Target intelligence / Profile preview

Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta[p110δ][5][7] (PI3Kδ[p110δ][5][7])

Target: PI3Kδ[p110δ][5][7]
Molecular classification: Enzyme[7][3], Lipid kinase[3][7], Class I phosphoinositide 3-kinase (Class IA catalytic subunit)[3][7]

Overview

Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta (PI3Kδ; p110δ) is the leukocyte-enriched catalytic subunit of Class IA phosphoinositide 3-kinase that partners with p85-type regulatory subunits to generate PIP3 from PI(4,5)P2 at the plasma membrane, activating downstream signaling via Akt and other PH domain proteins to regulate immune cell function and survival[5][3][7]. It is encoded by the PIK3CD gene and is a validated therapeutic target with multiple approved or investigational small-molecule ATP-competitive inhibitors used particularly in B-cell malignancies and inflammatory conditions[5][7].

Other names: p110δ[5][7]Phosphoinositide 3-kinase delta[5]PI3K delta isoform[5]PIK3CD (gene name)[5][3]Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta isoform[5]

Mechanism of action

Competitive inhibition of the ATP-binding site of PI3Kδ lipid kinase, reducing conversion of PI(4,5)P2 to PIP3 and downstream PI3K–Akt signaling[3][7] Isoform-selective targeting of the p110δ catalytic subunit within Class IA PI3Ks[7]

Biological functions

Signal transduction via production of phosphatidylinositol (3,4,5)-trisphosphate (PIP3)[3][7]Immune response regulation in leukocytes (B cells, T cells, mast cells, neutrophils)[5]Cell proliferation and survival signaling through Akt/PKB and PH domain–containing proteins[5][3]Membrane recruitment and activation downstream of tyrosine kinase–coupled receptors via p85 regulatory subunits[5]

Disease associations

Cancer (PI3K pathway dysregulation; p110δ implicated, especially in hematologic malignancies)[7][3]Inflammation[5][7]Autoimmunity[5]Infection susceptibility when inhibited (immunosuppression)[7]Transplant rejection (as a target for prevention)[5]

Safety considerations

Immune-related adverse events due to on-target immunosuppression (e.g., infections)[7]Inflammatory/autoimmune toxicities reported with PI3Kδ inhibitors (colitis, hepatotoxicity), requiring monitoring in clinical use[7]Class effects of PI3K inhibitors including hyperglycemia and rash may occur depending on selectivity profile[7]

Interacting drugs

Idelalisib (PI3Kδ inhibitor)[7]

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Biomarkers

PIK3CD expression enriched in leukocytes as a contextual biomarker for target engagement[5][3]Decrease in PIP3/Akt phosphorylation (p-Akt) as pharmacodynamic readouts of PI3K pathway inhibition[3][7]Hematologic malignancy phenotypes reliant on PI3Kδ signaling (e.g., B-cell receptor pathway activity) used to select patients for PI3Kδ inhibitors[7]

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