Class I Phosphoinositide 3-kinases and Mechanistic Target of Rapamycin (Class I PI3K/mTOR)

Class I Phosphoinositide 3-kinases (PI3Ks) and the Mechanistic Target of Rapamycin (mTOR) are central nodes in the PI3K/AKT/mTOR signaling pathway, which governs essential cellular functions such as growth, proliferation, metabolism, and survival [UniProt P42336, P42345]. Class I PI3Ks are lipid kinases that catalyze the production of phosphatidylinositol-3,4,5-trisphosphate (PIP3), while mTOR is a serine/threonine kinase acting through two complexes, mTORC1 and mTORC2, to regulate protein synthesis and autophagy [PubMed: 30634440]. This pathway is frequently hyperactivated in various human cancers due to mutations in PIK3CA or loss of the tumor suppressor PTEN, making it a high-priority therapeutic target [PubMed: 29735994]. Dual PI3K/mTOR inhibitors were designed to simultaneously block both nodes, preventing the compensatory feedback loops—such as mTORC2-mediated AKT activation—that often limit the efficacy of rapalogs or isoform-specific PI3K inhibitors [PubMed: 24352796]. Despite their potent anti-tumor activity in preclinical models, clinical development has been hindered by a narrow therapeutic window and significant toxicities, including hyperglycemia and gastrointestinal distress, which arise from the pathway's fundamental role in systemic glucose homeostasis [PubMed: 28671670].

Other names

PI3K/mTOR pathwayPhosphatidylinositol 3-kinase/mammalian target of rapamycinPI3K-mTOR dual targetPI3K/AKT/mTOR axis

Simultaneous competitive inhibition of the ATP-binding sites of Class I PI3K catalytic subunits (p110 alpha, beta, gamma, delta) and the mTOR kinase domain, thereby suppressing the PI3K/AKT/mTOR signaling cascade [PubMed: 24352796].