FDA authorises Regeneron's dual COVID-19 antibody treatment for emergency use

The FDA has issued an emergency-use authorisation (EUA) to Regeneron's filing for casirivimab and imdevimab to be administered together to treat mild-to-moderate COVID-19 in adults and paediatric patients. The monoclonal antibodies, also referred to as REGN-COV2 or as REGEN-COV2 when used in combination, are directed against the spike protein of SARS-CoV-2.

The dual antibody treatment is specifically indicated for patients 12 years of age or older weighing at least 40 kg with positive results of direct SARS-CoV-2 viral testing and who are at high risk for progressing to severe COVID-19. It is also the second antibody therapy to receive an EUA by the US regulator after one issued to Eli Lilly's investigational neutralising antibody bamlanivimab earlier this month for recently diagnosed, mild-to-moderate COVID-19 in patients 12 years and older who are at high risk for progressing to severe COVID-19 and/or hospitalisation.

Reduced hospitalisations, ER visits

Under the EUA, Regeneron said the recommended dose is for 1200 mg of casirivimab and 1200 mg of imdevimab, for a 2400-mg dose total, administered as a single intravenous infusion. The authorisation is based on Phase II data from the first 799 adults in an ongoing randomised trial of non-hospitalised patients with COVID-19. Results reported in October showed significant reductions in virus levels within seven days of outpatients receiving the antibody cocktail.

However, the FDA said the "most important evidence" that the dual antibody therapy may be effective came from the secondary goal of medically attended visits related to COVID-19, particularly hospitalisations and emergency room visits within 28 days after treatment. For patients at high risk for disease progression, results showed that hospitalisations and emergency room visits occurred in 3% of patients treated with casirivimab and imdevimab together, compared to 9% for placebo.

Need for COVID-19 treatments

George Yancopoulos, chief scientific officer at Regeneron, said "we are encouraged that no variants resistant to the cocktail were identified in the clinical trial analyses to date, which is consistent with our preclinical findings." He also suggested that despite recent positive study results for COVID-19 vaccines, "there remains a need to treat patients who develop COVID-19, especially as some may not have had access to or were not protected by vaccination."

As was the case with bamlanivimab, the FDA said casirivimab and imdevimab are not authorised for patients who are hospitalised due to COVID-19 or require oxygen therapy as a result of the infection, as monoclonal antibodies such as these may be associated with worse clinical outcomes in COVID-19 patients requiring high-flow oxygen or mechanical ventilation. Regeneron recently paused enrolling hospitalised COVID-19 patients with high oxygen needs in its REGN-COV2 trials, citing "a potential safety signal and an unfavourable risk/benefit profile at this time." For related analysis, see ViewPoints: Regeneron's mAb wobbles highlight importance of bispecifics.

Regeneron also indicated that it now expects to have REGN-COV2 treatment doses ready for about 80,000 patients by the end of November, 200,000 patients by the first week of January, and 300,000 patients in total by the end of January 2021. Earlier this year, Regeneron signed a $450-million supply agreement with the US, with the government there committing to provide up to 300,000 doses of the therapy at no cost to patients.

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