In view of the poor curative effect of the macromolecule PRLR, the need to be administered byinjection, the relatively high production cost, andthe inability to cross the blood-brain barrier to treatbreast cancer metastasis, small molecules have greater advantages as therapeutic agents in breast cancer,such as oral administration, low immunogenicity,penetration of the blood-brain barrier, ease of structural optimization through medicinal chemistry, andlow production cost (70). The Borcherding DC teamused a high-throughput screening (HTS) methodof 51,000 small molecules to find a small moleculeinhibitor SMI-6 that can bind to the extracellulardomain (ECD) of PRLR, which can eliminate PRLinduced breast cancer cell invasion and malignantlymphocyte proliferation, has the effect of reducingthe vitality of a variety of breast cancer cell types,and has no obvious toxicity in vivo or in vitro. It isexpected to become an effective treatment for breastcancer patients (71). New drugs targeting PRLRare used as potential therapeutics for breast cancer,and their efficacy and safety have yet to be furtherevaluated in clinical trials