Biopharmaceuticals are one of the best-selling groups of drugs and the number of new drug applications is in incline. Biologics are a very heterogeneous group that also encompasses therapeutic proteins, of which the most common are antibodies. For formulations with the latter, a trend of increasing concentrations, often exceeding 100 mg/ml, has been observed in recent years. At high concentrations, proteins have an even greater tendency to denature and aggregate. To prevent these processes, surfactants, especially polysorbates PS20 or PS80, are added to protein solutions in more than 80% of formulations. The latter are non-ionic surfactants that, among other things, effectively prevent the denaturation of proteins or. their aggregation. They are used in a wide range of concentrations, in most cases ranging from 0.01 mg/ml to 1.00 mg/ml. Their high HLB and low CMC contribute to this. On the other hand, PS20 and PS80 also have disadvantages, as they are both susceptible to oxidation and hydrolysis. A major problem is the hydrolysis of the ester bond, which can be enzymatically or non-enzymatically catalyzed. The products of hydrolysis lose their amphiphilic properties, which leads to colloidal instability or are the products poorly soluble and aggregate (e.g. fatty acids).
In order to increase the stability of PS, we prepared four analogs of PS20 and PS80 in the master's thesis, replacing the ester group with a more chemically stable carbamate. In the first phase of the experimental work, we developed appropriate reaction conditions and isolation procedure, that allowed us to obtain un-esterified POE sorbitan in high yield and purity from commercially available PS20. In the second phase corresponding isocyanate was reacted with un-esterified POE sorbitan to produce carbamate. Commercially available dodecyl and octadecyl isocyanate were used, however we also prepared an oleylamine isocyanate and a mixture of isocyanates from corresponding amines. CMC was determined for carbamate products and HLB values were calculated, thus proving the surface-active properties that are crucial for system stabilization. In the end, we tried to compare their chemical stability to PS20 and PS80. We could not directly prove this, although our experiments indicated this. This research paves the way for new potential polysorbate carbamates to stabilize therapeutic proteins.
|
