YZ-836P is a Protein arginine methyltransferase 5 (PRMT5) targeting agent. YZ-836P promotes ubiquitination and proteasomal degradation of PRMT5 in a cereblon (CRBN)-dependent manner, which in turn reduces levels of its downstream target KLF5. YZ-836P induces G1 phase cell cycle arrest in triple-negative breast cancer cells. YZ-836P induces apoptosis in triple-negative breast cancer cells. YZ-836P exerts cytotoxic effects on triple-negative breast cancer cells. YZ-836P inhibits the growth of triple-negative breast cancer patient-derived organoids. YZ-836P inhibits the growth of triple-negative breast cancer xenografts in nude mice. YZ-836P can be used for the research of triple-negative breast cancer.