AMG-319

Phosphoinositide 3-kinase δ (PI3Kδ) has a key role in lymphocytes, and inhibitors that target this PI3K have been approved for treatment of B cell malignancies1–3. Although studies in mouse models of solid tumours have demonstrated that PI3Kδ inhibitors (PI3Kδi) can induce anti-tumour immunity4,5, its effect on solid tumours in humans remains unclear. Here we assessed the effects of the PI3Kδi AMG319 in human patients with head and neck cancer in a neoadjuvant, double-blind, placebo-controlled randomized phase II trial (EudraCT no. 2014-004388-20). PI3Kδ inhibition decreased the number of tumour-infiltrating regulatory T (Treg) cells and enhanced the cytotoxic potential of tumour-infiltrating T cells. At the tested doses of AMG319, immune-related adverse events (irAEs) required treatment to be discontinued in 12 out of 21 of patients treated with AMG319, suggestive of systemic effects on Treg cells. Accordingly, in mouse models, PI3Kδi decreased the number of Treg cells systemically and caused colitis. Single-cell RNA-sequencing analysis revealed a PI3Kδi-driven loss of tissue-resident colonic ST2 Treg cells, accompanied by expansion of pathogenic T helper 17 (TH17) and type 17 CD8+ T (TC17) cells, which probably contributed to toxicity; this points towards a specific mode of action for the emergence of irAEs. A modified treatment regimen with intermittent dosing of PI3Kδi in mouse models led to a significant decrease in tumour growth without inducing pathogenic T cells in colonic tissue, indicating that alternative dosing regimens might limit toxicity.

Cell-cell junctions are critical for the maintenance of cellular as well as tissue polarity and integrity. Dysfunction of airway epithelial barrier has been shown to be involved in the pathogenesis of acute lung injury (ALI). Yet the role of phosphatidylinositol 3-kinase delta (PI3Kδ) in dysregulation of airway epithelial barrier integrity in ALI has not been addressed. Mice were subjected to intratracheal instillation of lipopolysaccharide (LPS) to generate a ALI model. Two pharmacological inhibitors of PI3Kδ, IC87114 and AMG319, were respectively given to the mice. Expression of p110δ and its downstream substrate phospho-AKT (Ser473) was increased in LPS-exposed lungs. These increases were inhibited by IC87114 or AMG319. LPS led to pronounced lung injury that was accompanied by significant airway neutrophil recruitment and bronchial epithelial morphological alterations 72 h after exposure. We also found compromised expression of adherens junction protein E-cadherin and tight junction protein claudin-2 in the airway epithelial cells. Treatment with either IC87114 or AMG319 not only attenuated LPS-induced edema, lung injury and neutrophilc inflammation, reduced total protein concentration and IL-6, TNF-α secretion in BALF, but also restored epithelial E-cadherin and claudin-2 expression. In summary, our results showed that LPS can induce a delayed effect on airway epithelial barrier integrity that is mediated by PI3Kδ in a mouse model of ALI.