After identifying the 24 specific nanobodies with high affinity to the new coronavirus N- protein and S-protein antigens through high-throughput screening in May 2020, the scientific team has used structural biology, computational biology and biophysical methods to further analyze and improve the properties of these nanobodies. Through rational design and transformation, the affinity and specificity of these nanobodies have been greatly enhanced.
Out of the 24 nanobodies, 16 deal with the S-protein which can be used as antiviral therapeutics and the other 8 deal with the N-protein, for use as a marker in diagnostic assays. The scientists have successfully established a prokaryotic expression and purification system for nanobodies in vitro. In this respect, they have expressed and purified the 16 S-protein nanobodies with a purity of 98%. For the 8 N-protein nanobodies, the nanobody expression vectors have been constructed, and the antibodies purified. The Elisa and Isothermal Titration Calorimetry (ITC) methods were successfully used to determine the affinities of antigens and antibodies, and nanobodies with good affinity were selected for affinity enhancement and humanization.
The scientific team is now moving ahead with its collaboration with an international Contract Research Organization, Genscript Biotech Corporation, to jointly target the coronavirus-specific nanobodies and conduct pseudovirus neutralization test with the objective of screening out nanobodies with strong affinity and good efficacy to prevent the virus infection.
On this basis, the team will optimize and humanize these nanobodies combining structure-based design and random mutations. They will use PML (Precise Mutant Library) database and FASEBA (Fast Screening for Expression, Biophysical-Properties and Affinity) screening technology to carry out the affinity maturation test of the nanobodies, and proceed with further purification and verification to obtain the lead nanobody. The humanized modification and affinity maturation of nanobodies are expected to be completed within the next 3 months.
The next stage of the study will further advance the preclinical research study such as live virus testing, animal testing and formulation development. The animal testing is aimed to be completed by end-2020 to be followed by the human clinical trials which will take a year to complete. The nanobodies can be used for treatment of coronaviruses, which include the SARS-CoV-2 coronavirus, the SARS coronavirus of 2003 and MERS coronavirus of 2012.
“These results from our preclinical study highlight the potential of the nanobody-based science and represent an important step forward in our research and development efforts for an effective medical cure and diagnostic assay for the COVID-19 virus. We are committed to winning the global battle against COVID-19 pandemic in a safe and effective manner,” commented Jacky Zhang, chairman and CEO of Beroni Group Limited.