Protein solid formulations

Not all observations are summarized by laws. There are many properties of matter (such as superconductivity, the ability of a few cold solids to conduct electricity without any resistance) that are currently at the forefront of research but are not described by grand laws that embrace hundreds of different compounds. A major current puzzle, which might be resolved in the future either hy finding the appropriate law or by detailed individual computation, is what determines the shapes of big protein molecules. Formulating a law is just one way, not the only way, of summarizing data. 

The Maillard reaction is likely to take on additional significance with the introduction of many new protein and peptide pharmaceuticals. For example, Tarelli et al. have demonstrated that lysine vasopressin undergoes rapid glycation in the presence of reducing sugars in both aqueous and solid formulations and that the N-terminal adduct can form rapidly even at — 20°C [52], A textbook that deals with the consequences for the chemical and life sciences of the Maillard reaction has been published [53]. 

To work around this concentration limitation, formulation scientists often use a solid-state formulation as a means to achieving a higher protein concentration for the final drug product. By reconstituting the solid formulation with less water than was used to initially formulate the drug, one gets an increased protein concentration in the reconstituted product, as depicted in Fig. 1. It is important for the formulation scientist to remember that, in addition to the protein, the excipients in the formulation are also increased in concentration when the solid formulation is reconstituted to a lower final volume. Care should be taken to maintain a suitable final product osmolality for injection. 

Moisture was known to increase the mobility of the surface groups of protein as measured by solid-state nuclear magnetic resonance spectroscopy The distribution of water between the protein and the excipients in a freeze-dried powder depends on the crystalline or amorphous nature of the excipients. For example, if a protein is formulated with an amorphous excipient and stored in a sealed container, water would distribute according to the water affinity of the protein and excipients.When the amorphous excipient crystallizes (e.g., because of elevated temperatures), it will expel its sorbed water, which may cause stability problems in the protein. ... 

Since the administration routes are mainly parenteral, the formulation has to be injectable. An injectable formulation requires specific excipients, ways of preparation and formulation types liquid, suspension, or solid formulations. In the development of protein drugs, various formulation principles are used. In Table 5, examples of some of the formulation principles are given. 

The usefulness of NMR in such analysis is because the proton spin-relaxation time constants are different for different components, such as water, liquid fat and solid fat. For example, the signal from solid fat is found to decay rapidly while the liquid signals decay much slower. This phenomenon is the basis for an NMR technique to determine the solid fat content [20], However, as the relaxation time constant of water, for example, could depend on its local environment, such as protein concentration, it may overlap with that of oil and other components. As a result, it could be difficult to formulate a robust and universal relaxation analysis. It... 

In addition to the additives used in a formulation to help stabilize the protein to freezing, the residual moisture content of the lyophilized powder needs to be considered. Not only is moisture capable of affecting the physicochemical stability of the protein itself, equally important is the ability of moisture to affect the Tg of the formulation. Water acts as a plasticizer and depresses the Tg of amorphous solids [124,137,138]. During primary drying, as water is gradually removed from the product, the Tg increases accordingly. The duration and temperature of the secondary drying step of the lyophilization process determines how much moisture remains bound to the powder. Usually lower residual moisture in the finished biopharmaceutical product leads to enhanced stability. Typically, moisture content in lyophilized formulations should not exceed 2% [139]. The optimal moisture level for maximum stability of a particular product must be demonstrated on a case-by-case basis. 

Baked goods are the oldest known compounded foods made by mankind. Each ingredient is selected for one or more specific purposes based on contribution to functionality and compatibility, and on relative cost. Bakery products formulators are receptive to new ideas, and vegetable proteins (primarily flours and concentrates) have been well-accepted when they show a cost advantage, for example, soy flours as replacements for dried nonfat milk solids and dried eggs. 

Soy flours and concentrates are used in compounded breakfast cereals, primarily for improving total protein content and PER. In the absence of dry nonfat milk solids, glucose is often included in bakery products formulations to impart a toasted brown color. Most... 

The principles of enzyme immobilization on solid phases and the requirements for such solid phases are in general the same as those applied for sorbents and protein ligands used in affinity chromatography. Some time ago the main requirements for the ideal matrix were formulated as follows [84] ... 

There are no published studies which examine the significance of pH shifts on quality attributes of freeze-dried formulations of small molecules. However, Costantino et al. (14) reported that lyophilized organic compounds containing protein functional groups (amino-, carboxylic-, and phenolic-) exhibit pH memory that is, the ionization state of the solid, as reflected by the FTIR spectrum, is similar to that of the aqueous solution from which the compound was freeze dried. 

Of course, it is common (and often desireable) to have both amorphous and crystalline phases present in a freeze-dried formulation. This is particularly relevant to freeze-dried proteins, where the lyoprotectant is present in the amorphous state, and another component, such as glycine or mannitol, is present as a crystalline solid in order to impart mechanical integrity and pharmaceutical elegance to the lyophilized solid. 

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