PFEP of Plecanatide: Two-Disulfide Folding under a pH-Sensing Sequence Constraint

Plecanatide is the 16-residue uroguanylin analogue NDECELCVNVACTGCL with Cys4–Cys12 and Cys7–Cys15 disulfides. Its N-terminal Asp2 and Glu3 create a pH-responsive charge environment relevant to conformation and GC-C pharmacology. This article proposes that PFEP should separate manufacturing pH control from the final biological pH-response question. A four-cysteine kinetic model predicts 79.1% native connectivity after a two-stage oxidation/exchange programme compared with 58.7% after static oxidation; synthetic off-pathway dimer falls from 11.2% to 4.0%. These are not observations. The manuscript details sequence-specific ionization, disulfide mapping, pH-dependent conformational assays, and chemical reconstruction controls. Article type: Target-specific mechanistic study with synthetic model data. All numerical results labelled synthetic or modelled are hypothesis-illustration and planning outputs, not experimental measurements. No wet-laboratory experiment, validated process, clinical benefit, or shelf life is claimed.