Solid-Phase Synthesis of Semaglutide: Using Novel Fragment Coupling Strategy to Overcome Aggregation, Improve yield and Quality

Semaglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist of considerable clinical importance in the management of type 2 diabetes mellitus, presents a formidable synthetic challenge owing to its extended peptide sequence, multiple stereochemical defined residues, and the presence of labile functionalities prone to side reactions. It is well known that Serine (Ser) and Threonine (Thr) generally induce aggregation Tamas et al. 2026, by specifically selecting this particular fragment containing two Serine residue, and found a specific sequence that overcame the typical aggregation issues, consequently increasing both purity and yield of the final product.

Herein, we disclose a novel and efficient synthetic route to Semaglutide employing a rationally designed hexapeptide fragment, assembled via solid-phase peptide synthesis (SPPS) under carefully optimized conditions, which is subsequently introduced through fragment condensation at a late stage of the Semaglutide synthesis.

The fragment condensation strategy afforded Semaglutide with an overall yield of 30% and a HPLC purity of 99.88%. Most notably, oligomer content, aspartic acid related variants and D -Ser/ D-Leu diastereomers were reduced to below the limit of detection.

This work underscores the enduring relevance of synthetic design and reaction optimization in the preparation of complex peptide therapeutics. The fragment based approach significantly reduced aggregation and process-related impurities, resulting in substantial improvement in yield and purity compared with conventional stepwise peptide elongation protocols, thereby demonstrating an efficient and robust strategy for Semaglutide synthesis.