Cambridge Healthtech Institute’s Kent Simmons recently spoke with Didier Clenet, a Research Scientist in the Formulation & Stability group at Sanofi Pasteur, about his upcoming presentation “Combining Viral Particle Counting, Biological Characterization and Advanced Kinetics to Predict Vaccine Stability”, to be delivered in the Protein Aggregation and Stability meeting at the 2018 PEGS event. PEGS is scheduled for April 30 - May 4, 2018 in Boston, with the aggregation program set for May 3-4.
What are the methods being used to accurately count viral particles in vaccines?
To estimate virus concentration in solution, scientists traditionally use immuno-assays (ELISA, SPR, BLI, etc.). Genomic titer (PCR) is also currently used to extrapolate viral particle concentration in vaccines. We have recently demonstrated that biophysical technics represent a relevant and complementary approach. Nanoparticle tracking analysis (NTA) and Tunable Resistive Pulse Sensor (TRPS) were conveniently used to size and count viral particles contained in a purified vaccine. In fluorescence mode, NTA was able to specifically count antigenic viruses labelled with conformational monoclonal antibodies recognizing surface glycoprotein. Agreement was observed between results obtained by NTA and the more conventional ELISA method.
How can biophysical techniques support the development of virus-based vaccine formulations?
As an example, NTA is appropriate to concomitantly count antigenic viruses (i.e. to determine antigenicity of sample) and determine their size distribution. We can take advantage of this capability to better understand the link between antigenicity and aggregation state of samples. During forced degradation studies, increase in polydispersity of particle size distribution and loss of antigenicity were concomitant, illustrating how biophysical tools can be beneficial to identify virus degradation pathways during thermal stress.
Can forced degradation studies be used to anticipate long-term product stability under recommended storage conditions?
Thermal stresses are useful to determine kinetic parameters. As long as forced degradation studies are adequately designed (i.e. typically comprising of at least 20 experimental data points obtained at 25°C, 37°C, 45°C over several weeks), a combination of advanced kinetics and statistical analyses can advantageously be applied to accurately describe the losses observed for stability-indicating parameters (antigenicity, purity, monomer content, etc.). Based on experimental data collected over several weeks, our results uncovered the potential of a kinetic-based modeling approach to predict long-term stability of products under recommended storage conditions (shelf-life).
How stable is stable? Are we able to predict stability of vaccines from production to time of use?
Yes, kinetic-based modeling approach can advantageously be used to evaluate the impact of temperatures excursions outside the recommended storage conditions on vaccine quality. Additionally, our experimental results confirm that the impact of cold chain breaks during product shipments and short temperature excursions above 40 °C can be predicted with high accuracy (see D. Clénet in EJPB, 2018). The prediction of changes in vaccine properties from production to their time of use can significantly support the formulation, process development and optimization of supply chain procedures. Increased knowledge pertaining to vaccine stability behavior and their thermosensitivity could certainly have economic impacts and provide financial gain.
Didier Clenet, Research Scientist, Formulation & Stability, Sanofi Pasteur, France
Didier has joined R&D Formulation & Stability platform of Sanofi-Pasteur in 2011. He focuses his work on high throughput screening formulations, stability prediction using advanced kinetics, vaccine activity – structure relationship, particulate matter in vaccines and adjuvants process optimization and physic-chemical characterization.
For more than 15 years in Sanofi R&D, Didier was dedicated on physical and biophysical characterization of active ingredients, freeze-dried products and monoclonal antibodies (mAbs, ADC). His research interests are structural characterization and aggregation state determination using a variety of biophysical techniques (light scattering, flow-imaging, DSC and thermokinetics, fluorescence and infra-red spectroscopy, …. ). Didier implemented Biophysical lab and a lab-automation platform for bioproduct formulations.
He is coaching young scientists and performed courses in several French Universities.