Methods of generating conditionally active proteins that target senescent cells and which are conditionally active in an extracellular environment of a senescent cell. The methods include discovery methods using libraries of evolved proteins and assays employing physiological concentrations of components of bodily fluids. Also disclosed are conditionally active proteins for killing or removing senescent cells, pharmaceutical compositions employing these conditionally active proteins and methods for treatment of age-related diseases, conditions or disorders using same. The conditionally active proteins may be further evolved, conjugated to other molecules, masked, reduced in activity by attaching a cleavable moiety.
