AstraZeneca's COVID-19 prevention therapy reduced the risk of infection in patients with weaker immunity in a late-stage trial, meeting its primary goal, the drugmaker said on Thursday.

The long-acting antibody therapy called sipavibart showed a "statistically significant reduction" in symptomatic COVID-19 cases among immunocompromised patients, the company said.

Immunocompromised people include those with blood cancer, organ transplant recipients, patients with end-stage renal disease requiring dialysis, patients receiving B-cell depleting therapy within the past year, and those taking immunosuppressive medications, it said.

These patients make up about 25% of COVID-19 hospitalizations, intensive care unit (ICU) admissions, and deaths, even after multiple doses of COVID-19 vaccines, according to the Anglo-Swedish drugmaker.

AstraZeneca acquired sipavibart from RQ Bio in May 2022.

"Immunocompromised patients currently have limited or no options for COVID-19 protection and continue to face a significant burden of disease, despite often being fully vaccinated," said Iskra Reic, the company's Executive Vice President for Vaccines and Immune Therapies.

."..we will now work with regulatory authorities globally to bring sipavibart to these vulnerable patients."

The results come a week after the company withdrew its COVID-19 vaccine, one of the first and most widely used, citing a "surplus of available updated vaccines" since the pandemic.

That move also followed intense scrutiny in recent months over a rare side effect causing blood clots and low blood platelet counts. AstraZeneca is being sued in London by more than 50 alleged victims and grieving relatives. It declines to comment on active legal cases, but says patient safety is its top priority and regulators have stringent standards.