To gain a global view on the impact of the collateral activity on protein expression levels, mass spectrometry was used for proteomics analysis of HEK 293T cells when PspCas13b was co-expressed with non-targeted (NT) crRNA or targeting (T) crRNA, which targets the BCR-ABL1 mRNA breakpoint. There was no evidence of off-target protein degradation by T crRNA compared to the non-targeting crRNA. The only significantly repressed proteins were the target BCR-ABL1 p190 (81% reduction) and eGFP (89% reduction) that are encoded on the same mRNA expression construct and encoded mRNA. Catalytic dead Cas13 (dCas13) and crRNA only were used as negative control.