Selective Phosphoinositide 3-kinase Inhibitor Research Articles

Abstract B065: Combining the androgen receptor inhibitor darolutamide with PI3K/AKT/mTOR pathway inhibitors has superior efficacy in preclinical models of prostate cancer

Abstract The phosphoinositide 3 kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway is dysregulated in the majority of advanced prostate cancer patients, often linked to phosphate and tensin homolog (PTEN) inactivation. An increasing number of studies demonstrates the reciprocal crosstalk between the PI3K/AKT/mTOR and the androgen receptor (AR) pathways with the inhibition of one of them leading to the compensatory activation of the other one. We compared the effects of different PI3K/AKT/mTOR pathway inhibitors as single agents or in combination with the AR inhibitor darolutamide.In vitro impact of the compounds was evaluated in prostate cancer cell lines by proliferation and apoptosis assays, and by RNA-seq analysis. In vivo effects were determined in a patient-derived (PDX) prostate cancer model in an efficacy study followed by immunohistochemistry analysis. Analysis of VCaP cells treated with the androgen R1881 showed that beside androgen response, the PI3K/AKT/mTOR pathway was an essential hallmark characteristic of androgen action. Additional darolutamide treatment opposed androgen effects on both pathways. We therefore evaluated the impact of selective inhibitors of PI3K or AKT and saw strong in vitro antiproliferative effects in the prostate cancer cell lines tested. We then focused on the pan-PI3K inhibitor copanlisib and observed pronounced synergistic effects with darolutamide in the VCaP model. This was accompanied by induction of PARP cleavage and activation of caspase 3/7. A detailed transcriptomic analysis revealed that the combination of both inhibitors resulted in more pronounced transcript changes, compared to individual treatments. Principal component analysis furthermore showed the combination to be closer to the DMSO control along the axis that represents androgen regulation. We observed a pronounced downregulation of cell proliferation and cell division genes following combination treatment compared to individual treatments, a prominent example being the proliferation marker KI67. In vivo studies performed with the PDX LuCaP 35 model revealed a superior inhibitory effect of the combination treatment with darolutamide and copanlisib when compared to single agents. Immunohistochemistry analysis revealed a significant upregulation of a pro-apoptotic pathway in tumors treated with darolutamide and copanlisib which was not observed in single treatment arms, when compared to vehicle control. In summary, we found that different PI3K and AKT inhibitors impaired the in vitro proliferation of prostate cancer cell lines. Combining the AR inhibitor darolutamide with the pan-PI3K inhibitor copanlisib led to increased apoptosis and down-regulation of cell division and proliferation genes. Importantly, the improved tumor inhibition by the combination was also observed in vivo. These results warrant further analysis of the impact of combined AR and PI3K pathway inhibition in prostate cancer, especially when aberrations in the PI3K/AKT/mTOR pathway or PTEN loss are observed. Citation Format: Simon Heller, Tatsuo Sugawara, Ekaterina Nevedomskaya, Simon J. Baumgart, Holly Nguyen, Eva Corey, Annika Böhme, Oliver von Ahsen, Oliver Politz, Bernard Haendler. Combining the androgen receptor inhibitor darolutamide with PI3K/AKT/mTOR pathway inhibitors has superior efficacy in preclinical models of prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B065.

Phosphoinositide 3-Kinase (PI3K) Inhibitors and Breast Cancer: An Overview of Current Achievements.

The phosphatidylinositol 3-kinase (PI3K) pathway is one of the most altered pathways in human cancers, and it plays a central role in cellular growth, survival, metabolism, and cellular mobility, making it a particularly interesting therapeutic target. Recently, pan-inhibitors and then selective p110α subunit inhibitors of PI3K were developed. Breast cancer is the most frequent cancer in women and, despite therapeutic progress in recent years, advanced breast cancers remain incurable and early breast cancers are at risk of relapse. Breast cancer is divided in three molecular subtypes, each with its own molecular biology. However, PI3K mutations are found in all breast cancer subtypes in three main "hotspots". In this review, we report the results of the most recent and main ongoing studies evaluating pan-PI3K inhibitors and selective PI3K inhibitors in each breast cancer subtype. In addition, we discuss the future of their development, the various potential mechanisms of resistance to these inhibitors and the ways to circumvent them.

Precision medicine: Novel PI3K inhibitor as cancer treatment.

e15093 Background: Phosphoinositide 3-kinase (PI3K) is an attractive anti-cancer drug target due to its promotion of cell growth and proliferation; however, available pan-PI3K inhibitors currently lack specificity, leading to excessive drug toxicity and adverse effects. Selectide-18 is a novel PI3K inhibitor that targets PI3K’s catalytic subunit p110β, resulting in reduced viability of cancer cells. The p110β subunit is the most prominent PI3K subunit in many chemoresistant tumors. Previous research has revealed a unique 18-residue long motif within the C2 domain of p110β. This motif is not found in other catalytic subunits (p110α, p110δ, or p110γ), making it a promising drug target. Selectide-18 is a memetic peptide drug modeled after this motif and has been shown to effectively inhibit p110β binding without affecting other isoforms, separating it from currently available pan-PI3K inhibitors. While Selectide-18 has been successful in inhibiting PI3K in previous studies, it has poor cell permeability due to its large size. Previous findings have revealed functional redundancies among Selectide-18’s residues. This study aims to remove these redundancies and determine the optimal formulation of Selectide-18 through in silico analysis. Methods: An in silico protocol was developed to determine the optimal formulation of Selectide-18. By utilizing the PEP-FOLD server, 455 peptide models were created using 91 unique fragments of the Selectide-18 amino acid sequence ranging in size from 6 to 17 residues. Physical conformation of each model was compared to wild-type Selectide-18 using root-mean-square deviation data collected using PyMOL and UCSF Chimera software. Computational docking through AutoDock Vina was performed to test the binding affinity of each model to the active site of regulatory subunit p85α. The distance between each drug and the active site was measured with UCSF Chimera’s distance function. Finally, ClusPro docking of drug-bound p85α/p110β was compared to wild-type p85α/p110β, as well as non-truncated Selectide-18-bound p85α/p110β. Statistical significance was determined using a Student's t-test. Results: Select truncated models demonstrated physical confirmation (RMSD = 0.024), binding affinity (-8.74 kcal/mol), and simulated inhibitory capabilities comparable to Selectide-18. A specific group of variants comprised of 9 amino acids (9 residue_6K-14Q) had the shortest formulation without significant declines in binding affinity. Conclusions: Selectide-18 is a selective PI3K inhibitor that can be optimized by removing functionally redundant amino acids. A 9-residue variant ranging from amino acids 6Lys to 14Gln showed the most promise and will be used in future studies to reformulate Selectide-18. Being half the size of Selectide-18, this optimized drug is anticipated to have improved cell permeability without sacrificing inhibitory function.

First-in-human (FIH) phase I study of the highly selective phosphoinositide 3-kinase inhibitor delta (PI3Kδ) inhibitor IOA-244 in patients with advanced cancer: Safety, activity, pharmacokinetic (PK), and pharmacodynamic (PD) results.

3107 Background: T regulatory (Tregs) cells contribute to immune suppression in cancer. The highly selective inhibitor of PI3Kδ, IOA-244, blocks the activity of Tregs among other things, thus reprograms the anti-tumor immune response. Methods: IOA-244 was investigated in a two-part FIH study. Part A explored the continuous daily dosing of IOA-244 at 10, 20, 40 and 80 mg. Part B consists of expansion cohorts of specific tumor indications, including pre-treated uveal melanoma patients (pts). Primary objective: safety of the anticipated biologically effective dose (BED), or the recommended phase 2 dose (RP2D). Secondary objectives: PK; PD (e.g., inhibition of CD63 expression on basophils, changes in immune cell subsets in peripheral blood); RECIST 1.1.-based responses; PFS and OS. Exploratory studies: changes in circulating immune cells by Cytometry by Time of Flight (CyTOF); response assessments by radiomics Results: Part A Solid Tumor (completed): Sixteen pts were treated in 4 cohorts each with 4 pts. Pts characteristics: uveal melanoma (9/16; 56%), cutaneous melanoma (5/16; 31%) and pleural mesothelioma (2/16; 13%). Four pts had at least one serious TEAE, none considered related to IOA-244. There was no treatment-emergent adverse events (TEAE) leading to study drug discontinuation, immune related toxicity or Dose Limiting Toxicity. CTCAE v5 Grade 1 and 2 were observed, including 2 cases of transient diarrhoea and 2 of AST/ALT elevation. Part A (Completed) – Subgroup Uveal Melanoma Pts (progressed ≥1 line prior therapy): 9 pts treated (3/9 pts ongoing). Mean time on treatment: 7.7 mo (range: 1.8-16.0 mo with 3 pts ongoing). ORR (RECIST 1.1): CR+PR: 0/9 (0%); SD: 6/9 (67%). Median OS: 5.4 mo - not determined (% alive at 1 year: 44% with 3 pts ongoing). CT images from 7/9 patients were assessed for changes in their metastatic lesions by radiomics (baseline and Week 8). Based on 147 matched lesions, 19% had complete responses and 16% had new lesions. In the liver, non-progressive disease was observed in 61% of all lesions, including 42% with either complete response or volume reduction of more than 30%. Using CyTOF, circulating Tregs were reduced while CD8 and NK cells were increased. Part B Uveal Melanoma Expansion Cohort (ongoing): 7 patients (7/7 pts ongoing); mean time on treatment 3.7 mo. ORR (RECIST 1.1): SD in 4/7 pts (57%). Part A Follicular Lymphoma Cohort (ongoing): At 20 mg: 4/4 pts. No DLT. At 80 mg: recruiting. Conclusions: In addition to being well tolerated, IOA-244 at the 80 mg dose shows reduction in peripheral blood Tregs and anti-tumor responses based on radiomics. Therefore, RECIST 1.1.-derived SD may underestimate anti-tumor activity of IOA-244 in treatment-resistant uveal melanoma. Additional patients will be treated to further refine this radiomics-based observation. Clinical trial information: NCT04328844.

Tumor suppressor functions of miRNA-375 in nasopharyngeal carcinoma through inhibition of ubiquitin-specific protease 1 expression.

Nasopharyngeal carcinoma (NPC) development involves many genetic alterations. This study profiled differentially expressed microRNAs (DE-miRNAs) and selected miR-375 for further study. DE-miRNAs were screened using online databases and subjected to various analyzes. miR-375 mimics with negative control (NC) cDNA, and a ubiquitin-specific protease 1 (USP1) as well as a NC group were transfected into NPC cells for analysis by quantitative PCR, western blotting, wound healing, Transwell, flow cytometry, cell counting kit-8 (CCK-8), and luciferase gene reporter assays. Among these DE-miRNAs, miR-375 was downregulated and miR-21 was upregulated in NPC cells. Bioinformatical analysis identified USP1 as a potential target gene of miR-375. Increased USP1 expression was associated with poor survival of head and neck cancer patients. The luciferase assay confirmed miR-375 binding to the USP1 3'-untranslated region (UTR), while the transfection experiment confirmed miR-375 expression reduced USP1 expression. USP1 overexpression reversed the anti-tumor activity of miR-375 in NPC cells as determined by tumor cell migration, invasion, apoptosis, and viability assays. In addition, USP1 overexpression activated phosphoinositide 3-kinase (PI3K) signaling, whereas a selective PI3K inhibitor (S2739) could reverse the effects of USP1 on NPC cells in vitro. miR-375 and miR-21 are both related to NPC and miR-375 can target USP1. Further experiments revealed that up-regulated miR-375 expression led to USP1 down-regulation, and miR-375 overexpression suppressed PI3K/Akt signaling and inhibited NPC cell migration and invasion, but promoted NPC cell apoptosis.

Acetylation of the Catalytic Lysine Inhibits Kinase Activity in PI3Kδ

Covalent inhibition is a powerful strategy to develop potent and selective small molecule kinase inhibitors. Targeting the conserved catalytic lysine is an attractive method for selective kinase inactivation. We have developed novel, selective inhibitors of phosphoinositide 3-kinase δ (PI3Kδ) which acylate the catalytic lysine, Lys779, using activated esters as the reactive electrophiles. The acylating agents were prepared by adding the activated ester motif to a known selective dihydroisobenzofuran PI3Kδ inhibitor. Three esters were designed, including an acetate ester which was the smallest lysine modification evaluated in this work. Covalent binding to the enzyme was characterized by intact protein mass spectrometry of the PI3Kδ-ester adducts. An enzymatic digest coupled with tandem mass spectrometry identified Lys779 as the covalent binding site, and a biochemical activity assay confirmed that PI3Kδ inhibition was a direct result of covalent lysine acylation. These results indicate that a simple chemical modification such as lysine acetylation is sufficient to inhibit kinase activity. The selectivity of the compounds was evaluated against lipid kinases in cell lysates using a chemoproteomic binding assay. Due to the conserved nature of the catalytic lysine across the kinome, we believe the covalent inhibition strategy presented here could be applicable to a broad range of clinically relevant targets.

Efficacy and Safety of Phosphoinositide 3-Kinase (PI3K) Inhibitors in Non-Hodgkin's Lymphoma: A Systematic Review and Meta-Analysis

Background: Phosphatidylinositol-3-Kinase (PI3K)-oncogenic protein kinase is ubiquitously expressed in cells, however, PI3Kδ and PI3Kγ are selectively expressed in hematopoietic cells predominantly in leucocytes. Suppression of the PI3K pathway has emerged as a therapeutic strategy for non-Hodgkin lymphoma (NHL) and 3 PI3K inhibitors are already approved for therapeutic use with many others under exploration. The application of these agents in terms of risk and benefit remains scarcely explored. Therefore, a systematic review and meta-analysis was conducted to assess the efficacy and safety of PI3K inhibitors in non-Hodgkin lymphoma. Methods: A comprehensive literature search was conducted from inception to the 4th of April 2020, following PRISMA guidelines on 4 databases (PubMed, Cochrane library, clinicaltrials.gov, web of science, and Embase). A search was performed without the use of filters and the MeSH terms used were "lymphoma, non-Hodgkin" and "phosphoinositide-kinase inhibitors". Only studies with available data that were either completed or still recruiting were included. Trials with no reported efficacy or safety data were excluded. A pooled analysis of the extracted data was performed using the "meta" package by Schwarzer et al. in the R programming language (version 4.0.2). For data analysis purposes, in the case of multi-arm studies, only those cohorts where PI3K was administered were included. The event rates were pooled using the inverse variance method and logit transformation. The between-studies variance was calculated using the DerSimonian-Laird estimator. The random-effects model was used for the analysis. Results: Initial search revealed 391 articles. After a thorough screening, 22 studies involving 1123 patients with relapsed or refractory NHL that fulfilled the inclusion criteria were included (Table 1). The median age ranged from 58-70 years. The median number of prior therapies ranged from 2 to 4. Twenty studies used a selective PI3K inhibitor including voxtalisib, pilaralisib, umbralisib, duvelisib, idelalisib, copanlisib, buparlisib, and parsaclisib. The pooled overall response rate (ORR) was 50% [95% CI: 42%; 58%] with pooled complete response of 15% [95% CI: 12%; 20%]. A subgroup analysis was performed on complete responses (CR) of patients with diffuse large B cell lymphoma (DLBCL), and follicular lymphoma (FL). The CR in FL and DLBCL were 20% [95% CI: 15%-20%] and 14% [95% CI 8%-25%] respectively, and the difference between the two subgroups was statistically non-significant with the Cochran Q test yielding the p-value of 0.34. The overall survival (OS) was extractable in only 3 studies with the highest OS reported as 28.9 months. The progression-free survival (PFS) ranged from 1.9 to 37.1 months and was reported in 16 studies. In terms of safety, the most common ≥ grade 3 hematologic abnormality was neutropenia with a pooled incidence rate of 24% [18%; 32%] while the pooled incidence rates of anemia and thrombocytopenia were 11% [7%; 17%], and 10% [7%; 13%]. Diarrhea was the most common ≥ grade 3 non-hematological adverse event, which was seen in 14.85% [12%;18%] patients. Conclusion: PI3K pathway inhibitors have shown promising efficacy. However, the therapeutic applicability is hindered by the off-target adverse events especially gastrointestinal as well as the consequences of neutropenia. Overcoming these limitations would involve exploring the selectivity of novel agents, optimizing sequencing, use in combination regimens, and varying of the doses. Table Disclosures Anwer: Incyte, Seattle Genetics, Acetylon Pharmaceuticals, AbbVie Pharma, Astellas Pharma, Celegene, Millennium Pharmaceuticals.:Honoraria, Research Funding, Speakers Bureau.

Abstract P3-11-01: An updated systematic review and meta-analysis of the safety and efficacy of phosphoinositide 3-kinase inhibitors (PI3Ki) in advanced breast cancer

Abstract Background In advanced breast cancer (ABC), the addition of pan-PI3Ki to the standard of care (SOC) treatment improves tumor response rate and progression free survival (PFS). Yet, further development of these drugs has been limited by their safety profile. Instead, selective PI3Ki were assessed and the Food and Drug Administration has recently approved the use of a selective PI3Ki based on a phase 3 randomized trial. Therefore, we updated our systematic review and meta-analysis to evaluate whether there is a difference in the efficacy and/or safety of pan versus selective PI3Ki in ABC. Methods The electronic databases Ovid PubMed, Cochrane Central Register of Controlled Trials and Embase, were searched for relevant publications reporting randomized controlled trials between January 2000 and June 2019. Pooled hazard ratios (HR) for progression-free survival (PFS), and pooled odds ratios (OR) for objective response rate (ORR), disease control rate (DCR) and toxicity were computed and weighted using Mantel-Haenszel method and generic inverse variance. Subgroup analyses compared patients with and without PI3K pathway activation. Results Seven studies comprising 3,597 patients were included (5 studies with pan-PI3Ki and 2 studies with selective PI3Ki). Pan and selective PI3Ki decreased the risk of progression by 21% and 32% compared to SOC: HR: 0.79, 95%CI 0.0.71-0.88 and 0.68, 95%CI 0.57-0.81 respectively, p for test for subgroup differences: 0.16. An improvement in ORR was more pronounced with the use of selective versus pan PI3Ki: OR 2.67, 95%CI 1.78-4.00 and OR 1.31, 95%CI 1.01-1.71 respectively, p for test for subgroup differences: 0.004 and DCR was only improved with selective PI3Ki: OR 1.85 95%CI 1.37-2.51. A statistically significant increase in the toxicity of any grade and of grade 3 and higher was observed with pan and selective PI3Ki: 1) for any grade toxicity: OR 5.51, 95%CI 3.05-9.96, and OR 3.77, 95%CI 2.16-6.58 respectively, p for test for subgroup differences 0.16; 2) for grade 3 or higher toxicity: OR 1.91, 95%CI 1.76-2.08 and OR 2.41, 95%CI 2.07-2.82 respectively; p for test for subgroup difference 0.01. In subgroup analyses, the PFS improvement was more pronounced in the PI3K mutant subgroup: HR 0.72, 95%CI 0.63-81 for the PI3K mutant subgroup and HR 0.83, 95%CI 0.73-0.96 for the PI3K wild-type subgroup, p for test for subgroup differences 0.11. Conclusion While selective PI3Ki have a better effect on ORR, DCR and PFS in patients with ABC compared to pan PI3Ki; their toxicity profile is still clinically substantial. Rigorous safety monitoring and early medical intervention are needed to reduce treatment discontinuation, optimize efficacy and render these drugs more clinically usable. Citation Format: Jacques Raphael, Syed Hussaini, Kathleen I Pritchard, Prakesh Shah, Phillip Blanchette, Ricardo Fernandes, Danielle Desautels. An updated systematic review and meta-analysis of the safety and efficacy of phosphoinositide 3-kinase inhibitors (PI3Ki) in advanced breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-11-01.

Sorafenib Suppresses Basal Spontaneous Beating of Rabbit Sinoatrial Node Cells (SANC) through Inhibition of Vascular Endothelial Growth Factor Receptor 1 (VEGFR1)

Sarcoplasmic reticulum generated local subsarcolemmal Ca2+ releases (LCRs) in SANC appear during diastolic depolarization and activate an inward Na+-Ca2+ exchange current accelerating the diastolic depolarization rate and thus increasing spontaneous SANC firing. Sorafenib, multitargeted tyrosine kinase inhibitor treating renal, liver and thyroid malignances, inhibits VEGFR, platelet-derived growth factor-receptor and rapidly accelerated fibrosarcoma (RAF) kinases. Sorafenib treatment is associated with myocardial infarction and increased incidence of atrial fibrillation that could be linked to suppression of cardiac pacemaker function. The goal of the present study is to determine whether sorafenib affects spontaneous firing of SANC and, if so, define specific downstream targets effected by sorafenib. Expression of VEGFR1, VEGFR2 and PLCγ (assessed by RT-qPCR) in rabbit sinoatrial node was comparable to that of β1-adrenergic receptors. Sorafenib: (1) markedly decreased the LCR size and number (confocal microscopy, Ca2+ indicator Fluo-3); (2) prolonged the LCR period (interval between action potential-induced Ca2+ transient and subsequent LCR); (3) in a time-dependent manner decreased and then abrogated spontaneous firing of single isolated SANC. A selective pan-inhibitor of VEGFR1/2/3 (PTK787/ZK222584) also decreased spontaneous SANC beating rate by ∼50%, suggesting that VEGFR1/2 could be one of major targets of sorafenib. The selective VEGFR2 inhibitor ZM-323881, however, suppressed spontaneous firing in only ∼18% of SANC suggesting that VEGFR1, but not VEGFR2 signaling, is linked to SANC automaticity. Phosphoinositide-3-kinase (PI3K) and phospholipase C (PLC) are downstream targets of VEGFR. While selective PI3K inhibitor PI-103 was lacking effects, PLC inhibitor U-73122 markedly decreased the LCR size, number, extended the LCR period and prolonged the spontaneous SANC cycle length. Our results strongly suggest that activation of VEGFR1-PLC pathway is involved in regulation of normal automaticity of cardiac pacemaker cells.

Casticin inhibits nasopharyngeal carcinoma growth by targeting phosphoinositide 3-kinase

BackgroundCasticin, an isoflavone compound extracted from the herb Fructus Viticis, has demonstrated anti-inflammatory and anticancer activities and properties. The aim of this study was to investigate the effects and mechanisms of casticin in nasopharyngeal carcinoma (NPC) cells and to determine its potential for targeted use as a medicine.MethodsNPC cells were used to perform the experiments. The CCK‑8 assay and colony formation assays were used to assess cell viability. Flow cytometry was used to measure the cell cycle and apoptosis analysis (annexin V/PI assay). A three-dimensional (3D) tumour sphere culture system was used to characterize the effect of casticin on NPC stem cells. In silico molecular docking prediction and high-throughput KINOME scan assays were used to evaluate the binding of casticin to phosphoinositide 3-kinase (PI3K), including wild-type and most of mutants variants. We also used the SelectScreen assay to detect the IC50 of ATP activity in the active site of the target kinase. Western blotting was used to evaluate the changes in key proteins involved cell cycle, apoptosis, stemness, and PI3K/protein kinase B (AKT) signalling. The effect of casticin treatment in vivo was determined by using a xenograft mouse model.ResultsOur results indicate that casticin is a new and novel selective PI3K inhibitor that can significantly inhibit NPC proliferation and that it induces G2/GM arrest and apoptosis by upregulating Bax/BCL2 expression. Moreover, casticin was observed to affect the self-renewal ability of the nasopharyngeal carcinoma cell lines, and a combination of casticin with BYL719 was observed to induce a decrease in the level of the phosphorylation of mTORC1 downstream targets in BYL719-insensitive NPC cell lines.ConclusionCasticin is a newly emerging selective PI3K inhibitor with potential for use as a targeted therapeutic treatment for nasopharyngeal carcinoma. Accordingly, casticin might represent a novel and effective agent against NPC and likely has high potential for combined use with pharmacological agents targeting PI3K/AKT.

Benefits versus risk profile of buparlisib for the treatment of breast cancer

ABSTRACTIntroduction: Activation of phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathways occurs in 70% of breast cancer, including PIK3CA activating mutations, PTEN loss and AKT mutation. It is associated with poor prognosis and resistance to anti-HER2 and endocrine therapy. PI3K inhibitors are promising anticancer targets that can reverse resistance to these therapies. Buparlisib (BKM-120) is an orally active pan-PI3K inhibitor evaluated in different solid tumors as monotherapy or in combination.Areas covered: This article reviews preclinical data, clinical studies that have evaluated the efficacy and safety profiles of buparlisib as a monotherapy or in combination with targeted therapy (including endocrine and anti-HER2 therapy) or cytotoxics. The authors cover completed and ongoing studies to evaluate the benefit vs risk profile of buparlisib.Expert opinion: Targeting PI3K showed efficacy in BC. Buparlisib, a pan PI3K inhibitor, presents manageable but not negligible toxicity with an activity/toxicity ratio in favor of the use of emerging second generation, α–selective PI3K inhibitors for ongoing and future trials.

Discovery of Potent, Efficient, and Selective Inhibitors of Phosphoinositide 3-Kinase δ through a Deconstruction and Regrowth Approach.

A deconstruction of previously reported phosphoinositide 3-kinase δ (PI3Kδ) inhibitors and subsequent regrowth led to the identification of a privileged fragment for PI3Kδ, which was exploited to deliver a potent, efficient, and selective lead series with a novel binding mode observed in the PI3Kδ crystal structure.

Ocena profilu korzyści i ryzyka leczenia idelalizybem u chorych na przewlekłą białaczkę limfocytową i chłoniaki nie-Hodgkina

Idelalisib is a selective inhibitor of phosphoinositide 3-kinase d , approved in relapsed/refractory (RR) chronic lymphocytic leukemia (CLL), first line CLL with del17p/TP53 mutation in patients unsuitable for immunochemotherapy and RR follicular lymphoma (FL) in whom at least two lines of therapy have failed. Despite good clinical efficacy, the development of this drug has been hampered due to its adverse events (i.e. autoimmune reactions and life-threatening opportunistic infections). In this retrospective study, we summarise the tolerability of idelalisib therapy in a Polish population, analysing 61 patients treated with idelalisib in monotherapy or idelalisib-based combination regimens. Idelalisib treatment was feasible for the majority of patients, with upper respiratory tract infections (N = 13.21%) being the most common adverse event (AE), and pneumonia (N = 11.18%) — the most prevalent grade 3 or higher non-hematological AE. We observed two cases of pneumonitis, one case of gastroenteritis, and no cases of liver transaminases elevation (all regarded as the AEs characteristic of idelalisib). Most of the patients were treated in haematology reference centres where physicians are more accustomed to dealing with opportunistic infections. Cotrimoxazole prophylaxis was given to 20 (32.8%) patients, whereas acyclovir prophylaxis was administered in 33 (54.1%) cases. This could explain the less frequent life-threatening infections and decreased mortality rate compared to the published registration studies. Our study confirms the high clinical efficacy of idelalisib in CLL and RR FL.

Methylene blue offers neuroprotection after intracerebral hemorrhage in rats through the PI3K/Akt/GSK3β signaling pathway.

Inflammation and apoptosis are two key factors contributing to secondary brain injury after intracerebral hemorrhage (ICH). In the present study, we explored the neuroprotective role of methylene blue (MB) in ICH rats and studied the potential mechanisms involved. Rats were subjected to local injection of collagenase IV in the striatum or sham surgery. We observed that MB treatment could exert a neuroprotective effect on ICH by promoting neurological scores, decreasing the brain water content, alleviating brain-blood barrier disruption, and improving the histological damages in the perihematomal areas. Furthermore, we demonstrated that the various mechanisms underlying MB's neuroprotective effects linked to inhibited apoptosis and inhibited neuroinflammation. In addition, wortmannin, a selective inhibitor of phosphoinositide 3-kinase (PI3K), could reverse the antiapoptotic and anti-inflammatory effects of MB, which suggested that the PI3K-Akt pathway played an important role. In conclusion, these data suggested that MB could inhibit apoptosis and ameliorate neuroinflammation after ICH, and its neuroprotective effects might be exerted via the activation of the PI3K/Akt/GSK3β pathway.

Over-activated PD-1/PD-L1 axis facilitates the chemoresistance of diffuse large B-cell lymphoma cells to the CHOP regimen.

Interaction between the programmed cell death ligand 1 (PD-L1) and programmed cell death 1 (PD-1) contributes to tumor cell resistance to chemotherapeutic agents. PD-L1 is expressed in the cells of diffuse large B-cell lymphoma (DLBCL), one common type of malignant non-Hodgkin lymphomas. However, little is known about how the PD-1/PD-L1 pathway functions in the pathogenesis of DLBCL. Therefore, the present study investigated whether and how the PD-1/PD-L1 axis is involved in regulating the sensitivity of CRL2631, a DLBCL cell line, to the CHOP (Cyclophosphamide, Hydroxydaunorubicin/adriamycin, Oncovin/vincristine and Prednisone) chemotherapeutic regimen. CHOP treatment significantly decreased cell survival rate and increased apoptosis in CRL2631 cells. The application of recombinant human PD-1 (rPD-1) significantly decreased the cytotoxic effects of the CHOP regimen in CRL2631 cells, but not in the CRL2631 cells with PD-L1 deficiency. In the CRL2631 cells, rPD-1 enhanced the activity of the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt1) pathway. However, the activity level of the PI3K/Akt1 pathway was decreased in CHOP-treated CRL2631 cells. The selective PI3K inhibitor BKM120 significantly increased CHOP-induced apoptosis, but this effect was abolished by rPD-1 and aggravated by PD-L1 knockdown. In CHOP-treated PD-L1 knockdown cells, the increased apoptosis was markedly inhibited by the overexpression of constitutively active Akt1. Overall, the results demonstrate that the over-activated PD-1/PD-L1 axis is associated with chemotherapeutic resistance of DLBCL cells to the CHOP regimen, potentially through a PI3K-dependent mechanism.

Abstract P3-14-10: Phase Ia/Ib study of taselisib (GDC-0032), a potent and selective phosphoinositide 3-kinase inhibitor, in Japanese patients with advanced solid tumors or hormone receptor-positive locally advanced or metastatic breast cancer (JO29196 study)

Abstract Background: Taselisib (GDC-0032) is an orally bioavailable, potent and selective phosphoinositide 3-kinase (PI3K) inhibitor. Preclinical data showed that taselisib had increased antitumor activity against PIK3CA (gene encoding the PI3Kα isoform) mutant tumors. This study aimed to investigate the safety, tolerability and pharmacokinetics (PK) of taselisib as monotherapy and in combination with fulvestrant in Japanese patients (pts). Materials and methods: A 3+3 design was used. In Phase Ia, pts with advanced solid tumors received taselisib tablet monotherapy (2, 4 or 6 mg once daily [QD]), and safety and PK were evaluated. In Phase Ib, pts with hormone receptor-positive locally advanced or metastatic breast cancer received taselisib (2 or 4 mg QD) in combination with fulvestrant (500 mg at a time), and safety and PK were evaluated. Maximal administered doses of 6 mg QD as a single agent and 4 mg QD in combination with fulvestrant were based upon prior clinical trial experience with taselisib (Juric D. et al. AACR 2013, Abstract LB-64; Juric D. et al. SABCS 2013, Abstract PD1-3). Results: As of 15 Mar 2015, 9 pts (PIK3CA mutant: 2 pts) were enrolled in Phase Ia and 3 pts in Phase Ib. Phase Ia dose-escalation study has been completed and Phase Ib is ongoing. In Phase Ia, no dose-limiting toxicity (DLT) was observed at any dose level tested (maximum administered dose of 6 mg QD). Common (≥3 pts) adverse reactions (ARs) were stomatitis (4 pts), rash (3 pts) and diarrhea (3 pts); the only Grade ≥3 AR was neutropenia (1 pt). Partial response was observed in 1 pt who received taselisib 4 mg and had a PIK3CA mutant breast tumor. Stable disease was observed in 4 pts. Cmax and AUC indicated a dose-proportional PK profile of taselisib within the dose range tested. Moreover, taselisib PK in Japanese pts was consistent with the PK reported from North American and European pts (Juric D. et al. AACR 2013, Abstract LB-64). In Phase Ib, 3 pts received taselisib 2 mg in combination with fulvestrant and no DLT was observed. Preliminary ARs were similar to those with monotherapy and no Grade ≥3 AR was reported. Confirmation of tolerability of taselisib 4 mg in combination with fulvestrant is under evaluation. Conclusion: Taselisib monotherapy was well tolerated in Japanese pts up to a dose of 6 mg, which is the recommended dose in non-Japanese pts. Promising preliminary activity of monotherapy was observed in advanced solid tumors, especially in a pt with PIK3CA mutant tumor. The combination of taselisib 2 mg with fulvestrant is well tolerated. Investigation of tolerability of taselisib 4 mg in combination with fulvestrant is ongoing. Final results of this study will be presented here at the Symposium this year. Citation Format: Kobayashi T, Nakano K, Tomomatsu J, Nara E, Ito Y, Kobayashi K, Fukada I, Araki K, Shimomura A, Shimoi T, Kodaira M, Yunokawa M, Yonemori K, Shimizu C, Nakamura K, Kotani N, Inatani M, Tamura K, Takahashi S. Phase Ia/Ib study of taselisib (GDC-0032), a potent and selective phosphoinositide 3-kinase inhibitor, in Japanese patients with advanced solid tumors or hormone receptor-positive locally advanced or metastatic breast cancer (JO29196 study). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-14-10.

Abstract B28: Activating mutations in PIK3CB confer resistance to PI3K inhibition in PTEN-deficient breast cancer and define a novel oncogenic role for p110β

Abstract Activation of the phosphoinositide 3-kinase (PI3K) pathway occurs commonly in breast cancers via mechanisms that include loss of function of the tumor suppressor phosphatase and tensin homolog (PTEN). Experience with other successful targeted agents suggests that clinical resistance to PI3K inhibitors is likely to arise and may reduce the durability of clinical benefit. Here, we sought to understand mechanisms underlying resistance to PI3K inhibition in PTEN deficient breast cancers. PTEN null breast cancer cell lines were selected for resistance to a pan-PI3K inhibitor, GDC-0941. Comprehensive molecular and cellular profiling was conducted to identify the mechanism of resistance. We generated GDC-0941 resistant derivatives of PTEN deficient EVSA-T and ZR-75-1 cell lines and identified a novel PIK3CB D1067Y mutation in both cell lines. We found that the PIK3CB mutation at D1067 position was recurrent in cancer patients. Stable expression of mutant PIK3CB variants in PTEN null breast cancer cells conferred resistance to PI3K inhibition that could be overcome by downstream AKT or mTORC1/2 inhibitors. We showed further that the p110β D1067Y mutant is highly activated and elevates PIP3 level at the cell membrane, promoting localization and activation of AKT and PDK1 at the cell membrane and driving PI3K signaling to a level that can overcome treatment with proximal inhibitors. Finally, we show that the PIK3CB D1067Y mutant can behave as an oncogene and transform normal cells, and that PTEN knock down enhances this activity. These novel preclinical and clinical findings implicate PIK3CB D1067 alterations as a novel oncogene that may cause resistance to selective PI3K inhibitor treatment. Taken together with previous findings that PTEN deficient cancers tend to signal through p110β rather than p110α, this work also suggests PTEN deficient breast cancers may depend on p110β and are thereby susceptible to PIK3CB mutation as an escape mechanism from PI3K inhibition. Citation Format: Yoshito Nakanishi, Kimberly M. Walter, Jill M. Spoerke, Carol O'Brien, Ling Y. Huw, Garret M. Hampton, Mark R. Lackner. Activating mutations in PIK3CB confer resistance to PI3K inhibition in PTEN-deficient breast cancer and define a novel oncogenic role for p110β. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr B28.

CCN1 acutely increases nitric oxide production via integrin αvβ3–Akt–S6K–phosphorylation of endothelial nitric oxide synthase at the serine 1177 signaling axis

Although CCN1 (also known as cysteine-rich, angiogenic inducer 61, CYR61) has been reported to promote angiogenesis and neovascularization in endothelial cells (ECs), its effects on endothelial nitric oxide (NO) production have never been studied. Using human umbilical vein ECs, we investigated whether and how CCN1 regulates NO production. CCN1 acutely increased NO production in a time- and dose-dependent manner, which was accompanied by increased phosphorylation of endothelial NO synthase (eNOS) at serine 1177 (eNOS-Ser1177), but not that of eNOS-Thr495 or eNOS-Ser114. The level of total eNOS expression was unaltered. Treatment with either LY294002, a selective inhibitor of phosphoinositide 3-kinase known as an upstream kinase of Akt, or H-89, an inhibitor of protein kinase A, mitogen- and stress-activated protein kinase 1, Rho-associated protein kinase 2, and ribosomal protein S6 kinase (S6K), inhibited CCN1-stimulated eNOS-Ser1177 phosphorylation and subsequent NO production. Ectopic expression of small interfering RNA against Akt and S6K significantly inhibited the effects of CCN1. Consistently, CCN1 increased the phosphorylation of Akt-Ser473 and S6K-Thr389. However, CCN1 did not alter the expression or secretion of VEGF, a known downstream factor of CCN1 and a potential upstream factor of Akt-mediated eNOS-Ser1177 phosphorylation. Furthermore, neutralization of integrin αvβ3 with corresponding antibody completely reversed all of the observed effects of CCN1. Moreover, CCN1 increased acetylcholine-induced relaxation in the rat aortas. Finally, we also found that CCN1-stimulated eNOS-Ser1177 phosphorylation and NO production are true for other types of EC tested. In conclusion, CCN1 acutely increases NO production via activation of a signaling axis in integrin αvβ3–Akt–S6K–eNOS-Ser1177 phosphorylation, suggesting an important role for CCN1 in vasodilation.

Optimization of Novel Indazoles as Highly Potent and Selective Inhibitors of Phosphoinositide 3-Kinase δ for the Treatment of Respiratory Disease.

Optimization of lead compound 1, through extensive use of structure-based design and a focus on PI3Kδ potency, isoform selectivity, and inhaled PK properties, led to the discovery of clinical candidates 2 (GSK2269557) and 3 (GSK2292767) for the treatment of respiratory indications via inhalation. Compounds 2 and 3 are both highly selective for PI3Kδ over the closely related isoforms and are active in a disease relevant brown Norway rat acute OVA model of Th2-driven lung inflammation.

Abstract B37: Mechanisms of acquired resistance to the PI3K inhibitor GDC-0941 in breast cancer cell lines

Abstract Alterations of the phosphoinositide-3 kinase (PI3K)/Akt signaling pathway occur broadly in cancer via multiple mechanisms including mutation of the PIK3CA gene or loss of the tumor suppressor PTEN. The dysregulation of this pathway has been implicated in tumor initiation, cell growth and survival, invasion and angiogenesis, thus, PI3K is a promising therapeutic target for cancer. There are several PI3K inhibitors in clinical trials and the current study was intended to investigate preclinical mechanisms of acquired resistance to GDC-0941, a class I selective PI3K inhibitor. GDC-0941 resistant pools and clones were generated in both EVSA-T and HCC-1954 breast cancer cell lines by treating cells with increasing concentrations of drug. We found that resistant clones from both lines demonstrated marked increase of downstream PI3K pathway signaling and upregulation of the MAPK pathway, through two different mechanisms. In HCC-1954, autocrine signaling to EGFR was observed in the resistant clones and resulted in increased dependency on the downstream factor c-Myc. EVSA-T clones with acquired resistance to GDC-0941 had elevated HER2 copy number and protein expression levels. A corresponding increase in phosphorylation of HER2 binding partner ErbB3 was also discovered in the EVSA-T resistance cells. In both cases sensitivity to PI3K inhibition was restored by blocking the activated upstream receptor tyrosine kinase, EGFR for HCC-1954 and HER2 for EVSA-T. Additionally both models were re-sensitized to GDC-0941 by blocking downstream signaling of the MAPK pathway. These preclinical data may provide rationale for combination therapy with PI3K inhibitors in the clinic. Citation Format: Kyle A. Edgar, Ling Hwu, Kimberly Walter, Mark Lackner, Lori S. Friedman, Jeffrey J. Wallin. Mechanisms of acquired resistance to the PI3K inhibitor GDC-0941 in breast cancer cell lines. [abstract]. In: Proceedings of the AACR Special Conference: Targeting the PI3K-mTOR Network in Cancer; Sep 14-17, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(7 Suppl):Abstract nr B37.