ER+, HER2- advanced breast cancer treated with taselisib and fulvestrant: genomic landscape and associated clinical outcomes

Taselisib is a potent β-sparing phosphatidylinositol 3-kinase (PI3K) inhibitor that, with endocrine therapy, improves outcomes in phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA)-mutated (PIK3CAmut) advanced breast cancer. To understand alterations associated with response to PI3K inhibition, we analysed circulating tumour DNA (ctDNA) from participants enrolled in the SANDPIPER trial. Participants were designated as either PIK3CAmut or PIK3CA no mutation was detected (NMD) per baseline ctDNA. The top mutated genes and tumour fraction estimates identified were analysed for their association with outcomes. In participants with PIK3CAmut ctDNA treated with taselisib + fulvestrant, tumour protein p53 (TP53; encoding p53) and fibroblast growth factor receptor 1 (FGFR1) alterations were associated with shorter progression-free survival (PFS) compared to participants with NMD in these genes. Conversely, participants with PIK3CAmut ctDNA harbouring a neurofibromin 1 (NF1) alteration or high baseline tumour fraction estimate experienced improved PFS upon treatment with taselisib + fulvestrant compared to placebo + fulvestrant. Broadly, alterations in oestrogen receptor (ER), PI3K and p53 pathway genes were associated with resistance to taselisib + fulvestrant in participants with PIK3CAmut ctDNA. Altogether, we demonstrated the impact of genomic (co-)alterations on outcomes with one of the largest clinico-genomic datasets of ER+, HER2-, PIK3CAmut breast cancer patients treated with a PI3K inhibitor.

Identifying malnutrition in emergency general surgery: systematic review

BACKGROUND

Emergency general surgery practice is high risk. Surgery is a key part of treatment, with resultant catabolic stress and frequent need for nutritional support. The aim of this study was to examine the current methods of defining and determining malnutrition in emergency general surgery. This included examining the use of nutrition screening and assessment tools and other measures of malnutrition.

METHODS

MEDLINE, Embase, Cumulative Index to Nursing and Allied Health Literature, trial registries, and relevant journals published between January 2000 and January 2022 were searched for studies of adult patients with any emergency general surgery diagnosis, managed conservatively or operatively, with an assessment of nutritional status. Mixed populations were included if more than 50 per cent of patients were emergency general surgery patients or emergency general surgery results could be separately extracted. Studies in which patients had received nutritional support were excluded. The protocol was registered with PROSPERO, the international prospective register of systematic reviews (CRD42021285897).

RESULTS

From 6700 studies screened, 324 full texts were retrieved and 31 were included in the analysis. A definition of malnutrition was provided in 23 studies (75 per cent), with nutritional status being determined by a variety of methods. A total of seven nutrition screening tools and a total of nine 'assessment' tools were reported. To define malnutrition, the most commonly used primary or secondary marker of nutritional status was BMI, followed by albumin level.

CONCLUSION

Wide variation exists in approaches to identify malnutrition risk in emergency general surgery patients, using a range of tools and nutrition markers. Future studies should seek to standardize nutrition screening and assessment in the emergency general surgery setting as two discrete processes. This will permit better understanding of malnutrition risk in surgical patients.

Screening for malnutrition in emergency laparotomy patients: a comparison of three tools

INTRODUCTION

Malnourished patients undergoing emergency laparotomy are at risk of significant morbidity. The optimum screening tool to identify such patients in practice and research is yet to be determined. This study aims to compare the performance of three nutrition risk tools in predicting time without enteral nutrition in this population.

METHODS

A prospective cohort study (NCT04696367) was conducted across two sites, recruiting patients undergoing National Emergency Laparotomy Audit eligible procedures. Data collected included demographics, diagnosis, procedure and outcomes. Nutrition risk was assessed using three tools: Malnutrition Universal Screening Tool (MUST) score, Nutritional Risk Index (NRI) and Nutritional Risk Score 2002 (NRS-2002). Complications were assessed with the Comprehensive Complication Index. Quality of life was measured at baseline and 5 days postsurgery using EQ-5D-5L.

RESULTS

A total of 59 patients were recruited. Median age was 69 years. Of the 59 participants, 23 were judged high risk using MUST score, 13 using NRS and 8 using NRI. Median time to restart enteral intake was 7 days (interquartile range 7-14). Time without intake was correlated with increasing score using MUST (r=0.463, p<0.001) and NRS-2002 (r=0.296, p=0.03) but not NRI (r=-0.121, p=0.38). High-risk nutritional groups also had increased length of hospital stay, but not complication scores.

CONCLUSIONS

Patients undergoing emergency laparotomy spend a prolonged time without enteral nutrition. Although all nutritional tools demonstrated some propensity to identify patients at higher risk of needing nutritional support, their performance was variable. Nevertheless, some may be useful in future clinical studies.

Multiple PIK3CA mutation clonality correlates with outcomes in taselisib + fulvestrant-treated ER+/HER2-, PIK3CA-mutated breast cancers

BACKGROUND

Mutations in the p110α catalytic subunit of phosphatidylinositol 3-kinase (PI3K), encoded by the PIK3CA gene, cause dysregulation of the PI3K pathway in 35-40% of patients with HR+/HER2- breast cancer. Preclinically, cancer cells harboring double or multiple PIK3CA mutations (mut) elicit hyperactivation of the PI3K pathway leading to enhanced sensitivity to p110α inhibitors.

METHODS

To understand the role of multiple PIK3CAmut in predicting response to p110α inhibition, we estimated the clonality of multiple PIK3CAmut in circulating tumor DNA (ctDNA) from patients with HR+/HER2- metastatic breast cancer enrolled to a prospectively registered clinical trial of fulvestrant ± taselisib, and analyzed the subgroups against co-altered genes, pathways, and outcomes.

RESULTS

ctDNA samples with clonal multiple PIK3CAmut had fewer co-alterations in receptor tyrosine kinase (RTK) or non-PIK3CA PI3K pathway genes compared to samples with subclonal multiple PIK3CAmut indicating a strong reliance on the PI3K pathway. This was validated in an independent cohort of breast cancer tumor specimens that underwent comprehensive genomic profiling. Furthermore, patients whose ctDNA harbored clonal multiple PIK3CAmut exhibited a significantly higher response rate and longer progression-free survival vs subclonal multiple PIK3CAmut.

CONCLUSIONS

Our study establishes clonal multiple PIK3CAmut as an important molecular determinant of response to p110α inhibition and provides rationale for further clinical investigation of p110α inhibitors alone or with rationally-selected therapies in breast cancer and potentially other solid tumor types.

Genetic Heterogeneity and Tissue-specific Patterns of Tumors with Multiple PIK3CA Mutations

PURPOSE

To comprehensively characterize tissue-specific and molecular subclasses of multiple PIK3CA (multi-PIK3CA) mutations and assess their impact on potential therapeutic outcomes.

EXPERIMENTAL DESIGN

We profiled a pan-cancer cohort comprised of 352,392 samples across 66 tumor types using a targeted hybrid capture-based next-generation sequencing panel covering at least 324 cancer-related genes. Molecularly defined subgroups, allelic configuration, clonality, and mutational signatures were identified and tested for association with PI3K inhibitor therapeutic response.

RESULTS

Multi-PIK3CA mutations are found in 11% of all PIK3CA-mutant tumors, including 9% of low tumor mutational burden (TMB) PIK3CA-mutant tumors, and are enriched in breast and gynecologic cancers. Multi-PIK3CA mutations are frequently clonal and in cis on the same allele and occur at characteristic positions across tumor types. These mutations tend to be mutually exclusive of mutations in other driver genes, and of genes in the PI3K pathway. Among PIK3CA-mutant tumors with a high TMB, 18% are multi-PIK3CA mutant and often harbor an apolipoprotein B mRNA-editing enzyme, catalytic polypeptide (APOBEC) mutational signature. Despite large differences in specific allele combinations comprising multi-PIK3CA mutant tumors, especially across cancer types, patients with different classes of multi-PIK3CA mutant estrogen receptor-positive, HER2-negative breast cancers respond similarly to PI3K inhibition.

CONCLUSIONS

Our pan-tumor study provides biological insights into the genetic heterogeneity and tissue specificities of multi-PIK3CA mutations, with potential clinical utility to guide PI3K inhibition strategies.

Geometry of Charge Density as a Reporter on the Role of the Protein Scaffold in Enzymatic Catalysis: Electrostatic Preorganization and Beyond

Enzymes host active sites inside protein macromolecules, which have diverse, often incredibly complex, and atom-expensive structures. It is an outstanding question what the role of these expensive scaffolds might be in enzymatic catalysis. Answering this question is essential to both enzymology and the design of artificial enzymes with proficiencies that will match those of the best natural enzymes. Protein rigidifying the active site, contrasted with the dynamics and vibrational motion promoting the reaction, as well as long-range electrostatics (also known as electrostatic preorganization) were all proposed as central contributions of the scaffold to the catalysis. Here, we show that all these effects inevitably produce changes in the quantum mechanical electron density in the active site, which in turn defines the reactivity. The phenomena are therefore fundamentally inseparable. The geometry of the electron density-a scalar field characterized by a number of mathematical features such as critical points-is a rigorous and convenient descriptor of enzymatic catalysis and a reporter on the role of the protein. We show how this geometry can be analyzed, linked to the reaction barriers, and report in particular on intramolecular electric fields in enzymes. We illustrate these tools on the studies of electrostatic preorganization in several representative enzyme classes, both natural and artificial. We highlight the forward-looking aspects of the approach.

Unicorns, Rhinoceroses and Chemical Bonds

The nascent field of computationally aided molecular design will be built around the ability to make computation useful to synthetic chemists who draw on their empirically based chemical intuition to synthesize new and useful molecules. This fact poses a dilemma, as much of existing chemical intuition is framed in the language of chemical bonds, which are pictured as possessing physical properties. Unfortunately, it has been posited that calculating these bond properties is impossible because chemical bonds do not exist. For much of the computationalchemistry community, bonds are seen as mythical-the unicorns of the chemical world. Here, we show that this is not the case. Using the same formalism and concepts that illuminated the atoms in molecules, we shine light on the bonds that connect them. The real space analogue of the chemical bond becomes the bond bundle in an extended quantum theory of atoms in molecules (QTAIM). We show that bond bundles possess all the properties typically associated with chemical bonds, including an energy and electron count. In addition, bond bundles are characterized by a number of nontraditional attributes, including, significantly, a boundary. We show, with examples drawn from solid state and molecular chemistry, that the calculated properties of bond bundles are consistent with those that nourish chemical intuition. We go further, however, and show that bond bundles provide new and quantifiable insights into the structure and properties of molecules and materials.

Safety and immunogenicity of AGS-v PLUS, a mosquito saliva peptide vaccine against arboviral diseases: A randomized, double-blind, placebo-controlled Phase 1 trial

BACKGROUND

Immunity to mosquito salivary proteins could provide protection against multiple mosquito-borne diseases and significantly impact public health. We evaluated the safety and immunogenicity of AGS-v PLUS, a mosquito salivary peptide vaccine, in healthy adults 18-50 years old.

METHODS

We conducted a randomized, double-blind, placebo-controlled Phase 1 study of AGS-v PLUS administered subcutaneously on Days 1 and 22 at the Center for Vaccine Development and Global Health, Baltimore, MD, USA. Participants were block randomized 1:1:1:1:1 to two doses saline placebo, two doses AGS-v PLUS, AGS-v PLUS/ISA-51 and saline placebo, two doses AGS-v PLUS/ISA-51, or two doses AGS-v PLUS/Alhydrogel. Primary endpoints were safety (all participants receiving ≥1 injection) and antibody and cytokine responses (all participants with day 43 samples), analysed by intention to treat.

FINDINGS

Between 26 August 2019 and 25 February 2020, 51 participants were enrolled and randomized, 11 into the single dose AGS-v PLUS/ISA-51 group and ten in other groups. Due to COVID-19, 15 participants did not return for day 43 samplings. Participants experienced no treatment-emergent or serious adverse events. All solicited symptoms in 2/10 placebo recipients and 22/41 AGS-v PLUS recipients after dose one and 1/10 placebo recipients and 22/41 AGS-v PLUS recipients after dose two were mild/moderate except for one severe fever the day after vaccination (placebo group). Only injection site pain was more common in vaccine groups (15/51 after dose 1 and 11/51 after dose 2) versus placebo. Compared to placebo, all vaccine groups had significantly greater fold change in anti-AGS-v PLUS IgG and IFN-ɣ from baseline.

INTERPRETATION

AGS-v PLUS had favourable safety profile and induced robust immune responses. Next steps will determine if findings translate into clinical efficacy against mosquito-borne diseases.

FUNDING

UK Department of Health and Social Care.

Bond Bundle Analysis of Ketosteroid Isomerase

Bond bundle analysis is used to investigate enzymatic catalysis in the ketosteroid isomerase (KSI) active site. We identify the unique bonding regions in five KSI systems, including those exposed to applied oriented electric fields and those with amino acid mutations, and calculate the precise redistribution of electron density and other regional properties that accompanies either enhancement or inhibition of KSI catalytic activity. We find that catalytic enhancement results from promoting both inter- and intra-molecular electron density redistribution, between bond bundles and bond wedges within the KSI-docked substrate molecule, in the forward direction of the catalyzed reaction. Though the redistribution applies to both types of perturbed systems and is thus suggestive of a general catalytic role, we observe that bond properties (e.g., volume vs energy vs electron count) can respond independently and disproportionately depending on the type of perturbation. We conclude that the resulting catalytic enhancement/inhibition proceeds via different mechanisms, where some bond properties are utilized more by one type of perturbation than the other. Additionally, we find that the correlations between bond wedge properties and catalyzed reaction barrier energies are additive to predict those of bond bundles and atomic basins, providing a rigorous grounding for connecting changes in local charge density to resulting shifts in reaction barrier energy.

MET gene amplification is a mechanism of resistance to entrectinib in ROS1+ NSCLC

BACKGROUND

ROS1 tyrosine kinase inhibitors (TKIs) have demonstrated significant clinical benefit for ROS1+ NSCLC patients. However, TKI resistance inevitably develops through ROS1 kinase domain (KD) modification or another kinase driving bypass signaling. While multiple TKIs have been designed to target ROS1 KD mutations, less is known about bypass signaling in TKI-resistant ROS1+ lung cancers.

METHODS

Utilizing a primary, patient-derived TPM3-ROS1 cell line (CUTO28), we derived an entrectinib-resistant line (CUTO28-ER). We evaluated proliferation and signaling responses to TKIs, and utilized RNA sequencing, whole exome sequencing, and fluorescence in situ hybridization to detect transcriptional, mutational, and copy number alterations, respectively. We substantiated in vitro findings using a CD74-ROS1 NSCLC patient's tumor samples. Last, we analyzed circulating tumor DNA (ctDNA) from ROS1+ NSCLC patients in the STARTRK-2 entrectinib trial to determine the prevalence of MET amplification.

RESULTS

CUTO28-ER cells did not exhibit ROS1 KD mutations. MET TKIs inhibited proliferation and downstream signaling and MET transcription was elevated in CUTO28-ER cells. CUTO28-ER cells displayed extrachromosomal (ecDNA) MET amplification without MET activating mutations, exon 14 skipping, or fusions. The CD74-ROS1 patient samples illustrated MET amplification while receiving ROS1 TKI. Finally, two of 105 (1.9%) entrectinib-resistant ROS1+ NSCLC STARTRK-2 patients with ctDNA analysis at enrollment and disease progression displayed MET amplification.

CONCLUSIONS

Treatment with ROS1-selective inhibitors may lead to MET-mediated resistance. The discovery of ecDNA MET amplification is noteworthy, as ecDNA is associated with more aggressive cancers. Following progression on ROS1-selective inhibitors, MET gene testing and treatments targeting MET should be explored to overcome MET-driven resistance.

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

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

VERONICA: Randomized Phase II Study of Fulvestrant and Venetoclax in ER-Positive Metastatic Breast Cancer Post-CDK4/6 Inhibitors - Efficacy, Safety, and Biomarker Results

PURPOSE

Despite promising activity in hematopoietic malignancies, efficacy of the B-cell lymphoma 2 (BCL2) inhibitor venetoclax in solid tumors is unknown. We report the prespecified VERONICA primary results, a randomized phase II clinical trial evaluating venetoclax and fulvestrant in estrogen receptor (ER)-positive, HER2-negative metastatic breast cancer, post-cyclin-dependent kinase (CDK) 4/6 inhibitor progression.

PATIENTS AND METHODS

Pre-/postmenopausal females ≥18 years were randomized 1:1 to venetoclax (800 mg orally daily) plus fulvestrant (500 mg intramuscular; cycle 1: days 1 and 15; subsequent 28-day cycles: day 1) or fulvestrant alone. The primary endpoint was clinical benefit rate (CBR); secondary endpoints were progression-free survival (PFS), overall survival, and safety. Exploratory biomarker analyses included BCL2 and BCL extra-large (BCLXL) tumor expression, and PIK3CA circulating tumor DNA mutational status.

RESULTS

At primary analysis (cutoff: August 5, 2020; n = 103), venetoclax did not significantly improve CBR [venetoclax plus fulvestrant: 11.8% (n = 6/51; 95% confidence interval (CI), 4.44-23.87); fulvestrant: 13.7% (7/51; 5.70-26.26); risk difference -1.96% (95% CI, -16.86 to 12.94)]. Median PFS was 2.69 months (95% CI, 1.94-3.71) with venetoclax plus fulvestrant versus 1.94 months (1.84-3.55) with fulvestrant (stratified HR, 0.94; 95% CI, 0.61-1.45; P = 0.7853). Overall survival data were not mature. A nonsignificant improvement of CBR and PFS was observed in patients whose tumors had strong BCL2 expression (IHC 3+), a BCL2/BCLXL Histoscore ratio ≥1, or PIK3CA-wild-type status.

CONCLUSIONS

Our findings do not indicate clinical utility for venetoclax plus fulvestrant in endocrine therapy-resistant, CDK4/6 inhibitor-refractory metastatic breast tumors, but suggest possible increased dependence on BCLXL in this setting.

Abstract 1103: MET gene amplification is a mechanism of resistance to entrectinib in ROS1+ NSCLC

ROS1 TKIs entrectinib and crizotinib have significantly improved outcomes for ROS1+ lung adenocarcinoma patients. However, drug resistance inevitably develops, leading to disease progression. Approximately 1/3 of patients resistant to ROS1 TKIs demonstrate ROS1 kinase domain (KD) mutations (Dziadziuszko et al. ESMO 2019), but the mechanism of resistance in most patients is unknown or poorly characterized. To model and characterize acquired resistance to ROS1 TKIs, we used patient-derived cell line CUTO28 (TPM3-ROS1) to generate an entrectinib-resistant derivative (CUTO28-ER) in vitro. We utilized several techniques to probe the mechanisms driving resistance: DNA and RNA sequencing (seq), fluorescence in-situ hybridization (FISH), cell proliferation assays, and western blotting.

DNA seq of the ROS1 KD in CUTO28-ER failed to reveal mutations. CUTO28-ER cells displayed sensitivity to MET-selective TKIs in proliferation assays, and MAPK and AKT pathways were inhibited only with MET-selective TKI. RNA seq and western blot showed MET overexpression, and interphase FISH confirmed MET amplification compared to parental cells (MET:CEP7 ratio 4.2 vs 1.0). We substantiated in vitro findings in patient tissue, utilizing tumor samples at 2 different points of a single CD74-ROS1 NSCLC patient’s tumor progression. The first tumor sample did not display MET amplification while on ROS1 TKI (MET:CEP7 ratio 0.9, 3.4 copies of MET). However, the second tumor sample collected 5 months later displayed a MET:CEP7 ratio of 2.5 (9.5 copies of MET), indicating progression on ROS1 TKI was likely MET-driven. To determine prevalence of MET amplification in entrectinib-resistant ROS1+ NSCLC, we analyzed circulating tumor DNA (ctDNA) by FoundationOne Liquid CDx from patients with ROS1+ NSCLC in the STARTRK-2 entrectinib trial. Of 105 ROS1+ NSCLC patients with ctDNA analysis both at enrollment and progression, 2 (1.9%) displayed copy number amplification (CNA) of MET. Of these, 1 patient had no detectible CNA at study baseline but MET CNA gain by day 166 of entrectinib therapy and the other had detectable MET CNA gains both at baseline and at progression only 28 days later. Both received 3 lines of therapy prior to entrectinib, none of which targeted ROS1 or MET.

In conclusion, we demonstrated MET gene amplification as a potential mechanism of resistance to ROS1 TKI entrectinib. The prevalence of MET amplification at resistance was 2 of 105, but may be greater than was detected in STARTRK-2 due to the sensitivity of ctDNA assays and challenges of measuring CNA in ctDNA. Utilization of the ROS1/MET TKI crizotinib or combination of entrectinib with capmatinib should be explored in patients with ROS1+ NSCLC that display MET CNA to overcome MET-driven resistance following entrectinib.

Citation Format: Logan C. Tyler, Anh T. Le, Hala Nijmeh, Liming Bao, Timothy R. Wilson, Brian Simmons, David Chen, Robert C. Doebele. MET gene amplification is a mechanism of resistance to entrectinib in ROS1+ NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1103.

Abstract 5165: The genomic landscape and prognostic implications of somatic alterations in patients (pts) with ER+, HER2-, PIK3CA mutated (mut) advanced breast cancer treated with taselisib and fulvestrant

Background: Mutations in PIK3CA, encoding the catalytic subunit p110α of PI3K, are present in ~40% of ER+/HER- BC. Taselisib (TAS) is a potent and selective β-sparing PI3K inhibitor that improves outcomes in combination with endocrine therapy in pts with PIK3CAmut advanced breast cancer (aBC). To better understand the molecular alterations associated with response to PI3K inhibition, we profiled the genomic landscape of ctDNA collected from PIK3CAmut, ER+, HER2- aBC pts immediately prior to treatment (tx) with TAS or placebo (PBO) plus fulvestrant (FUL).

Methods: Pts were enrolled as part of a phase III randomized study of TAS or PBO plus FUL in ER+, HER2- PIK3CAmut aBC (SANDPIPER, NCT02340221). Pre-tx ctDNA samples from 508 pts underwent comprehensive genomic profiling using the FoundationOne Liquid NGS assay at Foundation Medicine, Inc.; the 339 pts with PIK3CAmut ctDNA were further analyzed herein. The top mutated genes were analyzed for prognostic value against investigator-assessed progression-free survival (PFS) for both tx regimens using Cox proportional hazards regression modeling. As analysis was exploratory, no adjustments were made for multiple testing.

Results: The top altered genes were TP53 (44%), ESR1 (37%), CDH1 (17%), FGFR1 (12%), NF1 (11%), CHEK2 (10%), and PTEN (9%). In pts treated with PBO+FUL, alterations in PTEN (HR 2.8; 95% CI 1.4-5.7; p=0.0107) and TP53 (HR 2.0; 95% CI 1.3-3.1; p=0.0025) were associated with a worse prognosis compared to pts with no mutation detected (NMD) in these genes. In pts treated with TAS+FUL, alterations in FGFR1 (HR 2.4; 95% CI 1.5-3.7; p=0.0006), TP53 (HR 1.9; 95% CI 1.4-2.6; p=0.0001) and PTEN (HR 1.8; 95% CI 1.1-2.8; p=0.0265) were associated with a worse prognosis compared to pts with NMD in these genes. Alterations in ESR1, CDH1, or CHEK2 were not associated with prognosis (p≥0.05) in either tx arm. A trend towards worse prognosis was observed in pts with NF1 altered ctDNA treated with PBO+FUL (HR 2.1; 95% CI 1.1-4.1; p=0.0527), which was not observed in pts treated with TAS+FUL (HR 0.97; 95% CI 0.57-1.65; p=0.901). Within the NF1-altered subgroup, a significant PFS difference was observed between TAS- vs PBO-treated pts (HR 0.28; 95% CI 0.11-0.67; p=0.0058; median 5.65 vs 1.94 months, respectively).

Conclusions: We report that the most frequently mutated genes identified are consistent with previous studies in pts with ER+, HER2- aBC. This analysis shows that alterations in TP53 and PTEN were associated with poor prognosis in both tx arms, and FGFR1 alterations were associated with a poor prognosis in TAS+FUL treated pts. Further, NF1 alterations were associated with a poor prognosis in PBO+FUL treated pts, an association that was not observed with TAS+FUL. These findings may inform future rational combination strategies for the clinical development of PI3K inhibitors.

Citation Format: Jessica W. Chen, Susan Dent, William Jacot, Javier Cortés, Ian E. Krop, Thomas J. Stout, Frauke Schimmoller, Heidi M. Savage, Katherine E. Hutchinson, Timothy R. Wilson. The genomic landscape and prognostic implications of somatic alterations in patients (pts) with ER+, HER2-, PIK3CA mutated (mut) advanced breast cancer treated with taselisib and fulvestrant [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5165.

Neighborhoods and functionality in metals

The fundamental construct of organic chemistry involves understanding molecular behavior through functional groups. Much of computational chemistry focuses on this very principle, but metallic materials are rarely analyzed using these techniques owing to the assumption that they are delocalized and do not possess inherent functionality. In this paper, we propose a methodology that recovers functional groups in metallic materials from an energy perspective. We characterize neighborhoods associated with functional groups in metals by observing the evolution of Bader energy of the central cluster as a function of cluster size. This approach can be used to conceptually decompose metallic structure into meaningful chemical neighborhoods allowing for localization of energy-dependent properties. The generalizability of this approach is assessed by determining neighborhoods for crystalline materials of different structure types, and significant structural defects such as grain boundaries and dislocations. In all cases, we observe that the neighborhood size may be universal-around 2-3 atomic diameters. In its practical sense, this approach opens the door to the application of chemical concepts, e.g., orbital methods, to investigate a broad range of metallurgical phenomena, one neighborhood at a time.

Updated Integrated Analysis of the Efficacy and Safety of Entrectinib in Patients With NTRK Fusion-Positive Solid Tumors

PURPOSE

Entrectinib potently inhibits tropomyosin receptor kinases (TRKAs)/B/C and ROS1, and previously induced deep [objective response rate (ORR) 57.4%] and durable [median duration of response (DoR) 10.4 months] responses in adults with NTRK fusion-positive solid tumors from three phase I/II trials. This article expands prior reports with additional patients and longer follow-up.

PATIENTS AND METHODS

Patients with locally advanced/metastatic NTRK fusion-positive solid tumors and ≥12 months' follow-up were included. Primary endpoints were ORR and DoR by blinded independent central review (BICR); secondary endpoints included progression-free survival (PFS), intracranial efficacy, and safety. The safety-evaluable populations included all patients who had received ≥1 entrectinib dose.

RESULTS

At clinical cut-off (August 31, 2020), the efficacy-evaluable population comprised 121 adults with 14 tumor types and ≥30 histologies. Median follow-up was 25.8 months; 61.2% of patients had a complete (n = 19) or partial response (n = 55). Median DoR was 20.0 months [95% confidence interval (CI), 13.0-38.2]; median PFS was 13.8 months (95% CI, 10.1-19.9). In 11 patients with BICR-assessed measurable central nervous system (CNS) disease, intracranial ORR was 63.6% (95% CI, 30.8-89.1) and median intracranial DoR was 22.1 (95% CI, 7.4-not estimable) months. The safety profile of entrectinib in adults and pediatric patients was aligned with previous reports. Most treatment-related adverse events (TRAEs) were grade 1/2 and manageable/reversible with dose modifications. TRAE-related discontinuations occurred in 8.3% of patients.

CONCLUSIONS

With additional clinical experience, entrectinib continues to demonstrate durable systemic and intracranial responses and can address the unmet need of a CNS-active treatment in patients with NTRK fusion-positive solid tumors.

Pre- and post-treatment blood-based genomic landscape of patients with ROS1 or NTRK fusion-positive solid tumors treated with entrectinib

Genomic tumor profiling informs targeted treatment options. Entrectinib is a tyrosine kinase inhibitor with efficacy in NTRK fusion-positive (-fp) solid tumors and ROS1-fp non-small cell lung cancer. FoundationOne^® Liquid CDx (F1L CDx), a non-invasive in vitro next-generation sequencing (NGS)-based diagnostic, detects genomic alterations in plasma circulating tumor DNA (ctDNA). We evaluated the clinical validity of F1L CDx as an aid in identifying patients with NTRK-fp or ROS1-fp tumors, and assessed the genomic landscape pre- and post-entrectinib treatment. Among evaluable pre-treatment clinical samples (N = 85), positive percentage agreements between F1L CDx and clinical trial assays (CTAs) were 47.4% (NTRK fusions) and 64.5% (ROS1 fusions); positive predictive value was 100% for both. The objective response rate for CTA+ F1L CDx+ patients was 72.2% in both cohorts. The median duration of response significantly differed between F1L CDx+ and F1L CDx- samples in ROS1-fp (5.6 vs. 17.3 months) but not NTRK-fp (9.2 vs. 12.9 months) patients. Fifteen acquired resistance mutations were detected. We conclude that F1L CDx is a clinically valid complement to tissue-based testing to identify patients who may benefit from entrectinib and those with acquired resistance mutations associated with disease progression.

Abstract P5-13-06: Exploratory biomarker analysis in VERONICA, a phase 2 study of venetoclax + fulvestrant versus fulvestrant in patients with estrogen receptor (ER)-positive HER2-negative metastatic breast cancer (mBC)

BACKGROUND: Venetoclax (VEN) is a potent and selective inhibitor of the anti-apoptotic protein, BCL2. Preclinical studies have implicated the BCL2 family members, BCLXL and MCL1, in VEN resistance, and clinical studies in hematological malignancies have demonstrated subgroups with high ratios of BCL2/BCLXL and BCL2/MCL1 have the greatest VEN antitumor activity. The randomized phase 2 VERONICA study (NCT03584009) evaluated VEN in combination with fulvestrant (F) vs F alone in ER-positive, HER2-negative MBC pts who experienced disease recurrence/progression during or after a CDK4/6 inhibitor. Previously reported results from VERONICA (Lindeman et al. ASCO 2021) did not show an improved clinical benefit rate or progression-free survival (PFS) with VEN+F vs F alone. Here we present exploratory biomarker analyses of the expression of BCL2 family members and genomic alterations in circulating tumor DNA (ctDNA) and association with clinical outcomes from VEN+F vs F. METHODS: Tumor specimens were obtained during screening from 103 patients enrolled in the study, and expression levels of BCL2, BCLXL and MCL1 were analyzed by IHC. Baseline plasma-derived ctDNA was evaluated using the FoundationOne® Liquid assay. Expression of BCL2, BCLXL, MCL1 and mutations in ctDNA were correlated with PFS from VEN+F vs F based on the primary analysis (cutoff: Aug 5, 2020). RESULTS: In the overall population, protein levels of BCL2, BCLXL and MCL1 were similar between the VEN+F vs F arms. Patients whose tumors were BCL2 3+ trended towards having the greatest difference in median (m) PFS (3.9 months [mo] in VEN+F vs 1.7 mo in F; hazard ratio [HR] 0.38 [95% CI 0.09, 1.62]) albeit in a small sample size (n=13). Similarly, subgroup analysis suggested a trend for increasing mPFS and improved HR in VEN+F vs F alone in patients with the lowest BCLXL expression. mPFS in patients with a BCL2/BCLXL ratio ≥1 was 3.7 mo for VEN+F vs 1.8 mo for F (HR 0.67 [95% CI 0.3-1.49]) whereas patients with a BCL2/BCLXL ratio &lt;1 had no difference in mPFS between the arms (2.0 mo in both arms, HR 1.21 [95% CI 0.7-2.1]). In the ctDNA-evaluable population, ESR1 (42.6%), TP53 (41.5%) and PIK3CA (35%) were the most prevalent genomic alterations observed and well-controlled between arms. PFS was similar between the ESR1 wildtype (wt) and mutant (mut) subgroups. TP53 mut status was a poor prognostic factor in both treatment arms. The PIK3CA wt subgroup had increased mPFS with VEN+F vs F alone (HR 0.66 [95% 0.38-1.17]) compared to PIK3CA mut (HR 1.59 [95% 0.74-3.34]). Patients with PIK3CA wt and BCL2 high tumors had the largest difference in mPFS between VEN+F (3.7 mo) vs F alone (1.9 mo) (HR 0.58 [95%CI 0.28-1.19]), compared to PIK3CA wt-BCL2 low tumors (2.4 vs 1.9 mo; HR 0.67 [95%CI 0.26-1.72]). CONCLUSION: Our data suggest that a high ratio of BCL2 to BCLXL conferred a trend towards a greater benefit to VEN+F compared to F alone, consistent with other clinical studies evaluating VEN. These analyses highlight the need to profile BCL2 and its family members to identify the VEN-sensitive subgroups, especially in indications where high expression of BCLXL or MCL1 may be observed. The ctDNA profile of VERONICA patients indicate a heavily pretreated patient population. The benefit observed in PIK3CA wt patients from VEN+F suggest increased dependence on BCL2 in this subgroup, while PIK3CA mut tumors likely rely on PI3K/AKT/mTOR survival programs or other BCL2 family members to evade apoptosis. Exploratory biomarker analyses are ongoing to further understand the VERONICA patient population.

Citation Format: Geoffrey J. Lindeman, Tharu M. Fernando, Rebecca Bowen, Ching-Wei Chang, Rupal Desai, Kushagra Gupta, Aulde Fléchais, Timothy R. Wilson, Aditya Bardia. Exploratory biomarker analysis in VERONICA, a phase 2 study of venetoclax + fulvestrant versus fulvestrant in patients with estrogen receptor (ER)-positive HER2-negative metastatic breast cancer (mBC) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-06.

NTRK gene fusions are detected in both secretory and non-secretory breast cancers

NTRK fusions represent a new biomarker-defined population that can be treated with TRK inhibitors. Although rare, NTRK fusions are detected across a wide range of solid tumors. Previous reports suggest that NTRK fusions are limited to the secretory subtype of breast cancer. Here we examined NTRK fusions in a large real world next-generation sequencing (NGS) dataset and confirmed secretory versus non-secretory status using H&E images. Of 23 NTRK fusion-positive cases, 11 were classified as secretory, 11 as non-secretory, and one as mixed status. The secretory subtype trended younger, was predominantly estrogen receptor (ER)-, had lower tumor mutational burden, and exhibited lower levels of genomic loss of heterozygosity. The non-secretory subtype was enriched for TP53 mutations. The secretory subtype was enriched for ETV6-NTRK3 fusions in 7 of 11 cases, and the non-secretory subtype had NTRK1 fusions in 7 of 11 cases, each with a different fusion partner. Our data suggests NTRK fusions are present in both secretory and non-secretory subtypes, and that comprehensive genomic profiling should be considered across all clinically advanced breast cancers to identify patients that could receive benefit from TRK inhibitors.

Electron Density Geometry and the Quantum Theory of Atoms in Molecules

A novel form of charge density analysis, that of isosurface curvature redistribution, is formulated and applied to the toy problem of carbonyl oxygen activation in formaldehyde. The isosurface representation of the electron charge density allows us to incorporate the rigorous geometric constraints of closed surfaces toward the analysis and chemical interpretation of the charge density response to perturbations. Visual inspection of 2D isosurface motion resulting from applied external electric fields reveals how the isosurface curvature flows within and between atoms and that a molecule can be uniquely and completely partitioned into chemically significant regions of positive and negative curvatures. These concepts reveal that carbonyl oxygen activation proceeds primarily through curvature and charge redistribution within rather than between Bader atoms. Using gradient bundle analysis─the partitioning of formaldehyde into infinitesimal volume elements bounded by QTAIM zero-flux surfaces─the observations from visual isosurface inspection are verified. The results of the formaldehyde carbonyl analysis are then shown to be transferable to the substrate carbonyl in the ketosteroid isomerase enzyme, laying the groundwork for extending this approach to the problems of enzymatic catalysis.

Principles Determining the Structure of Transition Metals

For the better part of a century researchers across disciplines have sought to explain the crystallography of the elemental transition metals: hexagonal close packed, body centered cubic, and face centered cubic in a form similar to that used to rationalize the structure of organic molecules and inorganic complexes. Pauling himself tried with limited success to address the origins of transition metal stability. These early investigators were handicapped, however, by incomplete knowledge regarding the structure of metallic electron density. Here, we exploit modern approaches to electron density analysis to first comprehensively describe transition metal electron density. Then, we use topological partitioning and quantum mechanically rigorous treatments of kinetic energy to account for the structure of the density as arising from the interactions between metallic polyhedra. We argue that the crystallography of the early transition metals results from charge transfer from the so called "octahedral" to "tetrahedral cages" while the face centered cubic structure of the late transition metals is a consequence of anti-bonding interactions that increase octahedral hole kinetic energy.

Updated Integrated Analysis of the Efficacy and Safety of Entrectinib in Locally Advanced or Metastatic ROS1 Fusion-Positive Non-Small-Cell Lung Cancer

Genetic rearrangements of the tyrosine receptor kinase ROS proto-oncogene 1 (ROS1) are oncogenic drivers in non-small-cell lung cancer (NSCLC). We report the results of an updated integrated analysis of three phase I or II clinical trials (ALKA-372-001, STARTRK-1, and STARTRK-2) of the ROS1 tyrosine kinase inhibitor, entrectinib, in ROS1 fusion–positive NSCLC.

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

PURPOSE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Double PIK3CA mutations in cis increase oncogenicity and sensitivity to PI3Kα inhibitors

Activating mutations in PIK3CA are frequent in human breast cancer, and phosphoinositide 3-kinase alpha (PI3Kα) inhibitors have been approved for therapy. To characterize determinants of sensitivity to these agents, we analyzed PIK3CA-mutant cancer genomes and observed the presence of multiple PIK3CA mutations in 12 to 15% of breast cancers and other tumor types, most of which (95%) are double mutations. Double PIK3CA mutations are in cis on the same allele and result in increased PI3K activity, enhanced downstream signaling, increased cell proliferation, and tumor growth. The biochemical mechanisms of dual mutations include increased disruption of p110α binding to the inhibitory subunit p85α, which relieves its catalytic inhibition, and increased p110α membrane lipid binding. Double PIK3CA mutations predict increased sensitivity to PI3Kα inhibitors compared with single-hotspot mutations.

Tumor-Infiltrating Lymphocytes in Patients Receiving Trastuzumab/Pertuzumab-Based Chemotherapy: A TRYPHAENA Substudy

Background

There is an urgent requirement to identify biomarkers to tailor treatment in human epidermal growth factor receptor 2 (HER2)-amplified early breast cancer treated with trastuzumab/pertuzumab-based chemotherapy.

Methods

Among the 225 patients randomly assigned to trastuzumab/pertuzumab concurrently or sequentially with an anthracycline-containing regimen or concurrently with an anthracycline-free regimen in the Tryphaena trial, we determined the percentage of tumor-infiltrating lymphocytes (TILs) at baseline in 213 patients, of which 126 demonstrated a pathological complete response (pCR; ypT0/is ypN0), with 28 demonstrating event-free survival (EFS) events. We investigated associations between baseline TIL percentage and either pCR or EFS after adjusting for clinicopathological characteristics using logistic and Cox regression models, respectively. To understand TIL biology, we evaluated associations between baseline TILs and baseline tumor gene expression data (800 gene set by NanoString) in a subset of 173 patients. All statistical tests were two-sided.

Results

Among the patients with measurable TILs at baseline, the median level was 14.1% (interquartile range = 7.1%-32.4%). After adjusting for clinicopathological characteristics, baseline percentage TIL was not associated with pCR (adjusted odds ratio [aOR] for every 10-percentage unit increase in TILs = 1.12, 95% confidence interval [CI] = 0.95 to 1.31, P = .17). At a median follow-up of 4.7 years, for every increase in baseline TILs of 10%, there was a 25% reduction in the hazard for an EFS event (aOR = 0.75, 95% CI = 0.56 to 1.00, P = .05) after adjusting for baseline clinicopathological characteristics and pCR. Additionally, genes associated with epithelial-mesenchymal transition, angiogenesis, and T-cell inhibition such as SNAIL1, ZEB1, NOTCH3, and B7-H3 were statistically significantly inversely correlated with percentage TIL.

Conclusions

Baseline TIL percentage provides independent prognostic information in patients treated with trastuzumab/pertuzumab-based neoadjuvant chemotherapy. However, further validation is required.

First-in-Human Phase I Study to Evaluate the Brain-Penetrant PI3K/mTOR Inhibitor GDC-0084 in Patients with Progressive or Recurrent High-Grade Glioma

PURPOSE

GDC-0084 is an oral, brain-penetrant small-molecule inhibitor of PI3K and mTOR. A first-in-human, phase I study was conducted in patients with recurrent high-grade glioma.

PATIENTS AND METHODS

GDC-0084 was administered orally, once daily, to evaluate safety, pharmacokinetics (PK), and activity. Fluorodeoxyglucose-PET (FDG-PET) was performed to measure metabolic responses.

RESULTS

Forty-seven heavily pretreated patients enrolled in eight cohorts (2-65 mg). Dose-limiting toxicities included 1 case of grade 2 bradycardia and grade 3 myocardial ischemia (15 mg), grade 3 stomatitis (45 mg), and 2 cases of grade 3 mucosal inflammation (65 mg); the MTD was 45 mg/day. GDC-0084 demonstrated linear and dose-proportional PK, with a half-life (∼19 hours) supportive of once-daily dosing. At 45 mg/day, steady-state concentrations exceeded preclinical target concentrations producing antitumor activity in xenograft models. FDG-PET in 7 of 27 patients (26%) showed metabolic partial response. At doses ≥45 mg/day, a trend toward decreased median standardized uptake value in normal brain was observed, suggesting central nervous system penetration of drug. In two resection specimens, GDC-0084 was detected at similar levels in tumor and brain tissue, with a brain tissue/tumor-to-plasma ratio of >1 and >0.5 for total and free drug, respectively. Best overall response was stable disease in 19 patients (40%) and progressive disease in 26 patients (55%); 2 patients (4%) were nonevaluable.

CONCLUSIONS

GDC-0084 demonstrated classic PI3K/mTOR-inhibitor related toxicities. FDG-PET and concentration data from brain tumor tissue suggest that GDC-0084 crossed the blood-brain barrier.

Observing the 3D Chemical Bond and its Energy Distribution in a Projected Space

Our curiosity-driven desire to "see" chemical bonds dates back at least one-hundred years, perhaps to antiquity. Sweeping improvements in the accuracy of measured and predicted electron charge densities, alongside our largely bondcentric understanding of molecules and materials, heighten this desire with means and significance. Here we present a method for analyzing chemical bonds and their energy distributions in a two-dimensional projected space called the condensed charge density. Bond "silhouettes" in the condensed charge density can be reverse-projected to reveal precise three-dimensional bonding regions we call bond bundles. We show that delocalized metallic bonds and organic covalent bonds alike can be objectively analyzed, the formation of bonds observed, and that the crystallographic structure of simple metals can be rationalized in terms of bond bundle structure. Our method also reproduces the expected results of organic chemistry, enabling the recontextualization of existing bond models from a charge density perspective.

Entrectinib in ROS1 fusion-positive non-small-cell lung cancer: integrated analysis of three phase 1-2 trials

BACKGROUND

Recurrent gene fusions, such as ROS1 fusions, are oncogenic drivers of various cancers, including non-small-cell lung cancer (NSCLC). Up to 36% of patients with ROS1 fusion-positive NSCLC have brain metastases at the diagnosis of advanced disease. Entrectinib is a ROS1 inhibitor that has been designed to effectively penetrate and remain in the CNS. We explored the use of entrectinib in patients with locally advanced or metastatic ROS1 fusion-positive NSCLC.

METHODS

We did an integrated analysis of three ongoing phase 1 or 2 trials of entrectinib (ALKA-372-001, STARTRK-1, and STARTRK-2). The efficacy-evaluable population included adult patients (aged ≥18 years) with locally advanced or metastatic ROS1 fusion-positive NSCLC who received entrectinib at a dose of at least 600 mg orally once per day, with at least 12 months' follow-up. All patients had an Eastern Cooperative Oncology Group performance status of 0-2, and previous cancer treatment (except for ROS1 inhibitors) was allowed. The primary endpoints were the proportion of patients with an objective response (complete or partial response according to Response Evaluation Criteria in Solid Tumors version 1.1) and duration of response, and were evaluated by blinded independent central review. The safety-evaluable population for the safety analysis included all patients with ROS1 fusion-positive NSCLC in the three trials who received at least one dose of entrectinib (irrespective of dose or duration of follow-up). These ongoing studies are registered with ClinicalTrials.gov, NCT02097810 (STARTRK-1) and NCT02568267 (STARTRK-2), and EudraCT, 2012-000148-88 (ALKA-372-001).

FINDINGS

Patients were enrolled in ALKA-372-001 from Oct 26, 2012, to March 27, 2018; in STARTRK-1 from Aug 7, 2014, to May 10, 2018; and in STARTRK-2 from Nov 19, 2015 (enrolment is ongoing). At the data cutoff date for this analysis (May 31, 2018), 41 (77%; 95% CI 64-88) of 53 patients in the efficacy-evaluable population had an objective response. Median follow-up was 15·5 monhts (IQR 13·4-20·2). Median duration of response was 24·6 months (95% CI 11·4-34·8). In the safety-evaluable population, 79 (59%) of 134 patients had grade 1 or 2 treatment-related adverse events. 46 (34%) of 134 patients had grade 3 or 4 treatment-related adverse events, with the most common being weight increase (ten [8%]) and neutropenia (five [4%]). 15 (11%) patients had serious treatment-related adverse events, the most common of which were nervous system disorders (four [3%]) and cardiac disorders (three [2%]). No treatment-related deaths occurred.

INTERPRETATION

Entrectinib is active with durable disease control in patients with ROS1 fusion-positive NSCLC, and is well tolerated with a manageable safety profile, making it amenable to long-term dosing in these patients. These data highlight the need to routinely test for ROS1 fusions to broaden therapeutic options for patients with ROS1 fusion-positive NSCLC.

FUNDING

Ignyta/F Hoffmann-La Roche.

Entrectinib in patients with advanced or metastatic NTRK fusion-positive solid tumours: integrated analysis of three phase 1-2 trials

BACKGROUND

Entrectinib is a potent inhibitor of tropomyosin receptor kinase (TRK) A, B, and C, which has been shown to have anti-tumour activity against NTRK gene fusion-positive solid tumours, including CNS activity due to its ability to penetrate the blood-brain barrier. We present an integrated efficacy and safety analysis of patients with metastatic or locally advanced solid tumours harbouring oncogenic NTRK1, NTRK2, and NTRK3 gene fusions treated in three ongoing, early-phase trials.

METHODS

An integrated database comprised the pivotal datasets of three, ongoing phase 1 or 2 clinical trials (ALKA-372-001, STARTRK-1, and STARTRK-2), which enrolled patients aged 18 years or older with metastatic or locally advanced NTRK fusion-positive solid tumours who received entrectinib orally at a dose of at least 600 mg once per day in a capsule. All patients had an Eastern Cooperative Oncology Group performance status of 0-2 and could have received previous anti-cancer therapy (except previous TRK inhibitors). The primary endpoints, the proportion of patients with an objective response and median duration of response, were evaluated by blinded independent central review in the efficacy-evaluable population (ie, patients with NTRK fusion-positive solid tumours who were TRK inhibitor-naive and had received at least one dose of entrectinib). Overall safety evaluable population included patients from STARTRK-1, STARTRK-2, ALKA-372-001, and STARTRK-NG (NCT02650401; treating young adult and paediatric patients [aged ≤21 years]), who received at least one dose of entrectinib, regardless of tumour type or gene rearrangement. NTRK fusion-positive safety evaluable population comprised all patients who have received at least one dose of entrectinib regardless of dose or follow-up. These ongoing studies are registered with ClinicalTrials.gov, NCT02097810 (STARTRK-1) and NCT02568267 (STARTRK-2), and EudraCT, 2012-000148-88 (ALKA-372-001).

FINDINGS

Patients were enrolled in ALKA-372-001 from Oct 26, 2012, to March 27, 2018; in STARTRK-1 from Aug 7, 2014, to May 10, 2018; and in STARTRK-2 from Nov 19, 2015 (enrolment is ongoing). At the data cutoff date for this analysis (May 31, 2018) the efficacy-evaluable population comprised 54 adults with advanced or metastatic NTRK fusion-positive solid tumours comprising ten different tumour types and 19 different histologies. Median follow-up was 12.9 months (IQR 8·77-18·76). 31 (57%; 95% CI 43·2-70·8) of 54 patients had an objective response, of which four (7%) were complete responses and 27 (50%) partial reponses. Median duration of response was 10 months (95% CI 7·1 to not estimable). The most common grade 3 or 4 treatment-related adverse events in both safety populations were increased weight (seven [10%] of 68 patients in the NTRK fusion-positive safety population and in 18 [5%] of 355 patients in the overall safety-evaluable population) and anaemia (8 [12%] and 16 [5%]). The most common serious treatment-related adverse events were nervous system disorders (three [4%] of 68 patients and ten [3%] of 355 patients). No treatment-related deaths occurred.

INTERPRETATION

Entrectinib induced durable and clinically meaningful responses in patients with NTRK fusion-positive solid tumours, and was well tolerated with a manageable safety profile. These results show that entrectinib is a safe and active treatment option for patients with NTRK fusion-positive solid tumours. These data highlight the need to routinely test for NTRK fusions to broaden the therapeutic options available for patients with NTRK fusion-positive solid tumours.

FUNDING

Ignyta/F Hoffmann-La Roche.

Quantum theory of atoms in molecules in condensed charge density space

By leveraging the fundamental doctrine of the quantum theory of atoms in molecules — the partitioning of the electron charge density (ρ) into regions bounded by surfaces of zero flux — we map the gradient field of ρ onto a two-dimensional space called the gradient bundle condensed charge density ([Formula: see text]). The topology of [Formula: see text] appears to correlate with regions of chemical significance in ρ. The bond wedge is defined as the image in ρ of the basin of attraction in [Formula: see text], analogous to the Bader atom, which is the basin of attraction in ρ. A bond bundle is defined as the union of bond wedges that share interatomic surfaces. We show that maxima in [Formula: see text] typically map to bond paths in ρ, though this is not necessarily always true. This observation addresses many of the concerns regarding the chemical significance of bond critical points and bond paths in the quantum theory of atoms in molecules.

Predictive and Pharmacodynamic Biomarkers of Response to the Phosphatidylinositol 3-Kinase Inhibitor Taselisib in Breast Cancer Preclinical Models

The PI3K signaling pathway serves as a central node in regulating cell survival, proliferation, and metabolism. PIK3CA, the gene encoding the PI3K catalytic subunit p110-alpha, is commonly altered in breast cancer resulting in the constitutive activation of the PI3K pathway. Using an unbiased cell line screening approach, we tested the sensitivity of breast cancer cell lines to taselisib, a potent PI3K inhibitor, and correlated sensitivity with key biomarkers (PIK3CA, HER2, PTEN, and ESR1). We further assessed how taselisib modulates downstream signaling in the different genomic backgrounds that occur within breast cancer. We found that sensitivity to taselisib correlated with the presence of PIK3CA mutations, but was independent of HER2 status. We further showed that HER2-amplified/PIK3CA wild-type cell lines are not as sensitive to taselisib when compared with HER2-amplified/PIK3CA-mutant cell lines. In a PIK3CA-mutant/PTEN null background, PI3K downstream signaling rebounded in the presence of taselisib correlating with decreased sensitivity at later time points. Finally, we observed that PIK3CA mutations cooccurred with mutations in the estrogen receptor (ER; ESR1) in metastatic tumors from patients with ER⁺ breast cancer. However, the cooccurrence of an ESR1 mutation with a PIK3CA mutation did not affect response to taselisib in a single agent setting or in combination with fulvestrant. In summary, these data suggest that development of taselisib in breast cancer should occur in a PIK3CA-mutant setting with cotreatments determined by the specific subtypes under investigation.

Neoadjuvant letrozole plus taselisib versus letrozole plus placebo in postmenopausal women with oestrogen receptor-positive, HER2-negative, early-stage breast cancer (LORELEI): a multicentre, randomised, double-blind, placebo-controlled, phase 2 trial

BACKGROUND

Endocrine therapy-based neoadjuvant treatment for luminal breast cancer allows efficient testing of new combinations before surgery. The activation of the phosphatidylinositol-3-kinase (PI3K) pathway is a known mechanism of resistance to endocrine therapy. Taselisib is an oral, selective PI3K inhibitor with enhanced activity against PIK3CA-mutant cancer cells. The LORELEI trial tested whether taselisib in combination with letrozole would result in an increased proportion of objective responses and pathological complete responses.

METHODS

In this multicentre, randomised, double-blind, parallel-cohort, placebo-controlled phase 2, study, we enrolled postmenopausal women (aged ≥18 years) with histologically confirmed, oestrogen receptor (ER)-positive, HER2-negative, stage I-III, operable breast cancer, from 85 hospitals in 22 countries worldwide. To be eligible, patients had have an Eastern Cooperative Oncology Group (ECOG) performance status 0-1, adequate organ function, and had to have evaluable tumour tissue for PIK3CA genotyping. Patients were randomly assigned (1:1) by means of a permuted block algorithm (block size of four) via an interactive voice or web-based response system, to receive letrozole (2·5 mg/day orally, continuously) with either 4 mg of oral taselisib or placebo (on a 5 days-on, 2 days-off schedule) for 16 weeks, followed by surgery. Randomisation was stratified by tumour size and nodal status. Site staff, patients, and the sponsor were masked to treatment assignment. Coprimary endpoints were the proportion of patients who achieved an objective response by centrally assessed breast MRI and a locally assessed pathological complete response in the breast and axilla (ypT0/Tis, ypN0) at surgery in all randomly assigned patients and in patients with PIK3CA-mutant tumours. Analyses were done in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT02273973, and is closed to accrual.

FINDINGS

Between Nov 12, 2014, and Aug 12, 2016, 334 participants were enrolled and randomly assigned to receive letrozole and placebo (n=168) or letrozole and taselisib (n=166). Median follow-up was 4·9 months (IQR 4·7-5·1). The study met one of its primary endpoints: the addition of taselisib to letrozole was associated with a higher proportion of patients achieving an objective response in all randomly assigned patients (66 [39%] of 168 patients in the placebo group vs 83 [50%] of 166 in the taselisib group; odds ratio [OR] 1·55, 95% CI 1·00-2·38; p=0·049) and in the PIK3CA-mutant subset (30 [38%] of 79 vs 41 [56%] of 73; OR 2·03, 95% CI 1·06-3·88; p=0·033). No significant differences were observed in pathological complete response between the two groups, either in the overall population (three [2%] of 166 in the taselisib group vs one [1%] of 168 in the placebo group; OR 3·07 [95% CI 0·32-29·85], p=0·37) or in the PIK3CA-mutant cohort (one patient [1%) vs none [0%]; OR not estimable, p=0·48). The most common grade 3-4 adverse events in the taselisib group were gastrointestinal (13 [8%] of 167 patients), infections (eight [5%]), and skin-subcutaneous tissue disorders (eight [5%]). In the placebo group, four (2%) of 167 patients had grade 3 or worse vascular disorders, two (1%) had gastrointestinal disorders, and two (1%) patients had grade 3 or worse infections and infestations. There was no grade 4 hyperglycaemia and grade 3 cases were asymptomatic. Serious adverse events were more common in the taselisib group (eight [5%] patients with infections and seven [4%] with gastrointestinal effects) than in the placebo group (one [1%] patient each with grade 3 postoperative wound and haematoma infection, grade 4 hypertensive encephalopathy, grade 3 acute cardiac failure, and grade 3 breast pain). One death occurred in the taselisib group, which was not considered to be treatment-related.

INTERPRETATION

The increase in the proportion of patients who achieved an objective response from the addition of taselisib to endocrine therapy in a neoadjuvant setting is consistent with the clinical benefit observed in hormone receptor-positive, HER2-negative, metastatic breast cancer.

FUNDING

Genentech and F Hoffmann-La Roche.

Malnutrition, nutritional interventions and clinical outcomes of patients with acute small bowel obstruction: results from a national, multicentre, prospective audit

OBJECTIVE

The aim of this study was to assess the nutritional status of patients presenting with small bowel obstruction (SBO), along with associated nutritional interventions and clinical outcomes.

DESIGN

Prospective cohort study.

SETTING

131 UK hospitals with acute surgical services.

PARTICIPANTS

2069 adult patients with a diagnosis of SBO were included in this study. The mean age was 67.0 years and 54.7% were female.

PRIMARY AND SECONDARY OUTCOME MEASURES

Primary outcome was in-hospital mortality. Secondary outcomes recorded included: major complications (composite of in-hospital mortality, reoperation, unplanned intensive care admission and 30-day readmission), complications arising from surgery (anastomotic leak, wound dehiscence), infection (pneumonia, surgical site infection, intra-abdominal infection, urinary tract infection, venous catheter infection), cardiac complications, venous thromboembolism and delirium.

RESULTS

Postoperative adhesions were the most common cause of SBO (49.1%). Early surgery (<24 hours postadmission) took place in 30.0% of patients, 22.0% underwent delayed operation and 47.9% were managed non-operatively. Malnutrition as stratified by Nutritional Risk Index was common, with 35.7% at moderate risk and 5.7% at severe risk of malnutrition. Dietitian review occurred in just 36.4% and 55.9% of the moderate and severe risk groups. In the low risk group, 30.3% received nutritional intervention compared with 40.7% in moderate risk group and 62.7% in severe risk group. In comparison to the low risk group, patients who were at severe or moderate risk of malnutrition had 4.2 and 2.4 times higher unadjusted risk of in-hospital mortality, respectively. Propensity-matched analysis found no difference in outcomes based on use or timing of parenteral nutrition.

CONCLUSIONS

Malnutrition on admission is associated with worse outcomes in patients with SBO, and marked variation in management of malnutrition was observed. Future trials should focus on identifying effective and cost-effective nutritional interventions in SBO.

Exploratory analysis of the effect of taselisib on downstream pathway modulation and correlation with tumor response in ER-positive/HER2-negative early-stage breast cancer from the LORELEI trial

1050

Background: Taselisib (T) is an oral, potent, selective inhibitor of Class I PI3-kinase with enhanced activity against PIK3CA mutant cancer cells. Results from the LORELEI trial have demonstrated a significant improvement in ORR (objective response rate) by centrally assessed magnetic resonance imaging in all randomized patients as well as in the PIK3CA mutant (MT) cohort treated with neoadjuvant T plus letrozole (L) compared to placebo (P) plus L. Here we present the results of exploratory analyses of selected pathway-related phosphoproteins. Methods: Baseline (BL) and week3 (W3) tumor biopsies were obtained from 334 patients enrolled in the trial. Phosphoproteins (pAKT, pPRAS40 and pS6) were analyzed by IHC. BL levels as well as changes from BL to W3 were correlated with response assessed either by ORR or cell cycle arrest (Ki67 at W3 < 2.7%). Results: In the overall population, BL phosphoproteins levels were similar between the T and P arms. Higher pAKT (p < 0.001) and pPRAS40 (p = 0.004) levels were observed in MT vs wild-type (WT), whereas the opposite result was found for pS6 (p = 0.03). Treatment-induced absolute changes of phosphoproteins adjusted for BL levels were not significantly different between the T and P arms in the overall population, except for pPRAS40 with higher decrease in the T arm (p = 0.014). After stratification for PIK3CA genotype, a significantly greater decrease in expression levels was observed for pPRAS40 (p < 0.001) and pS6 (p = 0.020) in MT tumors treated with T. The treatment effects were not significantly different in the WT population. A trend for an association between decrease in pS6 levels at W3 and improved ORR was observed in the MT (p = 0.08) and T (p = 0.09) subgroups. The magnitude of pS6 suppression at W3 was higher in tumors achieving a cell cycle arrest in the MT/T subgroup (biserial correlation = -0.473). Conclusions: Exploratory analyses of phosphoproteins showed bioactivity of taselisib as indicated by downstream pathway suppression. Translational research aiming to integrate these results with additional exploratory biomarkers data is currently ongoing. Clinical trial information: NCT02273973.

Abstract P2-08-02: Interaction of PIK3CA mutation subclasses with response to preoperative treatment with the PI3K inhibitor pictilisib in patients with estrogen receptor-positive breast cancer

Background: Although preclinical data suggest that combining PI3K inhibitors with endocrine therapy may overcome resistance, results from randomized clinical trials have failed to identify a subgroup of patients that derive a substantial benefit. This preoperative window study assessed whether adding the PI3K inhibitor pictilisib can increase the anti-tumor effects of anastrozole in primary breast cancer and aimed to identify the most appropriate patient population for combination therapy.

Methods: In this randomized, open-label, phase 2 study, 167 postmenopausal women with newly diagnosed, operable, ER-positive, HER2-negative breast cancers were recruited. Participants were randomly allocated (2:1, favoring the combination) to two-weeks of preoperative treatment with anastrozole 1 mg once daily or the combination of anastrozole 1mg with pictilisib 260 mg once daily. The primary endpoint was inhibition of tumor cell proliferation, as measured by change in Ki-67 protein expression between tumor samples taken before and at the end of treatment. Secondary endpoints include induction of apoptosis (Caspase3) and safety. Comprehensive biomarkers analyses included targeted NGS of a comprehensive cancer panel of &gt;400 genes (Ampliseq Comprehensive Cancer panel), copy number variation analyses, and pre- and post-treatment reverse-phase protein arrays (RPPA) and RNA profiling (NanoString nCounter platform).

Results:There was significantly greater geometric mean Ki67 suppression of 82.5% (90% CI, 78.3%-85.8%) for the combination vs 70.7% (61.0%-78.0%) for anastrozole [geometric mean ratio (combination/ anastrozole) 0.60 (0.58-0.85);p=0.01]. Higher baseline Ki67, Luminal B status and/or negative PR status were associated with increased benefit from adding pictilisib. A significant interaction was observed between PIK3CA mutation subtypes [helical domain mutations (HD), kinase domain mutations (KD), wildtype (WT)] and mean Ki67 suppression; the combination/anastrozole geometric mean ratio of Ki67 suppression was 0.48 (0.27-0.84; p=0.02) for patients with HD mutations and 0.63 (0.39–1.0; p=0.05) for patients with PIK3Ca WT, compared to 1.17 (0.57–2.41; p=0.64) for patients with KD mutations. This was largely due to patients with HD mutations showing a particularly poor response to anastrozole alone [mean Ki67 suppression 53.9% (9.5%-76.5%)], that was reversed by the addition of pictilisib [mean Ki-67 suppression 78.1% (71.0%-83.4%)]. On the other hand, patients with KD mutations responded well to anastrozole alone [mean Ki-67 suppression 77.7% (57.0%-88.4%)] and showed no benefit from the addition of pictilisib [mean Ki-67 suppression 73.9% (59.8%-83.0%)]. There was no significant difference in induction of apoptosis between treatment groups. Comprehensive pre- and post-treatment biomarkers analyses will be presented.

Conclusions: Adding pictilisib to anastrozole significantly increases the anti-proliferative response to preoperative treatment with anastrozole. A significant interaction was observed between PIK3CA mutation subtypes, with patients with helical domain mutations showing a particularly poor response to anastrozole alone that was reversed by the addition of pictilisib.

Citation Format: Schmid P, Pinder S, Wheatley D, Zummit C, Macaskill EJ, Hu J, Price R, Bundred N, Hadad S, Shia A, Sarker S-J, Lim L, Mousa K, O'Brien C, Wilson TR, Lackner MR, Gendreau S, Gazinska P, Korbie D, Trau M, Mainwaring P, Thompson A, Purushotham A. Interaction of PIK3CA mutation subclasses with response to preoperative treatment with the PI3K inhibitor pictilisib in patients with estrogen receptor-positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-08-02.

Current management of small bowel obstruction in the UK: results from the National Audit of Small Bowel Obstruction clinical practice survey

AIM

Small bowel obstruction (SBO) is associated with high rates of morbidity and mortality. The National Audit of Small Bowel Obstruction (NASBO) is a collaboration between trainees and specialty associations to improve the care of patients with SBO through national clinical audit. The aim of this study was to define current consultant practice preferences in the management of SBO in the UK.

METHOD

A survey was designed to assess practice preferences of consultant surgeons. The anonymous survey captured demographics, indications for surgery or conservative management, use of investigations including water-soluble contrast agents (WSCA), use of laparoscopy and nutritional support strategies. The questionnaire underwent two pilot rounds prior to dissemination via the NASBO network.

RESULTS

A total of 384 responses were received from 131 NASBO participating units (overall response rate 29.2%). Abdominal CT and serum urea and electrolytes were considered essential initial investigations by more than 80% of consultants. Consensus was demonstrated on indications for early surgery and conservative management. Three hundred and thirty-eight (88%) respondents would consider use of WSCA; of these, 328 (97.1%) would use it in adhesive SBO. Two hundred (52.1%) consultants considered a laparoscopic approach when operating for SBO. Oral nutritional supplements were favoured in operatively managed patients by 259 (67.4%) respondents compared with conservatively managed patients (186 respondents, 48.4%).

CONCLUSION

This survey demonstrates consensus on imaging requirements and indications for early surgery in the management of SBO. Significant variation exists around awareness of the need for nutritional support in patients with SBO, and on strategies to achieve this support.

Phase III study of taselisib (GDC-0032) + fulvestrant (FULV) v FULV in patients (pts) with estrogen receptor (ER)-positive, PIK3CA-mutant (MUT), locally advanced or metastatic breast cancer (MBC): Primary analysis from SANDPIPER

LBA1006

Background: Taselisib, a potent, selective PI3K inhibitor, has enhanced activity in PIK3CA-MUT BC cell lines and confirmed partial responses in PIK3CA-MUT BC as a single-agent or with FULV. We assessed taselisib + FULV in pts with ER-positive, HER2-negative, PIK3CA-MUT locally advanced or MBC. Methods: SANDPIPER (NCT02340221) is a double-blind, placebo (PBO)-controlled, randomized, phase III study. Postmenopausal pts with disease recurrence or progression during or after an aromatase inhibitor were randomized 2:1 to receive taselisib (4 mg oral, qd) or PBO + FULV (500 mg). Stratification factors were: visceral disease, endocrine sensitivity, and geographic region. Pts with PIK3CA-MUT tumors, assessed by central cobas PIK3CA Mutation Test, were randomized separately from non-MUT tumors. The primary endpoint was investigator-assessed progression-free survival (INV-PFS) in pts with PIK3CA-MUT tumors. Secondary endpoints included objective response rate (ORR), overall survival (OS), clinical benefit rate (CBR), duration of objective response (DoR), PFS by blinded independent central review (BICR-PFS), and safety. Results: 516 pts were randomized in the PIK3CA-MUT intention-to-treat (ITT) population. Efficacy is shown in the Table. Taselisib + FULV significantly improved INV-PFS (hazard ratio [HR] 0.70) as confirmed by BICR-PFS (HR 0.66). OS is immature. The most common grade ≥3 adverse events (AEs; preferred terms) in the taselisib + FULV arm in safety-evaluable pts who received ≥ 1 dose of treatment were diarrhea (12%), hyperglycemia (10%), colitis (3%), and stomatitis (2%). AEs led to more taselisib discontinuations (17% v 2%) and dose reductions (37% v 2%), v PBO. Conclusions: Taselisib + FULV significantly improved INV-PFS, v PBO + FULV, in pts with ER-positive, HER2-negative, PIK3CA-MUT locally advanced or MBC. The safety profile is largely consistent with previous studies. Clinical trial information: NCT02340221. [Table: see text]

Phase II Study of Taselisib (GDC-0032) in Combination with Fulvestrant in Patients with HER2-Negative, Hormone Receptor-Positive Advanced Breast Cancer

Purpose: This single-arm, open-label phase II study evaluated the safety and efficacy of taselisib (GDC-0032) plus fulvestrant in postmenopausal women with locally advanced or metastatic HER2-negative, hormone receptor (HR)-positive breast cancer.Patients and Methods: Patients received 6-mg oral taselisib capsules daily plus intramuscular fulvestrant (500 mg) until disease progression or unacceptable toxicity. Tumor tissue (if available) was centrally evaluated for PIK3CA mutations. Adverse events (AE) were recorded using NCI-CTCAE v4.0. Tumor response was investigator-determined using RECIST v1.1.Results: Median treatment duration was 4.6 (range: 0.9-40.5) months. All patients experienced ≥1 AE, 30 (50.0%) had grade ≥3 AEs, and 19 (31.7%) experienced 35 serious AEs. Forty-seven of 60 patients had evaluable tissue for central PIK3CA mutation testing [20 had mutations, 27 had no mutation detected (MND)]. In patients with baseline measurable disease, clinical activity was observed in tumors with PIK3CA mutations [best confirmed response rate: 38.5% (5/13; 95% CI, 13.9-68.4); clinical benefit rate (CBR): 38.5% (5/13; 95% CI, 13.9-68.4)], PIK3CA-MND [best confirmed response rate: 14.3% (3/21; 95% CI, 3.0-36.3); CBR: 23.8% (5/21; 95% CI, 8.2-47.2)], and unknown PIK3CA mutation status [best confirmed response rate: 20.0% (2/10; 95% CI, 2.5-55.6); CBR: 30.0% (3/10; 95% CI, 6.7-65.2)].Conclusions: Taselisib plus fulvestrant had clinical activity irrespective of PIK3CA mutation status, with numerically higher objective response rate and CBR in patients with PIK3CA-mutated (vs. -MND) locally advanced or metastatic HER2-negative, HR-positive breast cancer. No new safety signals were reported. A confirmatory phase III trial is ongoing. Clin Cancer Res; 24(18); 4380-7. ©2018 AACR.

Abstract PD5-04: Ki67 changes and PEPI score in the LORELEI trial: A phase II randomized, double-blind study of neoadjuvant letrozole plus taselisib versus letrozole plus placebo in postmenopausal women with ER-positive/HER2-negative early-stage breast cancer

Background: Taselisib is an oral, potent, selective inhibitor of Class I PI3-kinase (PI3K) alpha, gamma, and delta isoforms with enhanced activity against PIK3CA mutant cancer cells. LORELEI trial demonstrated a significant improvement in ORR (objective response rate) centrally assessed by MRI with neoadjuvant taselisib plus letrozole compared to letrozole plus placebo in all randomized patients as well as in the PIK3CA mutant cohort (Saura et al, ESMO 2017).

Methods: 334 postmenopausal women with newly diagnosed ER+/HER2-, untreated, Stage I-III operable breast cancer and evaluable tumor tissue for PIK3CA genotyping were randomized (1:1) to receive daily letrozole (2.5 mg) with either taselisib (4 mg on a 5 days on/ 2 days off schedule) or placebo for 16 weeks, followed by surgery. Tumor tissue collection was performed at baseline, week 3 (W3) and at surgery. Secondary objectives included, but were not restricted to, ORR assessed by MRI in patients with PIK3CA wild type (WT) tumors, ORR using alternative methods of tumor assessment (ultrasound, mammogram and clinical breast exam) in all patients and patients with PIK3CA mutant and WT tumors, central assessment of Ki67 at different timepoints (baseline, W3 and surgery), and the centrally derived PEPI score. Central Ki67 was assessed by two independent readers blinded to treatment arms and PIK3CA status (Vall D'Hebron Institute of Oncology, Barcelona).

Results: ORR by centrally assessed MRI was similar in the two treatment arms in patients with PIK3CA WT tumors (45.7 vs 40.4% for taselisib and placebo, respectively). ORR assessed by breast US was also significantly higher with taselisib compared to placebo in all randomized patients and in the PIK3CA mutant cohort. The highest concordance rate between MRI and other imaging modalities was found with breast ultrasound (53.7%). Centrally assessed Ki67 changes are reported in Table 1. Ki67 values decreased from baseline to W3 and from baseline to surgery in both treatment arms. No significant differences in the decrease of Ki67 values between treatment arms were detected. Unplanned analysis of Complete Cell Cycle Arrest (CCCA) at W3 was numerically higher with taselisib than with placebo in all randomized patients (49.6% vs 38.5%) and in the PIK3CA mutant cohort (60.9% vs 47.5%). Due to the variability in timing between the last dose of taselisib (median time 11 days; interquartile range 6-16 days) and tissue collection at surgery, considering the half-life of taselisib of approximately 40 hours, centrally derived PEPI score is not interpretable.

Ki67 proportional changes, %Taselisib + letrozolePlacebo + letrozoleBaseline to W3All patients-83.8-80.4PIK3CA mutant-84.5-79.1PIK3CA WT-82.8-81.1Baseline to surgeryAll patients-75.6-80.5PIK3CA mutant-71.9-79.9PIK3CA WT-78.2-81.2

Conclusion: Among the investigated alternative methods for assessing ORR, breast ultrasound performed similar to MRI. Decrease in the Ki67 values from baseline to W3 and to surgery were observed in both treatment arms. The time interval between taselisib cessation and tissue collection at surgery are being further investigated.

Clinical trial information: NCT02273973

Citation Format: de Azambuja E, Saura C, Nuciforo P, Frantal S, Oliveira M, Zardavas D, Jallitsch-Halper A, de la Pena L, Dubsky P, Lombard JM, Vuylsteke P, Castaneda Altamirano C, Sanchez C, Ballestrero A, Colleoni M, Santos Borges G, Ciruelos E, Bardia A, Fornier M, Boer K, Wilson TR, Stout TJ, Hsu JY, Shi Y, Piccart M, Baselga J, Gnant M. Ki67 changes and PEPI score in the LORELEI trial: A phase II randomized, double-blind study of neoadjuvant letrozole plus taselisib versus letrozole plus placebo in postmenopausal women with ER-positive/HER2-negative early-stage breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD5-04.

Somatic mutation, copy number and transcriptomic profiles of primary and matched metastatic estrogen receptor-positive breast cancers

BACKGROUND

Estrogen receptor-positive (ER+) breast cancers (BCs) constitute the most frequent BC subtype. The molecular landscape of ER+ relapsed disease is not well characterized. In this study, we aimed to describe the genomic evolution between primary (P) and matched metastatic (M) ER+ BCs after failure of adjuvant therapy.

MATERIALS AND METHODS

A total of 182 ER+ metastatic BC patients with long-term follow-up were identified from a single institution. P tumor tissue was available for all patients, with 88 having matched M material. According to the availability of tumor material, samples were characterized using a 120 mutational hotspot qPCR, a 29 gene copy number aberrations (CNA) and a 400 gene expression panels. ESR1 mutations were assayed by droplet digital PCR. Molecular alterations were correlated with overall survival (OS) using the Cox proportional hazards regression models.

RESULTS

The median follow-up was 6.4 years (range 0.5-26.6 years). Genomic analysis of P tumors revealed somatic mutations in PIK3CA, KRAS, AKT1, FGFR3, HRAS and BRAF at frequencies of 41%, 6%, 5%, 2%, 1% and 2%, respectively, and CN amplification of CCND1, ZNF703, FGFR1, RSF1 and PAK1 at 23%, 19%, 17%, 12% and 11%, respectively. Mutations and CN amplifications were largely concordant between P and matched M (>84%). ESR1 mutations were found in 10.8% of the M but none of the P. Thirteen genes, among which ESR1, FOXA1, and HIF1A, showed significant differential expression between P and M. In P, the differential expression of 18 genes, among which IDO1, was significantly associated with OS (FDR < 0.1).

CONCLUSIONS

Despite the large concordance between P and matched M for the evaluated molecular alterations, potential actionable targets such as ESR1 mutations were found only in M. This supports the importance of characterizing the M disease. Other targets we identified, such as HIF1A and IDO1, warrant further investigation in this patient population.

UK-based, multisite, prospective cohort study of small bowel obstruction in acute surgical services: National Audit of Small Bowel Obstruction (NASBO) protocol

INTRODUCTION

Small bowel obstruction (SBO) is a common indication for emergency laparotomy in the UK, which is associated with a 90-day mortality rate of 13%. There are currently no UK clinical guidelines for the management of this condition. The aim of this multicentre prospective cohort study is to describe the burden, variation in management and associated outcomes of SBO in the UK adult population.

METHODS AND ANALYSIS

UK hospitals providing emergency general surgery are eligible to participate. This study has three components: (1) a clinical preference questionnaire to be completed by consultants providing emergency general surgical care to assesses preferences in diagnostics and therapeutic approaches, including laparoscopy and nutritional interventions; (2) site resource profile questionnaire to indicate ease of access to diagnostic services, operating theatres, nutritional support teams and postoperative support including intensive care; (3) prospective cohort study of all cases of SBO admitted during an 8-week period at participating trusts. Data on diagnostics, operative and nutritional interventions, and in-hospital mortality and morbidity will be captured, followed by data validation.

ETHICS AND DISSEMINATION

This will be conducted as a national audit of practice in conjunction with trainee research collaboratives, with support from patient representatives, surgeons, anaesthetists, gastroenterologists and a clinical trials unit. Site-specific reports will be provided to each participant site as well as an overall report to be disseminated through specialist societies. Results will be published in a formal project report endorsed by stakeholders, and in peer-reviewed scientific reports. Key findings will be debated at a focused national meeting with a view to quality improvement initiatives.

Abstract 1780: Identifying preclinical predictive biomarkers to taselisib in breast cancer cell lines

The phosphoinositol-3-kinase (PI3K) signaling pathway is one of the most frequently activated pathways in cancer, and controls critical cellular processes such as proliferation, transcription and survival. Taselisib (GDC0032) is an orally bioavailable, potent, and selective inhibitor of Class I PI3K alpha, delta, and gamma isoforms, with 30fold less inhibition of the PI3K beta isoform relative to the PI3K alpha isoform. Previously published data demonstrated that taselisib has increased activity against PIK3CA mutant cancer cell lines (Ndubaku CO et al, J Med Chem, 2013).

A panel of 50 breast cancer cell lines were profiled for sensitivity to taselisib using viability assays and subsequently correlated with PIK3CA mutations and expression of ER, PR, HER2 and PTEN. The PIK3CA mutant cell lines displayed an average of 30-fold greater sensitivity in IC50 compared to the PIK3CA wild-type cell lines. PTEN null cell lines were largely refractory to taselisib. Within the PIK3CA wild-type cell lines, the HER2 amplified cells showed an average of 18-fold greater sensitivity in IC50 over the HER2 wild-type cell lines. No differences in taselisib sensitivity were seen between the kinase, helical, or the C2 domain of the PIK3CA gene within the PIK3CA mutant cell lines. In HER2 amplified PIK3CA wild-type cell lines, taselisib did not fully suppress pAKT and pS6 signaling, however full suppression was observed in combination with the HER2 inhibitor, lapatinib. Increased apoptosis was observed with the combination of taselisib and lapatinib in the HER2 amplified, PIK3CA mutant cells, but not in HER2 amplified, PIK3CA wild-type cells. In PIK3CA mutant luminal cell lines, taselisib induced ESR1 transcriptional activity, but not in PIK3CA wild-type luminal lines, as assessed using PR, GREB1 and IGFBP4 gene expression. This induction was ER- and estradiol-dependent, and was suppressed using the estrogen degrader, fulvestrant. Lastly, as up to 40% of ER+, second line PIK3CA mutant metastatic tumors have been shown to harbor a mutation in the ESR1 gene (Spoerke JM et al., Nat Commun, 2016), we assessed the crosstalk between the PI3K and ER pathways in PIK3CA mutant MCF-7 cells that overexpress two ESR1 hotspot mutations. These ESR1 mutant cell lines displayed increased ER transcriptional activity, which was further activated by taselisib, an observation that was reversed with fulvestrant co-treatment. These data suggest that the combination of taselisib and an estrogen degrader can suppress crosstalk between PI3K and ER in both an ESR1 mutant and wild-type background, and supports the ongoing SANDPIPER study of taselisib in combination with fulvestrant in metastatic ER+, PIK3CA mutant cancers that have progressed following an aromatase inhibitor therapy (NCT02340221).

Citation Format: Heidi M. Savage, Heather M. Moore, Carol L. O'Brien, Wei Zhou, Ciara Metcalfe, Mark R. Lackner, Timothy R. Wilson. Identifying preclinical predictive biomarkers to taselisib in breast cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1780. doi:10.1158/1538-7445.AM2017-1780

SANDPIPER: Phase III study of the PI3-kinase (PI3K) inhibitor taselisib (GDC-0032) plus fulvestrant in patients (pts) with estrogen receptor (ER)-positive, HER2-negative locally advanced or metastatic breast cancer (BC) enriched for pts with PIK3CA-mutant tumors

TPS1119

Background: As one of the most frequent genomic alterations in BC, PIK3CA mutations occur in ~40% of ER-positive, HER2-negative breast tumors. PIK3CA mutations may mediate resistance to endocrine therapies and promote growth and proliferation of tumors in BC. Taselisib is a potent and selective PI3K inhibitor that preferentially degrades mutant versus wild-type PI3Kα via a unique mechanism not seen with alpelisib and pictilisib. In PIK3CA-mutant BC cell lines, taselisib had enhanced activity. Confirmed partial responses were reported in pts with PIK3CA-mutant BC treated with taselisib either as a single agent or in combination with fulvestrant. Methods: SANDPIPER is a double-blind, placebo-controlled, randomized, phase III study, designed to evaluate the efficacy and safety of taselisib plus fulvestrant in pts with ER-positive, HER2-negative, PIK3CA-mutant locally advanced or metastatic BC. Postmenopausal pts will be randomized 2:1 to receive either taselisib (4 mg qd) or placebo in combination with fulvestrant (500 mg intramuscular on Days 1 and 15 of Cycle 1, and on Day 1 of each subsequent 28-day cycle). Pts must have had disease recurrence or progression during or after aromatase inhibitor treatment. Randomization will be stratified by visceral disease, endocrine sensitivity, and geographic region. SANDPIPER enriches for pts with PIK3CA-mutant tumors and a centrally assessed, valid cobas PIK3CA Mutation Test result in tumor tissue is required prior to enrollment; pts with PIK3CA-mutant tumors are randomized separately from those with non-mutant tumors. The primary efficacy endpoint is investigator-assessed progression-free survival in pts with PIK3CA-mutant tumors (estimated by Kaplan–Meier methodology). Other endpoints include overall survival, objective response rate, clinical benefit rate, duration of objective response, safety, pharmacokinetics, and patient-reported outcomes. Enrollment is open for pts with PIK3CA-mutant tumors. Target enrollment is 600 pts and > 300 patients have been enrolled. Clinical trial information: NCT02340221.

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

Taselisib is a potent and selective tumor growth inhibitor through PI3K pathway suppression. Thirty-four patients with locally advanced or metastatic solid tumors were treated (phase I study, modified 3+3 dose escalation; 5 cohorts; 3-16 mg taselisib once-daily capsule). Taselisib pharmacokinetics were dose-proportional; mean half-life was 40 hours. Frequent dose-dependent, treatment-related adverse events included diarrhea, hyperglycemia, decreased appetite, nausea, rash, stomatitis, and vomiting. At 12 and 16 mg dose levels, dose-limiting toxicities (DLT) were observed, with an accumulation of higher-grade adverse events after the cycle 1 DLT assessment window. Pharmacodynamic findings showed pathway inhibition at ≥3 mg in patient tumor samples, consistent with preclinical PIK3CA-mutant tumor xenograft models. Confirmed response rate was 36% for PIK3CA-mutant tumor patients with measurable disease [5/14: 4 breast cancer (3 patients at 12 mg); 1 non-small cell lung cancer], where responses started at 3 mg, and 0% in patients with tumors without known PIK3CA hotspot mutations (0/15).Significance: Preliminary data consistent with preclinical data indicate increased antitumor activity of taselisib in patients with PIK3CA-mutant tumors (in comparison with patients with tumors without known activating PIK3CA hotspot mutations) starting at the lowest dose tested of 3 mg, thereby supporting higher potency for taselisib against PIK3CA-mutant tumors. Cancer Discov; 7(7); 704-15. ©2017 AACR.See related commentary by Rodon and Tabernero, p. 666This article is highlighted in the In This Issue feature, p. 653.