a, Schematic for sublibrary targeted screen using anti-CD22-maytansine (noncleavable), anti-CD22-VC-maytansine (cleavable) and free maytansine. The targeted sublibrary was designed, synthesized and lentivirally installed into Cas9-expressing Ramos cells. The Ramos cells were either treated with (1) anti-CD22-maytansine, (2) anti-CD22-VC-maytansine or (3) free maytansine or left untreated. The resulting populations were subjected to deep sequencing and analysis. The screens were performed in duplicate and at 1,000× coverage. b, Comparative analysis of results from anti-CD22-maytansine (noncleavable) and free maytansine sublibrary screens. Signed casTLE scores are reported. c, Comparative analysis of results from anti-CD22-maytansine (noncleavable) and anti-CD22-VC-maytansine (cleavable) sublibrary screens. Signed casTLE scores are reported.