BSJ-03-123 is a potent, CDK6-selective small-molecule degrader.

BSJ-03-123 induced rapid, dose-dependent ternary complex formation with CDK6 and CRBN, but not with CDK4 and CRBN. Ternary complex formation was prevented by blocking binding sites on CDK6 or CRBN via pretreatment with palbo or lenalidomide.

4x10^6 MV4-11 CRBN-/- cells were treated for 3 h with 20 μM palbociclib, BSJ-03-123 or vehicle. 1x10^6 cells were spun down at 500 x g for 5 min, and the supernatant removed. Pellets were incubated at 46, 49, 52 or 55°C for 3 min followed by 3 min incubation at room temperature. 30 μl of lysis buffer (20 mM Tris-HCl pH 8.0, 120 mM NaCl, 0.5% NP-40, protease inhibitors) were added and cells lysed by 3 rounds of snap freezing and thawing. Denatured proteins were removed by 20 min centrifugation at 14.000 x g at 4°C and supernatants analyzed by Western Blotting.