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Coronavirus in the crosshairs, Part 2: Vaccines in development

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Biopharmaceutical companies, government agencies, academic institutions and non-profits located world-wide have mobilized in an unprecedented effort to develop interventions that are effective against SARS-CoV-2, the virus that causes COVID-19. This global pandemic, however, affects people of all ages and every health status. As a consequence, we need a wide array of medicines, as well as vaccines, to ensure the right intervention is given to the right person. And we need these interventions as quickly as possible.

In Part 1 of ‘Coronavirus in the crosshairs’, we focused on early clinical studies for small molecule drugs that were re-purposed, i.e., drugs that were already approved or in clinical studies for another disease, but were tested for efficacy in COVID-19 patients. In Part 2 of this series, we focus on vaccines currently in clinical study. Part 3 will focus on the use of anti-SARS-CoV-2 polyclonal antibodies found in convalescent plasma as a treatment for COVID-19, and Part 4 will examine efforts to quickly discover anti-SARS-CoV-2 antibody therapeutics.

Vaccines in preclinical and clinical development

The World Health Organization has compiled a list of SARS-CoV-2 vaccine initiatives that, as of March 20, 2020, included 42 vaccines in preclinical development and 2 vaccines in human Phase 1 studies, National Institutes of Health (NIH)/Moderna’s mRNA-1273 vaccine and CanSino Biological Inc./Beijing Institute of Biotechnology’s adenovirus Type 5 vector (Ad5-nCoV) vaccine.

In addition, the Regulatory Affairs Professionals Society is maintaining the Regulatory Focus COVID-19 Tracker, which is a resource for information on COVID-19 vaccine development that is updated weekly.

mRNA-1273 vaccine candidate

mRNA-1273 is a novel lipid nanoparticle-encapsulated mRNA-based vaccine that encodes for a full-length, prefusion stabilized spike protein of SARS-CoV-2. The  vaccine candidate has shown promise in animal models. Manufacturing of mRNA-1273 for the Phase 1 study (NCT04283461) was supported by the Coalition for Epidemic Preparedness Innovations. On March 16, 2020, NIH announced the study, which will assess the safety and immunogenicity of mRNA-1273,  had started. A total of 45 adults between the ages of 18 to 55 years will be enrolled, and the estimated primary completion date of the study is June 1, 2021. According to the protocol, however, the immunogenicity data will start being collected by mid-May 2020. Moderna announced on March 23, 2020 that, under emergency use, a vaccine could be available to some people, possibly including healthcare professionals, in the fall of 2020, although a commercially-available vaccine is not likely to be available for at least 12-18 months.

Enrollment will occur at the Kaiser Permanente Washington Health Research Institute. Forty-five healthy adults will be administered one of three doses (25 microgram [mcg], 100 mcg, 250 mcg). They will receive an intramuscular injection of mRNA-1273 on Days 1 and 29 in the deltoid muscle, and will be followed through 12 months post second vaccination (Day 394). The first four participants will receive one injection with the low dose, and the next four participants will receive the 100 mcg dose. Investigators will review safety data before vaccinating the remaining participants in the 25 and 100 mcg dose groups and before participants receive their second vaccinations. Another safety review will be done before participants are enrolled in the 250 mcg cohort. Follow-up visits will occur 1, 2 and 4 weeks post each vaccination, as well as 3, 6 and 12 months post second vaccination.

The primary objective is to evaluate the safety and reactogenicity and the secondary objective is to evaluate the immunogenicity as measured by IgG ELISA to the 2019-nCoV S protein following a 2-dose vaccination schedule of mRNA-1273 at Day 57.

Ad5-nCoV vaccine candidate

On March 17, 2020, CanSino Biologics Inc. announced that its recombinant novel coronavirus vaccine Ad5-nCoV, co-developed with Beijing Institute of Biotechnology, has been approved to enter into a Phase 1 clinical trial. The Phase 1 ChiCTR2000030906 study was listed as recruiting patients when its record was accessed March 23, 2020; NCT04313127 is assumed to be the same study.

The single-center, open and dose-escalation Phase 1 clinical trial will evaluate Ad5-nCoV in healthy adults aged between 18 and 60 years. Three doses will be evaluated, with a total of 108 patients (36 per study arm) receiving a low (5E10 vp Ad5-nCoV), medium (1E11 vp Ad5-nCoV) or high (1.5E11vp Ad5-nCoV) dose of vaccine. Various types of antibody responses will be measured at Day 14, 28, and months 3 and 6 post injection.

Other vaccine candidates

Clinical studies of two additional vaccine candidates, Covid-19 aAPC Vaccine and Covid-19 Synthetic Minigene Vaccine, are listed on clinicaltrials.gov as recruiting patients (NCT04299724 and NCT04276896, respectively), although the status of these initiatives could not be confirmed as of March 23, 2020. Both vaccine candidates are sponsored by Shenzhen Geno-Immune Medical Institute, Shenzhen Third People’s Hospital, and Shenzhen Second People’s Hospital.

Coronavirus image from: CDC/ Alissa Eckert, MS; Dan Higgins, MAMS

Coronavirus in the crosshairs, Part 1

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Coronaviruses (CoVs) are enveloped positive-sense single-stranded RNA viruses that can cause highly lethal respiratory disease in humans, such as Middle East respiratory syndrome (MERS) and severe acute respiratory syndrome (SARS). The current coronavirus disease (COVID-19) pandemic is caused by the SARS-CoV-2 coronavirus. Infection in humans is initiated through exposure of the respiratory tract to the virus, which enters cells by binding angiotensin-converting enzyme 2 (ACE2) found on the cell surface.[1] Wrapp et al.[2] have shown that the SARS-CoV-2 spike protein binds to ACE2 with ~10- to 20-fold higher affinity than the spike protein of SARS–CoV, which is a coronavirus that caused an epidemic in 2002-2003.

An urgent and immediate need for knowledge about COVID-19 and for drugs to inhibit the virus and treat symptoms has existed since the disease started to spread in December 2019. To address this need, medical professionals have initiated numerous trials to identify key characteristics of the infections and the effects of investigational and approved drugs, including those used during the MERS and SARS outbreaks. As of March 19, 2020, clinicaltrials.gov already included ~115 studies related to COVID-19, with ~40 designed as observational studies or studies of diagnostics or devices, and ~75 designed to evaluate interventions such as antiviral drugs. Of the interventional studies, ~40 are currently recruiting patients, and the rest have not yet started recruiting. The earliest of these studies were started in China in late January 2020; additional studies may be listed on the Chinese clinical trials registry. Many studies are designed to produce results rapidly, which may greatly assist treatment of patients in the near future.

Effective in vitro inhibition of SARS-CoV-2 by remdesivir and chloroquine has been reported,[3] and numerous clinical studies are underway to determine the efficacy of these drugs as COVID-19 treatments.[4] Remdesivir (GS-5734, Gilead Sciences Inc) is an investigational monophosphoramidate prodrug of an adenosine analog with potent activity against an array of RNA virus families, including Filoviridae, Paramyxoviridae, Pneumoviridae, and Orthocoronavirinae, through the targeting of the viral RNA-dependent RNA polymerase. It was previously tested in humans with Ebola virus disease, and has demonstrated positive results in animal models of MERS.[5] Numerous clinical studies of the effects are remdesivir are ongoing, including:

  • NCT04257656, started February 6, 2020 in China, with estimated enrollment of 453 patients and a primary completion date of April 3, 2020.
  • NCT04252664, started February 12, 2020 in China, with estimated enrollment of 308 patients and a primary completion date of April 20, 2020.
  • NCT04280705, started February 21, 2020 in the US, South Kora and Singapore, with estimated enrollment of 394 patients and a primary completion date of April 1, 2020.[6]
  • NCT04292899, started March 6, 2020 in the US, South Kora and Singapore, with estimated enrollment of 400 patients and a primary completion date of May 2020.
  • NCT04292730, started on March 15, 2020 in the US, South Kora and Singapore, with estimated enrollment of 600 patients and a primary completion date of May 2020.

The U.S. Army Medical Research and Development Command is sponsoring a study of remdesivir (NCT04302766) with enrollment limited to DoD-affiliated personnel (including active and reserve component service members, US civilian employees, contractors, other US personnel, and dependents of any age, as well as allied military forces and local nationals) who have a COVID-19 diagnosis and have been granted access to the medical facility.

Hydroxychloroquine, which is FDA-approved as a treatment for malaria, lupus and rheumatoid arthritis, appears to interfere with terminal glycosylation of ACE2 and is known to elevate endosomal pH, which may inhibit virus binding and subsequent infection.[7] Preliminary evidence from a small study in humans suggests that the combination of azithromycin and hydroxychloroquine is significantly more efficient for virus elimination.[8] 

At least 3 clinical studies of the effects are hydroxychloroquine are ongoing:

  • NCT04261517, started February 6, 2020 in Shanghai, with estimated enrollment of 30 patients and a primary completion date of August 2020.
  • NCT04307693, started March 11, 2020 in Seoul, South Korea, with estimated enrollment of 150 patients and a primary completion date of May 2020.
  • NCT04308668, started March 2020 in Minneapolis, Minnesota, United States, with estimated enrollment of 1500 patients and a primary completion date of May 2021.

On March 18, 2020, the World Health Organization announced that they are planning a multi-arm clinical trial that will evaluate the following drugs as treatments for COVID-19:

  • Remdesivir;
  • Hydroxychloroquine or chloroquine;
  • Lopinavir-ritonavir (a combination of two HIV drugs marketed as Kaletra or Aluvia); and
  • Lopinavir-ritonavir plus interferon beta.

Argentina, Bahrain, Canada, France, Iran, Norway, South Africa, Spain, Switzerland, and Thailand have offered study sites, and sites in other countries may be added in the future. The study, called SOLIDARITY, will use an adaptive design, which allows study arms to be modified, added or eliminated based on the results of ongoing data collection.[9] The lopinavir-ritonavir arms are included in the SOLIDARITY study despite the negative results of a clinical study of 199 hospitalized adult patients with severe COVID-19 in China, which showed no benefit from adding lopinavir–ritonavir treatment to standard care.[10] Further study is needed to understand whether factors such as the drug dose or patient characteristics (age, severity of disease, underlying medical conditions) affected the possibility of a treatment benefit.

In addition, positive results have been reported for the antiviral agent favipiravir (Avigan), which was evaluated in COVID-19 patients in clinical trials conducted in Wuhan and Shenzhen, China. Favipiravir was approved in 2014 in Japan for treatment of influenza, although use is limited because the drug may cause fetal deaths or deformities. Additional studies in COVID-19 are needed, however, results reported by Japanese health officials suggest the drug is less effective in patients with more severe symptoms.[11]

Other antiviral treatments are currently being evaluated, including anti-SARS-CoV-2 inactivated convalescent plasma (NCT04292340), as are therapies that can ameliorate symptoms of the disease, including anti-IL-6 sarilumab (NCT04315298) and anti-IL-6 receptor tocilizumab (NCT04306705, NCT04310228), which may reduce lung inflammation and improve lung function in COVID-19 patients.

Scientists are searching for new treatments and vaccines, which will be discussed in our upcoming posts.

1. Walls et al. Structure, Function, and Antigenicity of the SARS-CoV-2 Spike Glycoprotein. Cell. March 09, 2020. DOI:https://doi.org/10.1016/j.cell.2020.02.058
2. Wrapp et al. Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation. Science 2020, 367, 1260-1263.
3. Wang et al. Remdesivir and chloroquine effectively inhibit the recently emerged novel coronavirus (2019-nCoV) in vitro. Cell Research 2020, 30, 269–271.
4. Food and Drug Administration, March 19, 2020. Coronavirus (COVID-19) Update: FDA Continues to Facilitate Development of Treatments.
5. National Institutes of Health, February 13, 2020. Remdesivir Prevents MERS Coronavirus Disease in Monkeys.
6. National Institutes of Health, February 25, 2020. NIH clinical trial of remdesivir to treat COVID-19 begins.
7. Vincent et al. Chloroquine is a potent inhibitor of SARS coronavirus infection and spread. Virology Journal 2005, 2, 69.
8. Gautret et al. (2020) Hydroxychloroquine and azithromycin as a treatment of COVID‐19: results of an open‐label non‐randomized clinical trial. International Journal of  Antimicrobial Agents – In Press 17 March 2020 – DOI : 10.1016/j.ijantimicag.2020.105949
9. WHO Director-General’s opening remarks at the media briefing on COVID-19 – 18 March 2020.
10. Cao et al. A Trial of Lopinavir–Ritonavir in Adults Hospitalized with Severe Covid-19. New England Journal of Medicine. March 18, 2020. DOI: 10.1056/NEJMoa2001282.
11. Watanabe S, Chan M, Suzuki W. China says Japan-developed drug Avigan works against coronavirus. Nikkei Asian Review. March 18, 2020.

Coronavirus image from: CDC/ Alissa Eckert, MS; Dan Higgins, MAMS

FDA issues guidance on conducting clinical trials during the COVID-19 pandemic

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In these challenging times, the biopharmaceutical industry, government agencies, as well as academic and non-profit organizations, are working toward the development of antibody therapeutics and vaccines for the treatment and prevention of infection by SARS-CoV-2, the virus that causes COVID-19. The Antibody Society is currently compiling information on these efforts, which will soon be posted on our website and distributed via email to our members. Many existing antiviral treatments are also being re-purposed in the fight against the virus.

The Society is an authoritative source of information on antibody therapeutics in the clinical pipeline. The COVID-19 pandemic, however, may delay ongoing clinical studies that are evaluating the safety and efficacy of therapeutics for other diseases. In a March 18, 2020 press release, the U.S. Food and Drug Administration (FDA) notes that challenges may arise from quarantines, site closures, travel limitations, interruptions to the supply chain for the investigational product, or other considerations if site personnel or trial subjects become infected with SARS-CoV-2. These challenges may lead to difficulties in conducting the clinical trials. Protocol modifications may be required, and there may be unavoidable protocol deviations due to COVID-19.

Information about FDA’s guidance for industry, investigators and institutional review boards conducting clinical trials during the coronavirus (COVID-19) pandemic can be found here.

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COVID-19 Demands Increased Public Sharing of Biomedical Research Data

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Defeating the coronavirus pandemic will require unprecedented cooperation from the research community. This is especially true for the Adaptive Immune Receptor Repertoire Community (AIRR-C), given the paramount importance of antibodies and T cells for vaccines, diagnostics, and therapeutics in viral infection. Therefore, the AIRR-C hereby calls upon its members, and the wider research community, to share experiences, resources, samples, and data as openly and freely as possible, and to work within their respective systems to break down barriers to achieve this goal, subject to the overarching directives of respect, privacy, and protection for patients and all people. We are in this together.

Molecular Biology Can Improve Antibody Drug Developability

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Contributed by  Nick Hutchinson, FUJIFILM Diosynth Biotechnologies

The discovery and development of antibody therapeutics often adheres to a series of stages starting with target identification and progressing through lead generation, lead optimization, then testing in preclinical and clinical studies. Molecular biologists engineer antibodies during lead generation and optimization to improve a range of characteristics, including antibody specificity and potency, or to reduce immunogenicity and the rate of elimination from the body (1).

Next-generation antibody biopharmaceuticals include bispecifics, glyco-engineered antibodies and antibody-fusion proteins with complex architectures. While drug development scientists may use antibody engineering techniques to generate candidates with very desirable or improved functional properties, at the same time, these can alter the biochemical, biophysical and in vivo properties of the antibody candidate, which can be detrimental to the overall target product profile (2). Engineering antibodies to improve their functional properties is frequently performed without consideration for the subsequent developability, including manufacturability, of the molecule. These issues are then often identified at a relatively late stage in the discovery process, after substantial resources have been invested in the molecule and, therefore, can have a real financial impact on drug development companies that may be being kept alive by funding from investors.

Ideally, antibody therapeutics should be capable of being manufactured with high productivity and at high quality with low protein heterogeneity. From a developability perspective, it is preferable if they express to high titer from the mammalian cell expression system and are stable during production storage and delivery (1). Some antibody candidates can exhibit a propensity to partially unfold, revealing hydrophobic patches that are more normally buried inside the molecule. Once revealed, the patches can interact with one another, leading to aggregation. Other liabilities that reduce developability include low solubility, unstable amino acids, clipping and antibody fragmentation (1). These can be sufficiently severe that projects can be cancelled due to poor toxicology data and concerns around whether the candidate can be safely administered to patients during clinical trials.

One solution, advocated by investigators from Roche (2), is to assess developability during antibody drug discovery. Their workflow incorporates two separate assessments, the first following the initial candidate screening and selection and the second following humanization and re-engineering, but before the selection of the clinical lead. During the first phase of the assessment, complementarity-determining regions are analysed in silico for potential liabilities such as degradation sites. This can be followed by studies on stressed samples, with samples incubated at elevated temperatures for two weeks. Stable candidates can progress to the next stage or drug development scientists can use humanization and protein re-engineering to remove the identified liabilities. The second phase, which follows humanization, again employs in silico tools but evaluates the whole humanized molecule and assesses potential hotpots where post-translational modification, charge variations or degradation might occur. Researchers then perform a second stress test for the most likely or detrimental liabilities. During this phase, they can include tests for self-interaction and aggregation, such as apparent hydrophobicity by hydrophobic interaction chromatography, thermal stability by dynamic light scattering (DLS), protein-protein self-interaction by DLS and viscosity at high concentration by DLS with latex beads (2).

Other groups have gone further, and not only select for candidates with properties that limit manufacturing and storage risks, but also apply molecular engineering techniques in order to improve manufacturability proactively. For example, in 2019, a team from AstraZeneca described manufacturing challenges they encountered during downstream purification of an antibody that was undergoing liquid-liquid phase separation (3). This in turn resulted in the need for longer mixing times that can be damaging for proteins, yield losses, increases in pressure during processing and misleading analytical results from in-process samples. The team attempted to resolve the problem by optimize the bioprocessing conditions, but there were still substantial limitations to large-scale manufacturing. To fix the problem, they used in silico homology modelling and charged-patch analysis to identify problematic residues, and this ultimately lead them to substitute charged residues with those with a neutral or opposite charge. Their research showed that these substitutions minimized electrostatic interactions and allowed them to engineer a variant that maintained antigen-binding affinity, but eliminated the liquid-liquid phase separation behaviour.

The molecular engineering of therapeutic antibodies is allowing development of candidates with ever improved functional properties. However, researchers should consider, where possible, the impact of this engineering on the biochemical and biophysical characteristics of the molecule, which can have a negative effect on the developability of lead candidates. Incorporating screens for developability during drug discovery workflow can help eliminate candidates with liabilities that will prevent them from being successful drugs. The more sophisticated developers of antibody therapeutics are cleverly applying molecular biological techniques to improve the stability and manufacturability of their monoclonal antibody leads.

(1) Chiu, M.L. & Gilliland, G.L. (2016) Engineering antibody therapeutics. Current Opinions in Structural Biology, 38: 163-173.

(2) Jarasch, A., Koll, H., Regula, J.T., Bader, M., Papadimitriou, A. & Kettenberger, H. (2015) Developability assessment during the selection of novel therapeutic antibodies. Journal of Pharmaceutical Sciences, 104:1885-1898.

(3) Du, Q., Damschroder, M., Pabst, T.M. Hunter, A.K., Wang, W.K. & Luo, H. (2019) Process optimization and protein engineering mitigated manufacturing challenges of a monoclonal antibody with liquid-liquid phase separation issues by disrupting inter-molecule electrostatic interaction. MAbs, 11 (4): 789-802.

The Antibody Society is an authoritative source of information about antibody therapeutics development. We are pleased to provide original posts and news summaries on our homepage, as well as semi-monthly summaries of recent news to our members.  Archived news from 2019 can be found in the Web Resources section of the Society’s website.