Beyond Freeze-Drying - Freeze-drying of Pharmaceuticals and Biopharmaceuticals - page 176

Figure 3 T g /time profile for a semi-dry PHC (polyhydroxy compound) product being
dried in a vial under isothermal conditions (318 K)
into the region of instability are permitted, either by a rise in the
temperature or water sorption.
Contrary to conventional wisdom, the employment of ambient or
elevated processing temperatures to remove water does not necessarily
inactivate bioproducts, provided that care is taken in the design of
appropriate formulations. The method has been successfully applied to
the ambient temperature stabilisation of a wide range of formulated
protein preparations.
13.3 Evaporative Drying: The Current State
Ambient temperature-stable DNA-modifying enzymes (restriction en-
zymes) that conventionally had to be shipped and stored in concentrated
glycerol solution at -20 1 C were produced in a shelf-stable format by the
new evaporation technology and became available commercially. 160 An
example in Figure 4 shows that such sensitive enzymes, dried and stored
for extended periods, compare well with their freshly prepared counter-
parts. The technology was later applied to the dry-state stabilisation of
microbial cultures for the dairy industry. Potentially, the most successful
application of protein stabilisation has been the formulated insulin
product Exubera, a spray-dried preparation, designed for delivery for
inhalation; it was approved by the FDA. and the European Union in
early 2006, some 15 years after the filing of the US patent, 161 for the
treatment of Types 1 and 2 diabetes. Exubera combines the advantages
of a shelf-stable product, even at tropical temperatures, with the re-
placement of delivery by injection.