PIK-75

PIK-75 is a specific inhibitor of p110α isoform of PI3K with IC50 of 5.8 nM [1].

In acute myeloid leukemia cells, PIK-75 targeted the p110α isoform of PI3K, which led to a loss of connection between Bcl-xL and Bak. PIK-75 also transiently decreased Cdk7/9, leading to loss of Mcl-1 protein, and alleviation of its inhibition of pro-apoptotic Bak. The simultaneous loss of Bcl-xL and Mcl-1 led to rapid apoptosis. [2] In human monocyte-endothelial cell, PIK-75 suppressed the events of downstream signaling, including AKT phosphorylation, IKK activation, and NF-kB transcription. PIK-75 inhibited in vitro and in vivo production of TNF-α and IL-6, decreased the E-selectin, ICAM-1, and VCAM-1 expression, and blocked cell adhesion [3]. In human smooth muscle cells, PIK-75 decreased TNF-α-induced CD38 expression in asthmatic and nonasthmatic cells [4]. In pancreatic β-cells, acute treatment with PIK-75 enhanced the glucose-induced insulin secretion [5].

In vivo, PIK-75 significantly suppressed the histological abnormalities associated with dextran sulfate sodium-induced murine colitis. PIK-75 can attenuate experimental inflammation in the colon [3].

References:
[1]. Zheng Z, Amran SI, Thompson PE, Jennings IG. Isoform-selective inhibition of phosphoinositide 3-kinase: identification of a new region of nonconserved amino acids critical for p110α inhibition. Mol Pharmacol. 2011 Oct;80(4):657-64.
[2]. Thomas D, Powell JA, Vergez F, Segal DH, Nguyen NY, Baker A, Teh TC, Barry EF, Sarry JE, Lee EM, Nero TL, Jabbour AM, Pomilio G, Green BD, Manenti S, Glaser SP, Parker MW, Lopez AF, Ekert PG, Lock RB, Huang DC, Nilsson SK, Récher C, Wei AH, Guthridge MA. Targeting acute myeloid leukemia by dual inhibition of PI3K signaling and Cdk9-mediated Mcl-1 transcription. Blood. 2013 Aug 1;122(5):738-48.
[3]. Dagia NM, Agarwal G, Kamath DV, Chetrapal-Kunwar A, Gupte RD, Jadhav MG, Dadarkar SS, Trivedi J, Kulkarni-Almeida AA, Kharas F, Fonseca LC, Kumar S, Bhonde MR. A preferential p110alpha/gamma PI3K inhibitor attenuates experimental inflammation by suppressing the production of proinflammatory mediators in a NF-kappaB-dependent manner. Am J Physiol Cell Physiol. 2010 Apr;298(4):C929-41.
[4]. Jude JA, Tirumurugaan KG, Kang BN, Panettieri RA, Walseth TF, Kannan MS. Regulation of CD38 expression in human airway smooth muscle cells: role of class I phosphatidylinositol 3 kinases. Am J Respir Cell Mol Biol. 2012 Oct;47(4):427-35.
[5]. Aoyagi K, Ohara-Imaizumi M, Nishiwaki C, Nakamichi Y, Ueki K, Kadowaki T, Nagamatsu S. Acute inhibition of PI3K-PDK1-Akt pathway potentiates insulin secretion through upregulation of newcomer granule fusions in pancreatic β-cells. PLoS One. 2012;7(10):e47381.

Development of PIK-75 nanosuspension formulation with enhanced delivery efficiency and cytotoxicity for targeted anti-cancer therapy.[Pubmed:23632263]

Int J Pharm. 2013 Jun 25;450(1-2):278-89.

PIK-75 is a phosphatidylinositol 3-kinase (PI3K) inhibitor that shows selectivity toward p110-alpha over the other PI3K class Ia isoforms p110-beta and p110-delta, but it lacks solubility, stability and other kinase selectivity. The purpose of this study was to develop folate-targeted PIK-75 nanosuspension for tumor targeted delivery and to improve therapeutic efficacy in human ovarian cancer model. High pressure homogenization was used to prepare the non-targeted and targeted PIK-75 nanosuspensions which were characterized for size, zeta potential, entrapment efficiency, morphology, saturation solubility and dissolution velocity. In vitro analysis of drug uptake, cell viability and cell survival was conducted in SKOV-3 cells. Drug pharmacokinetics and pAkt expression were determined in SKOV-3 tumor bearing mice. PIK-75 nanosuspensions showed an improvement in dissolution velocity and an 11-fold increase in saturation solubility over pre-milled PIK-75. In vitro studies in SKOV-3 cells indicated a 2-fold improvement in drug uptake and 0.4-fold decrease in IC50 value of PIK-75 following treatment with targeted nanosuspension compared to non-targeted nanosuspension. The improvement in cytotoxicity was attributed to an increase in caspase 3/7 and hROS activity. In vivo studies indicated a 5-10-fold increased PIK-75 accumulation in the tumor with both the nanosuspension formulations compared to PIK-75 suspension. The targeted nanosuspension showed an enhanced downregulation of pAkt compared to non-targeted formulation system. These results illustrate the opportunity to formulate PIK-75 as a targeted nanosuspension to enhance uptake and cytotoxicity of the drug in tumor.

Suppression of CD4+ T lymphocyte activation in vitro and experimental encephalomyelitis in vivo by the phosphatidyl inositol 3-kinase inhibitor PIK-75.[Pubmed:24674679]

Int J Immunopathol Pharmacol. 2014 Jan-Mar;27(1):53-67.

Class IA phosphatidyl inositol-3 kinases (PI3-K) are important targets in cancer therapy and are essential to immune responses, particularly through costimulation by CD28 and ICOS. Thus, small PI3-K inhibitors are likely candidates to immune intervention. PIK-75 is an efficient inhibitor of the PI3-K p110alpha catalytic subunits that suppresses tumor growth, and its effects on immune and autoimmune responses should be studied. Here, we describe the effect of PIK-75 on different immune parameters in vitro and in vivo. PIK-75 at concentrations commonly used in vitro (≥0.1 μM) inhibited T and B cell activation by Concanavalin A and LPS, respectively, and survival of non-stimulated spleen cells. In naive CD4+ T lymphocytes, PIK-75 induced apoptosis of resting or activated cells that was prevented by caspase inhibitors. At low nanomolar concentrations (≤10 nM), PIK-75 inhibited naive CD4+ T cell proliferation, and IL-2 and IFN-gamma production induced by anti-CD3 plus anti-CD28. In activated CD4+ T blasts costimulated by ICOS, PIK-75 (less than 10 nM) inhibited IFN-gamma, IL-17A, or IL-21 secretion. Furthermore, PIK-75 (20 mg/kg p.o.) suppressed clinical symptoms in ongoing experimental autoimmune encephalomyelitis (EAE) and inhibited MOG-specific responses in vitro. Thus, PIK-75 is an efficient suppressor of EAE, modulating lymphocyte function and survival.

Inhibition of NRF2 by PIK-75 augments sensitivity of pancreatic cancer cells to gemcitabine.[Pubmed:24366069]

Int J Oncol. 2014 Mar;44(3):959-69.

We describe the potential benefit of PIK-75 in combination of gemcitabine to treat pancreatic cancer in a preclinical mouse model. The effect of PIK-75 on the level and activity of NRF2 was characterized using various assays including reporter gene, quantitative PCR, DNA-binding and western blot analyses. Additionally, the combinatorial effect of PIK-75 and gemcitabine was evaluated in human pancreatic cancer cell lines and a xenograft model. PIK-75 reduced NRF2 protein levels and activity to regulate its target gene expression through proteasome-mediated degradation of NRF2 in human pancreatic cancer cell lines. PIK-75 also reduced the gemcitabine-induced NRF2 levels and the expression of its downstream target MRP5. Co-treatment of PIK-75 augmented the antitumor effect of gemcitabine both in vitro and in vivo. Our present study provides a strong mechanistic rationale to evaluate NRF2 targeting agents in combination with gemcitabine to treat pancreatic cancers.

The inhibitory effect of PIK-75 on inflammatory mediator response induced by hydrogen peroxide in feline esophageal epithelial cells.[Pubmed:25276052]

Mediators Inflamm. 2014;2014:178049.

Isoform-selective inhibitors of phosphoinositide 3-kinase (PI3K) activation have an anti-inflammatory effect by reducing proinflammatory cytokines. Cultured feline esophageal epithelial cells (EEC) of passages 3~4 were treated with hydrogen peroxide and PIK-75. The cell viability was measured by a MTT incorporation assay. The distribution of PI3K isoforms, p-Akt, IL-1beta, and IL-8 was inferred from Western blots. The release of IL-6 was determined by ELISA. The cell morphology was not considerably different from nontreated cells if the cells were pretreated with PIK-75 and treated with 300 muM hydrogen peroxide. The density of p110alpha of PI3K was increased, but that of other types was not affected after the treatment with hydrogen peroxide. The density of p-Akt, when the cells were exposed to PIK-75 and hydrogen peroxide, was diminished dose dependently more than that of hydrogen peroxide treatment only. The decrease of p-Akt showed an inhibition of PI3K by PIK-75. PIK-75 dose dependently reduced the expression of IL-1beta, IL-8, and the level of IL-6 compared with hydrogen peroxide treatment only. These results suggest evidence that p110alpha mediates esophageal inflammation and that PIK-75 has an anti-inflammatory effect by reducing proinflammatory cytokines on feline esophageal epithelial cultured cells.

PIK-75 hydrochloride is a reversible DNA-PK and p110α-selective inhibitor, which inhibits DNA-PK, p110α and p110γ with IC50s of 2, 5.8 and 76 nM, respectively. PIK-75 hydrochloride inhibits p110α >200-fold more potently than p110β (IC50=1.3 μM). PIK-75 hydrochloride induces apoptosis.

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