Concomitant inhibition of PI3K/mTOR signaling pathways boosts antiproliferative effects of lanreotide in bronchopulmonary neuroendocrine tumor cells

Introduction: Somatostatin analogues (SSAs) are commonly used in the treatment of hormone hypersecretion in neuroendocrine tumors (NETs), however the extent to which they inhibit proliferation is much discussed. Objective: We studied the antiproliferative effects of novel SSA lanreotide in bronchopulmonary NETs (BP-NETs). We focused on assessing whether pretreating cells with inhibitors for phosphatidylinositol 3-kinase (PI3K) and mammalian target for rapamycin (mTOR) could enhance the antiproliferative effects of lanreotide. Methods: BP-NET cell lines NCI-H720 and NCI-H727 were treated with PI3K inhibitor BYL719 (alpelisib), mTOR inhibitor everolimus and SSA lanreotide to determine the effect on NET differentiation markers, cell survival, proliferation and alterations in cancer-associated pathways. NT-3 cells, previously reported to express somatostatin receptors (SSTRs) natively, were used as control for SSTR expression. Results: SSTR2 was upregulated in NCI-H720 and NT-3 cells upon treatment with BYL719. Additionally, combination treatment consisting of BYL719 and everolimus plus lanreotide tested in NCI-H720 and NCI-H727 led to diminished cell proliferation in a dose-dependent manner. Production of proteins activating cell death mechanisms was also induced. Notably, a multiplexed gene expression analysis performed on NCI-H720 revealed that BYL719 plus lanreotide had a stronger effect on the downregulation of mitogens than lanreotide alone. Discussion/Conclusion: We report a widespread analysis of changes in BP-NET cell lines at the genetic/protein expression level in response to combination of lanreotide with pretreatment consisting of BYL719 and everolimus. Interestingly, SSTR expression reinduction could be exploited in therapeutic and diagnostic applications. The overall results of this study support the evaluation of combination-based therapies using lanreotide in preclinical studies to further increase its antiproliferative effect and ultimately facilitate its use in high-grade tumors.

Dual inhibition of atypical PKC signaling and PI3K/Akt signaling dysregulates c-Myc to induce apoptosis in clear cell Renal Cell Carcinoma

Background

Renal Cell Carcinoma (RCC) is the most common type of kidney cancer (85%). 75% of the RCC cases involve conventional clear cell RCC (ccRCC). Approximately, 39% of late-stage patients (stage IV) are treated with chemotherapeutic agents. Phosphatidylinositol-3-kinase (PI3K) and Mitogen-Activated Protein Kinase Kinase (MEK)/extracellular signal-regulated kinase (ERK1/2) pathways are frequently activated in RCC. In addition, atypical PKCs (PKC-ί and PKC ζ) are overexpressed in most cancer cells, and they play a central role in tumor progression and the metastasis of different types of cancers. Our goal is to establish the role of aPKCs in the regulation of multiple key activated pathways in ccRCC. In this study, we also established a novel therapeutic regimen for dual inhibition of key activated pathways.

Method

In this study, 786-0 and Caki-1 cells were studied and subjected to cell viability assay, western blot analysis, scratch & wound healing assay, transwell invasion assay, immunofluorescence, immunoprecipitation, flow cytometry, and quantitative real-time polymerase chain reaction. We used combination of PI3K inhibitor- Alpelisib (BYL719) and ICA-1 (a PKC-ι-specific 5-amino-1-2,3-dihydroxy-4-(methylcyclopentyl)-1H-imidazole-4-carboxamide). In addition to drug treatment, small interfering RNA (siRNA) technology was used to further confirm the experimental outcome of the drug treatment.

Results

Our results suggest that treatment of ccRCC cells with a combination of ICA-1 (aPKC inhibitor) and BYL719 (PI3K inhibitor) downregulates PKC-ί and causes downstream inhibition of c-Myc. Inhibition of the PKCί also reduces activation of MEK/ERK1/2. It is observed that treatment with ICA-1 disrupts the level of the aPKC-Akt1 association. ICA-1 treatment also shows a reduced level of association between aPKC and c-Myc. The inhibition of aPKCs and downstream effector proteins by combination therapy is more pronounced compared to a single therapy. These effects contribute to reduced cell growth, and eventually, the induction of apoptosis. The decreased level of N-cadherin, p-vimentin, and vimentin and the increased level of E-cadherin confirm reduced malignancy.

Conclusion

Therefore, implementing a combination of Alpelisib and a PKC-ι inhibitor is an effective approach to reducing cell proliferation, and invasion that eventually induces apoptosis and may be considered as a potential therapeutic option in ccRCC.

Alpelisib: A Novel Agent for PIK3CA-Related Overgrowth Spectrum

The aim of this review is to present the information a clinician will need when considering alpelisib therapy for a patient diagnosed with PIK3CA-related overgrowth spectrum (PROS). PROS is a condition caused by a somatic recessive gain-of-function mutation in the gene encoding phosphatidylinositol-3-kinase (PI3K). PROS is rare, affecting approximately 14 births per 1 million. PROS affects many different tissues including skin, bone, vascular, adipose, and connective tissues, thus its presentations vary widely. The presentation of PROS is often described as mosaic, as the disease typically does not affect all cells in the body. For patients two years of age and older requiring systemic therapy, alpelisib is an option which was recently granted accelerated approval by the US Food and Drug Administration (FDA) on April 5, 2022. Alpelisib is an inhibitor of PI3K, slowing the progression of existing lesions and preventing new lesions in patients with PROS. Important drug interactions exist with both CYP3A4 inducers and CYP2C9 substrates. Additionally, providers of patients receiving alpelisib should be aware of potential side effects including hypersensitivity, severe cutaneous adverse reactions, hyperglycemia, pneumonitis, diarrhea, and embryo-fetal toxicity. Despite the potential for adverse events, alpelisib has provided clinical benefit to many patients with PROS as evidenced by the current literature. This review collects and summarizes the currently available evidence, including a recently published case series and multiple case reports. Alpelisib is a promising new option for patients with PROS.

Pharmacokinetics and Safety of Multiple-Dose Alpelisib in Participants with Moderate or Severe Hepatic Impairment: A Phase 1, Open-Label, Parallel Group Study

The pharmacokinetics (PK) and safety of single-dose alpelisib (300 mg) were assessed in participants with moderate to severe hepatic impairment (n = 6 each) compared with their matching healthy controls (n = 11). Blood samples were collected upto 144 hours post-dose and evaluated by liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay. The primary PK parameters (maximum plasma concentration [C_max], area under the curve [AUC]_inf and AUC_last) and secondary PK parameters (AUC_0-t, apparent total body clearance [CL/F], apparent volume of distribution [Vz/F], time of maximum observed concentration [T_max], and half-life [T_1/2]) of oral alpelisib 300 mg were determined from individual plasma concentration-time profiles using non‑compartmental analysis. C_max of alpelisib decreased by approximately 17% in the moderate hepatic impairment group vs. the healthy control group (geometric mean ratio; GMR [90% confidence interval; CI], 0.833 [0.530, 1.31]). C_max in the severe hepatic impairment group was comparable to that of the healthy control group (GMR [90% CI], 1.00 [0.636, 1.58]). AUC_last for alpelisib decreased by approximately 27% in the moderate hepatic impairment group vs. the healthy control group (GMR [90% CI], 0.726 [0.487, 1.08]). AUC_last was 26% higher in the severe hepatic impairment group compared with the healthy control group (GMR [90% CI], 1.26 [0.845, 1.87]). Overall, 3 participants (13.0%) experienced at least 1 adverse event which were either grade 1 or 2. Adverse events did not lead to study drug discontinuation. No grade 3 or 4 adverse events, serious adverse events or deaths were reported. The results indicate that a single dose of alpelisib was well tolerated in this study population. There was no significant impact of moderate or severe hepatic impairment on the exposure of alpelisib.

Upregulation of PIK3IP1 monitors the anti-cancer activity of PI3Kα inhibitors in gastric cancer cells

Gastric cancer remains one of the most malignant cancers in the world. The target-based drugs approved by FDA for gastric cancer treatment include only three targets and benefit a small portion of gastric cancer patients. PIK3CA, a confirmed oncogene, mutates in 7-25% gastric cancer patients. PI3Kα inhibitor BYL719 has been approved for treating specific breast cancer. However, there is no comprehensive study about PI3Kα inhibitor in gastric cancer. In this study, we found pharmacological inhibition or knockdown of PI3Kα effectively inhibited the proliferation of partial gastric cancer cells. Then, we systematically explored the potential biomarkers for predicting or monitoring treatment response according to previous reports and found that basal expression of several receptor tyrosine kinases were related with the sensitivity of gastric cancer cells to BYL719. Next, RNA-seq technique was utilized and showed that BYL719 inhibited Myc targets V2 gene set in sensitive gastric cancer cells, and western blotting further verified that c-Myc was only inhibited in sensitive gastric cancer cells. More importantly, we firstly found BYL719 significantly elevated the expression of PIK3IP1 in sensitive gastric cancer cells, which was also observed in NCI-N87 cell derived xenograft mice models. Meanwhile, knockdown of PIK3IP1 partially rescued the cell growth inhibited by BYL719 in sensitive gastric cancer cells, suggesting the important role of PIK3IP1 in the antitumor activity of BYL719. In conclusion, our study provides biological evidence that PI3Kα is a promising target in specific gastric cancer and the elevation of PIK3IP1 could supply as a biomarker that monitoring treatment response.

Growth and Viability of Cutaneous Squamous Cell Carcinoma Cell Lines Display Different Sensitivities to Isoform-Specific Phosphoinositide 3-Kinase Inhibitors

Cutaneous squamous cell carcinomas (cSCCs) account for about 20% of keratinocyte carcinomas, the most common cancer in the UK. Therapeutic options for cSCC patients who develop metastasis are limited and a better understanding of the biochemical pathways involved in cSCC development/progression is crucial to identify novel therapeutic targets. Evidence indicates that the phosphoinositide 3-kinases (PI3Ks)/Akt pathway plays an important role, in particular in advanced cSCC. Questions remain of whether all four PI3K isoforms able to activate Akt are involved and whether selective inhibition of specific isoform(s) might represent a more targeted strategy. Here we determined the sensitivity of four patient-derived cSCC cell lines to isoform-specific PI3K inhibitors to start investigating their potential therapeutic value in cSCC. Parallel experiments were performed in immortalized keratinocyte cell lines. We observed that pan PI3Ks inhibition reduced the growth/viability of all tested cell lines, confirming the crucial role of this pathway. Selective inhibition of the PI3K isoform p110α reduced growth/viability of keratinocytes and of two cSCC cell lines while affecting the other two only slightly. Importantly, p110α inhibition reduced Akt phosphorylation in all cSCC cell lines. These data indicate that growth and viability of the investigated cSCC cells display differential sensitivity to isoform-specific PI3K inhibitors.

Effects of PI3K and FGFR inhibitors alone and in combination, and with/without cytostatics in childhood neuroblastoma cell lines

Neuroblastoma (NB) is a heterogenous disease with treatment varying from observation for low-risk tumors, to extensive therapy with chemotherapy, surgery, radiotherapy, and autologous bone-marrow-transplantation and immunotherapy. However, a high frequency of primary-chemo-refractory disease and recurrences urgently require novel treatment strategies. The present study therefore investigated the anti-NB efficacy of the recently FDA-approved phosphoinositide 3-kinase (PI3K) and fibroblast growth factor receptor (FGFR) inhibitors, alpelisib (BYL719) and erdafitinib (JNJ-42756493), alone and in combination with or without cisplatin, vincristine, or doxorubicin on 5 NB cell lines. For this purpose, the NB cell lines, SK-N-AS, SK-N-BE(2)-C, SK-N-DZ, SK-N-FI and SK-N-SH (where SK-N-DZ had a deletion of PIK3C2G and none had FGFR mutations according to the Cancer Program's Dependency Map, although some were chemoresistant), were tested for their sensitivity to FDA-approved inhibitors alone or in combination, or together with cytostatic drugs by viability, cytotoxicity, apoptosis and proliferation assays. The results revealed that monotherapy with alpelisib or erdafitinib resulted in a dose-dependent inhibition of cell viability and proliferation. Notably, the combined use of PI3K and FGFR inhibitors resulted in an enhanced efficacy, while their combined use with the canonical cytotoxic agents, cisplatin, vincristine and doxorubicin, resulted in variable synergistic, additive and antagonistic effects. Collectively, the present study provides pre-clinical evidence that PI3K and FGFR inhibitors exhibit promising anti-NB activity. The data presented herein also indicate that the incorporation of these inhibitors into chemotherapeutic regimens requires careful consideration and further research in order to obtain a beneficial efficacy. Nevertheless, the addition of PI3K and FGFR inhibitors to the treatment arsenal might reduce the occurrence of refractory and relapsing disease in NB without FGFR and PI3K mutations.

TAM family receptors in conjunction with MAPK signalling are involved in acquired resistance to PI3Kα inhibition in head and neck squamous cell carcinoma

Background

Aberrant activation of the phosphatidylinositol 3-kinase (PI3K) pathway is common in many malignancies, including head and neck squamous cell carcinoma (HNSCC). Despite pre-clinical and clinical studies, outcomes from targeting the PI3K pathway have been underwhelming and the development of drug resistance poses a significant barrier to patient treatment. In the present study, we examined mechanisms of acquired resistance to the PI3Kα inhibitor alpelisib (formerly BYL719) in HNSCC cell lines and patient-derived xenografts (PDXs).

Methods

Five unique PDX mouse models and three HNSCC cell lines were used. All cell lines and xenografts underwent genomic characterization prior to study. Serial drug treatment was conducted in vitro and in vivo to develop multiple, clinically-significant models of resistance to alpelisib. We then used reverse phase protein arrays (RPPAs) to profile the expression of proteins in parental and drug-resistant models. Top hits were validated by immunoblotting and immunohistochemistry. Flow cytometric analysis and RNA interference studies were then used to interrogate the molecular mechanisms underlying acquired drug resistance.

Results

Prolonged treatment with alpelisib led to upregulation of TAM family receptor tyrosine kinases TYRO3 and AXL. Importantly, a significant shift in expression of both TYRO3 and AXL to the cell surface was detected in drug-resistant cells. Targeted knockdown of TYRO3 and AXL effectively re-sensitized resistant cells to PI3Kα inhibition. In vivo, resistance to alpelisib emerged following 20–35 days of treatment in all five PDX models. Elevated TYRO3 expression was detected in drug-resistant PDX tissues. Downstream of TYRO3 and AXL, we identified activation of intracellular MAPK signalling. Inhibition of MAPK signalling also re-sensitized drug-resistant cells to alpelisib.

Conclusions

We have identified TYRO3 and AXL receptors to be key mediators of resistance to alpelisib, both in vitro and in vivo. Our findings suggest that pan-TAM inhibition is a promising avenue for combinatorial or second-line therapy alongside PI3Kα inhibition. These findings advance our understanding of the role TAM receptors play in modulating the response of HNSCC to PI3Kα inhibition and suggest a means to prevent, or at least delay, resistance to PI3Kα inhibition in order to improve outcomes for HNSCC patients.

Divergent Roles of PI3K Isoforms in PTEN-Deficient Glioblastomas

Loss of PTEN, the negative regulator of PI3K activity, is frequent in glioblastomas (GBMs). However, the role of the two major PI3K isoforms, p110α and p110β, in PTEN-deficient gliomagenesis remains unknown. We show that PTEN-deficient GBM largely depends on p110α for proliferation and p110β for migration. Genetic ablation of either isoform delays tumor progression in mice, but only ablating both isoforms completely blocks GBM driven by the concurrent ablation of Pten and p53. BKM120 (buparlisib) treatment only modestly prolongs survival in mice bearing intracranial Pten/p53 null tumors due to partial pathway inhibition. BKM120 extends the survival of mice bearing intracranial tumors in which p110β, but not p110α, has been genetically ablated in the Pten/p53 null glioma, indicating that BKM120 fails to inhibit p110β effectively. Our study suggests that the failure of PI3K inhibitors in GBM may be due to insufficient inhibition of p110β and indicates a need to develop brain-penetrant p110α/β inhibitors.

Xie et al. show that p110α and p110β isoforms of PI3K play overlapping and divergent roles in PTEN-deficient glioblastomas, suggesting the importance of blocking both PI3K isoforms to effectively treat PTEN-deficient glioblastomas. Moreover, this study also provides a potential mechanism explaining the failure of BKM120 in the clinic.

Dermatologic adverse events related to the PI3Kα inhibitor alpelisib (BYL719) in patients with breast cancer

PURPOSE

Rash develops in approximately 50% of patients receiving alpelisib for breast cancer, often requiring dose modifications. Here, we describe the clinicopathologic, laboratory, and management characteristics of alpelisib-related dermatologic adverse events (dAEs).

METHODS

A single center-retrospective analysis was conducted. Data were abstracted from electronic medical records.

RESULTS

A total of 102 patients (mean age 56 years, range 27-83) receiving alpelisib most frequently in combination with endocrine therapy (79, 77.5%) were included. We identified 41 (40.2%) patients with all-grade rash distributed primarily along the trunk (78%) and extremities (70%) that developed approximately within two weeks of treatment initiation (mean 12.8 ± 1.5 days) and lasted one-week (mean duration 7.1 ± 0.8 days). Of 29 patients with documented morphology of alpelisib-related dAEs, 26 (89.7%) had maculopapular rash. Histology showed perivascular and interface lymphocytic dermatitis. All-grade rash correlated with an increase in serum eosinophils from 2.7 to 4.4%, p < 0.05, and prophylaxis with non-sedating antihistamines (n = 43) was correlated with a reduction of grade 1/2 rash (OR 0.39, p = 0.09). Sixteen (84.2%) of 19 patients with grade 3 dAEs resulted in interruption of alpelisib, which were managed with antihistamines, topical and systemic corticosteroids. We did not observe rash recurrence in 12 (75%) patients who were re-challenged.

CONCLUSIONS

A maculopapular rash associated with increased blood eosinophils occurs frequently with alpelisib. While grade 3 rash leads to alpelisib therapy interruption, dermatologic improvement is evident with systemic corticosteroids; and most patients can continue oncologic treatment at a maintained or reduced dose upon re-challenge with alpelisib.

Alpelisib Treatment for Genital Vascular Malformation in a Patient with Congenital Lipomatous Overgrowth, Vascular Malformations, Epidermal Nevi, and Spinal/Skeletal Anomalies and/or Scoliosis (CLOVES) Syndrome

BACKGROUND

Most patients with phosphoinositide-3-kinase, catalytic, alpha polypeptide (PIK3CA)-related overgrowth spectrum become symptomatic early in life and need treatment before puberty. Recently, the specific inhibition of PIK3CA pathways has been proposed as a therapeutic option for these patients improving their surgical options and quality of life. Alpelisib, a specific alpha fraction inhibitor, has shown promising results.

CASE

A 17-year-old girl presented with severe involvement of her external genitalia with a combined vascular malformation in the context of congenital, lipomatous, overgrowth, vascular malformations, epidermal nevi and spinal/skeletal anomalies and/or scoliosis syndrome, needing frequent blood transfusions for anemia due to vaginal bleeding and use of a crutch for walking. After failure of treatment with rapamycin, compassionate treatment with alpelisib was started with excellent response.

SUMMARY AND CONCLUSION

PIK3CA inhibitors might become a new option of treatment for PIK3CA-related overgrowth spectrum patients.

Mechanisms of resistance to a PI3K inhibitor in gastrointestinal stromal tumors: an omic approach to identify novel druggable targets

Background: Gastrointestinal stromal tumors (GISTs) represent a worldwide paradigm of target therapy. The introduction of tyrosine kinase inhibitors has deeply changed the prognosis of GIST patients, however, the majority of them acquire secondary mutations and progress. Unfortunately, besides tyrosine-kinase inhibitors, no other therapeutic options are available. Therefore, it is mandatory to identify novel molecules and/or strategies to overcome the inevitable resistance. In this context, after promising preclinical data on the novel PI3K inhibitor BYL719, the NCT01735968 trial in GIST patients who had previously failed treatment with imatinib and sunitinib started. BYL719 has attracted our attention, and we comprehensively characterized genomic and transcriptomic changes taking place during resistance.

Methods: For this purpose, we generated two in vitro GIST models of acquired resistance to BYL719 and performed an omic-based analysis by integrating RNA-sequencing, miRNA, and methylation profiles in sensitive and resistant cells.

Results: We identified novel epigenomic mechanisms of pharmacological resistance in GISTs suggesting the existence of pathways involved in drug resistance and alternatively acquired mutations. Therefore, epigenomics should be taken into account as an alternative adaptive mechanism.

Conclusion: Despite the fact that currently we do not have patients in treatment with BYL719 to verify this hypothesis, the most intriguing result is the involvement of H19 and PSTA1 in GIST resistance, which might represent druggable targets.

Phase I study of alpelisib (BYL719), an α-specific PI3K inhibitor, in Japanese patients with advanced solid tumors

This phase I study aimed to determine tolerability and preliminary efficacy of single‐agent alpelisib (BYL719) in Japanese patients with advanced solid malignancies. The primary objective of the study was to estimate the maximum tolerated dose (MTD) and/or recommended phase II dose (RP2D) of oral alpelisib in patients with advanced solid tumors who had progressed despite standard therapy. The expansion part included patients with PIK3CA mutation/amplification; safety, preliminary efficacy, pharmacokinetic (PK)/pharmacodynamic profile, and food effect on the PK profile of alpelisib at the MTD/RP2D were determined. Oral alpelisib was given as a single agent on a continuous 28‐day treatment cycle once daily. Overall, 33 patients received alpelisib. Dose‐limiting toxicities were observed in 2 patients in the escalation part (at 400 mg/day) and 1 patient in the expansion part (at 350 mg/day). The RP2D of alpelisib was determined as 350 mg/day based on overall safety profile in the dose escalation part and previous data from a Western population; the MTD was not determined. The most common all‐grade treatment‐suspected adverse events were hyperglycemia and maculopapular rash (48.5% each) and diarrhea (45.5%). The PK of alpelisib in the Japanese population was similar to that reported in the Western population. The overall response rate, disease control rate, and median progression‐free survival at 350 mg/day were 3%, 57.6%, and 3.4 months, respectively. Alpelisib as single agent showed a favorable safety profile and encouraging preliminary efficacy in Japanese patients with advanced solid tumors.

Specific inhibition of p110α subunit of PI3K: putative therapeutic strategy for KRAS mutant colorectal cancers

Colorectal cancer (CRC) is a leading cause of cancer mortality worldwide. It is often associated with activating mutations in KRAS leading to deregulation of major signaling pathways as the RAS-RAF-MAPK and PI3K-Akt. However, the therapeutic options for CRC patients harboring somatic KRAS mutations are still very limited. It is therefore urgent to unravel novel therapeutic approaches for those patients. In this study, we have awarded PI3K p110α a key role in CRC cells harboring KRAS/PIK3CA mutations or KRAS mutations alone. Specific silencing of PI3K p110α by small interfering RNA (siRNA) reduced viability and induced apoptosis or cell cycle arrest. In agreement with these cellular effects, PI3K p110α silencing led to alterations in the expression levels of proteins implicated in apoptosis and cell cycle, namely XIAP and pBad in KRAS/PIK3CA mutant cells and cyclin D1 in KRAS mutant cells. To further validate our data, a specific PI3K p110α inhibitor, BYL719, was evaluated. BYL719 mimicked the in vitro siRNA effects on cellular viability and on the alterations of apoptotic- and cell cycle-related proteins in CRC mutant cells. Overall, this study demonstrates that specific inhibition of PI3K p110α could provide an alternative therapeutic approach for CRC patients, particularly those harboring KRAS mutations.

PI3Kδ inhibition causes feedback activation of PI3Kα in the ABC subtype of diffuse large B-cell lymphoma

Cell line models of the activated B cell-like (ABC) subtype of diffuse large B cell (DLBCL) depend on both NF-κB and phosphatidylinositol 3-kinase (PI3K) signaling pathways for survival, especially those with gain-of-function B cell receptor (BCR) mutations. Here we show that these cells depend specifically on the PI3Kδ isoform, but that PI3K pathway interruption by PI3Kδ inhibitors is short-lived due to feedback activation of the PI3Kα isoform. PI3Kδ and PI3Kα inhibition cooperated in killing ABC DLBCL lines, and genetic knockdown of PI3Kα sensitized cells to PI3Kδ inhibition and prolonged the interruption of PI3K signaling. PI3Kδ inhibition evoked feedback activation of proximal BCR signaling, which increased the association of PI3Kα with BCAP and CD19 and increased overall PI3K activity. These results support the clinical evaluation of dual PI3Kδ and PI3Kα inhibition in patients with ABC DLBCL.

Integration of Receptor Tyrosine Kinases Determines Sensitivity to PI3Kα-selective Inhibitors in Breast Cancer

PI3Kα-selective inhibitor BYL719 is currently in phase II/III clinical trial for the treatment of breast cancer, but highly variable response has been observed among patients. We sought to discover predictive biomarker for the efficacy of BYL719 by dissecting the proliferative signaling pathway mediated by PI3K in breast cancer. BYL719 concurrently inhibited the phosphorylation of AKT and ERK in PIK3CA-mutated human breast cancer cells. PI3K-regulated ERK phosphorylation was independent of canonical PDK1/AKT/mTOR pathway, while it was associated with RAF/MEK. Hyper-activation of EGFR or RAS abrogated inhibition of ERK phosphorylation by BYL719. Furthermore, hyper-activation of receptor tyrosine kinases (RTKs) including EGFR, c-MET, FGFR and HER3 but not IGF-1R restored ERK phosphorylation and cell viability suppressed by BYL719, suggesting the discriminative functions of RTKs in cell signaling and proliferation. By profiling 22 breast cancer cell lines, we found that BYL719 was more potent in cell lines where phosphorylation of both AKT and ERK was attenuated than those where only AKT phosphorylation was inhibited. The potency of BYL719 was further found to be significantly correlated with the expression profile of RTKs in breast cancer cells. Specifically, overexpression of EGFR, c-MET and/or FGFR1 forecasted resistance, while overexpression of IGF-1R and/or HER2 predicted sensitivity to BYL719 in breast cancer cells. Similar correlation between BYL719 efficacy and expression profile of RTKs was found in patient-derived xenograft models of breast cancer. Thus, inhibition of ERK phosphorylation by PI3Kα inhibitor BYL719 contributes to its antitumor efficacy and is determined by the converged signaling from RTKs. The expression profile of RTKs in breast cancer tissue could be potentially developed as a predictive biomarker for the efficacy of PI3Kα inhibitors.

Population pharmacokinetics and pharmacodynamics of BYL719, a phosphoinositide 3-kinase antagonist, in adult patients with advanced solid malignancies

AIMS

The aim was to characterize the population pharmacokinetics of BYL719 in cancer patients and assess the time course of tumour response in relation to drug exposure and dosing schedule.

METHODS

Plasma samples and longitudinal tumour size measurements were collected from 60 patients with advanced solid malignancies who received oral BYL719 once daily (30-450 mg) or twice daily at 120 mg or 200 mg. Non-linear mixed effect modelling was employed to develop the population pharmacokinetic and pharmacodynamic model.

RESULTS

The pharmacokinetics were best described by a one compartment disposition model and transit compartments accounting for the lag time in absorption. The typical population oral clearance and volume of distribution estimates with their between-subject variability (BSV) were 10 l h(-1) (BSV 26%) and 108 l (BSV 28%), respectively. The estimated optimal number of transit compartments was 8.1, with a mean transit time to the absorption compartment of 1.28 h (BSV 32%). The between-occasion variability in the rate and extent of absorption was 46% and 26%, respectively. Tumour growth was modelled using a turnover model characterized by a zero order growth rate of 0.581 cm week(1) and a first order death rate of 0.0123 week(-1) . BYL719 inhibited tumour growth with an IC50 of 100 ng ml(-1) (BSV 154%). Model-based predictions showed potential for additional anti-tumour activity of twice daily dosing at total daily dose below 400 mg, but a loss of efficacy if administered less frequently than once daily.

CONCLUSIONS

The proposed model provides a valuable approach for planning future clinical studies and for designing optimized dosing regimens with BYL719.

In vitro anticancer activity of PI3K alpha selective inhibitor BYL719 in head and neck cancer

BACKGROUND/AIM

The purpose of the present study was to explore the antiproliferative effect of BYL719, a specific inhibitor for phosphatidylinositol 3-kinase (PI3K) p110α, in human head and neck cancer cell lines, as a single agent or in combination with the irreversible EGFR tyrosine kinase inhibitor, dacomitinib.

MATERIALS AND METHODS

Six head and neck cancer cell lines consisting of two PIK3CA mutant cell lines, SNU-1076 and Detroit562, and four PIK3CA wild-type cell lines, SNU-1066, SNU-1041, FaDu and SCC25, were analyzed.

RESULTS

The PIK3CA-mutant cell lines were more sensitive to BYL719 than the PIK3CA wild-type cell lines. Following BYL719 treatment, all PIK3CA wild-type cell lines, except for the SNU-1066 cell line, exhibited higher IC50 values compared to the PIK3CA mutant cell lines. Administration of BYL719 induced cell cycle G0/G1 arrest and resulted in increased apoptosis in a dose-dependant manner. Furthermore, the administration of BYL719 reduced the level of p-mTOR, p-AKT and p-S6 expression indicating the down-regulation of downstream signaling.

CONCLUSION

BYL719, a PI3K alpha selective blocker, could be a promising factor in the treatment of head and neck cancer either as a single agent or in combination with dacomitinib.