Regeneron Pharmaceuticals said today its double-antibody cocktail against COVID-19 is advancing into Phase III studies, less than a month after the start of its first clinical trial, with preliminary data from one study expected to be reported later this summer.

Regeneron said it is proceeding with clinical development of the antibody cocktail after generating a positive review from the Independent Data Monitoring Committee overseeing the Phase I safety study, following an evaluation of data from an initial cohort of 30 hospitalized and non-hospitalized patients with COVID-19. Regeneron launched the safety study in June.

The cocktail, REGN-COV2, consists of two antibodies—REGN10933 and REGN10987—that are designed to bind non-competitively to the receptor binding domain of SARS-CoV-2’s spike protein. Regeneron says that such binding diminishes the ability of mutant viruses to escape treatment.

REGN-COV2 is among 18 “front runner” candidates among the more than 260 COVID-19 therapeutics tracked by GEN’s updated “COVID-19 DRUG & VACCINE TRACKER.”

Regeneron is partnering with the NIH’s National Institute of Allergy and Infectious Diseases (NIAID) to conduct what is being planned as a 2,000-patient Phase III trial (NCT04452318) designed to assess REGN-COV2’s ability to prevent infection among uninfected people who have had close exposure to a COVID-19 patient, such as a patient’s housemate.

The placebo-controlled trial, to be conducted at approximately 100 sites, had yet to begin recruiting patients as of June 30, the date of the study’s most recent update on ClinicalTrials.gov. According to that update, the trial’s estimated primary completion date is April 11, 2021, though Regeneron did not include a timeframe for reporting data from the NIAID study in its announcement today.

The trial will have three primary outcome measures:

  • Proportion of participants who have a positive SARS-CoV-2 quantitative reverse transcription polymerase chain reaction (RT-qPCR) based on central lab test and signs and symptoms of SARS-CoV-2 infection during an up to 1 month timeframe.
  • Proportion of participants who have a RT-qPCR confirmed SARS-CoV-2 infection (either symptomatic or asymptomatic) during the same efficacy assessment period.
  • Incidence and severity of treatment-emergent adverse events up to 8 months following treatment.

“Sooner than a vaccine”

“We are pleased to collaborate with NIAID to study REGN-COV2 in our quest to further prevent the spread of the virus with an antiviral antibody cocktail that could be available much sooner than a vaccine,” George D. Yancopoulos, MD, PhD, Regeneron co-founder, president, and chief scientific officer, said in a statement.

Regeneron has previously said that its antibody cocktail offers several advantages over a vaccine—including longer-term utility for elderly and immuno-compromised patients, who often do not respond well to vaccines.

In its statement today, Regeneron said it has advanced REGN-COV2 into the Phase II/III portion of two adaptive Phase I/II/III trials designed to evaluate the antibody cocktail’s ability to treat hospitalized and non-hospitalized patients with COVID-19.

One Phase II/III study (NCT04426695) is designed to assess the safety, tolerability, and efficacy of Regeneron’s antibody cocktail in hospitalized adult patients with COVID-19, with an estimated enrollment of 1,860 participants. The other study (NCT04425629) will evaluate the safety, tolerability, and efficacy of Regeneron’s antibody cocktail in ambulatory adult patients with COVID-19, with an estimated enrollment of 1,054 participants.

Regeneron said preliminary data from the Phase II/III trials is expected as soon as “later this summer,” though the study in ambulatory adults has an estimated primary completion date of November 21, and the study in hospitalized adults, March 3, 2021.

The two Phase II/III trials are set to be conducted at approximately 150 sites in the U.S., Brazil, Mexico and Chile.

The trials will evaluate primary endpoints that include the proportion of patients with treatment-emergent serious adverse events through day 169, the proportion of patients with infusion-related reactions through day 4, and the proportion of patients with hypersensitivity reactions through day 29.

Also listed as primary endpoints: Time-weighted average change from baseline viral shedding measured in swab samples through day 22, time-weighted average change from baseline viral shedding measured in saliva samples through day 22, and the proportion of patients with at least 1-point improvement in clinical status on a 7-Point ordinal scale.

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