Antitumor efficacy of PKI-587, a highly potent dual PI3K/mTOR kinase inhibitor

Targeting PI3K family with small-molecule inhibitors in cancer therapy: current clinical status and future directions

The Phosphatidylinositol-3-kinase (PI3K) family is well-known to comprise three classes of intracellular enzymes. Class I PI3Ks primarily function in signaling by responding to cell surface receptor stimulation, while class II and III are more involved in membrane transport. Under normal physiological conditions, the PI3K signaling network orchestrates cell growth, division, migration and survival. Aberrant activation of the PI3K signaling pathway disrupts cellular activity and metabolism, often marking the onset of cancer. Currently, the Food and Drug Administration (FDA) has approved the clinical use of five class I PI3K inhibitors. These small-molecule inhibitors, which exhibit varying selectivity for different class I PI3K family members, are primarily used in the treatment of breast cancer and hematologic malignancies. Therefore, the development of novel class I PI3K inhibitors has been a prominent research focus in the field of oncology, aiming to enhance potential therapeutic selectivity and effectiveness. In this review, we summarize the specific structures of PI3Ks and their functional roles in cancer progression. Additionally, we critically evaluate small molecule inhibitors that target class I PI3K, with a particular focus on their clinical applications in cancer treatment. Moreover, we aim to analyze therapeutic approaches for different types of cancers marked by aberrant PI3K activation and to identify potential molecular targets amenable to intervention with small-molecule inhibitors. Ultimately, we propose future directions for the development of therapeutic strategies that optimize cancer treatment outcomes by modulating the PI3K family.

Assessments of prostate cancer cell functions highlight differences between a pan-PI3K/mTOR inhibitor, gedatolisib, and single-node inhibitors of the PI3K/AKT/mTOR pathway

Metastatic castration-resistant prostate cancer (mCRPC) is characterized by loss of androgen receptor (AR) sensitivity and oncogenic activation of the PI3K/AKT/mTOR (PAM) pathway. Loss of the PI3K regulator PTEN is frequent during prostate cancer (PC) initiation, progression, and therapeutic resistance. Co-targeting the PAM/AR pathways is a promising mCRPC treatment strategy but is hampered by reciprocal negative feedback inhibition or feedback relief. Most PAM inhibitors selectively spare (or weakly inhibit) one or more key nodes of the PAM pathway, potentiating drug resistance depending on the PAM pathway mutation status of patients. We posited that gedatolisib, a uniformly potent inhibitor of all class I PI3K isoforms, as well as mTORC1 and mTORC2, would be more effective than inhibitors targeting single PAM pathway nodes in PC cells. Using a combination of functional and metabolic assays, we evaluated a panel of PC cell lines with different PTEN/PIK3CA status for their sensitivity to multi-node PAM inhibitors (PI3K/mTOR: gedatolisib, samotolisib) and single-node PAM inhibitors (PI3Kα: alpelisib; AKT: capivasertib; mTOR: everolimus). Gedatolisib induced anti-proliferative and cytotoxic effects with greater potency and efficacy relative to the other PAM inhibitors, independent of PTEN/PIK3CA status. The superior effects of gedatolisib were likely associated with more effective inhibition of critical PAM-controlled cell functions, including cell cycle, survival, protein synthesis, oxygen consumption rate, and glycolysis. Our results indicate that potent and simultaneous blockade of all class I PI3K isoforms, mTORC1, and mTORC2 could circumvent PTEN-dependent resistance. Gedatolisib, as a single agent and in combination with other therapies, reported promising preliminary efficacy and safety in various solid tumor types. Gedatolisib is currently being evaluated in a Phase 1/2 clinical trial in combination with darolutamide in patients with mCRPC previously treated with an AR inhibitor, and in a Phase 3 clinical trial in combination with palbociclib and fulvestrant in patients with HR+/HER2- advanced breast cancer.

Method development and validation for the estimation of gedatolisib in mouse plasma by tandem mass spectrometry and its application to pharmacokinetics studies

A simple and a sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for the quantification of gedatolisib in mouse plasma. The extraction technique involved a simple precipitation method to extract gedatolisib and idelalisib (internal standard) from mouse plasma. A clean chromatographic separation of gedatolisib and the internal standard was achieved on an Atlantis dC18 column using an isocratic mobile phase (10 mm ammonium formate and acetonitrile; 30:70% v/v, both supplemented with 0.1% formic acid) delivered at a flow rate of 0.7 ml/min. The total run time was 2.0 min, and gedatolisib and idelalisib were eluted at 0.80 and 0.95 min, respectively. Gedatolisib was monitored at m/z 616.40 → 488.20 and idelalisib at 416.05 → 176.10. All the required parameters for the method validation were performed as per US Food and Drug Administration guidelines, and the results were within the acceptance criteria. The method was accurate and proved to be precise at a linearity range of 1.33-2667 ng/ml. The accuracy for gedatolisib in mouse plasma was in the ranges 0.99-1.06% (intra-day) and 0.96-1.04% (inter-day). Gedatolisib appeared to be stable in a series of stability conditions. Gedatolisib showed a good intravenous profile when administered through a solution formulation.

Gedatolisib shows superior potency and efficacy versus single-node PI3K/AKT/mTOR inhibitors in breast cancer models

The PI3K, AKT, and mTOR (PAM) pathway is frequently dysregulated in breast cancer (BC) to accommodate high catabolic and anabolic activities driving tumor growth. Current therapeutic options for patients with hormone receptor (HR) + / HER2- advanced BC (ABC) include PAM inhibitors that selectively inhibit only one PAM pathway node, which can lead to drug resistance as cells rapidly adapt to maintain viability. We hypothesized that gedatolisib, which potently inhibits all Class I PI3K isoforms, as well as mTORC1 and mTORC2, may be more effective in BC cells than single-node PAM inhibitors by limiting adaptive resistances. By using multiple functional assays, a panel of BC cell lines was evaluated for their sensitivity to four different PAM inhibitors: gedatolisib (pan-PI3K/mTOR inhibitor), alpelisib (PI3Kα inhibitor), capivasertib (AKT inhibitor), and everolimus (mTORC1 inhibitor). Gedatolisib exhibited more potent and efficacious anti-proliferative and cytotoxic effects regardless of the PAM pathway mutational status of the cell lines compared to the single-node PAM inhibitors. The higher efficacy of gedatolisib was confirmed in three-dimensional culture and in BC PDX models. Mechanistically, gedatolisib decreased cell survival, DNA replication, cell migration and invasion, protein synthesis, glucose consumption, lactate production, and oxygen consumption more effectively than the other PAM inhibitors tested. These results indicate that inhibition of multiple PAM pathway nodes by a pan-PI3K/mTOR inhibitor like gedatolisib may be more effective at inducing anti-tumor activity than single-node PAM inhibitors. A global Phase 3 study is currently evaluating gedatolisib plus fulvestrant with and without palbociclib in patients with HR+/HER2- ABC.

Gedatolisib in combination with palbociclib and endocrine therapy in women with hormone receptor-positive, HER2-negative advanced breast cancer: results from the dose expansion groups of an open-label, phase 1b study

BACKGROUND

The PI3K-mTOR pathway is frequently dysregulated in breast cancer. Combining an inhibitor targeting all class I PI3K isoforms and mTOR complex 1 (mTORC1)-mTOR complex 2 (mTORC2) with endocrine therapy and a CDK4/6 inhibitor might provide more effective tumour control than standard-of-care therapy. To evaluate this hypothesis, gedatolisib, a pan-PI3K-mTOR inhibitor, was assessed in a phase 1b trial combined with palbociclib and endocrine therapy in patients with hormone receptor-positive, HER2-negative, advanced breast cancer. Results from the dose expansion portion of this trial are reported herein.

METHODS

This multicentre, open-label, phase 1b study recruited female patients aged at least 18 years from 17 sites across the USA with hormone-receptor-positive, HER2-negative, advanced breast cancer and an Eastern Cooperative Oncology Group performance status of 0-1. Four patient groups were studied in the dose expansion portion of the study: treatment-naive in the advanced setting (first line; group A), progression on 1-2 lines of endocrine therapy but CDK4/6 inhibitor-naive (group B); and one or more previous lines (second-line and higher) of therapy, including a CDK4/6 inhibitor (groups C and D). Gedatolisib 180 mg was administered intravenously weekly in 28-day treatment cycles for groups A-C, and on days 1, 8, and 15 for group D. Letrozole (group A), fulvestrant (groups B-D), and palbociclib (all groups) were administered at standard doses and schedules. The primary endpoint was investigator-assessed objective response rate per RECIST version 1.1 in the evaluable analysis set. This trial is completed and registered with ClinicalTrials.gov, NCT02684032.

FINDINGS

Between Dec 19, 2017, and June 19, 2019, 103 female participants were enrolled in the dose expansion groups A (n=31), B (n=13), C (n=32), and D (n=27). Median follow-up was 16·6 months (IQR 5·7-48·4) for group A, 11·0 months (7·6-16·9) for group B, 3·6 months (1·8-7·5) for group C, and 9·4 months (5·3-16·7) for group D for the primary endpoint. Gedatolisib, palbociclib, and endocrine therapy induced an objective response in 23 (85·2%; 90% CI 69·2-94·8) of 27 evaluable first-line participants (group A). In the second-line and higher setting, an objective response was observed in eight (61·5%; 90% CI 35·5-83·4) of 13 evaluable group B participants, seven (25·0%; 12·4-41·9) of 28 evaluable group C participants, and 15 (55·6%; 38·2-72·0) of 27 evaluable group D participants; this included participants with both wild-type and mutated PIK3CA tumours. The most common grade 3-4 treatment-related adverse events were neutropenia (65 [63%] of 103), stomatitis (28 [27%]), and rash (21 [20%]). Grade 3-4 hyperglycaemia was reported in six (6%) participants. 23 (22%) of 103 participants had a treatment-related serious adverse event, and there were no treatment-related deaths. Nine (9%) participants discontinued treatment because of a treatment-emergent adverse event.

INTERPRETATION

Gedatolisib plus palbociclib and endocrine therapy showed a promising objective response rate compared with the published results for standard-of-care therapies and had an acceptable safety profile.

FUNDING

Pfizer and Celcuity.

Targeting autophagy drug discovery: Targets, indications and development trends

Autophagy plays a vital role in sustaining cellular homeostasis and its alterations have been implicated in the etiology of many diseases. Drugs development targeting autophagy began decades ago and hundreds of agents were developed, some of which are licensed for the clinical usage. However, no existing intervention specifically aimed at modulating autophagy is available. The obstacles that prevent drug developments come from the complexity of the actual impact of autophagy regulators in disease scenarios. With the development and application of new technologies, several promising categories of compounds for autophagy-based therapy have emerged in recent years. In this paper, the autophagy-targeted drugs based on their targets at various hierarchical sites of the autophagic signaling network, e.g., the upstream and downstream of the autophagosome and the autophagic components with enzyme activities are reviewed and analyzed respectively, with special attention paid to those at preclinical or clinical trials. The drugs tailored to specific autophagy alone and combination with drugs/adjuvant therapies widely used in clinical for various diseases treatments are also emphasized. The emerging drug design and development targeting selective autophagy receptors (SARs) and their related proteins, which would be expected to arrest or reverse the progression of disease in various cancers, inflammation, neurodegeneration, and metabolic disorders, are critically reviewed. And the challenges and perspective in clinically developing autophagy-targeted drugs and possible combinations with other medicine are considered in the review.

The search for CDK4/6 inhibitor biomarkers has been hampered by inappropriate proliferation assays

CDK4/6 inhibitors are effective at treating advanced HR+ /HER2- breast cancer, however biomarkers that can predict response are urgently needed. We demonstrate here that previous large-scale screens designed to identify which tumour types or genotypes are most sensitive to CDK4/6 inhibitors have misrepresented the responsive cell lines because of a reliance on metabolic proliferation assays. CDK4/6-inhibited cells arrest in G1 but continue to grow in size, thereby producing more mitochondria. We show that this growth obscures the arrest using ATP-based proliferation assays but not if DNA-based assays are used instead. Furthermore, lymphoma lines, previously identified as the most sensitive, simply appear to respond the best using ATP-based assays because they fail to overgrow during the G1 arrest. Similarly, the CDK4/6 inhibitor abemaciclib appears to inhibit proliferation better than palbociclib because it also restricts cellular overgrowth through off-target effects. DepMap analysis of screening data using reliable assay types, demonstrates that palbociclib-sensitive cell types are also sensitive to Cyclin D1, CDK4 and CDK6 knockout/knockdown, whereas the palbociclib-resistant lines are sensitive to Cyclin E1, CDK2 and SKP2 knockout/knockdown. Potential biomarkers of palbociclib-sensitive cells are increased expression of CCND1 and RB1, and reduced expression of CCNE1 and CDKN2A. Probing DepMap with similar data from metabolic assays fails to reveal these associations. Together, this demonstrates why CDK4/6 inhibitors, and any other anti-cancer drugs that arrest the cell cycle but permit continued cell growth, must now be re-screened against a wide-range of cell types using an appropriate proliferation assay. This would help to better inform clinical trials and to identify much needed biomarkers of response.

PI3K and tankyrase inhibitors as therapeutic targets in colorectal cancer

INTRODUCTION

The pathways like Wingless-related integration (Wnt/β-catenin) and PI3K play an important role in colorectal cancer (CRC) development; however, their roles are distinct in the process of oncogenesis. Despite their differences, these pathways interact through feedback mechanisms and regulate the common effectors both in the upstream and the downstream processes in normal and pathological conditions. Their ability to reciprocally control each other is a primary resistance mechanism for the selective inhibitors in CRC.

AREA COVERED

This review highlights the Wnt/β-catenin and PI3K pathways that are interrelated in CRC, recent advances and some key perspectives in developing inhibitors that could target the tankyrase enzyme and PI3K, apart from a brief description of the potential of dual inhibitors of PI3K and Tankyrases (TNKS).

EXPERT OPINION

Recent research has focused on overcoming the challenges particularly relating to the resistance and efficacy of dual inhibitors targeting PI3K and tankyrase proteins. Despite these challenges, PI3K as well as tankyrases remain promising therapeutic targets for the treatment of solid tumors. The design of potent inhibitors is crucial to effectively block these protein signaling pathways. Moreover, it is essential to explore the potential of dual-target inhibition of other signaling pathways in conjunction with PI3K and tankyrase.

Advancements in dual-target inhibitors of PI3K for tumor therapy: Clinical progress, development strategies, prospects

Phosphoinositide 3-kinases (PI3Ks) modify lipids by the phosphorylation of inositol phospholipids at the 3'-OH position, thereby participating in signal transduction and exerting effects on various physiological processes such as cell growth, metabolism, and organism development. PI3K activation also drives cancer cell growth, survival, and metabolism, with genetic dysregulation of this pathway observed in diverse human cancers. Therefore, this target is considered a promising potential therapeutic target for various types of cancer. Currently, several selective PI3K inhibitors and one dual-target PI3K inhibitor have been approved and launched on the market. However, the majority of these inhibitors have faced revocation or voluntary withdrawal of indications due to concerns regarding their adverse effects. This article provides a comprehensive review of the structure and biological functions, and clinical status of PI3K inhibitors, with a specific emphasis on the development strategies and structure-activity relationships of dual-target PI3K inhibitors. The findings offer valuable insights and future directions for the development of highly promising dual-target drugs targeting PI3K.

Preclinical evaluation of the CDK4/6 inhibitor palbociclib in combination with a PI3K or MEK inhibitor in colorectal cancer

BACKGROUND

Studies have demonstrated the efficacy of Palbociclib (CDK 4/6 inhibitor), Gedatolisib (PI3K/mTOR dual inhibitor) and PD0325901 (MEK1/2 inhibitor) in colorectal cancer (CRC), however single agent therapeutics are often limited by the development of resistance.

METHODS

We compared the anti-proliferative effects of the combination of Gedatolisib and Palbociclib and Gedatolisib and PD0325901 in five CRC cell lines with varying mutational background and tested their combinations on total and phosphoprotein levels of signaling pathway proteins.

RESULTS

The combination of Palbociclib and Gedatolisib was superior to the combination of Palbociclib and PD0325901. The combination of Palbociclib and Gedatolisib had synergistic anti-proliferative effects in all cell lines tested [CI range: 0.11-0.69] and resulted in the suppression of S6rp (S240/244), without AKT reactivation. The combination of Palbociclib and Gedatolisib increased BAX and Bcl-2 levels in PIK3CA mutated cell lines. The combination of Palbociclib and Gedatolisib caused MAPK/ERK reactivation, as seen by an increase in expression of total EGFR, regardless of the mutational status of the cells.

CONCLUSION

This study shows that the combination of Palbociclib and Gedatolisib has synergistic anti-proliferative effects in both wild-type and mutated CRC cell lines. Separately, the phosphorylation of S6rp may be a promising biomarker of responsiveness to this combination.

Discovery of novel potent PI3K/mTOR dual-target inhibitors based on scaffold hopping: Design, synthesis, and antiproliferative activity

The PI3K/AKT/mTOR pathway is one of the most common dysregulated signaling cascade responses in human cancers, playing a crucial role in cell proliferation and angiogenesis. Therefore, the development of anticancer drugs targeting the PI3K and mTOR pathways has become a research hotspot in cancer treatment. In this study, the PI3K selective inhibitor GDC-0941 was selected as a lead compound, and 28 thiophenyl-triazine derivatives with aromatic urea structures were synthesized based on scaffold hopping, serving as a novel class of PI3K/mTOR dual inhibitors. The most promising compound Y-2 was obtained through antiproliferative activity evaluation, kinase inhibition, and toxicity assays. The results showed that Y-2 demonstrated potential inhibitory effects on both PI3K kinase and mTOR kinase, with IC50 values of 171.4 and 10.2 nM, respectively. The inhibitory effect of Y-2 on mTOR kinase was 52 times greater than that of the positive drug GDC-0941. Subsequently, the antitumor activity of Y-2 was verified through pharmacological experiments such as AO staining, cell apoptosis, scratch assays, and cell colony formation. The antitumor mechanism of Y-2 was further investigated through JC-1 experiments, real-time quantitative PCR, and Western blot analysis. Based on the above experiments, Y-2 can be identified as a potent PI3K/mTOR dual inhibitor for cancer treatment.

Oncogenic signals prime cancer cells for toxic cell overgrowth during a G1 cell cycle arrest

CDK4/6 inhibitors are remarkable anti-cancer drugs that can arrest tumor cells in G1 and induce their senescence while causing only relatively mild toxicities in healthy tissues. How they achieve this mechanistically is unclear. We show here that tumor cells are specifically vulnerable to CDK4/6 inhibition because during the G1 arrest, oncogenic signals drive toxic cell overgrowth. This overgrowth causes permanent cell cycle withdrawal by either preventing progression from G1 or inducing genotoxic damage during the subsequent S-phase and mitosis. Inhibiting or reverting oncogenic signals that converge onto mTOR can rescue this excessive growth, DNA damage, and cell cycle exit in cancer cells. Conversely, inducing oncogenic signals in non-transformed cells can drive these toxic phenotypes and sensitize the cells to CDK4/6 inhibition. Together, this demonstrates that cell cycle arrest and oncogenic cell growth is a synthetic lethal combination that is exploited by CDK4/6 inhibitors to induce tumor-specific toxicity.

Unveiling Novel Avenues in mTOR-Targeted Therapeutics: Advancements in Glioblastoma Treatment

The mTOR signaling pathway plays a pivotal and intricate role in the pathogenesis of glioblastoma, driving tumorigenesis and proliferation. Mutations or deletions in the PTEN gene constitutively activate the mTOR pathway by expressing growth factors EGF and PDGF, which activate their respective receptor pathways (e.g., EGFR and PDGFR). The convergence of signaling pathways, such as the PI3K-AKT pathway, intensifies the effect of mTOR activity. The inhibition of mTOR has the potential to disrupt diverse oncogenic processes and improve patient outcomes. However, the complexity of the mTOR signaling, off-target effects, cytotoxicity, suboptimal pharmacokinetics, and drug resistance of the mTOR inhibitors pose ongoing challenges in effectively targeting glioblastoma. Identifying innovative treatment strategies to address these challenges is vital for advancing the field of glioblastoma therapeutics. This review discusses the potential targets of mTOR signaling and the strategies of target-specific mTOR inhibitor development, optimized drug delivery system, and the implementation of personalized treatment approaches to mitigate the complications of mTOR inhibitors. The exploration of precise mTOR-targeted therapies ultimately offers elevated therapeutic outcomes and the development of more effective strategies to combat the deadliest form of adult brain cancer and transform the landscape of glioblastoma therapy.

Multifaceted role of mTOR (mammalian target of rapamycin) signaling pathway in human health and disease

The mammalian target of rapamycin (mTOR) is a protein kinase that controls cellular metabolism, catabolism, immune responses, autophagy, survival, proliferation, and migration, to maintain cellular homeostasis. The mTOR signaling cascade consists of two distinct multi-subunit complexes named mTOR complex 1/2 (mTORC1/2). mTOR catalyzes the phosphorylation of several critical proteins like AKT, protein kinase C, insulin growth factor receptor (IGF-1R), 4E binding protein 1 (4E-BP1), ribosomal protein S6 kinase (S6K), transcription factor EB (TFEB), sterol-responsive element-binding proteins (SREBPs), Lipin-1, and Unc-51-like autophagy-activating kinases. mTOR signaling plays a central role in regulating translation, lipid synthesis, nucleotide synthesis, biogenesis of lysosomes, nutrient sensing, and growth factor signaling. The emerging pieces of evidence have revealed that the constitutive activation of the mTOR pathway due to mutations/amplification/deletion in either mTOR and its complexes (mTORC1 and mTORC2) or upstream targets is responsible for aging, neurological diseases, and human malignancies. Here, we provide the detailed structure of mTOR, its complexes, and the comprehensive role of upstream regulators, as well as downstream effectors of mTOR signaling cascades in the metabolism, biogenesis of biomolecules, immune responses, and autophagy. Additionally, we summarize the potential of long noncoding RNAs (lncRNAs) as an important modulator of mTOR signaling. Importantly, we have highlighted the potential of mTOR signaling in aging, neurological disorders, human cancers, cancer stem cells, and drug resistance. Here, we discuss the developments for the therapeutic targeting of mTOR signaling with improved anticancer efficacy for the benefit of cancer patients in clinics.

The regulation of PTEN: Novel insights into functions as cancer biomarkers and therapeutic targets

This review summarizes the implications of the primary tumor suppressor protein phosphatase and tensin homolog (PTEN) in aggressive cancer development. PTEN interacts with other cellular proteins or factors suggesting the existence of an intricate molecular network that regulates their oncogenic function. Accumulating evidence has shown that PTEN exists and plays a role in the cytoplasmic organelles and in the nucleus. PTEN blocks phosphoinositide 3-kinases (PI3K)-protein kinase B-mammalian target of rapamycin signaling pathway by dephosphorylating phosphatidylinositol (PI)-3,4,5-triphosphate to PI-4,5-bisphosphate thus counteracting PI3K function. Studies have shown that PTEN expression is tightly regulated at transcriptional, posttranscriptional, and posttranslational levels (including protein-protein interactions and posttranslational modifications). Despite recent advances in PTEN research, the regulation and function of the PTEN gene remain largely unknown. How mutation or loss of specific exons in the PTEN gene occurs and involves in cancer development is not clear. This review illustrates the regulatory mechanisms of PTEN expression and discusses how PTEN participates in tumor development and/or suppression. Future prospects for the clinical applications are also highlighted.

Design, Synthesis and Phenotypic Profiling of Simplified Gedatolisib Analogues

Targeted antitumour therapy has revolutionized the treatment of several types of tumours. Among the validated targets, phosphatidylinositol-3 kinase (PI3K) deserves to be highlighted. Several PI3K inhibitors have been developed for the treatment of cancer, including gedatolisib (4). This inhibitor was elected as a prototype and molecular modifications were planned to design a new series of simplified gedatolisib analogues (5a-f). The analogues were synthesised, and the comparative cytotoxic activity profile was studied in phenotypic models employing solid and nonadherent tumour cell lines. Compound 5f (LASSBio-2252) stood out as the most promising of the series, showing good aqueous solubility (42.38 μM (pH = 7.4); 39.33 μM (pH = 5.8)), good partition coefficient (cLogP = 2.96), cytotoxic activity on human leukemia cell lines (CCRF-CEM, K562 and MOLT-4) and an excellent metabolic stability profile in rat liver microsomes (t1/2 = 462 min; Clapp = 0.058 mL/min/g). The ability of 5f to exert its cytotoxic effect through modulation of the PI3K pathway was demonstrated by flow cytometry analysis in a comparative manner to gedatolisib.

Recent advances in PI3K/PKB/mTOR inhibitors as new anticancer agents

The biochemical role of the PI3K/PKB/mTOR signalling pathway in cell-cycle regulation is now well known. During the onset and development of different forms of cancer it becomes overactive reducing apoptosis and allowing cell proliferation. Therefore, this pathway has become an important target for the treatment of various forms of malignant tumors, including breast cancer and follicular lymphoma. Recently, several more or less selective inhibitors targeting these proteins have been identified. In general, drugs that act on multiple targets within the entire pathway are more efficient than single targeting inhibitors. Multiple inhibitors exhibit high potency and limited drug resistance, resulting in promising anticancer agents. In this context, the present survey focuses on small molecule drugs capable of modulating the PI3K/PKB/mTOR signalling pathway, thus representing drugs or drug candidates to be used in the pharmacological treatment of different forms of cancer.

Design, synthesis and pharmacological evaluation of 2-arylurea-1,3,5-triazine derivative (XIN-9): A novel potent dual PI3K/mTOR inhibitor for cancer therapy

Blocking the PI3K/AKT/mTOR pathway has been widely recognized as an attractive cancer therapeutic strategy because of its crucial role in cell growth and survival. In this study, a novel series of 2-arylurea-1,3,5-triazine derivatives had been synthesized and evaluated as highly potent PI3K and mTOR inhibitors. The new compounds exhibited cytotoxic activities against MCF-7, Hela and A549 cancer cell lines (IC₅₀ = 0.03-36.54 μM). The most promising compound XIN-9 exhibited potent inhibition against PI3K and mTOR kinase (IC₅₀ = 23.8 and 10.9 nM). Mechanistic study using real-time PCR revealed the ability of XIN-9 to inhibit PI3K and mTOR. In addition, compound XIN-9 arrested the cell cycle of MCF-7 cells at the G0/G1 phase. XIN-9 also caused a significant dose-dependent increase of early and late apoptotic events. Molecular docking analysis revealed a high binding affinity for XIN-9 toward PI3K and mTOR. Following in vitro studies, XIN-9 was further evaluated in MCF-7 xenograft models to show significant in vivo anticancer efficacies with tumor growth inhibitions of 41.67% (po, 75 mg/kg). Overall, this work indicated that compound XIN-9 represents a potential anticancer targeting PI3K/AKT/mTOR pathway.

XS-2, a novel potent dual PI3K/mTOR inhibitor, exhibits high in vitro and in vivo anti-breast cancer activity and low toxicity with the potential to inhibit the invasion and migration of triple-negative breast cancer

Breast cancer has become the most commonly diagnosed cancer, surpassing lung cancer, with 2.26 million new breast cancers worldwide in 2020. Hence, there is an urgent need to develop effective molecularly targeted therapeutic drugs to treat breast cancer. In this paper, we designed, synthesized and screened a novel thiophene-triazine derivative, XS-2, as a potent dual PI3K/mTOR inhibitor for the treatment of breast cancer. Also, XS-2 was found to be potentially effective against triple-negative breast cancer (TNBC) in vitro during the investigation. We evaluated the in vitro inhibitory effect of XS-2 on 10 cancer cell lines by MTT and 6 kinases to investigated its in vivo antitumor activity in MCF-7 xenograft tumor-bearing BALB/c nude mice. In addition, the in vitro/in vivo toxicity to mice was also assessed by hemolytic toxicity, H&E staining and blood biochemical analysis. In order to investigate the antitumor mechanism of XS-2, a series of experiments were carried out in vitro/in vivo animal model and molecular biological levels such as the cell cycle and the apoptosis assay, real-time PCR, western blot, docking and molecular simulations analysis, etc. What's more, wound healing assay, Transwell and Western Blot were applied to explore the ability of XS-2 to inhibit the cell invasion and migration. The results showed that XS-2 exhibited strong antitumor activity both in vitro and in vivo. The inhibitory activities of XS-2 on ten cancer cell lines were ranging from 1.07 ± 0.11 to 0.002 ± 0.001 μM, which were 1565 times better than that of the lead compound GDC-0941, inhibitory activities against PI3Kα and mTOR kinases were 291.0 and 60.8 nM, respectively. Notably, XS-2 not only showed significant in vivo antitumor activity and low toxicity, with the tumor inhibition rate of 57.0 %, but also exhibited strong inhibitory in the expression of related proteins of PI3K pathway in tumor tissues. In addition, XS-2 significantly inhibited breast cancer MCF-7 and MDA-MB-231 cells in a concentration- and time-dependent manner, and inhibited the migration and invasion ability of MDA-MB-231 and MCF-7 cells. More than that, XS-2 could inhibit the increase of the expression levels of N-cadherin and vimentin upregulated by EGF and reversed the E-cadherin expression down regulated by EGF, resulting in inhibiting EMT in MCF-7 and MDA-MB-231 cells. The results showed that XS-2 was expected to be successfully developed as a high-efficiency and low-toxicity breast cancer therapeutic drug with the potential to inhibit the invasion and migration of TNBC. This provides a new research idea for the treatment of TNBC, which is of great significance.

Antitumor activity of the dual PI3K/mTOR inhibitor gedatolisib and the involvement of ABCB1 in gedatolisib resistance in canine tumor cells

The phosphatidylinositol 3-kinase/mammalian target of rapamycin (PI3K/mTOR) signaling pathway is a therapeutic target for various types of human tumors, and dual PI3K/mTOR inhibitors demonstrate antitumor activities in both preclinical and clinical studies. However, resistance mechanisms limit their abilities. As the molecular mechanisms involved in the cellular resistance are not clear in any canine tumors, an understanding of resistance mechanisms would support the potential use of dual PI3K/mTOR inhibitors in canine tumors. The antitumor activity of gedatolisib on cell viability, protein phosphorylation, and cell cycle distribution was assessed using 12 canine tumor cell lines from 6 types of tumors. In addition, the molecular determinants involved in the cellular sensitivity to gedatolisib were explored by investigating the involvement of serum-and-glucocorticoid-induced kinase 1 (SGK1), PIK3CA, and ATP-binding cassette, subfamily B, member 1 (ABCB1). The results demonstrated that gedatolisib decreased cell viability in all cell lines, with IC₅₀ values <1 µM in 10 of the 12 lines. Gedatolisib inhibited Akt and mTOR complex 1 substrate phosphorylation and induced G₀/G₁ cell cycle arrest. However, certain cell lines with higher IC₅₀ values were more resistant to these effects. These cell lines exhibited higher ABCB1 activity and the ABCB1 inhibitor cyclosporin A enhanced the decrease of cell viability caused by gedatolisib. SGK1 overexpression did not confer resistance to gedatolisib. The mutations of E545K and H1047R in PIK3CA were not observed. The present results indicated that gedatolisib decreased cell viability in canine tumor cell lines and ABCB1 played an important role in gedatolisib resistance, supporting the potential use of gedatolisib for canine tumors.

Emerging Biomarkers and Targeted Therapies in Feline Mammary Carcinoma

Feline mammary carcinoma (FMC) is a common aggressive malignancy with a low survival rate that lacks viable therapeutic options beyond mastectomy. Recently, increasing efforts have been made to understand the molecular mechanisms underlying FMC development, using the knowledge gained from studies on human breast cancer to discover new diagnostic and prognostic biomarkers, thus reinforcing the utility of the cat as a cancer model. In this article, we review the current knowledge on FMC pathogenesis, biomarkers, and prognosis factors and offer new insights into novel therapeutic options for HER2-positive and triple-negative FMC subtypes.

Targeting Different Pathways Using Novel Combination Therapy in Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer accounting for 15-20% of cases and is defined by the lack of hormonal receptors viz., estrogen receptor (ER), progesterone receptor (PR) and expression of human epidermal growth receptor 2 (HER2). Treatment of TNBC is more challenging than other subtypes of breast cancer due to the lack of markers for the molecularly targeted therapies (ER, PR, and HER-2/ Neu), the conventional chemotherapeutic agents are still the mainstay of the therapeutic protocols of its patients. Despite, TNBC being more chemo-responsive than other subtypes, unfortunately, the initial good response to the chemotherapy eventually turns into a refractory drug-resistance. Using a monotherapy for the treatment of cancer, especially high-grade tumors like TNBC, is mostly worthless due to the inherent genetic instability of tumor cells to develop intrinsic and acquired resistance. Thus, a cocktail of two or more drugs with different mechanisms of action is more effective and could successfully control the disease. Furthermore, combination therapy reveals more, or at least the same, effectiveness with lower doses of every single agent and decreases the likelihood of chemoresistance. Herein, we shed light on the novel combinatorial approaches targeting PARP, EGFR, PI3K pathway, AR, and wnt signaling, HDAC, MEK pathway for efficient treatment of high-grade tumors like TNBC and decreasing the onset of resistance.

Phase I Dose-Escalation Study of the Dual PI3K-mTORC1/2 Inhibitor Gedatolisib in Combination with Paclitaxel and Carboplatin in Patients with Advanced Solid Tumors

PURPOSE

This phase I study evaluated safety, tolerability, pharmacokinetics, and preliminary activity of the PI3K/mTORC1/2 dual inhibitor gedatolisib combined with carboplatin and paclitaxel.

PATIENTS AND METHODS

Patients with advanced solid tumors treated with ≤ 2 prior chemotherapies received intravenous gedatolisib on days 1, 8, 15, and 22 (95, 110, or 130 mg according to dose level); carboplatin (AUC5) on day 8 (day 1 following protocol amendment); and paclitaxel at 80 mg/m² on days 8, 15, and 22 (1, 8, and 15 after amendment), every 28 days. Patients without progressive disease after cycle 6 received maintenance gedatolisib until progression.

RESULTS

Seventeen patients were enrolled [11 ovarian (10 clear cell ovarian cancer, CCOC), 4 endometrial, 2 lung cancers]. Median number of prior chemotherapies was 1 (range, 0-2). Median number of administered cycles was 6 (range, 2-16). Dose-limiting toxicities occurred in 4 patients: 2 (cycle 2 delay due to G2-G3 neutropenia) at 110 mg leading to a change in the treatment schedule, 2 at 130 mg (G2 mucositis causing failure to deliver ≥ 75% of gedatolisib at cycle 1). The recommended phase II dose is gedatolisib 110 mg on days 1, 8, 15, and 22 with carboplatin AUC5 on day 1 and paclitaxel 80 mg/m² on days 1, 8, and 15. The most frequent ≥G3 treatment-related adverse events were neutropenia (35%), anemia (18%), and mucositis (12%). The overall response rate was 65% (80% in CCOC). Pharmacokinetic parameters of gedatolisib were consistent with single-agent results.

CONCLUSIONS

Gedatolisib combined with carboplatin and paclitaxel is tolerable, and preliminary efficacy was observed especially in CCOC.

Targeting autophagy in disease: established and new strategies

Macroautophagy/autophagy is an evolutionarily conserved pathway responsible for clearing cytosolic aggregated proteins, damaged organelles or invading microorganisms. Dysfunctional autophagy leads to pathological accumulation of the cargo, which has been linked to a range of human diseases, including neurodegenerative diseases, infectious and autoimmune diseases and various forms of cancer. Cumulative work in animal models, application of genetic tools and pharmacologically active compounds, has suggested the potential therapeutic value of autophagy modulation in disease, as diverse as Huntington, Salmonella infection, or pancreatic cancer. Autophagy activation versus inhibition strategies are being explored, while the role of autophagy in pathophysiology is being studied in parallel. However, the progress of preclinical and clinical development of autophagy modulators has been greatly hampered by the paucity of selective pharmacological agents and biomarkers to dissect their precise impact on various forms of autophagy and cellular responses. Here, we summarize established and new strategies in autophagy-related drug discovery and indicate a path toward establishing a more efficient discovery of autophagy-selective pharmacological agents. With this knowledge at hand, modern concepts for therapeutic exploitation of autophagy might become more plausible.

Abbreviations: ALS: amyotrophic lateral sclerosis; AMPK: AMP-activated protein kinase; ATG: autophagy-related gene; AUTAC: autophagy-targeting chimera; CNS: central nervous system; CQ: chloroquine; GABARAP: gamma-aminobutyric acid type A receptor-associated protein; HCQ: hydroxychloroquine; LYTAC: lysosome targeting chimera; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; NDD: neurodegenerative disease; PDAC: pancreatic ductal adenocarcinoma; PE: phosphatidylethanolamine; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol 3-phosphate; PROTAC: proteolysis-targeting chimera; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2; SQSTM1/p62: sequestosome 1; ULK1: unc-51 like autophagy activating kinase 1.

RASAL2 Confers Collateral MEK/EGFR Dependency in Chemoresistant Triple-Negative Breast Cancer

PURPOSE

While chemotherapy remains the standard treatment for triple-negative breast cancer (TNBC), identifying and managing chemoresistant tumors has proven elusive. We sought to discover hallmarks and therapeutically actionable features of refractory TNBC through molecular analysis of primary chemoresistant TNBC specimens.

EXPERIMENTAL DESIGN

We performed transcriptional profiling of tumors from a phase II clinical trial of platinum chemotherapy for advanced TNBC (TBCRC-009), revealing a gene expression signature that identified de novo chemorefractory tumors. We then employed pharmacogenomic data mining, proteomic and other molecular studies to define the therapeutic vulnerabilities of these tumors.

RESULTS

We reveal the RAS-GTPase-activating protein (RAS-GAP) RASAL2 as an upregulated factor that mediates chemotherapy resistance but also an exquisite collateral sensitivity to combination MAP kinase kinase (MEK1/2) and EGFR inhibitors in TNBC. Mechanistically, RASAL2 GAP activity is required to confer kinase inhibitor sensitivity, as RASAL2-high TNBCs sustain basal RAS activity through suppression of negative feedback regulators SPRY1/2, together with EGFR upregulation. Consequently, RASAL2 expression results in failed feedback compensation upon co-inhibition of MEK1/2 and EGFR that induces synergistic apoptosis in vitro and in vivo. In patients with TNBC, high RASAL2 levels predict clinical chemotherapy response and long-term outcomes, and are associated via direct transcriptional regulation with activated oncogenic Yes-Associated Protein (YAP). Accordingly, chemorefractory patient-derived TNBC models exhibit YAP activation, high RASAL2 expression, and tumor regression in response to MEK/EGFR inhibitor combinations despite well-tolerated intermittent dosing.

CONCLUSIONS

These findings identify RASAL2 as a mediator of TNBC chemoresistance that rewires MAPK feedback and cross-talk to confer profound collateral sensitivity to combination MEK1/2 and EGFR inhibitors.

Next generation proteomics with drug sensitivity screening identifies sub-clones informing therapeutic and drug development strategies for multiple myeloma patients

With the introduction of novel therapeutic agents, survival in Multiple Myeloma (MM) has increased in recent years. However, drug-resistant clones inevitably arise and lead to disease progression and death. The current International Myeloma Working Group response criteria are broad and make it difficult to clearly designate resistant and responsive patients thereby hampering proteo-genomic analysis for informative biomarkers for sensitivity. In this proof-of-concept study we addressed these challenges by combining an ex-vivo drug sensitivity testing platform with state-of-the-art proteomics analysis. 35 CD138-purified MM samples were taken from patients with newly diagnosed or relapsed MM and exposed to therapeutic agents from five therapeutic drug classes including Bortezomib, Quizinostat, Lenalidomide, Navitoclax and PF-04691502. Comparative proteomic analysis using liquid chromatography-mass spectrometry objectively determined the most and least sensitive patient groups. Using this approach several proteins of biological significance were identified in each drug class. In three of the five classes focal adhesion-related proteins predicted low sensitivity, suggesting that targeting this pathway could modulate cell adhesion mediated drug resistance. Using Receiver Operating Characteristic curve analysis, strong predictive power for the specificity and sensitivity of these potential biomarkers was identified. This approach has the potential to yield predictive theranostic protein panels that can inform therapeutic decision making.

The PI3K/mTOR inhibitor Gedatolisib eliminates dormant breast cancer cells in organotypic culture, but fails to prevent metastasis in preclinical settings

Dormant, disseminated tumor cells (DTCs) are thought to be the source of breast cancer metastases several years or even decades after initial treatment. To date, a selective therapy that leads to their elimination has not been discovered. While dormant DTCs resist chemotherapy, evidence suggests that this resistance is driven not by their lack of proliferation, but by their engagement of the surrounding microenvironment, via integrin‐β1‐mediated interactions. Because integrin‐β1‐targeted agents have not been translated readily to the clinic, signaling nodes downstream of integrin‐β1 could serve as attractive therapeutic targets in order to sensitize dormant DTCs to therapy. By probing a number of kinases downstream of integrin‐β1, we determined that PI3K inhibition with either a tool compounds or a compound (PF‐05212384; aka Gedatolisib) in clinical trials robustly sensitizes quiescent breast tumor cells seeded in organotypic bone marrow cultures to chemotherapy. These results motivated the preclinical study of whether Gedatolisib—with or without genotoxic therapy—would reduce DTC burden and prevent metastases. Despite promising results in organotypic culture, Gedatolisib failed to reduce DTC burden or delay, reduce or prevent metastasis in murine models of either triple‐negative or estrogen receptor‐positive breast cancer dissemination and metastasis. This result held true whether analyzing Gedatolisib on its own (vs. vehicle‐treated animals) or in combination with dose‐dense doxorubicin and cyclophosphamide (vs. animals treated only with dose‐dense chemotherapies). These data suggest that PI3K is not the node downstream of integrin‐β1 that confers chemotherapeutic resistance to DTCs. More broadly, they cast doubt on the strategy to target PI3K in order to eliminate DTCs and prevent breast cancer metastasis.

Inhibition of the PI3K/mTOR Pathway in Breast Cancer to Enhance Response to Immune Checkpoint Inhibitors in Breast Cancer

OBJECTIVES

Inhibition of the PI3K/mTOR pathway suppresses breast cancer (BC) growth, enhances anti-tumor immune responses, and works synergistically with immune checkpoint inhibitors (ICI). The objective here was to identify a subclass of PI3K inhibitors that, when combined with paclitaxel, is effective in enhancing response to ICI.

METHODS

C57BL/6 mice were orthotopically implanted with syngeneic luminal/triple-negative-like PyMT cells exhibiting high endogenous PI3K activity. Tumor growth in response to treatment with anti-PD-1 + anti-CTLA-4 (ICI), paclitaxel (PTX), and either the PI3Kα-specific inhibitor alpelisib, the pan-PI3K inhibitor copanlisib, or the broad spectrum PI3K/mTOR inhibitor gedatolisib was evaluated in reference to monotherapy or combinations of these therapies. Effects of these therapeutics on intratumoral immune populations were determined by multicolor FACS.

RESULTS

Treatment with alpelisib + PTX inhibited PyMT tumor growth and increased tumor-infiltrating granulocytes but did not significantly affect the number of tumor-infiltrating CD8+ T cells and did not synergize with ICI. Copanlisib + PTX + ICI significantly inhibited PyMT growth and increased activation of intratumoral CD8+ T cells as compared to ICI alone, yet did not inhibit tumor growth more than ICI alone. In contrast, gedatolisib + ICI resulted in significantly greater inhibition of tumor growth compared to ICI alone and induced durable dendritic-cell, CD8+ T-cell, and NK-cell responses. Adding PTX to this regimen yielded complete regression in 60% of tumors.

CONCLUSION

PI3K/mTOR inhibition plus PTX heightens response to ICI and may provide a viable therapeutic approach for treatment of metastatic BC.

ABCB1 and ABCG2 restricts the efficacy of gedatolisib (PF-05212384), a PI3K inhibitor in colorectal cancer cells

Background

Overexpression of ABC transporters is a big challenge on cancer therapy which will lead cancer cells resistance to a series of anticancer drugs. Gedatolisib is a dual PI3K and mTOR inhibitor which is under clinical evaluation for multiple types of malignancies, including colorectal cancer. The growth inhibitory effects of gedatolisib on colorectal cancer cells have been specifically studied. However, the role of ABC transporters on gedatolisib resistance remained unclear. In present study, we illustrated the role of ABC transporters on gedatolisib resistance in colorectal cancer cells.

Methods

Cell viability investigations of gedatolisib on colorectal cancer cells were determined by MTT assays. The verapamil and Ko143 reversal studies were determined by MTT assays as well. ABCB1 and/or ABCG2 siRNA interference assays were conducted to verify the role of ABCB1- and ABCG2-overexpression on gedatolisib resistance. The accumulation assays of gedatolisib were conducted using tritium-labeled paclitaxel and mitoxantrone. The effects of gedatolisib on ATPase activity of ABCB1 or ABCG2 were conducted using PREDEASY ATPase Kits. The expression level of ABCB1 and ABCG2 after gedatolisib treatment were conducted by Western blotting and immunofluorescence assays. The well-docked position of gedatolisib with crystal structure of ABCB1 and ABCG2 were simulated by Autodock vina software. One-way ANOVA was used for the statistics analysis.

Results

Gedatolisib competitively increased the accumulation of tritium-labeled substrate-drugs in both ABCB1- and ABCG2-overexpression colorectal cancer cells. Moreover, gedatolisib significantly increased the protein expression level of ABCB1 and ABCG2 in colorectal cancer cells. In addition, gedatolisib remarkably simulated the ATPase activity of both ABCB1 and ABCG2, suggesting that gedatolisib is a substrate drug of both ABCB1 and ABCG2 transporters. Furthermore, a gedatolisib-resistance colorectal cancer cell line, SW620/GEDA, was selected by increasingly treatment with gedatolisib to SW620 cells. The SW620/GEDA cell line was proved to resistant to gedatolisib and a series of chemotherapeutic drugs, except cisplatin. The ABCB1 and ABCG2 were observed overexpression in SW620/GEDA cell line.

Conclusions

These findings suggest that overexpression of ABCB1 and ABCG2 may restrict the efficacy of gedatolisib in colorectal cancer cells, while co-administration with ABC transporter inhibitors may improve the potency of gedatolisib.

Biguanide-Based Synthesis of 1,3,5-Triazine Derivatives with Anticancer Activity and 1,3,5-Triazine Incorporated Calcium Citrate Nanoparticles

Twelve derivatives of biguanide-derived 1,3,5-triazines, a promising class of anticancer agent, were synthesised and evaluated for their anticancer activity against two colorectal cancer cell lines-HCT116 and SW620. 2c and 3c which are the derivatives containing o-hydroxyphenyl substituents exhibited the highest activity with IC50 against both cell lines in the range of 20-27 µM, which is comparable to the IC50 of cisplatin reference. Moreover, the potential use of the calcium citrate nanoparticles (CaCit NPs) as a platform for drug delivery system was studied on a selected 1,3,5-triazine derivative 2a. Condition optimisation revealed that the source of citrate ions and reaction time significantly influence the morphology, size and %drug loading of the particles. With the optimised conditions, "CaCit-2a NPs" were successfully synthesised with the size of 148 ± 23 nm and %drug loading of up to 16.3%. Furthermore, it was found that the release of 2a from the synthesised CaCit-2a NPs is pH-responsive, and 2a could be control released under the acidic cancer environment. The knowledge from this study is perceptive for further development of the 1,3,5-triazine-based anticancer drugs and provide the platform for the incorporation of other drugs in the CaCit NPs in the future.

Dacomitinib and gedatolisib in combination with fractionated radiation in head and neck cancer

•

We evaluated radiation with dual EGFR and PI3K targeting in head and neck cancer.

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Dacomitinib, showed an inverse correlation between growth inhibition and EGFR expression.

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Gedatolisib was effective in each cell line. Neither drug caused radiosensitization in vitro.

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Gedatolisib was relatively ineffective in vivo in combination with dacomitinib and/or radiation.

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Dacomitinib was highly effective alone and in combination with radiation and/or gedatolisib.

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Immunoblotting studies in vivo mirrored the effects seen with growth delay.

Background and purpose

There has been little success targeting individual genes in combination with radiation in head and neck cancer. In this study we investigated whether targeting two key pathways simultaneously might be more effective.

Materials and methods

We studied the effect of combining dacomitinib (pan-HER, irreversible inhibitor) and gedatolisib (dual PI3K/MTOR inhibitor) with radiation in well characterized, low passage xenograft models of HNSCC in vitro and in vivo.

Results

Dacomitinib showed differential growth inhibition in vitro that correlated to EGFR expression whilst gedatolisib was effective in both cell lines. Neither agent radiosensitized the cell lines in vitro. In vivo studies demonstrated that dacomitinib was an effective agent alone and in combination with radiation whilst the addition of gedatolisib did not enhance the effect of these two modalities despite inhibiting phosphorylation of key genes in the PI3K/MTOR pathway.

Conclusions

Our results showed that combining two drugs with radiation provided no added benefit compared to the single most active drug. Dacomitinib deserves more investigation as a radiation sensitizing agent in HNSCC.

Targeting PI3K/Akt/mTOR in AML: Rationale and Clinical Evidence

Acute myeloid leukemia (AML) is a highly heterogeneous hematopoietic malignancy characterized by excessive proliferation and accumulation of immature myeloid blasts in the bone marrow. AML has a very poor 5-year survival rate of just 16% in the UK; hence, more efficacious, tolerable, and targeted therapy is required. Persistent leukemia stem cell (LSC) populations underlie patient relapse and development of resistance to therapy. Identification of critical oncogenic signaling pathways in AML LSC may provide new avenues for novel therapeutic strategies. The phosphatidylinositol-3-kinase (PI3K)/Akt and the mammalian target of rapamycin (mTOR) signaling pathway, is often hyperactivated in AML, required to sustain the oncogenic potential of LSCs. Growing evidence suggests that targeting key components of this pathway may represent an effective treatment to kill AML LSCs. Despite this, accruing significant body of scientific knowledge, PI3K/Akt/mTOR inhibitors have not translated into clinical practice. In this article, we review the laboratory-based evidence of the critical role of PI3K/Akt/mTOR pathway in AML, and outcomes from current clinical studies using PI3K/Akt/mTOR inhibitors. Based on these results, we discuss the putative mechanisms of resistance to PI3K/Akt/mTOR inhibition, offering rationale for potential candidate combination therapies incorporating PI3K/Akt/mTOR inhibitors for precision medicine in AML.

Virtual docking screening and QSAR studies to explore AKT and mTOR inhibitors acting on PI3K in cancers

The phosphoinositide 3-kinase (PI3K) pathway is an important regulator of cell proliferation and metabolism. PI3K activation initiates a signal transduction cascade, of which the major effectors are the kinases AKT and mTOR. Aberrant activation of the PI3K/AKT/mTOR pathway is frequently observed in many human malignancies and the combination of compounds simultaneously targeting different related molecules in the PI3K/AKT/mTOR pathway leads to synergistic activity. To explore the competing common ATP inhibitors PI3K/AKT and PI3K/mTOR we developed a model PI3K-SAR 2D which made it possible to predict the bioactivity of inhibitors of AKT and mTOR towards PI3K; the interaction of the best inhibitors was evaluated by docking analysis and compared to that of dactolisib and pictilisib. A PI3K-SAR model with a correlation coefficient (R2) of 0.81706 and an RMSE of 0.16029 was obtained, which was validated and evaluated by a cross-validation method, LOO. The most predicted AKT and mTOR inhibitors present respectively pIC50 activities between 9.26-9.93 and 9.59-9.87. After docking and several comparisons, inhibitors with better predictions showed better affinity and interaction with PI3K compared to pictilisib and dactolisib, so we found that 4 inhibitors of AKT and 14 mTOR inhibitors met the criteria of Lipinski and Veber and could be future drugs.

Triple negative breast cancer: special histological types and emerging therapeutic methods

Triple negative breast cancer (TNBC) is a complex and malignant breast cancer subtype that lacks expression of the estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2), thereby making therapeutic targeting difficult. TNBC is generally considered to have high malignancy and poor prognosis. However, patients diagnosed with certain rare histomorphologic subtypes of TNBC have better prognosis than those diagnosed with typical triple negative breast cancer. In addition, with the discovery and development of novel treatment targets such as the androgen receptor (AR), PI3K/AKT/mTOR and AMPK signaling pathways, as well as emerging immunotherapies, the therapeutic options for TNBC are increasing. In this paper, we review the literature on various histological types of TNBC and focus on newly developed therapeutic strategies that target and potentially affect molecular pathways or emerging oncogenes, thus providing a basis for future tailored therapies focused on the mutational aspects of TNBC.

Mechanistic basis for PI3K inhibitor antitumor activity and adverse reactions in advanced breast cancer

PURPOSE

The phosphatidylinositol 3-kinase (PI3K) pathway is involved in several physiological processes, including glucose metabolism, cell proliferation, and cell growth. Hyperactivation of this signaling pathway has been associated with tumorigenesis and resistance to treatment in various cancer types. Mutations that activate PIK3CA, encoding the PI3K isoform p110α, are common in breast cancer, particularly in the hormone receptor-positive (HR+), human epidermal growth factor receptor-2-negative (HER2-) subtype. A number of PI3K inhibitors have been developed and evaluated for potential clinical use in combinations targeting multiple signaling pathways in cancer. The purpose of this review is to provide an overview of PI3K inhibitor mechanisms of action for antitumor activity and adverse events in advanced breast cancer (ABC).

METHODS

Published results from phase 3 trials evaluating the efficacy and safety of PI3K inhibitors in patients with ABC and relevant literature were reviewed.

RESULTS

Although PI3K inhibitors have been shown to prolong progression-free survival (PFS), the therapeutic index is often unfavorable. Adverse events, such as hyperglycemia, rash, and diarrhea are frequently observed in these patients. In particular, hyperglycemia is intrinsically linked to the inhibition of PI3Kα, a key mediator of insulin signaling. Off-target effects, including mood disorders and liver toxicity, have also been associated with some PI3K inhibitors.

CONCLUSION

Recent clinical trial results show that specifically targeting PI3Kα can improve PFS and clinical benefit. Broad inhibition of class I PI3Ks appears to result in an unfavorable safety profile due to off-target effects, limiting the clinical utility of the early PI3K inhibitors.

6,N 2-Diaryl-1,3,5-triazine-2,4-diamines: synthesis, antiproliferative activity and 3D-QSAR modeling

A library of 126 compounds with a 6,N²-diaryl-1,3,5-triazine-2,4-diamine scaffold was prepared using a one-pot, microwave-assisted method from readily available cyanoguanidine, aromatic aldehydes and arylamines. The three-component condensation of these reagents in the presence of hydrochloric acid was followed by the treatment with a base, which promoted a rearrangement of the dihydrotriazine ring and its dehydrogenative aromatization. The antiproliferative properties of the prepared compounds were evaluated using three breast cancer cell lines. The most promising results were obtained in the growth inhibition of the triple negative MDA-MB231 breast cancer cells. The active compounds were also selective against cancer cells and did not affect growth of the non-cancerous MCF-10A breast cell line. Analyzing the structure–activity relationship within the series, we built a 3D-QSAR model for the further design of more potent anticancer compounds.

New compounds selectively targeting the triple negative MDA-MB231 breast cancer cells were used to build a 3D-QSAR model.

Is There a Role for Dual PI3K/mTOR Inhibitors for Patients Affected with Lymphoma?

The activation of the PI3K/AKT/mTOR pathway is a main driver of cell growth, proliferation, survival, and chemoresistance of cancer cells, and, for this reason, represents an attractive target for developing targeted anti-cancer drugs. There are plenty of preclinical data sustaining the anti-tumor activity of dual PI3K/mTOR inhibitors as single agents and in combination in lymphomas. Clinical responses, including complete remissions (especially in follicular lymphoma patients), are also observed in the very few clinical studies performed in patients that are affected by relapsed/refractory lymphomas or chronic lymphocytic leukemia. In this review, we summarize the literature on dual PI3K/mTOR inhibitors focusing on the lymphoma setting, presenting both the three compounds still in clinical development and those with a clinical program stopped or put on hold.

A Phase I Study of Safety, Pharmacokinetics, and Pharmacodynamics of Concurrent Everolimus and Buparlisib Treatment in Advanced Solid Tumors

PURPOSE

Concurrent inhibition of mTOR and PI3K led to improved efficacy in preclinical models and provided the rationale for this phase I study of everolimus and buparlisib (BKM120) in patients with advanced solid tumor.

PATIENTS AND METHODS

We used the Bayesian Escalation with Overdose Control design to test escalating doses of everolimus (5 or 10 mg) and buparlisib (20, 40, 60, 80, and 100 mg) in eligible patients. Pharmacokinetic assessment was conducted using blood samples collected on cycle 1, days 8 and 15. Pharmacodynamic impact on mTOR/PI3K pathway modulation evaluated in paired skin biopsies collected at baseline and end of cycle 1.

RESULTS

We enrolled 43 patients, median age of 63 (range, 39-78) years; 25 (58.1%) females, 35 (81.4%) Caucasians, and 8 (18.6%) Blacks. The most frequent toxicities were hyperglycemia, diarrhea, nausea, fatigue, and aspartate aminotransferase elevation. Dose-limiting toxicities observed in 7 patients were fatigue (3), hyperglycemia (2), mucositis (1), acute kidney injury (1), and urinary tract infection (1). The recommended phase II dose (RP2D) for the combination was established as everolimus (5 mg) and buparlisib (60 mg). The best response in 27 evaluable patients was progressive disease and stable disease in 3 (11%) and 24 (89%), respectively. The median progression-free survival and overall survival were 2.7 (1.8-4.2) and 9 (6.4-13.2) months. Steady-state pharmacokinetic analysis showed dose-normalized maximum concentrations and AUC values for everolimus and buparlisib in combination to be comparable with single-agent pharmacokinetic.

CONCLUSIONS

The combination of everolimus and buparlisib is safe and well-tolerated at the RP2D of 5 and 60 mg on a continuous daily schedule.

Morpholine as ubiquitous pharmacophore in medicinal chemistry: Deep insight into the structure-activity relationship (SAR)

Morpholine is a versatile moiety, a privileged pharmacophore and an outstanding heterocyclic motif with wide ranges of pharmacological activities due to different mechanisms of action. The ability of morpholine to enhance the potency of the molecule through molecular interactions with the target protein (kinases) or to modulate the pharmacokinetic properties propelled medicinal chemists and researchers to synthesize morpholine ring by the efficient ways and to incorporate this moiety to develop various lead compounds with diverse therapeutic activities. The present review primarily focused on discussing the most promising synthetic leads containing morpholine ring along with structure-activity relationship (SAR) to reveal the active pharmacophores accountable for anticancer, anti-inflammatory, antiviral, anticonvulsant, antihyperlipidemic, antioxidant, antimicrobial and antileishmanial activity. This review outlines some of the recent effective chemical synthesis for morpholine ring. The review also highlighted the metabolic liability of some clinical drugs containing this nucleus and various researches on modified morpholine to enhance the metabolic stability of drugs as well. Drugs bearing morpholine ring and those under clinical trials are also mentioned with the role of morpholine and their mechanism of action. This review will provide the necessary knowledge base to the medicinal chemists in making strategic structural changes in designing morpholine derivatives.

RAS/RAF/MEK/ERK, PI3K/PTEN/AKT/mTORC1 and TP53 pathways and regulatory miRs as therapeutic targets in hepatocellular carcinoma

Introduction: Hepatocellular carcinoma (HCC) is a significant problem globally because of viral infections and the increasing incidence of obesity and fatty liver disease. However, it is difficult to treat because its inherent genetic heterogeneity results in activation of numerous signaling pathways. Kinases have been targeted for decades with varying results, but the development of therapeutic resistance is a major challenge.Areas covered: The key roles of the RAS/RAF/MEK/ERK, PI3K/PTEN/AKT/mTORC1, TP53 microRNAs (miRs) as therapeutic targets are discussed and we suggests novel approaches for targeting miRs or their downstream targets to combat HCC. We performed literature searches using the Medline Database from 2000 to the present.Expert opinion: The involvement of RAS/RAF/MEK/ERK, PI3K/PTEN/AKT/mTORC and TP53 pathways as drivers of the disease and drug resistance is a challenge. Moreover, miRs regulate the expression of key genes in these pathways. What we and others are proposing is the prospect of targeting miRs and their downstream targets to improve conventional approaches to treat HCC. Combination approaches are often promising because multiple signaling pathways are deregulated due to diverse mutations and events.

Clinical Genomic Sequencing of Pediatric and Adult Osteosarcoma Reveals Distinct Molecular Subsets with Potentially Targetable Alterations

PURPOSE

Although multimodal chemotherapy has improved outcomes for patients with osteosarcoma, the prognosis for patients who present with metastatic and/or recurrent disease remains poor. In this study, we sought to define how often clinical genomic sequencing of osteosarcoma samples could identify potentially actionable alterations.Experimental Design: We analyzed genomic data from 71 osteosarcoma samples from 66 pediatric and adult patients sequenced using MSK-IMPACT, a hybridization capture-based large panel next-generation sequencing assay. Potentially actionable genetic events were categorized according to the OncoKB precision oncology knowledge base, of which levels 1 to 3 were considered clinically actionable.

RESULTS

We found at least one potentially actionable alteration in 14 of 66 patients (21%), including amplification of CDK4 (n = 9, 14%: level 2B) and/or MDM2 (n = 9, 14%: level 3B), and somatic truncating mutations/deletions in BRCA2 (n = 3, 5%: level 2B) and PTCH1 (n = 1, level 3B). In addition, we observed mutually exclusive patterns of alterations suggesting distinct biological subsets defined by gains at 4q12 and 6p12-21. Specifically, potentially targetable gene amplifications at 4q12 involving KIT, KDR, and PDGFRA were identified in 13 of 66 patients (20%), which showed strong PDGFRA expression by IHC. In another largely nonoverlapping subset of 14 patients (24%) with gains at 6p12-21, VEGFA amplification was identified.

CONCLUSIONS

We found potentially clinically actionable alterations in approximately 21% of patients with osteosarcoma. In addition, at least 40% of patients have tumors harboring PDGFRA or VEGFA amplification, representing candidate subsets for clinical evaluation of additional therapeutic options. We propose a new genomically based algorithm for directing patients with osteosarcoma to clinical trial options.

Clinical Genomic Sequencing of Pediatric and Adult Osteosarcoma Reveals Distinct Molecular Subsets with Potentially Targetable Alterations

PURPOSE

Although multimodal chemotherapy has improved outcomes for patients with osteosarcoma, the prognosis for patients who present with metastatic and/or recurrent disease remains poor. In this study, we sought to define how often clinical genomic sequencing of osteosarcoma samples could identify potentially actionable alterations.Experimental Design: We analyzed genomic data from 71 osteosarcoma samples from 66 pediatric and adult patients sequenced using MSK-IMPACT, a hybridization capture-based large panel next-generation sequencing assay. Potentially actionable genetic events were categorized according to the OncoKB precision oncology knowledge base, of which levels 1 to 3 were considered clinically actionable.

RESULTS

We found at least one potentially actionable alteration in 14 of 66 patients (21%), including amplification of CDK4 (n = 9, 14%: level 2B) and/or MDM2 (n = 9, 14%: level 3B), and somatic truncating mutations/deletions in BRCA2 (n = 3, 5%: level 2B) and PTCH1 (n = 1, level 3B). In addition, we observed mutually exclusive patterns of alterations suggesting distinct biological subsets defined by gains at 4q12 and 6p12-21. Specifically, potentially targetable gene amplifications at 4q12 involving KIT, KDR, and PDGFRA were identified in 13 of 66 patients (20%), which showed strong PDGFRA expression by IHC. In another largely nonoverlapping subset of 14 patients (24%) with gains at 6p12-21, VEGFA amplification was identified.

CONCLUSIONS

We found potentially clinically actionable alterations in approximately 21% of patients with osteosarcoma. In addition, at least 40% of patients have tumors harboring PDGFRA or VEGFA amplification, representing candidate subsets for clinical evaluation of additional therapeutic options. We propose a new genomically based algorithm for directing patients with osteosarcoma to clinical trial options.

The next generation of PI3K-Akt-mTOR pathway inhibitors in breast cancer cohorts

The PI3K/Akt/mTOR pathway plays a role in various oncogenic processes in breast cancer and key pathway aberrations have been identified which drive the different molecular subtypes. Early drugs developed targeting this pathway produced some clinical success but were hampered by pharmacokinetics, tolerability and efficacy problems. This created a need for new PI3K pathway-inhibiting drugs, which would produce more robust results allowing incorporation into treatment regimens for breast cancer patients. In this review, the most promising candidates from the new generation of PI3K-pathway inhibitors is explored, presenting evidence from preclinical and early clinical research, as well as ongoing trials utilising these drugs in breast cancer cohorts. The problems hindering the development of drugs targeting the PI3K pathway are examined, which have created problems for their use as monotherapies. PI3K pathway inhibitor combinations therefore remains a dynamic research area, and their role in combination with immunotherapies and epigenetic therapies is also inspected.

A Multi-Arm Phase I Study of the PI3K/mTOR Inhibitors PF-04691502 and Gedatolisib (PF-05212384) plus Irinotecan or the MEK Inhibitor PD-0325901 in Advanced Cancer

Background

This phase I, four-arm, open-label study (NCT01347866) evaluated the PI3K/mTOR inhibitors PF-04691502 (arms A, B) and gedatolisib (PF-05212384; arms C, D) in combination with the MEK inhibitor PD-0325901 (arm A, D) or irinotecan (arm B, C) in patients with advanced solid tumors.

Objectives

Primary endpoint was dose-limiting toxicity with each combination. Secondary endpoints included safety, pharmacokinetics and preliminary antitumor activity.

Patients and Methods

Dose escalation followed a 3 + 3 design in arm C and a zone-based design in arm D.

Results

The PF-04691502 combination arms were closed prematurely due to low tolerability, and the maximum tolerated doses (MTDs) were not determined for either arm. The MTD for the combination of gedatolisib with irinotecan 180 mg/m² was estimated to be 110 mg weekly and for the combination with PD-0325901 was not reached at the highest dose evaluated (gedatolisib 154 mg weekly). Plasma concentrations of gedatolisib were generally similar across dose groups in arm C (with irinotecan) and arm D (with PD-0325901). Frequent dose delays or dose reductions were required for both combinations, potentially preventing sustained therapeutic drug concentrations. Gedatolisib plus irinotecan produced a response rate of ~5% and clinical benefit in 16% of patients with advanced colorectal cancer (progression-free survival, 2.8 months). Preliminary evidence of clinical activity was observed with gedatolisib plus PD-0325901 in patients with ovarian cancer (three partial responses, n = 5) or endometrial cancer (one partial response, n = 1) and KRAS mutations.

Conclusions

Further evaluations of gedatolisib are warranted in patients with advanced solid malignancies.

Electronic supplementary material

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Targeting phosphoinositide 3-kinase (PI3K) in head and neck squamous cell carcinoma (HNSCC)

The landscape of head and neck squamous cell carcinoma (HNSCC) has been changing rapidly due to growing proportion of HPV-related disease and development of new therapeutic agents. At the same time, there has been a constant need for individually tailored treatment based on genetic biomarkers in order to optimize patient survival and alleviate treatment-related toxicities. In this regard, aberrations of PI3K pathway have important clinical implications in the treatment of HNSCC. They frequently constitute ‘gain of function’ mutations which trigger oncogenesis, and PI3K mutations can also lead to emergence of drug resistance after treatment with EGFR inhibitors. In this article, we review PI3K pathway as a target of treatment for HNSCC and summarize PI3K/mTOR inhibitors that are currently under clinical trials. In light of recent advancement of immune checkpoint inhibitors, consideration of PI3K inhibitors as potential immune modulators is also suggested.

Purine Nucleotide Availability Regulates mTORC1 Activity through the Rheb GTPase

Pharmacologic agents that interfere with nucleotide metabolism constitute an important class of anticancer agents. Recent studies have demonstrated that mTOR complex 1 (mTORC1) inhibitors suppress de novo biosynthesis of pyrimidine and purine nucleotides. Here, we demonstrate that mTORC1 itself is suppressed by drugs that reduce intracellular purine nucleotide pools. Cellular treatment with AG2037, an inhibitor of the purine biosynthetic enzyme GARFT, profoundly inhibits mTORC1 activity via a reduction in the level of GTP-bound Rheb, an obligate upstream activator of mTORC1, because of a reduction in intracellular guanine nucleotides. AG2037 treatment provokes both mTORC1 inhibition and robust tumor growth suppression in mice bearing non-small-cell lung cancer (NSCLC) xenografts. These results indicate that alterations in purine nucleotide availability affect mTORC1 activity and suggest that inhibition of mTORC1 contributes to the therapeutic effects of purine biosynthesis inhibitors.

Metabolic Determinants of Sensitivity to Phosphatidylinositol 3-Kinase Pathway Inhibitor in Small-Cell Lung Carcinoma

Comprehensive genomic analysis has revealed that the PI3K/AKT/mTOR pathway is a feasible therapeutic target in small-cell lung carcinoma (SCLC). However, biomarkers to identify patients likely to benefit from inhibitors of this pathway have not been identified. Here, we show that metabolic features determine sensitivity to the PI3K/mTOR dual inhibitor gedatolisib in SCLC cells. Substantial phosphatidyl lipid analysis revealed that a specific phosphatidylinositol (3,4,5)-trisphosphate (PIP₃) subspecies lipid product PIP₃ (38:4) is predictive in assessing sensitivity to PI3K/mTOR dual inhibitor. Notably, we found that higher amounts of purine-related aqueous metabolites such as hypoxanthine, which are characteristic of SCLC biology, lead to resistance to PI3K pathway inhibition. In addition, the levels of the mRNA encoding hypoxanthine phosphoribosyl transferase 1, a key component of the purine salvage pathway, differed significantly between SCLC cells sensitive or resistant to gedatolisib. Moreover, complementation with purine metabolites could reverse the vulnerability to targeting of the PI3K pathway in SCLC cells normally sensitive to gedatolisib. These results indicate that the resistance mechanism of PI3K pathway inhibitors is mediated by the activation of the purine salvage pathway, supplying purine resource to nucleotide biosynthesis. Metabolomics is a powerful approach for finding novel therapeutic biomarkers in SCLC treatment.Significance: These findings identify features that determine sensitivity of SCLC to PI3K pathway inhibition and support metabolomics as a tool for finding novel therapeutic biomarkers. Cancer Res; 78(9); 2179-90. ©2018 AACR.