Phase I Dose-Escalation Study of Taselisib, an Oral PI3K Inhibitor, in Patients with Advanced Solid Tumors

Genetic dependencies associated with transcription factor activities in human cancer cell lines

Transcription factors (TFs) are important mediators of aberrant transcriptional programs in cancer cells. In this study, we focus on TF activity (TFa) as a biomarker for cell-line-selective anti-proliferative effects, in that high TFa predicts sensitivity to loss of function of a given gene (i.e., genetic dependencies [GDs]). Our linear-regression-based framework identifies 3,047 pan-cancer and 3,952 cancer-type-specific candidate TFa-GD associations from cell line data, which are then cross-examined for impact on survival in patient cohorts. One of the most prominent biomarkers is TEAD1 activity, whose associations with its predicted GDs are validated through experimental evidence as proof of concept. Overall, these TFa-GD associations represent an attractive resource for identifying innovative, biomarker-driven hypotheses for drug discovery programs in oncology.

PIK3CA mutation as an acquired resistance driver to EGFR-TKIs in non-small cell lung cancer: Clinical challenges and opportunities

Epithelial growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have significantly enhanced the treatment outcomes in non-small cell lung cancer (NSCLC) patients harboring EGFR mutations. However, the occurrence of acquired resistance to EGFR-TKIs is an unavoidable outcome observed in these patients. Disruption of the PI3K/AKT/mTOR signaling pathway can contribute to the emergence of resistance to EGFR TKIs in lung cancer. The emergence of PIK3CA mutations following treatment with EGFR-TKIs can lead to resistance against EGFR-TKIs. This review provides an overview of the current perspectives regarding the involvement of PI3K/AKT/mTOR signaling in the development of lung cancer. Furthermore, we outline the state-of-the-art therapeutic strategies targeting the PI3K/AKT/mTOR signaling pathway in lung cancer. We highlight the role of PIK3CA mutation as an acquired resistance mechanism against EGFR-TKIs in EGFR-mutant NSCLC. Crucially, we explore therapeutic strategies targeting PIK3CA-mediated resistance to EGFR TKIs in lung cancer, aiming to optimize the effectiveness of treatment.

Hormone, Targeted, and Combinational Therapies for Breast Cancers: From Humans to Dogs

Breast cancer (BC) is the most frequent cancer in women. In female dogs, canine mammary gland tumor (CMT) is also the leading neoplasm. Comparative oncology indicates similar tumor behaviors between human BCs (HBCs) and CMTs. Therefore, this review summarizes the current research in hormone and targeted therapies and describes the future prospects for HBCs and CMTs. For hormone receptor-expressing BCs, the first medical intervention is hormone therapy. Monoclonal antibodies against Her2 are proposed for the treatment of Her2+ BCs. However, the major obstacle in hormone therapy or monoclonal antibodies is drug resistance. Therefore, increasing alternatives have been developed to overcome these difficulties. We systemically reviewed publications that reported inhibitors targeting certain molecules in BC cells. The various treatment choices for humans decrease mortality in females with BC. However, the development of hormone or targeted therapies in veterinary medicine is still limited. Even though some clinical trials have been proposed, severe side effects and insufficient case numbers might restrict further explorations. This difficulty highlights the urgent need to develop updated hormone/targeted therapy or novel immunotherapies. Therefore, exploring new therapies to provide more precise use in dogs with CMTs will be the focus of future research. Furthermore, due to the similarities shared by humans and dogs, well-planned prospective clinical trials on the use of combinational or novel immunotherapies in dogs with CMTs to obtain solid results for both humans and dogs can be reasonably anticipated in the future.

Facts and Hopes on RAS Inhibitors and Cancer Immunotherapy

Although the past decade has seen great strides in the development of immunotherapies that reactivate the immune system against tumors, there have also been major advances in the discovery of drugs blocking oncogenic drivers of cancer growth. However, there has been very little progress in combining immunotherapies with drugs that target oncogenic driver pathways. Some of the most important oncogenes in human cancer encode RAS family proteins, although these have proven challenging to target. Recently drugs have been approved that inhibit a specific mutant form of KRAS: G12C. These have improved the treatment of patients with lung cancer harboring this mutation, but development of acquired drug resistance after initial responses has limited the impact on overall survival. Because of the immunosuppressive nature of the signaling network controlled by oncogenic KRAS, targeted KRAS G12C inhibition can indirectly affect antitumor immunity, and does so without compromising the critical role of normal RAS proteins in immune cells. This serves as a rationale for combination with immune checkpoint blockade, which can provide additional combinatorial therapeutic benefit in some preclinical cancer models. However, in clinical trials, combination of KRAS G12C inhibitors with PD-(L)1 blockade has yet to show improved outcome, in part due to treatment toxicities. A greater understanding of how oncogenic KRAS drives immune evasion and how mutant-specific KRAS inhibition impacts the tumor microenvironment can lead to novel approaches to combining RAS inhibition with immunotherapies.

HS-10352 in hormone receptor-positive, HER2-negative advanced breast cancer: A phase 1 dose-escalation trial

BACKGROUND

Approximately 40% of patients with hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer (ABC) exhibit PIK3CA mutations.

AIMS

This study aims to evaluate the safety, tolerability, pharmacokinetics, and preliminary antitumor activity of HS-10352, a selective PI3Kα inhibitor, in this patient population.

MATERIALS AND METHODS

Conducted as a phase 1 dose-escalation trial, HS-10352 was administered orally once-daily (QD) at dose levels of 2, 4, 6, and 8 mg. The primary endpoints were dose-limiting toxicity (DLT) and the maximum tolerated dose (MTD). This study is registered at ClinicalTrials.gov (NCT04631835).

RESULTS

Between August 2020 and March 2022, a total of 18 female patients were enrolled. DLT, manifested as hyperglycemia, occurred in two patients in the 8 mg QD group, establishing an MTD of 6 mg QD. The most common treatment-related adverse events were hyperglycemia (88.9%) and weight loss (61.3%). In the 6 mg QD group, four patients (66.7%) had a partial response (PR), and one (16.7%) had stable disease (SD). Among the four patients with PIK3CA mutated tumors in this dosage group, three (75.0%) had PR and one (25.0%) had SD. The median progression-free survival was not reached (95% confidence interval, 11.1-NA).

DISCUSSION AND CONCLUSION

HS-10352 at 6 mg QD was well-tolerated in patients with HR-positive, HER2-negative ABC, and showed preliminary antitumor activity in patients with PIK3CA mutated tumors. These findings support the further clinical development of HS-10352.

The emerging role of PI3K inhibitors for solid tumour treatment and beyond

Phosphoinositide 3-kinases (PI3Ks) play a central role in tumourigenesis with recurrent activating mutations of its p110α subunit (PIK3CA) identified in several tumours. Although several PI3K inhibitors are approved for haematological malignancies, only alpelisib was approved in solid tumours and for the treatment of PIK3CA-related overgrowth spectrum (PROS) syndrome. Traditional PI3K inhibitors inhibit both wild-type and mutant PI3K with almost equal potency, thus limiting their efficacy due to on-target toxicity. Since the initiation of phase I clinical trials investigating next generation allosteric mutant and isoform selective PIK3CA inhibitors, there has been a surge in interest in PIK3CA targeting in solid tumours. Preclinical characterisation of these compounds showed that maximal mutant protein inhibition fails to elicit metabolic and glucose homoeostasis dysregulation, one of the dose limiting toxicities of both selective and pan PI3K inhibitors. While extreme selectivity can be hypothesised to grant activity and safety advantage to these novel agents, on the other hand reduced benefit can be speculated for patients harbouring multiple or rare PIK3CA mutations. This review summarises the current understanding of PI3K alterations and the state-of-the-art treatment strategies in PI3K driven solid tumours, while also exploring the potential intrinsic and acquired resistance mechanisms to these agents, and the emerging role of mutant selective PIK3CA inhibitors.

Discovery of 4-oxo-4,5-dihydropyrazolo[1,5-a]quinoxaline-7-carboxamide derivatives as PI3Kα inhibitors via virtual screening and docking-based structure optimization

Compound 1 with pyrazolo[1,5-a]quinoxalin-4(5H)-one scaffold was identified as a PI3Kα inhibitor hit via virtual screening strategy. Additional similarity search and molecular docking based structural modification yielded a novel series of pyrazolo[1,5-a]quinoxalin-4(5H)-one derivatives. The most potent compound 49b exhibited remarkably improved PI3Kα inhibitory activity with IC₅₀ value of 0.24 μM and moderate to good isoform selectivity over other class I PI3K isoforms. In addition, 49b significantly inhibited the proliferation of Kasumi-1 and T47D cells with IC₅₀ value of 1.64 and 1.82 μM, respectively. Further PK study demonstrated that it has favorable pharmacokinetic profiles (AUC_0-t = 3294.05 ng·h/mL at 5.0 mg/kg PO, F = 91.8%). All these data indicated that compound 49b was a promising PI3Kα inhibitor with beneficial drug-like properties and merited further development.

Recent Advances with Precision Medicine Treatment for Breast Cancer including Triple-Negative Sub-Type

Breast cancer is a heterogeneous disease with different molecular subtypes. Breast cancer is the second leading cause of mortality in woman due to rapid metastasis and disease recurrence. Precision medicine remains an essential source to lower the off-target toxicities of chemotherapeutic agents and maximize the patient benefits. This is a crucial approach for a more effective treatment and prevention of disease. Precision-medicine methods are based on the selection of suitable biomarkers to envision the effectiveness of targeted therapy in a specific group of patients. Several druggable mutations have been identified in breast cancer patients. Current improvements in omics technologies have focused on more precise strategies for precision therapy. The development of next-generation sequencing technologies has raised hopes for precision-medicine treatment strategies in breast cancer (BC) and triple-negative breast cancer (TNBC). Targeted therapies utilizing immune checkpoint inhibitors (ICIs), epidermal growth factor receptor inhibitor (EGFRi), poly(ADP-ribose) polymerase inhibitor (PARPi), antibody-drug conjugates (ADCs), oncolytic viruses (OVs), glucose transporter-1 inhibitor (GLUT1i), and targeting signaling pathways are potential treatment approaches for BC and TNBC. This review emphasizes the recent progress made with the precision-medicine therapy of metastatic breast cancer and TNBC.

Antitumor activity of the PI3K δ-sparing inhibitor MEN1611 in PIK3CA mutated, trastuzumab-resistant HER2 + breast cancer

PURPOSE

Dysregulation of the PI3K pathway is one of the most common events in breast cancer. Here we investigate the activity of the PI3K inhibitor MEN1611 at both molecular and phenotypic levels by dissecting and comparing its profile and efficacy in HER2 + breast cancer models with other PI3K inhibitors.

METHODS

Models with different genetic backgrounds were used to investigate the pharmacological profile of MEN1611 against other PI3K inhibitors. In vitro studies evaluated cell viability, PI3K signaling, and cell death upon treatment with MEN1611. In vivo efficacy of the compound was investigated in cell line- and patient-derived xenografts models.

RESULTS

Consistent with its biochemical selectivity, MEN1611 demonstrated lower cytotoxic activity in a p110δ-driven cellular model when compared to taselisib, and higher cytotoxic activity in the p110β-driven cellular model when compared to alpelisib. Moreover, MEN1611 selectively decreased the p110α protein levels in PIK3CA mutated breast cancer cells in a concentration- and proteasome-dependent manner. In vivo, MEN1611 monotherapy showed significant and durable antitumor activity in several trastuzumab-resistant PIK3CA-mutant HER2 + PDX models. The combination of trastuzumab and MEN1611 significantly improved the efficacy compared to single agent treatment.

CONCLUSIONS

The profile of MEN1611 and its antitumoral activity suggest an improved profile as compared to pan-inhibitors, which are limited by a less than ideal safety profile, and isoform selective molecules, which may potentially promote development of resistance mechanisms. The compelling antitumor activity in combination with trastuzumab in HER2 + trastuzumab-resistant, PIK3CA mutated breast cancer models is at the basis of the ongoing B-Precise clinical trial (NCT03767335).

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

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

Clinical Evidence of Circulating Tumor DNA Application in Aggressive Breast Cancer

Breast cancer is clinically and biologically heterogeneous and is classified into different subtypes according to the molecular landscape of the tumor. Triple-negative breast cancer is a subtype associated with higher tumor aggressiveness, poor prognosis, and poor response to treatment. In metastatic breast cancer, approximately 6% to 10% of new breast cancer cases are initially staged IV (de novo metastatic disease). The number of metastatic recurrences is estimated to be 20-30% of all existing breast tumor cases, whereby the need to develop specific genetic markers to improve the prognosis of patients suffering from these deadly forms of breast cancer. As an alternative, liquid biopsy methods can minutely identify the molecular architecture of breast cancer, including aggressive forms, which provides new perspectives for more precise diagnosis and more effective therapeutics. This review aimed to summarize the current clinical evidence for the application of circulating tumor DNA in managing breast cancer by detailing the increased usefulness of this biomarker as a diagnostic, prognostic, monitoring, and surveillance marker for breast cancer.

PIK3CA mutations in breast cancer: A Tunisian series

BACKGROUND

The aim of this study was to analyze PIK3CA mutations in exons 9 and 20 in breast cancers (BCs) and their association with clinicopathological characteristics.

METHODS

Mutational analysis of PIK3CA exon 9 and 20 was performed by Sanger sequencing in 54 primary BCs of Tunisian women. The associations of PIK3CA mutations with clinicopathological characteristics were analyzed.

RESULTS

Fifteen exon 9 and exon 20 PIK3CA variants were identified in 33/54 cases (61%). PIK3CA mutations including pathogenic (class 5/Tier I) or likely pathogenic (class 4/Tier II) occurred in 24/54 cases (44%): 17/24 cases (71%) in exon 9, 5/24 cases (21%) in exon 20 and 2/24 cases (8%) in both exons. Of these 24 cases, 18 (75%) carried at least one of the three hot spot mutations: E545K (in 8 cases), H1047R (in 4 cases), E542K (in 3 cases), E545K/E542K (in one case), E545K/H1047R (in one case) and P539R/H1047R (in one case). Pathogenic PIK3CA mutations were associated with negative lymph node status (p = 0.027). Age distribution, histological SBR tumor grading, estrogen and progesterone receptors, human epidermal growth factor receptor 2, and molecular classification were not correlated with PIK3CA mutations (p > 0.05).

CONCLUSION

The frequency of somatic PIK3CA mutations in BCs of Tunisian women is slightly higher than that of BCs of Caucasian women and more observed in exon 9 than in exon 20. PIK3CA mutated status is associated with negative lymph node status. These data need to be confirmed in larger series.

IQ Motif Containing GTPase Activating Proteins (IQGAPs), A-Kinase Anchoring Proteins (AKAPs) and Kinase Suppressor of Ras Proteins (KSRs) in Scaffolding Oncogenic Pathways and Their Therapeutic Potential

Scaffolding proteins colocalize interacting partners on their surface and facilitate complex formation. They have multiple domains and motifs, which provide binding sites for various molecules. This property of scaffolding proteins helps in the orderly transduction of signals. Abnormal signal transduction is frequently observed in cancers, which can also be attributed to the altered functionality of scaffolding proteins. IQ motif containing GTPase activating proteins (IQGAPs), kinase suppressor of Ras (KSR), and A-kinase anchoring proteins (AKAPs) tether oncogenic pathways RAS/RAF/MEK/ERK, PI3K/AKT, Hippo, Wnt, and CDC42/RAC to them. Scaffolding proteins are attractive drug targets as they are the controlling hub for multiple pathways and regulate crosstalk between them. The first part of this review describes the human scaffolding proteins known to play a role in oncogenesis, pathways altered by them, and the impact on oncogenic processes. The second part provides information on the therapeutic potential of scaffolding proteins and future possibilities. The information on the explored and unexplored areas of the therapeutic potential of scaffolding proteins will be equally helpful for biologists and chemists.

Small molecule inhibitors targeting the cancers

Compared with traditional therapies, targeted therapy has merits in selectivity, efficacy, and tolerability. Small molecule inhibitors are one of the primary targeted therapies for cancer. Due to their advantages in a wide range of targets, convenient medication, and the ability to penetrate into the central nervous system, many efforts have been devoted to developing more small molecule inhibitors. To date, 88 small molecule inhibitors have been approved by the United States Food and Drug Administration to treat cancers. Despite remarkable progress, small molecule inhibitors in cancer treatment still face many obstacles, such as low response rate, short duration of response, toxicity, biomarkers, and resistance. To better promote the development of small molecule inhibitors targeting cancers, we comprehensively reviewed small molecule inhibitors involved in all the approved agents and pivotal drug candidates in clinical trials arranged by the signaling pathways and the classification of small molecule inhibitors. We discussed lessons learned from the development of these agents, the proper strategies to overcome resistance arising from different mechanisms, and combination therapies concerned with small molecule inhibitors. Through our review, we hoped to provide insights and perspectives for the research and development of small molecule inhibitors in cancer treatment.

Growth‐rate model predicts in vivo tumor response from in vitro data

A major challenge in oncology drug development is to elucidate why drugs that show promising results in cancer cell lines in vitro fail in mouse studies or human trials. One of the fundamental steps toward solving this problem is to better predict how in vitro potency translates into in vivo efficacy. A common approach to infer whether a model will respond in vivo is based on in vitro half‐maximal inhibitory concentration values (IC₅₀), but yields limited quantitative comparison between cell lines and drugs, potentially because cell division and death rates differ between cell lines and in vivo models. Other methods based either on mechanistic modeling or machine learning require molecular insights or extensive training data, limiting their use for early drug development. To address these challenges, we propose a mathematical model integrating in vitro growth rate inhibition values with pharmacokinetic parameters to estimate in vivo drug response. Upon calibration with a drug‐specific factor, our model yields precise estimates of tumor growth rate inhibition for in vivo studies based on in vitro data. We then demonstrate how our model can be used to study dosing schedules and perform sensitivity analyses. In addition, it provides meaningful metrics to assess association with genotypes and guide clinical trial design. By relying on commonly collected data, our approach shows great promise for optimizing drug development, better characterizing the efficacy of novel molecules targeting proliferation, and identifying more robust biomarkers of sensitivity while limiting the number of in vivo experiments.

Novel Systemic Treatment Modalities Including Immunotherapy and Molecular Targeted Therapy for Recurrent and Metastatic Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinomas (HNSCCs) are the sixth most common cancers worldwide. More than half of patients with HNSCC eventually experience disease recurrence and/or metastasis, which can threaten their long-term survival. HNSCCs located in the oral cavity and larynx are usually associated with tobacco and/or alcohol use, whereas human papillomavirus (HPV) infection, particularly HPV16 infection, is increasingly recognized as a cause of oropharyngeal HNSCC. Despite clinical, histologic, and molecular differences between HPV-positive and HPV-negative HNSCCs, current treatment approaches are the same. For recurrent disease, these strategies include chemotherapy, immunotherapy with PD-1-inhibitors, or a monoclonal antibody, cetuximab, that targets epidermal growth factor; these therapies can be administered either as single agents or in combination. However, these treatment strategies carry a high risk of toxic side effects; therefore, more effective and less toxic treatments are needed. The landscape of HNSCC therapy is changing significantly; numerous clinical trials are underway to test novel therapeutic options like adaptive cellular therapy, antibody-drug conjugates, new targeted therapy agents, novel immunotherapy combinations, and therapeutic vaccines. This review helps in understanding the various developments in HNSCC therapy and sheds light on the path ahead in terms of further research in this field.

Genomic landscape of lymphatic malformations: a case series and response to the PI3Kα inhibitor alpelisib in an N-of-1 clinical trial

Background

Lymphatic malformations (LMs) often pose treatment challenges due to a large size or a critical location that could lead to disfigurement, and there are no standardized treatment approaches for either refractory or unresectable cases.

Methods

We examined the genomic landscape of a patient cohort of LMs (n = 30 cases) that underwent comprehensive genomic profiling using a large-panel next-generation sequencing assay. Immunohistochemical analyses were completed in parallel.

Results

These LMs had low mutational burden with hotspot PIK3CA mutations (n = 20) and NRAS (n = 5) mutations being most frequent, and mutually exclusive. All LM cases with Kaposi sarcoma-like (kaposiform) histology had NRAS mutations. One index patient presented with subacute abdominal pain and was diagnosed with a large retroperitoneal LM harboring a somatic PIK3CA gain-of-function mutation (H1047R). The patient achieved a rapid and durable radiologic complete response, as defined in RECIST1.1, to the PI3Kα inhibitor alpelisib within the context of a personalized N-of-1 clinical trial (NCT03941782). In translational correlative studies, canonical PI3Kα pathway activation was confirmed by immunohistochemistry and human LM-derived lymphatic endothelial cells carrying an allele with an activating mutation at the same locus were sensitive to alpelisib treatment in vitro, which was demonstrated by a concentration-dependent drop in measurable impedance, an assessment of cell status.

Conclusions

Our findings establish that LM patients with conventional or kaposiform histology have distinct, yet targetable, driver mutations.

Funding

R.P. and W.A. are supported by awards from the Levy-Longenbaugh Fund. S.G. is supported by awards from the Hugs for Brady Foundation. This work has been funded in part by the NCI Cancer Center Support Grants (CCSG; P30) to the University of Arizona Cancer Center (CA023074), the University of New Mexico Comprehensive Cancer Center (CA118100), and the Rutgers Cancer Institute of New Jersey (CA072720). B.K.M. was supported by National Science Foundation via Graduate Research Fellowship DGE-1143953.

Clinical trial number

NCT03941782.

Neoadjuvant afatinib with paclitaxel for triple-negative breast cancer and the molecular characteristics in responders and non-responders

BACKGROUND

The prognosis of triple-negative breast cancer (TNBC) is worse and a major proportion of TNBC expresses epidermal growth factor receptor (EGFR). Afatinib can inhibit EGFR signal pathway; however, its treatment effect for TNBC is unknown. Thus, we aimed to assess the efficacy and biomarkers of afatinib in combination with paclitaxel in a neoadjuvant setting.

METHODS

Patients with stage II to III TNBC were enrolled. They received 40 mg of afatinib daily for 14 days, followed by daily afatinib and weekly paclitaxel (80 mg/m²) every 21 days for four to six cycles. To explore the mechanisms of responsiveness and non-responsiveness, 409 cancer-associated genes were sequenced.

RESULTS

Twenty-one patients were enrolled and one patient achieved a complete clinical response; however, a 2 mm residual tumor was noted in the surgical specimen. Overall, 33.0% patients were responders. Fifteen patients received molecular testing. No activated mutation of EGFR or Her2 were found. Activated PI3K or JAK2 pathway were trended to associate with non-responder (p = 0.057). Mutation of homologous recombination (HR) genes were correlated with non-responsiveness (p = 0.005). Seven patients did not have altered PI3K, JAK2 or HR pathway; six (85.7%) of them were responder. Patients with the amplified DAXX gene was associated with a favorable trend of response (p = 0.109).

CONCLUSIONS

Adding afatinib to neoadjuvant paclitaxel generated a modest effect in TNBC. Exploratory molecular analysis suggested that activated PI3K, JAK2 pathways and mutation of HR genes were associated with therapeutic non-responsiveness, and amplification of DAXX genes was associated with responsiveness to afatinib in combination with paclitaxel.

Quantitative systems pharmacology model-based investigation of adverse gastrointestinal events associated with prolonged treatment with PI3-kinase inhibitors

Several PI3K inhibitors are in clinical development for the treatment of various forms of cancers, including pan-PI3K inhibitors targeting all four PI3K isoforms (α, β, γ, and δ), and isoform-selective inhibitors. Diarrhea and immune-mediated colitis are among the adverse events observed with PI3K inhibition which limits the maximal tolerated dose. A quantitative systems pharmacology model was developed to investigate PI3K-inhibitor-induced colitis. The effects of individual PI3K isoforms on relevant cellular pathways were incorporated into a mechanistic representation of mucosal inflammation. A virtual clinical population captures the observed clinical variability in the onset timing and rates of diarrhea and colitis for seven clinically tested PI3K inhibitors. Model-based analysis suggests that colitis development is governed by both the inhibition of PI3Kδ, which drives T cell differentiation and proliferation, and PI3Kα, which regulates epithelial barrier integrity. Specifically, when PI3Kα is inhibited below a given threshold, epithelial barrier dysfunction precipitates an exaggerated T effector response due to PI3Kδ-inhibition, leading to risk of diarrhea and colitis. This synergy explains why the lowest diarrhea and colitis rates are seen with the weakest PI3Kδ inhibition (alpelisib), and higher rates are seen with strong PI3Kδ inhibition if PI3Kα is even mildly inhibited (e.g., idelalisib), whereas strong PI3Kδ inhibition in the absence of PI3Kα inhibition does not result in high colitis rates (umbralisib). Thus, the model-based analysis suggests that PI3Kα and δ inhibition play unique but synergistic roles in driving colitis. Finally, we explore if and how dose-regimen might influence colitis rates for molecules that inhibit both PI3Kα and PI3Kδ.

PI3K Inhibitors in Advanced Breast Cancer: The Past, The Present, New Challenges and Future Perspectives

Breast cancer is the leading cause of death in the female population and despite significant efforts made in diagnostic approaches and treatment strategies adopted for advanced breast cancer, the disease still remains incurable. Therefore, development of more effective systemic treatments constitutes a crucial need. Recently, several clinical trials were performed to find innovative predictive biomarkers and to improve the outcome of metastatic breast cancer through innovative therapeutic algorithms. In the pathogenesis of breast cancer, the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB/AKT)-mammalian target of rapamycin (mTOR) axis is a key regulator of cell proliferation, growth, survival, metabolism, and motility, making it an interest and therapeutic target. Nevertheless, the PI3K/AKT/mTOR cascade includes a complex network of biological events, needing more sophisticated approaches for their use in cancer treatment. In this review, we described the rationale for targeting the PI3K pathway, the development of PI3K inhibitors and the future treatment directions of different breast cancer subtypes in the metastatic setting.

Phase II Study of Taselisib in PIK3CA-Mutated Solid Tumors Other Than Breast and Squamous Lung Cancer: Results From the NCI-MATCH ECOG-ACRIN Trial (EAY131) Subprotocol I

PURPOSE

PIK3CA mutations frequently contribute to oncogenesis in solid tumors. Taselisib, a potent and selective inhibitor of phosphoinositide 3-kinase, has demonstrated clinical activity in PIK3CA-mutant breast cancer. Whether PIK3CA mutations predict sensitivity to taselisib in other cancer types is unknown. National Cancer Institute-Molecular Analysis for Therapy Choice Arm EAY131-I is a single-arm, phase II study of the safety and efficacy of taselisib in patients with advanced cancers.

METHODS

Eligible patients had tumors with an activating PIK3CA mutation. Patients with breast or squamous cell lung carcinoma, or whose cancer had KRAS or PTEN mutations, were excluded. Patients received taselisib 4 mg, orally once daily continuously, until disease progression or unacceptable toxicity. The primary end point was objective response rate. Secondary end points included progression-free survival (PFS), 6-month PFS, overall survival (OS), and identification of predictive biomarkers.

RESULTS

Seventy patients were enrolled, and 61 were eligible and initiated protocol therapy. Types of PIK3CA mutations included helical 41 of 61 (67%), kinase 11 of 61 (18%), and other 9 of 61 (15%). With a median follow-up of 35.7 months, there were no complete or partial responses. Six-month PFS was 19.9% (90% CI, 12.0 to 29.3) and median PFS was 3.1 months (90% CI, 1.8 to 3.7). Six-month OS was 60.7% (90% CI, 49.6 to 70.0) and median OS was 7.2 months (90% CI, 5.9 to 10.0). Individual comutations were too heterogeneous to correlate with clinical outcome. Fatigue, diarrhea, nausea, and hyperglycemia were the most common toxicities, and most were grade 1 and 2.

CONCLUSION

In this study, taselisib monotherapy had very limited activity in a heterogeneous cohort of heavily pretreated cancer patients with PIK3CA-mutated tumors; the presence of a PIK3CA mutation alone does not appear to be a sufficient predictor of taselisib activity.

RTK-Dependent Inducible Degradation of Mutant PI3Kα Drives GDC-0077 (Inavolisib) Efficacy

PIK3CA is one of the most frequently mutated oncogenes; the p110a protein it encodes plays a central role in tumor cell proliferation. Small-molecule inhibitors targeting the PI3K p110a catalytic subunit have entered clinical trials, with early-phase GDC-0077 studies showing antitumor activity and a manageable safety profile in patients with PIK3CA-mutant breast cancer. However, preclinical studies have shown that PI3K pathway inhibition releases negative feedback and activates receptor tyrosine kinase signaling, reengaging the pathway and attenuating drug activity. Here we discover that GDC-0077 and taselisib more potently inhibit mutant PI3K pathway signaling and cell viability through unique HER2-dependent mutant p110a degradation. Both are more effective than other PI3K inhibitors at maintaining prolonged pathway suppression. This study establishes a new strategy for identifying inhibitors that specifically target mutant tumors by selective degradation of the mutant oncoprotein and provide a strong rationale for pursuing PI3Kα degraders in patients with HER2-positive breast cancer. SIGNIFICANCE: The PI3K inhibitors GDC-0077 and taselisib have a unique mechanism of action; both inhibitors lead to degradation of mutant p110a protein. The inhibitors that have the ability to trigger specific degradation of mutant p110a without significant change in wild-type p110a protein may result in improved therapeutic index in PIK3CA-mutant tumors.See related commentary by Vanhaesebroeck et al., p. 20.This article is highlighted in the In This Issue feature, p. 1.

Targeting PI3K/Akt signal transduction for cancer therapy

The phosphatidylinositol 3-kinase (PI3K)/Akt pathway plays a crucial role in various cellular processes and is aberrantly activated in cancers, contributing to the occurrence and progression of tumors. Examining the upstream and downstream nodes of this pathway could allow full elucidation of its function. Based on accumulating evidence, strategies targeting major components of the pathway might provide new insights for cancer drug discovery. Researchers have explored the use of some inhibitors targeting this pathway to block survival pathways. However, because oncogenic PI3K pathway activation occurs through various mechanisms, the clinical efficacies of these inhibitors are limited. Moreover, pathway activation is accompanied by the development of therapeutic resistance. Therefore, strategies involving pathway inhibitors and other cancer treatments in combination might solve the therapeutic dilemma. In this review, we discuss the roles of the PI3K/Akt pathway in various cancer phenotypes, review the current statuses of different PI3K/Akt inhibitors, and introduce combination therapies consisting of signaling inhibitors and conventional cancer therapies. The information presented herein suggests that cascading inhibitors of the PI3K/Akt signaling pathway, either alone or in combination with other therapies, are the most effective treatment strategy for cancer.

EWSR1-WT1 Target Genes and Therapeutic Options Identified in a Novel DSRCT In Vitro Model

Simple Summary

Desmoplastic small round cell tumor (DSRCT) is an extremely rare soft tissue sarcoma arising in the abdomen of adolescents and young adults. This sarcoma is driven by a single genomic rearrangement, resulting in the expression of the EWSR1-WT1 fusion gene. No effective treatment exists for DSRCT patients, which highlights the need for preclinical models to study disease progression and drug sensitivity. The aim of this study is to develop a pre-clinical DSRCT in vitro model, which enables investigating the molecular target genes of the EWSR1-WT1 fusion gene and allows for medium-throughput drug screening to discover new therapeutic options.

Abstract

Desmoplastic small round cell tumor (DSRCT) is a rare and aggressive soft tissue sarcoma with a lack of effective treatment options and a poor prognosis. DSRCT is characterized by a chromosomal translocation, resulting in the EWSR1-WT1 gene fusion. The molecular mechanisms driving DSRCT are poorly understood, and a paucity of preclinical models hampers DSRCT research. Here, we establish a novel primary patient-derived DSRCT in vitro model, recapitulating the original tumor. We find that EWSR1-WT1 expression affects cell shape and cell survival, and we identify downstream target genes of the EWSR1-WT1 fusion. Additionally, this preclinical in vitro model allows for medium-throughput drug screening. We discover sensitivity to several drugs, including compounds targeting RTKs. MERTK, which has been described as a therapeutic target for several malignancies, correlates with EWSR1-WT1 expression. Inhibition of MERTK with the small-molecule inhibitor UNC2025 results in reduced proliferation of DSRCT cells in vitro, suggesting MERTK as a therapeutic target in DSRCT. This study underscores the usefulness of preclinical in vitro models for studying molecular mechanisms and potential therapeutic options.

A Prospective Cohort Study of Biomarkers in Squamous Cell Carcinoma of the Anal Canal (SCCAC) and their Influence on Treatment Outcomes

Background: Although Chemoradiation (CRT) is the curative treatment for SCCAC, many patients present primary resistance. Since it is a rare tumor, response predictors remain unknown.

Methods: We performed a prospective cohort study to evaluate biomarkers associated with CRT response, progression-free survival (PFS), and overall survival (OS). The primary endpoint was response at 6 months (m). Tumor DNA and HPV were analyzed by next-generation sequencing, while KI-67 and PD-L1 by immunohistochemistry in tumor tissue.

Results: Seventy-eight patients were recruited between October/2011 and December/2015, and 75 were response evaluable. The median age was 57 years, 65% (n=49) were stage III and 12% (n=9) were HIV positive (HIV+). At 6m, 62.7% (n=47) presented CR. On multivariate analyses, stage II patients were 4.7 more likely to achieve response than stage III (OR, 4.70; 95%CI, 1.36-16.30; p=0.015). HIV+ was associated with a worse response (OR, 5.72; 95%CI, 2.5-13.0; p<0.001). 5-year PFS and OS rates were 63.3% and 76.4%, respectively, with a median follow up of 66m. On multivariate analyses, older age (HR 1.06, p=0.022, 95%IC 1.01-1.11) and absence of CR at 6m (HR 3.36, p=0.007, 95%IC 1.39-8.09) were associated with inferior OS. The 5-year OS rate was 62.5% in HIV+ group compared to 78% among HIV- pts, although this difference was not statistically significant (p=0.4). PIK3CA, MET and TP53 mutations, HPV, Ki-67 expression, and PD-L1 expression, were not associated with PFS and OS.

Conclusions: Clinical stage III and HIV+ were associated with worse response to CRT at 6m. The absence of CR was the main factor associated with poor 5-year OS.

Fasting-mimicking diet blocks triple-negative breast cancer and cancer stem cell escape

Metastatic tumors remain lethal due to primary/acquired resistance to therapy or cancer stem cell (CSC)-mediated repopulation. We show that a fasting-mimicking diet (FMD) activates starvation escape pathways in triple-negative breast cancer (TNBC) cells, which can be identified and targeted by drugs. In CSCs, FMD lowers glucose-dependent protein kinase A signaling and stemness markers to reduce cell number and increase mouse survival. Accordingly, metastatic TNBC patients with lower glycemia survive longer than those with higher baseline glycemia. By contrast, in differentiated cancer cells, FMD activates PI3K-AKT, mTOR, and CDK4/6 as survival/growth pathways, which can be targeted by drugs to promote tumor regression. FMD cycles also prevent hyperglycemia and other toxicities caused by these drugs. These data indicate that FMD has wide and differential effects on normal, cancer, and CSCs, allowing the rapid identification and targeting of starvation escape pathways and providing a method potentially applicable to many malignancies.

The Importance of Being PI3K in the RAS Signaling Network

Ras proteins are essential mediators of a multitude of cellular processes, and its deregulation is frequently associated with cancer appearance, progression, and metastasis. Ras-driven cancers are usually aggressive and difficult to treat. Although the recent Food and Drug Administration (FDA) approval of the first Ras G12C inhibitor is an important milestone, only a small percentage of patients will benefit from it. A better understanding of the context in which Ras operates in different tumor types and the outcomes mediated by each effector pathway may help to identify additional strategies and targets to treat Ras-driven tumors. Evidence emerging in recent years suggests that both oncogenic Ras signaling in tumor cells and non-oncogenic Ras signaling in stromal cells play an essential role in cancer. PI3K is one of the main Ras effectors, regulating important cellular processes such as cell viability or resistance to therapy or angiogenesis upon oncogenic Ras activation. In this review, we will summarize recent advances in the understanding of Ras-dependent activation of PI3K both in physiological conditions and cancer, with a focus on how this signaling pathway contributes to the formation of a tumor stroma that promotes tumor cell proliferation, migration, and spread.

Targeting PI3K/AKT/mTOR Signaling Pathway in Breast Cancer

Breast cancer is the most frequently diagnosed cancer and the primary cause of cancer death in women worldwide. Although early diagnosis and cancer growth inhibition has significantly improved breast cancer survival rate over the years, there is a current need to develop more effective systemic treatments to prevent metastasis. One of the most commonly altered pathways driving breast cancer cell growth, survival, and motility is the PI3K/AKT/mTOR signaling cascade. In the past 30 years, a great surge of inhibitors targeting these key players has been developed at a rapid pace, leading to effective preclinical studies for cancer therapeutics. However, the central role of PI3K/AKT/mTOR signaling varies among diverse biological processes, suggesting the need for more specific and sophisticated strategies for their use in cancer therapy. In this review, we provide a perspective on the role of the PI3K signaling pathway and the most recently developed PI3K-targeting breast cancer therapies.

The present and future of PI3K inhibitors for cancer therapy

Phosphoinositide-3- kinase (PI3K) signaling regulates cellular proliferation, survival and metabolism, and its aberrant activation is one of the most frequent oncogenic events across human cancers. In the last few decades, research focused on the development of PI3K inhibitors, from preclinical tool compounds to the highly specific medicines approved to treat patients with cancer. Herein we discuss current paradigms for PI3K inhibitors in cancer therapy, focusing on clinical data and mechanisms of action. We also discuss current limitations in the use of PI3K inhibitors including toxicities and mechanisms of resistance, with specific emphasis on approaches aimed to improve their efficacy.

Significance of tumor mutation burden and immune infiltration in thymic epithelial tumors

Background

Thymic epithelial tumors (TETs) are relatively rare malignant thoracic tumors. Tumor mutation burden (TMB) and immune infiltration play important roles in tumorigenesis.

Methods

Research data was obtained using the Cancer Genome Atlas (TCGA) database to evaluate the landscape of tumor mutations, related factors, and relationship of prognosis. The CIBERSORT algorithm was used to evaluate immune cell infiltration in TETs and its relationship with TMB. Immune‐related differentially expressed genes (irDEGs) were identified. Hub irDEGs independently related to prognosis were analyzed using univariate and multivariate Cox proportional hazard models. A survival signature was constructed from hub irDEGs.

Results

A total of 122 patients were included in this study. GTF2I was the most common gene mutation. Higher TMB was significantly associated with the later stage, more advanced pathological type, and older age. The overall survival (OS) of patients in the low‐TMB group was significantly better. There was no significant correlation between TMB levels and PD‐L1 expression. Enrichment analysis showed that DEGs were mainly involved in the P13K–Akt signaling pathway. There were significant differences in macrophage and other types of immune cell infiltration between the high‐ and low‐TMB groups. CCR5, FASLG, and CD79A independently relating to prognosis were screened from 391 irDEGs. The low‐risk group had a significantly better prognosis than the high‐risk group based on the signature, which has a good predictive effect on OS.

Conclusions

In this study, TETs patients with high TMB had a significantly poor prognosis and an immune‐related gene signature was found to effectively evaluate the long‐term prognosis.

Phosphatidylinositol 3-kinase (PI3K) inhibitors: a recent update on inhibitor design and clinical trials (2016-2020)

Introduction: The phosphatidylinositol 3-kinase/protein kinase-B/mammalian target of rapamycin (PI3K/AKT/mTOR) signaling pathway plays a central role in regulating cell growth and proliferation and thus has been considered as effective anticancer drug targets. Many PI3K inhibitors have been developed and progressed to various stages of clinical trials, and some have been approved as anticancer treatment. In this review, we discuss the drug design and clinical development of PI3K inhibitors over the past 4 years. We review the selectivity and potency of 47 PI3K inhibitors. Structural determinants for increasing selectivity toward PI3K subtype-selectivity or mutant selectivity are discussed. Future research direction and current clinical development in combination therapy of inhibitors involved in PI3Ks are also discussed.Area covered: This review covers clinical trial reports and patent literature on PI3K inhibitors and their selectivity published between 2016 and 2020.Expert opinion: To PI3Kα mutants (E542K, E545K, and H1047R), it is highly desirable to design and develop mutant-specific PI3K inhibitors. It is also necessary to develop subtype-selective PI3Kα inhibitors to minimize toxicity. To reduce drug resistance and to improve efficacy, future studies should include combination therapy of PI3K inhibitors with existing anticancer drugs from different pathways.

IGF2 Mediates Resistance to Isoform-Selective-Inhibitors of the PI3K in HPV Positive Head and Neck Cancer

Simple Summary

In the current study, we delineate the molecular mechanisms of acquisition of resistance to two isoform-selective inhibitors of PI3K (isiPI3K), alpelisib and taselisib, in human papillomavirus positive head and neck cell lines. By comparing RNA sequencing of isiPI3K-sensitive tumor cells and their corresponding isiPI3K-acquired-resistant tumor cells, we found that overexpression of insulin growth factor 2 (IGF2) is associated with the resistance phenotype. We further demonstrated by gain and loss of function studies that IGF2 plays a causative role in limiting the sensitivity of human papillomavirus-positive head and neck cell lines. Moreover, we show that blocking IGF2 stimulation activity, using an inhibitor of the IGF1 receptor (IGF1R), enhances isiPI3K efficacy and displays a synergistic anti-tumor effect in vitro and superior anti-tumor activity ex vivo and in vivo.

Abstract

Over 50% of human papilloma positive head-and-neck cancer (HNC^HPV+) patients harbor genomic-alterations in PIK3CA, leading to hyperactivation of the phosphatidylinositol-4, 5-bisphosphate 3-kinase (PI3K) pathway. Nevertheless, despite PI3K pathway activation in HNC^HPV+ tumors, the anti-tumor activities of PI3K pathway inhibitors are moderate, mostly due to the emergence of resistance. Thus, for potent and long-term tumor management, drugs blocking resistance mechanisms should be combined with PI3K inhibitors. Here, we delineate the molecular mechanisms of the acquisition of resistance to two isoform-selective inhibitors of PI3K (isiPI3K), alpelisib (BYL719) and taselisib (GDC0032), in HNC^HPV+ cell lines. By comparing the transcriptional landscape of isiPI3K-sensitive tumor cells with that of their corresponding isiPI3K-acquired-resistant tumor cells, we found upregulation of insulin growth factor 2 (IGF2) in the resistant cells. Mechanistically, we show that upon isiPI3K treatment, isiPI3K-sensitive tumor cells upregulate the expression of IGF2 to induce cell proliferation via the activation of the IGF1 receptor (IGF1R). Stimulating tumor cells with recombinant IGF2 limited isiPI3K efficacy and released treated cells from S phase arrest. Knocking-down IGF2 with siRNA, or blocking IGF1R with AEW541, resulted in superior anti-tumor activity of isiPI3K in vitro and ex vivo. In vivo, the combination of isiPI3K and IGF1R inhibitor induced stable disease in mice bearing either tumors generated by the HNC^HPV+ UM-SCC47 cell line or HPV+ patient-derived xenografts. These findings indicate that IGF2 and the IGF2/IGF1R pathway may constitute new targets for combination therapies to enhance the efficacy of PI3K inhibitors for the treatment of HNC^HPV+.

Copanlisib for the Treatment of Malignant Lymphoma: Clinical Experience and Future Perspectives

Dysregulation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B/mammalian target of rapamycin signaling is common in both indolent and aggressive forms of malignant lymphoma, for which several targeted therapies have been developed. Copanlisib is a highly selective and potent intravenous pan-class I PI3K inhibitor that has demonstrated durable objective responses and a manageable safety profile in heavily pre-treated patients with indolent lymphomas. As a result, copanlisib monotherapy received accelerated approval from the US Food and Drug Administration for the treatment of adults with relapsed follicular lymphoma who have received at least two systemic therapies, and breakthrough designation for patients with pre-treated relapsed or refractory marginal zone lymphoma. Hyperglycemia and hypertension are among the most frequently reported adverse events with copanlisib monotherapy, and are infusion-related, transient, and manageable with standard therapies. Mild diarrhea is also a common adverse event with copanlisib monotherapy; there is no evidence of worsening severity of diarrhea, or serious gastrointestinal toxicities such as colitis or severe liver enzyme elevations, which have been reported with orally administered PI3K inhibitors. The intravenous route of administration and intermittent dosing schedule of copanlisib may support a favorable tolerability profile over continually administered oral alternatives. Ongoing studies of copanlisib in combination with rituximab and standard-of-care chemotherapy in patients with relapsed indolent lymphoma have the potential to support the use of copanlisib in the second-line setting, providing a much-needed additional therapeutic option in this underserved patient population.

PI3K inhibition in breast cancer: Identifying and overcoming different flavors of resistance

The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway is commonly deregulated in many human tumors, including breast cancer. Somatic mutations of the PI3K alpha catalytic subunit (PIK3CA) are the most common cause of pathway hyperactivation. Hence, several PI3K inhibitors have been investigated with one of them, alpelisib, recently approved for the treatment of endocrine sensitive, PIK3CA mutated, metastatic breast cancer. Unfortunately, all patients receiving a PI3K inhibitor eventually develop resistance to these compounds. Mechanisms of resistance include oncogenic PI3K alterations, pathway reactivation through upstream or downstream effectors and enhancement of parallel pro-survival pathways. We review the prognostic and predictive role of PI3K alterations in breast cancer, focusing on resistance to PI3K inhibitors and on biomarkers with potential clinical relevance. We also discuss combination strategies that may overcome resistance to PI3K inhibitors, thus increasing the efficacy of these drugs in breast cancer.

PI3K Inhibitors in Cancer: Clinical Implications and Adverse Effects

The phospatidylinositol-3 kinase (PI3K) pathway is a crucial intracellular signaling pathway which is mutated or amplified in a wide variety of cancers including breast, gastric, ovarian, colorectal, prostate, glioblastoma and endometrial cancers. PI3K signaling plays an important role in cancer cell survival, angiogenesis and metastasis, making it a promising therapeutic target. There are several ongoing and completed clinical trials involving PI3K inhibitors (pan, isoform-specific and dual PI3K/mTOR) with the goal to find efficient PI3K inhibitors that could overcome resistance to current therapies. This review focuses on the current landscape of various PI3K inhibitors either as monotherapy or in combination therapies and the treatment outcomes involved in various phases of clinical trials in different cancer types. There is a discussion of the drug-related toxicities, challenges associated with these PI3K inhibitors and the adverse events leading to treatment failure. In addition, novel PI3K drugs that have potential to be translated in the clinic are highlighted.

Cardiovascular toxicity of PI3Kα inhibitors

The phosphoinositide 3-kinases (PI3Ks) are a family of intracellular lipid kinases that phosphorylate the 3'-hydroxyl group of inositol membrane lipids, resulting in the production of phosphatidylinositol 3,4,5-trisphosphate from phosphatidylinositol 4,5-bisphosphate. This results in downstream effects, including cell growth, proliferation, and migration. The heart expresses three PI3K class I enzyme isoforms (α, β, and γ), and these enzymes play a role in cardiac cellular survival, myocardial hypertrophy, myocardial contractility, excitation, and mechanotransduction. The PI3K pathway is associated with various disease processes but is particularly important to human cancers since many gain-of-function mutations in this pathway occur in various cancers. Despite the development, testing, and regulatory approval of PI3K inhibitors in recent years, there are still significant challenges when creating and utilizing these drugs, including concerns of adverse effects on the heart. There is a growing body of evidence from preclinical studies revealing that PI3Ks play a crucial cardioprotective role, and thus inhibition of this pathway could lead to cardiac dysfunction, electrical remodeling, vascular damage, and ultimately, cardiovascular disease. This review will focus on PI3Kα, including the mechanisms underlying the adverse cardiovascular effects resulting from PI3Kα inhibition and the potential clinical implications of treating patients with these drugs, such as increased arrhythmia burden, biventricular cardiac dysfunction, and impaired recovery from cardiotoxicity. Recommendations for future directions for preclinical and clinical work are made, highlighting the possible role of PI3Kα inhibition in the progression of cancer-related cachexia and female sex and pre-existing comorbidities as independent risk factors for cardiac abnormalities after cancer treatment.

Signaling Pathways in Cancer: Therapeutic Targets, Combinatorial Treatments, and New Developments

Molecular alterations in cancer genes and associated signaling pathways are used to inform new treatments for precision medicine in cancer. Small molecule inhibitors and monoclonal antibodies directed at relevant cancer-related proteins have been instrumental in delivering successful treatments of some blood malignancies (e.g., imatinib with chronic myelogenous leukemia (CML)) and solid tumors (e.g., tamoxifen with ER positive breast cancer and trastuzumab for HER2-positive breast cancer). However, inherent limitations such as drug toxicity, as well as acquisition of de novo or acquired mechanisms of resistance, still cause treatment failure. Here we provide an up-to-date review of the successes and limitations of current targeted therapies for cancer treatment and highlight how recent technological advances have provided a new level of understanding of the molecular complexity underpinning resistance to cancer therapies. We also raise three basic questions concerning cancer drug discovery based on molecular markers and alterations of selected signaling pathways, and further discuss how combination therapies may become the preferable approach over monotherapy for cancer treatments. Finally, we consider novel therapeutic developments that may complement drug delivery and significantly improve clinical response and outcomes of cancer patients.

Ganglioside GT1b increases hyaluronic acid synthase 2 via PI3K activation with TLR2 dependence in orbital fibroblasts from thyroid eye disease patients

Thyroid eye disease (TED) is a complex autoimmune disease with a spectrum of signs. we previously reported that trisialoganglioside (GT)1b is significantly overexpressed in the orbital tissue of TED patients, and that exogenous GT1b strongly induced HA synthesis in orbital fibroblasts. However, the signaling pathway in GT1b-induced hyaluronic acid synthase (HAS) expression in orbital fibroblasts from TED patients have rarely been investigated. Here, we demonstrated that GT1b induced phosphorylation of Akt/mTOR in a dose-dependent manner in orbital fibroblasts from TED patients. Both co-treatment with a specific inhibitor for PI3K and siRNA knockdown of TLR2 attenuated GT1b-induced Akt phosphorylation. GT1b significantly induced HAS2 expression at both the transcriptional and translational level, which was suppressed by specific inhibitors of PI3K or Akt/mTOR, and by siRNA knockdown of TLR2. In conclusion, GT1b induced HAS2 in orbital fibroblasts from TED patients via activation of the PI3K-related signaling pathway, dependent on TLR2.

Research update on the anticancer effects of buparlisib

Buparlisib is a highly efficient and selective PI3K inhibitor and a member of the 2,6-dimorpholinopyrimidine-derived family of compounds. It selectively inhibits four isomers of PI3K, PI3Kα, PI3Kβ, PI3Kγ and PI3Kδ, by competitively binding the lipid kinase domain on adenosine 5'-triphosphate (ATP), and serves an important role in inhibiting proliferation, promoting apoptosis and blocking angiogenesis, predominantly by antagonizing the PI3K/AKT pathway. Buparlisib has been confirmed to have a clinical effect in patients with solid tumors and hematological malignancies. A global, phase II clinical trial with buparlisib and paclitaxel in head and neck squamous cell carcinoma has now been completed, with a manageable safety profile. Buparlisib currently has fast-track status with the United States Food and Drug Administration. The present review examined the biochemical structure, pharmacokinetic characteristics, preclinical data and ongoing clinical studies of buparlisib. The various mechanisms of influence of buparlisib in tumors, particularly in preclinical research, were summarized, providing a theoretical basis and direction for basic research on and clinical treatment with buparlisib.

Druggable targets meet oncogenic drivers: opportunities and limitations of target-based classification of tumors and the role of Molecular Tumor Boards

The therapeutic landscape of cancer is changing rapidly due to the growing number of approved drugs capable of targeting specific genetic alterations. This aspect, together with the development of noninvasive methods for the assessment of somatic mutations in the peripheral blood of patients, generated a growing interest toward a new tumor-agnostic classification system based on ‘predictive’ biomarkers. The current review article discusses this emerging alternative approach to the classification of cancer and its implications for the selection of treatments. It is suggested that different types of cancers sharing the same molecular profiles could benefit from the same targeted drugs. Although recent clinical trials have demonstrated that this approach cannot be generalized, there are also specific examples that demonstrate the clinical utility of this alternative vision. In this rapidly evolving scenario, a multidisciplinary approach managed by institutional Molecular Tumor Boards is fundamental to interpret the biological and clinical relevance of genetic alterations and the complexity of their relationship with treatment response.

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The identification of oncogenic drivers offers the opportunity to develop target-specific drugs.

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The inhibition of crucial pathways realizes the principle of druggable target to exploit cancer vulnerability.

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The approval of new anticancer agents based on target-based concept represents a paradigm shift in cancer therapy.

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However, only few drugs have been approved so far on an agnostic basis and the concept of biomarker cannot be generalized.

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Tumor Molecular Boards will have an increasing role in the identification of new therapeutic options in selected patients.

Identification of Core Prognosis-Related Candidate Genes in Chinese Gastric Cancer Population Based on Integrated Bioinformatics

Background

Gastric cancer (GC) is one of the leading causes of cancer-related mortality worldwide. There are great geographical differences in the incidence of GC, and somatic mutation rates of driver genes are also different. The present study is aimed at screening core prognosis-related candidate genes in Chinese gastric cancer population based on integrated bioinformatics for the early diagnosis and prognosis of GC.

Methods

In the present study, the differentially expressed genes (DEGs) in GC were identified using four microarray datasets from the Gene Expression Omnibus (GEO) database. The samples of these datasets were all from China. Functional enrichment analysis of DEGs was conducted to evaluate the underlying molecular mechanisms involved in GC. Protein-protein interaction (PPI) network and cytoHubba were performed to determine hub genes associated with GC. Gene Expression Profiling Interactive Analysis (GEPIA) and Human Protein Atlas (HPA) were performed to validate the hub genes.

Results

A total of 240 DEGs were obtained through the RRA method, including 80 upregulated genes and 160 downregulated genes. Upregulated genes were mainly enriched in extracellular matrix organization, extracellular matrix, and extracellular matrix structural constituent. The downregulated genes were mainly enriched in digestion, extracellular space, and oxidoreductase activity. The KEGG pathway enrichment analysis showed that the upregulated genes were mainly associated with ECM-receptor interaction, focal adhesion, and PI3K-Akt signaling pathway. And downregulated genes were mainly associated with the metabolism of xenobiotics by cytochrome P450, metabolic pathways, and gastric acid secretion. The transcriptional and translational expression levels of the genes including COL1A1, COL5A2, COL12A1, and VCAN were higher in GC tissues than normal tissues.

Conclusion

A total of four genes including COL1A1, COL5A2, COL12A1, and VCAN were considered potential GC biomarkers in the Chinese population. And ECM-receptor interaction, focal adhesion, and PI3K-Akt signaling pathway were revealed to be important mechanisms of GC. Our findings provide novel insights into the occurrence and progression of GC in the Chinese population.

A pharmacokinetic evaluation of alpelisib for the treatment of HR+, HER2-negative, PIK3CA-mutated advanced or metastatic breast cancer

Introduction: In most cases, metastatic breast cancer remains an incurable disease. A PIK3CA mutation is detected in 30-40% of all hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancers. PIK3CA activating mutations have been linked to endocrine resistance. PI3K inhibitors therefore offer promising new therapeutic options for this disease. Areas covered: This review discusses the pharmacologic properties, preclinical development, clinical efficacy, and safety profile of alpelisib, a PI3K inhibitor indicated in HR+/HER2 - PIK3CA-mutated advanced breast cancer, describing current therapeutic indication and open questions. Expert opinion: Following results of the SOLAR-1 trial, alpelisib became the first PI3K inhibitor approved by the U.S. Food and Drug Administration, in combination with fulvestrant, for postmenopausal women and men with HR+/HER2 - PIK3CA-mutated advanced breast cancer following progression on or after an endocrine-based regimen. This trial showed a substantial improvement in progression-free survival. However, given the side effects of alpelisib, the treatment decision should follow a thorough benefit-risk assessment. The BYLieve trial suggests alpelisib-fulvestrant benefit after progression on CDK 4/6 inhibitors. The identification of patients that are likely to benefit the most from PI3K inhibitors is still eagerly sought.

Comprehensive Genomic Profile of Heterogeneous Long Follow-Up Triple-Negative Breast Cancer and Its Clinical Characteristics Shows DNA Repair Deficiency Has Better Prognostic

Triple-negative breast cancer (TNBC) presents a marked diversity at the molecular level, which promotes a clinical heterogeneity that further complicates treatment. We performed a detailed whole exome sequencing profile of 29 Mexican patients with long follow-up TNBC to identify genomic alterations associated with overall survival (OS), disease-free survival (DFS), and pathologic complete response (PCR), with the aim to define their role as molecular predictive factors of treatment response and prognosis. We detected 31 driver genes with pathogenic mutations in TP53 (53%), BRCA1/2 (27%), CDKN1B (9%), PIK3CA (9%), and PTEN (9%), and 16 operative mutational signatures. Moreover, tumors with mutations in BRCA1/2 showed a trend of sensitivity to platinum salts. We found an association between deficiency in DNA repair and surveillance genes and DFS. Across all analyzed tumors we consistently found a heterogeneous molecular complexity in terms of allelic composition and operative mutational processes, which hampered the definition of molecular traits with clinical utility. This work contributes to the elucidation of the global molecular alterations of TNBC by providing accurate genomic data that may help forthcoming studies to improve treatment and survival. This is the first study that integrates genomic alterations with a long follow-up of clinical variables in a Latin American population that is an underrepresented ethnicity in most of the genomic studies.

Phase III randomized study of taselisib or placebo with fulvestrant in estrogen receptor-positive, PIK3CA-mutant, HER2-negative, advanced breast cancer: the SANDPIPER trial

BACKGROUND

The phase III SANDPIPER study assessed taselisib (GDC-0032), a potent, selective PI3K inhibitor, plus fulvestrant in estrogen receptor-positive, HER2-negative, PIK3CA-mutant locally advanced or metastatic breast cancer.

PATIENTS AND METHODS

Postmenopausal women with disease recurrence/progression during/after an aromatase inhibitor were randomized 2 : 1 to receive taselisib (4 mg; taselisib arm) or placebo (placebo arm) plus fulvestrant (500 mg). Stratification factors were visceral disease, endocrine sensitivity, and geographic region. Patients with PIK3CA-mutant tumors (central cobas® PIK3CA Mutation Test) were randomized separately from those without detectable mutations. The primary endpoint was investigator-assessed progression-free survival (INV-PFS) in patients with PIK3CA-mutant tumors. Secondary endpoints included objective response rate, overall survival, clinical benefit rate, duration of objective response, PFS by blinded independent central review (BICR-PFS), safety, and time to deterioration in health-related quality of life.

RESULTS

The PIK3CA-mutant intention-to-treat population comprised 516 patients (placebo arm: n = 176; taselisib arm: n = 340). INV-PFS was significantly improved in the taselisib {7.4 months [95% confidence interval (CI), 7.26-9.07]} versus placebo arm (5.4 months [95% CI, 3.68-7.29]) (stratified hazard ratio [HR] 0.70; 95% CI, 0.56-0.89; P = 0.0037) and confirmed by BICR-PFS (HR 0.66). Secondary endpoints, including objective response rate, clinical benefit rate, and duration of objective response, showed consistent improvements in the taselisib arm. Safety was assessed in all randomized patients who received at least one dose of taselisib/placebo or fulvestrant regardless of PIK3CA-mutation status (n = 629). Serious adverse events were lower in the placebo versus taselisib arm (8.9% versus 32.0%). There were more discontinuations (placebo arm: 2.3%; taselisib arm: 16.8%) and dose reductions (placebo arm: 2.3%; taselisib arm: 36.5%) in the taselisib arm.

CONCLUSION

SANDPIPER met its primary endpoint; however, the combination of taselisib plus fulvestrant has no clinical utility given its safety profile and modest clinical benefit.

Phase I Basket Study of Taselisib, an Isoform-Selective PI3K Inhibitor, in Patients with PIK3CA-Mutant Cancers

PURPOSE

Somatic mutations in phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), which encodes the p110α catalytic subunit of PI3K, are found in multiple human cancers. While recurrent mutations in PIK3CA helical, regulatory, and kinase domains lead to constitutive PI3K pathway activation, other mutations remain uncharacterized. To further evaluate their clinical actionability, we designed a basket study for patients with PIK3CA-mutant cancers with the isoform-specific PI3K inhibitor taselisib.

PATIENTS AND METHODS

Patients were enrolled on the basis of local PIK3CA mutation testing into one of 11 histology-specific cohorts and treated with taselisib at 6 or 4 mg daily until progression. Tumor DNA from baseline and progression (when available) was sequenced using a next-generation sequencing panel. Exploratory analyses correlating genomic alterations with treatment outcomes were performed.

RESULTS

A total of 166 patients with PIK3CA-mutant cancers were enrolled. The confirmed response rate was 9%. Activity varied by tumor type and mutant allele, with confirmed responses observed in head and neck squamous (15.4%), cervical (10%), and other cancers, plus in tumors containing helical domain mutations. Genomic analyses identified mutations potentially associated with resistance to PI3K inhibition upfront (TP53 and PTEN) and postprogression through reactivation of the PI3K pathway (PTEN, STK11, and PIK3R1). Higher rates of dose modification occurred at higher doses of taselisib, indicating a narrow therapeutic index.

CONCLUSIONS

Taselisib had limited activity in the tumor types tested and is no longer in development. This genome-driven study improves understanding of the activity, limitations, and resistance mechanisms of using PI3K inhibitors as monotherapy to target PIK3CA-mutant tumors.

Functional Precision Medicine Identifies New Therapeutic Candidates for Medulloblastoma

Medulloblastoma is among the most common malignant brain tumors in children. Recent studies have identified at least four subgroups of the disease that differ in terms of molecular characteristics and patient outcomes. Despite this heterogeneity, most patients with medulloblastoma receive similar therapies, including surgery, radiation, and intensive chemotherapy. Although these treatments prolong survival, many patients still die from the disease and survivors suffer severe long-term side effects from therapy. We hypothesize that each patient with medulloblastoma is sensitive to different therapies and that tailoring therapy based on the molecular and cellular characteristics of patients' tumors will improve outcomes. To test this, we assembled a panel of orthotopic patient-derived xenografts (PDX) and subjected them to DNA sequencing, gene expression profiling, and high-throughput drug screening. Analysis of DNA sequencing revealed that most medulloblastomas do not have actionable mutations that point to effective therapies. In contrast, gene expression and drug response data provided valuable information about potential therapies for every tumor. For example, drug screening demonstrated that actinomycin D, which is used for treatment of sarcoma but rarely for medulloblastoma, was active against PDXs representing Group 3 medulloblastoma, the most aggressive form of the disease. Functional analysis of tumor cells was successfully used in a clinical setting to identify more treatment options than sequencing alone. These studies suggest that it should be possible to move away from a one-size-fits-all approach and begin to treat each patient with therapies that are effective against their specific tumor. SIGNIFICANCE: These findings show that high-throughput drug screening identifies therapies for medulloblastoma that cannot be predicted by genomic or transcriptomic analysis.