Results of the c-TRAK TN trial: a clinical trial utilising ctDNA mutation tracking to detect molecular residual disease and trigger intervention in patients with moderate- and high-risk early-stage triple-negative breast cancer

BACKGROUND

Post-treatment detection of circulating tumour DNA (ctDNA) in early-stage triple-negative breast cancer (TNBC) patients predicts high risk of relapse. c-TRAK TN assessed the utility of prospective ctDNA surveillance in TNBC and the activity of pembrolizumab in patients with ctDNA detected [ctDNA positive (ctDNA+)].

PATIENTS AND METHODS

c-TRAK TN, a multicentre phase II trial, with integrated prospective ctDNA surveillance by digital PCR, enrolled patients with early-stage TNBC and residual disease following neoadjuvant chemotherapy, or stage II/III with adjuvant chemotherapy. ctDNA surveillance comprised three-monthly blood sampling to 12 months (18 months if samples were missed due to coronavirus disease), and ctDNA+ patients were randomised 2 : 1 to intervention : observation. ctDNA results were blinded unless patients were allocated to intervention, when staging scans were done and those free of recurrence were offered pembrolizumab. A protocol amendment (16 September 2020) closed the observation group; all subsequent ctDNA+ patients were allocated to intervention. Co-primary endpoints were (i) ctDNA detection rate and (ii) sustained ctDNA clearance rate on pembrolizumab (NCT03145961).

RESULTS

Two hundred and eight patients registered between 30 January 2018 and 06 December 2019, 185 had tumour sequenced, 171 (92.4%) had trackable mutations, and 161 entered ctDNA surveillance. Rate of ctDNA detection by 12 months was 27.3% (44/161, 95% confidence interval 20.6% to 34.9%). Seven patients relapsed without prior ctDNA detection. Forty-five patients entered the therapeutic component (intervention n = 31; observation n = 14; one observation patient was re-allocated to intervention following protocol amendment). Of patients allocated to intervention, 72% (23/32) had metastases on staging at the time of ctDNA+, and 4 patients declined pembrolizumab. Of the five patients who commenced pembrolizumab, none achieved sustained ctDNA clearance.

CONCLUSIONS

c-TRAK TN is the first prospective study to assess whether ctDNA assays have clinical utility in guiding therapy in TNBC. Patients had a high rate of metastatic disease on ctDNA detection. Findings have implications for future trial design, emphasising the importance of commencing ctDNA testing early, with more sensitive and/or frequent ctDNA testing regimes.

Abstract OT2-11-05: SERENA-6: A Phase III study to assess the efficacy and safety of AZD9833 (camizestrant) compared with aromatase inhibitors when given in combination with palbociclib or abemaciclib in patients with HR+/HER2- metastatic breast cancer with detectable ESR1m who have not experienced disease progression on first-line therapy

Background: More than two thirds of patients with metastatic breast cancer (mBC) have hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) tumors. Current guidelines recommend combining endocrine therapy (ET), such as an aromatase inhibitor (AI), with an inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6i) as first-line (1L) treatment (Cardoso et al. Ann Oncol 2020). However, drug resistance eventually develops, leading to disease progression. Mutations in the estrogen receptor (ER) alpha gene (ESR1m) result in constitutively active, estrogen-independent ER signaling which can reduce AI efficiency (Reinert et al. Front Oncol 2017). Clinically, ESR1m are associated with acquired resistance to AI as well as more aggressive disease features, including development of visceral metastasis (Gerratana et al. Eur J Cancer 2021). At the initial diagnosis of mBC, the frequency of ESR1m is low (approximately 3%) (Bidard et al. Ann Oncol 2019); however, this increases to 17−35% of patients when disease progresses on an AI + CDK4/6i (Bidard et al. Ann Oncol 2019; Goetz et al. J Clin Oncol 2020). Patients with ESR1m tumors have poor outcomes with subsequent lines of therapy. New approaches are needed to maximize time on 1L treatment with ET + CDK4/6i and prevent further clinical and radiological disease progression. AZD9833 (camizestrant) is a highly potent, next-generation oral selective ER degrader (ngSERD) and pure ER antagonist that has demonstrated antitumor activity in a wide range of ER+ breast cancer cell lines and patient-derived xenograft models, including those with wild type ESR1 (ESR1wt) and the most prevalent ESR1m, D538G and Y537S (Scott et al. AACR 2020; Lawsone et al. AACR 2020). The Phase I SERENA-1 study demonstrated that AZD9833 shows encouraging clinical activity as monotherapy or in combination with a CDK4/6i in heavily pre-treated patients with ER+/HER2− advanced breast cancer whose tumors are ESR1wt or ESR1m (Baird et al. SABCS 2020). SERENA-6 will assess the efficacy of switching patients from AI to AZD9833, while continuing CDK4/6i treatment, once ESR1m are detected but before overt disease progression. Study description: SERENA-6 is an ongoing, randomized, multicenter, double-blind, Phase III trial. Patients with HR+/HER2− mBC who have received at least 6 months of 1L AI (letrozole or anastrozole) + CDK4/6i (palbociclib or abemaciclib) and do not have clinical or radiological disease progression will be enrolled into Step 1, the ESR1m detection phase. During this phase, patients will be monitored regularly for the presence of ESR1m via central circulating tumor DNA analysis. Patients with detectable ESR1m and no overt disease progression (by RECIST v1.1 criteria) will be enrolled into Step 2 double-blind 1:1 randomization to either continue AI plus CDK4/6i, plus a placebo for AZD9833, or switch to AZD9833 (75 mg oral once daily), plus the same CDK4/6i plus a placebo for the AI. The primary endpoint will be investigator-assessed progression-free survival (PFS) per RECIST v1.1 criteria. A key secondary endpoint will be time to second progression or death on a subsequent therapy. Other secondary endpoints will include overall survival, chemotherapy-free survival, objective response rate, clinical benefit rate, patient-reported outcomes, and safety. Enrollment began in June 2021 and is expected at approximately 200 sites across 19 countries. Acknowledgments: We thank Julia Mawer, PhD, of Oxford PharmaGenesis, UK, for medical writing assistance, which was funded by AstraZeneca. Funding: The SERENA-6 trial is funded and overseen by AstraZeneca.

Citation Format: François-Clément Bidard, Kevin Kalinsky, Massimo Cristofanilli, Giampaolo Bianchini, Stephen KL Chia, Wolfgang Janni, Cynthia X Ma, Erica L Mayer, Yeon Hee Park, Steven Fox, Xiaochun Liu, Andrew Walding, Cynthia Huang Bartlett, Nick C Turner. SERENA-6: A Phase III study to assess the efficacy and safety of AZD9833 (camizestrant) compared with aromatase inhibitors when given in combination with palbociclib or abemaciclib in patients with HR+/HER2- metastatic breast cancer with detectable ESR1m who have not experienced disease progression on first-line therapy [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 OT2-11-05.

Genomic alterations in breast cancer: level of evidence for actionability according to ESMO Scale for Clinical Actionability of molecular Targets (ESCAT)

Better knowledge of the tumor genomic landscapes has helped to develop more effective targeted drugs. However, there is no tool to interpret targetability of genomic alterations assessed by next-generation sequencing in the context of clinical practice. Our aim is to rank the level of evidence of individual recurrent genomic alterations observed in breast cancer based on the ESMO Scale for Clinical Actionability of molecular Targets (ESCAT) in order to help the clinicians to prioritize treatment. Analyses of databases suggested that there are around 40 recurrent driver alterations in breast cancer. ERBB2 amplification, germline BRCA1/2 mutations, PIK3CA mutations were classified tier of evidence IA based on large randomized trials showing antitumor activity of targeted therapies in patients presenting the alterations. NTRK fusions and microsatellite instability (MSI) were ranked IC. ESR1 mutations and PTEN loss were ranked tier IIA, and ERBB2 mutations and AKT1 mutations tier IIB. Somatic BRCA 1/2 mutations, MDM2 amplifications and ERBB 3 mutations were ranked tier III. Seventeen genes were ranked tier IV based on preclinical evidence. Finally, FGFR1 and CCND1 were ranked tier X alterations because previous studies have shown lack of actionability.

Abstract OT2-07-01: A phase 2 study of futibatinib (TAS-120) in metastatic breast cancers harboring fibroblast growth factor receptor (FGFR) amplifications (FOENIX-MBC2)

Background: FGFR1 gene amplifications occur in ~15% of invasive breast cancers (BCs) andhave been shown to be associated with endocrine therapy resistance, whereas FGFR2 amplifications occur in ~2% of invasive BCs (4% of triple-negative BCs [TNBCs]). Futibatinib is an oral, highly selective, irreversible FGFR1-4 inhibitor that has been shown to inhibit both mutant and wild-type FGFR isoforms. In a phase 1 study, futibatinib showed promising clinical activity and tolerability across tumor types, including BC. This phase 2 trial (FOENIX-MBC2) is designed to evaluate futibatinib alone or in combination with fulvestrant (a selective estrogen receptor down-regulator administered intramuscularly) in patients with metastatic BC.

Trial design: FOENIX-MBC2 is a multicenter, phase 2, open-label, non-randomized study planned to be conducted in patients with locally advanced/metastatic BC harboring FGFR1/2 amplifications who have experienced disease progression after prior therapy for advanced/metastatic disease. Eligibility criteria include an Eastern Cooperative Oncology Group performance status of 0 or 1 and no prior FGFR inhibitor treatment. Approximately 168 patients are planned to be enrolled in one of four cohorts based on a recurrent BC diagnosis and FGFR amplification status (table) as determined by local testing. Patients will receive single-agent futibatinib (cohorts 1-3) or futibatinib plus fulvestrant (cohort 4) until disease progression, unacceptable toxicity, or other discontinuation criteria are met. Primary and secondary endpoints are detailed in the table. Sample sizes for cohorts 1, 2, and 3 are based on a Simon’s optimal 2-stage design; that for cohort 4 is based on a proof-of-concept phase 2 design. The anticipated start date is August 30, 2019.

Patients, treatment, and endpoints in cohorts 1-4 of FOENIX-MBC2

CohortApprox. target enrollment (n)TreatmentKey patient inclusion criteriaEndpointsa1≤55FutibatinibHR+ HER2– BC, measurable disease per RECIST v1.1, FGFR2 amplification, and 1–3 prior endocrine therapies and ≤2 prior chemotherapy regimens for advanced/metastatic diseasePrimary: ORR Secondary: CBR, DOR, OS, PFS, 6-month PFS rate, safety2≤55FutibatinibTNBC, measurable disease per RECIST v1.1, FGFR2 amplification, and ≥1 prior chemotherapy or chemotherapy/immunotherapy regimen for advanced/metastatic diseasePrimary: ORR Secondary: CBR, DOR, OS, PFS, 6-month PFS rate, safety3≤24FutibatinibHR+ HER2– BC or TNBC; non-measurable, evaluable disease; FGFR2 amplification; and prior therapy as per cohort 1 (HR+ HER2– BC) or cohort 2 (TNBC)Primary: CBR Secondary: CR rate, DOR, OS, PFS, 6-month PFS rate, safety4≤34Futibatinib + fulvestrantHR+ HER2– BC, measurable disease per RECIST v1.1, high levels of FGFR1 amplification (FGFR1:CEN8 ratio ≥5.0 or FGFR1 copy number ≥10), and 1–2 prior endocrine-containing regimens and ≤1 prior chemotherapy regimen for advanced/metastatic disease, but no prior fulvestrantPrimary: 6-month PFS rate Secondary: ORR, CBR, DOR, OS, PFS, safetyCBR, clinical benefit rate; CR, complete response; DOR, duration of response; HER2-, human epidermal growth factor-negative; HR+, hormone-receptor-positive; ORR, objective response rate; OS, overall survival; PFS, progression-free survival; RECIST v1.1, Response Evaluation Criteria in Solid Tumors version 1.1aORR is defined as the proportion of all treated patients with a best overall response of CR or PR; CBR is defined as the proportion of all treated patients with a best overall response of CR, PR, or SD ≥24 weeks. ORR and CBR will be summarized descriptively. The 6-month PFS rate is the percentage of patients who remain alive and progression-free at 6 months estimated using the Kaplan-Meier method.

This study is funded by Taiho Oncology, Inc. and Taiho Pharmaceutical Co., Ltd.

Citation Format: Nick C. Turner, Ian E. Krop, Aditya Bardia, Senthil Damodaran, Miguel Martin, Karim A. Benhadji, Yaohua He, Mieke Ptaszynski, Carlos L. Arteaga. A phase 2 study of futibatinib (TAS-120) in metastatic breast cancers harboring fibroblast growth factor receptor (FGFR) amplifications (FOENIX-MBC2) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr OT2-07-01.

Targeting the PI3-kinase pathway in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is characterised by poor outcomes and a historical lack of targeted therapies. Dysregulation of signalling through the phosphoinositide 3 (PI3)-kinase and AKT signalling pathway is one of the most frequent oncogenic aberrations of TNBC. Although mutations in individual genes occur relatively rarely, combined activating mutations in PIK3CA and AKT1, with inactivating mutations in phosphatase and tensin homologue, occur in ∼25%‒30% of advanced TNBC. Recent randomised trials suggest improved progression-free survival (PFS) with AKT-inhibitors in combination with first-line chemotherapy for patients with TNBC and pathway genetic aberrations. We review the evidence for PI3K pathway activation in TNBC, and clinical trial data for PI3K, AKT and mammalian target of rapamycin inhibitors in TNBC. We discuss uncertainty over defining which cancers have pathway activation and the future overlap between immunotherapy and pathway targeting.

BEECH: a dose-finding run-in followed by a randomised phase II study assessing the efficacy of AKT inhibitor capivasertib (AZD5363) combined with paclitaxel in patients with estrogen receptor-positive advanced or metastatic breast cancer, and in a PIK3CA mutant sub-population

BACKGROUND

BEECH investigated the efficacy of capivasertib (AZD5363), an oral inhibitor of AKT isoforms 1-3, in combination with the first-line weekly paclitaxel for advanced or metastatic estrogen receptor-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer, and in a phosphoinositide 3-kinase, catalytic, alpha polypeptide mutation sub-population (PIK3CA+).

PATIENTS AND METHODS

BEECH consisted of an open-label, phase Ib safety run-in (part A) in 38 patients with advanced breast cancer, and a randomised, placebo-controlled, double-blind, phase II expansion (part B) in 110 women with ER+/HER2- metastatic breast cancer. In part A, patients received paclitaxel 90 mg/m2 (days 1, 8 and 15 of a 28-day cycle) with capivasertib taken twice daily (b.i.d.) at two intermittent ascending dosing schedules. In part B, patients were randomly assigned, stratified by PIK3CA mutation status, to receive paclitaxel with either capivasertib or placebo. The primary end point for part A was safety to recommend a dose and schedule for part B; primary end points for part B were progression-free survival (PFS) in the overall and PIK3CA+ sub-population.

RESULTS

Capivasertib was well tolerated, with a 400 mg b.i.d. 4 days on/3 days off treatment schedule selected in part A. In part B, median PFS in the overall population was 10.9 months with capivasertib versus 8.4 months with placebo [hazard ratio (HR) 0.80; P = 0.308]. In the PIK3CA+ sub-population, median PFS was 10.9 months with capivasertib versus 10.8 months with placebo (HR 1.11; P = 0.760). Based on the Common Terminology Criteria for Adverse Event v4.0, the most common grade ≥3 adverse events in the capivasertib group were diarrhoea, hyperglycaemia, neutropoenia and maculopapular rash. Dose intensity of paclitaxel was similar in both groups.

CONCLUSIONS

Capivasertib had no apparent impact on the tolerability and dose intensity of paclitaxel. Adding capivasertib to weekly paclitaxel did not prolong PFS in the overall population or PIK3CA+ sub-population of ER+/HER2- advanced/metastatic breast cancer patients.ClinicalTrials.gov: NCT01625286.

Clinical considerations of the role of palbociclib in the management of advanced breast cancer patients with and without visceral metastases

Background

This report assesses the efficacy and safety of palbociclib plus endocrine therapy (ET) in women with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer (ABC) with or without visceral metastases.

Patients and methods

Pre- and postmenopausal women with disease progression following prior ET (PALOMA-3; N = 521) and postmenopausal women untreated for ABC (PALOMA-2; N = 666) were randomized 2 : 1 to ET (fulvestrant or letrozole, respectively) plus palbociclib or placebo. Progression-free survival (PFS), safety, and patient-reported quality of life (QoL) were evaluated by prior treatment and visceral involvement.

Results

Visceral metastases incidence was higher in patients with prior resistance to ET (58.3%, PALOMA-3) than in patients naive to ET in the ABC setting (48.6%, PALOMA-2). In patients with prior resistance to ET and visceral metastases, median PFS (mPFS) was 9.2 months with palbociclib plus fulvestrant versus 3.4 months with placebo plus fulvestrant [hazard ratio (HR), 0.47; 95% confidence interval (CI), 0.35–0.61], and objective response rate (ORR) was 28.0% versus 6.7%, respectively. In patients with nonvisceral metastases, mPFS was 16.6 versus 7.3 months, HR 0.53; 95% CI 0.36–0.77. In patients with visceral disease and naive to ET in the advanced disease setting, mPFS was 19.3 months with palbociclib plus letrozole versus 12.9 months with placebo plus letrozole (HR 0.63; 95% CI 0.47–0.85); ORR was 55.1% versus 40.0%; in patients with nonvisceral disease, mPFS was not reached with palbociclib plus letrozole versus 16.8 months with placebo plus letrozole (HR 0.50; 95% CI 0.36–0.70). In patients with prior resistance to ET with visceral metastases, palbociclib plus fulvestrant significantly delayed deterioration of QoL versus placebo plus fulvestrant, whereas patient-reported QoL was maintained with palbociclib plus letrozole in patients naive to endocrine-based therapy for ABC.

Conclusions

Palbociclib plus ET prolonged mPFS in patients with visceral metastases, increased ORRs, and in patients previously treated for ABC, delayed QoL deterioration, presenting a standard treatment option among patients with visceral metastases amenable to endocrine-based therapy.

Clinical trial registration

NCT01942135, NCT01740427

Abstract P5-19-05: Health-related quality of life during a phase 2 study of talazoparib in patients with advanced breast cancer and germline BRCA1/2 mutations (ABRAZO)

Background: Talazoparib (TALA; 1 mg/d) was well tolerated and exhibited promising antitumor activity in ABRAZO, a 2-cohort, 2-stage, open-label phase 2 study (NCT02034916) in patients (pts) with locally advanced or metastatic breast cancer and gBRCA1/2 mutations following platinum-based therapy (cohort 1 [C1]) or ≥3 platinum-free cytotoxic-based regimens (cohort 2 [C2]). This analysis evaluates health-related quality of life (QoL) for both cohorts.

Methods: QoL was assessed on day 1 (baseline) and every 6 weeks for the initial 24 weeks and every 12 weeks thereafter, or sooner if progression was clinically suspected, using the EORTC QLQ-C30 and its breast cancer module, QLQ-BR23. For all scales, results were summarized using descriptive statistics for each cohort and at each time point, based on Characters (max 3400 including title, body and table [including spaces]): 3363 No abbreviations in title; title sentence case; define acronyms; no figures Category: Psychosocial, QOL, and Educational Aspects – Other 2 observed values and changes from baseline (clinically meaningful defined as ≥10-point change from baseline). Time to deterioration (TTD; defined as ≥10-point decrease in global health status [GHS]/functional scales or increase in symptom scales) analyses using survival analysis methods were carried out on the GHS/functional scales of QLQ-C30 and symptom scales of QLQ-BR23.

Results:GHS was maintained from baseline across all time points for both C1 and C2 except at week 24 in C2, when a statistically significant but not clinically meaningful improvement in GHS was observed. In C1, statistically significant and clinically meaningful improvement was observed at specific time points in 4 functional scales (body image, week 6; sexual functioning, week 24; sexual enjoyment, week 36; and future perspective, weeks 6, 18, and 24) and in 3 symptom scales (dyspnea, week 24; insomnia, week 24; and breast symptoms, weeks 6 and 36). Statistically significant and clinically meaningful deterioration in C1 was observed in 2 functional scales (emotional functioning, week 12 and end of treatment, and role functioning, end of treatment) and in 1 symptom scale (fatigue, week 6). In C2, statistically significant and clinically meaningful improvement was observed at specific time points in 4 functional scales (role functioning, week 24; social functioning, week 24; sexual enjoyment, week 18; and future perspective, weeks 6, 12, and 18) and in 5 symptom scales (nausea/vomiting, week 18; pain, weeks 12, 18, and 24; insomnia, week 24; breast symptoms, weeks 12 and 18; and arm symptoms, week 48). For C2, no statistically significant and clinically meaningful deterioration was observed for any functional or symptoms scales across all time points, except in the dyspnea symptom scale at week 18. For C1 and C2, the median (95% confidence interval) TTD of GHS was 2.8 (2.1-3.0) and 5.5 (4.2-5.7) months, respectively. The median TTD for all QLQ-C30 functional scales for C1 and C2 ranged 2.1-3.1 and 4.2-5.6 months, respectively; the median TTD for all QLQ-BR23 symptoms scales ranged 2.6-4.0 and 4.2-5.6 months, respectively.

Conclusions: The QoL of TALA-treated patients during ABRAZO was maintained. QoL is being evaluated among atients with germline BRCA1/2 mutated advanced BC treated with TALA vs physician's choice chemotherapy in the phase 3 EMBRACA trial (NCT01945775).

Citation Format: Hurvitz SA, Turner NC, Telli ML, Rugo HS, Mailliez A, Ettl J, Grischke E-M, Mina LA, Balmaña J, Fasching PA, Tudor C, Quek RGW, Hannah AL, Robson ME, Wardley AM. Health-related quality of life during a phase 2 study of talazoparib in patients with advanced breast cancer and germline BRCA1/2 mutations (ABRAZO) [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 P5-19-05.

Abstract P1-14-03: ABRAZO: Exposure-efficacy and -safety analyses of breast cancer patients with germline BRCA1/2 mutations receiving talazoparib in a phase 2 open-label trial

Background: Talazoparib (TALA) is a dual-mechanism poly (ADP-ribose) polymerase (PARP) inhibitor that traps PARP on DNA. Efficacy results of this phase 2 trial were previously presented (Turner et al, ASCO 2017, abstract 1007). This study included sparse pharmacokinetic (PK) sampling for patients through cycle 4 of therapy. Exploratory analyses included assessment of exposure versus parameters of efficacy and safety.

Methods: ABRAZO (NCT02034916) was a parallel-cohort, open-label phase 2 study of TALA (1 mg/d) following (i) platinum-based therapy (cohort 1) or (ii) ≥3 platinum-free cytotoxic-based regimens (cohort 2) in patients with locally advanced or metastatic breast cancer and germline BRCA1/2 mutation. Sparse PK sampling was performed on day 1 of cycles 1-4, consisting of a predose sample collected ≤60 minutes prior to dosing and 2 postdose samples collected ≥30 minutes after dosing (time of food ingestion prior to the dose was collected). The collection times of the 2 postdose samples were separated by ≥2 hours. Efficacy parameters included radiographic progression-free survival (rPFS) by central review and objective response rate (ORR). Safety parameters included incidence of overall adverse events (AEs) and grade ≥3 AEs. Individual AUCs (area under concentration-time curves) for exposure-response analyses were predicted by population PK analyses.

Results: Patients were divided into AUC tertiles: low (median, 109.0 ng*hr/mL; n=27), intermediate (median, 170.8 ng*hr/mL; n=27), and high (median, 219.2 ng*hr/mL; n=27). Median rPFS was 5.3 months (95% confidence interval [CI], 3.1, 8.3) in the lowest AUC tertile, 5.6 months (95% CI, 3.7, 8.4) in the intermediate AUC tertile, and 5.3 months (95% CI, 3.9, 5.6) in the highest AUC tertile. The ORR was 22.2% (95% CI, 8.6, 42.3) in the lowest AUC tertile, 25.9% (95% CI, 11.1, 46.3) in the intermediate AUC tertile, and 37.0% (95% CI, 19.4, 57.6) in the highest AUC tertile. AEs of any grade were reported in 11 patients (40.7%) in the lowest AUC tertile, 21 patients (77.8%) in the intermediate AUC tertile, and 22 patients (81.5%) in the highest AUC tertile. Grade ≥3 AEs were reported in 8 patients (29.6%) in the lowest AUC tertile and in 18 patients (66.7%) in the intermediate and highest AUC tertiles. The most common AEs in all 3 exposure tertiles were anemia, thrombocytopenia, and neutropenia.

Conclusions: Median rPFS did not change with increasing systemic exposure. There may be a trend to higher ORR in patients with highest systemic exposure. A larger percentage of patients experienced AEs with elevated systemic exposure. Increased response rates with greater exposure does not translate to improved rPFS. These results should be interpreted with caution due to the low patient numbers in each cohort.

Citation Format: Telli ML, Turner NC, Mailliez A, Ettl J, Grischke E-M, Mina LA, Balmaña J, Hurvitz SA, Wardley AM, Fasching PA, Tudor C, Nguyen L, Hannah AL, Robson ME, Rugo HS. ABRAZO: Exposure-efficacy and -safety analyses of breast cancer patients with germline BRCA1/2 mutations receiving talazoparib in a phase 2 open-label 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 P1-14-03.

Abstract OI-1: Tackling Breast Cancer Diversity

Breast cancer is a highly diverse disease with multiple subtypes and driver mutations. Further diversity may develop, particularly in metastatic breast cancer, due to the selective pressure of treatment. In ER positive breast cancer, activating mutations of the oestrogen receptor (ESR1), along with mutations in the NF1, KRAS and FGFR genes, are all enriched in endocrine resistant breast cancer, although rare in untreated primary breast cancer.

This diversity presents a substantial challenge to the treatment of metastatic breast cancer, with new therapeutic approaches required to tackle this heterogeneity. Circulating tumour DNA analysis, to identify selected mutations in the tumour and guide matching targeted therapy, has preliminary evidence of clinical utility. Targeting common phenotypes presents an alterative therapeutic approach, targeting the dependence of luminal breast cancer on CDK4/6 to initiate cell cycle entry. Pre-clinical evidence supports combining CDK4/6 inhibition with mutation-targeted therapies, although implementing these combinations presents a substantial clinical translational challenge.

A novel approach to overcoming tumour heterogeneity is to identify and target micro-metastatic cancer in the adjuvant setting. Micro-metastatic cancer can be detected with highly sensitive circulating tumour DNA analysis for minimal residual disease (MRD) detection. This may open up a new paradigm of treatment guided by MRD monitoring, potentially treating cancer in a setting where the cancer may be less genetically diverse, with lower potential to develop resistance to therapy.

Citation Format: Turner NC. Tackling Breast Cancer Diversity [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 OI-1.

Abstract P2-02-01: Withdrawn

This abstract was withdrawn by the authors.

Abstract P4-22-03: Palbociclib in combination with endocrine therapy in treatment-naive and previously treated elderly women with HR+, HER2– advanced breast cancer: a pooled analysis from randomized phase 2 and 3 studies

Background: At least 40% of breast cancers are diagnosed in women ≥65 y old and most are hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-). Palbociclib (PAL) is an oral, small-molecule inhibitor of cyclin-dependent kinases 4 and 6. Randomized studies of PAL combined with endocrine therapy (ET) demonstrated significantly improved progression-free survival (PFS) in patients (pts) with treatment-naive and previously treated advanced breast cancer (ABC).

Methods: We evaluated the efficacy of PAL+ET vs ET alone in pts aged ≥65-74 and ≥75 y across multiple pivotal randomized phase 2 and 3 studies. Safety and pharmacokinetics (PK) data (blood samples collected from pts in phase 1/2 [PALOMA-1] and phase 1 studies [NCT00141297 and NCT00420056]) for PAL+ET were pooled and compared across age groups. Pts who had not received treatment for ABC were randomized to receive PAL+letrozole (LET) or LET alone/with placebo (PBO; PALOMA-1, open-label/PALOMA-2, double-blind). Pts who had progressed on prior ET were randomized to receive PAL+fulvestrant (FUL) or PBO+FUL (PALOMA-3, double-blind). The primary endpoint for these studies was investigator-assessed PFS. Safety assessments and blood counts occurred at baseline and every 2 weeks for the first 2 cycles and on day 1 of subsequent cycles.

Results: Among 872 pts treated with PAL+ET, 221 (25%) were aged ≥65-74 y and 83 (10%) were ≥75 y (PAL+LET: n=528, 162 and 56, respectively; PAL+FUL: n=347, 59 and 27). Median (range) treatment durations were 440 (1-1615) d, 502 (1-1615) d, and 459 (21-1404) d, respectively. Improvement in efficacy endpoints was seen with PAL+ET vs ET across all age groups (Table 1). Incidence of adverse events (AEs), serious AEs and discontinuations due to AEs were similar in the overall population (99%, 19%, 3%) and in pts aged ≥65-74 (99%, 25%, 5%) and ≥75 y (100%, 30%, 6%). Incidence of all grades and grade 3/4 neutropenia were also similar across age groups (overall: 67% and 54%; ≥65-74 y: 64% and 51%; ≥75 y: 77% and 60%). PK analysis showed no clinically relevant differences between arithmetic means, medians, and geometric means of the apparent oral clearance across age groups.

Conclusions: PAL in combination with ET is an effective and well-tolerated treatment option for elderly pts with HR+/HER2- endocrine-sensitive and -resistant ABC. A dose adjustment based on age is not required.

Sponsor: Pfizer

Table 1. PFS in pts ?65-74 and ?75 y (ITT populations)OverallAged ≥65-74 yAged ≥75 yPALOMA-1/PALOMA-2PAL+LET vs528 vs 303162 vs 9456 vs 26LET/LET+PBO,* nHR (95% CI);0.53 (0.44-0.64);0.66 (0.45-0.97);0.31 (0.16-0.61);1-sided P value<0.00010.01620.0002Median PFS (95% CI), mo24.4 (22.0-26.2) vs27.5 (24.2-NR) vsNR (19.2-NR) vs13.6 (11.1-16.4)21.8 (16.3-31.3)10.9 (4.9-24.9)PALOMA-3PAL+FUL vs347 vs 17459 vs 3727 vs 6FUL+PBO, nHR (95% CI);0.46 (0.36-0.59);0.25 (0.14-0.45);0.87 (0.27-2.79);1-sided P value<0.0001<0.00010.4074Median PFS (95% CI), mo9.5 (9.2-11.0) vs16.1 (12.0-NR) vs13.6 (7.5-NR) vs4.6 (3.5-5.6)3.7 (1.9-5.3)7.4 (1.9-NR)HR=hazard ratio; ITT=intent to treat; NR=not reached. *Does not include 5 pts from phase 1 of PALOMA-1.

Citation Format: Rugo HS, Turner NC, Finn RS, Joy AA, Verma S, Harbeck N, Moulder S, Masuda N, Im Y-H, Zhang K, Kim S, Sun W, Schnell P, Huang-Bartlett C, Slamon D. Palbociclib in combination with endocrine therapy in treatment-naive and previously treated elderly women with HR+, HER2– advanced breast cancer: a pooled analysis from randomized phase 2 and 3 studies [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-22-03.

Abstract P1-02-01: Circulating tumor DNA analysis to predict relapse and overall survival in early breast cancer – Longer follow-up of a proof-of-principle study

Background

In a previous proof-of-principle study we demonstrated that detection of circulating tumour DNA (ctDNA) in the adjuvant setting, after completion of surgery and chemotherapy for early stage breast cancer, was associated with a high risk of early relapse. Here we present longer follow-up of the same series, to define the predictive power of ctDNA analysis for disease free survival, and assess the potential to predict overall survival.

Methods

We recruited a cohort of 55 women presenting with early stage, primary breast cancer, who were all scheduled to receive neo-adjuvant chemotherapy. The primary tumour was sequenced to identify somatic mutations, identifying at least one mutation in 43 patients. Mutations were tracked with digital PCR to identify ctDNA, in plasma samples taken either at a single post-surgical time point (2-6 weeks post-surgery) or with serial plasma samples taken every 6 months in the adjuvant setting.

Results

At a median 31.7 months follow-up, 42% (18/43) patients had relapsed. Detection of ctDNA at the single post-surgical time point was associated with poor disease free survival, HR=13.6 95%CI (4.5, 41.2) p<0.001, and overall survival HR=84.7 95%CI (9.8, 730.4) p<0.001. All patients with ctDNA detected in a single post-surgical time point relapsed and died in the follow-up period (7/7, 100% specificity), although the single post-surgery time point had modest 39% (7/18) sensitivity for relapse. Detection of ctDNA at any point in serial sampling was associated with poor disease free survival HR=25.7 95%CI (8.3, 79.8) p<0.001 and overall survival HR=47.1 95%CI (6.1, 366.1) p<0.001. All patients with ctDNA detected in a serial mutation tracking relapsed in the follow-up period (14/14, 100% specificity), with 78% (14/18) sensitivity for relapse. Sensitivity was limited by 3 cases of brain only relapse and one case of solitary ovarian relapse. Detection of ctDNA in serial sampling had a median lead-time of 8.1 months over clinical relapse.

Conclusion

Detection of ctDNA in the adjuvant setting has a high predictive power for future relapse and death from breast cancer. Therapeutic trials are required to determine whether mutation tracking identifies relapse sufficiently early to allow for further adjuvant therapy.

Citation Format: Turner NC, Garcia-Murillas I, Chopra N, Beaney M, Kilburn L, Cutts R, Osin P, Nerurkar A, Schiavon G, Hrebien S, Bliss J, Dowsett M, Smith I. Circulating tumor DNA analysis to predict relapse and overall survival in early breast cancer – Longer follow-up of a proof-of-principle study [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-02-01.

Abstract ES7-2: ES7-2 Mechanisms of resistant to therapy in ER positive cancer

Recent years have seen substantial advances in our understanding of ER positive/ HER2 negative breast cancer, both in the genetics of this subtype of breast cancer and the biological processes the drive tumor growth and resistance to therapy. Diverse targetable mutations have been identified in studies of primary breast cancer, along with acquired mutations in the estrogen receptor (ESR1) found in 30% of advanced breast cancers that progress on aromatase inhibitors. The therapeutic significance of this genetic diversity is being explored in ongoing studies. Therapies that target mTOR and CDK4/6 have entered routine clinical practice, demonstrating substantial improvements in progression free survival for patients with advanced cancer. The ongoing challenge is to identify biomarkers of sensitivity, to assist in selecting patients who benefit, and identify mechanisms of resistance to therapy to identify the optimal schedule of therapies and identify novel therapeutic approaches for resistant disease.

Citation Format: Turner NC. ES7-2 Mechanisms of resistant to therapy in ER positive cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr ES7-2.

Abstract P4-22-07: Long-term safety of palbociclib in combination with endocrine therapy in treatment-naive and previously treated women with HR+ HER2– advanced breast cancer: A pooled analysis from randomized phase 2 and 3 studies

Background: Palbociclib (PAL) is a selective and reversible oral cyclin-dependent kinase 4 and 6 inhibitor. Large randomized phase (ph) 2 and 3 trials showed significant improvement in progression-free survival (PFS) when PAL was combined with endocrine therapy (ET) vs ET alone in treatment (trt)-naive and previously treated hormone receptor?positive human epidermal growth factor receptor 2?negative (HR+ HER2–) advanced breast cancer (ABC) patients (pts). The median PFS with PAL+ET is >2 years as a first-line therapy for ABC and 11.2 mo in endocrine-resistant ABC. We evaluated the long-term safety in PALOMA-1, -2, and -3.

Methods: We analyzed the tolerability of PAL in combination with ET in 3 randomized trials. Pts untreated for ABC were randomized to receive PAL+letrozole (LET) vs LET alone in PALOMA-1 (ph 2, open-label; 1:1) or randomized to receive PAL+LET vs placebo (PBO)+LET in PALOMA-2 (ph 3, double-blind; 2:1). PALOMA-3 included pts who progressed on prior ET, randomized to receive PAL+fulvestrant (FUL) or PBO+FUL (ph 3, double-blind; 2:1). Safety assessments, including a complete blood count, were done at baseline, on D1 of each cycle, and on D14 of the first 2 cycles. We evaluated adverse events (AEs) by 6-mo intervals (out to 36 mo) and cumulatively (12-, 24-, and 36-mo time points), and assessed latency (event onset) of pertinent adverse drug reactions (ADRs) in all pts treated in PALOMA-1, -2, and -3.

Results: A total of 1352 pts were pooled for this analysis; 872 pts received PAL+ET (527 pts, PAL+LET; 345 pts, PAL+FUL). Median duration of trt was 421 days in PALOMA-1 (January 2015), 603 days in PALOMA-2 (February 2016), and 330 days in PALOMA-3 (July 2015). PAL+LET was received by 119 pts as first-line trt in PALOMA-1 and 2 for 24–<30 months and 11 pts were treated for >36 mo. PAL+FUL was received by 140 pts for >12 mo as second-line trt in PALOMA-3. The most commonly reported ADRs across all studies were neutropenia, fatigue, nausea, anemia, and leukopenia. The 6-mo-interval analyses of the most common (>15%) AEs (by preferred term [PT]) from PALOMA-1, -2, and -3 indicated that these AEs were reported with the highest frequency during the first 6-mo interval and typically decreased in incidence over time to 30–<36-mo; the most common hematologic AEs (clustered PTs) are shown (Table). The cumulative incidence of AEs after the first vs the second and third years showed similar frequencies of most AEs, including the most common ADRs.

Conclusions: Based on these long-term safety analyses, there is no evidence of specific cumulative or delayed toxicity resulting from prolonged trt with PAL+ET for HR+ HER2– ABC. This supports the ongoing investigation of PAL+ET in early breast cancer (NCT02513394).

Table. Pooled hematologic AEs: all grades and all causality clustered PTs reported for ≥10% of PAL+ET (LET/FUL)-treated ptsTime interval, mo0–<66–<1212–<1818–<2424–<3030–<36≥36Patients, N8726764912891192711TEAEs, %       Neutropenia75.758.649.349.842.937.054.5Leukopenia40.027.416.711.87.611.118.2Anemia20.812.710.011.19.211.118.2Thrombocytopenia15.18.76.15.55.914.836.4TEAEs=treatment-emergent adverse events.

Sponsor: Pfizer.

Citation Format: Diéras V, Rugo HS, Gelmon K, Finn RS, Cristofanilli M, Loi S, Colleoni M, Lu D, Gauthier E, Huang-Bartlett C, Turner NC, Schnell P. Long-term safety of palbociclib in combination with endocrine therapy in treatment-naive and previously treated women with HR+ HER2– advanced breast cancer: A pooled analysis from randomized phase 2 and 3 studies [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-22-07.

Abstract P4-13-03: Updated safety from a double-blind phase 3 trial (PALOMA-3) of fulvestrant with placebo or with palbociclib in pre- and postmenopausal women with hormone receptor-positive, HER2-negative metastatic breast cancer that progressed on prior endocrine therapy

Background: Endocrine therapy (ET) resistance remains a major clinical problem for patients (pts) with hormone receptor (HR+) breast cancer (BC). In PALOMA-3, palbociclib (P) combined with fulvestrant (F) demonstrated significant prolongation of progression-free survival (PFS) vs F plus placebo (PLB) in pre/peri and postmenopausal women with HR+/HER2– metastatic BC (MBC) whose disease progressed on prior ET (median PFS 9.2 vs 3.8 m; HR=0.422, P=0.0001).

Methods: In this double-blind phase 3 study, 521 pts with HR+/HER2– MBC were randomized 2:1 to receive P (125 mg/d orally for 3 weeks followed by 1 week off) and F (500 mg given per standard of care) or PLB plus F. Pre- and perimenopausal women also received goserelin. One previous line of chemotherapy (CT) for MBC was allowed. Safety assessments occurred at baseline and D1 of each cycle; blood counts occurred every 2 wks for the first 2 cycles and on D1 of subsequent cycles. As pts may have experienced multiple episodes of neutropenia during treatment, we analyzed all episodes in aggregate based on laboratory data per CTCAE4.0.

Results: The results reported here are from the data cutoff of Dec 2014, with a median follow-up of 5.6 m. Overall rate of any grade (G) and G3/4 AEs was 98/70% of pts in P+F vs 89/18% in PLB+F. The most commonly reported AEs in P+F (≥20%) were hematologic toxicities, fatigue, nausea, and headache. Per lab data, G3/G4 neutropenia occurred in 52.2/8.2%, G3/G4 leukopenia in 39.5/1.2%, G3/G4 anemia in 20.8/2.9% and G3/G4 thrombocytopenia in 2.1/1.2% of pts on P+F. Neutropenia occurred early, with a median onset time for first episode of ≥G3 neutropenia of 15 d (13–197) and median time from first dose to the lowest absolute neutrophil count (ANC) of 29 d (13–334). The median duration of ≥G3 episode was 7 d (1–35), suggesting that most pts can resume treatment after a 1-week cycle delay. A comparable proportion of any grade neutropenia was observed in pts with or without prior CT (prior CT 88.4% vs no prior CT 85.4%). There was no difference in the rate of G3/G4 neutropenia in the older pts (>65 yrs, 51% vs ≤65 yrs, 57%) in P+F arm. Concurrent G≥3 infections occurred in 1% of pts with G≥3 neutropenia (2/192 pts). Febrile neutropenia occurred in 0.6% of pts in both arms. 21% of pts had dose reductions and 45% had dose interruption due to neutropenia. Dose intensity was maintained at 89.7% for P. Serious adverse events (SAEs) were reported in 9.6% of pts on P+F and in 14% of pts on PLB+F. The most common SAEs on P+F were pulmonary embolism (0.9%) and pyrexia (0.9%). Safety analyses with longer follow-up (data cut off, March 2015) are ongoing and will be presented.

Conclusions: Findings suggest P+F has a favorable safety profile characterized mainly by asymptomatic hematologic toxicity. Overall SAE rates were low and comparable between the 2 arms. Palbociclib-related neutropenia differs from that seen with CT, consistent with proposed mechanism of action, in that it is not commonly associated with fever, and can be effectively managed by a dose interruption or cycle delay.

Funding: Pfizer, Inc.

Citation Format: Verma S, DeMichele AM, Loi S, Ro J, Colleoni M, Iwata H, Harbeck N, Stearns V, Cristofanilli M, Huang Bartlett C, Schnell P, Zhang K, Thiele A, Turner NC, Rugo HS. Updated safety from a double-blind phase 3 trial (PALOMA-3) of fulvestrant with placebo or with palbociclib in pre- and postmenopausal women with hormone receptor-positive, HER2-negative metastatic breast cancer that progressed on prior endocrine therapy. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-03.

Abstract OT1-03-17: ABRAZO: An international phase 2 (2-stage, 2-cohort) study of the oral PARP inhibitor talazoparib (BMN 673) in BRCA mutation subjects with locally advanced and/or metastatic breast cancer

Background: Cancer cells with deleterious mutations in breast cancer susceptibility genes 1 and 2 (BRCA1/2) are deficient in the DNA double-strand break repair mechanism, rendering them highly dependent on the single-strand break repair pathway, which is initiated by poly-(ADP-ribose) polymerase (PARP) [1-3]. In cells with deleterious BRCA1/2 mutations, PARP inhibition is synthetically lethal because of accumulation of irreparable DNA damage [1-3]. Talazoparib (BMN 673) exhibits a novel two-pronged approach in treating BRCA1/2-mutant tumors: 1) potent catalytic inhibition of the PARP enzyme; and 2) trapping of PARP at sites of DNA damage [4-7]. The capacity to trap PARP-DNA complexes varies widely across PARP inhibitors and is not correlated with catalytic inhibition potency [4-7]. In preclinical models, trapping PARP on DNA is more potent at inducing cancer cell death than enzymatic inhibition of PARP alone [4,7]. Talazoparib is the most potent clinical-stage PARP inhibitor tested to date with the highest efficacy at trapping PARP-DNA complexes [7]. Talazoparib has shown single-agent antitumor efficacy in several solid tumor types and was generally well tolerated in a phase 1/2 clinical study [8].

Methods: This 2-stage, 2-cohort, phase 2 international study (ABRAZO) evaluates the safety and efficacy of talazoparib in patients with a deleterious germline BRCA1 or BRCA2 mutation with locally advanced and/or metastatic breast cancer. Eligible subjects will be assigned to one of two cohorts based on prior chemotherapy for metastatic disease. Cohort 1 (n=70) includes patients with a complete response (CR) or partial response (PR) to platinum-containing regimens for metastatic disease. Cohort 2 (n=70) includes patients who have received >2 prior chemotherapy regimens in the metastatic setting but have not had prior platinum therapy for locally advanced or metastatic disease (prior adjuvant or neoadjuvant therapy with a platinum is allowed). The primary objective is objective response rate (ORR). Secondary objectives include clinical benefit response (CBR) rate, duration of response (DOR), progression-free survival (PFS), and overall survival (OS). Health-related quality of life (QoL) assessments are an exploratory objective. Eligible subjects will receive oral talazoparib (1 mg/day, 21-day cycles) until disease progression or unacceptable toxicity. This trial is currently enrolling patients from the United States and Europe (NCT02034916).

This study is funded by BioMarin Pharmaceutical Inc.

References:

1. Ashworth A. J Clin Oncol. 2008;26:3785-3790; 2. Jalve M, Curtin NJ. Ther Adv Med Oncol. 2011;3:257-267; 3. Helleday T. Mol Oncol. 2011;5:387-393; 4. Murai J et al. Cancer Res. 2012;72:5588-5599; 5. Rouleau M et al. Nat Rev Cancer. 2010;10:293-301; 6. Shen Y et al. Clin Cancer Res. 2013;19:5003-5015; 7. Murai J et al. Mol Cancer Ther. 2014;13:433-443; 8. Wainberg ZA et al. J Clin Oncol. 2014;32(suppl):5. Abstract 7522.

Citation Format: Turner NC, Balmaña J, Fasching PA, Hurvitz SA, Rugo HS, Telli ML, Visco F, Wardley AM, Yang X, Lokker NA, Lounsbury DL, Robson ME. ABRAZO: An international phase 2 (2-stage, 2-cohort) study of the oral PARP inhibitor talazoparib (BMN 673) in BRCA mutation subjects with locally advanced and/or metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT1-03-17.

Abstract P4-13-01: PALOMA3: Phase 3 trial of fulvestrant with or without palbociclib in pre- and postmenopausal women with hormone receptor-positive, HER2-negative metastatic breast cancer that progressed on prior endocrine therapy—confirmed efficacy and safety

Background: Selective estrogen receptor modulators and aromatase inhibitors (AI) (+LHRH agonists [premenopausal]) are standard of care (SOC) for hormone–receptor–positive (HR+) metastatic breast cancer (MBC). Many HR+ MBC patients (pts) get limited benefit from adjuvant or advanced endocrine therapy (ET) and develop endocrine resistance, refractory disease. HR+ BC growth relies on cyclin dependent kinases 4/6 that promote G1–S phase cell cycle progression. Palbociclib (PAL) with ET showed efficacy in HR+/HER2– MBC (Turner et al, 2015). We report updated safety and efficacy from PALOMA3 with longer follow–up, focusing on degrees of clinically defined endocrine resistance.

Methods: Pts with HR+/HER2– MBC that progressed on prior ET were randomized 2:1 to PAL (125 mg/d oral [3 wks drug, 1 wk off]) + fulvestrant (F, 500 mg, SOC) +/– goserelin or placebo (PLB)+F. One line of chemotherapy (CT) for MBC was allowed. Pt stratification: prior ET sensitivity; visceral metastases; menopausal status. Primary endpoint (EP) was investigator–assessed progression–free survival (PFS). Secondary EP: overall survival, response assessment, patient–reported outcomes, safety.

Results: By March 2015, median follow–up was 8.9 mo. 521 pts were randomized (PAL+F, 347; PLB+F, 174). Baseline characteristics were balanced. Median PFS was 9.5 (95% CI 9.2–11.0) mo (PAL+F) vs 4.6 (3.5–5.6) mo (PLB+F) (HR 0.46 [0.36–0.59], P<0.001). Overall response (CR+ PR) was significantly improved with PAL+F (ITT: 19% vs 8.6%, P=0.001; pts with measurable disease: 24.6% vs 10.9%, P<0.001). Clinical benefit (CBR=CR+PR+SD ?24wks) was 66.6% vs 39.7% (P<0.001). Benefit from PAL was confirmed in pre– and postmenopausal pts with PFS in premenopausal 9.5 vs 5.6 mo (HR=0.50 [0.29–0.87], P=0.006) and in postmenopausal 9.9 vs 3.9 mo (HR=0.45 [0.34–0.59], P<0.001). Common adverse events (AEs) for PAL+F vs PLB+F were neutropenia (80.9 vs 3.5%), leukopenia (49.6 vs 4.1%), and fatigue (39.1 vs 28.5%); febrile neutropenia occurred in 0.9% (P+ F) vs 0.6% pts (PLB+F). Discontinuation due to AEs was 4.0% on P vs 1.7% on PLB. The benefit of PAL+F vs PLB+F was compared in pts with various degrees of endocrine resistance: a) progression ≤12 mo of adjuvant ET completion, PFS 9.5 vs 5.4 mo (HR 0.55 [0.32–0.92], P=0.01); b) failed 1 line of ET, 10.2 vs 5.4 mo (HR 0.42 [0.29–0.59], P<0.001); c) failed 2 lines of ET, 9.9 vs 1.8 mo (HR=0.20 [0.10– 0.39, P<0.001); d) proven endocrine sensitive, 10.2 vs 4.2 mo (HR 0.42 [0.32–0.56], P<0.001); e) proven no prior endocrine sensitivity, 7.5 vs 5.4 mo (HR 0.64 [0.39–1.07], P=0.04) f) AI most recent therapy, 9.5 vs 3.7 mo (HR 0.42 [0.31–0.56], P<0.001).

Conclusion: Mature efficacy confirmed superior PFS and demonstrated significantly improved clinical response and CBR by the combination of ET and Palbociclib. It also consistently showed therapeutic benefit irrespective of menopausal status and various degrees of endocrine sensitivity. Safety profile is favorable. PAL+F may be an effective option for HR+ MBC pts.

Funding: Pfizer.

Citation Format: Cristofanilli M, Bondarenko I, Ro J, Im S-A, Masuda N, Colleoni M, DeMichele AM, Loi S, Verma S, Iwata H, Huang Bartlett C, Zhang K, Puyana Theall K, Turner NC, Slamon DJ. PALOMA3: Phase 3 trial of fulvestrant with or without palbociclib in pre- and postmenopausal women with hormone receptor-positive, HER2-negative metastatic breast cancer that progressed on prior endocrine therapy—confirmed efficacy and safety. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-01.

Abstract P2-08-01: Analysis of PIK3CA mutation abundance in primary breast cancer with droplet digital PCR identifies frequent sub-clonal PIK3CA mutations in ER negative and / or HER2 positive breast cancer

Background: PIK3CA is the single most commonly mutated gene in breast cancer, with highest incidence reported in ER positive and HER2 negative breast cancer. Substantial data now suggests that breast cancers show intra-tumoural genetic heterogeneity, with apparently clonal tumours composed of multiple populations of tumour cells that, in addition to the founder genetic events common to all cells, harbour private genetic alterations. Tumours with mutations that are sub-clonal may respond less well to therapies targeting these mutations than cancers with clonal mutations. To assess how frequently PIK3CA mutations are clonal founder mutations, or may be subclonal, we assessed the abundance on PIK3CA mutation using digital PCR.

Methods: DNA was extracted from frozen sections of 119 primary breast cancers, following macrodissection to achieve tumour cell content of >70%. PIK3CA mutations c.1624G>A (E542K), c.1633G>A (E545K), c.3140A>T (H1047L) and c.3140A>G (H1047R) were assessed by droplet digital PCR on a BioRad QX100 system. Exon 9 mutation assays were optimised to not amplify the PIK3CA pseudogene. Mutational abundance was calculated from the Poisson distribution, expressed as the portion of PIK3CA DNA in the sample that was mutant, and compared between breast cancer subtypes. A mutational abundance of <20% was predefined to represent low abundance mutation, that may be subclonal.

Results: PIK3CA mutations were detected with abundance ranging from 80.4% to 0.0063%, with 26 cancers with an abundance >20% and 19 cancers with low abundance <20% (5 cancers with abundance 1-20%, and 14 cancer with abundance <1%). There was highly correlation between repeat experiments r2 = 0.98, p<0.0001, with 100% concordance for low abundance mutations in repeat analysis. High abundance mutations were numerically more common in ER positive HER2 negative cancers (18/65, 28%) than HER2 positive or triple negative (TN) cancers (7/54, 14% p = 0.07 Fishers exact test). Conversely, low abundance mutations were less common in ER positive HER2 negative cancers (4/65, 6%) than in HER2 positive or TN cancers (10/54, 19% p = 0.047). In cancers with a detectable PIK3CA mutation, mutational abundance was higher in ER positive cancer than ER negative cancers (p = 0.023 Mann-Whitney U test), and higher in ER positive HER2 negative cancers compared to HER2 positive or TN cancers (p = 0.0024). In ER positive HER2 negative cancers 82% (18/22) mutations were of high abundance, and likely clonal, whereas in TN or HER2 positive cancers 39% (7/18, p = 0.009) were of high abundance.

Conclusion: Our data suggests that hotspot PIK3CA mutations are frequently of low abundance in HER2 positive or TN breast cancer, and may be subclonal. However, we cannot exclude the possibility that these findings represent contamination. If confirmed on an independent data set, our data suggest that identification of mutational abundance may be an important component of PIK3CA mutation assessment and the potential targeting of these mutations with PI3 kinase inhibitors.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-08-01.

Basal-like breast cancer and the BRCA1 phenotype

Breast cancers arising in germline carriers of BRCA1 mutations have a characteristic phenotype that has been shown in many studies to differentiate BRCA1 tumours from sporadic tumours. Recently, it has become clear that the characteristic phenotype of BRCA1 tumours is due to expression of the basal-like phenotype. We review these phenotypes, the evidence for BRCA1 pathway dysfunction in sporadic basal-like cancers, and discuss the clinical significance of the basal-like phenotype for cancer genetics and treatment.

BRCA1 dysfunction in sporadic basal-like breast cancer

Basal-like breast cancers form a distinct subtype of breast cancer characterized by the expression of markers expressed in normal basal/myoepithelial cells. Breast cancers arising in carriers of germline BRCA1 mutations are predominately of basal-like type, suggesting that BRCA1 dysfunction may play a role in the pathogenesis of sporadic basal-like cancers. We analysed 37 sporadic breast cancers expressing the basal marker cytokeratin 5/6, and age- and grade-matched controls, for downregulation of BRCA1. Although BRCA1 promoter methylation was no more common in basal-like cancers (basal 14% vs controls 11%, P=0.72), BRCA1 messenger RNA expression was twofold lower in basal-like breast cancers compared to matched controls (P=0.008). ID4, a negative regulator of BRCA1, was expressed at 9.1-fold higher levels in basal-like breast cancer (P<0.0001), suggesting a potential mechanism of BRCA1 downregulation. BRCA1 downregulation correlated with the presence of multiple basal markers, revealing heterogeneity in the basal-like phenotype. Finally, we found that 63% of metaplastic breast cancers, a rare type of basal-like cancers, had BRCA1 methylation, in comparison to 12% of controls (P<0.0001). The high prevalence of BRCA1 dysfunction identified in this study could be exploited in the development of novel approaches to targeted treatment of basal-like breast cancer.

Paraneoplastic "stiff person syndrome" with metastatic adenocarcinoma and anti-Ri antibodies

A 43-year-old woman presented with clinical and electrophysiologic features of stiff person syndrome (SPS), without abdominal or lumbar paraspinal muscle involvement. Investigations revealed metastatic adenocarcinoma of the lung with positive anti-Ri antibodies. Her clinical condition improved with diazepam, baclofen, tizanidine, and palliative chemotherapy. Screening for an underlying malignancy and anti-Ri antibodies should be considered in patients with SPS when clinical presentation is atypical.

Hepatitis C and B-cell lymphoma

The association between the hepatitis C virus and B-cell non-Hodgkin's lymphomas is controversial. We review the epidemiological evidence behind the association, and look at the reasons behind the variation in study findings. There is increasing evidence of the pathogenesis of hepatitis C-associated lymphoma. Treatment of the hepatitis C virus with antiviral therapy may lead to the regression of some low-grade lymphomas. The management of other hepatitis C-associated lymphomas is similar to that of conventional lymphoma, although viral reactivation and subsequent immune reconstitution hepatitis can complicate chemotherapy.

An improved heat pulse method to measure low and reverse rates of sap flow in woody plants

The compensation heat pulse method (CHPM) is of limited value for measuring low rates of sap flow in woody plants. Recent application of the CHPM to woody roots has further illustrated some of the constraints of this technique. Here we present an improved heat pulse method, termed the heat ratio method (HRM), to measure low and reverse rates of sap flow in woody plants. The HRM has several important advantages over the CHPM, including improved measurement range and resolution, protocols to correct for physical and thermal errors in sensor deployment, and a simple linear function to describe wound effects. We describe the theory and methodological protocols of the HRM, provide wound correction coefficients, and validate the reliability and accuracy of the technique against gravimetric measurements of transpiration.

Gas exchange by pods and subtending leaves and internal recycling of CO(2) by pods of chickpea (Cicer arietinum L.) subjected to water deficits

Terminal drought markedly reduces leaf photosynthesis of chickpea (Cicer arietinum L.) during seed filling. A study was initiated to determine whether photosynthesis and internal recycling of CO(2) by the pods can compensate for the low rate of photosynthesis in leaves under water deficits. The influence of water deficits on the rates of photosynthesis and transpiration of pods and subtending leaves in chickpea (cv. Sona) was investigated in two naturally-lit, temperature-controlled glasshouses. At values of photosynthetically active radiation (PAR) of 900 micromol m(-2) s(-1) and higher, the rate of net photosynthesis of subtending leaves of 10-d-old pods was 24 and 6 micromol m(-2) s(-1) in the well-watered (WW) and water-stressed (WS) plants when the covered-leaf water potential (Psi) was -0.6 and -1.4 MPa, respectively. Leaf photosynthesis further decreased to 4.5 and 0.5 micromol m(-2) s(-1) as Psi decreased to -2.3 and -3.3 MPa, respectively. At 900--1500 micromol m(-2) s(-1) PAR, the net photosynthetic rate of 10-d-old pods was 0.9-1.0 micromol m(-2) s(-1) in the WW plants and was -0.1 to -0.8 micromol m(-2) s(-1) in the WS plants. The photosynthetic rates of both pods and subtending leaves decreased with age, but the rate of transpiration of the pods increased with age. The rates of respiration and net photosynthesis inside the pods were estimated by measuring the changes in the internal concentration of CO(2) of covered and uncovered pods during the day. Both the WW and WS pods had similar values of internal net photosynthesis, but the WS pods showed significantly higher rates of respiration suggesting that the WS pods had higher gross photosynthetic rates than the WW pods, particularly in the late afternoon. When (13)CO(2) was injected into the gas space inside the pod, nearly 80% of the labelled carbon 24 h after injection was observed in the pod wall in both the WW and WS plants. After 144 h the proportion of (13)C in the seed had increased from 19% to 32% in both treatments. The results suggest that internal recycling of CO(2) inside the pod may assist in maintaining seed filling in water-stressed chickpea.

Acceleration of the development of diabetes in obese diabetic (db/db) mice by nicotinamide: a comparison with its antidiabetic effects in non-obese diabetic mice

Destruction of pancreatic beta cells has been implicted in the progression to hyperglycemia in type 1 diabetes. While there is evidence of beta-cell loss in type 2 diabetes, its contribution to the development of the diabetic state is undecided. Nicotinamide has defensive effects against toxic insults to the pancreatic islets and confers protection in both human and animal models of type 1 diabetes, but its effects on type 2 diabetes are less well documented. This report describes a comparison of the outcome of chronic oral administration of nicotinamide on the development of diabetes in obese diabetic (db/db) and non-obese diabetic (NOD) mice models of type 2 and type 1 diabetes, respectively. Nicotinamide was administered in the diet (5 g/kg diet) for 12 (db/db) or 24 (NOD) weeks. Over the 12 weeks of the study, control diabetic (db/db) mice became progressively more hyperglycemic and glycosuric, while serum and pancreatic insulin levels decreased compared with those on day 0. In mice treated with nicotinamide, there was a pronounced acceleration in the development of hyperglycemia and glycosuria, as well as a decrease in pancreatic insulin levels, compared with time-matched controls. In addition, the morphology of the pancreatic islets of nicotinamide-treated diabetic (db/db) mice showed an enhanced islet disorganization. By comparison, in NOD mice, nicotinamide prevented the decline in serum and pancreatic insulin levels and maintained normal islet architecture and insulin content. Our data shows that in contrast to its preventative effects on the development of autoimmune diabetes in NOD mice, chronic nicotinamide administration to obese diabetic (db/db) mice markedly accelerated the progression of diabetes. The results of our study caution against the use of nicotinamide in insulin-resistant states, such as type 2 diabetes.

Seed coat cell turgor in chickpea is independent of changes in plant and pod water potential

Turgor pressure in cells of the pod wall and the seed coat of chickpea (Cicer arietinum L.) were measured directly with a pressure probe on intact plants under initially dry soil conditions, and after the plants were irrigated. The turgor pressure in cells of the pod wall was initially 0.25 MPa, and began to increase within a few minutes of irrigation. By 2-4 h after irrigation, pod wall cell turgor had increased to 0.97 MPa. This increase in turgor was matched closely by increases in the total water potential of both the pod and the stem, as measured by a pressure chamber. However, turgor pressure in cells of the seed coat was relatively low (0.10 MPa) and was essentially unchanged up to 24 h after irrigation (0.13 MPa). These data demonstrate that water exchange is relatively efficient throughout most of the plant body, but not between the pod and the seed. Since both the pod and the seed coat are vascularized tissues of maternal origin, this indicates that at least for chickpea, isolation of the water relations of the embryo from the maternal plant does not depend on the absence of vascular or symplastic connections between the embryo and the maternal plant.

Insulin resistance, impaired glucose tolerance and non-insulin-dependent diabetes, pathologic mechanisms and treatment: current status and therapeutic possibilities

Impaired glucose tolerance and non-insulin-dependent diabetes (NIDDM) are the pathologic consequence of two co-incident and interacting conditions, namely insulin resistance and relative insulin deficiency. Recognised by the World Health Authority as a global health problem there are at 1995 estimates at least 110 million diagnosed diabetics world wide with at least the same number undiagnosed. Diabetes is the 4th leading cause of death in developed countries and its management exerts a vast economic and social burden. Insulin resistance is established as the characteristic pathologic feature of patients with glucose intolerance and NIDDM describing a state in which insulin stimulated glucose uptake and utilisation in liver, skeletal muscle and adipose tissue is impaired and coupled to impaired suppression of hepatic glucose output. Although the biochemical mechanisms underpinning both defects are becoming better understood, the genetic and molecular causes remain elusive; and whether insulin resistance or relative insulin deficiency represents the primary defect in patients with NIDDM is the matter of some debate. In this article we review the biochemical and molecular nature of the defects in insulin sensitivity and glucose uptake, and discuss some of the potential causative mechanisms. The genetic and environmental basis of insulin resistance is reviewed and presented, and potential therapeutic targets including thiazolidinediones are discussed.

Potential benefit of inhibitors of advanced glycation end products in the progression of type II diabetes: a study with aminoguanidine in C57/BLKsJ diabetic mice

Prolonged hyperglycemia in type II diabetic patients is linked both with diabetic complications and with further impairment of glucose homeostasis, possibly due to glucose toxicity of the beta cell. While the connection between the accumulation of extracellular advanced glycation end products (AGEs) and the development of complications is well established, it has only recently been suggested that intracellular glycation may be equally adverse and could be involved in the pathogenesis of glucose toxicity in vitro. Aminoguanidine is a recognized inhibitor of the formation of both extracellular and intracellular AGEs. In this study, we show that the development of diabetes, measured by increased water intake and concomitant midday blood glucose levels in type II genetically diabetic mice, is reduced by treatment with aminoguanidine at a dosage of 500 mg/kg/d for 12 weeks in the diet. In addition, at the end of the study, aminoguanidine reduced the decline in serum and pancreatic insulin levels and the degree of pancreatic islet morphological degeneration, all of which are associated with pancreatic insufficiency following prolonged hyperglycemia in this animal model. These results suggest that AGEs may be involved in the aggravation of type II diabetes in vivo and aminoguanidine may be beneficial in its treatment.

Peroxisome proliferator-activated receptor-gamma agonist, rosiglitazone, protects against nephropathy and pancreatic islet abnormalities in Zucker fatty rats

Rosiglitazone (BRL 49653), a peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist and potent insulin action-enhancing agent, was given in the diet (50 micromol/kg of diet) to male Zucker rats ages 6-7 weeks for 9 months (prevention group). In this treatment mode, rosiglitazone prolonged the time to onset of proteinuria from 3 to 6 months and markedly reduced the rate of its subsequent progression. Progression was also retarded when treatment was commenced (intervention group) after proteinuria had become established (4 months; ages 24-25 weeks). In either treatment mode, rosiglitazone normalized urinary N-acetyl-beta-D-glucosaminidase activity, a marker for renal proximal tubular damage, and ameliorated the rise in systolic blood pressure that occurred coincidentally with the development of proteinuria in Zucker fatty control rats. The renal protective action of rosiglitazone was verified morphologically. Thus in the prevention group there was an absence of the various indexes of chronic nephropathy that were prominent in the Zucker fatty control group, namely, glomerulosclerosis, dilated tubules containing proteinaceous casts, a loss of functional microvilli on the tubular epithelium, and varying degrees of chronic interstitial nephritis. An intermediate pathology was observed in the intervention group. Also, pancreatic islet hyperplasia, ultrastructural evidence of beta-cell work hypertrophy, and derangement of alpha-cell distribution within the islet were prominent features of Zucker fatty control rats, but these adaptive changes were ameliorated (intervention group) or prevented (prevention group) by rosiglitazone treatment. These data demonstrate that treatment of Zucker fatty rats with rosiglitazone produced substantial protection over a prolonged period against the development and progression of renal injury and the adaptive changes to pancreatic islet morphology caused by sustained hyperinsulinemia.

Elevated renal endothelin-I clearance and mRNA levels associated with albuminuria and nephropathy in non-insulin-dependent diabetes mellitus: studies in obese fa/fa Zucker rats

1. The obese fa/fa Zucker rat is a genetic model of obesity and insulin resistance which develops a number of metabolic and endocrine features of non-insulin-dependent diabetes, including hypertension, proteinuria and glomerular sclerosis. 2. We have investigated the urinary excretion of the metabolites of thromboxane (thromboxane B2) and prostacyclin (6-keto prostaglandin F1 alpha), and of endothelin and cyclic GMP as markers for changes in the balance of renal haemodynamic factors in the obese Zucker rat. 3. Obese fa/fa Zucker rats were hypertensive compared with their lean counterparts (161 +/- 3 and 138 +/- 3 mmHg respectively, P < 0.01); obese animals were also markedly proteinuric (16.7 +/- 6.7 versus 1.1 +/- 0.1 mg/ml) and albuminuric (8.3 +/- 2.9 versus 0.4 +/- 0.25 mg/ml) and excreted less creatinine than lean animals (all P < 0.01). Urinary excretion of endothelin was greater in obese rats (123 +/- 24 versus 62 +/- 10 pg/15 h, P < 0.05) as was the level of pre-proendothelin mRNA, but excretion of cyclic GMP was depressed (12.5 +/- 1.6 versus 27.2 +/- 3.1 nmol/ 15 h, P < 0.01). Histological examination of kidneys from obese animals showed evidence of focal glomerulosclerosis and cortical tubular damage. 4. These results show that increased urinary endothelin is associated with proteinuria and early stage nephropathy in this animal model of non-insulin-dependent diabetes mellitus. This finding, coupled with a decreased excretion of cyclic GMP, suggests that these increased renal vasoconstrictor/vasodilator forces might contribute to the renal functional changes in non-insulin-dependent diabetes mellitus.

Effects of the glucocorticoid II receptor antagonist mifepristone on hypertension in the obese Zucker rat

We have investigated the possible involvement of endogenous corticosteroids in the maintenance of hypertension in aged lean and obese Zucker rats using the type II corticosteroid antagonist mifepristone. At 8 mo of age, the start of the study, obese Zuckers had been hypertensive for at least 2 mo (systolic blood pressure; 153 +/- 4 vs. 136 +/- 5 mmHg; n = 8-9; P < .05) and were hyperinsulinemic (756 +/- 98 vs. 193 +/- 61 microU x ml(-1)) and hypercorticosteronemic (524 +/- 83 vs. 260 +/- 97 ng x ml(-1)) compared to their lean littermates. There were no differences in plasma renin activity between lean and obese animals and plasma renin activity was unaffected by any treatment. Oral treatment of obese rats with mifepristone (40.0 mg x kg(-1) day(-1) for 9 days) resulted in a gradual reduction in SBP to lean levels by day 9. Mifepristone treatment did not affect plasma insulin or corticosterone levels but resulted in a significant reduction in plasma aldosterone concentration. Mifepristone was without significant effect on systolic blood pressure in lean rats. Oral treatment of lean rats with corticosterone-21-acetate (3.0 mg x kg(-1) day(-1) for 9 days) resulted in a rise in systolic blood pressure to levels similar to obese Zuckers after 9 days. Plasma insulin levels were unchanged but corticosterone immunoreactivity was significantly reduced. Plasma aldosterone levels were increased from 564 +/- 3 to 802 +/- 68 pg x ml(-1). Our data suggest that raised glucocorticoids and aldosterone may be factors contributing to hypertension in obesity.

Effects of streptozotocin-induced diabetes on vascular reactivity in genetically hyperinsulinaemic obese Zucker rats

Although the fa/fa Zucker rat shows many of the features of type II diabetes, the absence of consistent cardiovascular complications in this model may be due to the absence of significant hyperglycaemia. We studied the consequences of streptozotocin (STZ)-induced insulin deficiency and hyperglycaemia on vascular reactivity in the fa/fa Zucker rat. Hyperinsulinaemic obese Zucker rats were rendered diabetic by injection of STZ (50-60 mg/kg intraperitoneally, i.p.), and vascular tissue was removed for study 10-12 weeks later. In isolated aorta, there was no difference in the phenylephrine (PE) concentration-response relation between lean and obese control animals, but the concentration-response curve was shifted to the left in diabetic animals, (pD2 7.56 +/- 0.04 in STZ diabetic animals, n = 8; 7.4 +/- 0.04 in obese control, n = 9, p < 0.05). The maximum response was also enhanced in both aorta and perfused mesentery of STZ-treated animals. In contrast, the potency of serotonin (5-HT) in inducing contractions of isolated aorta were enhanced in tissues from obese as compared with lean animals (pD2 6.63 +/- 0.06, n = 9; 6.17 +/- 0.07, n = 7 respectively; p < 0.01) and was attenuated in animals with STZ-induced diabetes (pD2 6.31 +/- 0.09, n = 8, p = 0.05). The differential effects of hyperglycaemia on PE-and 5-HT-induced vasoconstriction suggest that the long-lasting modulation of vasoconstrictor responses induced by increases in blood glucose level may be specific for some agonists.

Plant and soil influences on estimating biomass of wheat in plant breeding plots using field spectral radiometers

Field spectral radiometers were used to estimate the biomass of wheat at early growth stages, as wheat breeders require a rapid, non-destructive technique to rank wheat genotypes for early vigour. Under experimental conditions, good relationships were obtained between reflectance and biomass prior to the wheat crop achieving a green area index of 1.5. When used above different soil types, good results were achieved on very uniform dark and light soils under experimental conditions, but greater differentiation between plots differing in biomass was achieved on darker soils. Similarly, under operational conditions in wheat breeders' plots, the best results were achieved against a dark soil background. Structural differences between plants also influenced solar radiation reflectance. At the Merredin site with the dark soil background, where the best correlation between reflectance and biomass was achieved, the relationship was much stronger for the more uniform genotypes at the second stage of selection than for the more heterogeneous genotypes at the first stage of selection. On these plots, the vegetation spectral indices NDVI (normalised difference vegetation index) and TSAVI (transformed soil-adjusted vegetation index) had a coefficient of determination 90-95% as good as the best regression using two wavebands. To optimise the field spectroradiometry technique for estimating early biomass, it should be applied at a weed-free site, with a uniform dark soil background and on material that is relatively homogenous in structure. We conclude that, unless these precautions are taken, the technique will have limited utility in breeding programs.

Effects of genetic hyperinsulinaemia on vascular reactivity, blood pressure, and renal structure in the Zucker rat

The association between insulin resistance, obesity, and hypertension is well recognised. We examined the hypothesis that hypertension in the obese Zucker rat is related to changes in vascular reactivity. Systolic blood pressure (SBP) in conscious Zucker rats was significantly greater in obese as compared with lean animals (157 +/- 9 and 117 +/- 8 mm Hg). Obese animals also had marked proteinuria and reduced urinary creatinine excretion in 24 h as compared with their lean counterparts. The reactivity of isolated aorta to phenylephrine (PE) and 5-hydroxy-tryptamine (5-HT) was modestly (twofold) increased in obese animals (EC50 13.8 nM as compared with 29.4 nM in lean animals and 0.19 nM as compared with 0.46 nM in lean animals, respectively). In the perfused mesenteric vascular bed, basal perfusion pressure was the same in both phenotypes, as was the pressor response to PE and depressor response to acetylcholine (ACh) and sodium nitroprusside (SNP). In the isolated aorta, from obese animals, insulin attenuated the contractile response to PE but markedly enhanced the vasoconstrictor potency of 5-HT. It had no significant effect on pressor or depressor responses in the perfused mesenteric bed. The data suggest that increased reactivity of central arteries to spasmogenic agents may be involved in the development of systolic hypertension in the hyperinsulinaemic Zucker rat.

Eicosanoid release in allergen-induced bronchoconstriction in dogs. Its relationship to airways hyperreactivity and pulmonary inflammation

In vitro studies have demonstrated the release of histamine, PGD2, TXB2, PGE2, PGF2 alpha, 6-keto-PGF1 alpha and the peptidoleukotrienes from sensitized lung. We have assessed the release of these mediators following antigen challenge in vivo. Antigen challenge of allergic dogs resulted in an acute bronchoconstriction and an increase in bronchial reactivity to histamine and an increase in neutrophil and eosinophil numbers recovered by bronchoalveolar lavage (BAL), 2 and 24 h later. The acute response was associated with histamine and PGD2 release but there was no increase in the levels of other eicosanoids in recovered BAL. Bronchial hyperreactivity and pulmonary inflammation, 2 and 24 h post-challenge was not associated with a concommitant (antigen specific) increase in BAL fluid eicosanoid levels. We conclude that although PGD2 is released during the acute response to antigen the subsequent changes (hyperreactivity and inflammation) are not characterised by a maintained elevation in eicosanoid levels detectable by BAL.

Superoxide generation by guinea-pig peritoneal macrophages is inhibited by rolipram, staurosporine and mepacrine in an agonist-dependent manner

Platelet-activated factor (PAF) (EC50 -7.9 +/- 0.6 M), formyl-methionyl-leucyl-phenylalanine (fMPL) (EC50 -7.7 +/- 0.1M), phorbol 12-myristate 13 acetate (PMA) (EC50 -8.4 +/- 0.3 M), opsonized zymosan (OPZ) (0.01-1 mg/ml) were potent stimuli to superoxide generated by guinea-pig peritoneal macrophages. Superoxide generation by low (< or = -8M) concentrations but not high (> or = -7M) concentrations of PAF or fMLP were attenuated by rolipram (100 microM) in the presence of 1 microM prostaglandin E2 (PGE2). That stimulated by PMA or OPZ, however, was unaffected. At 1 microM, staurosporine was a potent inhibitor of superoxide generation stimulated by both fMLP and PAF but was without effect on that stimulated by OPZ. Superoxide generation stimulated by fMLP, PAF and OPZ was inhibited by 100 microM mepacrine. We conclude that superoxide generation stimulated by the chemoattractants fMLP and PAF involves a cyclic AMP regulated and cyclic AMP independent process. The cyclic AMP independent process is mediated by protein kinase C. Although protein kinase C seems a central element in the respiratory burst stimulated by fMLP, PAF and PMA that stimulated by OPZ bypasses this mechanism. Phospholipase A2 however, represents a common stage in the signal transduction pathway.

Leaf growth, photosynthesis and tissue water relations of greenhouse-grown Eucalyptus marginata seedlings in response to water deficits

Leaf growth, rate of leaf photosynthesis and tissue water relations of shoots of Eucalyptus marginata Donn ex Sm. (jarrah) seedlings were studied during a soil drying and rewatering cycle in a greenhouse experiment. Rates of leaf growth and photosynthesis were sensitive to water deficits. The rate of leaf growth decreased linearly with predawn leaf water potential to reach zero at -1.5 MPa. Rate of leaf growth did not recover completely within the first three days after rewatering. Midday photosynthetic rates declined to 40% of those of well-watered seedlings at a predawn leaf water potential of -1.0 MPa and reached zero at -2.2 MPa. Photosynthetic rate recovered rapidly following rewatering and almost fully recovered by the second day after rewatering. All tissue water relations parameters, except the bulk modulus of elasticity, changed significantly as the soil dried and recovered completely by the third day after rewatering. Changes in osmotic pressure at full turgor of 0.4 MPa indicated considerable capacity for osmotic adjustment. However, because there was little osmotic adjustment until predawn leaf water potential fell below -1.5 MPa, this capacity would not have enhanced seedling growth, although it may have increased seedling survival. The sensitivity of photosynthesis and relative water content to water deficits suggests that greenhouse-grown E. marginata seedlings behave like mesophytic plants, even though E. marginata seedlings naturally grow in a drought-prone environment.

Effects of PAF, FMLP and opsonized zymosan on the release of ECP, elastase and superoxide from human granulocytes

Platelet-activating factor (PAF) is a potent chemoattractant for human eosinophils and neutrophils and causes eosinophil and neutrophil recruitment into animal airways. Since eosinophils and eosinophil cationic proteins are thought to play an important role in the pathophysiology of asthma, we have examined the hypothesis that PAF may also stimulate eosinophil cationic protein (ECP) release from human granulocytes. Granulocytes (93% neutrophils, 3% eosinophils) were isolated from the blood of normal volunteers, using metrizamide density gradients, and stimulated in vitro with PAF, L-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) or opsonized zymosan (OPZ). Superoxide generation was measured colorimetrically, granulocyte degranulation by a fluorimetric assay for elastase, and eosinophil activation by specific radioimmunoassay (RIA) for ECP. Granulocyte chemotaxis was also measured. Whilst both PAF and FMLP were potent chemoattractants for human mixed granulocytes (concentrations producing half the maximal effect (EC50s) ca 10 nM), PAF at concentrations below 10 microM was a poor stimulus to superoxide generation, elastase release or ECP release from the same cell population. In contrast, FMLP was a potent stimulus to both superoxide generation (EC50 48 nM) and ECP (EC50 ca 100 nM) and elastase release (EC50 ca 1 microM). OPZ was a potent stimulus to superoxide generation, but was a poor stimulus to ECP or elastase release. Thus, although PAF is a potent chemoattractant for human granulocytes, our results suggest that it alone may not stimulate their subsequent activation and release of cytotoxic products.

Effects of PAF, FMLP and opsonized zymosan on the release of ECP, elastase and superoxide from human granulocytes

Platelet-activating factor (PAF) is a potent chemoattractant for human eosinophils and neutrophils and causes eosinophil and neutrophil recruitment into animal airways. Since eosinophils and eosinophil cationic proteins are thought to play an important role in the pathophysiology of asthma, we have examined the hypothesis that PAF may also stimulate eosinophil cationic protein (ECP) release from human granulocytes. Granulocytes (93% neutrophils, 3% eosinophils) were isolated from the blood of normal volunteers, using metrizamide density gradients, and stimulated in vitro with PAF, L-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) or opsonized zymosan (OPZ). Superoxide generation was measured colorimetrically, granulocyte degranulation by a fluorimetric assay for elastase, and eosinophil activation by specific radioimmunoassay (RIA) for ECP. Granulocyte chemotaxis was also measured. Whilst both PAF and FMLP were potent chemoattractants for human mixed granulocytes (concentrations producing half the maximal effect (EC50s) ca 10 nM), PAF at concentrations below 10 microM was a poor stimulus to superoxide generation, elastase release or ECP release from the same cell population. In contrast, FMLP was a potent stimulus to both superoxide generation (EC50 48 nM) and ECP (EC50 ca 100 nM) and elastase release (EC50 ca 1 microM). OPZ was a potent stimulus to superoxide generation, but was a poor stimulus to ECP or elastase release. Thus, although PAF is a potent chemoattractant for human granulocytes, our results suggest that it alone may not stimulate their subsequent activation and release of cytotoxic products.

Relaxation of guinea-pig trachea by cyclic AMP phosphodiesterase inhibitors and their enhancement by sodium nitroprusside

1. The effects of agents that elevate either cyclic AMP (the phosphodiesterase (PDE) III inhibitor siguazodan, salbutamol) or cyclic GMP (sodium nitroprusside (SNP)) on the relaxant activity of the PDE IV inhibitor, rolipram, were investigated in carbachol (0.1 microM) precontracted guinea-pig tracheal sheets. 2. Rolipram, siguazodan and SNP caused concentration-related reductions in tone of tissues precontracted with 0.1 microM carbachol (EC50 values 12.5; 2.73 and 0.35 microM respectively). Whilst the concentration-response relationship for the PDE III inhibitor, siguazodan, was monophasic that of the PDE IV inhibitor, rolipram, was biphasic. 3. The relaxant activity of rolipram was markedly enhanced in the presence of 10 microM siguazodan (EC50 < 0.01 microM), 0.1 microM salbutamol (EC50 0.03 microM) and 0.3 microM SNP (EC50 0.03 microM). In contrast, the relaxant activity of siguazodan was unaffected by SNP and only modestly enhanced by rolipram (10 microM) and salbutamol (0.1 microM). 4. The relaxant activity of SNP was enhanced by the PDE V inhibitor SK&F 96231 (30 microM: EC50 0.06 microM) and rolipram (30 microM, EC50 0.08 microM) but was unaffected by 30 microM siguazodan. 5. At concentrations up to 10 microM, neither siguazodan nor rolipram elevated tracheal cyclic AMP levels. However, the combination of 10 microM rolipram and siguazodan caused a two fold increase in the cyclic AMP content (from 2.19 to 4.36 pmol cyclic AMP mg-1 protein). SNP (0.1-10 microM) failed to produce a significant increase in tracheal cyclic AMP levels. At 0.1 microM the effect of SNP on tracheal cyclic AMP levels was significantly (P < 0.05) increased in the presence of rolipram but not siguadozan. 6. The results indicate that the relaxant effects of rolipram are markedly enhanced by agents that inhibit PDE III activity or elevate cyclic GMP. They support the hypothesis that SNP potentiates the effects of rolipram via the inhibitory action of cyclic GMP on hydrolysis of cyclic AMP by PDE III. The findings also suggest that whilst PDE III may be more significant in regulating basal smooth muscle tone in the absence of any exogenous stimulus to cyclic AMP accumulation, PDE IV activity may be more tightly coupled to the pool of adenylyl cyclase stimulated by beta2-adrenoceptor agonists.

Pulmonary effects of type V cyclic GMP specific phosphodiesterase inhibition in the anaesthetized guinea-pig

1. We have investigated the bronchodilator potential of type V phosphodiesterase (PDE V) inhibitors in anaesthetized ventilated guinea-pigs using the potent and selective PDE V inhibitor, SK&F 96231. We have compared its activity to that of salbutamol, the PDE III inhibitors, siguazodan and SK&F 95654 and to the PDE IV inhibitor rolipram. 2. Administered as an i.v. infusion SK&F 96231 (0.6 and 1 mg kg-1 min-1, i.v.) caused a slowly developing inhibition of histamine (100 nmol kg-1, i.v.)-induced bronchoconstriction and elevated tracheal cyclic GMP levels in the anaesthetized guinea-pig. SK&F 96231 (0.1 and 0.3 mg kg-1 min-1, i.v.) was without effect on histamine-induced bronchoconstriction. In the presence of a sub-threshold infusion of SNP (0.1 mumol kg-1 min-1, i.v.) there was a marked enhancement of SK&F 96231-induced inhibition of histamine responses such that at infusion rates that were ineffective alone, SK&F 96231 caused a > 50% inhibition of histamine responses. The stimulation of tracheal cyclic GMP accumulation by SK&F 96231 was also potentiated. 3. Administered directly into the airway, SK&F 96231 (300 micrograms in 5 mg lactose carrier) was largely without effect on histamine-induced bronchoconstriction (4.9 +/- 1.9% inhibition). In the presence of SNP (0.1 mumol kg-1 min-1, i.v.) or isosorbide dinitrate (200 micrograms administered by insufflation into the trachea) there was a marked potentiation of the inhibitory activity of SK&F 96231 (40 +/- 4% and 62 +/- 1.8% respectively). 4. Salbutamol and rolipram (3-300 microg by insufflation) caused a dose-related inhibition of histamine responses with a maximum of 91 +/- 2% and 59 +/- 10% respectively. The PDE III inhibitor, siguazodan,was without effect on histamine responses but they were reduced (27.7 +/- 4.8% at 300 microg) by SK&F95654. There was a marked enhancement of the inhibitory activity of rolipram in the presence of SK&F 95654.5. We conclude that SK&F 96231 has weak anti-spasmogenic activity in the guinea-pig in vivo, we suggest that this is primarily a consequence of a low endogenous guanylate cyclase activity in the airway. The potentiation of the anti-spasmogenic activity of SK&F 96231 by SNP suggests that a combination of PDE V inhibitor and guanylate cyclase agonist might provide significant bronchodilator activity.6. We have established that PDE IV inhibitors are bronchodilators when administered directly into the airway of anaesthetized guinea-pigs but that PDE III inhibitors are only weakly active. The marked enhancement of the inhibitory activity of rolipram by the PDE III inhibitor, SK&F 95654, indicates that inhibitors of both PDE III and PDE IV might offer greater potential as bronchodilators than inhibitors of either isoenzyme alone.

The effect of cyclic AMP and cyclic GMP phosphodiesterase inhibitors on the superoxide burst of guinea-pig peritoneal macrophages

1. The cyclic nucleotide phosphodiesterase (PDE) activity of guinea-pig peritoneal macrophages was partially characterized and the effects of selective and non-selective inhibitors of adenosine 3':5'-cyclic monophosphate (cyclic AMP PDE) and guanosine 3':5'-cyclic monophosphate (cyclic GMP PDE) phosphodiesterases on superoxide generation were investigated using peritoneal macrophages from horse-serum pretreated guinea-pigs. 2. The non-selective PDE inhibitor, 3-isobutyl-1-methylxanthine (IBMX) and the PDE I/V selective inhibitor, zaprinast, inhibited spontaneous superoxide generation with IC50s of 30.7 +/- 11.3 microM and 145 +/- 17 microM respectively (n = 6 and 5). The concentration-response curves for the PDE IV selective inhibitors rolipram and Ro20-1724 were biphasic; mean maximum inhibitions were 56.9 +/- 5.9% and 66.8 +/- 10.5% respectively at 300 microM, but in 2 out of 6 (rolipram) and 2 out of 5 (Ro20-1724) experiments inhibition was < 50%. The PDE III inhibitor SK&F 94120 was without effect. Spontaneous superoxide generation was reduced 57 +/- 10% by 1 microM prostaglandin E2 (PGE2) and 62.6 +/- 3.76% by 1 microM salbutamol. 3. The increase in superoxide generation elicited by FMLP (10(-9)-10(-5)M) was unaffected by any of the PDE inhibitors studied. Inhibition of FMLP-stimulated superoxide generation by PGE2 was enhanced in the presence of 10 microM IBMX. 4. Macrophages were found to contain a predominantly membrane bound cyclic AMP PDE (90% of total activity) which was unaffected by cyclic GMP or calcium/calmodulin. The cyclic AMP PDE activity in the cytosolic fraction was enhanced in the presence of calcium/calmodulin. Selective inhibitors of PDE IV inhibited the particulate cyclic AMP PDE activity (IC50s rolipram 1.5 +/- 0.3 microM, Ro 20-17244.1 +/- 0.6 microm) as did the non-selective inhibitor IBMX (IC50 22 +/- 8 microM). The macrophage particulate PDE activity was resistant to inhibition by the PDE III inhibitor SK&F 94836 and the PDE I/V inhibitor, zaprinast. The cytosolic calcium/calmodulin stimulated cyclic AMP hydrolytic activity was inhibited by zaprinast (IC50 - calcium/calmodulin 123 +/- 39 microM; + calcium/calmodulin IC50 17.7 +/- 6.3 microM).5. The results indicate that guinea-pig peritoneal macrophages contain a type IV cyclic AMP PDE which is predominantly membrane associated and a predominantly cytosolic calcium/calmodulin stimulated cyclic AMP PDE. Functional studies suggest that both of these PDE activities contribute to cyclic AMP hydrolysis and regulation of superoxide generation in these cells. Inhibition of spontaneous superoxide generation, but not that stimulated by FMLP, suggests that the activity of PDE inhibitors is subject to functional antagonism but that this can be overcome by enhancing cyclic AMP formation.

Evaluation of chemical desiccation as a selection technique for drought resistance in a dryland wheat breeding program

Previous studies have shown that some chemical desiccants and senescing agents, when applied to adequately watered cereals 10 to 14 days after anthesis, can be used to select lines with stable grain size (kernel weight) under post-anthesis water deficits. The present study evaluated the potential of one of these chemicals, potassium iodide (KI), to select for this character in a dryland wheat breeding program. Ninety-six F2-derived lines grown in the F6and F7 generations and 11 cultivars of wheat (Triticum aestzvum L.) were grown in two experiments at two medium-rainfall sites in 1988 and 1989 and sprayed with a 0.3% solution of KI when the grains had developed one-third in the lemma. Reductions in grain yield and thousand kernel weight due to treatment with KI were greater in 1988 than in 1989, probably due to the higher growing-season rainfall in that year. The reduction in grain yield as a result of desiccation was greater than the reduction in thousand kernel weight, but the correlation between the two was low (0.09 to 0.58) and non-significant in five out of the eight comparisons. There were considerable differences among genotypes in response to the desiccation treatment in the wetter 1988. Genetic coefficients of variation ranged from 5.6 to 12.9% for yield and 2.5 to 9.5% for thousand kernel weight. The ratio of the variance component estimates for the interaction between genotypes and desiccation treatment to the variance component estimates for genotypes was generally less than one. However, genetic differences in response to the desiccation treatment could be demonstrated in some experiments, particularly at one site and in the wetter of the two years. We conclude that the chemical desiccation technique can be used to select for post-anthesis drought resistance in a dryland breeding program. However, there are some limitations to the technique, and selection needs to be confined to wetter sites and seasons.

Potential of using field spectroscopy during early growth for ranking biomass in cereal breeding trials

The use of field spectroscopy for the non-destructive ranking of cereal breeding plots at the early stages of crop growth was investigated using measurements of spectral reflectance over 222 wavebands between 400 and 2500 nm using the single beam GEOSCAN Portable Field Spectroradiometer (PFS). Measurements were made on 54 barley plots at the 5- and 7-leaf stages of growth with biomass varying between 10 and 96 g/m2. The optimal multiple linear regression relationship between reflectance and biomass included wavebands from the near-infrared (NIR) and mid-infrared (MIR) with a standard deviation of 4.8 g/m2. The ranking of plots according to biomass by this optimal relationship or the Simple Ratio of NIR to visible (VIS) reflectance, which is a common index of greeness, agreed closely with actual ranking. Tested against an independent set of wheat plots at the 4-leaf stage with biomass ranging from 3 to 32 g/m2, the barley-derived relationship, but not the Simple Ratio, performed poorly in ranking plots according to biomass. However, at the 7-leaf growth stage, when the biomass range had increased to 48-117 g/m2, both the Simple Ratio and the barley-derived relationship agreed closely with the actual ranking. To apply these results in practice, the accuracy of the simpler CROPSCAN portable field radiometer (PFR) was found to be greater than the GEOSCAN PFS for comparable NIR and VIS wavebands. It was therefore concluded that it is practically feasible to use field spectroscopy to rank cereal plots for biomass at early growth stages where the difference between plots is of the order of 5-7 gm/m2. Such biomass differences were more apparent at the 7-leaf than 4-leaf stage of growth.

Characterization of the antagonist activity of the PAF antagonists RP 59227 and WEB 2086 on elicited guinea pig peritoneal macrophages. Evidence for variable affinities and kinetics

The pharmacological selectivity and affinity of the two PAF antagonists RP 59227 and WEB 2086 for macrophage platelet activating factor (PAF) receptors have been investigated. PAF produced a dose-related increase in superoxide generation from elicited guinea pig peritoneal macrophages (IC50 41 +/- 16 nM, n = 9). After a 5 min preincubation time RP 59227 (0.1, 1.0 and 10 microM) produced a dose-related rightward displacement of the PAF dose-response curve, the Schild plot gave a pA2 of 7.39 +/- 0.07 (n = 5) with a slope of 1.17 +/- 0.11, indicating competitive antagonism. WEB 2086 over the same concentration range was without effect at the lower two concentrations, but at 10 microM, the displacement of the PAF dose-response curve was similar to that obtained with 10 microM RP 59227. Increasing the preincubation time to 30 min increased the affinity of RP 59227 (apparent pA2 8.76 +/- 0.28, n = 5). This was associated with a reduction in the slope of the Schild plot to 0.67 +/- 0.11, suggesting noncompetitive kinetics. The affinity of WEB 2086 could not be determined, but the antagonism appeared noncompetitive in nature. The results indicate that PAF antagonists can show variable affinities for macrophage PAF receptors depending on the experimental conditions, as well as competitive or noncompetitive kinetics depending on the contact time.