Flow photochemistry transforms peptide amidation for pharmaceutical applications
The revolutionary UV-150 photochemical reactor, employed alongside Vapourtec’s R-Series flow chemistry system, has enabled significant advancements in peptide modification techniques with potential to reshape pharmaceutical manufacturing.
Innovative technology enables post-translational amidation
Scientists at Novo Nordisk have developed a groundbreaking approach to C-terminal α-amidation of peptides and proteins using flow photochemistry technology. The research, published in Nature Communications, demonstrates a three-step process that efficiently converts cysteine-extended polypeptide precursors into their amidated forms – a crucial modification for many therapeutic peptides.
The process utilises Vapourtec’s R-Series flow chemistry system equipped with a UV-150 photochemical reactor to perform a sequence of reactions: cysteine thiol substitution with a photolabel, photoinduced decarboxylative elimination, and cleavage of the resulting enamide. This methodology addresses significant challenges in the commercial-scale production of amidated peptides, which have previously hindered development pipelines for potential drug candidates.
Scalable synthesis overcomes traditional limitations
Peptide-based therapeutics have experienced renewed interest in recent years due to advances in chemical and structural biology. However, traditional peptide synthesis approaches face significant limitations when scaling to commercial production volumes. Whilst solid-phase peptide synthesis (SPPS) remains the standard for laboratory-scale production, it becomes impractical at industrial scale. Recombinant production offers an alternative approach but has historically struggled with C-terminal α-amide modifications – a structural feature present in many biologically active peptides.
The new methodology addresses this limitation through a photochemical process. By conjugating C-terminal cysteine residues to 4-chloro-7-nitrobenzofurazan (NBD-Cl) and subjecting the intermediate to precise irradiation conditions, researchers achieved decarboxylation-fragmentation to produce a C-terminal N-vinyl amide. This intermediate could then be converted to the desired amide through either acid hydrolysis or an inverse electron demand Diels-Alder reaction.
Flow chemistry enables pharmaceutical-scale production
The true innovation lies in the successful scale-up demonstrated using Vapourtec’s flow technology. In one example, researchers prepared an analogue of PYY – an amidated gastrointestinal hormone involved in appetite regulation – starting with 4 grams of material. The process involved reacting the C-terminal cysteine with NBD-Cl, followed by photo-initiated cleavage under flow conditions (430 nm, 24 W, 99% lamp power) with a residence time of just 6 seconds.
In a more ambitious demonstration, 12 grams of a recombinant 81 amino acid GLP1R-amylinR co-agonist precursor peptide was converted to the target peptide amide with 78% yield, showcasing the efficiency of the flow approach.
The researchers noted that the entire C-terminal amidation process – including photolabeling and photochemical conversion – could be completed in a single day, representing a significant improvement over existing methods. Importantly, the authors emphasised that “without the photochemical flow process this reaction would simply not be viable on commercial scale,” highlighting the transformative potential of flow photochemistry for pharmaceutical manufacturing.
Broader applications in peptide therapeutics
The methodology demonstrates broad substrate scope, accommodating both synthetic and recombinant peptides. The research team successfully applied the protocol to several biologically relevant targets, including the GLP-1R agonist GLP-1(7-36) – representing an important class of therapeutic peptides that includes marketed drugs like exenatide and lixisenatide.
Other successfully modified targets included gastrin-releasing peptide, osteocrin, and bulevertide, demonstrating the versatility of the approach across different peptide structures.
