November 17, 2021: Detailed Description

Of A Highly Potent SARS - CoV - 2

Neutralizing Antibody: Bamlanivimab

Monoclonal antibodies have been shown to be effective in both the prevention and early treatment of SARS-CoV-2 infections. One of the antibodies currently approved for clinical use by emergency use authorization is a combination antibody treatment of bamlanivimab and etesevimab. A recent paper by Jones et al.describes bamlanivimab and its properties in detail, as well as details how bamlanivimab was discovered, providing a potential blueprint for antibody discovery in the future.

Monoclonal antibodies are typically laboratory-produced molecules that mimic the adaptive immune system’s response to invading pathogens. They neutralize a virus by blocking the Spike (S) protein from attaching to the host ACE2 receptor, which reduces viral reproduction and immune reactions.

SelectingBamlanivimab

To find potential SARS-CoV-2 antibodies, Jones et al. extracted peripheral blood mononuclear cells (PBMCs) from a convalescent patient 20 days after initial symptoms. They extracted and screened about 5.8 million PBMCs, which contained 2,238 single antibodysecreting cells. Using custom machine-learning-based sequencing, Jones et al.narrowed their search to 440 high-confidence heavy and light chain antibodies.

From these 440 candidates, Jones et al.selected antibodies capable of rapid cloning, recombinant expression, and were observed in high frequency, of which there were 175. They further selected for more specific requirements, including SARS-CoV-2 and SARSCoV-1 binding, binding to the S protein receptor-binding domain, and binding to certain receptor-binding domain mutations commonly found in SARS-CoV-2 variants, including V378F and V483A. This led to a lead panel of antibodies for further testing.

Jones et al. tested the neutralizing capacity of the panel antibodies against a SARS-CoV-2 pseudovirus and a live SARS-CoV-2 isolate. In both instances, one antibody, bamlanivimab, was by far the most potent neutralizing antibody, with a half-maximal concentration of about 0.05 micrograms per milliliter neutralizing at roughly 75%.

BamlanivimabBinding

Bamlanivimab had a 10-fold greater neutralization capacity than any other identified antibody candidate. This is despite binding in a similar place and pattern to two other tested antibodies: Ab128 and Ab133, which is notably a similar configuration to advanced antibody candidate etesevimab.

To investigate the increased neutralization, Jones et al. performed x-ray crystallography on bamlanivimab and found that in addition to binding the receptor-binding domain, it also was found to bind to an epitope overlapping ACE2 binding sites.

The researchers then conclude that this allows bamlanivimab to bind the receptor-binding domain in both the “up” and “down” configurations, whereas the other antibodies, including etesevimab, only bind in the “up” configuration.

BamlanivimabProtection

To test for protection by bamlanivimab against Covid-19 related symptoms, Jones et al. used nonhuman primates as a simulation of how the antibody may be accepted by the human immune system. Testing for RNA copies per milliliter in bronchoalveolar lavage fluid, lung tissue, nasal swabs, and throat swabs, the researchers noticed distinct drops in RNA content across the board within days of monoclonal antibody inoculation.

In other words, in all areas of the respiratory tract, the monoclonal antibody bamlanivimab reduces SARS-CoV-2 replication and viral load, which in theory results in weakening and waning of symptoms sooner in the infection cycle. This is great news for general and atrisk populations alike. If you were to come in contact with a known SARS-CoV-2 infection or were early on in the symptom onset, taking bamlanivimab could greatly reduce the risk for at-least respiratory-related illness.

While bamlanivimab on its own neutralized SARS-CoV-2 more effectively etesevimab in the Jones et al. study, further research indicated that together they neutralize live virus even more effectively.

The combination therapy, now produced by Eli Lilly, is now approved by the Food and Drug Administration via emergency use authorization for post-exposure prophylaxis and treatment. In addition to immediate treatment, the antibody can be used in immunocompetent infected patients up to five to seven days postinfection and it remains effective. Additionally, the antibody is successful in preventing infection and disease in those known to be exposed to SARS-CoV-2 infected hosts.

MonoclonalAntibodies:TheOnceandFutureCureforCovid-19

However, we note that as SARS-CoV-2 continues to evolve into new and more mutated variants, the virus can and will become more resistant to treatments like bamlanivimab + etesevimab. For example, a recent study of three SARS-CoV-2 variants all originating in Africa indicates some resistance already occurs. The Beta variant from South Africa is completely resistant to the combination cocktail. Additionally, the Eta variant from Nigeria and the A.30 variant from Tanzania are substantially resistant to the cocktail in comparison to the Triad variant which drove infections in the Summer of 2020. In other words, these variants already contain mutations that render major approved monoclonal antibodies less effective or completely ineffective.

Despite this, we implore more such wide studies to be undertaken as hidden gems like bamlanivimab await discovery. More treatments and prophylactics of this nature could greatly reduce the risk for hospitalization and death, especially among at-risk individuals. Using bamlanivimab’s discovery as a blueprint may lead to numerous more to be discovered in the critical months ahead.

This articleoriginallyappeared on Forbes, and can be read online here: Detailed Description Of A Highly Potent SARS-CoV-2

NeutralizingAntibody:Bamlanivimab

November 19, 2021:

Intramuscular Injection Of Monoclonal Antibodies Simplifies Covid Treatment

Until effective and accessible SARS-CoV-2 antivirals are available, monoclonal antibodies remain our strongest treatment and prophylactic against Covid-19. These antibodies are typically administered by a drip, which often requires medical assistance. One antibody, however, sotrovimab, could be administered intramuscularly (by shot), making delivery of the treatment far simpler. Here we review a press release by sotrovimab producers GSK and VIR that details the intramuscular administration of sotrovimab.

The trial to test sotrovimab was a phase 3, randomized, doubleblind, placebo-controlled study, which is the standard for an efficacy test of this nature. The aim of the trial was to determine whether intramuscular administration of the antibody was similarly effective to intravenous (IV) administration for the early treatment of mildto-moderate Covid-19 in high-risk populations.

Primary Outcomes

A detailed review of the study is yet to be released, but according to the GSK press release, the results for intravenous and intramuscular administration of sotrovimab were roughly equal. There was a 2.7% rate of progression to hospitalization for more than 24 hours or death among high-risk patients with mild-to-moderate Covid-19 in the intramuscular group. In contrast, that rate in the intravenous cohort was 1.3%.

The adjusted difference between the two administration methods was 1.07% with a 95% confidence interval of -1.25% to 3.39%, which falls below the upper bound set by the Food and Drug Administration for non-inferiority. In other words, the receiving sotromivab from a shot in the arm is of the same clinical effectiveness as from an IV drip.

SotrovimabStructure

We have previously described the origins and activities of sotrovimab in greater detail. To recount, the antibody is a derivative of another antibody, S309, which was first isolated from memory B cells from the sera of a recovered SARS-CoV-1 patient. S309, like many other antibodies, targets the Spike protein of the viral genome, which modulates viral entry into host cells and carries several antibody binding sites.

S309 targets a specific residue on the Spike protein, N343, which was later determined to be a consistently conserved glycan in the Sarbecovirus subgenus. As SARS-CoV-2 belongs to this subgenus and maintains many similarities to SARS-CoV-1, S309 was a promising neutralizing antibody candidate for inhibition of SARSCoV-2.

Sotrovimab differs from S309 in a particular way. It is purposefully engineered to possess two mutations in the Fc region. These are M428L and N434S, colloquially referred to as the LS mutation. These two mutations confer enhanced antibody binding to the Fc receptor, a critical binding agent for monoclonal neutralization. Studies describe that the two mutations result in an extended half- life of roughly 50 days and enhanced drug distribution to the respiratory system, protecting from significant lung damage or other Covid-related respiratory complications.

CaveatsandConclusions

While the finding that intramuscular and intravenous administration of sotrovimab is significant, there are several further endpoints that should be considered with this monoclonal antibody and with all antibody candidates.

The trial described follows patients through 29 days of trial. As the half-life of sotrovimab is detailed by some studies as roughly 50 days, it would be noteworthy to follow these patients past the 29-day marker to investigate the ongoing protection from SARS-CoV-2 reinfection that sotrovimab may grant.

While the two administration methods were statistically equivalent, more patients were hospitalized or died in the intramuscular cohort than the intravenous cohort. It would be interesting to analyze the health context and complications of those in the intramuscular group versus the intravenous group to potentially find some correlation in symptom protection.

It is worth commenting on the relative merits and disadvantages of a single intramuscular injection of long-acting monoclonal antibodies versus orally-administered pills both for the treatment and prevention of COVID-19.

The advantage of pill formulation is that they do not require medical personnel for administration. However, the patient must determine that they are infected, see a doctor, obtain a prescription, and take the pills as recommended, at present a five-day course involving a dose every 12 hours. Moreover, the treatment must begin shortly after infection and usually within three to four days of symptom onset, which translates to between six and 12 days postinfection. Additionally, once oral treatment ceases, the patient is only protected by existing convalescent antibodies.

A single muscular injection, however, requires no further treatment or medication past the moment of treatment, though this requires medical personnel for administration. Moreover, the half-life of sotrovimab is roughly 50 days, which means the protection from subsequent infections following exposure could last three months or longer. In the case of one antibody cocktail developed by Regeneron, protection is estimated to last eight months, though that treatment is an IV drip.

Perhaps the best use for antiviral drugs occurs prior to infection, either as pre-exposure or post-exposure prophylaxis. In other words, the drug is administered as a preventative either in general or immediately following exposure to a known positive infection. In this context, a single intramuscular injection of an antibody is far superior to orally-administered pills. The single intramuscular injection may provide protection for up to four months, whereas ingestible pills only protect as long as they are taken. Additionally, long-term use of antiviral pills could lead to dangerous side effects, including carcinogenesis. This is the case for aspiring drug candidate Molnupiravir, which is toxic and mutagenic in extended use.

One major advantage of small-molecule ingestible antivirals over intramuscular injections is the price. Prices may vary and both Merck and Pfizer have stated that costs will be lower in low-income countries. For Molnupiravir, the cost of production for a full course is roughly $5. Most small-molecule drugs will be of similar production cost: around $20 or less. In higher-income countries, the five-day regimen of antiviral pills is closer to $500. A full 8-milliliter dose of sotrovimab will cost roughly $2000, which is far from a competitive price point compared to other existing and emerging treatments for Covid-19. Were the sotrovimab treatment closer to the $500 to $1000 range, it may be more competitive in the treatment and prophylaxis market.

For congregate living centers, particularly eldercare facilities where the residents are at high risk due to age and comorbidities, we first recommend triple vaccination. Then, if a Covid-19 case is detected, we would recommend all residents and employees receive an intramuscular injection of monoclonal antibodies. We call this the “belt and suspenders” strategy, conferring two layers of significant protection to high-risk populations. This strategy is universally beneficial, as it boosts all recipients' antibody levels tremendously. Were “belt and suspenders” a routine procedure in every potential host, we would all be better protected if exposed to the virus.

Orally-administered pills, on the other hand, only provide additional protection so long as the treatment is ingested. We also note that antiviral pills are mostly used in the context of postexposure and post-symptom-onset patients. Their benefits for preexposure prophylaxis have yet to be significantly evaluated.

It is welcome news that a variety of approaches for both treatment and prevention of SARS-CoV-2 infectious disease are either here or will soon be available. It will be up to both governments and individuals to decide which treatment is appropriate in what setting to join vaccines in medical control of the COVID-19 pandemic.

MonoclonalAntibodies:TheOnceandFutureCureforCovid-19

This articleoriginallyappeared on Forbes, and can be read online here:IntramuscularInjectionOfMonoclonalAntibodiesSimplifies CovidTreatment

November 24, 2021: