Phosphoinositide-dependent kinase 1 (PDK1) in cancer: molecular insights and therapeutic strategies.

3-Phosphoinositide-dependent protein kinase 1 (PDK1) has emerged as one of the most strategically positioned and paradoxically underexploited regulators within Pl3K. It is the main controller of the AGC kinase family, which includes AKT, S6K, SGK, and PKC isoforms. PDK1 is a central signaling hub downstream of the PI3K signaling pathway. It controls key cellular processes such as proliferation, metabolism, and survival by orchestrating activation-loop phosphorylation. Aberrant activation of PDK1 facilitates tumor initiation, progression, and therapeutic resistance in various cancer types. Scientists have not been able to develop small-molecule inhibitors that are as selective and work as well in the clinic as they do for other kinases. This is mostly because the ATP-binding site is highly conserved, while PDK1's structure is very dynamic. This review summarizes recent progress in comprehending PDK1's structure, regulation, and its function in oncogenic (cancer-promoting) signaling. We discuss medicinal chemistry strategies like ATP-competitive, allosteric, and dual-site inhibition, as well as rational polypharmacology and combination approaches to overcome pathway redundancy. We also discuss how far we have come in identifying biomarkers to help us select patients and monitor their responses. These efforts make PDK1 a promising but underused target for therapy. New opportunities are emerging to use it for diseases beyond cancer, such as inflammatory, metabolic, and neurological diseases.