AstraZeneca’s one-time dual-antibody injection cut the risk of symptomatic COVID-19 by up to 83 percent and the risk of severe disease by 88 percent in two studies of high-risk patients.

The positive results from the two phase 3 trials show that the injection can be used both prophylactically and therapeutically, the company said.

The ongoing PROVENT trial enrolled 5,197 subjects, 75 percent of whom had at least one medical comorbidity that increased their risk of severe COVID-19. About 43 percent were 60 years or older. Participants were randomized to placebo or to a single intramuscular injection of 300 mg of AZD7442.

At a median of six months’ follow-up, those who received the vaccine were 83 percent less likely to develop symptomatic COVID-19. None of these subjects developed severe COVID-19 or died from the disease. In the placebo arm, there have been five severe COVID-19 cases and two deaths.

The separate TACKLE study enrolled 903 nonhospitalized patients being treated for mild-to-moderate COVID-19 infections. They were randomized to placebo or to a single 600-mg injection of AZD7442, given within the first three days of confirmed infection.

The primary efficacy endpoint was the composite of either severe COVID-19 or death from any cause through day 29. Subjects will continue to be followed for 15 months. About 13 percent were 65 year or older; 90 percent had medical comorbidities that increased their risk of severe disease (cancer, diabetes, obesity, chronic lung disease or asthma, cardiovascular disease or immunosuppression).

In an exploratory analysis, the injection reduced the risk of severe COVID-19 by 88 percent.

AZD7442 was well-tolerated in both trials.

“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 return to their everyday lives,” said study investigator Hugh Montgomery of the University College, London. “Importantly, six months of protection was maintained despite the surge of the Delta variant among these high-risk participants who may not respond adequately to vaccination.”

Full results of both studies will be presented at an upcoming meeting. AstraZeneca is seeking FDA Emergency Use Authorization (EUA) for AZD7442 as a COVID-19 preventive in high-risk populations. The company has committed to supplying 700,000 doses to the federal government if it receives the EUA (DID, Oct. 7).

AZD7442 combines two long-acting monoclonal antibodies (tixagevimab and cilgavimab), both of which were derived from B-cells extracted from COVID-19 convalescent serum. Both antibodies attach to the SARS-CoV-2 spike protein and provide a high level of neutralizing antibodies for up to a year.

AZD7442 also being studied as a potential treatment for hospitalized COVID-19 patients as part of the National Institute of Health’s ACTIV-3 trial. — Michele G. Sullivan