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Preventing severe disease in Covid-19 patients

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Written by Raquel Barroso Ferro, University of Aberdeen

In April 2020, Vir Biotechnology and GlaxoSmithKline (GSK) began a partnership that has proven fruitful. As announced on March 10, 2021, patients with mild or moderate Covid-19 at high risk of progression to severe disease who were treated with the human monoclonal antibody VIR-7831 (sotrovimab) in the COMET-ICE study (NCT04545060) had a reduction of 85% in hospitalization or death compared to those who received placebo. Although complete details of the ongoing trial are not yet available, this “artificial immunity” offers hope for patients. In particular, such treatment may be beneficial to those who are unable to receive a vaccine or whose immune system is weakened.

Vir and GSK plan to submit an emergency use authorization application in the US and seek authorizations in other countries.

Originally derived from a patient who survived severe acute respiratory syndrome coronavirus (SARS-CoV) in 2003, (1) the antibody binds to a highly conserved epitope on the spike glycoprotein shared by both SARS-CoV and the virus causing the current pandemic, SARS-CoV-2. This shared epitope suggests high conservation and its likely importance for viral infection. Binding this epitope may reduce the likelihood of mutational escape, and allow the antibody to neutralize multiple variants that emerge. In fact, according to a pre-print posted March 10, 2021 on BioRxiv, the epitope of VIR-7831 does not overlap with the mutational sites observed in the circulating variants. (1)

In preclinical studies, VIR-7831 achieved high concentration in the lungs, (1) the principal site of Covid-19 infection, (2) neutralized live virus, and was shown to engage effector functions, such as antibody-dependent cytotoxicity and phagocytosis, to mediate clearance of infected cells. (1)

The announcement of positive results from the COMET-ICE study follows a March 3, 2021, announcement by Vir and GSK that the Data and Safety Monitoring Board for the ACTIV-3 trial (NCT04501978) evaluating VIR-7831 in hospitalized adults with COVID-19 has recommended that the VIR-7831 arm of the trial be closed to enrolment while the data mature. No safety signals were reported, but the sensitivity analysis called into question the magnitude of the potential benefit of VIR-7831 administration to hospitalized patients. The National Institutes of Health is sponsoring the ACTIV-3 master protocol, which is examining the clinical safety and efficacy of numerous investigational agents relative to current standard of care therapy in hospitalized patients with more severe COVID-19.

Overall, the findings from the two clinical studies suggest that VIR-7831 could be of most benefit to patients during early onset of the disease, shortly after a positive test. This treatment has great potential to reduce both the severity of the disease in individuals and the substantial burden COVID-19 has placed on hospital staff and resources.

Another challenge, however, will be instilling confidence in doctors to prescribe anti-SARS-CoV-2 monoclonal therapies to patients. According to Dr. Derek Angus, an intensive-care physician at the University of Pittsburgh who spoke to Nature, (3) the absence of data published in peer-reviewed journals has left doctors wary. Moreover, high costs and more specialized requirements for administering infusion-based therapies will make what seems to be a working therapy and hope for patients a more complicated task. Intramuscular (IM) injection, which may substantially increase patient convenience, is possible. Clinical studies for anti-SARS-CoV-2 antibodies administered via intramuscular (IM) injection, including VIR-7831 (COMET-PEAK) and AZD7442 (PROVENT, STORM CHASER), are ongoing and clinical study results have not yet been announced.

1.       Cathcart et al. The dual function monoclonal antibodies VIR-7831 and VIR-7832 demonstrate potent in vitro and in vivo activity against SARS-CoV-2. 2021. 
2.       Cevik et al. Virology, transmission, and pathogenesis of SARS-CoV-2. BMJ 2020; 371. BMJ. 2020. 
3.       Ledford H. COVID antibody treatments show promise for preventing severe disease. Nature 2021. 

FDA issues Emergency Use Authorization for bamlanivimab/etesevimab combination

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On February 9, 2021, the U.S. Food and Drug Administration issued an emergency use authorization (EUA) for bamlanivimab and etesevimab administered together for the treatment of mild to moderate COVID-19 in adults and pediatric who test positive for SARS-CoV-2 and who are at high risk for progressing to severe COVID-19. Developed by Eli Lilly and Company, bamlanivimab and etesevimab are monoclonal antibodies (mAbs) that target overlapping regions of the SARS-CoV-2 spike protein.

The EUA was based on a randomized, double-blind, placebo-controlled clinical trial in 1,035 non-hospitalized adults with mild to moderate COVID-19 symptoms who were at high risk for progressing to severe COVID-19. Of these patients, 518 received a single infusion of bamlanivimab (2.8 g) and etesevimab (2.8 g) together, and 517 received placebo. The primary endpoint was COVID-19 related hospitalizations or death by any cause during 29 days of follow-up.  Hospitalization or death occurred in 11 (2%) patients treated the mAb combination vs. 36 (7%) patients who received placebo. All 10 deaths (2%) occurred in the placebo group.

The authorized dosage of 700 milligrams bamlanivimab and 1400 milligrams etesevimab administered together is based on analyses of available preclinical, clinical, and virologic data, as well as pharmacokinetic and pharmacodynamic modeling, which, in totality, support that the authorized dosage is expected to have a similar clinical and virologic effect to the dose evaluated in the clinical trial. Use of the mAb combination is not authorized for patients who are hospitalized due to COVID-19 or require oxygen therapy due to COVID-19.

In November 2020, FDA issued an EUA for a single infusion of 700 mg bamlanivimab for the treatment of mild-to-moderate COVID-19 in adult and certain pediatric patients. Since the monotherapy and the combination treatment are expected to benefit patients at high risk of disease progression, both 700 milligrams bamlanivimab alone and the combination of 700 milligrams bamlanivimab and 1,400 milligrams etesevimab administered together will be available under an EUA.

Anti-SARS-CoV-2 casirivimab and imdevimab (REGN-COV2) authorized in the US for COVID-19

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On November 20, 2020, the US Food and Drug Administration authorized the emergency use of casirivimab and imdevimab (REGN-COV2), both of which are recombinant human IgG1 monoclonal antibodies that target the receptor binding domain of the spike protein of SARS-CoV-2. This antibody cocktail has been shown to reduce COVID-19-related hospitalization or emergency room visits in patients at high risk for disease progression within 28 days after treatment when compared to placebo.

After reviewing the analysis of Phase 1 and 2 data from the ongoing Phase 1/2/3 NCT04425629 study, the agency concluded that “it is reasonable to believe that casirivimab and imdevimab, administered together, may be effective for the treatment of mild to moderate COVID-19 in adults and pediatric patients (12 years of age and 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 and/or hospitalization, and that, when used under the conditions described in this authorization, the known and potential benefits of casirivimab and imdevimab, administered together, outweigh the known and potential risks of such product.”

The EUA letter further states that distribution of REGN-COV2 will be directed by the U.S. government, and its EUA will be effective until the declaration that circumstances exist justifying the authorization of the emergency use of drugs and biological products during the COVID-19 pandemic is terminated or the EUA is revoked. The authorized dosage is 1,200 mg of casirivimab and 1,200 mg of imdevimab administered together as a single intravenous (IV) infusion over at least 60 minutes via pump or gravity as soon as possible after positive viral test for SARS-CoV-2 and within 10 days of symptom onset.

Regeneron was granted a $450 million contract to manufacture and supply REGN-COV2 by the US government, which has committed to making the doses available to Americans for free. The agreement covers a fixed number of bulk lots, as well as fill/finish and storage activities. Delivery of REGN-COV2 drug product started during the third quarter of 2020, and the company expects to have ~ 80,000 doses available by the end of November, ~200,000 total doses ready by the first week of January 2021, and ~ 300,000 total doses ready by the end of January 2021.

Emergency use authorization requests for anti-SARS-CoV-2 antibodies under FDA review

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On October 7, 2020, Eli Lilly and Company and Regeneron announced that they have submitted requests to the  U.S. Food and Drug Administration (FDA) for emergency use authorizations (EUA) of their anti-SARS-CoV-2 monoclonal antibodies.

Lilly’s EUA request is for bamlanivimab (LY-CoV555) monotherapy in higher-risk patients who have been recently diagnosed with mild-to-moderate COVID-19. According to the company, up to 100,000 doses of 700 mg LY-CoV555 monotherapy may be available in October, and one million doses available in Q4 2020.

The combination of LY-CoV555 and LY-CoV016, which bind complementary regions of the SARS-CoV-2 spike protein, for the treatment of symptomatic COVID-19 in an outpatient setting is also being evaluated. Lilly anticipates submission of an EUA request for combination therapy in November, and may have data to support a biologics license application submission for combination therapy as early as Q2 2021.

Regeneron’s EUA request is for REGN-COV2, which is a combination of two anti-SARS-CoV-2 monoclonal antibodies (REGN10933 and REGN10987). Regeneron was granted a $450 million contract to manufacture and supply REGN-COV2 by the US government, which has committed to making the doses available to Americans for free. The agreement covers a fixed number of bulk lots that are intended to be completed in the fall of 2020, as well as fill/finish and storage activities. At the time of the EUA request, Regeneron had doses available for ~ 50,000 patients, and expects to have doses available for a total of 300,000 patients within several months.

The Antibody Society is tracking the progress of recombinant biologic COVID-19 interventions in preclinical and clinical studies. Summary data for all anti-SARS-CoV-2 antibodies in clinical studies can be found here.

Antibodies to Watch in a Pandemic

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The extraordinary scale of the COVID-19 pandemic has elicited extraordinary responses world-wide, but the resulting disruptions have raised concerns about delays in approval of non-COVID-19 antibody therapeutics.

As part of the virtual Antibody Engineering & Therapeutics Europe conference, Dr. Janice Reichert, Executive Director of The Antibody Society,  provided an update on non-COVID-19 antibody therapeutics approved so far in 2020, and those that might be approved by the end of the year. She also discussed the biologics currently in development for COVID-19, which includes over 50 repurposed biologics and over 80 anti-SARS-CoV-2 biologics.

Broadcast date: Thursday August 27, 2020.

Updated presentation slides can be downloaded here.

Dataset of commercially sponsored biologic COVID-19 interventions can be downloaded here.