Lyophilized formulation development and characterization of stable glatiramer acetate/oligonucleotide polyplexes at...

Glatiramer acetate (GA) electrostatically complexes with cytosine-guanine oligodeoxynucleotides (CpG ODN), forming ∼100 nm cationic nanoparticles that localize this potent immunostimulant to the injection site. We previously reported GA-CpG nanoparticles retained the anti-tumor activity of CpG while mitigating systemic immune-related adverse events. Nonetheless, nanoparticulate systems like polypeptide-oligonucleotide complexes pose challenges with reproducible production, in-use stability, and storage stability, which must be solved before translation for clinical use. In this study, we systematically investigated a microfluidic mixing process to define reproducible production of GA-CpG nanoparticles. Dynamic light scattering measurements revealed significantly smaller and more uniform nanoparticles for microfluidic processing versus traditional mixing via pipette. We screened a range of buffer systems to determine the pH and ion types that could maintain colloidal stability and CpG potency. Buffer screening tests indicated that amino acid buffers, particularly glutamic acid, better maintained particle consistency than commonly used parenteral buffers. Finally, formulations of potential lyoprotectants and GA-CpG nanoparticles were developed. Freeze-thaw and freeze-drying experiments were conducted to assess the effects of buffers and lyoprotectants. Formulations with 5% HP-β-CD or trehalose yielded mean particle sizes of less than 127 nm and retained even after storage for 6 months at 40 °C/75% relative humidity. The work on electrostatic complexes reported here may provide valuable guidance to formulators aiming to optimize polypeptide-based oligonucleotide polyplex products for in-use or long-term stability.