In 2019, Zhao et al. exploited the CRBN ligand and palbociclib (a CDK4/6 inhibitor) to synthesis the PROTAC Pal-pom that degraded CDK4/6 with DC50 values of 20–50 nM, thus preventing Rb phosphorylation and inducing cell cycle arrest in triple negative breast cancer (TNBC) cells [104]. The gene discussed is CDK4; the disease is triple-negative breast carcinoma.