Formulation And Characterization of Biologics – From siRNA to Monoclonal Antibodies

Biologics are a rapidly growing class of therapeutics, encompassing a wide range of modalities, with gene therapy products and monoclonal antibodies (mAbs) constituting the majority. Proper formulation and characterization of these complex therapeutics is crucial to ensure their safety and therapeutic efficacy. This dissertation focuses on two main areas: the development of a novel renal-targeted siRNA delivery system and the assessment of structural and conformational stability of mAbs in a simulated subcutaneous (SC) environment. The first part of this dissertation presents the synthesis and characterization of a novel renal-targeted polymer for selective siRNA delivery to injured kidneys. Inulin was modified with α-cyclam-p-toluic acid (CPTA), imparting targeting properties to cells overexpressing the CXCR4 receptor. In a mouse model of cisplatin-induced AKI, self-assembled IC/siRNA polyplexes showed rapid accumulation in injured kidneys, with selective uptake and prolonged retention in renal tubules overexpressing the CXCR4 receptor. Systemically administered polyplexes of IC and siRNA against p53 effectively silenced p53 expression in the injured proximal tubules, leading to positive therapeutic outcomes in a murine model of cisplatin-induced AKI. These results indicate IC's potential as a renal-targeted siRNA delivery system. The second part of this dissertation investigates the physiochemical stability of mAbs in a simulated SC environment using a novel in vitro instrument, the Subcutaneous Injection Site Simulator (SCISSOR). Limited knowledge exists regarding alterations in the structural stability and integrity of mAbs following injection in the SC space. We utilized the SCISSOR to probe for physicochemical changes in seven mAbs following SC injection using various analytical techniques. After 24 h, all mAbs demonstrated a relative decrease in conformational stability, an increase in fragmentation, and elevated acidic species. Higher order structure analysis revealed a deviation in the secondary structure from the standard and an increase in the number of unordered species. Our findings suggest an overall reduced stability of mAbs after SC administration. Decreased stability could have a potential impact on safety and efficacy. In vitro systems like the SCISSOR, when combined with downstream analyses, offer valuable insights for evaluating the suitability of lead molecules and optimizing formulation design for specific administration in the intended body compartment, thereby enhancing the likelihood of clinical success.