Abstract: Described herein are embodiments of methods to rationally design CRISPR-Cas system-based therapeutics and therapies based on expression of a DNA-damage response signature in a cell. In some embodiments, the methods include screening a set of CRISPR-Cas systems by expressing each CRISPR-Cas system in a test cell population and modifying one or more target sequences in the test cell population; screening in the test cell population for each CRISPR-Cas system and expression of a DNA-damage response signature; and selecting one or more CRISPR-Cas systems that do not result in expression of a DNA-damage response signature.