Kinetic Optimization and Scale-Up of Site-Specific Thiol-PEGylation of Loxenatide from Laboratory to Pilot Scale

PEG-loxenatide is a new once-weekly GLP-1 receptor agonist candidate for the treatment of type 2 diabetes mellitus. Site-specific thiol-PEGylation of loxenatide with Y-shaped mPEG2-MAL of 40 kDa was first optimized using a reaction kinetic model based approach on a laboratory scale. The optimized reaction conditions were further scaled up to a pilot scale, and PEG-loxenatide achieved a high yield and purity. This result demonstrated an efficient and convenient scale-up PEGylation reaction process, which achieved the maximum utilization of the raw materials and the minimum generation of byproducts. Furthermore, PEG-loxenatide was efficiently purified using cation exchange chromatography on a pilot scale. The purified PEG-loxenatide was further desalted, concentrated, and lyophilized to improve its stability. PEGylation site analysis revealed that a single PEG molecule was conjugated to the unique cysteine residue at the C-terminus of loxenatide. This study will provide useful information for the preparation of PEG-loxenatide on an industrial scale.