PTC-209 HBr is primarily used in research settings to study cancer biology, particularly in the context of targeting and inhibiting the BMI-1 protein. BMI-1 is a key regulatory protein involved in the self-renewal of cancer stem cells, which are often resistant to conventional therapies. By inhibiting BMI-1, PTC-209 HBr helps researchers explore potential strategies to disrupt cancer stem cell proliferation and survival. This makes it a valuable tool in preclinical studies aimed at developing novel cancer treatments, especially for cancers with poor prognosis or high relapse rates, such as certain types of leukemia, breast cancer, and glioblastoma. Its application extends to understanding the molecular mechanisms underlying tumorigenesis and drug resistance.