Monoclonal antibodies may prevent severe COVID-19, but there’s a catch
Promising interim data from a unique Phase 3 trial testing the efficacy of a monoclonal antibody cocktail developed to prevent SARS-CoV-2 infection has been announced by pharmaceutical company Regeneron. The preliminary results suggest this novel treatment is 100 percent effective at preventing symptomatic infection, but despite these positive signs there are concerns the prohibitive cost of producing monoclonal antibody therapies will severely limit widespread use.
Last week pharma company Eli Lilly revealed its monoclonal antibody treatment for COVID-19 is 80 percent effective at preventing viral infection. Not to be outdone, Lilly’s major monoclonal antibody competitor Regeneron is now announcing early results from its ongoing Phase 3 clinical trial.
Monoclonal antibody treatments are a little different to vaccines. Instead of teaching a body how to produce antibodies against a virus, monoclonal antibodies are a single dose of lab-produced antibodies intended to either prevent infection or reduce the severity of a disease for a short period of time.
Regeneron’s therapy is called REGEN-COV and it comprises two different but complimentary types of lab-engineered antibodies developed to rapidly stop the virus from replicating inside an infected patient. These kinds of monoclonal antibody therapies are designed to be administered to subjects at high-risk of being infected with SARS-CoV-2, or given to patients at the very earliest stage of COVID-19.
Because monoclonal antibodies only offer limited short-term protection the trials testing them must be very focused. Eli Lilly’s bamlanivimab treatment, for example, is being trialled in nursing homes and aged care centers at the first sign of a localized outbreak. Regeneron on the other hand is looking at how well its antibody cocktail can prevent viral infection in subjects living in households with a confirmed COVID-19 case.
To qualify for the trial subjects must be recruited and dosed with the antibodies within four days of their household contact testing positive for SARS-CoV-2. Regeneron plans to recruit 2,450 subjects in this blinded, randomized and placebo-controlled Phase 3 trial.
Regeneron's interim data analysis comprises the first 409 subjects enrolled in the trial. The data has yet to be peer-reviewed or published in a journal but complete results for the entire trial are hoped to be delivered in the first half of 2021.
These early results reveal the antibody cocktail delivered 100 percent protection from symptomatic infection (8/223 placebo vs. 0/186 REGEN-COV). The trial is also testing for asymptomatic infections and found the treatment effective on that measure (23/223 asymptomatic infections in placebo group vs. 10/186 REGEN-COV).
The interim data also shows those in the REGEN-COV group who did still get infected with SARS-CoV-2 displayed decreased peak viral levels and significantly shorter durations of viral shedding. In other words, those asymptomatic cases in the antibody group were potentially much less contagious than similar cases in the placebo group.
"These data using REGEN-COV as a passive vaccine suggest that it may both reduce transmission of the virus as well as reduce viral and disease burden in those who still get infected," says Regeneron’s chief scientific officer, George D. Yancopoulos.
Perhaps the most significant aspect of this new announcement from Regeneron is the way the therapy was administered. Traditionally monoclonal antibodies must be administered by intravenous infusion. Eli Lilly’s competing therapy requires a 60 minute infusion which severely limits how broadly these treatments can be deployed.
This new REGEN-COV trial, however, tested the efficacy of administration by subcutaneous injection. This essentially turns an onerous, medically supervised 60 minute infusion into a swift single injection that can be delivered virtually anywhere. Considering this kind of monoclonal antibody treatment may be most effective as a very early preventative measure in communities at high-risk of infection, delivery by injection is nothing short of a game-changer.
"In this prevention trial, REGEN-COV was given as injections rather than an infusion, which makes administration much more convenient and efficient for patients and overburdened healthcare providers and facilities," says David Weinreich, Regeneron’s Head of Global Clinical Development.
Penny Ward, from King’s College London, suggests this preliminary data is interesting and awaits the full panel of data from the trial. Taken on its own merits, Ward says this monoclonal antibody therapy is “a potentially exciting addition to the therapeutic armamentarium,” offering clinicians an important tool to intervene and suppress outbreaks in places such as universities, prisons and hospitals.
“Vaccination will prevent disease but takes 14-21 days to take effect: in an immediate contact situation, this is too long to prevent illness which may, in an individual at high risk, be fatal,” says Ward. “This approach could protect patients receiving chemotherapy for cancer, enable control/prevention of outbreaks in an institutional setting and reduce pressure on health services.”
The massive issue that will ultimately hold these monoclonal antibody therapies back from widespread use is sadly their prohibitive cost. It's speculated both Regeneron and Eli Lilly’s antibody therapies could cost over US$1,000 per dose.
As explained by Arturo Casadevall, from Johns Hopkins School of Medicine, the excessive cost of monoclonal antibody therapy is less about greedy pharmaceutical companies and more to do with time-consuming and labor-intensive modes of production.
“The reason that monoclonal antibodies are so expensive is because they have to be made in what we call tissue culture,” said Casadevall in an interview last November. “You have to grow the cells. And these cells have to produce the protein which then needs to be purified. It’s not only labor-intensive, [but] the reagents are very expensive. In general, monoclonal antibody therapies— whether for COVID, cancer, or for rheumatological problems—tend to be expensive.”
Stephen Evans, from the London School of Hygiene and Tropical Medicine, suggests monoclonal antibodies such as those developed by Regeneron may be too expensive to deploy widely but that does not mean they won’t be a useful tool.
“As a prevention of Covid disease it would probably be too expensive for very widespread use (we are not informed of its cost), but it could be very useful in situations where people are at very high risk of exposure to the virus and their own immune system is deficient in its response to any standard Covid vaccine,” says Evans.
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