Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha H1047X mutant (PIK3CA H1047X) (PIK3CA H1047X)

The Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha H1047X mutant (PIK3CA H1047X), commonly the H1047R variant, is an oncogenic gain-of-function mutation in the kinase domain of the p110α subunit of PI3Kα, a lipid kinase that phosphorylates PIP2 to PIP3, hyperactivating downstream AKT/mTOR signaling to promote cell growth, survival, and proliferation. This mutation, the most prevalent kinase domain alteration in PIK3CA (occurring in ~30-40% of breast cancers and other solid tumors), increases catalytic activity by enhancing plasma membrane retention and reducing p85 regulatory inhibition. It drives tumor progression, confers resistance to HER2-targeted therapies like trastuzumab in HER2+ breast cancer, and is prognostic for worse outcomes in metastatic settings. Therapeutically, PIK3CA H1047X predicts higher response rates to PI3K/AKT/mTOR inhibitors compared to wild-type, with selective inhibitors like pyridopyrimidinones (e.g., compound 17) and STX-478 exploiting a cryptic allosteric pocket near the mutant Arg1047 for potent antitumor activity and tumor regressions in models like HCC1954 xenografts, minimizing wild-type inhibition. Challenges include on-target hyperglycemia from concomitant wild-type PI3Kα blockade, though mutant-selective agents aim to improve tolerability.

Other names

PI3Kα H1047X mutantPI3Kα H1047R mutantp110α H1047X mutant

Selective inhibition of mutant PI3Kα kinase activity, Inhibition of PI3K/AKT/mTOR pathway signaling, Allosteric binding to cryptic pocket near Arg1047, Disruption of activation loop and membrane binding