Chemical denaturation as a tool in the formulation optimization of biologics

• Isothermal chemical denaturation reliably determines protein stability.
• Chemical denaturation is often reversible enabling rigorous thermodynamic analysis.
• New developments enable automated, accurate and reproducible stability studies.
• Chemical denaturation is an orthogonal method to complement thermal denaturation.
• Virtually any formulation or processing condition can be evaluated for stability.

Biologics have become the fastest growing segment in the pharmaceutical industry. As is the case with all proteins, biologics are susceptible to denature or to aggregate; conditions that, if present, preclude their use as pharmaceuticals. Identifying the solvent conditions that maximize their structural stability is crucial during development. Since the structural stability of a protein is susceptible to different chemical and physical conditions, the use of several complementary techniques can be expected to provide the best answers. Stability measurements that rely on temperature or chemical [urea or guanidine hydrochloride (GuHCl)] denaturation have been the preferred ones in research laboratories and together provide a thorough evaluation of protein stability. In this review, we will discuss chemical denaturation as a tool in the optimization of formulation conditions for biologics, and how chemical denaturation complements the role of thermal denaturation for this purpose.