| With the development of recombinant DNA and peptide synthesize technology, and advantage in analytical separation technology, more and more proteins and peptides, such as enzyme, activators and inhibitors, poly- and monoclonal antibodies, and various vaccines, are used as pharmaceuticals in clinic. In comparison with small chemical drugs, protein and peptide pharmaceuticals have high specificity and activity at relatively low concentrations. These features have made them indispensable in combating human diseases. However, one of the most challenging tasks remains in the development of the protein and peptide pharmaceuticals: dealing with physical and chemical instabilitiey. Instability is one of the major reasons why protein and peptide pharmaceuticals are administered traditionally through injection rather than taken orally like most small chemical drugs. They usually have to be stored under cold conditions or even freeze-dried to a solid form to achieve an acceptable shelf life. Furthermore, applying of the free-dried has the shortages itself: 1. The procedure usually leads to decrease activity of some proteins and peptides. 2. During the dissolve, some incorrect manipulation method,shaking and shearing for example, can make proteins and peptides denaturalized. 3. The cost of the pharmaceuticals will increase with long-time free-dried procedure. Obviously, It seemed that the better way is to discovery a long shelf life aqueous formulation for them.Triptorelin (MW=1311.5), synthesized by solid-phase method, is a kind of decapeptide analogs of gonadotropin-releasing hormone (GnRH), and its pharmacology function is similar to GnRH, except for longer half-life. Octreotide can also be synthesized by solid-phase method, and its molecular weight is 1019.3 dalton. It is one of the octapeptide analog of somatostatin (SS), and has higher activity and longer half-life than SS nevertheless. In therapeutic aspects , they have the same effect. Due to their exact curative effect, triptorelin and octreotide are used widely in clinic. But like the situation of other proteins and peptides in aqueous formulation, they cause degradation product during storage and conveyance before it is injected to the patients, especially in high temperature. In this paper, we built a aqueous formulation for each peptide, which has long storage time relatively, by the high performance liquid chromatography (HPLC) and the liquid chromatography-mass spectrum (LC-MS) method. Furthermore, we found the possible degradation mechanism of triptorelin and octreotide in aqueous formulation. Our research work including: 1. Investigation on the relationship between the stability of the peptides and the factors, such as pHs, various buffers species at different concentration, ionic strength, several additives.2. Base on the results above, the aqueous formulation was optimized by long-time testing.3. The degradation products of triptorelin and octreotide was characterized and the possible degradation mechanism was evaluated.All the data shows that:1. The curve based on relationship between the pH(2.2-8.0) and the sample purity takes on "V" shape. The maximum stability of triptorelin and octreotide was showed to be at an approximate pH of 5.0 and 4.0 respectively. Low concentration(20mM) of the acetate buffer, the tartrate buffer, the sodium bicarbonate/ lactic acid buffer seemed to be helpful to maintain the stability of triptorelin; and low concentration(20mM) of the succinate buffer, the tartrate buffer, the sodium bicarbonate/ lactic acid buffer seemed to be helpful to maintain the stability of octreotide. Particularly, the concentration of the acetate buffer has no different affect on the stability of triptorelin and octreotide. The ionic strength and the additive has no significant influence on the stability of the peptides.2. The maximum stability aqueous formulation of triptorelin consists of the sodium bicarbonate/ lactic acid buffer(20mM, pH5.0) and 0.9% NaCl, and its T90% is 24, 16, 6, 7 months und... |
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