PF-4708671 is a selective inhibitor of p70 ribosomal S6 kinase (S6K1), a key enzyme involved in cell growth, proliferation, and survival pathways. It is widely used in research to study the mTOR (mammalian target of rapamycin) signaling pathway, which plays a central role in regulating protein synthesis and cellular metabolism. By inhibiting S6K1, PF-4708671 helps scientists investigate the downstream effects of mTOR activity in processes such as insulin signaling, cancer progression, and aging. In cancer research, PF-4708671 has been used to explore how blocking S6K1 affects tumor cell growth and survival, particularly in cancers where the mTOR pathway is hyperactive. It has shown potential in reducing cell proliferation and enhancing the effects of other anticancer agents in preclinical models. Additionally, it is used to study metabolic diseases, as S6K1 inhibition can influence glucose homeostasis and insulin sensitivity. Due to its ability to cross cell membranes effectively, PF-4708671 is valuable in cellular and animal studies, providing insights into therapeutic strategies targeting the mTOR/S6K1 axis. However, it remains a research compound and is not used clinically.