As of the beginning of June 2020, we are still in the early stages of the COVID-19 global pandemic. Many questions remain unanswered as to whether an effective vaccine can be produced, and if so, when it might be available. In the meantime, significant activity centers on developing therapies to treat those who experience serious symptoms after infection by the virus. Anti-viral drugs such as remdesivir, originally developed to treat the Ebola virus, have attracted considerable attention. Another emphasis has been on drugs to block the often lethal “cytokine storm,” an intense immune reaction that can occur in the most acute cases of the disease. But there is perhaps more promise in using the same naturally occurring reagents that would be the basis of any immunity derived from vaccines, i.e., human antibodies. Anti-CoV-2 antibodies will block propagation of the virus and decrease worsening of symptoms in an individual.

ANTIBODY ACTION

Several types of antibodies are generated by B cells of the human adaptive immune system (as distinguished from the innate immune system) in response to foreign antigen encountered in the lymph nodes. Some antibodies bind and coat antigens to attract phagocytes that will engulf and destroy the invaders. Others combine with the antigens in a way that activates the complement cascade (a component of the innate immune system) that will then work together with those antibodies to eliminate the intruders. There is also a class known as neutralizing antibodies that can block viruses from entering cells. This last variety of antibodies is the focus of much current biopharmaceutical research in developing anti-COVID-19 therapies.

Standard biotech industry techniques for identifying neutralizing antibodies involve use of cell-based assays. Careful selection of an appropriate cell line and endpoint readout is crucial to achieving optimal results with these complex tests.  With MarinBio’s scientific expertise in designing and performing cell based assays and ELISA assays, we can help you test your candidate antibodies for blocking spike protein binding to ACE receptor. One ELISA assay design would use purified proteins, and one cell based assay method would use a cell with surface ACE receptor expression.

NEUTRALIZING ANTIBODIES

One source of neutralizing antibodies is blood plasma from people who have recovered from COVID-19 infection and generated their own antibodies against the virus in the process. Plasma is a clear fluid derived from blood that carries various blood cells, platelets, and antibodies along with other proteins. “Convalescent” plasma transfusions have been used for over 100 years as a medical treatment for various diseases. While convalescent plasma does contain neutralizing antibodies, and doctors in some hospitals are using it to treat COVID-19 patients who are seriously ill, there are known risks to plasma transfusion and supply issues that make convalescent plasma problematic for treating patients in a global pandemic. A potentially more important use of convalescent plasma is providing a source of neutralizing antibodies for researchers to study and select from for cloning and potential engineering as monoclonal antibodies (MAbs). Candidate MAbs would then be subjected first to testing in cell-based assays in vitro, then in non-human animals in vivo, and finally in clinical trials to prove their safety and efficacy in humans. These sophisticated biological drugs can be reliably mass produced, so if any successfully make it through clinical trials and gain approval by regulatory agencies such as the FDA or EMA, they can be manufactured at scale and distributed worldwide.

Antibodies against administered drugs may produce adverse reactions. These anti-drug antibodies can arise with the use of biologics, i.e., therapeutic protein drugs such as MAbs. MarinBio has considerable experience and expertise in designing anti-drug antibody assays (ADAs) to enable stringent screening for such antibodies by use of highly sensitive immunoassays in the ELISA format.

PHARMACEUTICAL COMPANY RACE TO FIND ANTIBODIES

A number of large biopharma companies are engaged in finding antibodies effective in neutralizing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the official name of the virus responsible for COVID-19. Activity is often centered on antibodies that would recognize the coronavirus’ “spike protein,” a part of the virus’ protective envelope that it uses to enter human cells after binding to a particular cell surface molecule, angiotensin-converting enzyme-2 (ACE-2). The structure of the spike protein allows it to mimic ACE-2’s endogenous ligand (angiotensin II), so the idea is that antibodies binding to different epitopes on the spike protein could change its structure or could just block the binding sites and prevent entry of the virus. If the virus cannot bind to and enter the cell, it will not be able to replicate, and the infection is halted.

Among the early players in the race to develop neutralizing antibodies are some of the largest biopharma companies in the world, with more likely to follow suit. Eli Lilly (Indianapolis, IN) teamed up with MAb developer AbCellera (Vancouver, BC) in March, then struck a deal with Junshi Biosciences (Shanghai, China) for co-development of MAbs with a clinical trial planned for Q2 in the US. AstraZeneca (Cambridge, UK) is making a major push, working not only with Vanderbilt University (Nashville, TN) and the Chinese Academy of Sciences (Beijing, China) on in silico and in vitro assessment of candidates, but is also collaborating with the US Army Medical Research Institute of Infectious Diseases (USAMRIID; Frederick, MD) and the University of Maryland (College Park, MD) for preclinical safety and efficacy assessments. GlaxoSmithKline (Brentford, UK)  has partnered with Vir Biotechnology (San Francisco, CA) to advance two of VIR’s candidates, and Amgen (Thousand Oaks, CA) is working with Adaptive Biotechnologies (Seattle, WA) to develop treatments with neutralizing antibodies against SARS-CoV-2. Celltrion (Seoul, South Korea) claims to have multiple viable neutralizing MAbs and is planning on commencing human trials with selected candidates in July.

Smaller, potentially nimbler companies are also involved in the hunt for SARS-CoV-2-neutralizing MAbs but may need to partner to achieve sufficient manufacturing scale should they succeed. Among these are Sorrento Therapeutics (San Diego, CA).  Sorrento has developed an antibody that showed 100% inhibition of SARS-CoV-2 binding to human cells in assays conducted by their collaborators at the University of Texas Medical Branch (Galveston, TX) using the actual virus. (Many labs do not have access to the actual SARS-CoV-2 virus; pseudo-viruses with the spike or other proteins grafted onto them are used to simulate the virus’ antigen profile.)

MULTI-ANTIBODY COCKTAIL AS DRUG

Concerns over the potential for the virus to mutate its spike protein in ways that might allow it to escape recognition by a single monoclonal and thereby still be able to bind to ACE-2 have many groups considering development of a “cocktail” of two or more neutralizing antibodies. Therefore, as strong as Sorrento considers their lead candidate to be, the company has also announced a partnership with Mount Sinai Health System (New York, NY) to develop an antibody cocktail that is a mixture of three antibodies with each recognizing a specific region of the spike protein. In the same vein, Regeneron Pharmaceuticals (Tarrytown, NY), a company that already makes MAbs for cancer, arthritis, and asthma, announced that it has already designed two antibody cocktail therapies to treat COVID-19 patients after selecting from hundreds of neutralizing antibodies against SARS-CoV-2 using a mouse model and from humans who have recovered from the disease. Regeneron anticipates starting clinical trials in June 2020 and says they hope to provide hundreds of thousands of doses to patients by the end of the summer.

Located in the San Francisco Bay Area, in the largest concentration of biotechnology companies in the world, and with over 25 years of providing services to the biopharma industry, MarinBio is well positioned to provide assistance to researchers working on COVID-19-related research. If you are starting, currently working on, or even just considering a project involving SARS-CoV-2, you should contact us. MarinBio can be an effective and efficient partner to help you maintain pace in the development of COVID-19 diagnostics or therapeutics. MarinBio is staffed by scientists with world-class expertise in the molecular biology and biochemistry of RNA viruses such as SARS-CoV-2. Our team has experience with and knowledge of the molecular interactions that underlie viral pathogenesis, the processes of virion particle assembly and transmission, and the molecular mechanisms by which coronaviruses recognize human cell-surface receptors.

MarinBio is particularly skilled in the construction of assays capable of accelerating your research and accurately identifying targets. For decades, we have been helping our clients successfully develop, qualify, and validate a wide range of molecular tests that include ELISAs, cell-based assays such as detection of neutralizing antibodies, and qPCR tests for RNA or DNA. For further information please contact MarinBio at info@marinbio.com, or call 415 883 8000, or visit our website at www.marinbio.com.