A multicenter phase I trial of PX-866, an oral irreversible phosphatidylinositol 3-kinase inhibitor, in patients with advanced solid tumors

Phosphoinositide 3-kinase (PI3K) pathway inhibitors in solid tumors: From laboratory to patients

The phosphoinositide 3-kinase (PI3K) pathway is an intracellular signaling pathway that has regulatory roles in cell survival, proliferation, and differentiation, and a critical role in tumorigenesis. In cancer, multiple studies have investigated the therapeutic targeting of the PI3K pathway, and multiple inhibitors targeting PI3K and its isoforms, protein kinase B/AKT, mammalian target of rapamycin (mTOR), and other pathway proteins have been developed. For the treatment of solid tumors, only allosteric mTOR inhibitors, such as everolimus and temsirolimus, are currently approved for clinical use. This review describes the PI3K inhibitors that have progressed from the laboratory to late-stage clinical trials, and discusses the challenges that have prevented other compounds from doing the same. Challenges to the therapeutic effectiveness of some PI3K inhibitors include the absence of reliable and effective biomarkers, their limited efficacy as single agents, insufficient development of rational therapeutic combinations, the use of schedules with a variety of off-target effects, and suboptimal therapeutic exposures. Therefore, with regard to PI3K inhibitors currently in late-stage clinical trials, the identification of appropriate biomarkers of efficacy and the development of optimal combination regimens and dosing schedules are likely to be important for graduation into clinical practice.

Activation of phosphoinositide 3-kinase/Akt/mechanistic target of rapamycin pathway and response to everolimus in endocrine receptor-positive metastatic breast cancer - A retrospective pilot analysis and viewpoint

Introduction:

Biomarkers predictive of response to mechanistic target of rapamycin (mTOR) inhibitor, everolimus, in endocrine receptor (ER)-positive metastatic breast cancer (MBC) are a work in progress. We evaluated the feasibility of directly measuring mTOR activity and phosphatase and tensin homolog (PTEN) expression and correlating their expression with response and survival.

Materials and Methods:

MBC patients who received everolimus with endocrine therapy (ET) after progression on an aromatase inhibitor and had adequate tissue preservation for estimation of mTOR activity and PTEN expression were selected for analysis from a prospectively maintained database. Progression-free survival (PFS) and overall survival (OS) were estimated by Kaplan–Meier method, and correlation between mTOR activity and PTEN expression with survival was done by log-rank test.

Results:

Thirteen ER-positive MBC patients were available for analysis. PTEN expression was lost in 11/13 (84.6%) patients and retained in 2/13 patients (15.4%). mTOR activity was absent in four patients (30.7%), weak in six patients (46.1%), and moderate in 3 patients (23.2%). Median PFS for the entire population was 2.5 months while median OS was not reached. Patients with an absent mTOR activity showed a longer PFS (5 vs. 1.5 vs. 2 months) than those with weak and moderate activity, respectively (P = 0.043). There was no correlation between loss of PTEN expression and PFS.

Conclusions:

Measurement of direct mTOR activity in patients with MBC receiving everolimus/ET combination appears feasible. Absent mTOR activity may predict for longer PFS with everolimus-ET combination and requires further study.

Advances in the treatment of advanced oestrogen-receptor-positive breast cancer

Oestrogen-receptor-positive breast cancer is the most common subtype of breast cancer. Endocrine therapies that target the dependence of this subtype on the oestrogen receptor have substantial activity, yet the development of resistance to therapy is inevitable in advanced cancer. Major progress has been made in identifying the drivers of oestrogen-receptor-positive breast cancer and the mechanisms of resistance to endocrine therapy. This progress has translated into major advances in the treatment of advanced breast cancer, with several targeted therapies that enhance the efficacy of endocrine therapy; inhibitors of mTOR and inhibitors of the cyclin-dependent kinases CDK4 and CDK6 substantially improve progression-free survival. A new wave of targeted therapies is being developed, including inhibitors of PI3K, AKT, and HER2, and a new generation of oestrogen-receptor degraders. Considerable challenges remain in patient selection, deciding on the most appropriate order in which to administer therapies, and establishing whether cross-resistance occurs between therapies.

Recent advances in the use of PI3K inhibitors for glioblastoma multiforme: current preclinical and clinical development

Glioblastoma multiforme (GBM) is the most common and aggressive malignant primary tumor in the central nervous system. One of the most widely used chemotherapeutic drugs for GBM is temozolomide, which is a DNA-alkylating agent and its efficacy is dependent on MGMT methylation status. Little progress in improving the prognosis of GBM patients has been made in the past ten years, urging the development of more effective molecular targeted therapies. Hyper-activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway is frequently found in a variety of cancers including GBM, and it plays a central role in the regulation of tumor cell survival, growth, motility, angiogenesis and metabolism. Numerous PI3K inhibitors including pan-PI3K, isoform-selective and dual PI3K/mammalian target of rapamycin (mTOR) inhibitors have exhibited favorable preclinical results and entered clinical trials in a range of hematologic malignancies and solid tumors. Furthermore, combination of inhibitors targeting PI3K and other related pathways may exert synergism on suppressing tumor growth and improving patients' prognosis. Currently, only a handful of PI3K inhibitors are in phase I/II clinical trials for GBM treatment. In this review, we focus on the importance of PI3K/Akt pathway in GBM, and summarize the current development of PI3K inhibitors alone or in combination with other inhibitors for GBM treatment from preclinical to clinical studies.

Therapeutic Potential of Targeting PI3K/AKT Pathway in Treatment of Colorectal Cancer: Rational and Progress

PI3K/AKT/mTOR signaling pathway is one of the key dysregulated pathways in different tumor types, including colorectal cancer (CRC). Activation of this pathway is shown to be related with cellular transformation, tumor progression, cell survival, and drug resistance. There is growing body of data evaluating the value of PI3K/AKT/mTOR inhibitors in CRC (e.g., BEZ235, NVP-BEZ235, OSI-027, everolimus, MK-2206, KRX-0401, BYL719, and BKM120). This report summarizes the current knowledge about PI3K/AKT pathway and its cross talk with ERK/MAPK and mTOR pathways with particular emphasis on the value of targeting this pathway as a potential therapeutic target in treatment of colorectal cancer. J. Cell. Biochem. 119: 2460-2469, 2018. © 2017 Wiley Periodicals, Inc.

A First-in-Human, Phase I, Dose-Escalation Study of TAK-117, a Selective PI3Kα Isoform Inhibitor, in Patients with Advanced Solid Malignancies

Purpose: To evaluate the safety, MTD, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of TAK-117 (MLN1117/INK1117), an investigational PI3Kα-selective inhibitor, in patients with advanced solid tumors.Experimental Design: Seventy-one patients received oral TAK-117 once daily [100-300 mg (n = 24)] or 3 days per week [Monday-Wednesday-Friday (MWF), 200-1,200 mg (n = 27); Monday-Tuesday-Wednesday (MTuW), 200-900 mg (n = 20)], in 21-day cycles. Dose escalation proceeded via a 3 + 3 design.Results: TAK-117 once-daily dosing was associated with dose-limiting grade ≥3 alanine/aspartate aminotransferase (ALT/AST) elevations, resulting in a narrow range of tolerable doses (100-150 mg once daily). With MWF/MTuW dosing, no dose-limiting ALT/AST elevations occurred until the MTD of 900 mg; total weekly dose was 2.6-fold that of 150 mg once daily. Drug-related grade ≥3 adverse events occurred in 25%/22%/35% (including hyperglycemia in 0%/7%/15%) of once-daily/MWF/MTuW patients. TAK-117 (100-1,200 mg) exhibited moderately fast oral absorption, a generally dose proportional increase in exposure, and plasma half-life of approximately 11 hours. Total weekly exposures with 900 mg MWF/MTuW dosing were approximately 4 times greater than with 150 mg once daily. Skin pS6 expression was suppressed at ≥200 mg. There were 3/1/0 partial responses (once daily/MWF/MTuW) and 5/7/5 patients had stable disease lasting ≥3 months (all PIK3CA mutated).Conclusions: Intermittent dosing of TAK-117 had an acceptable safety profile and enabled higher doses and total weekly exposures versus once-daily dosing. Although the potential for TAK-117 as single-agent therapy appears limited, further evaluation in combination approaches for advanced solid tumors is warranted. Clin Cancer Res; 23(17); 5015-23. ©2017 AACR.

A phase I dose-escalation study of the safety and pharmacokinetics of a tablet formulation of voxtalisib, a phosphoinositide 3-kinase inhibitor, in patients with solid tumors

Background Voxtalisib, a PI3K/mTOR inhibitor, has shown antitumor activity in capsule formulation in patients with solid tumors. This Phase I study assessed safety and pharmacokinetics of voxtalisib administered as immediate-release tablets in patients with solid tumors (NCT01596270). Methods A "3 + 3" dose escalation design was used. Adverse events (AEs), pharmacokinetics (PK), food effect and tumor response were evaluated. Results Thirty-two patients received voxtalisib doses ranging from 50 mg to 70 mg once daily (QD) and 17 patients received voxtalisib doses ranging from 30 mg to 50 mg twice daily (BID), for two 28-day cycles. Dose-limiting toxicities (DLTs) were Grade 3 fatigue (two patients at 70 mg QD, one patient at 40 mg BID) and Grade 3 rash (two patients at 50 mg BID). The maximum tolerated dose (MTD) was 60 mg for QD and 40 mg for BID regimens. Common treatment-emergent AEs were diarrhea (41%), nausea (37%) and fatigue (33%). Voxtalisib appeared to follow linear PK, with a general increase in plasma exposure with dose and no significant accumulation. Administration with food caused a slight decrease in exposure; however, given the high variability observed in the exposure parameters, this should be interpreted with caution. Best response was stable disease in 29% and 50% of patients (QD and BID regimens, respectively). Conclusions The safety profile of voxtalisib tablets at the MTD in patients with solid tumors was consistent with that observed with voxtalisib capsules. Given the limited activity observed across multiple clinical trials, no further trials of voxtalisib are planned.

AR Signaling and the PI3K Pathway in Prostate Cancer

Prostate cancer is a leading cause of cancer-related death in men worldwide. Aberrant signaling in the androgen pathway is critical in the development and progression of prostate cancer. Despite ongoing reliance on androgen receptor (AR) signaling in castrate resistant disease, in addition to the development of potent androgen targeting drugs, patients invariably develop treatment resistance. Interactions between the AR and PI3K pathways may be a mechanism of treatment resistance and inhibitors of this pathway have been developed with variable success. Herein we outline the role of the PI3K pathway in prostate cancer and, in particular, its association with androgen receptor signaling in the pathogenesis and evolution of prostate cancer, as well as a review of the clinical utility of PI3K targeting.

Enhanced anti-tumour activity of the combination of the novel MEK inhibitor WX-554 and the novel PI3K inhibitor WX-037

PURPOSE

Tumours frequently have defects in multiple oncogenic pathways, e.g. MAPK and PI3K signalling pathways, and combinations of targeted therapies may be required for optimal activity. This study evaluated the novel MEK inhibitor WX-554 and the novel PI3K inhibitor WX-037, as single agents and in combination, in colorectal carcinoma cell lines and tumour xenograft-bearing mice.

METHODS

In vitro growth inhibition, survival and signal transduction were measured using the Sulforhodamine B, clonogenic and Western blotting assays, respectively, in HCT116 and HT29 cell lines. In vivo anti-tumour efficacy and pharmacokinetic properties were assessed in HCT116 and HT29 human colorectal cancer xenograft tumour-bearing mice.

RESULTS

The combination of WX-554 and WX-037 exhibited marked synergistic growth inhibition in vitro, which was associated with increased cytotoxicity and enhanced inhibition of ERK and S6 phosphorylation, compared to either agent alone. Pharmacokinetic analyses indicated that there was no PK interaction between the two drugs at low doses, but that at higher doses, WX-037 may delay the tumour uptake of WX-554. In vivo efficacy studies revealed that the combination of WX-037 and WX-554 was non-toxic and exhibited marked tumour growth inhibition greater than observed with either agent alone.

CONCLUSION

These studies show for the first time that combination treatment with the novel MEK inhibitor WX-554 and the novel PI3K inhibitor WX-037 can induce synergistic growth inhibition in vitro, which translates into enhanced anti-tumour efficacy in vivo.

Clinical Implementation of Novel Targeted Therapeutics in Advanced Breast Cancer

The majority of advanced breast cancers have genetic alterations that are potentially targetable with drugs. Through initiatives such as The Cancer Genome Atlas (TCGA) and the International Cancer Genome Consortium (ICGC), data can be mined to provide context for next-generation sequencing (NGS) results in the landscape of advanced breast cancer. Therapies for targets other than estrogen receptor alpha (ER) and HER2, such as cyclin-dependent kinases CDK4 and CDK6, were recently approved based on efficacy in patient subpopulations, but no predictive biomarkers have been found, leaving clinicians to continue a trial-and-error approach with each patient. Next-generation sequencing identifies potentially actionable alterations in genes thought to be drivers in the cancerous process including phosphatidylinositol 3-kinase (PI3K), AKT, fibroblast growth factor receptors (FGFRs), and mutant HER2. Epigenetically directed and immunologic therapies have also shown promise for the treatment of breast cancer via histone deacetylases (HDAC) 1 and 3, programmed T cell death 1 (PD-1), and programmed T cell death ligand 1 (PD-L1). Identifying biomarkers to predict primary resistance in breast cancer will ultimately affect clinical decisions regarding adjuvant therapy in the first-line setting. However, the bulk of medical decision-making is currently made in the secondary resistance setting. Herein, we review the clinical potential of PI3K, AKT, FGFRs, mutant HER2, HDAC1/3, PD-1, and PD-L1 as therapeutic targets in breast cancer, focusing on the rationale for therapeutic development and the status of clinical testing. J. Cell. Biochem. 117: 2454-2463, 2016. © 2016 Wiley Periodicals, Inc.

Puquitinib mesylate, an inhibitor of phosphatidylinositol 3-kinase p110δ, for treating relapsed or refractory non-Hodgkin's lymphoma

Objectives

To determine the safety of Puquitinib Mesylate (XC-302), an oral inhibitor of phosphatidylinositol 3-kinase, in treating relapsed or refractory non-Hodgkin's lymphoma (NHL).

Methods

Between October 2013 and July 2015, 21 patients from Sun Yat-sen University Cancer Center were treated twice daily on each day of a 28-day cycle (median number of cycles, 2; maximum, 20) with XC-302 at a post prandial dose of 25 mg, 37.5 mg, or 50 mg. Adverse events (AEs), AUC_last and C_max, response rates, and overall survival were assessed.

Results

Patients had received a median (range) of 1 (1 to 3) previous cancer treatments. At the latest follow-up, two patients were still benefitting from the study. The most common drug-related AEs were elevations in alanine transaminase (ALT, 14 of 21 patients) and aspartate transaminase (AST, 7 of 21 patients). Four patients, both in the-50-mg group, had dose-limiting toxicities, and therapy was discontinued in a fifth because of persistent abnormal liver function. The overall response rate was 2 of19. Serum concentrations of XC-302 increased in a dose-dependent pattern. Median progression-free survival in all patients was 1.9 (95% CI, 1.7 to 2.0) months.

Conclusion

XC-302 has an acceptable safety profile and offers potential therapeutic value to patients with relapsed or refractory non-Hodgkin lymphoma.

Gastric cancer: somatic genetics as a guide to therapy

Gastric cancer is the leading cause of cancer-related mortality across the world, with poor prognosis and a median overall survival of ≤12 months for advanced stage gastric cancer. Environmental, genetic and other predisposing factors contribute to the development of gastric cancer and a predominant factor was found to be infection of Helicobacter pylori Advances in understanding the deranged signalling pathways that are critical for normal cellular homeostasis helped in the development of novel drugs that target specific proteins and pathways to curtail the growth of gastric cancer. Genetic studies revealed several single nucleotide polymorphisms, chromosomal aberrations and epigenetic alterations that likely play a major role in elevating the susceptibility to develop gastric cancer. Methylation pattern of specific genes may likely prove to be a valid biomarker for early detection of gastric cancer, but much progress is needed to establish specific markers. Important developments have been made in targeting human epidermal growth factor receptor-2 and vascular endothelial growth factor receptor 2 for treating advanced gastro-oesophageal junction cancer, using specific monoclonal antibodies. Lack of efficacy with regard to targeting other signalling pathways including mesenchymal-epithelial transition/hepatocyte growth factor and mammalian target of rapamycin is probably due to suboptimal patient selection for these clinical trials, which is probably due to the lack of appropriate biomarkers, to decide on responsive patient population. Besides the development of antagonists for the cell growth-related signalling pathways, advances are also being made to tackle gastric cancer by immunotherapies, targeting immune check-points, which may hold promise for better treatment options in future.

Novel drugs that target the metabolic reprogramming in renal cell cancer

Molecular profiling studies of tumor tissue from patients with clear cell renal cell cancer (ccRCC) have revealed extensive metabolic reprogramming in this disease. Associations were found between metabolic reprogramming, histopathologic Fuhrman grade, and overall survival of patients. Large-scale genomics, proteomics, and metabolomic analyses have been performed to identify the molecular players in this process. Genes involved in glycolysis, the pentose phosphate pathway, glutamine metabolism, and lipogenesis were found to be upregulated in renal cell cancer (RCC) specimens as compared to normal tissue. Preclinical research indicates that mutations in VHL, FBP1, and the PI3K-AKT-mTOR pathway drives aerobic glycolysis through transcriptional activation of the hypoxia-inducible factors (HIF). Mechanistic studies revealed glutamine as an important source for de novo fatty acid synthesis through reductive carboxylation. Amplification of MYC drives reductive carboxylation. In this review, we present a detailed overview of the metabolic changes in RCC in conjunction with potential novel therapeutics. We discuss preclinical studies that have investigated targeted agents that interfere with various aspects of tumor cell metabolism and emphasize their impact specifically on glycolysis, lipogenesis, and tumor growth. Furthermore, we describe a number of phase 1 and 2 clinical trials that have been conducted with these agents.

Phase I safety and pharmacokinetic dose-escalation study of pilaralisib polymorph E, a phosphoinositide 3-kinase inhibitor in tablet formulation, in patients with solid tumors or lymphoma

PURPOSE

Pilaralisib (SAR245408), a pan-class I PI3K inhibitor, has been investigated in Phase I/II trials in several solid tumors and lymphomas in capsule and tablet formulations of polymorph A (capsule-A and tablet-A). This Phase I study was conducted to determine the recommended Phase II dose (RP2D) of a more thermodynamically stable form of pilaralisib (polymorph E), in tablet formulation (tablet-E), in patients with advanced solid tumors or relapsed/refractory lymphoma.

METHODS

A modified '3 + 3' dose-escalation design was employed. Patients received pilaralisib once daily (QD; starting dose 400 mg) for two 28-day cycles. Primary endpoints were safety and pharmacokinetics (PK). Exploratory endpoints were pharmacodynamics and efficacy.

RESULTS

Eighteen patients were enrolled: Six patients received pilaralisib 400 mg QD and 12 patients received pilaralisib 600 mg QD. Two patients in the 600 mg QD cohort had dose-limiting toxicities (DLTs) (one patient with Grade 3 maculopapular rash and one patient with Grade 3 generalized rash and Grade 4 lipase increased). The most frequently occurring treatment-related, treatment-emergent adverse events were decreased appetite (22 %), dry skin (22 %), nausea (22 %) and vomiting (22 %). In PK analyses, individual exposures observed with 600 mg tablet-E were within the range of data at steady state from previous studies of 400 mg tablet-A and 600 mg capsule-A. Five patients (28 %) had stable disease as best response.

CONCLUSIONS

With pilaralisib tablet-E, the RP2D was 600 mg QD, drug exposure was similar to the 400 mg tablet-A and 600 mg capsule-A formulations, and safety was consistent with the known safety profile of pilaralisib.

The Inositide Signaling Pathway As a Target for Treating Gastric Cancer and Colorectal Cancer

Gastric cancer and colorectal cancer are the leading cause of cancer mortality and have a dismal prognosis. The introduction of biological agents to treat these cancers has resulted in improved outcomes, and combination chemotherapy with targeted agents and conventional chemotherapeutic agents is regarded as standard therapy. Additional newly clarified mechanisms of oncogenesis and resistance to targeted agents require the development of new biologic agents. Aberrant activation of the inositide signaling pathway by a loss of function PTEN mutation or gain of function mutation/amplification of PIK3CA is an oncogenic mechanism in gastric cancer and colorectal cancer. Clinical trials with biologic agents that target the inositide signaling pathway are being performed to further improve treatment outcomes of patients with advanced gastric cancer and metastatic colorectal cancer (CRC). In this review we summarize the inositide signaling pathway, the targeted agents that inhibit abnormal activation of this signaling pathway and the clinical trials currently being performed in patients with advanced or metastatic gastric cancer and metastatic CRC using these targeted agents.

A Randomized, Phase II Trial of Cetuximab With or Without PX-866, an Irreversible Oral Phosphatidylinositol 3-Kinase Inhibitor, in Patients With Metastatic Colorectal Carcinoma

BACKGROUND

The phosphotidylinositol-3 kinase (PI3K)/serine-threonine kinase/mammalian target of rapamycin signaling pathway is frequently altered in colorectal cancer (CRC). PX-866 is an oral, irreversible, pan-isoform inhibitor of PI3K. This randomized phase II study evaluated cetuximab with or without PX-866 in patients with metastatic, anti-epidermal growth factor receptor-naive, KRAS codon 12 and 13 wild-type CRC.

PATIENTS AND METHODS

Patients with metastatic CRC who had received both oxaliplatin and irinotecan were randomized (1:1) to cetuximab (400 mg/m² loading then 250 mg/m² weekly) with or without PX-866 (8 mg orally daily; arms A and B, respectively). The primary endpoint was progression-free survival (PFS). Secondary endpoints included objective response rate, overall survival (OS), toxicity, and correlation of relevant biomarkers with efficacy outcomes.

RESULTS

A total of 85 patients were enrolled. The median PFS was 59 days versus 104 days for arms A (cetuximab + PX-866) and B (cetuximab alone), respectively (P = .77). OS between the 2 arms (266 vs. 333 days for arm A vs. B) were similar (P = .83). Overall toxicity, including treatment-related toxicity, was higher in arm A compared with arm B, especially in terms of all-grade nausea (66% vs. 37%), vomiting (50% vs. 29%), diarrhea (64% vs. 18%), and rash (66% vs. 37%). Grade 3 diarrhea occurred in 19% of patients in Arm A and 0% in Arm B. PIK3CA mutations and PTEN loss by immunohistochemistry were infrequently seen.

CONCLUSION

The addition of PX-866 to cetuximab did not improve PFS, objective response rate, or OS in patients with metastatic CRC. The combination arm had greater toxicity and may have been harmful in this study.

Enhancing the evaluation of PI3K inhibitors through 3D melanoma models

Targeted therapies for mutant BRAF metastatic melanoma are effective but not curative due to acquisition of resistance. PI3K signaling is a common mediator of therapy resistance in melanoma; thus, the need for effective PI3K inhibitors is critical. However, testing PI3K inhibitors in adherent cultures is not always reflective of their potential in vivo. To emphasize this, we compared PI3K inhibitors of different specificity in two- and three-dimensional (2D, 3D) melanoma models and show that drug response predictions gain from evaluation using 3D models. Our results in 3D demonstrate the anti-invasive potential of PI3K inhibitors and that drugs such as PX-866 have beneficial activity in physiological models alone and when combined with BRAF inhibition. These assays finally help highlight pathway effectors that could be involved in drug response in different environments (e.g. p4E-BP1). Our findings show the advantages of 3D melanoma models to enhance our understanding of PI3K inhibitors.

Suppression of mTOR pathway in solid tumors: lessons learned from clinical experience in renal cell carcinoma and neuroendocrine tumors and new perspectives

The PI3K-AKT-mTOR pathway plays role in the regulation of many cellular processes. Hyperactivation of mTOR signaling has been implicated in human carcinogenesis, representing an attractive target for cancer therapy. Among other cancer subtypes, renal cell carcinoma (RCC) and neuroendocrine tumors are relevant settings in which the deregulation of mTOR pathway is of crucial importance. Different mTOR-inhibitory agents have been developed in recent years. Temsirolimus is approved for advanced RCC; everolimus is registered for the treatment of advanced RCC, pancreatic neuroendocrine tumors and postmenopausal, hormone receptor-positive/HER2-negative, advanced breast cancer. This review is focused on the description of the clinical experience with mTOR-inhibitor agents for the treatment of advanced RCC and neuroendocrine tumors, followed by an excursus on the landscape of the ongoing research in this field.

Pharmacodynamic Biomarker Development for PI3K Pathway Therapeutics

The phosphatidylinositol 3-kinase (PI3K) signaling pathway is integral to many essential cell processes, including cell growth, differentiation, proliferation, motility, and metabolism. Somatic mutations and genetic amplifications that result in activation of the pathway are frequently detected in cancer. This has led to the development of rationally designed therapeutics targeting key members of the pathway. Critical to the successful development of these drugs are pharmacodynamic biomarkers that aim to define the degree of target and pathway inhibition. In this review, we discuss the pharmacodynamic biomarkers that have been utilized in early-phase clinical trials of PI3K pathway inhibitors. We focus on the challenges related to development and interpretation of these assays, their optimal integration with pharmacokinetic and predictive biomarkers, and future strategies to ensure successful development of PI3K pathway inhibitors within a personalized medicine paradigm for cancer.

Phase I Study of Apitolisib (GDC-0980), Dual Phosphatidylinositol-3-Kinase and Mammalian Target of Rapamycin Kinase Inhibitor, in Patients with Advanced Solid Tumors

PURPOSE

This first-in-human phase I trial assessed the safety, tolerability, and preliminary antitumor activity of apitolisib (GDC-0980), a dual inhibitor of class I PI3K, and mTOR kinases.

EXPERIMENTAL DESIGN

Once-daily oral apitolisib was administered to patients with solid tumors for days 1 to 21 or 1 to 28 of 28-day cycles. Pharmacokinetic and pharmacodynamic parameters were assessed.

RESULTS

Overall, 120 patients were treated at doses between 2 and 70 mg. The commonest ≥G3 toxicities related to apitolisib at the recommended phase 2 dose (RP2D) at 40 mg once daily included hyperglycemia (18%), rash (14%), liver dysfunction (12%), diarrhea (10%), pneumonitis (8%), mucosal inflammation (6%), and fatigue (4%). Dose-limiting toxicities (1 patient each) were G4 fasting hyperglycemia at 40 mg (21/28 schedule) and G3 maculopapular rash and G3 fasting hyperglycemia at 70 mg (21/28 schedule). The pharmacokinetic profile was dose-proportional. Phosphorylated serine-473 AKT levels were suppressed by ≥90% in platelet-rich plasma within 4 hours at the MTD (50 mg). Pharmacodynamic decreases in fluorodeoxyglucose positron emission tomography uptake of >25% occurred in 66% (21/32) of patients dosed at 40 mg once daily. Evidence of single-agent activity included 10 RECIST partial responses (PR; confirmed for peritoneal mesothelioma, PIK3CA mutant head-and-neck cancer, and three pleural mesotheliomas).

CONCLUSIONS

Apitolisib exhibited dose-proportional pharmacokinetics with target modulation at doses ≥16 mg. The RP2D was 40 mg once-daily 28/28 schedule; severe on-target toxicities were apparent at ≥40 mg, particularly pneumonitis. Apitolisib was reasonably tolerated at 30 mg, the selected dose for pleural mesothelioma patients given limited respiratory reserve. Modest but durable antitumor activity was demonstrated. Clin Cancer Res; 22(12); 2874-84. ©2016 AACR.

Other targeted drugs in melanoma

Targeted therapy drugs are developed against specific molecular alterations on cancer cells. Because they are "targeted" to the tumor, these therapies are more effective and better tolerated than conventional therapies such as chemotherapy. In the last decade, great advances have been made in understanding of melanoma biology and identification of molecular mechanisms involved in malignant transformation of cells. The identification of oncogenic mutated kinases involved in this process provides an opportunity for development of new target therapies. The dependence of melanoma on BRAF-mutant kinase has provided an opportunity for development of mutation-specific inhibitors with high activity and excellent tolerance that are now being used in clinical practice. This marked a new era in the treatment of metastatic melanoma and much research is now ongoing to identify other "druggable" kinases and transduction signaling networking. It is expected that in the near future the spectrum of target drugs for melanoma treatment will increase. Herein, we review the most relevant potential novel drugs for melanoma treatment based on preclinical data and the results of early clinical trials.

Targeting the PI3K/Akt signaling pathway in gastric carcinoma: A reality for personalized medicine?

Frequent activation of phosphatidylinositol-3 kinases (PI3K)/Akt/mTOR signaling pathway in gastric cancer (GC) is gaining immense popularity with identification of mutations and/or amplifications of PIK3CA gene or loss of function of PTEN, a tumor suppressor protein, to name a few; both playing a crucial role in regulating this pathway. These aberrations result in dysregulation of this pathway eventually leading to gastric oncogenesis, hence, there is a need for targeted therapy for more effective anticancer treatment. Several inhibitors are currently in either preclinical or clinical stages for treatment of solid tumors like GC. With so many inhibitors under development, further studies on predictive biomarkers are needed to measure the specificity of any therapeutic intervention. Herein, we review the common dysregulation of PI3K/Akt/mTOR pathway in GC and the various types of single or dual pathway inhibitors under development that might have a superior role in GC treatment. We also summarize the recent developments in identification of predictive biomarkers and propose use of predictive biomarkers to facilitate more personalized cancer therapy with effective PI3K/Akt/mTOR pathway inhibition.

Complications of hyperglycaemia with PI3K-AKT-mTOR inhibitors in patients with advanced solid tumours on Phase I clinical trials

Background:

PI3K–AKT–mTOR inhibitors (PAMi) are promising anticancer treatments. Hyperglycaemia is a mechanism-based toxicity of these agents and is becoming increasingly important with their use in larger numbers of patients.

Methods:

Retrospective case-control study comparing incidence and severity of hyperglycaemia (all grades) between a case group of 387 patients treated on 18 phase I clinical trials with PAMi (78 patients with PI3Ki, 138 with mTORi, 144 with AKTi and 27 with PI3K/mTORi) and a control group of 109 patients treated on 10 phase I clinical trials with agents not directly targeting the PAM pathway. Diabetic patients were excluded in both groups.

Results:

The incidence of hyperglycaemia was not significantly different between cases and controls (86.6% vs 80.7%, respectively, P=0.129). However, high grade (grade 3–4) hyperglycaemia was more frequent in the PAMi group than in controls (6.7% vs 0%, respectively, P=0.005). The incidence of grade 3–4 hyperglycaemia was greater with AKT and multikinase inhibitors compared with other PAMi (P<0.001). All patients with high-grade hyperglycaemia received antihyperglycemic treatment and none developed severe metabolic complications (diabetic ketoacidosis or hyperosmolar hyperglycemic nonketotic state). High-grade hyperglycaemia was the cause of permanent PAMi discontinuation in nine patients.

Conclusions:

PI3K–AKT–mTOR inhibitors are associated with small (6.7%) but statistically significant increased risk of high-grade hyperglycaemia compared with non-PAM targeting agents. However, PAMi-induced hyperglycaemia was not found to be associated with severe metabolic complications in this non-diabetic population of patients with advanced cancers.

Adipose tissue dysfunction and its effects on tumor metabolism

Growing by an alarming rate in the Western world, obesity has become a condition associated with a multitude of diseases such as diabetes, metabolic syndrome and various cancers. Generally viewed as an abnormal accumulation of hypertrophied adipocytes, obesity is also a poor prognostic factor for recurrence and chemoresistance in cancer patients. With more than two-thirds of the adult population in the United States considered clinically overweight or obese, it is critical that the relationship between obesity and cancer is further emphasized and elucidated. Adipocytes are highly metabolically active cells, which, through release of adipokines and cytokines and activation of endocrine and paracrine pathways, affect processes in neighboring and distant cells, altering their normal homeostasis. This work will examine specifically how adipocyte-derived factors regulate the cellular metabolism of malignant cells within the tumor niche. Briefly, tumor cells undergo metabolic pressure towards a more glycolytic and hypoxic state through a variety of metabolic regulators and signaling pathways, i.e., phosphoinositol-3 kinase (PI3K), hypoxia-inducible factor-1 alpha (HIF-1α), and c-MYC signaling. Enhanced glycolysis and high lactate production are hallmarks of tumor progression largely because of a process known as the Warburg effect. Herein, we review the latest literature pertaining to the body of work on the interactions between adipose and tumor cells, and underlining the changes in cancer cell metabolism that have been targeted by the currently available treatments.

Suppression of esophageal tumor growth and chemoresistance by directly targeting the PI3K/AKT pathway

Esophageal cancer is the sixth most common cause of cancer-related deaths worldwide. Novel therapeutic intervention is urgently needed for this deadly disease. The functional role of PI3K/AKT pathway in esophageal cancer is little known. In this study, our results from 49 pairs of human esophageal tumor and normal specimens demonstrated that AKT was constitutively active in the majority (75.5%) of esophageal tumors compared with corresponding normal tissues. Inhibition of the PI3K/AKT pathway with specific inhibitors, wortmannin and LY294002, significantly reduced Bcl-xL expression, induced caspase-3-dependent apoptosis, and repressed cell proliferation and tumor growth in vitro and in vivo without obvious toxic effects. Moreover, significantly higher expression level of p-AKT was observed in fluorouracil (5-FU)-resistant esophageal cancer cells. Inactivation of PI3K/AKT pathway markedly increased the sensitivity and even reversed acquired resistance of esophageal cancer cells to chemotherapeutic drugs in vitro. More importantly, the resistance of tumor xenografts derived from esophageal cancer cells with acquired 5-FU resistance to chemotherapeutic drugs was significantly abrogated by wortmannin treatment in animals. In summary, our data support PI3K/AKT as a valid therapeutic target and strongly suggest that PI3K/AKT inhibitors used in conjunction with conventional chemotherapy may be a potentially useful therapeutic strategy in treating esophageal cancer patients.

Toward a Cancer Drug of Fungal Origin

Although fungi produce highly structurally diverse metabolites, many of which have served as excellent sources of pharmaceuticals, no fungi-derived agent has been approved as a cancer drug so far. This is despite a tremendous amount of research being aimed at the identification of fungal metabolites with promising anticancer activities. This review discusses the results of clinical testing of fungal metabolites and their synthetic derivatives, with the goal to evaluate how far we are from an approved cancer drug of fungal origin. Also, because in vivo studies in animal models are predictive of the efficacy and toxicity of a given compound in a clinical situation, literature describing animal cancer testing of compounds of fungal origin is reviewed as well. Agents showing the potential to advance to clinical trials are also identified. Finally, the technological challenges involved in the exploitation of fungal biodiversity and procurement of sufficient quantities of clinical candidates are discussed, and potential solutions that could be pursued by researchers are highlighted.

Drugging PI3K in cancer: refining targets and therapeutic strategies

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PI3K is an important target for innovative anticancer drug development and precision medicine.

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Over 30 small molecule PI3K inhibitors are currently in clinical trial testing.

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These drugs include dual PI3K/mTOR, pan-Class I PI3K and isoform-selective PI3K inhibitors.

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The PI3Kδ inhibitor idelalisib has received FDA approval for the treatment of B-cell malignancies.

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Drug resistance, patient selection and development of targeted combinations remain challenges.

The phosphatidylinositol-3 kinase (PI3K) pathway is one of the most frequently activated pathogenic signalling routes in human cancers, making it a rational and important target for innovative anticancer drug development and precision medicine. The three main classes of PI3K inhibitors currently in clinical testing comprise dual pan-Class I PI3K/mTOR inhibitors, pan-Class I PI3K inhibitors lacking significant mTOR activity and isoform-selective PI3K inhibitors. A major step forward in recent years is the progression of over 30 small molecule PI3K inhibitors into clinical trials and the first regulatory approval of the PI3Kδ inhibitor idelalisib for multiple B-cell malignancies. This review article focuses on the progress made in the discovery and development of novel PI3K inhibitors, with an emphasis on antitumour activity and tolerability profiles for agents that have entered clinical trials. We also discuss the key issues of drug resistance, patient selection approaches and rational targeted combinations. Finally, we envision the future development and use of PI3K inhibitors for the treatment of patients with a range of malignancies.

Targeting phosphatidylinositol-3-kinase pathway for the treatment of Philadelphia-negative myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are a diverse group of chronic hematological disorders that involve unregulated clonal proliferation of white blood cells. Sevearl of them are associated with mutations in receptor tyrosine kinases or cytokine receptor associated tyrosine kinases rendering them independent of cytokine-mediated regulation. Classically they have been broadly divided into BCR-ABL1 fusion + ve (Ph + ve) or -ve (Ph-ve) MPNs. Identification of BCR-ABL1 tyrosine kinase as a driver of chronic myeloid leukemia (CML) and successful application of small molecule inhibitors of the tyrosine kinases in the clinic have triggered the search for kinase dependent pathways in other Ph-ve MPNs. In the past few years, identification of mutations in JAK2 associated with a majority of MPNs raised the hopes for similar success with specific targeting of JAK2. However, targeting JAK2 kinase activity has met with limited success. Subsequently, mutations in genes other than JAK2 have been identified. These mutations specifically associate with certain MPNs and can drive cytokine independent growth. Therefore, targeting alternate molecules and pathways may be more successful in management of MPNs. Among other pathways, phosphatidylinositol -3 kinase (PI3K) has emerged as a promising target as different cell surface receptor induced signaling pathways converge on the PI3K signaling axis to regulate cell metabolism, growth, proliferation, and survival. Herein, we will review the clinically relevant inhibitors of the PI3K pathway that have been evaluated or hold promise for the treatment of Ph-ve MPNs.

Disentangling the Complexity of HGF Signaling by Combining Qualitative and Quantitative Modeling

Signaling pathways are characterized by crosstalk, feedback and feedforward mechanisms giving rise to highly complex and cell-context specific signaling networks. Dissecting the underlying relations is crucial to predict the impact of targeted perturbations. However, a major challenge in identifying cell-context specific signaling networks is the enormous number of potentially possible interactions. Here, we report a novel hybrid mathematical modeling strategy to systematically unravel hepatocyte growth factor (HGF) stimulated phosphoinositide-3-kinase (PI3K) and mitogen activated protein kinase (MAPK) signaling, which critically contribute to liver regeneration. By combining time-resolved quantitative experimental data generated in primary mouse hepatocytes with interaction graph and ordinary differential equation modeling, we identify and experimentally validate a network structure that represents the experimental data best and indicates specific crosstalk mechanisms. Whereas the identified network is robust against single perturbations, combinatorial inhibition strategies are predicted that result in strong reduction of Akt and ERK activation. Thus, by capitalizing on the advantages of the two modeling approaches, we reduce the high combinatorial complexity and identify cell-context specific signaling networks.

First-in-Human Study of PF-05212384 (PKI-587), a Small-Molecule, Intravenous, Dual Inhibitor of PI3K and mTOR in Patients with Advanced Cancer

PURPOSE

To evaluate safety (primary endpoint), tolerability, pharmacokinetics, pharmacodynamic profile, and preliminary activity of the intravenous, pan-class I isoform PI3K/mTOR inhibitor PF-05212384 in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

Part 1 of this open-label phase I study was designed to estimate the maximum-tolerated dose (MTD) in patients with nonselected solid tumors, using a modified continual reassessment method to guide dose escalation. Objectives of part 2 were MTD confirmation and assessment of preliminary activity in patients with selected tumor types and PI3K pathway dysregulation.

RESULTS

Seventy-seven of the 78 enrolled patients received treatment. The MTD for PF-05212384, administered intravenously once weekly, was estimated to be 154 mg. The most common treatment-related adverse events (AE) were mucosal inflammation/stomatitis (58.4%), nausea (42.9%), hyperglycemia (26%), decreased appetite (24.7%), fatigue (24.7%), and vomiting (24.7%). The majority of patients treated at the MTD experienced only grade 1 treatment-related AEs. Grade 3 treatment-related AEs occurred in 23.8% of patients at the MTD. No treatment-related grade 4-5 AEs were reported at any dose level. Antitumor activity was noted in this heavily pretreated patient population, with two partial responses (PR) and an unconfirmed PR. Eight patients had long-lasting stable disease (>6 months). Pharmacokinetic analyses showed a biphasic concentration-time profile for PF-05212384 (half-life, 30-37 hours after multiple dosing). PF-05212384 inhibited downstream effectors of the PI3K pathway in paired tumor biopsies.

CONCLUSIONS

These findings demonstrate the manageable safety profile and antitumor activity of the PI3K/mTOR inhibitor PF-05212384, supporting further clinical development for patients with advanced solid malignancies.

Phase I Trial of the Pan-PI3K Inhibitor Pilaralisib (SAR245408/XL147) in Patients with Chronic Lymphocytic Leukemia (CLL) or Relapsed/Refractory Lymphoma

PURPOSE

This phase I expansion-cohort study evaluated the safety, pharmacokinetics, pharmacodynamics, and preliminary efficacy of the pan-PI3K inhibitor pilaralisib (SAR245408/XL147) in patients with chronic lymphocytic leukemia (CLL) or relapsed or refractory lymphoma.

PATIENTS AND METHODS

Patients were treated with the maximum tolerated dose of pilaralisib previously determined in patients with solid tumors (600 mg capsules once daily). Adverse events (AE) and response were evaluated. Plasma pharmacokinetics and pharmacodynamic effects on cytokines and chemokines were also assessed.

RESULTS

Twenty-five patients were included in the study: 10 with CLL and 15 with lymphoma. The most frequent AEs of any grade were diarrhea (92.0%), pyrexia (52.0%), and fatigue (44.0%). The most frequent grade ≥3 AEs were neutropenia (32.0%), diarrhea (20.0%), and anemia (16.0%). Pilaralisib exposure on cycle 1 day 28 was similar to exposure in patients with solid tumors. In patients with CLL, pilaralisib significantly reduced plasma levels of several cytokines and chemokines involved in B-cell trafficking. Five patients (50.0%) with CLL and 3 patients (20.0%) with lymphoma had a partial response. Six patients (60.0%) with CLL had nodal shrinkage ≥50%. Overall, 14 patients (56.0%; 7 patients with CLL and 7 patients with lymphoma) had progression-free survival ≥6 months.

CONCLUSIONS

Pilaralisib demonstrated an acceptable safety profile in patients with CLL and lymphoma, generally consistent with findings in patients with solid tumors. Single-agent pilaralisib showed preliminary clinical activity in patients with CLL and lymphoma, supporting further development.

A randomized, phase 2 trial of docetaxel with or without PX-866, an irreversible oral phosphatidylinositol 3-kinase inhibitor, in patients with relapsed or metastatic head and neck squamous cell cancer

INTRODUCTION

The phosphotidylinositol-3 kinase (PI3K)/serine-threonine kinase (AKT)/mammalian target of rapamycin (mTOR) signaling pathway is frequently altered in head and neck squamous cell cancer (HNSCC). PX-866 is an oral, irreversible, pan-isoform inhibitor of PI3K. Preclinical models revealed synergy with docetaxel and a phase 1 trial demonstrated tolerability of this combination. This randomized phase 2 study evaluated PX-866 combined with docetaxel in patients with advanced, refractory HNSCC.

METHODS

Patients with locally advanced, recurrent or metastatic HNSCC who had received at least one and no more than two prior systemic treatment regimens were randomized (1:1) to a combination of docetaxel (75mg/m(2) IV every 21days) with or without PX-866 (8mg PO daily; Arms A and B, respectively). The primary endpoint was progression free survival (PFS). Secondary endpoints included objective response rate (RR), overall survival (OS), toxicity, and correlation of biomarker analyses with efficacy outcomes.

RESULTS

85 patients were enrolled. There was a non-significant improvement in response rate in the combination arm (14% vs. 5%; P=0.13). Median PFS was 92days in Arm A and 82days in Arm B (P=0.42). There was no difference in OS between the two arms (263 vs. 195days; P=0.62). Grade 3 or higher adverse events were infrequent, but more common in the combination arm with respect to diarrhea (17% vs. 2%), nausea (7% vs. 0%), and febrile neutropenia (21% vs. 5%); grade 3 or higher anemia was more frequent in arm B (7% vs. 27%). PIK3CA mutations or PTEN loss were infrequently observed.

CONCLUSION

The addition of PX-866 to docetaxel did not improve PFS, RR, or OS in patients with advanced, refractory HNSCC without molecular pre-selection.

Genomic profiling toward precision medicine in non-small cell lung cancer: getting beyond EGFR

Lung cancer remains the leading cause of cancer-related mortality worldwide. The application of next-generation genomic technologies has offered a more comprehensive look at the mutational landscape across the different subtypes of non-small cell lung cancer (NSCLC). A number of recurrent mutations such as TP53, KRAS, and epidermal growth factor receptor (EGFR) have been identified in NSCLC. While targeted therapeutic successes have been demonstrated in the therapeutic targeting of EGFR and ALK, the majority of NSCLC tumors do not harbor these genomic events. This review looks at the current treatment paradigms for lung adenocarcinomas and squamous cell carcinomas, examining genomic aberrations that dictate therapy selection, as well as novel therapeutic strategies for tumors harboring mutations in KRAS, TP53, and LKB1 which, to date, have been considered “undruggable”. A more thorough understanding of the molecular alterations that govern NSCLC tumorigenesis, aided by next-generation sequencing, will lead to targeted therapeutic options expected to dramatically reduce the high mortality rate observed in lung cancer.

A randomized, phase 2 trial of Docetaxel with or without PX-866, an irreversible oral phosphatidylinositol 3-kinase inhibitor, in patients with relapsed or metastatic non-small-cell lung cancer

INTRODUCTION

The phosphotidylinositol-3 kinase/serine-threonine kinase (AKT)/mammalian target of rapamycin signaling pathway is frequently altered in non-small-cell lung cancer (NSCLC). PX-866 is an oral, irreversible, pan-isoform inhibitor of phosphotidylinositol-3 kinase. Preclinical models revealed synergy with docetaxel and a phase 1 trial demonstrated tolerability of this combination. This randomized phase 2 study evaluated PX-866 combined with docetaxel in patients with advanced, refractory NSCLC.

METHODS

Patients with locally advanced, recurrent, or metastatic NSCLC who had received at least one and no more than two prior systemic treatment regimens were randomized (1:1) to a combination of docetaxel (75 mg/m intravenous every 21 days) with or without PX-866 (8 mg orally daily; arms A and B, respectively). The primary end point was progression-free survival (PFS). Secondary end points included objective response rate, overall survival (OS), toxicity, and correlation of biomarker analyses with efficacy outcomes.

RESULTS

A total of 95 patients were enrolled. Median PFS was 2 months in arm A and 2.9 months in arm B (p = 0.65). Objective response rates were 6% and 0% in arms A and B, respectively (p = 0.4). There was no difference in OS between the two arms (7.0 versus 9.2 months; p = 0.9). Grade 3 or higher adverse events were infrequent, but more common in the combination arm with respect to diarrhea (7% versus 2%), nausea (4% versus 0%), and vomiting (7% versus 0%). PIK3CA mutations or PTEN loss were infrequently observed.

CONCLUSION

The addition of PX-866 to docetaxel did not improve PFS, response rate, or OS in patients with advanced, refractory NSCLC without molecular preselection.

Novel treatments for head and neck squamous cell carcinoma: preclinical identification and clinical investigation

Head and neck squamous cell carcinoma (HNSCC) is a common cancer worldwide. Classically, it is a disease related to tobacco and alcohol use; an increasing number of patients are being diagnosed with HNSCC caused by infection with the human papillomavirus. New deep-sequencing techniques have confirmed the importance of p53 and EGF receptor in HNSCC development, and have identified pathways of critical importance, such as PI3K/mTOR and NOTCH. Increasing knowledge of key molecular features has lead to new therapeutic avenues for HNSCC. Novel therapies under investigation in HNSCC include antibody and small molecule inhibitors of EGF receptor and its family members, PI3K inhibitors, antiangiogenic agents, immunotherapies and agents interacting with early developmental pathways such as Hedgehog.

Phase II study of PX-866 in recurrent glioblastoma

BACKGROUND

Glioblastoma (GBM) is the most aggressive malignancy of the central nervous system in adults. Increased activity of the phosphatidylinositol-3-OH kinase (PI3K) signal transduction pathway is common. We performed a phase II study using PX-866, an oral PI3K inhibitor, in participants with recurrent GBM.

METHODS

Patients with histologically confirmed GBM at first recurrence were given oral PX-866 at a dose of 8 mg daily. An MRI and clinical exam were done every 8 weeks. Tissue was analyzed for potential predictive markers.

RESULTS

Thirty-three participants (12 female) were enrolled. Median age was 56 years (range 35-78y). Eastern Cooperative Oncology Group performance status was 0-1 in 29 participants and 2 in the remainder. Median number of cycles was 1 (range 1-8). All participants have discontinued therapy: 27 for disease progression and 6 for toxicity (5 liver enzymes and 1 allergic reaction). Four participants had treatment-related serious adverse events (1 liver enzyme, 1 diarrhea, 2 venous thromboembolism). Other adverse effects included fatigue, diarrhea, nausea, vomiting, and lymphopenia. Twenty-four participants had a response of progression (73%), 1 had partial response (3%, and 8 (24%) had stable disease (median, 6.3 months; range, 3.1-16.8 months). Median 6-month progression-free survival was 17%. None of the associations between stable disease and PTEN, PIK3CA, PIK3R1, or EGFRvIII status were statistically significant.

CONCLUSIONS

PX-866 was relatively well tolerated. Overall response rate was low, and the study did not meet its primary endpoint; however, 21% of participants obtained durable stable disease. This study also failed to identify a statistically significant association between clinical outcome and relevant biomarkers in patients with available tissue.

Differential regulatory functions of three classes of phosphatidylinositol and phosphoinositide 3-kinases in autophagy

Autophagy is an evolutionarily conserved and exquisitely regulated self-eating cellular process with important biological functions. Phosphatidylinositol 3-kinases (PtdIns3Ks) and phosphoinositide 3-kinases (PI3Ks) are involved in the autophagic process. Here we aim to recapitulate how 3 classes of these lipid kinases differentially regulate autophagy. Generally, activation of the class I PI3K suppresses autophagy, via the well-established PI3K-AKT-MTOR (mechanistic target of rapamycin) complex 1 (MTORC1) pathway. In contrast, the class III PtdIns3K catalytic subunit PIK3C3/Vps34 forms a protein complex with BECN1 and PIK3R4 and produces phosphatidylinositol 3-phosphate (PtdIns3P), which is required for the initiation and progression of autophagy. The class II enzyme emerged only recently as an alternative source of PtdIns3P and autophagic initiator. However, the orthodox paradigm is challenged by findings that the PIK3CB catalytic subunit of class I PI3K acts as a positive regulator of autophagy, and PIK3C3 was thought to be an amino acid sensor for MTOR, which curbs autophagy. At present, a number of PtdIns3K and PI3K inhibitors, including specific PIK3C3 inhibitors, have been developed for suppression of autophagy and for clinical applications in autophagy-related human diseases.

First-in-human phase I study of pictilisib (GDC-0941), a potent pan-class I phosphatidylinositol-3-kinase (PI3K) inhibitor, in patients with advanced solid tumors

PURPOSE

This first-in-human dose-escalation trial evaluated the safety, tolerability, maximal-tolerated dose (MTD), dose-limiting toxicities (DLT), pharmacokinetics, pharmacodynamics, and preliminary clinical activity of pictilisib (GDC-0941), an oral, potent, and selective inhibitor of the class I phosphatidylinositol-3-kinases (PI3K).

PATIENTS AND METHODS

Sixty patients with solid tumors received pictilisib at 14 dose levels from 15 to 450 mg once-daily, initially on days 1 to 21 every 28 days and later, using continuous dosing for selected dose levels. Pharmacodynamic studies incorporated (18)F-FDG-PET, and assessment of phosphorylated AKT and S6 ribosomal protein in platelet-rich plasma (PRP) and tumor tissue.

RESULTS

Pictilisib was well tolerated. The most common toxicities were grade 1-2 nausea, rash, and fatigue, whereas the DLT was grade 3 maculopapular rash (450 mg, 2 of 3 patients; 330 mg, 1 of 7 patients). The pharmacokinetic profile was dose-proportional and supported once-daily dosing. Levels of phosphorylated serine-473 AKT were suppressed >90% in PRP at 3 hours after dose at the MTD and in tumor at pictilisib doses associated with AUC >20 h·μmol/L. Significant increase in plasma insulin and glucose levels, and >25% decrease in (18)F-FDG uptake by PET in 7 of 32 evaluable patients confirmed target modulation. A patient with V600E BRAF-mutant melanoma and another with platinum-refractory epithelial ovarian cancer exhibiting PTEN loss and PIK3CA amplification demonstrated partial response by RECIST and GCIG-CA125 criteria, respectively.

CONCLUSION

Pictilisib was safely administered with a dose-proportional pharmacokinetic profile, on-target pharmacodynamic activity at dose levels ≥100 mg and signs of antitumor activity. The recommended phase II dose was continuous dosing at 330 mg once-daily.

Novel chemotherapeutic approaches in adult high-grade gliomas

Despite decades of advancing science and clinical trials, average survival remains dismal for individuals with high-grade gliomas. Our understanding of the genetic and molecular aberrations that contribute to the aggressive nature of these tumors is continually growing, as is our ability to target such specific traits. Herein, we review the major classes of such targeted therapies, as well as the relevant clinical trial outcomes regarding their efficacy.

The role of the PI3K pathway in colorectal cancer

In the last decade treatment for colorectal cancer (CRC) has evolved with the addition of contemporary chemotherapy drugs and targeted therapies. Despite this progress, our drug armamentarium is by no means complete and modern molecular biology techniques have led to the identification of a number of 'druggable' targets. One of the most important current drug targets is the phosphatidyl-inositol 3-kinase (PI3K) pathway, which is frequently deregulated in patients with CRC. In vitro and in vivo data strongly support the clinical development of compounds affecting signal transduction via the PI3K pathway. In this review we outline the role of PI3K in the development and progression of CRC and discuss data from current and ongoing clinical trials targeting this pathway. In addition we make suggestions toward the optimization of future research in order to derive the maximum benefit for patients with CRC.

A randomized, phase II trial of cetuximab with or without PX-866, an irreversible oral phosphatidylinositol 3-kinase inhibitor, in patients with relapsed or metastatic head and neck squamous cell cancer

BACKGROUND

The phosphotidylinositol-3 kinase (PI3K)/serine-threonine kinase/mammalian target of rapamycin signaling pathway is frequently altered in head and neck squamous cell cancer (HNSCC). PX-866 is an oral, irreversible, pan-isoform inhibitor of PI3K. A phase I trial demonstrated tolerability of this combination. This randomized phase II study evaluated PX-866 combined with cetuximab in patients with advanced, refractory HNSCC.

METHODS

Patients with recurrent or metastatic HNSCC who had received at least one and no more than two prior systemic treatment regimens were randomized (1 : 1) to cetuximab with or without PX-866 (8 mg p.o. daily; arms A and B, respectively). The primary end point was progression-free survival (PFS). Secondary end points included objective response rate (ORR), overall survival (OS), toxicity, and correlation of key biomarkers with efficacy outcomes.

RESULTS

Eighty-three patients were enrolled. There was a similar response rate between arms (10% versus 7%). Of patients for whom tissue was assessable, 57% were human papillomavirus (HPV) positive. Median PFS was 80 days in both arms and there was no difference in OS between the two arms (211 versus 256 days). Overall toxicity was higher in arm A compared with arm B, especially in terms of nausea (53% versus 23%), vomiting (45% versus 15%), fatigue (43% versus 23%), diarrhea (40% versus 21%), and hypokalemia (25% versus 10%). Grade 3 or higher adverse events were infrequent, but more common in the combination arm although without a specific pattern. PIK3CA mutations were observed in 17% of the cases assessed, and PTEN loss was infrequently observed.

CONCLUSION

The addition of PX-866 to cetuximab did not improve PFS, RR, or OS in patients with advanced, refractory HNSCC enrolled without molecular preselection. In this contemporary cohort, HPV-positive patients comprised the majority, and neither HPV-positive nor HPV-negative patients derived clinical benefit for the addition of cetuximab plus PX-866.

Phase II study of the PI3K inhibitor pilaralisib (SAR245408; XL147) in patients with advanced or recurrent endometrial carcinoma

OBJECTIVE

Patients with endometrial carcinoma who progress after first-line chemotherapy have a poor prognosis. Phosphoinositide 3-kinase (PI3K) inhibitors are investigational treatment options in this setting. This study evaluated the efficacy and safety of the PI3K inhibitor pilaralisib (SAR245408; XL147) in advanced or recurrent endometrial carcinoma.

METHODS

This Phase II, multicenter, single-arm, open-label study enrolled patients with histologically confirmed advanced or recurrent endometrial carcinoma, who had received one or two prior chemotherapy regimens. Patients received pilaralisib 600mg capsules or 400mg tablets once daily. Primary endpoints were objective response rate (ORR), proportion of patients with progression-free survival (PFS) >6months and safety. Molecular profiling in archival tumor tissue and circulating tumor DNA were performed to identify molecular markers associated with response or resistance to pilaralisib.

RESULTS

67 patients were enrolled, of which 50 and 17 patients had received one or two prior regimens, respectively. Complete or partial tumor responses occurred in two patients each (ORR 6.0%); three had tumors with normal PTEN expression and PIK3R1 mutations and one had a tumor with PTEN protein deficiency. However, there was no association between molecular alterations and clinical activity. Rate of PFS>6months was 11.9%. The most commonly reported treatment-related adverse events (AEs) were rash (40.3%), diarrhea (37.3%) and fatigue (28.4%). The most commonly reported treatment-related grade ≥3 AEs were rash (9.0%), diarrhea (4.5%) and increased alanine aminotransferase (4.5%).

CONCLUSIONS

Pilaralisib was associated with a favorable safety profile and minimal antitumor activity in advanced or recurrent endometrial carcinoma.

Efficacy, safety, pharmacokinetics and pharmacodynamics of SAR245409 (voxtalisib, XL765), an orally administered phosphoinositide 3-kinase/mammalian target of rapamycin inhibitor: a phase 1 expansion cohort in patients with relapsed or refractory lymphoma

The maximum tolerated dose of SAR245409 (voxtalisib), a pan-class I phosphoinositide 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) inhibitor, was determined in a phase 1 dose-escalation study in advanced solid tumors. We report safety, pharmacokinetics (PK), pharmacodynamics and preliminary efficacy of SAR245409 capsules 50 mg twice daily in an expansion cohort of 16 patients with relapsed/refractory lymphoma. The most common treatment-related adverse events (AEs) were nausea (31.3%) and diarrhea (25.0%). The most common grade 3/4 treatment-related AE was increased alanine aminotransferase (12.5%). PK results were consistent with solid tumors, confirming a relatively short steady-state half-life (mean 4.61 h). Among 12 evaluable patients, one complete response and two partial responses were achieved in patients with and without PI3K/mTOR pathway alterations. In a patient with mantle cell lymphoma achieving PR, SAR245409 was associated with significant inhibition of PI3K/mTOR and extracellular signal-related kinase (ERK) pathways. Preliminary efficacy warrants further evaluation of SAR245409 in lymphoma.

Ovarian cancer

Epithelial ovarian cancer is the commonest cause of gynaecological cancer-associated death. The disease typically presents in postmenopausal women, with a few months of abdominal pain and distension. Most women have advanced disease (International Federation of Gynecology and Obstetrics [FIGO] stage III), for which the standard of care remains surgery and platinum-based cytotoxic chemotherapy. Although this treatment can be curative for most patients with early stage disease, most women with advanced disease will develop many episodes of recurrent disease with progressively shorter disease-free intervals. These episodes culminate in chemoresistance and ultimately bowel obstruction, the most frequent cause of death. For women whose disease continues to respond to platinum-based drugs, the disease can often be controlled for 5 years or more. Targeted treatments such as antiangiogenic drugs or poly (ADP-ribose) polymerase inhibitors offer potential for improved survival. The efficacy of screening, designed to detect the disease at an earlier and curable stage remains unproven, with key results expected in 2015.

Targeting PI3 kinase in cancer

The PI3K/Akt/mTOR pathway is the most frequently known activated aberrant pathway in human cancers. Pathologic activation can occur at multiple levels along the signaling pathway by a variety of mechanisms, including point mutations, amplifications, and inactivation of tumor suppressor genes. This pathway is also a known resistance pathway, as it can be activated by both receptor tyrosine kinases and other oncogenes. mTOR inhibitors were the first targeted molecules in this pathway, and have already been FDA-approved in multiple indications. Because of the broad potential applications of inhibiting this pathway upstream of mTOR, multiple compounds targeting PI3K are in development. In this review, we discuss the clinical development of these inhibitors, including dual PI3K/mTOR inhibitors, pan-PI3K inhibitors, and isoform-selective PI3K inhibitors. Common adverse events, including rash, nausea, vomiting, diarrhea, and hyperglycemia, have created a narrow therapeutic window for all classes of PI3K inhibitors. Furthermore, single agent clinical activity has also been limited, with the exception of isoform-selective inhibitors, particularly the PI3Kδ and PI3Kγ inhibitors in hematologic malignancies. The future role of inhibitors of the PI3K/Akt/mTOR pathway in the clinical practice of oncology likely depends on the development of patient selection strategies and the results of combination trials that are currently ongoing.