Abstract P1-13-11: Neratinib in the extended adjuvant treatment of patients from Asia with early-stage HER2+ breast cancer after trastuzumab-based therapy: Exploratory analyses from the phase III ExteNET trial

Background: Current breast cancer knowledge is based largely on studies conducted in western populations. Their findings may not be generalizable to Asian women because of ethnic, genetic and lifestyle differences. Neratinib (N) is an irreversible tyrosine kinase inhibitor of HER1, 2 and 4. The international, randomized, placebo (P)-controlled phase III ExteNET trial showed that 1 year (yr) of N after trastuzumab (T)-based adjuvant therapy significantly improved 2-yr invasive disease-free survival (iDFS) in patients (pts) with early-stage HER2+ breast cancer (HR 0.67; 95% CI 0.50–0.91; p=0.009) [Chan et al. Lancet Oncol 2016]. The significant iDFS benefit with N was shown to be durable after 5 yrs' follow-up (HR 0.73; 95% CI 0.57-0.92; p=0.008) [Martin et al. ESMO 2017]. We report efficacy and safety findings from pts enrolled from Asian centers (China, Hong Kong, Japan, Korea, Malaysia, Singapore, and Taiwan) on the ExteNET trial to better characterize the effects of N in Asian women.

Methods: Pts with early-stage HER2+ breast cancer were randomly assigned to oral N 240 mg/day or P for 1 yr after standard primary therapy and T-based adjuvant therapy. Antidiarrheal prophylaxis was not required by protocol. Data concerning disease recurrences were collected prospectively during yr 1-2 post-randomization, and from medical records during yr 3–5 post-randomization. Primary endpoint: iDFS. HR (95% CI) estimated using Cox proportional-hazards models stratified by nodal status, hormone-receptor status and prior T regimen. Data cut-off: 2-yr analysis, July 2014; 5-yr analysis, March 2017. Clinicaltrials.gov:NCT00878709.

Results: Of 2840 randomized pts (N, n=1420; P, n=1420), 341 (12%) were enrolled from Asian centers (N, n=165; P, n=176). Baseline characteristics: median age 53 yr; hormone receptor-positive 48%. Median treatment duration was similar in both groups (N, 351 days; P, 352 days). iDFS events in Asian vs ITT populations are shown in the Table.

 Primary 2-yr analysisa5-yr analysis NPNPAsian population, n165176165176iDFS events, n10151222HR (95% CI)b0.71 (0.31-1.57)0.54 (0.26-1.08)P-value (2-sided)0.4040.085ITT population, n1420142014201420iDFS events, n67106116163HR (95% CI)b0.66 (0.49-0.90)0.73 (0.57-0.92)P-value (2-sided)0.0080.008a. Primary study endpoint; b. Neratinib vs placebo

The incidence of grade 3/4 diarrhea with N was slightly higher in Asian pts (46.1% vs ITT, 39.8%). All other grade 3/4 adverse events with N were rare among Asian pts (elevated ALT, mucosal inflammation, 2 pts each; other events, 1 pt each). Compliance with N in Asian pts was also improved (71% vs ITT, 61%).

Conclusions: In Asian pts enrolled into ExteNET, compliance with N was better and the magnitude of N effect was similar or greater that that observed in the ITT population. Although N-related grade 3/4 diarrhea was more common in Asian pts than in the ITT population, all other grade 3/4 events were rare. Despite small pt numbers, our analyses suggest that the findings from ExteNET are applicable to Asian pts, and support the conclusion that N reduces disease recurrences in Asian pts with early-stage HER2+ breast cancer after T-based adjuvant therapy.

Citation Format: Iwata H, Masuda N, Kim S-B, Inoue K, Rai Y, Fujita T, Shen Z-Z, Chiu JW, Ohtani S, Takahashi M, Yamamoto N, Miyaki T, Sun Q, Yen-Shen L, Xu B, Yap YS, Bustam AZ, Lee JR, Zhang B, Bryce R, Chan A. Neratinib in the extended adjuvant treatment of patients from Asia with early-stage HER2+ breast cancer after trastuzumab-based therapy: Exploratory analyses from the phase III ExteNET trial [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 P1-13-11.

Abstract P1-13-08: Extended adjuvant neratinib/fulvestrant blocks ER/HER2 crosstalk and maintains complete responses of ER+/HER2+ tumors following treatment with chemotherapy and anti-HER2 therapy

Background: Neratinib is a potent, irreversible pan-HER tyrosine kinase inhibitor. The phase III trial ExteNET showed improved disease-free survival in patients (pts) with HER2+ breast cancer treated with neratinib vs placebo after trastuzumab-based adjuvant therapy. The benefit from neratinib appeared to be greater in pts with ER+ tumors. Thus, we sought to elucidate mechanisms that may explain the benefit from extended adjuvant therapy with neratinib in pts with ER+/HER2+ breast cancer using a human-in-mouse model that simulates the clinical outcomes seen in ExteNET.

Results: Mice with established ER+/HER2 amplified MDA-361 tumors were treated with trastuzumab (tz) + paclitaxel (pac) for 4 weeks, and then randomized to fulvestrant (fulv) ± neratinib for 4 weeks. All MDA-361 tumors exhibited a prompt and marked reduction in volume after tz/pac treatment; 10 mice achieved a complete response (CR) before receiving 'extended adjuvant' therapy with fulv (n=5) or neratinib/fulv (n=5). A CR was maintained with neratinib/fulv following tz/pac. However, mice treated with fulv alone, relapsed rapidly (p<0.05 at week 8) despite of a complete downregulation of tumor ER levels. In a second experiment, nude mice with established MDA-361 xenografts were treated with pertuzumab/tz/pac for 4 weeks. Following a CR, mice were randomized to neratinib/fulv vs. fulv. Again, mice treated with neratinib/fulv maintained a CR, while mice in the fulv alone arm exhibited tumor progressions within a week. In three ER+/HER2+ cell lines (MDA-361, BT474 and UACC893) but not in ER+/HER– MCF7 cells, treatment with neratinib induced ER reporter transcriptional activity whereas treatment with fulv resulted in an increase in HER2 phosphorylation, suggesting compensatory crosstalk between the ER and HER2 pathways. To further understand the molecular basis of this crosstalk, MDA-361 tumor-bearing mice were treated with either fulv, neratinib or the combination for 7 days, after which tumors were harvested and analyzed using a Nanostring breast cancer ER panel consisting of 196 ER-regulated genes. Compared to vehicle or fulv-treated tumors, tumors treated with neratinib alone and neratinib/fulv showed marked downregulation of cyclin D1 mRNA expression. Similarly, in MDA-361, BT474 and UACC893 cells but not in MCF7 cells, only neratinib/fulv downregulated cyclin D1, P-AKT and P-ERK. Finally, treatment with neratinib/fulv but not fulv alone reduced cyclin D1 transcriptional reporter activity and cyclin D1 protein levels, and induced cell cycle arrest, suggesting double blockade is required to overcome compensatory crosstalk between ER and amplified HER2.

Conclusions: Neratinib/fulv but not fulv alone maintained complete responses of ER+/HER+ tumors following treatment with tz/pac or pertuzumab/tz/pac, reminiscent of the results in ExteNET. Neratinib treatment promoted ER transcriptional activity whereas ER downregulation with fulv was associated with increased HER2 signaling. In ER+/HER2+ breast cancer cells and tumors, neratinib/fulv synergistically inhibited growth, cyclin D1 expression, and AKT and MAPK activation, thus providing a plausible mechanism to explain the results in the ExteNET trial.

Citation Format: Sudhan DR, Schwarz LJ, Guerrero-Zotano AL, Nixon M, Formisano L, Croessmann S, Gonzalez Ericsson PI, Sanders ME, Balko JM, Avogadri-Connors F, Cutler RE, Lalani AS, Bryce R, Auerbach A, Arteaga CL. Extended adjuvant neratinib/fulvestrant blocks ER/HER2 crosstalk and maintains complete responses of ER+/HER2+ tumors following treatment with chemotherapy and anti-HER2 therapy [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 P1-13-08.

Neratinib after trastuzumab-based adjuvant therapy in HER2-positive breast cancer (ExteNET): 5-year analysis of a randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

ExteNET showed that 1 year of neratinib, an irreversible pan-HER tyrosine kinase inhibitor, significantly improves 2-year invasive disease-free survival after trastuzumab-based adjuvant therapy in women with HER2-positive breast cancer. We report updated efficacy outcomes from a protocol-defined 5-year follow-up sensitivity analysis and long-term toxicity findings.

METHODS

In this ongoing randomised, double-blind, placebo-controlled, phase 3 trial, eligible women aged 18 years or older (≥20 years in Japan) with stage 1-3c (modified to stage 2-3c in February, 2010) operable breast cancer, who had completed neoadjuvant and adjuvant chemotherapy plus trastuzumab with no evidence of disease recurrence or metastatic disease at study entry. Patients who were eligible patients were randomly assigned (1:1) via permuted blocks stratified according to hormone receptor status (hormone receptor-positive vs hormone receptor-negative), nodal status (0 vs 1-3 vs or ≥4 positive nodes), and trastuzumab adjuvant regimen (given sequentially vs concurrently with chemotherapy), then implemented centrally via an interactive voice and web-response system, to receive 1 year of oral neratinib 240 mg/day or matching placebo. Treatment was given continuously for 1 year, unless disease recurrence or new breast cancer, intolerable adverse events, or consent withdrawal occurred. Patients, investigators, and trial funder were masked to treatment allocation. The predefined endpoint of the 5-year analysis was invasive disease-free survival, analysed by intention to treat. ExteNET is registered with ClinicalTrials.gov, number NCT00878709, and is closed to new participants.

FINDINGS

Between July 9, 2009, and Oct 24, 2011, 2840 eligible women with early HER2-positive breast cancer were recruited from community-based and academic institutions in 40 countries and randomly assigned to receive neratinib (n=1420) or placebo (n=1420). After a median follow-up of 5·2 years (IQR 2·1-5·3), patients in the neratinib group had significantly fewer invasive disease-free survival events than those in the placebo group (116 vs 163 events; stratified hazard ratio 0·73, 95% CI 0·57-0·92, p=0·0083). The 5-year invasive disease-free survival was 90·2% (95% CI 88·3-91·8) in the neratinib group and 87·7% (85·7-89·4) in the placebo group. Without diarrhoea prophylaxis, the most common grade 3-4 adverse events in the neratinib group, compared with the placebo group, were diarrhoea (561 [40%] grade 3 and one [<1%] grade 4 with neratinib vs 23 [2%] grade 3 with placebo), vomiting (grade 3: 47 [3%] vs five [<1%]), and nausea (grade 3: 26 [2%] vs two [<1%]). Treatment-emergent serious adverse events occurred in 103 (7%) women in the neratinib group and 85 (6%) women in the placebo group. No evidence of increased risk of long-term toxicity or long-term adverse consequences of neratinib-associated diarrhoea were identified with neratinib compared with placebo.

INTERPRETATION

At the 5-year follow-up, 1 year of extended adjuvant therapy with neratinib, administered after chemotherapy and trastuzumab, significantly reduced the proportion of clinically relevant breast cancer relapses-ie, those that might lead to death, such as distant and locoregional relapses outside the preserved breast-without increasing the risk of long-term toxicity. An analysis of overall survival is planned after 248 events.

FUNDING

Wyeth, Pfizer, and Puma Biotechnology.

Neratinib Efficacy and Circulating Tumor DNA Detection of HER2 Mutations in HER2 Nonamplified Metastatic Breast Cancer

Purpose: Based on promising preclinical data, we conducted a single-arm phase II trial to assess the clinical benefit rate (CBR) of neratinib, defined as complete/partial response (CR/PR) or stable disease (SD) ≥24 weeks, in HER2^mut nonamplified metastatic breast cancer (MBC). Secondary endpoints included progression-free survival (PFS), toxicity, and circulating tumor DNA (ctDNA) HER2^mut detection.Experimental Design: Tumor tissue positive for HER2^mut was required for eligibility. Neratinib was administered 240 mg daily with prophylactic loperamide. ctDNA sequencing was performed retrospectively for 54 patients (14 positive and 40 negative for tumor HER2^mut).Results: Nine of 381 tumors (2.4%) sequenced centrally harbored HER2^mut (lobular 7.8% vs. ductal 1.6%; P = 0.026). Thirteen additional HER2^mut cases were identified locally. Twenty-one of these 22 HER2^mut cases were estrogen receptor positive. Sixteen patients [median age 58 (31-74) years and three (2-10) prior metastatic regimens] received neratinib. The CBR was 31% [90% confidence interval (CI), 13%-55%], including one CR, one PR, and three SD ≥24 weeks. Median PFS was 16 (90% CI, 8-31) weeks. Diarrhea (grade 2, 44%; grade 3, 25%) was the most common adverse event. Baseline ctDNA sequencing identified the same HER2^mut in 11 of 14 tumor-positive cases (sensitivity, 79%; 90% CI, 53%-94%) and correctly assigned 32 of 32 informative negative cases (specificity, 100%; 90% CI, 91%-100%). In addition, ctDNA HER2^mut variant allele frequency decreased in nine of 11 paired samples at week 4, followed by an increase upon progression.Conclusions: Neratinib is active in HER2^mut, nonamplified MBC. ctDNA sequencing offers a noninvasive strategy to identify patients with HER2^mut cancers for clinical trial participation. Clin Cancer Res; 23(19); 5687-95. ©2017 AACR.

Abstract CT011: Circulating tumor DNA (ctDNA) sequencing for HER2 mutation (HER2mut) screening and response monitoring to neratinib in metastatic breast cancer (MBC)

Introduction: MutHER is a phase II trial that demonstrated the anti-tumor activity of the pan-HER inhibitor neratinib in HER2mut, non-amplified MBC. The major challenges to accrue to this trial were the large number of pts to screen for the 2-3% HER2mut population and the high rate (24%) of poor quality tumor DNA for sequencing. The goals of this ctDNA study were: 1) the concordance of HER2mut detected by ctDNA versus tumor testing; 2) the incidence of ctDNA HER2mut in HER2 non-amplified MBC; 3) changes in HER2mut variant allele frequency (VAF) on neratinib therapy.

Methods: A sample size of 30 negative (neg) controls was needed to ensure 90% confidence if ctDNA testing has &gt;90% specificity in detecting HER2mut. Thus, plasma from MBC pts obtained at screening for MutHER trial (Neg control: 40 pts without HER2mut on tumor testing; Positive (pos) control: 14 pts with known HER2mut who received neratinib) were subjected to Guardant360 ctDNA 70-gene panel sequencing (all exons of HER2 included). ctDNA from the 14 neratinib treated pts were also analyzed at week (wk) 4 and upon progression. ctDNA data from MBC pts clinically tested at Guardant Health were interrogated for HER2mut incidence.

Results: Among the 14 pts with tumor pos for HER2mut, ctDNA sequencing identified the same HER2mut in 11, discrepant HER2mut in 1, and neg in 2. The 2 pts with ctDNA neg for HER2mut had progressive disease (PD) and stable disease (SD &gt; 6 months) on neratinib, respectively. Among the 40 neg controls, 8 were not evaluable (no detectable ctDNA or assay unsuccessful) and all 32 successfully sequenced cases were neg for HER2mut. The sensitivity and specificity of ctDNA for HER2mut detection was 11/14 (79%, 90% CI: 53-94%) and 32/32 (100%, 90% CI: 91-100%), respectively. Among the 11 paired baseline and wk 4 samples, 9 (82%) had lower HER2mut VAFs at wk 4 than at baseline, with 1 complete response (CR), 1 partial response (PR), 5 SD, and 4 PD at wk 8 as best tumor response. Two pts had higher wk 4 ctDNA HER2mut VAFs and both had radiographic PD at wk 8. The absolute HER2mut VAF levels at wk 4 were significantly associated with TTP (Spearman rho=-0.69, p=0.02) and tumor size change (rho=0.67, p=0.05). The HER2mut VAFs were significantly higher at progression than wk 4 in all pts (p&lt;0.01). One pt acquired a new HER2mut T798I, which is analogous to the gate-keeper mutation EGFR T790M. The incidence of HER2mut without amplification in unselected consecutive MBC clinically tested by Guardant360 was 3% (48/1,584), with mutation pattern similar to published tumor testing data.

Conclusions: ctDNA sequencing is sensitive and highly specific in detecting HER2mut, offering a non-invasive method to identify pts for trials of HER2mut-targeted therapy. Decreased HER2mut VAFs at wk 4 was observed in 82% of cases, consistent with the on-target effect of neratinib. Increased HER2mut VAFs at wk 4 is a potential early marker of progression.

Citation Format: Cynthia Ma, Ron Bose, Feng Gao, Rachel Freedman, Melinda Telli, Gretchen Kimmick, Eric Winer, Michael Naughton, Matthew Goetz, Christy Russell, Debu Tripathy, Melody Cobleigh, Andres Forero, Timothy Pluard, Carey Anders, Shana Thomas, Jill Anderson, Caroline Bumb, Kimberly Banks, Richard Lanman, Richard Bryce, Alshad Lalani, John Pfeifer, Daniel Hays, Mark Pegram, Kimberly Blackwell, Philippe Bedard, Hussam Al-Kateb, Matthew Ellis. Circulating tumor DNA (ctDNA) sequencing for HER2 mutation (HER2mut) screening and response monitoring to neratinib in metastatic breast cancer (MBC) [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 CT011. doi:10.1158/1538-7445.AM2017-CT011

Participation in a farmers' market fruit and vegetable prescription program at a federally qualified health center improves hemoglobin A1C in low income uncontrolled diabetics

Fruit and vegetable prescription programs have been shown to increase consumption of fresh produce, but whether they have an impact on medical outcomes is unknown. The purpose of this study was to examine the role of participation in a farmers' market and fruit and vegetable prescription program on changes in hemoglobin A1C (HbA1C), blood pressure (BP) and weight in patients with uncontrolled type 2 diabetes at a federally qualified health center (FQHC) in Detroit, MI.

The 13-week Fresh Prescription program (June 2015–October 2015) was designed to improve access and consumption of produce among low-income patients with uncontrolled type 2 diabetes. The program allotted up to $40 ($10 per week for up to four weeks) for purchase of produce from a FQHC located farmers' market. Adult, non-pregnant patients with a history of type 2 diabetes that had an elevated HbA1C > 6.5 within three months before Fresh Prescription program were eligible to participate. HgA1c, BP and weight were collected within three months of program start and within three months of completion.

There were 65 eligible participants with complete biometric data. A statistically significant (p = 0.001) decrease in HbA1C was found (9.54% to 8.83%). However, weight (208.3 lbs. to 209.0 lbs.) and BP (135.1/79.3 mm Hg to 135.8/77.6 mm Hg) did not change from pre- to post-study (p > 0.05).

Access to a fruit and vegetable prescription program over a 13-week period led to decreased HbA1C concentrations in uncontrolled type 2 diabetic patients living in an urban area of predominately-lower socioeconomic status.

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We evaluated efficacy of a fruit and vegetable prescription program.

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To date, there has been no research investigating the quantitative health benefits.

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A significant decrease in hemoglobin A1C was found in diabetics after program.

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There was no change in weight and blood pressure.

Neratinib Plus Paclitaxel vs Trastuzumab Plus Paclitaxel in Previously Untreated Metastatic ERBB2-Positive Breast Cancer: The NEfERT-T Randomized Clinical Trial

Importance

Efficacious ERBB2 (formerly HER2 or HER2/neu)-directed treatments, in addition to trastuzumab and lapatinib, are needed.

Objective

To determine whether neratinib, an irreversible pan-ERBB tyrosine kinase inhibitor, plus paclitaxel improves progression-free survival compared with trastuzumab plus paclitaxel in the first-line treatment of recurrent and/or metastatic ERBB2-positive breast cancer.

Design, Setting, and Participants

In the randomized, controlled, open-label NEfERT-T trial conducted from August 2009 to December 2014 at 188 centers in 34 countries in Europe, Asia, Africa, and North America, 479 women with previously untreated recurrent and/or metastatic ERBB2-positive breast cancer were randomized to 1 of 2 treatment arms (neratinib-paclitaxel [n = 242] or trastuzumab-paclitaxel [n = 237]). Women with asymptomatic central nervous system metastases were eligible, and randomization was stratified by prior trastuzumab and lapatinib exposure, hormone-receptor status, and region.

Interventions

Women received neratinib (240 mg/d orally) or trastuzumab (4 mg/kg then 2 mg/kg weekly), each combined with paclitaxel (80 mg/m2 on days 1, 8, and 15 every 28 days). Primary prophylaxis for diarrhea was not mandatory.

Main Outcome and Measures

The primary outcome was progression-free survival. Secondary end points were response rate, clinical benefit rate, duration of response, frequency, and time to symptomatic and/or progressive central nervous system lesions, and safety.

Results

The intent-to-treat population comprised 479 women 18 years or older (neratinib-paclitaxel, n = 242; trastuzumab-paclitaxel, n = 237) randomized and stratified in their respective treatment arms by prior trastuzumab and lapatinib exposure, hormone-receptor status, and region. Median progression-free survival was 12.9 months (95% CI, 11.1-14.9) with neratinib-paclitaxel and 12.9 months (95% CI, 11.1-14.8) with trastuzumab-paclitaxel (hazard ratio [HR], 1.02; 95% CI, 0.81-1.27; P =.89). With neratinib-paclitaxel, the incidence of central nervous system recurrences was lower (relative risk, 0.48; 95% CI, 0.29-0.79; P = .002) and time to central nervous system metastases delayed (HR, 0.45; 95% CI, 0.26-0.78; P = .004). Common grade 3 to 4 adverse events were diarrhea (73 of 240 patients [30.4%] with neratinib-paclitaxel and 9 of 234 patients [3.8%] with trastuzumab-paclitaxel), neutropenia (31 patients [12.9%] vs 34 patients [14.5%]) and leukopenia (19 patients [7.9%] vs 25 patients [10.7%]); no grade 4 diarrhea was observed.

Conclusions and Relevance

In first-line ERBB2-positive metastatic breast cancer, neratinib-paclitaxel was not superior to trastuzumab-paclitaxel in terms of progression-free survival. In spite of similar overall efficacy, neratinib-paclitaxel may delay the onset and reduce the frequency of central nervous system progression, a finding that requires a larger study to confirm.

Trial Registration

clinicaltrials.gov Identifier: NCT00915018.

Neratinib after trastuzumab-based adjuvant therapy in patients with HER2-positive breast cancer (ExteNET): a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

Neratinib, an irreversible tyrosine-kinase inhibitor of HER1, HER2, and HER4, has clinical activity in patients with HER2-positive metastatic breast cancer. We aimed to investigate the efficacy and safety of 12 months of neratinib after trastuzumab-based adjuvant therapy in patients with early-stage HER2-positive breast cancer.

METHODS

We did this multicentre, randomised, double-blind, placebo-controlled, phase 3 trial at 495 centres in Europe, Asia, Australia, New Zealand, and North and South America. Eligible women (aged ≥18 years, or ≥20 years in Japan) had stage 1-3 HER2-positive breast cancer and had completed neoadjuvant and adjuvant trastuzumab therapy up to 2 years before randomisation. Inclusion criteria were amended on Feb 25, 2010, to include patients with stage 2-3 HER2-positive breast cancer who had completed trastuzumab therapy up to 1 year previously. Patients were randomly assigned (1:1) to receive oral neratinib 240 mg per day or matching placebo. The randomisation sequence was generated with permuted blocks stratified by hormone receptor status (hormone receptor-positive [oestrogen or progesterone receptor-positive or both] vs hormone receptor-negative [oestrogen and progesterone receptor-negative]), nodal status (0, 1-3, or ≥4), and trastuzumab adjuvant regimen (sequentially vs concurrently with chemotherapy), then implemented centrally via an interactive voice and web-response system. Patients, investigators, and trial sponsors were masked to treatment allocation. The primary outcome was invasive disease-free survival, as defined in the original protocol, at 2 years after randomisation. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00878709.

FINDINGS

Between July 9, 2009, and Oct 24, 2011, we randomly assigned 2840 women to receive neratinib (n=1420) or placebo (n=1420). Median follow-up time was 24 months (IQR 20-25) in the neratinib group and 24 months (22-25) in the placebo group. At 2 year follow-up, 70 invasive disease-free survival events had occurred in patients in the neratinib group versus 109 events in those in the placebo group (stratified hazard ratio 0·67, 95% CI 0·50-0·91; p=0·0091). The 2-year invasive disease-free survival rate was 93·9% (95% CI 92·4-95·2) in the neratinib group and 91·6% (90·0-93·0) in the placebo group. The most common grade 3-4 adverse events in patients in the neratinib group were diarrhoea (grade 3, n=561 [40%] and grade 4, n=1 [<1%] vs grade 3, n=23 [2%] in the placebo group), vomiting (grade 3, n=47 [3%] vs n=5 [<1%]), and nausea (grade 3, n=26 [2%] vs n=2 [<1%]). QT prolongation occurred in 49 (3%) patients given neratinib and 93 (7%) patients given placebo, and decreases in left ventricular ejection fraction (≥grade 2) in 19 (1%) and 15 (1%) patients, respectively. We recorded serious adverse events in 103 (7%) patients in the neratinib group and 85 (6%) patients in the placebo group. Seven (<1%) deaths (four patients in the neratinib group and three patients in the placebo group) unrelated to disease progression occurred after study drug discontinuation. The causes of death in the neratinib group were unknown (n=2), a second primary brain tumour (n=1), and acute myeloid leukaemia (n=1), and in the placebo group were a brain haemorrhage (n=1), myocardial infarction (n=1), and gastric cancer (n=1). None of the deaths were attributed to study treatment in either group.

INTERPRETATION

Neratinib for 12 months significantly improved 2-year invasive disease-free survival when given after chemotherapy and trastuzumab-based adjuvant therapy to women with HER2-positive breast cancer. Longer follow-up is needed to ensure that the improvement in breast cancer outcome is maintained.

FUNDING

Wyeth, Pfizer, Puma Biotechnology.

Invasive disease-free survival benefit following neratinib as extended adjuvant therapy in centrally-confirmed HER2+ early-stage breast cancer: The ExteNET phase III randomized placebo-controlled trial

117

Background: Neratinib is an irreversible pan-HER tyrosine kinase inhibitor with clinical efficacy in trastuzumab pre-treated HER2-positive (HER2+) metastatic breast cancer (BC). ExteNET is an ongoing multicenter randomized placebo-controlled phase III trial evaluating the efficacy and safety of a 1-year course of neratinib in patients with early-stage HER2+ BC after trastuzumab-based adjuvant therapy (clinicaltrials.gov: NCT00878709). Methods: Women with locally-confirmed early-stage HER2+ BC were randomly assigned to oral neratinib 240mg/day or matching placebo for 1 year. Archived diagnostic tumor samples were submitted for HER2 gene amplification testing at a central laboratory. Primary endpoint: invasive disease-free survival (iDFS). Secondary endpoints: DFS including ductal carcinoma in situ (DFS+DCIS); distant disease-free survival (DDFS); time to distant recurrence (TDR). Stratified Cox proportional-hazards models were used to estimate hazard ratios (HR) for the ITT and amended ITT (aITT) populations; unstratified models were used for the centrally confirmed HER2 population. Treatment groups were compared using 2-sided log-rank tests. Results: The ITT population included 2840 patients (neratinib, N=1420; placebo, N=1420). The higher-risk aITT population (i.e. node-positive disease and randomized ≤1 year of completing prior trastuzumab) included 1873 patients (neratinib, N=938; placebo, N=935). Of the tumor samples analyzed, 1463 (86%) were centrally confirmed (neratinib, N=741; placebo, N=722). Conclusions: Neratinib significantly improves iDFS in trastuzumab-treated early-stage HER2+ BC patients. An enhanced treatment effect is observed with neratinib in women with centrally confirmed HER2+ tumors. Clinical trial information: NCT00878709. [Table: see text]

Use of multicriteria decision analysis to address conservation conflicts

Conservation conflicts are increasing on a global scale and instruments for reconciling competing interests are urgently needed. Multicriteria decision analysis (MCDA) is a structured, decision-support process that can facilitate dialogue between groups with differing interests and incorporate human and environmental dimensions of conflict. MCDA is a structured and transparent method of breaking down complex problems and incorporating multiple objectives. The value of this process for addressing major challenges in conservation conflict management is that MCDA helps in setting realistic goals; entails a transparent decision-making process; and addresses mistrust, differing world views, cross-scale issues, patchy or contested information, and inflexible legislative tools. Overall we believe MCDA provides a valuable decision-support tool, particularly for increasing awareness of the effects of particular values and choices for working toward negotiated compromise, although an awareness of the effect of methodological choices and the limitations of the method is vital before applying it in conflict situations.

Randomized phase II study of neratinib with or without temsirolimus in patients (pts) with non-small cell lung cancer (NSCLC) carrying HER2-activating mutations

TPS8124

Background: Recent advances in NSCLC have highlighted the importance of identifying mutations in driver oncogenes (eg EGFR, ALK) and the use of targeted agents to treat genetically-defined pt populations. HER2 (ERBB2) is a member of the ERBB receptor tyrosine kinase (TK) family which, once activated, stimulates several downstream effector pathways including PI3K, MAPK and JAK/STAT. Activating HER2 mutations are documented in approx 2–4% of pts with NSCLC and occur independently of EGFR, KRAS, NRAS and BRAF mutations. The efficacy of single-agent neratinib in HER2-mutated NSCLC is currently unknown; however, in vivo studies suggest that dual inhibition with an irreversible TK inhibitor (TKI) and an mTOR inhibitor is a promising therapeutic approach for HER2-mutated NSCLC [Perera et al. PNAS 2009]. This concept has been supported recently by a phase I study of neratinib, an irreversible pan-ERBB TKI, plus temsirolimus, which showed tumor regression in 5/6 evaluable pts with HER2-mutated NSCLC [Gandhi et al. WCLC, Amsterdam, Netherlands, 2011]. Methods: This international, randomized, open-label phase II study includes pts with previously treated stage IIIB/IV NSCLC and HER2-activating mutations. Pts are randomized 1:1 to oral neratinib 240mg od continuously ± IV temsirolimus 8mg/w (dose escalation to 15mg/w after one 4w cycle if tolerated). The addition of temsirolimus is permitted in pts assigned to neratinib monotherapy after progression. Tumor evaluations will be conducted every 8w. The primary endpoint is overall response rate (RECIST 1.1). Secondary endpoints are: clinical benefit rate; response duration; progression-free and overall survival; safety; health outcomes. Exploratory analyses include: correlative studies between tumor and plasma biomarkers and outcomes; pharmacokinetics. The trial has an optimal 2-stage design. Sample size (13–52 pts/arm) is based on a null response rate of 0.09, an alternative response rate of 0.25, power of 80% and 0.05 type I error rate. Both arms will be compared independently against historical controls. Enrollment is scheduled to open in March 2013. EudraCT identifier: 2012-004743-68. Clinical trial information: 2012-004743-68.

Design and rationale of FOCUS (PX-171-011): a randomized, open-label, phase 3 study of carfilzomib versus best supportive care regimen in patients with relapsed and refractory multiple myeloma (R/R MM)

Background

Carfilzomib is a next-generation proteasome inhibitor with single-agent activity in patients with relapsed and refractory multiple myeloma (R/R MM). In PX-171-003-A1, a single-arm phase 2 study of carfilzomib monotherapy in heavily pretreated patients, the overall response rate was 23.7%, 37% of patients achieved ≥ minimal response and median overall survival (OS) was 15.6 months. Based on this study, carfilzomib was recently approved by the US Food and Drug Administration for the treatment of R/R MM. Herein we describe the trial design and rationale for a phase 3 randomized study, FOCUS (CarFilzOmib for AdvanCed Refractory MUltiple Myeloma European Study), being conducted to compare OS after treatment with single-agent carfilzomib to best supportive care (BSC) regimen in R/R MM.

Methods

Patients must have received ≥3 prior regimens, must be responsive to at least 1 line of therapy, and be refractory to their most recent therapy. Eligible patients are randomized 1:1 to receive either carfilzomib (28-day cycles at 20 mg/m² IV on Days 1–2 of Cycle 1, escalating to 27 mg/m² IV on Days 8, 9, 15, and 16 and continuing at 27 mg/m² through Cycle 9 and Days 1, 2, 15, and 16 ≥ Cycle 10) or an active BSC regimen (corticosteroid treatment of prednisolone 30 mg, dexamethasone 6 mg, or equivalent every other day with optional cyclophosphamide 50 mg PO once daily). Patients will continue treatment until disease progression, unacceptable toxicity, or treatment discontinuation and will then enter long-term follow-up for survival. The primary endpoint is OS and secondary endpoints include progression-free survival, overall response rate, and safety. Disease assessments will be determined according to the International Myeloma Working Group Uniform Response Criteria with minimal response per European Blood and Marrow Transplantation Group criteria.

Conclusions

This phase 3 trial will provide more rigorous data for carfilzomib, as this is the first carfilzomib study with OS as the primary endpoint and will not be confounded by crossover and will provide more robust secondary response and safety results that will add to the data set from prior phase 2 studies. FOCUS will facilitate regulatory approvals around the world and expand treatment options for patients with R/R MM.

Trial registration

EudraCT No. 2009-016840-38; NCT01302392.

Abstract 3713: Inhibition of NQO2 by imidozoacridinones, including C1311 (Symadex, NSC645809): Implications for their mechanism of action

INTRODUCTION: Imidazoacridinones (IAs) have well documented anti-tumour activity in vitro and in vivo. They are thought to act as intercalating agents and inhibitors of topoisomerase II. More recently C1311 and other IAs have been shown to act as inhibitors of receptor tyrosine kinases such as FLT3 (J Clin Oncol 2008. Vol 26(15S) 2576). We have recently demonstrated that a structurally related series of triazoloacridinones can act as potent inhibitors of the oxidoreductases NQO1 and NQO2 (Bioorg Med Chem, 2009. In Press). Consequently, we conducted a computational substructure screen of the NCI chemical database to identify compounds with an IA scaffold. Here we describe these compounds, as novel inhibitors of NQO2, with low nanomolar potency. Moreover, some of these agents are up to 50-fold more efficient than the standard inhibitor, resveratrol.

EXPERIMENTAL: Compounds were evaluated spectrophotometrically for their ability to inhibit human NQO2 using NRH and DCPIP as co-substrates. Inhibitory potency (IC50) was related to computational binding affinity in order to derive potential structure/activity relationships. Toxicity was assessed in HCT116 cells (measured as the concentration required to reduce proliferation by 50%) using the MTT assay. The capacity of the compounds to interact with DNA was measured by changes in DNA melting temperature. Intercalative properties were confirmed by ethidium bromide displacement in SDS-PAGE gel electrophoresis

RESULTS: Seventeen compounds were evaluated for inhibitory potency which ranged from 6 to 1000nM. IC50 values were correlated with computationally derived binding affinities with a correlation coefficient of 0.93. However, the 200 fold difference in NQO2 inhibitory potency was not associated with any major change in toxicity which ranged from 460 to 3000nM. All compounds (at 10μM) were able to increase the melting temperature of calf thymus DNA in low salt solution. Changes in Tm ranged from 4.5 to 9oC and correlated well with ethidium bromide displacement. Though, as previously reported for IAs (Biochem Pharma, 2002. Vol 63, 1653), no obvious relationship could be determined between toxicity and Tm or the ability to displace ethidium bromide from DNA.

CONCLUSION: We have identified IAs as novel inhibitors of NQO2, with some in the series being the most potent inhibitors yet reported. Therefore, these agents could have applications in processes, such as inflammation, where NQO2 may be important. Furthermore, one of the IAs in the series is C1311 (IC50 = 148nM), an agent currently in clinical trial. It has been reported that tyrosine kinase inhibitors, such as imatinib, can also interact with NQO2 (BMC Struct Biol, 2009. Vol 9(7) 1472) and this may compromise drug action. Hence, when reviewing the activity of C1311, the cellular content of NQO2 should be considered since drug/enzyme interactions could influence overall activity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3713.

Gamma-Linolenic acid regulates the expression and secretion of SPARC in human cancer cells

SPARC (secreted protein acidic and rich in cystein), also known as osteonectin and BM40, is a secreted glycoprotein. It confers matrix adhesion of cells including cancer cells, thus promoting cell migration. SPARC has been shown to be involved in the aggressive nature of cancer. The current study investigated the role of a n-6 polyunsaturated fatty acid, gamma linolenic acid (GLA) on the expression and secretion of SPARC from cancer cells. Human breast cancer cell line MCF-7 and MDA-MB-231, human colon cancer cells HT115 and HRT-18 were used in the study. Cancer cells were treated with GLA or other fatty acids over a range of concentrations. Presence of SPARC in the supernatant and in the cell lysate were analysed using Western blotting. Cellular SPARC was also assessed using immunocytochemistry. SPARC transcript in these cells were studied using RT-PCR. Cell-matrix adhesion was determined using a cell-matrix adhesion assay and cell migration analysis. Treatment of MDA-MB-231 and HT115 cells with GLA, at non-toxic levels, resulted in reduction of SPARC in supernatant as well as in the cell lysate. In contrast, there were little changes in the supernatant SPARC in MCF-7 and in HRT-18 cells. Cellular SPARC, as revealed by immunocytochemistry, also demonstrated a similar trend of changes as seen with protein blotting. Analysis of the SPARC transcript using RT-PCR has shown an up-regulation of SPARC mRNA by the fatty acid. GLA reduced cell-matrix adhesion in these cancer cells. It is concluded that GLA is a regulator of SPARC secretion and expression in cancer cells. It reduces the secretion of SPARC into surrounding environment, which may contribute to the reduction of cancer cells adhesion to the extracellular matrix and cell motility.

Increased levels of SPARC (osteonectin) in human breast cancer tissues and its association with clinical outcomes

SPARC (secreted protein acidic and rich in cystein), also known as osteonectin and BM40, is a 32 kDa secreted glycoprotein that interacts with extracellular matrix (ECM) proteins to promote adhesion of cells from the matrix, thereby inducing a biological state conducive to cell migration. SPARC is also thought to play an important role in tissue remodelling, angiogenesis, embryonic development and tumourigenesis. The current study set out to examine both the transcript levels of SPARC and the presence of the molecule in breast cancer tissue and to demonstrate if a link existed between the levels of SPARC and the clinical outcome. Breast tumour tissues (n=120) and non-neoplastic mammary tissues (n=32) were studied. Protein levels of SPARC were assessed using immunohistochemistry. Transcript levels of SPARC were analysed using RT-PCR. The levels were correlated with nodal status, grade, prognosis and long-term survival (10 years). Transcript levels of SPARC were found to be significantly higher in tumour tissue when compared to normal background breast tissue. This fact was mirrored when comparing levels of SPARC in ductal tumours with levels in lobular and other types of tumour. A high level of SPARC was also found in Grade 3 and TNM2 and TNM4 tumours. Node-positive tumours also exhibited higher levels of SPARC than node-negative tumours . It was also noted that SPARC was present in high levels in NPI 2 and NPI 3 tumours. Over a 6 year follow-up, high levels of SPARC was seen to be significantly associated with the overall survival of the patients (P=0.0198). However, there was no significant correlation with disease-free survival. It is concluded that SPARC plays a crucial role in tumour development in breast cancer and as such has a significant bearing on patient prognosis and long-term survival.

Randomized, dose-finding phase III study of lithium gamolenate in patients with advanced pancreatic adenocarcinoma

BACKGROUND

Chemotherapy for pancreatic cancer offers small survival benefits and considerable side-effects. Unsaturated fatty acids have an antitumour effect in experimental studies; in phase II studies few side-effects were seen.

METHODS

In this group-sequential, open-label, randomized study, 278 patients with a diagnosis of inoperable pancreatic cancer were treated with either oral (700 mg daily for 15 days), low-dose (0.28 g/kg) or high-dose (0.84 g/kg) intravenous lithium gamolenate (LiGLA). The primary endpoint was survival time from randomization using Kaplan-Meier estimates.

RESULTS

Median survival after oral and low-dose intravenous treatment was 129 and 121 days respectively. Median survival after high-dose intravenous treatment was 94 days. A good Karnofsky score and the absence of metastases were associated with increased survival. Haemolysis, a marker of rapid infusion, was associated with a median survival time of 249 days in the low-dose intravenous group.

CONCLUSION

Oral or low-dose intravenous LiGLA led to survival times similar to those of other treatments for pancreatic cancer although one subgroup (low-dose intravenous LiGLA with haemolysis) had longer survival. High-dose intravenous treatment appeared to have an adverse effect. Systemic treatment with LiGLA cannot be recommended for the treatment of pancreatic cancer.

The effect of fatty acids and analogues upon intracellular levels of doxorubicin in cells displaying P-glycoprotein mediated multidrug resistance

Multidrug resistance mediated by overexpression of P-glycoprotein (P-gp) is a major obstacle in the chemotherapeutic management of cancer. The objectives of the current work were to examine if fatty acids affect the intracellular transport and dynamics of doxorubicin in drug-resistant cancer cell lines, and to assess if such effects were mediated through modulation of P-gp efflux pump activity. Among the range of fatty acids tested in this study, eicosapentaenoic acid diester (EPADI) increased doxorubicin accumulation [A] to 137% and retention [R] to 212% in doxorubicin-resistant MCF-7/ADR breast carcinoma cells, and [A] to 147% and [R] to 163% in vinblastine-resistant KBVI nasopharyngeal carcinoma cells. Consistent with EPADI-induced increases in intracellular doxorubicin concentrations, EPADI (10 microg/ml) sensitized MCF-7/ADR cells to the cytotoxic effects of doxorubicin (1 microg/ml) as assessed by MTT assay (viability < 50% of control), while EPADI itself displayed no cytotoxicity. The combination of EPADI (10 microg/ml) with verapamil (1 microM) resulted in a considerable increase in the [A] and [R] of the model P-gp substrate rhodamine-123 within drug-resistant cells compared to when either agent were used alone. KBV1 cells treated with combination of EPADI (10 microg/ml) and verapamil (1 microM) achieved 160% and 1120% greater [A] and [R] of rhodamine-123, respectively, compared to untreated cells. The P-gp modulatory effects of EPADI either alone, or as part of a combination with more potent inhibitors, should be further investigated.

Cytotoxic effects of two gamma linoleic salts (lithium gammalinolenate or meglumine gammalinolenate) alone or associated with a nitrosourea: an experimental study on human glioblastoma cell lines

Gamma linoleic acid (GLA) salts may exert a direct antiproliferative activity on tumor cells. The cytotoxicity is linked to the generation of conjugated dienes, peroxyl radicals and superoxide radicals. Lithium gammalinolenate (LiGLA) and meglumine gammalinolenate (MeGLA) have been recently developed for enhancing the water solubility of these compounds. MeGLA or LiGLA (10(-5) to 10(-4) mol/l) and fotemustine (Fote) (2 x 10(-6) to 2 x 10(-4) mol/l) were applied, alone or in combination, for up to 9 days to two human glioblastoma cell lines A172 and U373MG. Fote was applied first followed by LiGLA and/or MeGLA. Cytotoxicity was evaluated by the MTT test, and the effects of drug combinations were analyzed by the isobolographic representation according to the Chou and Talalay method (combination indexes). For both GLA salts, cytotoxicity was manifested after 4 days of cell exposure and with very sharp dose-response curves. Comparison of IC50 values indicated that MeGLA was more active than LiGLA. There was a constant reduction in IC50 values following an increase in exposure time for A172 cells: between 4 and 9 days of cell exposure, IC50 changed from 73 to 46 microM for LiGLA and from 49 to 31 microM for MeGLA (p<0.05). With U373MG cells, there was no influence of exposure duration on IC50 values. Combination index values indicated that association between Fote and GLA salts globally resulted in slightly antagonistic effects. These results may be useful for further development of GLA salts at the clinical level.

Calcium supplementation in nulliparous women for the prevention of pregnancy-induced hypertension, preeclampsia and preterm birth: an Australian randomized trial. FRACOG and the ACT Study Group

A multicentre, randomized controlled double-blind trial in 5 maternity hospitals in Australia assessed the effect of a daily supplement of calcium (1.8g oral calcium or an oral placebo) taken daily until delivery, from less than 24 weeks' gestation, on the frequency of pregnancy-induced hypertension, preeclampsia and preterm birth (< 37 weeks' gestation) in 456 nulliparas with a singleton pregnancy. Treatment with calcium reduced the risk of preeclampsia (relative risk 0.44 [95% CI, 0.21-0.90], p = 0.02) and the risk of preterm birth (relative risk 0.44 [95% CI, 0.21-0.90], p = 0.02). No significant differences were seen between the 2 groups in the frequency of pregnancy-induced hypertension, although the study only had statistical power to detect large differences in this outcome. An updated systematic review of the 9 randomized trials of calcium supplementation in pregnancy shows a significant reduction in the risk of hypertension and preeclampsia although no effect on preterm birth. Calcium supplementation during pregnancy reduced the risk of preeclampsia and preterm birth in this nulliparous population. The available evidence for systematic review of all the randomized trials of calcium supplementation shows benefit in reducing the risk of hypertension and preeclampsia.

Inhibition of membrane ruffling and ezrin translocation by gamma linolenic acid

Membrane ruffling of a tumour cell is correlated with its motile and metastatic behaviour. This study examined the effect of gamma linolenic acid (GLA), an anti-cancer agent, on HGF/SF induced membrane ruffling in the human cancer cell line, HT115. HGF induced a rapid appearance of membrane ruffling which was related to increased motility and the tyrosine phosphorylation and translocation of ezrin, a membrane-cytoskeleton linker protein. The presence of GLA significantly inhibited both the membrane ruffling and cell motility of the tumour cells, at sub-toxic concentrations. Western blotting revealed that the tyrosine phosphorylation of ezrin was inhibited by GLA. The translocation ezrin from cytosol and generalised areas of cell membrane to ruffled areas of the membrane induced by HGF/SF was also inhibited as shown by both indirect immunofluorescence and transmission electron microscopy. It is concluded that GLA inhibits HGF/SF induced membrane ruffling via its effect on ezrin, and this provides a further molecular explanation for the anti-tumour action of GLA.

Gamma linolenic acid inhibits tyrosine phosphorylation of focal adhesion kinase and paxillin and tumour cell matrix interaction

Gamma linolenic acid (GLA) is an anti-cancer agent recently reported to inhibit tumour cell-matrix attachment. This study examined the effects of GLA on the adhesion of two tumour cell lines, HT115 (human colon) and MDA MB 231 (human breast), to an extracellular matrix, Matrigel. The action of GLA on focal adhesion kinase(FAK) and paxillin was also investigated. Following cell adhesion to Matrigel in control experiments, both FAK and paxillin were quickly tyrosine phosphorylated and become concentrated at focal adhesion areas. Inclusion of GLA resulted in an inhibition of the tyrosine phosphorylation of both FAK and paxillin leading to a reduced attachment of both cell types to Matrigel. FAK and paxillin were also less well distributed in the focal adhesions compared with the controls. It is concluded, therefore, that GLA inhibits tumour-matrix adhesion via the inhibition of FAK and paxillin tyrosine phosphorylation.

Stiffening effects of cortical bone on vertebral cancellous bone in situ

STUDY DESIGN

This study tested a theory about vertebral cancellous bone stiffness by performing experimental tests and comparing the results with the theoretical predictions.

OBJECTIVES

To test experimentally a theoretical prediction that vertebral cancellous bone appears stiffer than would be expected from isolated tests because of the constraining effects of the cortical bone, to measure the magnitude of this strengthening effect and its dependency on tissue composition and density.

SUMMARY OF BACKGROUND DATA

Vertebral bodies are composed mainly of cancellous bone surrounded by a thin shell of much stronger cortical bone. Little is known of the ways in which these two materials function synergistically to produce strong but light structures and why sometimes extensive damage to the cancellous bone has apparently little outward effect on vertebral body strength.

METHODS

Cancellous bone from 45 lumbar vertebrae from a homogeneous group of pigs was tested in compression both in situ in the vertebral body and as an excised cylinder. The density and composition of the bone were then measured and correlation tested with both of the stiffness measurements.

RESULTS

The cancellous bone in situ appears much stiffer than when isolated by a factor of about 4 (range, 1.6-12). No correlation was found between stiffness, either in situ or in isolation, and density, although density is predicted entirely by the volume fractions of water, organic, and mineral phases.

CONCLUSIONS

Combining low density cancellous bone with stiffer, more dense cortical bone leads to a lightweight structure that is much stronger than might be expected from the isolated properties of its components.