Exenatide Synthesis and Impurities

Exenatide is mainly synthesized by the classic solid-phase synthesis method combined with fragment synthesis method. During the synthesis, placement and preparation process of exenatide, some miscellaneous peptides similar in structure and properties to exenatide will be produced, such as Amino acid insertion/deletion, diastereoisomers, etc., the structure and physicochemical properties of these exenatide impurities are almost the same as exenatide. The analysis of these exenatide impurities will help us better understand its medicinal chemical properties and provide more support for the research and development of exenatide.

Peptide Characterization and Exenatide Impurities

The identification of peptides is not simple and can be completed by a single detection. The confirmation of its primary structure generally uses mass spectrometry to determine the relative molecular mass, chromatography to determine the amino acid composition, and mass spectrometry combined with enzyme digestion or Edman degradation to determine the peptide sequence. The secondary structure of a polypeptide is actually a local structure formed by the peptide chain due to hydrogen bonds. Its confirmation generally includes detection methods such as X-ray single crystal diffraction, nuclear magnetic resonance, infrared, ultraviolet, and circular dichroism.

High-performance liquid chromatography (HPLC) is the main method for the identification, separation and quantification of peptides and their related impurities. The development of long-acting formulations of Exenatide includes PEG derivatives and dimerized Exenatide, microsphere injections, etc.

Omizzur Biotech 

Omizzur Biotech is a custom peptide synthesis company in China. Omizzur provides a series of customized synthesis services for exenatide impurities, Salmon Calcitonin, Octreotide, Tripeptide, etc with analysis reports ,certificates for HPLC, MS, COA, COO,BSE, etc. Omizzur sign a customer privacy agreement to 100% protect customer privacy . Please send inquiry to Omizzur team for help.

OMIZZUR LTD is an integrated specialty peptide company powered by a robust custom peptide synthesis services and a growing branded business as well as pharmaceutical intermediates, biosimilars markets. Omizzur provide peptide products and services to pharmaceutical companies, clinical research labs, universities, biotech companies etc.  

Omizzur scientists have extensive expertise experience in developing of various peptides and amino acid derivatives (cyclic peptide, peptide library, peptide impurities etc. We have a complete certified ISO 9001 quality control system, all peptide products have undergone dual quality testing by QC and QA to a 100% pass rate of products. We are Omizzur and we make research efficient.

What is Custom Peptide Synthesis?

The synthesis of peptides can be divided into two main pathways: chemical synthesis and biosynthesis. Omizzur is engaged in chemical synthesis, mainly in the form of condensation between amino acids. The chemical synthesis of peptides can be divided into liquid solid phase synthesis. 

Merrifield, a famous biochemist in the United States, proposed Solid Phase Peptide Synthesis (SPPS), which involves connecting the C-terminal of amino acids to an insoluble resin, and then successively conducting the condensation of amino acids on this resin to extend the peptide chain. Solid phase synthesis methods can be divided into Boc method and Fmoc method. 

Custom peptide synthesis : according to the peptide sequence required by clients, Omizzur synthesizes high quality research-grade peptides on time. We need to know your product structure or sequence, the required quantity. In this process: we will sign a non-disclosure agreement to ensure the privacy of your company.

How To Check The Quality of Synthetic Peptides?

The company keeps all materials provided by customers strictly confidential. Omizzur provides HPLC and MS test results free of charge when sending products. All peptides of the company are purified by reverse phase chromatography. Determine whether the product is correct by measuring the molecular weight of the peptide by mass spectrometry. 

MS test results can also show most of the main impurities. If necessary, net peptide content testing, such as amino acid analysis or elemental analysis, can also be provided. These methods can confirm the amino acid composition of peptides, and they can be used as supplementary methods for peptide confirmation. All delivered peptides are of the purity required by the customer.

Please mail us your product sequences / structural formula, CAS number (if any), our customer service representatives will get in touch with you within 1 hour.

Sources of Peptide Impurities & Peptide Characterization

The solid-phase synthesis of peptides has been widely used nowadays. In the process of peptide synthesis and storage, related structural impurities are easily formed, such as amino acid loss, amino acid insertion, deamination, degradation products, etc. Many related structural impurities not only have no medicinal effect, but have certain toxic and side effects. Therefore, the European Pharmacopoeia requires qualitative analysis of related structural impurities with a content of more than 0.5%, quantitative analysis of related structural impurities with a content of more than 1%, and investigation of their toxic and side effects.

6 peptide impurities that appear during the synthesis & storage of peptides:

1. Amino acid deletion/ insertion

In solid-phase peptide synthesis, incomplete removal of amino acid protecting groups attached to the resin or the introduction of incompletely activated amino acids will reduce the efficiency of the condensation reaction, which will result in the loss of one or more amino acids in the entire peptide chain. During transportation and storage, peptides will also produce a small amount of degradation products, missing one or more amino acids at the N or C-terminus, which can also be classified as amino acid-deleted impurities.

In solid-phase synthesis of peptides, an excess of amino-protected amino acids is often added to ensure maximum condensation efficiency. However, if the excess reactants are not completely washed away after the condensation reaction, additional amino acids will be inserted into the target peptide sequence.

2. Protective group residues

In solid-phase synthesis of peptides, sometimes the protecting group cannot be completely removed (amino group protection, side chain protection, etc.), which will cause the protecting group to remain in the target peptide.

3. Oxidation / reduction

Certain amino acid residues are prone to oxidation/reduction reactions during solid-phase peptide synthesis. Prolonged exposure to light or exposure to air during storage of histidine and lysine can lead to the formation of oxidative impurities. The side chain of tryptophan can be oxidized to generate impurities under acidic conditions, and can also undergo reduction reactions.

4. Diastereomers

Amino acid racemization in peptides. Even a small amount of isomeric impurities, even a single amino acid isomerization, can greatly affect the overall biological function

5. Side chain / terminal modification impurities

Side chain impurities can be mainly divided into 2 categories: impurities introduced by side chain protecting groups and impurities introduced by amino acid side chain itself with reactivity. Such as the deamination of the side chains of two basic amino acids, asparagine and glutamine.

Chain-end impurities include two categories: one is the impurities produced by N-terminal acylation or C-terminal deamidation, such as N-terminal acetylation. Another class of impurities is those formed by reactive groups at the end of the chain.

6. Peptide aggregates

Peptide aggregation can be divided into two types, covalent and non-covalent, and the degree of its formation depends on various environmental factors. Covalent aggregates are usually formed by two monomers through amide bonds and disulfide bonds. Non-covalent aggregates are the result of weak interactions such as hydrophobic interactions and electrostatic interactions. Usually there is an equilibrium switch between non-covalent aggregates and their monomers. During the purification and storage process of peptide drugs, a certain amount of polymeric impurities may be generated.

Popular Peptides & Impurities:

Exenatide, salmon Calcitonin, Octreotide, Terlipatide, make an inquiry to Omizzur Services now.

Salmon calcitonin is a peptide drug containing 32 amino acids synthesized by solid phase synthesis. It is used as the first choice of the treatment of osteoporosis,especially used for bone fracture treatment. Due to its complex amino acid composition and many synthetic steps, the drug has the characteristics of instability and easy degradation, and the impurity composition is relatively complex. It is necessary to analyze the product, deeply study its impurity mass spectrum, establish an analytical method for the correlation between impurities and biological activity, and comprehensively evaluate the effectiveness and stability of the marketed product, so as to ensure the safe, effective and controllable quality of the drug.

Related substances of salmon calcitonin raw materials were detected by LC-MS technology,determine whether it was a known impurity,determine the structure of them. There are two main process impurities,one is isomers,the other is lack of an asparagine. Omizzur use LC-MS technology,preparation,disulfide bond fracture analysis method to determine the structure of the two injection degradation impurities.The salmon calcitonin impurities may produce include the following categories:

1. Salmon calcitonin impurities with amino acid deficiency

Salmon calcitonin impurity that lacks one amino acid. There are 32 possible impurities, starting with the deletion of N-terminal cysteine and ending with C-terminal proline, such as EP 7.0

Des-22 tyrosine calcitonin . According to the analysis of amino acid properties, acidic amino acids such as aspartic acid and glutamic acid are not easy to condense. Salmon calcitonin is a peptide impurity that lacks two amino acids and may have more types, such as C-terminal glycine threonine deficient Salmon calcitonin

2. Chiral racemic isomers

Some amino acids are prone to racemization during condensation, such as cysteine, serine, lysine, histidine, proline, arginine, and other amino acids. For example, impurity B, 9-D leucine calcitonin salmon in European Pharmacopoeia 7.0

3. Degradable impurities, such as hydrolytic impurities

Some amino acids are relatively easy to hydrolyze, such as asparagine, glutamine, and the amide structure formed by terminal proline is also easy to hydrolyze; Oxidizing impurities, impurities that are oxidized by cysteine, such as impurity D in EP 7.0; Amino acid ring opening impurity, proline ring opening, two proline in salmon calcitonin, easy to open the ring to form 5-aminovaleric acid; N-terminal acetylated impurity, such as impurity A (N-Acetyl-cys1-calcium salt) in EP 7.0

4. Recombinant Salmon Calcitonin Impurities (EP7.0)

Impurity E: Calcitonin salmon-glycine

Impurity F: 1,7-bis (3-sulfo-l-alanine)] calcitonin salmon

5.Others

 Asp salmon calcitonin

 Glu salmon calcitonin

High performance liquid chromatography (HPLC) can be used to detect impurities in salmon calcitonin and its injections, compare the impurities in products from different manufacturers, determine the source and structure of impurities using liquid chromatography mass spectrometry, and identify the structure of unknown impurities. An impurity spectrum of salmon calcitonin can be established.

Omizzur Biotech is a custom peptide synthesis company in China. Omizzur provides a series of customized synthesis services for salmon calcitonin impurities, as well as analysis reports ,certificates for HPLC, MS, COA, COO,BSE, etc. Omizzur sign a customer privacy agreement to 100% protect customer privacy . Please contact Omizzur customer services for help.