(T1330-01-04) Platform Formulation Approach for Injectable GalNAc siRNA

Purpose: GalNAc-conjugated siRNA consists of double-stranded oligonucleotides with unique structural and physicochemical properties, which influence key formulation parameters such as appearance, pH, viscosity, osmolality, and density. These attributes are critical to both formulation and process development. This study evaluates over 10 GalNAc siRNA molecules to establish a robust formulation platform. The primary goal was to optimize tonicity, pH, and viscosity to ensure product manufacturability, usability, and performance. Higher viscosity, in particular, can hinder manufacturing, filtration, and injectability.

Methods: GalNAc siRNA solutions were prepared at varying concentrations, and key physicochemical properties, including appearance, osmolality, pH, viscosity, and density, were measured. Appearance was assessed using the EU color standard with a lightbox. Concentration was determined using a Cary 300 UV-Vis spectrophotometer (Agilent Technologies, USA). Osmolality was measured using an OsmoTech Pro 2020 osmometer (Advanced Instruments, USA). pH was recorded with a MicroPro ISM pH meter (Mettler-Toledo, USA). Density measurements were performed using an SVM 2001 viscometer (Anton Paar, Austria). Viscosity was analyzed with a VROC Initium One Plus viscometer (Rheosense, USA) over a temperature range of 5 to 37 °C.

Results: All tested GalNAc siRNA molecules exhibited similar concentration-dependent physicochemical properties. Increasing siRNA concentration resulted in proportional increases in viscosity, osmolality, and density, regardless of molecular structure or weight. A decrease in pH was observed with increasing concentration. Sodium phosphate buffer was identified as the optimal buffering agent due to its compatibility with GalNAc siRNA properties. Sodium chloride was selected as the tonicity modifier, successfully enabling isotonic formulation development.

Conclusion: GalNAc siRNA demonstrates unique, concentration-dependent physicochemical properties that are largely independent of molecular weight. These characteristics facilitated the development of a robust and scalable formulation platform. By optimizing siRNA concentration, buffer composition, and tonicity adjustments, injectable formulations suitable for subcutaneous delivery were achieved. This platform provides a streamlined and predictable approach for the development of GalNAc siRNA therapeutics.

Figture 1. Effect of concentration on osmolality ( example)

Figure 2: Effect of concentration on viscosity (example)