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.

Learnings from phosphatidylinositol 3-kinase inhibitors in lymphoma-Moving to a model where less can be more.

The role of Pi3K inhibitors in lymphoma is diminishing due to the adverse results from trials in indolent lymphoma, but is a one-size-fits-all approach to drug development penalising some lymphoma subtypes and the newer generation of Pi3K inhibitors? The report by Soumerai et al. of zandelisib with zanubrutinib in follicular and mantle cell lymphoma is an important addition to the data. Commentary on: Soumerai et al. Safety and efficacy of zandelisib plus zanubrutinib in previously treated follicular and mantle cell lymphomas. Br J Haematol 2024;204:1762-1770.

Targeting PI3K-gamma in myeloid driven tumour immune suppression: a systematic review and meta-analysis of the preclinical literature.

The intricate interplay between immune and stromal cells within the tumour microenvironment (TME) significantly influences tumour progression. Myeloid cells, including tumour-associated macrophages (TAMs), neutrophils (TANs), and myeloid-derived suppressor cells (MDSCs), contribute to immune suppression in the TME (Nakamura and Smyth in Cell Mol Immunol 17(1):1-12 (2020). https://doi.org/10.1038/s41423-019-0306-1 ; DeNardo and Ruffell in Nat Rev Immunol 19(6):369-382 (2019). https://doi.org/10.1038/s41577-019-0127-6 ). This poses a significant challenge for novel immunotherapeutics that rely on host immunity to exert their effect. This systematic review explores the preclinical evidence surrounding the inhibition of phosphoinositide 3-kinase gamma (PI3Kγ) as a strategy to reverse myeloid-driven immune suppression in solid tumours. EMBASE, MEDLINE, and PubMed databases were searched on 6 October 2022 using keyword and subject heading terms to capture relevant studies. The studies, focusing on PI3Kγ inhibition in animal models, were subjected to predefined inclusion and exclusion criteria. Extracted data included tumour growth kinetics, survival endpoints, and immunological responses which were meta-analysed. PRISMA and MOOSE guidelines were followed. A total of 36 studies covering 73 animal models were included in the review and meta-analysis. Tumour models covered breast, colorectal, lung, skin, pancreas, brain, liver, prostate, head and neck, soft tissue, gastric, and oral cancer. The predominant PI3Kγ inhibitors were IPI-549 and TG100-115, demonstrating favourable specificity for the gamma isoform. Combination therapies, often involving chemotherapy, radiotherapy, immune checkpoint inhibitors, biological agents, or vaccines, were explored in 81% of studies. Analysis of tumour growth kinetics revealed a statistically significant though heterogeneous response to PI3Kγ monotherapy, whereas the tumour growth in combination treated groups were more consistently reduced. Survival analysis showed a pronounced increase in median overall survival with combination therapy. This systematic review provides a comprehensive analysis of preclinical studies investigating PI3Kγ inhibition in myeloid-driven tumour immune suppression. The identified studies underscore the potential of PI3Kγ inhibition in reshaping the TME by modulating myeloid cell functions. The combination of PI3Kγ inhibition with other therapeutic modalities demonstrated enhanced antitumour effects, suggesting a synergistic approach to overcome immune suppression. These findings support the potential of PI3Kγ-targeted therapies, particularly in combination regimens, as a promising avenue for future clinical exploration in diverse solid tumour types.

Real-world treatment patterns and clinical outcomes in patients treated with eribulin after prior phosphoinositide 3-Kinase inhibitor treatment for metastatic breast cancer.

PURPOSE: In 2010, the US Food and Drug Administration approved eribulin for the treatment of metastatic breast cancer (MBC). Since then, the treatment landscape has evolved with many new therapy classes, a more recent one being the small molecule inhibitors of phosphoinositide 3 kinase (PI3K). We sought to characterize the treatment patterns and clinical outcomes of patients with MBC who received eribulin following prior treatment with a PI3K inhibitor. METHODS: A retrospective cohort study based on medical record review included MBC patients who initiated eribulin between March 2019 and September 2020 following prior treatment with a PI3K inhibitor was conducted. Patient demographics, treatment characteristics, and clinical outcomes were analyzed descriptively. Real-world progression-free survival (rwPFS) and overall survival (OS) were estimated from the initiation of eribulin therapy using Kaplan-Meier analyses. RESULTS: 82 eligible patients were included. Patients' median age at eribulin initiation was 62 years; 86.5% had hormone receptor-positive, human epidermal growth factor receptor 2-negative tumors. Eribulin was most often administered in the second or third line (82.9%) in the metastatic setting. Best overall response on eribulin was reported as complete or partial response in 72% of the patients. The median rwPFS was 18.9 months (95% confidence interval [CI], 12.4-not estimable); median OS was not reached. The estimated rwPFS and OS rates at 12 months were 63.3% (95% CI, 50.5-73.7) and 82.6% (95% CI, 72.4-89.3), respectively. CONCLUSION: Our real-world study suggests that eribulin may be a potential treatment option for MBC patients who fail a prior PI3K inhibitor.

Disparities in PI3K/mTOR inhibitor use, toxicities, and outcomes among patients with metastatic breast cancer.

PURPOSE: Novel agents such as PI3K and mTOR inhibitors (PI3K/mTORi) have expanded treatment options in metastatic breast cancer (MBC). Nevertheless, mortality rates remain disproportionately high for Black patients and patients with lower socioeconomic status. Furthermore, clinical trials for these novel agents lacked diversity, so their toxicity profile in minority populations is uncertain. METHODS: We conducted a retrospective analysis of EHR-derived data from the Flatiron Health Database for patients with HR+, HER2- MBC. Multivariable logistic regression was used to evaluate factors associated with PI3K/mTORi use and toxicity outcomes. RESULTS: A total of 9169 patients with MBC were included in our analysis, of which 1780 (19.4%) received a PI3K/mTORi. We estimated the conditional total effect of insurance through Medicaid, and found lower odds of use of PI3K/mTORi among patients on Medicaid compared to those with commercial insurance (OR 0.73, 95% CI 0.54-0.99, p = 0.049). Odds of PI3K/mTORi use were higher for patients treated at an academic center (OR 1.28, CI 1.06-1.55, p = 0.01). Modeled as a controlled direct effect, Black/African American (Black/AA) race had no impact on odds of PI3K/mTOR use. Black/AA patients had twice the odds of developing hyperglycemia on PI3K/mTORi compared to White patients (OR 2.02, CI 1.24-3.39, p < 0.01). CONCLUSION: This analysis of real-world data suggests that the use of PI3K/mTORi is influenced by socioeconomic factors. We also found racial disparities in toxicity outcomes, with Black/AA patients having twice the risk of hyperglycemia. Our findings call for greater efforts to ensure access to novel treatments and improve their tolerability in diverse populations.

Predictive, preventive, and personalized medicine in breast cancer: targeting the PI3K pathway.

Breast cancer (BC) is a multifaceted disease characterized by distinct molecular subtypes and varying responses to treatment. In BC, the phosphatidylinositol 3-kinase (PI3K) pathway has emerged as a crucial contributor to the development, advancement, and resistance to treatment. This review article explores the implications of the PI3K pathway in predictive, preventive, and personalized medicine for BC. It emphasizes the identification of predictive biomarkers, such as PIK3CA mutations, and the utility of molecular profiling in guiding treatment decisions. The review also discusses the potential of targeting the PI3K pathway for preventive strategies and the customization of therapy based on tumor stage, molecular subtypes, and genetic alterations. Overcoming resistance to PI3K inhibitors and exploring combination therapies are addressed as important considerations. While this field holds promise in improving patient outcomes, further research and clinical trials are needed to validate these approaches and translate them into clinical practice.

PI3Kγδ inhibition suppresses key disease features in a rat model of asthma.

BACKGROUND: Two isoforms of Phosphoinositide 3-kinase (PI3K), p110γ and p110δ, are predominantly expressed in leukocytes and represent attractive therapeutic targets for the treatment of allergic asthma. The study aim was to assess the impact of administration of an inhaled PI3Kγδ inhibitor (AZD8154) in a rat model of asthma. METHODS: Firstly, we checked that the tool compound, AZD8154, inhibited rat PI3K γ & δ kinases using rat cell-based assays. Subsequently, a time-course study was conducted in a rat model of asthma to assess PI3K activity in the lung and how it is temporally associated with other key transcription pathways and asthma like features of the model. Finally, the impact on lung dosed AZD8154 on target engagement, pathway specificity, airway inflammation and lung function changes was assessed. RESULTS: Data showed that AZD8154 could inhibit rat PI3K γ & δ isoforms and, in a rat model of allergic asthma the PI3K pathway was activated in the lung. Intratracheal administration of AZD8154 caused a dose related suppression PI3K pathway activation (reduction in pAkt) and unlike after budesonide treatment, STAT and NF-κB pathways were not affected by AZD8154. The suppression of the PI3K pathway led to a marked inhibition of airway inflammation and reduction in changes in lung function. CONCLUSION: These data show that a dual PI3Kγδ inhibitor suppress key features of disease in a rat model of asthma to a similar degree as budesonide and indicate that dual PI3Kγδ inhibition may be an effective treatment for people suffering from allergic asthma.

Alpelisib for PIK3CA-mutated advanced gynecological cancers: First clues of clinical activity.

OBJECTIVE: Recurrent gynecological tumors (e.g., endometrial, and ovarian cancers) are incurable diseases; therefore, new treatment options are urgently needed. The PTEN-AKT-PI3K pathway is frequently altered in these tumors, representing a potential treatment target. Alpelisib is an α-specific PI3K inhibitor approved in PIK3CA-mutated advanced breast cancer. We report outcomes from a large series of patients with PIK3CA-mutated gynecological cancers prospectively treated with alpelisib within a controlled program. METHODS: From April 2021 to December 2022, 36 patients with PIK3CA-mutated advanced gynecological cancers received alpelisib 300 mg orally once daily. Objective response (ORR) and disease control (DCR) rates provided measure of the antitumor activity of alpelisib, the primary objective of the study. RESULTS: Included patients had endometrial (17/36 [47%]), ovarian (10/36 [28%]), or other gynecological cancers (9/36 [25%]). Most patients had received 2-3 prior systemic treatments (endometrial, 47·2%; ovarian, 60%; other, 56%), and presented with visceral metastases at baseline (82%, 70%, and 56%, respectively). Overall, 17 different PIK3CA mutations were found, including 53% in the kinase domain (most commonly H1047R) and 36% in the helical domain (most commonly E545K). Overall, the ORR was 28% and DCR was 61%, with the greatest benefit observed in patients with endometrial cancer (35% and 71%, respectively). CONCLUSION: Alpelisib represents an active treatment option in patients with recurrent gynecological cancers harboring a PIK3CA mutation. These findings support the need of biomarker-driven randomized trials of PI3K inhibitors in gynecological cancers.

Aggressive T-cell lymphomas: 2024: Updates on diagnosis, risk stratification, and management.

INTRODUCTION: Aggressive T-cell lymphomas continue to have a poor prognosis. There are over 30 different subtypes of peripheral T-cell lymphoma (PTCL), and we are now beginning to understand the differences between the various subtypes beyond histologic variations. MOLECULAR PATHOGENESIS OF VARIOUS SUBTYPES OF PTCL: Gene expression profiling and other molecular techniques have enabled deeper understanding of differences in various subtypes as reflected in the latest 5th WHO classification of PTCL. It is becoming increasingly clear that therapeutic approaches that target specific cellular pathways are needed to improve the clinical outcomes of PTCL. TARGETED THERAPIES: There are many targeted agents currently in various stages of clinical trials for PTCL that take advantage of the differential expression of specific proteins or receptors in PTCL tumors. This includes the CD30 directed antibody drug conjugate brentuximab vedotin. Other notable targets are phosphatidylinositol 3-kinase inhibitors, histone deacetylase inhibitors, CD25, and chemokine receptor 4. Anaplastic lymphoma kinase (ALK) inhibitors are promising for ALK expressing tumors. IMMUNOTHERAPIES: Allogeneic stem cell transplant continues to be the curative therapy for most aggressive subtypes of PTCL. The use of checkpoint inhibitors in the treatment of PTCL is still controversial, with best results seen in cases of extranodal natural killer cell/T-cell lymphoma. Bispecific antibody-based treatments and chimeric antigen receptor cell-based therapies are in clinical trials.

Quantitative evaluation of the efficacy and safety profiles of two types of targeted inhibitors combined with endocrine therapy in ER+/HER2- metastatic breast cancer.

PURPOSE: The aim of this study was to quantitatively compare the efficacy and safety of CDK4/6 inhibitors and PI3K/AKT/mTOR inhibitors for ER+/HER2- metastatic breast cancer. METHODS: A parametric survival function was used to analyze the time course of overall survival (OS) and progression-free survival (PFS). The objective response rate (ORR) and the incidence of any grade and grade 3-4 adverse events were summarized using the random-effects model of a single-arm meta-analysis. RESULTS: This study included 44 arms from 48 publications, with a total sample size of 7881 patients. Our study revealed that CDK4/6 inhibitors had a median OS of 40.7 months, a median PFS of 14.8 months, and an ORR of 40%, whereas PI3K/AKT/mTOR inhibitors had a median OS of 29.8 months, a median PFS of 8.3 months, and an ORR of 20%. Additionally, this study also found that the proportion of patients with visceral metastases and specific endocrine therapy used in combination significantly impact OS and PFS. In terms of adverse events, CDK4/6 inhibitors exhibited a relatively high incidence of hematological adverse events. CONCLUSION: Our study provides solid quantitative evidence for the first-line recommendation of CDK4/6 inhibitors combined with endocrine therapy for ER+/HER2- metastatic breast cancer in clinical guidelines.

Dose optimization for cancer treatments with considerations for late-onset toxicities.

Given that novel anticancer therapies have different toxicity profiles and mechanisms of action, it is important to reconsider the current approaches for dose selection. In an effort to move away from considering the maximum tolerated dose as the optimal dose, the Food and Drug Administration Project Optimus points to the need of incorporating long-term toxicity evaluation, given that many of these novel agents lead to late-onset or cumulative toxicities and there are no guidelines on how to handle them. Numerous methods have been proposed to handle late-onset toxicities in dose-finding clinical trials. A summary and comparison of these methods are provided. Moreover, using PI3K inhibitors as a case study, we show how late-onset toxicity can be integrated into the dose-optimization strategy using current available approaches. We illustrate a re-design of this trial to compare the approach to those that only consider early toxicity outcomes and disregard late-onset toxicities. We also provide proposals going forward for dose optimization in early development of novel anticancer agents with considerations for late-onset toxicities.

The PI3K/AKT/mTOR signaling pathway in breast cancer: Review of clinical trials and latest advances.

Breast cancer (BC) is the most commonly diagnosed cancer and the leading cause of cancer mortality in women. As the phosphatidylinositol 3-kinase (PI3K) signaling pathway is involved in a wide range of physiological functions of cells including growth, proliferation, motility, and angiogenesis, any alteration in this axis could induce oncogenic features; therefore, numerous preclinical and clinical studies assessed agents able to inhibit the components of this pathway in BC patients. To the best of our knowledge, this is the first study that analyzed all the registered clinical trials investigating safety and efficacy of the PI3K/AKT/mTOR axis inhibitors in BC. Of note, we found that the trends of PI3K inhibitors in recent years were superior as compared with the inhibitors of either AKT or mTOR. However, most of the trials entering phase III and IV used mTOR inhibitors (majorly Everolimus) followed by PI3K inhibitors (majorly Alpelisib) leading to the FDA approval of these drugs in the BC context. Despite favorable efficacies, our analysis shows that the majority of trials are utilizing PI3K pathway inhibitors in combination with hormone therapy and chemotherapy; implying monotherapy cannot yield huge clinical benefits, at least partly, due to the activation of compensatory mechanisms. To emphasize the beneficial effects of these inhibitors in combined-modal strategies, we also reviewed recent studies which investigated the conjugation of nanocarriers with PI3K inhibitors to reduce harmful toxicities, increase the local concentration, and improve their efficacies in the context of BC therapy.

Molecular Targeting of the Phosphoinositide-3-Protein Kinase (PI3K) Pathway across Various Cancers.

The dysregulation of the phosphatidylinositol-3-kinase (PI3K) pathway can lead to uncontrolled cellular growth and tumorigenesis. Targeting PI3K and its downstream substrates has been shown to be effective in preclinical studies and phase III trials with the approval of several PI3K pathway inhibitors by the Food and Drug Administration (FDA) over the past decade. However, the limited clinical efficacy of these inhibitors, intolerable toxicities, and acquired resistances limit the clinical application of PI3K inhibitors. This review discusses the PI3K signaling pathway, alterations in the PI3K pathway causing carcinogenesis, current and novel PI3K pathway inhibitors, adverse effects, resistance mechanisms, challenging issues, and future directions of PI3K pathway inhibitors.

EGFR and PI3K Signalling Pathways as Promising Targets on Circulating Tumour Cells from Patients with Metastatic Gastric Adenocarcinoma.

The prognosis for metastatic gastric adenocarcinoma (mGAC) remains poor. Gene alterations in receptor tyrosine kinases (RTKs) such as epidermal growth factor receptor (EGFR) and their downstream effectors including catalytic subunit alpha of the phosphatidylinositol 3-kinase (PIK3CA) are common in mGAC. Targeted RTK and phosphatidylinositol-3-kinase (PI3K) treatments have demonstrated clinical benefits in other solid tumours and are key potential targets for clinical development against mGAC given the presence of recurrent alterations in these pathways. Furthermore, combination RTK/PI3K treatments may overcome compensatory mechanisms that arise using monotherapies, leading to improved patient outcomes. Herein, we investigated RTK/PI3K single and combination drug responses against our unique human mGAC-derived PIK3CA gain-of-function mutant, human epidermal growth factor receptor 2 (HER2)-negative, EGFR-expressing circulating tumour cell line, UWG02CTC, under two- and three-dimensional culture conditions to model different stages of metastasis. UWG02CTCs were highly responsive to the PI3K p110α-subunit targeted drugs PIK-75 (IC50 = 37.0 ± 11.1 nM) or alpelisib (7.05 ± 3.7 µM). Drug sensitivities were significantly increased in 3D conditions. Compensatory MAPK/ERK pathway upregulation by PI3K/Akt suppression was overcome by combination treatment with the EGFR inhibitor gefitinib, which was strongly synergistic. PIK-75 plus gefitinib significantly impaired UWG02CTC invasion in an organotypic assay. In conclusion, UWG02CTCs are a powerful ex vivo mGAC drug responsiveness model revealing EGFR/PI3K-targeted drugs as a promising combination treatment option for HER2-negative, RAS wild-type mGAC patients.

Discovery of Pyridopyrimidinones that Selectively Inhibit the H1047R PI3Kα Mutant Protein.

The H1047R mutation of PIK3CA is highly prevalent in breast cancers and other solid tumors. Selectively targeting PI3KαH1047R over PI3KαWT is crucial due to the role that PI3KαWT plays in normal cellular processes, including glucose homeostasis. Currently, only one PI3KαH1047R-selective inhibitor has progressed into clinical trials, while three pan mutant (H1047R, H1047L, H1047Y, E542K, and E545K) selective PI3Kα inhibitors have also reached the clinical stage. Herein, we report the design and discovery of a series of pyridopyrimidinones that inhibit PI3KαH1047R with high selectivity over PI3KαWT, resulting in the discovery of compound 17. When dosed in the HCC1954 tumor model in mice, 17 provided tumor regressions and a clear pharmacodynamic response. X-ray cocrystal structures from several PI3Kα inhibitors were obtained, revealing three distinct binding modes within PI3KαH1047R including a previously reported cryptic pocket in the C-terminus of the kinase domain wherein we observe a ligand-induced interaction with Arg1047.

Phase II study of novel orally PI3Kα/δ inhibitor TQ-B3525 in relapsed and/or refractory follicular lymphoma.

This registration study assessed clinical outcomes of TQ-B3525, the dual phosphatidylinositol-3-kinase (PI3K) α/δ inhibitor, in relapsed and/or refractory follicular lymphoma (R/R FL). This phase II study (ClinicalTrials.gov NCT04324879. Registered March 27, 2020) comprised run-in stage and stage 2. R/R FL patients after ≥2 lines therapies received oral 20 mg TQ-B3525 once daily in a 28-day cycle until intolerable toxicity or disease progression. Primary endpoint was independent review committee (IRC)-assessed objective response rate (ORR). Based on results (ORR, 88.0%; duration of response [DOR], 11.8 months; progression-free survival [PFS], 12.0 months) in 25 patients at run-in stage, second stage study was initiated and included 82 patients for efficacy/safety analysis. Patients received prior-line (median, 3) therapies, with 56.1% refractory to previous last therapies; 73.2% experienced POD24 at baseline. At stage 2, ORR was 86.6% (71/82; 95% CI, 77.3-93.1%), with 28 (34.2%) complete responses. Disease control rate was 95.1% due to 7 (8.5%) stable diseases. Median time to response was 1.8 months. Among 71 responders, median DOR was not reached; 18-month DOR rate was 51.6%. with median follow-up of 13.3 months, median PFS was 18.5 (95% CI, 10.2-not estimable) months. Median overall survival (OS) was not reached by cutoff date; 24-month OS rate was estimated as 86.1%. Response rates and survival data were consistent across all subgroups. Grade 3 or higher treatment-related adverse events were observed in 63 (76.8%) cases, with neutropenia (22.0%), hyperglycemia (19.5%), and diarrhea (13.4%) being common. TQ-B3525 showed favorable efficacy and safety for R/R FL patients after ≥2 lines prior therapies.

The dual HDAC and PI3K inhibitor, CUDC­907, inhibits tumor growth and stem­like properties by suppressing PTX3 in neuroblastoma.

Neuroblastoma (NB) is one of the common solid tumors in childhood and poses a threat to the lives of children. Patients with advanced­stage or recurrent NB have a poor prognosis. CUDC­907, as a novel dual­target inhibitor of histone deacetylase (HDAC) and phosphatidylinositol­3­kinase (PI3K), has been proven to play an antitumor role in several types of tumors. However, the exact role of CUDC­907 in NB remains unclear. In the present study, in vivo and in vitro assays were performed to investigate the anti­NB activity of CUDC­907. Pentraxin 3 (PTX3) small interfering RNA (siRNA) and PTX3 overexpression plasmid were transfected into cells to define the underlying mechanisms of CUDC­907. Tumor tissues and clinical information were collected and immunohistochemistry (IHC) was conducted to analyze the association between the expression of HDAC1, HDAC2, HDAC3 and CD44, and the prognosis of patients with NB. The results indicated that CUDC­907 significantly inhibited the proliferation and migration, and induced the apoptosis of NB cells, downregulating the expression level of MYCN, and suppressing the PI3K/AKT and MAPK/ERK pathways. Furthermore, CUDC­907 suppressed the stem­like properties of NB cells by inhibiting PTX3, a ligand and upstream protein of CD44. IHC revealed that the high expression of HDAC1, 2, 3 and CD44 was associated with a poor prognosis of patients with NB. On the whole, these findings indicate that CUDC­907 may be developed into a possible therapeutic approach for patients with NB.

Long-term treatment with selective PI3Kδ inhibitor leniolisib in adults with activated PI3Kδ syndrome.

ABSTRACT: Activated phosphoinositide 3-kinase delta (PI3Kδ) syndrome (APDS) is an inborn error of immunity that manifests as immune deficiency and dysregulation; symptoms include frequent infections and lymphoproliferation. In our dose-finding and phase 3 placebo-controlled trials, treatment with the selective PI3Kδ inhibitor leniolisib reduced lymphoproliferation and normalized lymphocyte subsets. Here, we present 6 years of follow-up from the 6 adult patients in the original dose-finding trial receiving leniolisib. We used data from the ongoing open-label extension study, which was supplemented at later time points by investigators, including health-related quality of life (HRQoL) assessed through a clinician-reported questionnaire. We observed improvements in HRQoL: 5 of 6 patients experienced an increase in physical capabilities and socialization, and a decrease in prescribed medications. Immune subsets improved in all patients: mean transitional B-cell levels decreased from 38.17% to 2.47% and the CD4:CD8 T-cell ratio normalized to 1.11. Manifestations seen before and within the first year of leniolisib exposure, such as infections and gastrointestinal conditions, attenuated after year 2, with few new conditions emerging out to year 6. Thrombocytopenia or lymphopenia remained present in half of patients at year 6. Of 83 adverse events through year 5, 90.36% were grade 1; none were grade 4/5 nor deemed leniolisib related. Collectively, we saw an enhancement in HRQoL as well as durable changes in lymphocyte subsets and clinical manifestations, further supporting the use of leniolisib as a long-term therapeutic option for the treatment of APDS. This trial was registered at www.ClinicalTrials.gov as #NCT02859727.

Selective Termination of Autophagy-Dependent Cancers.

The goal of cancer research is to identify characteristics of cancer cells that allow them to be selectively eliminated without harming the host. One such characteristic is autophagy dependence. Cancer cells survive, proliferate, and metastasize under conditions where normal cells do not. Thus, the requirement in cancer cells for more energy and macromolecular biosynthesis can evolve into a dependence on autophagy for recycling cellular components. Recent studies have revealed that autophagy, as well as different forms of cellular trafficking, is regulated by five phosphoinositides associated with eukaryotic cellular membranes and that the enzymes that synthesize them are prime targets for cancer therapy. For example, PIKFYVE inhibitors rapidly disrupt lysosome homeostasis and suppress proliferation in all cells. However, these inhibitors selectively terminate PIKFYVE-dependent cancer cells and cancer stem cells with not having adverse effect on normal cells. Here, we describe the biochemical distinctions between PIKFYVE-sensitive and -insensitive cells, categorize PIKFYVE inhibitors into four groups that differ in chemical structure, target specificity and efficacy on cancer cells and normal cells, identify the mechanisms by which they selectively terminate autophagy-dependent cancer cells, note their paradoxical effects in cancer immunotherapy, and describe their therapeutic applications against cancers.