The power of genetics in understanding biological pathways is based on the idea that a chromosomal mutation causes a specific, identifiable change in a cell. In contrast, biochemical or cell biological approaches to protein function are often nonspecific when done in vivo due to broad effects on cellular function resulting from secondary molecular interactions, or are not physiologically relevant when done in vitro.

To address the issue of specificity without genetic engineering, Xerion Pharmaceuticals GmbH is developing a cell biological protein inactivation technology called CALI for protein characterization and functional analysis, target validation and drug discovery. It allows protein inactivation without genetic engineering to permit cell culture and animal model research that is both relevant and target-specific.