Peptide drug is a kind of peptide biologic drug which can be used for the prevention, treatment and diagnosis of diseases. Its preparation methods mainly include chemical peptide synthesis, separation and purification, and genetic engineering, among which chemical peptide synthesis is the main preparation way of peptide drug. Although peptide drugs can be obtained by isolation and purification from organisms, the content of natural peptide molecules is small, which cannot fully meet the needs of clinical application. Chemical peptide synthesis is achieved through the chemical reaction of amino acid condensation step by step, generally from the carboxyl end to the amino end, the repeated process of adding amino acids one by one.

Peptide drugs mainly include peptide vaccines, anti-tumor peptides, antiviral peptides, peptide oriented drugs, cytokine mimics peptides, antibacterial peptides, diagnostic peptides and other small medicinal peptides. Compared with common organic small molecule drugs, peptide drugs have prominent characteristics such as strong biological activity, small dosage, low toxicity and significant curative effect. However, the half-life of peptide drugs is generally short, unstable, and easy to be rapidly degraded in vivo.

Compared with protein-based macromolecular drugs, except for peptide vaccines, peptide drugs have relatively small immunogenicity, lower dosage, higher unit activity, easy synthesis, modification and optimization, high purity, controllable quality, and can quickly determine the medicinal value.

1.peptide vaccine

Peptide vaccine is a vaccine prepared by chemical peptide synthesis technology according to the amino acid sequence of a certain epitope known or predicted in the antigen gene of the pathogen. Peptide vaccine is an important direction of vaccine research at present. Peptide vaccines against HIV and hepatitis C virus have been developed. Traditional vaccines are usually prepared in two ways, one is a weakened vaccine that induces immunity but does not cause disease. Because the peptide vaccine is completely synthetic, there is no problem of virulence recovery or inactivation. In particular, some microbial pathogens have not been able to obtain sufficient amounts of antigens through in vitro culture. Some can be cultured in vitro, but these pathogens have potential pathogenicity and immunopathological effects, which involve safety and efficacy issues. Peptides, as immunogens that cause the formation of effector cell immune response in vivo, will become a new type of vaccine.

2. Antitumor peptides

Peptide drugs have attracted attention in the development of anti-tumor drugs due to their targeting, safety and specificity. Different peptide drugs have various mechanisms of action. It can inhibit the proliferation of tumor cells and promote the apoptosis of tumor cells to achieve direct anti-tumor effects, and can also achieve indirect anti-tumor effects by enhancing and stimulating the immune response to tumor cells and inhibiting tumor angiogenesis. Moreover, the diversity and specificity of its mechanism of action can also realize the transformation and fusion of peptides, and realize the efficient, targeted and specific anti-tumor effects of peptides.

3. Peptide-directed drugs

The binding ability of peptides and cytotoxins or cytokines are fused to direct them to the lesion site, play a therapeutic role, while reducing toxic side effects. Many toxins (such as pseudomonas aeruginosa exotoxins) and cytokines (such as interleukin series) are known to be highly toxic to tumor cells, but they can also damage normal cells when used in humans for a long time or in large quantities. By fusing these active factors with peptides that can bind specifically to tumor cells, these active factors can be specifically concentrated in the tumor site, which can greatly reduce the concentration of toxins and cytokines and reduce their side effects.

4. Cytokine mimicking peptides

It refers to the selection of peptides from peptide libraries that can specifically bind to cytokine receptors and have cytokine activity. The sequence of these simulated peptides is generally different from the amino acid sequence of cytokines. Hematopoietic cytokines such as erythropoietin (EPO) and thrombopoietin (TPO) regulate self-renewal, proliferation, differentiation, maturation and programmed death of hematopoietic cells through specific binding to their receptors. In recent years, phage display library and other technologies have been used to screen out the simulated peptides and non-peptide small molecules similar to the activity of cytokines. In vitro and animal experiments have confirmed that they have similar functions to cytokines in stimulating hematopoietic biology. This lays a solid foundation for further exploring the mechanism of action of cytokines and screening out ideal small molecule peptides and non-peptide drugs that mimic the function of other cytokines.

5. antibacterial sexually active peptide

More than 100 kinds of peptide molecules with antibacterial activity have been screened from insects and animals. Antimicrobial peptides have the characteristics of broad antibacterial spectrum, strong thermal stability, small molecular weight and low immunogenicity. Their bactericidal mechanism is unique, and pathogens are not easy to develop drug resistance, which is expected to be developed into a new generation of peptide antibiotics. However, some antimicrobial peptides are characterized by unstable spatial structure and hemolytic activity, which limit their clinical application. Therefore, the design or modification of natural antibacterial peptides can eliminate their hemolytic activity on the basis of improving antibacterial activity, and promote the application of antibacterial peptides in medicine, which is expected to develop into new antibacterial drugs and provide a new way to solve the problem of increasing resistance of pathogenic bacteria to traditional antibiotics.

6. Diagnostic peptides

Peptides obtained by screening from pathogenic bodies or peptide libraries are used as diagnostic reagents to detect the presence of antibodies of pathogenic microorganisms, parasites, etc. Including the detection of antibodies to hepatitis virus, HIV, rheumatoid disease, etc. The main use of peptides in diagnostic reagents is used as antigens to detect antibodies against viruses, cells, mycoplasma, spirochaeta and other microorganisms, as well as cysticercus, Trypanosoma and other parasites. peptide antigen is more specific than natural microbial or parasite protein antigen and is easy to prepare. Therefore, the assembled detection reagent has a low false negative rate and background reaction for antibody detection, which is easy for clinical application.

The common types of peptide drugs mainly include the above several types. Currently, peptide drugs extracted from animal tissues will be phased out gradually, and chemical peptide synthesis and gene recombination will become complementary polypeptide drug production methods in a long time. At the time of rapid development of synthetic drugs of chemical peptides, gene recombination expression to produce peptide drugs has attracted much attention in the industry. Compared with chemical peptide synthesis, gene recombination is more suitable for the preparation of long peptide. And as technology improves, the cost of producing peptide drugs through genetic reprogramming is falling.