a, Native gel of cetuximab (ctx)-based LYTACs. b, Levels of EGFR in HeLa cells treated with 100 nM ctx (lane 3), ctx-GalNAc (lane 4), ctx-M6Pnlong (lane 5) or ctx-M6Pnshort (lane 6) for 24 h in complete growth medium. EGF stimulation is a positive control for EGFR downregulation. c, Synthesis of linker-swapped Ab-2. Ctx was labelled with NHS-PEG4-N3, then incubated with BCN-functionalized poly(M6Pn)short for 3 days at room temperature. Reaction progress was monitored by native gel electrophoresis and visualized with Coomassie stain. d, Native gel of ctx-Fab-based LYTACs. e, EGFR levels in dCas9-KRAB HeLa cells transfected with non-targeting sgRNA against GAL4 after incubation with 100 nM, 10 nM,1 nM, or 0.1 nM conjugates for 36 h in complete growth medium. f, EGFR levels in dCas9-KRAB HeLa cells transfected with non-targeting GAL4 sgRNA incubated with Ab-2 or ctx for the indicated time. g, Quantification of LYTAC or ctx-mediated EGFR degradation in dCas9-KRAB HeLa expressing GAL4 sgRNA over time as read out by western blot relative to untreated cells. h, Levels of pEGFR in dCas9-KRAB HeLa cells expressing an sgRNA targeting IGF2R after 24 h incubation with 10 nM ctx or Ab-2, then incubation with EGF for 10 or 60 min. Data are representative of two (a–e, h) or three (f) independent experiments. For g, data are mean ± s.d. of three independent experiments, one of which is shown in f. Per cent control was calculated by densitometry and normalized to loading control (b, e, f).