DermaVir vaccine is a novel "pathogen-like" nanomedicine containing a plasmid DNA complexed with a polyethylenimine that is mannobiosylated to target antigen-presenting cells and to induce immune responses (pDNA/PEIm). To develop a commercially viable vaccine product we have systematically investigated the variability of raw materials and their relationship with the product's biological activity. We demonstrated that the cGMP quality requirements are not sufficient to reproducible formulate the nanomedicine with optimal biological activity. Unexpectedly, we found that the high cationic concentration of the pDNA favored the biological activity, but did not support the stability of the nanomedicine. Similarly, the presence of EDTA in the pDNA increased the size of the nanoparticle to microparticles causing the drop of its biological activity. A new parameter, the Cl/N ratio of the PEIm, also influenced the biological activity together with the chemical properties of the solvent. Based on these findings we have developed a pDNA/PEIm formulation capable to maintain the physical stability and the biological activity of the nanomedicine. This work illustrates some of the key steps that must be taken for the implementation of "Quality by Design" (QbD) approach for a biotech product.
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