a year in those who receive the drug as treatment.

Mr Vinod Narayanan, the country president of AstraZeneca Singapore, said: "Evusheld provides healthcare professionals and patients in Singapore with a new option to fight the virus. Additionally, Evusheld will provide another prevention option for high-risk populations, alongside vaccines, including for people who are immuno-compromised and unable to develop the needed degree of protective response following Covid-19 vaccination."

AstraZeneca this week received emergency use authorisation for Evusheld from the United States' Food and Drug Administration (FDA) for the prevention of Covid-19, and has filed for regulatory approvals in other countries.

The FDA said the drug is authorised for use in preventing Covid-19 in people who have weakened immune systems and who may not be adequately protected by vaccines.

The Straits Times understands that Evusheld will be used only for the treatment of Covid-19 in Singapore, and not prevention.