The development of biological drugs for cancer treatment often requires formulations that must be lyophilized to produce stable products that can be stored and reconstituted. Control of the residual moisture content in the freeze-dried cake is critical for storage stability. For many drugs the residual moisture level is <1%, but for some protein-based drugs drying the product to this level results in reduced conformational stability and loss of product quality and potency. Despite the importance of the residual moisture level there is currently no on line method for determining the process endpoint.
