Tuesday, November 9, 2010: 9:45 AM
253 A Room (Salt Palace Convention Center)
Radiolabeled antibodies can be used to deliver a high concentration of radiation to a localized site within a patient's body, and these molecules are becoming increasingly important for medical applications including cancer therapy and imaging. However, widespread clinical application of radioimmunotherapeutic and radioimmunodiagnostic approaches will require production and purification processes that are rapid, efficient, and scalable. Here, a diafiltration-based strategy is described that meets these criteria for the production of radiometal-labeled antibody-chelate conjugates. Moreover, a mathematical model was developed that can be used to determine optimal operating parameters for the diafiltration process to maximize the radiolabeling efficiency of these antibody-chelate conjugates. Conjugation and purification can be completed in <24 h within a single vessel, and the process can be scaled to a desired volume by choosing from commercially available hollow-fiber membrane cartridges with a broad range of membrane surface areas. This model-guided diafiltration strategy was used to produce antibody-chelate conjugates with >95% radiolabeling efficiencies at both the milligram and gram production scale, including GMP-grade material for use in the clinic. Experimental data and theoretical calculations demonstrate that there exists an optimal number of diavolumes to maximize the radiolabeling efficiency of the purified antibody-chelate conjugate, and this optimization requires balancing the removal of excess free chelate from the conjugation reaction with the introduction of additional heavy metal impurities in the diafiltration buffer. An instant thin layer chromatography method was used to indicate the presence of excess free chelate or radiometal in the final radiolabeled antibody product created under different processing conditions. Maximum radiolabeling efficiencies were typically observed between 10 and 15 diavolumes for the post-conjugation purification of the antibody-chelate conjugate. This diafiltration process represents a useful approach for the production of radiolabeled proteins with high consistency and efficiency, offering benefits with respect to patient safety, therapeutic efficacy, and overall production cost.