Physicochemical stability of durvalumab (Imfinzi®) concentrate for solution in original vials after first opening

Abstract

Abstract Objectives Durvalumab (Imfinzi®), a PD-L1 monoclonal antibody (mAb) medication is available as concentrate (50 mg/mL) for solution for infusion. The summary of product characteristics provides information about the physicochemical stability of ready-to-administer durvalumab preparations (vehicle solution 0.9 % NaCl, G5%), but not about the concentrate after first opening. The objective of this study was to determine the physicochemical stability of durvalumab concentrate for solution after first opening over a period of 28 days. Methods Imfinzi® vials were punctured and stored refrigerated (2–8 °C) or at room temperature (20–25 °C) light protected. At predefined time points (day 0, 7, 14, 21, 28) the physicochemical stability of the concentrated solution was determined by ion-exchange/size-exclusion high-performance liquid chromatography (IE-/SE-HPLC) with photodiode array detection and pH measurement. Vials were inspected with regard to changes of color, clarity, and visible particles at any time point. Results Regardless of the storage temperature, durvalumab 50 mg/mL solutions remained physiochemically stable for 28 days in punctured vials. The concentrations of durvalumab monomer remained unchanged and no secondary peaks (fragments, aggregates) were observed in any of the SE-HPLC chromatograms. The IE-HPLC test results showed no substantial changes of the peak areas of the main peak and of the acidic and basic charge variants during the whole storage period. Appearance and pH of the test solutions remained unchanged until the end of the study. Conclusions Regardless of storage conditions none of the analytical methods indicated physicochemical instability of the intact durvalumab monomer over the 28 days of the study. To avoid microbiological instability storage under refrigeration is recommended.