Buparlisib plus fulvestrant versus placebo plus fulvestrant in postmenopausal, hormone receptor-positive, HER2-negative, advanced breast cancer (BELLE-2): a randomised, double-blind, placebo-controlled, phase 3 trial.

BACKGROUND: Phosphatidylinositol 3-kinase (PI3K) pathway activation is a hallmark of endocrine therapy-resistant, hormone receptor-positive breast cancer. This phase 3 study assessed the efficacy of the pan-PI3K inhibitor buparlisib plus fulvestrant in patients with advanced breast cancer, including an evaluation of the PI3K pathway activation status as a biomarker for clinical benefit. METHODS: The BELLE-2 trial was a randomised, double-blind, placebo-controlled, multicentre study. Postmenopausal women aged 18 years or older with histologically confirmed, hormone receptor-positive and human epidermal growth factor (HER2)-negative inoperable locally advanced or metastatic breast cancer whose disease had progressed on or after aromatase inhibitor treatment and had received up to one previous line of chemotherapy for advanced disease were included. Eligible patients were randomly assigned (1:1) using interactive voice response technology (block size of 6) on day 15 of cycle 1 to receive oral buparlisib (100 mg/day) or matching placebo, starting on day 15 of cycle 1, plus intramuscular fulvestrant (500 mg) on days 1 and 15 of cycle 1, and on day 1 of subsequent 28-day cycles. Patients were assigned randomisation numbers with a validated interactive response technology; these numbers were linked to different treatment groups which in turn were linked to treatment numbers. PI3K status in tumour tissue was determined via central laboratory during a 14-day run-in phase. Randomisation was stratified by PI3K pathway activation status (activated vs non-activated vs and unknown) and visceral disease status (present vs absent). Patients, investigators, local radiologists, study team, and anyone involved in the study were masked to the identity of the treatment until unblinding. The primary endpoints were progression-free survival by local investigator assessment per Response Evaluation Criteria In Solid Tumors (version 1.1) in the total population, in patients with known (activated or non-activated) PI3K pathway status, and in PI3K pathway-activated patients. Efficacy analyses were done in the intention-to-treat population. Safety was analysed in all patients who received at least one dose of study drug and had at least one post-baseline safety assessment according to the treatment they received. This trial is registered with ClinicalTrials.gov, number NCT01610284, and is currently ongoing but not recruiting participants. FINDINGS: Between Sept 7, 2012, and Sept 10, 2014, 1147 patients from 267 centres in 29 countries were randomly assigned to receive buparlisib (n=576) or placebo plus fulvestrant (n=571). In the total patient population (n=1147), median progression-free survival was 6·9 months (95% CI 6·8-7·8) in the buparlisib group versus 5·0 months (4·0-5·2) in the placebo group (hazard ratio [HR] 0·78 [95% CI 0·67-0·89]; one-sided p=0·00021). In patients with known PI3K status (n=851), median progression-free survival was 6·8 months (95% CI 5·0-7·0) in the buparlisib group vs 4·5 months (3·3-5·0) in the placebo group (HR 0·80 [95% CI 0·68-0·94]; one-sided p=0·0033). In PI3K pathway-activated patients (n=372), median progression-free survival was 6·8 months (95% CI 4·9-7·1) in the buparlisib group versus 4·0 months (3·1-5·2) in the placebo group (HR 0·76 [0·60-0·97], one-sided p=0·014). The most common grade 3-4 adverse events in the buparlisib group versus the placebo group were increased alanine aminotransferase (146 [25%] of 573 patients vs six [1%] of 570), increased aspartate aminotransferase (103 [18%] vs 16 [3%]), hyperglycaemia (88 [15%] vs one [<1%]), and rash (45 [8%] vs none). Serious adverse events were reported in 134 (23%) of 573 patients in the buparlisib group compared with 90 [16%] of 570 patients in the placebo group; the most common serious adverse events (affecting ≥2% of patients) were increased alanine aminotransferase (17 [3%] of 573 vs one [<1%] of 570) and increased aspartate aminotransferase (14 [2%] vs one [<1%]). No treatment-related deaths occurred. INTERPRETATION: The results from this study show that PI3K inhibition combined with endocrine therapy is effective in postmenopausal women with endocrine-resistant, hormone receptor-positive and HER2-negative advanced breast cancer. Use of more selective PI3K inhibitors, such as α-specific PI3K inhibitor, is warranted to further improve safety and benefit in this setting. No further studies are being pursued because of the toxicity associated with this combination. FUNDING: Novartis Pharmaceuticals Corporation.

AZD2171, a pan-VEGF receptor tyrosine kinase inhibitor, normalizes tumor vasculature and alleviates edema in glioblastoma patients.

Using MRI techniques, we show here that normalization of tumor vessels in recurrent glioblastoma patients by daily administration of AZD2171-an oral tyrosine kinase inhibitor of VEGF receptors-has rapid onset, is prolonged but reversible, and has the significant clinical benefit of alleviating edema. Reversal of normalization began by 28 days, though some features persisted for as long as four months. Basic FGF, SDF1alpha, and viable circulating endothelial cells (CECs) increased when tumors escaped treatment, and circulating progenitor cells (CPCs) increased when tumors progressed after drug interruption. Our study provides insight into different mechanisms of action of this class of drugs in recurrent glioblastoma patients and suggests that the timing of combination therapy may be critical for optimizing activity against this tumor.

Phase I dose-escalation and -expansion study of buparlisib (BKM120), an oral pan-Class I PI3K inhibitor, in patients with advanced solid tumors.

PURPOSE: The pan-Class I PI3K inhibitor buparlisib (BKM120) has shown activity in a range of preclinical cancer models. This first-in-man study was initiated to identify the maximum tolerated dose (MTD) of buparlisib (100 mg/day) and to assess safety and preliminary efficacy. METHODS: Patients with advanced solid tumors (N = 83) enrolled in a Phase I dose-escalation and -expansion study of single-agent buparlisib. Patients in the dose-expansion arm (n = 43) had tumor samples with PIK3CA and/or PTEN alterations. RESULTS: The most common cancers were colorectal (n = 31) and breast cancer (n = 21). Median number of prior antineoplastic regimens was four (range: 1-12). Grade 3/4 adverse events (AEs) included asthenia (12.0 %) and performance status decrease (9.6 %). Treatment-related AEs (all grades) included decreased appetite, diarrhea, nausea (each in 33 % of patients), hyperglycemia (31 %) and rash (29 %). One confirmed partial response (PR; triple-negative breast cancer) and three unconfirmed PRs (parotid gland carcinoma, epithelioid hemangiothelioma, ER + breast cancer) were reported. Tumor molecular status did not predict clinical benefit in the full study cohort, or among the colorectal or breast cancer subpopulations. Pharmacodynamic biomarkers ((18)F-FDG-PET, C-peptide, pS6) demonstrated dose-dependent changes; however, tumor heterogeneity precluded a clear correlation with clinical benefit. CONCLUSION: Buparlisib was well tolerated up to the 100 mg/day dose and showed preliminary activity in patients with advanced cancers. Future studies in more homogeneous patient populations will evaluate buparlisib in combination with other agents and further investigate the use of predictive biomarkers.

Engineered blood vessel networks connect to host vasculature via wrapping-and-tapping anastomosis.

Rapid blood perfusion is critical for postimplantation survival of thick, prevascularized bioartificial tissues. Yet the mechanism by which implanted vascular networks inosculate, or anastomose, with the host vasculature has been unknown, making it difficult to develop optimized strategies for facilitating perfusion. Here we show that implanted vascular networks anastomose with host vessels through a previously unidentified process of "wrapping and tapping" between the engrafted endothelial cells (ECs) and the host vasculature. At the host-implant interface, implanted ECs first wrap around nearby host vessels and then cause basement membrane and pericyte reorganization and localized displacement of the underlying host endothelium. In this way, the implanted ECs replace segments of host vessels to divert blood flow to the developing implanted vascular network. The process is facilitated by high levels of matrix metalloproteinase-14 and matrix metalloproteinase-9 expressed by the wrapping ECs. These findings open the door to new strategies for improving perfusion of tissue grafts and may have implications for other physiologic and pathologic processes involving postnatal vasculogenesis.

Hearing improvement after bevacizumab in patients with neurofibromatosis type 2.

BACKGROUND: Profound hearing loss is a serious complication of neurofibromatosis type 2, a genetic condition associated with bilateral vestibular schwannomas, benign tumors that arise from the eighth cranial nerve. There is no medical treatment for such tumors. METHODS: We determined the expression pattern of vascular endothelial growth factor (VEGF) and three of its receptors, VEGFR-2, neuropilin-1, and neuropilin-2, in paraffin-embedded samples from 21 vestibular schwannomas associated with neurofibromatosis type 2 and from 22 sporadic schwannomas. Ten consecutive patients with neurofibromatosis type 2 and progressive vestibular schwannomas who were not candidates for standard treatment were treated with bevacizumab, an anti-VEGF monoclonal antibody. An imaging response was defined as a decrease of at least 20% in tumor volume, as compared with baseline. A hearing response was defined as a significant increase in the word-recognition score, as compared with baseline. RESULTS: VEGF was expressed in 100% of vestibular schwannomas and VEGFR-2 in 32% of tumor vessels on immunohistochemical analysis. Before treatment, the median annual volumetric growth rate for 10 index tumors was 62%. After bevacizumab treatment in the 10 patients, tumors shrank in 9 patients, and 6 patients had an imaging response, which was maintained in 4 patients during 11 to 16 months of follow-up. The median best response to treatment was a volumetric reduction of 26%. Three patients were not eligible for a hearing response; of the remaining seven patients, four had a hearing response, two had stable hearing, and one had progressive hearing loss. There were 21 adverse events of grade 1 or 2. CONCLUSIONS: VEGF blockade with bevacizumab improved hearing in some, but not all, patients with neurofibromatosis type 2 and was associated with a reduction in the volume of most growing vestibular schwannomas.

Kinetics of vascular normalization by VEGFR2 blockade governs brain tumor response to radiation: role of oxygenation, angiopoietin-1, and matrix metalloproteinases.

The recent landmark Phase III clinical trial with a VEGF-specific antibody suggests that antiangiogenic therapy must be combined with cytotoxic therapy for the treatment of solid tumors. However, there are no guidelines for optimal scheduling of these therapies. Here we show that VEGFR2 blockade creates a "normalization window"--a period during which combined radiation therapy gives the best outcome. This window is characterized by an increase in tumor oxygenation, which is known to enhance radiation response. During the normalization window, but not before or after it, VEGFR2 blockade increases pericyte coverage of brain tumor vessels via upregulation of Ang1 and degrades their pathologically thick basement membrane via MMP activation.

Direct evidence that the VEGF-specific antibody bevacizumab has antivascular effects in human rectal cancer.

The effects of vascular endothelial growth factor (VEGF) blockade on the vascular biology of human tumors are not known. Here we show here that a single infusion of the VEGF-specific antibody bevacizumab decreases tumor perfusion, vascular volume, microvascular density, interstitial fluid pressure and the number of viable, circulating endothelial and progenitor cells, and increases the fraction of vessels with pericyte coverage in rectal carcinoma patients. These data indicate that VEGF blockade has a direct and rapid antivascular effect in human tumors.

Plasma soluble VEGFR-1 is a potential dual biomarker of response and toxicity for bevacizumab with chemoradiation in locally advanced rectal cancer.

We explored plasma and urinary concentrations of two members of the vascular endothelial growth factor (VEGF) family and their receptors as potential response and toxicity biomarkers of bevacizumab with neoadjuvant chemoradiation in patients with localized rectal cancer. The concentrations of VEGF, placental growth factor (PlGF), soluble VEGF receptor 1 (sVEGFR-1), and sVEGFR-2 were measured in plasma and urine at baseline and during treatment. Pretreatment values and changes over time were analyzed as potential biomarkers of pathological response to treatment as well as for acute toxicity in patients with locally advanced rectal cancer treated prospectively in 2002-2008 with neoadjuvant bevacizumab, 5-fluorouracil, radiation therapy, and surgery in a phase I/II trial. Of all biomarkers, pretreatment plasma sVEGFR-1-an endogenous blocker of VEGF and PlGF, and a factor linked with "vascular normalization"-was associated with both primary tumor regression and the development of adverse events after neoadjuvant bevacizumab and chemoradiation. Based on the findings in this exploratory study, we propose that plasma sVEGFR-1 should be further studied as a potential biomarker to stratify patients in future studies of bevacizumab and/or cytotoxics in the neoadjuvant setting.

Pathology: cancer cells compress intratumour vessels.

The delivery of therapeutic drugs to solid tumours may be impaired by structural and functional abnormalities in blood and lymphatic vessels. Here we provide evidence that proliferating cancer cells cause intratumour vessels to compress and collapse. By reducing this compressive mechanical force and opening vessels, cytotoxic cancer treatments have the potential to increase blood perfusion, thereby improving drug delivery.

Discovery and Characterization of SY-1365, a Selective, Covalent Inhibitor of CDK7.

Recent studies suggest that targeting transcriptional machinery can lead to potent and selective anticancer effects in cancers dependent on high and constant expression of certain transcription factors for growth and survival. Cyclin-dependent kinase 7 (CDK7) is the catalytic subunit of the CDK-activating kinase complex. Its function is required for both cell-cycle regulation and transcriptional control of gene expression. CDK7 has recently emerged as an attractive cancer target because its inhibition leads to decreased transcript levels of oncogenic transcription factors, especially those associated with super-enhancers. Here, we describe a selective CDK7 inhibitor SY-1365, which is currently in clinical trials in populations of patients with ovarian and breast cancer (NCT03134638). In vitro, SY-1365 inhibited cell growth of many different cancer types at nanomolar concentrations. SY-1365 treatment decreased MCL1 protein levels, and cancer cells with low BCL2L1 (BCL-XL) expression were found to be more sensitive to SY-1365. Transcriptional changes in acute myeloid leukemia (AML) cell lines were distinct from those following treatment with other transcriptional inhibitors. SY-1365 demonstrated substantial antitumor effects in multiple AML xenograft models as a single agent; SY-1365-induced growth inhibition was enhanced in combination with the BCL2 inhibitor venetoclax. Antitumor activity was also observed in xenograft models of ovarian cancer, suggesting the potential for exploring SY-1365 in the clinic in both hematologic and solid tumors. Our findings support targeting CDK7 as a new approach for treating transcriptionally addicted cancers. SIGNIFICANCE: These findings demonstrate the molecular mechanism of action and potent antitumor activity of SY-1365, the first selective CDK7 inhibitor to enter clinical investigation.

The potent and selective cyclin-dependent kinases 4 and 6 inhibitor ribociclib (LEE011) is a versatile combination partner in preclinical cancer models.

Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of ribociclib. When tested across a large panel of kinase active site binding assays, ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both ribociclib and abemaciclib showed slightly higher potency in CDK4-dependent cells than in CDK6-dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.

Complete pathological response to bevacizumab and chemoradiation in advanced rectal cancer.

BACKGROUND: Localized rectal cancer responds well to 5-fluorouracil and radiation-based regimens. A phase I-II trial is currently testing the efficacy of adding bevacizumab, a VEGF-specific antibody, to standard chemoradiotherapy. The case presented here is a complete pathological response seen in a patient with extensive and locally invasive carcinoma after receiving this combined treatment. INVESTIGATIONS: Physical examination, rectal ultrasound, PET-CT scan, laboratory tests, proctoscopic examination, chest radiograph, rectal forcep biopsies with immunohistochemistry, and protein and flow cytometric analyses. DIAGNOSIS: Large, invasive, ultrasound stage T4 carcinoma of the rectum, which was positive for survivin. MANAGEMENT: One 2-week cycle of bevacizumab alone, followed by 3 cycles of bevacizumab with continuous 5-fluorouracil infusion, and external-beam radiation therapy given 5 days per week to the pelvis, abdominoperineal resection with posterior vaginectomy, hysterectomy and bilateral salpingo-oophorectomy.

Robust 3-D modeling of vasculature imagery using superellipsoids.

This paper presents methods to model complex vasculature in three-dimensional (3-D) images using cylindroidal superellipsoids, along with robust estimation and detection algorithms for automated image analysis. This model offers an explicit, low-order parameterization, enabling joint estimation of boundary, centerlines, and local pose. It provides a geometric framework for directed vessel traversal, and extraction of topological information like branch point locations and connectivity. M-estimators provide robust region-based statistics that are used to drive the superellipsoid toward a vessel boundary. A robust likelihood ratio test is used to differentiate between noise, artifacts, and other complex unmodeled structures, thereby verifying the model estimate. The proposed methodology behaves well across scale-space, shows a high degree of insensitivity to adjacent structures and implicitly handles branching. When evaluated on synthetic imagery mimicking specific structural complexities in tumor microvasculature, it consistently produces ubvoxel accuracy estimates of centerlines and widths in the presence of closely-adjacent vessels, branch points, and noise. An edit-based validation demonstrated a precision level of 96.6% at a recall level of 95.4%. Overall, it is robust enough for large-scale application.

Mosaic tumor vessels: cellular basis and ultrastructure of focal regions lacking endothelial cell markers.

Endothelial cells of blood vessels in tumors may be thin, fragile, and defective in barrier function. We found previously that the endothelium of vessels in human colon carcinoma xenografts in mice is a mosaic structure. Approximately 85% of tumor vessels have uniform CD31 and/or CD105 immunoreactivity, but the remainder have focal regions that lack these common endothelial markers. The present study assessed the ultrastructure of the vessel lining and the integrity of the basement membrane in these regions. Using immunolabeling and confocal microscopy, we identified blood vessels that lacked CD31 and CD105 immunoreactivity and then analyzed the ultrastructure of these vessels by transmission electron microscopy. Eleven percent of vessels in orthotopic tumors and 24% of vessels in ectopic tumors had defects in CD31 and CD105 staining measuring on average 10.8 microm (range, 1-41.2 microm). Ultrastructural studies identified endothelial cells at 92% of CD31- and CD105-negative sites in orthotopic tumors and 70% of the sites in ectopic tumors. Thus, most regions of tumor vessels that lack CD31 and CD105 immunoreactivity represent attenuated endothelial cells with abnormal expression of endothelial cell markers, but some are gaps between endothelial cells. More than 80% of the defects lacked immunoreactivity for multiple basement membrane proteins.

Platelet-derived growth factor receptor-beta in Gorham's disease.

BACKGROUND: A 17-year-old male presented with pain in his lower-left chest. He had no significant medical history and was previously in good health. He had a fractured ninth left anterior rib and the tenth, eleventh and twelfth ribs were absent, which was thought to be a congenital anomaly. Several months later, he presented again with back pain, an enlarging mass in the lower-left chest wall, erosion of the lateral pedicles of the lower thoracic vertebrae and pleural effusion. INVESTIGATIONS: Physical examination, chest X-ray, MRI of the spine, incisional biopsy, serial CT imaging of the hemithorax, immunohistochemistry, flow cytometry, and enzyme-linked immunosorbent assays. DIAGNOSIS: Gorham's lymphangiomatosis with expression of platelet-derived growth factor receptor-beta and elevated circulating platelet-derived growth factor-BB. MANAGEMENT: Spine stabilization, thalidomide, celecoxib, interferon-alpha2b, pamidronate, zoledronate, thoracotomy, pleurectomy, talc pleurodesis, and imatinib mesylate.

Combined vascular endothelial growth factor-targeted therapy and radiotherapy for rectal cancer: theory and clinical practice.

Despite the routine use of adjuvant and neoadjuvant chemoradiotherapy, patients with advanced rectal tumors experience significant rates of treatment failure and disease recurrence. Resistance to radiation is a particular problem. Adding a vascular endothelial growth factor (VEGF)-targeted therapy may improve outcomes in these patients. Epidemiologic studies have shown that tumor expression of VEGF predicts disease recurrence and lower overall survival in patients treated with radiation. In tumor xenograft models in mice, VEGF-targeted agents increase the response to radiation, with a greater probability of tumor control and a greater delay in tumor growth. In addition to killing cancer cells indirectly by damaging tumor blood vessels (antivascular effect), VEGF-targeted therapy may sensitize tumors to radiation through two mechanisms: by normalizing the tumor vasculature, leading to greater tumor oxygenation, and thereby increasing the cytotoxicity of radiation to cancer cells, and by increasing the radiosensitivity of tumor-associated endothelial cells. In addition, anti-VEGF agents may inhibit the regrowth of tumors after radiation by decreasing the number of circulating endothelial cells and endothelial progenitor cells. A phase I dose-escalation study has shown the safety of bevacizumab at a dose of 5 mg/kg in combination with 5-fluorouracil and radiation in patients with rectal carcinoma, and has provided evidence of both vascular normalization and antivascular mechanisms. Phase II evaluation of bevacizumab in this setting is under way.

Responses to antiangiogenesis treatment of spontaneous autochthonous tumors and their isografts.

Preclinical studies typically use human tumor xenografts or murine tumor isografts. Tumor growth may be accelerated by in vivo passage, thus making these tumors more sensitive to some therapies than the original tumors. In the present study, by comparing the effects of DC101, an antimurine vascular endothelial growth factor receptor 2 (VEGFR2) monoclonal antibody, on spontaneous autochthonous tumors and their early generation transplants, we show that this growth acceleration is diminished by DC101 treatment. Spontaneous autochthonous tumors in aged C3H mice consisted of s.c. sarcomas and adenocarcinomas, and their growth rate was accelerated by in vivo passages. Anti-VEGFR2 treatment decreased vessel density, increased apoptosis, and reduced tumor growth in large (500 mm(3)) spontaneous autochthonous tumors. Anti-VEGFR2 treatment significantly delayed tumor growth and extended animal survival. Tumor growth acceleration by in vivo passage was diminished by DC101 treatment. To our knowledge, this is the first evaluation of antiangiogenic therapy in a spontaneous autochthonous tumor model, which may more closely resemble human tumors. Additionally, this is the first study to compare treatment response between the parental tumor and its isografts. Although passaged tumors behave differently, it is encouraging that the tumor growth rates under DC101 treatment are comparable among different passage generations.

PI3K inhibitors as new cancer therapeutics: implications for clinical trial design.

The PI3K-AKT-mTOR pathway is frequently activated in cancer. PI3K inhibitors, including the pan-PI3K inhibitor buparlisib (BKM120) and the PI3Kα-selective inhibitor alpelisib (BYL719), currently in clinical development by Novartis Oncology, may therefore be effective as anticancer agents. Early clinical studies with PI3K inhibitors have demonstrated preliminary antitumor activity and acceptable safety profiles. However, a number of unanswered questions regarding PI3K inhibition in cancer remain, including: what is the best approach for different tumor types, and which biomarkers will accurately identify the patient populations most likely to benefit from specific PI3K inhibitors? This review summarizes the strategies being employed by Novartis Oncology to help maximize the benefits of clinical studies with buparlisib and alpelisib, including stratification according to PI3K pathway activation status, selective enrollment/target enrichment (where patients with PI3K pathway-activated tumors are specifically recruited), nonselective enrollment with mandatory tissue collection, and enrollment of patients who have progressed on previous targeted agents, such as mTOR inhibitors or endocrine therapy. An overview of Novartis-sponsored and Novartis-supported trials that are utilizing these approaches in a range of cancer types, including breast cancer, head and neck squamous cell carcinoma, non-small cell lung carcinoma, lymphoma, and glioblastoma multiforme, is also described.

Safety and Efficacy of Buparlisib (BKM120) in Patients with PI3K Pathway-Activated Non-Small Cell Lung Cancer: Results from the Phase II BASALT-1 Study.

INTRODUCTION: The phosphatidylinositol 3-kinase (PI3K) pathway promotes tumor growth and treatment resistance in non-small cell lung cancer (NSCLC). The aim of the open-label, two-stage, Phase II study BASALT-1 (NCT01820325) was to investigate the pan-PI3K inhibitor buparlisib (BKM120) in patients with PI3K pathway-activated, relapsed NSCLC. METHODS: After prescreening for PI3K pathway activation, patients with PI3K pathway-activated, metastatic, squamous or nonsquamous NSCLC, who had relapsed after prior systemic antineoplastic therapy, were enrolled. In Stage 1, patients received single-agent buparlisib (100 mg/day). A futility analysis was performed independently in each histology group, based on the 12-week progression-free survival rate for the first 30 patients treated in each group being less than 50%. Exploratory biomarker analyses were performed in archival tissue samples and circulating tumor DNA (ctDNA). RESULTS: Of 1242 prescreened patients, 13.5% exhibited PI3K pathway activation. As of June 5, 2014, 63 patients (30 squamous and 33 nonsquamous) were treated in Stage 1. The 12-week progression-free survival rates were 23.3% (95% confidence interval: 9.9-42.3) and 20.0% (95% confidence interval: 7.7-38.6) in the squamous and nonsquamous groups, respectively. Stage 2 was therefore not initiated in either group. PI3K pathway mutations in ctDNA were more concordant with metastatic tissue than with primary biopsies. CONCLUSIONS: Despite preselecting patients for targeted treatment, BASALT-1 did not meet its primary objective during Stage 1. PI3K pathway activation can be detected using ctDNA, but may not be the main oncogenic driver in NSCLC. Combinations of PI3K inhibitors with other agents may demonstrate greater efficacy than monotherapy.