Characterization of disulfide bridges containing cyclic peptide Linaclotide and its degradation products by using LC-HRMS/MS

Linaclotide (LINA) is a first-in-class guanylate cyclase agonist used for treating irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation. Stress degradation studies were performed to examine LINA's intrinsic stability, adhering to International Council for Harmonisation of Technical ICH) guidelines Q1A (R2). The current study endeavours to elucidate the stability behavior of LINA by exposing various stress conditions. A simple LC method was developed for effective separation of all LINA degradation products using a Waters Symmetry C18 column (150 ×4.6 mm, 3.5 µm) as the stationary phase. The generated degradation products were identified and characterized by using high-resolution mass spectrometry (LC-HRMS), MS/MS studies. The mechanistic fragmentation pathway for the seven degradation products was established and the chemical structure for the identified degradation products was elucidated. LINA was susceptible to degrade under acidic, basic, neutral, photolytic, and oxidative conditions. A total of three Pseudo DPs, DP-1, DP-2, and DP-3, were formed under acidic conditions while using methanol as the co-solvent. Additionally, degradation products (DPs) were identified: DP-4 formed under basic stress condition and DP-5 under neutral, thermal, and photolytic conditions. Furthermore, DP-6 and DP-7 were formed under oxidative stress condition. This study established the mechanistic fragmentation pathways and elucidated the chemical structures of the degradation products, offering valuable insights for generics and novel formulation drug development.