Diversity of US participants in AstraZeneca-sponsored clinical trials

BACKGROUND

To develop medicines that are safe and efficacious to all patients, clinical trials must enroll appropriate target populations, but imbalances related to race, ethnicity and sex have been reported. A comprehensive analysis and improvement in understanding representativeness of patient enrollment in industry-sponsored trials are key public health needs.

METHODS

We assessed race/ethnicity and sex representation in AstraZeneca (AZ)-sponsored clinical trials in the United States (US) from 2010 to 2022, compared with the 2019 US Census.

RESULTS

In total, 246 trials representing 95,372 patients with complete race/ethnicity and sex records were analyzed. The proportions of different race/ethnicity subgroups in AZ-sponsored clinical trials and the US Census were similar (White: 69.5% vs 60.1%, Black or African American: 13.3% vs 12.5%, Asian: 1.8% vs 5.8%, Hispanic: 14.4% vs 18.5%). We also observed parity in the proportions of males and females between AZ clinical trials and US Census (males: 52.4% vs 49.2%, females: 47.6% vs 50.8%). Comparisons of four distinct therapy areas within AZ (Respiratory and Immunology [R&I]; Cardiovascular, Renal, and Metabolism [CVRM]; Solid Tumors; and Hematological Malignancies), including by trial phases, revealed greater variability, with proportions observed above and below US Census levels.

CONCLUSION

This analysis provides the first detailed insights into the representativeness of AZ trials. Overall, the proportions of different race/ethnicity and sex subgroups in AZ-sponsored clinical trials were broadly aligned with the US Census. We outline some of AZ's planned health equity initiatives that are intended to continue to improve equitable patient enrollment.

A View on Drug Development for Cancer Prevention

Despite some notable successes, there are still relatively few agents approved for cancer prevention. Here we review progress thus far in the development of medicines for cancer prevention, and we outline some key concepts that could further enable or accelerate drug development for cancer prevention in the future. These are summarized under six key themes: (i) unmet clinical need, (ii) patient identification, (iii) risk stratification, (iv) pharmacological intervention, (v) clinical trials, and (vi) health care policy. These concepts, if successfully realized, may help to increase the number of medicines available for cancer prevention.

SIGNIFICANCE

The huge potential public health benefits of preventing cancer, combined with recent advances in the availability of novel early detection technologies and new treatment modalities, has caused us to revisit the opportunities and challenges associated with developing medicines to prevent cancer. Here we review progress in the field of developing medicines to prevent cancer to date, and we present a series of ideas that might help in the development of more medicines to prevent cancer in the future.

Comorbidity between lung cancer and COVID-19 pneumonia: role of immunoregulatory gene transcripts in high ACE2-expressing normal lung

BACKGROUND

SARS-CoV-2 (COVID-19) elicits a T-cell antigen-mediated immune response of variable efficacy. To understand this variability, we explored transcriptomic expression of angiotensin-converting enzyme 2 (ACE2, the SARS-CoV-2 receptor) and of immunoregulatory genes in normal lung tissues from patients with non-small cell lung cancer (NSCLC).

METHODS

This study used the transcriptomic and the clinical data for NSCLC patients generated during the CHEMORES study [n = 123 primary resected (early-stage) NSCLC] and the WINTHER clinical trial (n = 32 metastatic NSCLC).

RESULTS

We identified patient subgroups with high and low ACE2 expression (p = 1.55 × 10^-19) in normal lung tissue, presumed to be at higher and lower risk, respectively, of developing severe COVID-19 should they become infected. ACE2 transcript expression in normal lung tissues (but not in tumor tissue) of patients with NSCLC was higher in individuals with more advanced disease. High-ACE2 expressors had significantly higher levels of CD8+ cytotoxic T lymphocytes and natural killer cells but with presumably impaired function by high Thymocyte Selection-Associated High Mobility Group Box Protein TOX (TOX) expression. In addition, immune checkpoint-related molecules - PD-L1, CTLA-4, PD-1, and TIGIT - are more highly expressed in normal (but not tumor) lung tissues; these molecules might dampen immune response to either viruses or cancer. Importantly, however, high inducible T-cell co-stimulator (ICOS), which can amplify immune and cytokine reactivity, significantly correlated with high ACE2 expression in univariable analysis of normal lung (but not lung tumor tissue).

CONCLUSIONS

We report a normal lung immune-tolerant state that may explain a potential comorbidity risk between two diseases - NSCLC and susceptibility to COVID-19 pneumonia. Further, a NSCLC patient subgroup has normal lung tissue expressing high ACE2 and high ICOS transcripts, the latter potentially promoting a hyperimmune response, and possibly leading to severe COVID-19 pulmonary compromise.

Transcriptomics in Tumor and Normal Lung Tissues Identify Patients With Early-Stage Non-Small-Cell Lung Cancer With High Risk of Postsurgery Recurrence Who May Benefit From Adjuvant Therapies

PURPOSE

The prognosis of patients with non-small-cell lung cancer (NSCLC), traditionally determined by anatomic histology and TNM staging, neglects the biological features of the tumor that may be important in determining patient outcome and guiding therapeutic interventions. Identifying patients with NSCLC at increased risk of recurrence after curative-intent surgery remains an important unmet need so that known effective adjuvant treatments can be offered to those at highest risk of recurrence.

METHODS

Relative gene expression level in the primary tumor and normal bronchial tissues was used to retrospectively assess their association with disease-free survival (DFS) in a cohort of 120 patients with NSCLC who underwent curative-intent surgery.

RESULTS

Low versus high Digital Display Precision Predictor (DDPP) score (a measure of relative gene expression) was significantly associated with shorter DFS (highest recurrence risk; P = .006) in all patients and in patients with TNM stages 1-2 (P = .00051; n = 83). For patients with stages 1-2 and low DDPP score (n = 29), adjuvant chemotherapy was associated with improved DFS (P = .0041). High co-overexpression of CTLA-4, PD-L1, and ICOS in normal lung (28 of 120 patients) was also significantly associated with decreased DFS (P = .0013), suggesting an immune tolerance to tumor neoantigens in some patients. Patients with DDPP low and immunotolerant normal tissue had the shortest DFS (P = 2.12E-11).

CONCLUSION

TNM stage, DDPP score, and immune competence status of normal lung are independent prognostic factors in multivariate analysis. Our findings open new avenues for prospective prognostic assessment and treatment assignment on the basis of transcriptomic profiling of tumor and normal lung tissue in patients with NSCLC.

The Porto European Cancer Research Summit 2021

Key stakeholders from the cancer research continuum met in May 2021 at the European Cancer Research Summit in Porto to discuss priorities and specific action points required for the successful implementation of the European Cancer Mission and Europe's Beating Cancer Plan (EBCP). Speakers presented a unified view about the need to establish high-quality, networked infrastructures to decrease cancer incidence, increase the cure rate, improve patient's survival and quality of life, and deal with research and care inequalities across the European Union (EU). These infrastructures, featuring Comprehensive Cancer Centres (CCCs) as key components, will integrate care, prevention and research across the entire cancer continuum to support the development of personalized/precision cancer medicine in Europe. The three pillars of the recommended European infrastructures - namely translational research, clinical/prevention trials and outcomes research - were pondered at length. Speakers addressing the future needs of translational research focused on the prospects of multiomics assisted preclinical research, progress in Molecular and Digital Pathology, immunotherapy, liquid biopsy and science data. The clinical/prevention trial session presented the requirements for next-generation, multicentric trials entailing unified strategies for patient stratification, imaging, and biospecimen acquisition and storage. The third session highlighted the need for establishing outcomes research infrastructures to cover primary prevention, early detection, clinical effectiveness of innovations, health-related quality-of-life assessment, survivorship research and health economics. An important outcome of the Summit was the presentation of the Porto Declaration, which called for a collective and committed action throughout Europe to develop the cancer research infrastructures indispensable for fostering innovation and decreasing inequalities within and between member states. Moreover, the Summit guidelines will assist decision making in the context of a unique EU-wide cancer initiative that, if expertly implemented, will decrease the cancer death toll and improve the quality of life of those confronted with cancer, and this is carried out at an affordable cost.

Rethinking Cancer Clinical Trial Conduct Induced by COVID-19: An Academic Center, Industry, Government, and Regulatory Agency Perspective

The COVID-19 pandemic brought about major changes in cancer clinical trials. In its aftermath, the community has an opportunity to incorporate some of these changes as part of the future of trial conduct to make it more patient centered.

Antibiotic use towards the end of life: development of good practice recommendations

OBJECTIVES

Development of evidence-based good practice recommendations for clinicians considering the use of antibiotics in patients towards the end of life.

DESIGN

A multiprofessional group of experts in end-of-life care and antimicrobial stewardship was convened. Findings from a scoping review of the literature and a consultation of clinicians were triangulated. Expert discussion was used to generate consensus on how to approach decision-making.

SETTING

Representatives from hospital and a range of community health and care settings.

PARTICIPANTS

Medical, pharmacy and nursing professionals.

MAIN OUTCOME MEASURES

Good practice recommendations based on published evidence and the experience of prescribers in Scotland.

RESULTS

The findings of 88 uncontrolled, observational studies of variable quality were considered alongside a survey of over 200 prescribers. No national or international guidelines were identified. Antibiotic use towards the end of life was common but practice was highly variable. The potential harms associated with giving antibiotics tended to be less well considered than the potential benefits. Antibiotics often extended the length of time to death but this was sometimes at the cost of higher symptom burden. There was strong consensus around the importance of effective communication with patients and their families and making treatment decisions aligned to a patient's goals and priorities.

CONCLUSIONS

Good practice recommendations were agreed with focus on three areas: making shared decisions about future care; agreeing clear goals and limits of therapy; reviewing all antibiotic prescribing decisions regularly. These will be disseminated widely to support optimal care for patients towards the end of life. A patient version of the recommendations has also been produced to support implementation.

Report from the SWOG Radiation Oncology Committee: Research Objectives Workshop 2017

The Radiation Therapy Committee of SWOG periodically evaluates its strategic plan in an effort to maintain a current and relevant scientific focus, and to provide a standard platform for future development of protocol concepts. Participants in the 2017 Strategic Planning Workshop included leaders in cancer basic sciences, molecular theragnostics, pharmaceutical and technology industries, clinical trial design, oncology practice, and statistical analysis. The committee discussed high-priority research areas, such as optimization of combined modality therapy, radiation oncology-specific drug design, identification of molecular profiles predictive of radiation-induced local or distant tumor responses, and methods for normal tissue-specific mitigation of radiation toxicity. The following concepts emerged as dominant questions ready for national testing: (i) what is the role of radiotherapy in the treatment of oligometastatic, oligorecurrent, and oligoprogressive disease? (ii) How can combined modality therapy be used to enhance systemic and local response? (iii) Can we validate and optimize liquid biopsy and other biomarkers (such as novel imaging) to supplement current response criteria to guide therapy and clinical trial design endpoints? (iv) How can we overcome deficiencies of randomized survival endpoint trials in an era of increasing molecular stratification factors? And (v) how can we mitigate treatment-related side effects and maximize quality of life in cancer survivors? The committee concluded that many aspects of these questions are ready for clinical evaluation and example protocol concepts are provided that could improve rates of cancer cure and quality of survival. Clin Cancer Res; 24(15); 3500-9. ©2018 AACR.

A simplified interventional mapping system (SIMS) for the selection of combinations of targeted treatments in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a leading cause of death worldwide. Targeted monotherapies produce high regression rates, albeit for limited patient subgroups, who inevitably succumb. We present a novel strategy for identifying customized combinations of triplets of targeted agents, utilizing a simplified interventional mapping system (SIMS) that merges knowledge about existent drugs and their impact on the hallmarks of cancer. Based on interrogation of matched lung tumor and normal tissue using targeted genomic sequencing, copy number variation, transcriptomics, and miRNA expression, the activation status of 24 interventional nodes was elucidated. An algorithm was developed to create a scoring system that enables ranking of the activated interventional nodes for each patient. Based on the trends of co-activation at interventional points, combinations of drug triplets were defined in order to overcome resistance. This methodology will inform a prospective trial to be conducted by the WIN consortium, aiming to significantly impact survival in metastatic NSCLC and other malignancies.

The changing world of oncology drug development-A global pharmaceutical company's perspective

Recent approvals for oncology drugs have seen an increasing proportion directed to specific genetic targets identified with an associated companion diagnostic test. In addition, there is a wave of drugs directed against immune 'checkpoints' which promise to transform the way cancer is treated in the next decade. We can increase the probability of success in drug development based on a thorough mechanistic understanding of how a target drug affects cancer biology and the specific biological and genotypic context in which it operates. This article compares and contrasts the discovery and development of gefitinib-the first EGFR tyrosine kinase inhibitor and AZD9291, an irreversible inhibitor of both sensitizing and resistant mutated EGFR. This demonstrates how the better understanding we now have of the genetic changes driving the cancer growth and the biochemical structure and function of the mutated proteins, has led to a much faster developmental path with higher likelihood of success in pivotal trials. An emerging trend in response to the challenge of the increasing segmentation of cancers based on their genetic makeup is the development of 'basket' studies which include one or more screening tests for multiple genetic aberrations and the direction of patients to one of several arms of a clinical trial based on the specific aberration in their tumor. In the face of both the wealth of genetic information about cancer and the challenges of drug development, collaboration across academia and industry is vital. There is great potential to benefit from more 'open innovation' to address some of these challenges and opportunities. Far from there being a decline in innovation in pharmaceutical development, I see that we are in one of the most exciting times in cancer drug development with innovation in every aspect of how we discover and develop new therapies.

Correlates and characteristics of hepatitis C virus-specific T-cell immunity in exposed uninfected high-risk prison inmates

Some hepatitis C (HCV)-uninfected, high-risk individuals have HCV-specific cellular immunity without viraemia or seroconversion. The characteristics of these responses and the risk behavioural associations were studied in 94 subjects in a prospective cohort of recently seronegative prisoners reporting injecting drug use (IDU). Detailed behavioural data were collected. HCV antibody and PCR testing were performed. ELISpot assays for HCV-induced interferon (IFN)-γ and interleukin (IL)-2 production by T lymphocytes, as well as multiplex in vitro cytokine production assays, were performed. Seventy-eight subjects remained antibody and PCR negative and 16 seroconverted. Of the seronegative group, 22 (28%) had IFN-γ ELISpot responses in comparison with 13 of the 16 seroconverters (82%). This seronegative immune status was associated positively with injecting anabolic steroids and negatively with a recent break from IDU. The IFN-γ ELISpot responses involved both CD4 and CD8 T lymphocytes and were comparable in magnitude, but narrower in specificity, in uninfected subjects than in seroconverters. A subset of seronegative subjects had HCV-induced cytokine production patterns comparable with the seroconverters with increased production of IFN-γ, IL-2 and tumour necrosis factor (TNF)-α and reduced IL-10 in response to nonstructural peptides. In conclusion, comparable patterns of HCV-specific cellular immunity are found in recently infected subjects and in a minority of high-risk, uninfected subjects. Further characterization of these responses and their protective efficacy will inform HCV vaccine development.

Detection of herpes viruses in the cerebrospinal fluid of adults with suspected viral meningitis in Malawi

PURPOSE

We looked for herpes simplex virus types 1 and 2 (HSV-1 and HSV-2, respectively), varicella zoster virus (VZV), Epstein-Barr virus (EBV) and cytomegalovirus (CMV) DNA in Malawian adults with clinically suspected meningitis.

METHODS

We collected cerebrospinal fluid (CSF) from consecutive adults admitted with clinically suspected meningitis to Queen Elizabeth Central Hospital (QECH), Blantyre, Malawi, for a period of 3 months. Those with proven bacterial or fungal meningitis were excluded. Real-time polymerase chain reaction (PCR) was performed on the CSF for HSV-1 and HSV-2, VZV, EBV and CMV DNA.

RESULTS

A total of 183 patients presented with clinically suspected meningitis. Of these, 59 (32 %) had proven meningitis (bacterial, tuberculous or cryptococcal), 39 (21 %) had normal CSF and 14 (8 %) had aseptic meningitis. For the latter group, a herpes virus was detected in 9 (64 %): 7 (50 %) had EBV and 2 (14 %) had CMV, all were human immunodeficiency virus (HIV)-positive. HSV-2 and VZV were not detected. Amongst those with a normal CSF, 8 (21 %) had a detectable herpes virus, of which 7 (88 %) were HIV-positive.

CONCLUSIONS

The spectrum of causes of herpes viral meningitis in this African population is different to that in Western industrialised settings, with EBV being frequently detected in the CSF. The significance of this needs further investigation.

Phase I dose-escalation study to determine the safety, pharmacokinetics and pharmacodynamics of brivanib alaninate in combination with full-dose cetuximab in patients with advanced gastrointestinal malignancies who have failed prior therapy

Background:

The objectives of this phase I study were to determine the safety, pharmacokinetics (PK), pharmacodynamics and efficacy of brivanib combined with full-dose cetuximab in patients with advanced gastrointestinal malignancies.

Methods:

Patients with advanced gastrointestinal malignancies who had failed prior therapies received brivanib (320, 600 or 800 mg daily) plus cetuximab (400 mg m^–2 loading dose then 250 mg m^–2 weekly). Assessments included adverse events, PK, tumour response, 2[18F]fluoro-2-deoxyglucose positron-emitting tomography and K-Ras mutation analyses.

Results:

Toxicities observed were manageable; the most common treatment-related toxicities (>10% of patients) were fatigue, diarrhoea, anorexia, increase in aspartate aminotransferase and alanine aminotransferase, acneiform dermatitis, headache, mucosal inflammation, nausea, dry skin, vomiting, hypertension, pruritus, proteinuria and weight loss. Of 62 patients, 6 (9.7%) had objective radiographic partial responses, with an overall response rate of 10%. Median duration of response was 9.2 months; median progression-free survival was 3.9 months.

Conclusions:

The acceptable toxicity profile and efficacy of brivanib observed in this study were promising. These findings are being further evaluated in a phase III study of brivanib plus cetuximab vs cetuximab alone in patients previously treated with combination chemotherapy for K-Ras wild-type advanced metastatic colorectal cancer.

A phase I study to determine the safety, pharmacokinetics and pharmacodynamics of a dual VEGFR and FGFR inhibitor, brivanib, in patients with advanced or metastatic solid tumors

BACKGROUND

This study was designed to determine the safety, pharmacokinetics (PK) and pharmacodynamics (PD) of brivanib in patients with advanced/metastatic solid tumors.

PATIENTS AND METHODS

Ninety patients enrolled in this two-part, phase I open-label study of oral brivanib alaninate. The primary objectives of this study were (in part A) dose-limiting toxicity, maximum tolerated dose (MTD) and the lowest biologically active dose level and (in part B) the optimal dose/dose range. The secondary objectives of this study were preliminary evidence of antitumor activity, PK and PD.

RESULTS

Across part A (open-label dose escalation and MTD) and part B (open-label dose optimization), 68 patients received brivanib alaninate. Brivanib demonstrated a manageable toxicity profile at doses of 180-800 mg. Most toxic effects were mild. Systemic exposure of the active moiety brivanib increased linearly ≤1000 mg/day. The MTD was 800 mg/day. Forty-four patients were treated at the MTD: 20 with 800 mg continuously, 11 with 800 mg intermittently and 13 with 400 mg b.i.d. doses. Partial responses were confirmed in two patients receiving brivanib ≥600 mg. Dynamic contrast-enhanced magnetic resonance imaging demonstrated statistically significant decreases in parameters reflecting tumor vascularity and permeability after multiple doses in the 800-mg continuous q.d. and 400-mg b.i.d. dose cohorts.

CONCLUSION

In patients with advanced/metastatic cancer, brivanib demonstrates promising antiangiogenic and antitumor activity and manageable toxicity at doses ≤800 mg orally q.d., the recommended phase II study dose.

Blockade of cytotoxic T-lymphocyte antigen-4 by ipilimumab results in dysregulation of gastrointestinal immunity in patients with advanced melanoma

Blockade of cytotoxic T-lymphocyte antigen-4 (CTLA-4) by ipilimumab leads to immune-mediated tumor regression and immune-related adverse events (irAEs), including diarrhea and colitis. The current analyses were undertaken to promote an understanding of the underlying mechanism of action and to identify potential biomarkers that could help in the prediction and management of ipilimumab-induced gastrointestinal irAEs. Treatment-naïve or previously treated patients with unresectable stage III/IV melanoma (n = 115) received open-label ipilimumab (10 mg/kg every 3 weeks for four doses) and were randomized to receive concomitant blinded prophylactic oral budesonide (9 mg/d with gradual taper through week 16) or placebo. Outcome measures included histologic assessment of bowel biopsies and assessment of serologic markers of inflammatory bowel disease (IBD), fecal calprotectin levels, and polymorphisms in immune-related genes. Ipilimumab resulted in dysregulation of gastrointestinal mucosal immunity as evidenced by altered antibody levels to enteric flora, inflammatory cell infiltration into gastrointestinal mucosa, and increased fecal calprotectin associated with diarrhea and clinical evidence of colitis. The pattern of ipilimumab-induced antibody titers to microbial flora and the histologic features and location of the inflammation were distinct from classic IBD. Prophylactic budesonide did not prevent ipilimumab-induced bowel inflammation. Despite an observed association between colonic inflammation and grade 2 or higher diarrhea, no baseline biomarkers could reliably predict development of gastrointestinal toxicity. Although classic IBD and ipilimumab-related gastrointestinal toxicity are both immune mediated, the observed pattern of biomarkers suggests ipilimumab-related gastrointestinal toxicity may be a distinct clinicopathologic entity.

Optimization of donor management goals yields increased organ use

Multiple strategies have been used in an effort to increase the pool of organs for transplantation. Standardizing donor management has produced promising results. Donor management goals (DMGs) are now being used as end points of intensive care unit care during the prerecovery phase but no prospective results have been reported. Data from the United Network for Organ Sharing Region 11 were collected for successful achievement of eight common donor management goals (mean airway pressure [MAP], central venous pressure [CVP], pH, PaO2, sodium, glucose, single pressor use, and urine output) before organ recovery. Two time periods were studied with different panels of DMGs. The analysis identified the success rate of transplantation. Goals were stratified by their statistical correlation with the number of organs transplanted per donor (OTPD) in an effort to identify the most important parameter(s). Eight hundred five organ donors were studied with 2685 organs transplanted. DMGs were assessed through two phases of the study. Achieving DMGs rose from 18 to 66 per cent associated with significant improvement in OTPD (range, 2.96 to 3.45). The success of transplantation was primarily associated with limitations in vasopressor use and PaO2. Tight glucose control did affect the rate of pancreatic transplants. Thoracic organs were the most sensitive to DMGs with a 10- to 15-fold increase in lung transplantation when PaO2 rose above 100 mmHg. MAP, CVP, pH, sodium, and urine output had little effect on transplantation. Standardization of end points of donor management was associated with increased rates of transplantation. Surprisingly, not all standard goals are necessary for optimal organ use. The most significant parameters were the low use of vasopressor agents and oxygenation. Donor management strategies should strive to optimize these goals.

Abstract B195: Synergy between ixabepilone (Ixa) and trastuzumab (TZ): Investigation of the role of microtubule-associated protein (MAP-tau) and III tubulin (βIII) in HER2-positive (HER2+) breast cancer (BC)

Background and rationale: Historically, patients with aggressive HER2+ BC have a poor response to chemotherapy, including antimicrotubule agents. Elevated III levels have been reported in HER2+ BC. Introduction of the HER2+ targeted agent TZ, in combination with taxane based chemotherapy, greatly improved the outcomes of these patients. The novel antimicrotubule agent Ixa has broad preclinical and clinical efficacy in BC tumors, including those that overexpress III, a predictor of taxane resistance. Previous reports in BC cell lines and tumors have shown an inverse correlation between Ixa/taxane sensitivity and MAP-tau. We set out to evaluate the activity of Ixa in combination with TZ and explore the relationship between III and MAPtau expression and Ixa response in HER2+ BC. Here we provide preclinical evidence of synergy with Ixa plus TZ and preclinical and clinical evidence of the contribution of MAP-tau and III in HER2+ BC.

Methods: In preclinical studies with HER2+ human BC cell lines BT-474 and KPL-4 the effects of drug exposure were determined by a vital dye uptake assay (MTS) or a colony formation assay. Gene (Affymetrix HG U133A v2.0 Gene Chips) and protein expression (immunoblotting) changes in cells exposed to TZ or estradiol (E2; control) were assessed. BT-474 and KPL-4 subcutaneous tumors in mice were also assessed. Using intrinsic gene clustering, microarray expression data from 134 breast tumors from the Ixa monotherapy neoadjuvant BC trial CA163-080 (080) were subtyped as HER2-enriched, basal-, luminal- or normal-like, and III/MAP-tau expression was assessed by subtype.

Results: Ixa exhibited synergistic activity in combination with TZ in vitro (HER2+ BT-474 cell line). Synergy was also demonstrated in BT-474 and KPL-4 human BC xenografts in mice; 75% complete response (CR) was achieved in BT-474, compared with 0% CR and 25% partial response (PR) with Ixa alone, and 0% CR and 0% PR with TZ alone. Exposure of BT-474 cells to TZ for 24 hours caused down regulation of MAP-tau, relative to E2. Analysis of clinical tumor samples from 080 demonstrated that HER2-enriched tumors have elevated III, but reduced MAP-Tau levels relative to luminal-like and normal-like subtypes (P<0.0001).

Conclusions: Ixa and TZ demonstrated synergy in HER2+ BC models. The ability of TZ to down regulate MAP-tau may explain, at least partially, the synergistic activity seen in the clinical setting when TZ is combined with antimicrotubule agents. Retrospective analysis of the 080 trial revealed that III was over- and MAP-tau was under-expressed, in HER2-enriched tumors relative to other BC subtypes. In two Phase 2 studies, Ixa was safe and effective when combined with TZ for the treatment of HER2+ BC patients. This data supports further exploration of III/MAP-tau expression and Ixa response in HER2+ BC in the clinical setting.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B195.

Association of baseline and on-study tumor biopsy markers with clinical activity in patients (pts) with advanced melanoma treated with ipilimumab

9008

Background: Ipilimumab is a fully human monoclonal antibody to cytotoxic T-lymphocyte antigen-4. Identifying predictive markers may help select advanced melanoma pts most likely to benefit from ipilimumab therapy. Biomarkers in the tumor microenvironment are thought to be more relevant for predicting response than those in the peripheral blood. Methods: We examined tumor biopsy markers in a Phase II study CA184004 (ipilimumab 3 and 10 mg/kg). Ipilimumab was administered every 3 weeks (Q3W) x 4; eligible pts could receive ipilimumab Q12W starting Wk 24. Pre- and post-treatment (Wk 4) tumor biopsies were performed for hematoxylin and eosin analysis of tumor-infiltrating lymphocytes (TILs); immunohistochemistry of FOXP3 and indoleamine 2,3-dioxygenase (IDO); and mRNA expression profile analysis. Response was assessed with modified World Health Organization criteria. Associations between tumor biomarkers and clinical activity (complete response, partial response, or stable disease ≥ 24 wks) were assessed. Results: Ipilimumab 3 or 10 mg/kg was administered to 40 and 42 pts, respectively. In tumor biopsies, clinical activity was associated with high expression of FOXP3 (P = 0.014) and IDO (P = 0.012) at baseline and an increase from baseline in TILs (Wk 4) (P = 0.005) ( Table ). Tumor mRNA profiling identified genes with significant changes from baseline in expression, or with baseline expression levels that may be associated with clinical activity. These included various immune response genes and known melanoma antigens. Conclusions: Biomarkers in the tumor microenvironment have been demonstrated to be associated with clinical activity in pts treated with ipilimumab.

[Table: see text]

[Table: see text]

High β-III tubulin expression in triple-negative (TN) breast cancer (BC) subtype and correlation to ixabepilone response: A retrospective analysis

3587

Background: High βIII-tubulin (βIII) expression confers resistance to many anti-microtubule agents (Sève, Lancet 2008; 9: 168). The anti-microtubule agent ixabepilone (Ixa) demonstrates efficacy in βIII over-expressing tumor models resistant to taxanes and has clinical activity in patients with TN BC. The incidence and expression of βIII by BC subtype have not been delineated. Methods: Retrospective analyses of βIII mRNA expression were conducted in two microarray datasets of BC cohorts. Using intrinsic gene clustering, BC tumors from the Ixa neoadjuvant study CA163–080 (080) and the International Genome Consortium (IGC) were defined as basal-like (BL), luminal-like, Her2-overexpressing (Her2+) or normal-like subtypes. For study 080, IHC status subtyping defined TN, Her2+ and Her2-ER+PR+ patients. Mean expression of TUBB3, the gene encoding for βIII, was determined for each subtype. Clinical responses for 080 patients were compared to βIII expression levels. Results: For both cohorts, mean expression of TUBB3 was higher in BL and Her2+ tumors (one-way ANOVA and Tukey's HSD test; both p < 0.001). TUBB3 expression was rank-ordered: low, medium and high. In 080 and IGC cohorts, high expressors represent >50% of patients in BL and Her2+ subtypes and ∼20% of other BC subtypes. Subtyping 080 patients by receptor expression status demonstrated mean TUBB3 expression was higher for TN compared to Her2+ and Her2-ER+PR+ patients (t-test; p = 0.009). TN patients (n = 11/46) in study 080 had a trend to higher pCR rate than the overall population (n = 29/161), 26 vs. 18%. Receiver operating characteristics (ROC) analysis with AUC=0.66 demonstrates that high TUBB3 expression may predict for Ixa response in the overall 080 population. Conclusions: BC patients with TN, BL and Her2+ tumors have higher βIII expression. For the 080 study, responses to Ixa were higher for TN BC patients, and ROC analysis correlated response to βIII levels in the overall population. These data suggest high βIII in BL and TN BC may contribute to the aggressiveness of these subtypes and predict for Ixa clinical response. Additional studies are needed to address the activity of taxanes relative to βIII expression in TN BC.

[Table: see text]

Repeatability of [18F] fluoro-deoxyglucose positron emission tomography (FDG-PET) in a multicenter phase I oncology study in patients with gastrointestinal malignancies

2530

Background: FDG-PET is used to monitor response in multi-center oncology clinical trials. This study assessed the repeatability of select semi-quantitative standardized uptake values (SUV) as measured by double baseline FDG-PET studies in a multi-center phase I oncology trial. Methods: Double baseline FDG-PET studies were acquired on 62 sequentially enrolled patients. Tumor metabolic activity was assessed by SUVmean, SUVmax, SUVpeak and SUV70%. Compliance with image acquisition guidelines and quality assurance (QA) standards were assessed as to their effect on SUV repeatability. Summary statistics for baseline absolute differences relative to the average of baseline values and repeatability analysis were performed for all patients (full dataset) and a subset with scans that passed QA (QA dataset), analyzed in both a multi-observer (site-reported) and single-observer (central-read) setting. Intra-subject precision of baseline measurements was assessed by repeatability coefficients, intra-subject coefficients of variation, and confidence intervals for all SUV parameters. Results: No statistically significant difference was noted between the two baseline measurements for any of the SUV parameters. Mean baseline differences for SUVmean, SUVmax, SUVpeak and SUV70% were not statistically significant for either dataset, in the multi- or the single-observer setting. The intra-subject coefficient of variation of the SUV parameters ranged from 11–14% (QA dataset) to 16% (full dataset). The 95% repeatability coefficients for individual patient differences, ranged from (-25%, 34%) to (-34%, 52%) for all SUV parameters. Conclusions: Repeatability results of double baseline FDG-PET scans were similar for all SUV parameters assessed in a variety of analysis settings. The variability was acceptable even in the absence of close compliance with current consensus recommendations, supporting the use of FDG-PET imaging as a robust tumor assessment tool in multi-center oncology clinical trials. The results of this study suggest thresholds for determining metabolic response may be on the order of -35%, 50%, allowing increased confidence that a true change from baseline has occurred.

[Table: see text]

Phase II genomics study of ixabepilone as neoadjuvant treatment for breast cancer

PURPOSE

This phase II study evaluated the efficacy and safety of ixabepilone as neoadjuvant therapy for invasive breast cancer not amenable to breast conservation surgery. Gene expression studies were undertaken using genes that were identified as potentially associated with sensitivity/resistance to ixabepilone in prior preclinical investigations.

PATIENTS AND METHODS

Patients with invasive breast cancer >or= 3 cm were eligible. Ixabepilone 40 mg/m(2) was administered as a 3-hour intravenous infusion on day 1 of a 21-day cycle for four or fewer cycles.

RESULTS

One hundred sixty-one patients were treated. The overall complete pathologic response (pCR) rate was 18% in breast and 29% in estrogen receptor (ER) -negative patients. Gene expression data were available for 134 patients. ER gene expression (ER1) was inversely related to pCR in breast and had a positive predictive value (PPV) of 37% and negative predictive value (NPV) of 92%. A 10-gene penalized logistic regression (PLR) model developed from 200 genes predictive of ixabepilone sensitivity in preclinical experiments included ER and tau and had higher PPV (45%) and comparable NPV (89%) to ER1. Grade 3 to 4 adverse events (AEs) were reported for 32% of patients. Except for neutropenia and leukopenia, all grade 3 to 4 AEs occurred in <or= 3% of patients. Reversible peripheral neuropathy was experienced by 3% of patients. CONCLUSION ER, microtubule-associated protein tau, and a 10-gene PLR model that included ER were identified as predictors of ixabepilone-induced pCR.

RESULTS

indicate an inverse relation between ER expression levels and ixabepilone sensitivity. Neoadjuvant ixabepilone demonstrated promising activity and a manageable safety profile in patients with invasive breast tumors.

Metabolism and disposition of dasatinib after oral administration to humans

SPRYCEL (dasatinib, BMS-354825; Bristol-Myers Squibb, Princeton, NJ), a multiple kinase inhibitor, is currently approved to treat chronic myelogenous leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia tumors in patients who are resistant or intolerant to imatinib mesylate (Gleevec; Novartis, Basel, Switzerland). After a 100-mg single p.o. dose of [(14)C]dasatinib to healthy volunteers, the radioactivity was rapidly absorbed (T(max) approximately 0.5 h). Both dasatinib and total radioactivity (TRA) plasma concentrations decreased rapidly with elimination half-life values of <4 h. Dasatinib was the major drug-related component in human plasma. At 2 h, dasatinib accounted for 25% of the TRA in plasma, suggesting that metabolites contributed significantly to the total drug-related component. There were many circulating metabolites detected that included hydroxylated metabolites (M20 and M24), an N-dealkylated metabolite (M4), an N-oxide (M5), an acid metabolite (M6), glucuronide conjugates (M8a,b), and products of further metabolism of these primary metabolites. Most of the administered radioactivity was eliminated in the feces (85%). Urine recovery accounted for <4% of the dose. Dasatinib accounted for <1 and 19% of the dose in urine and feces, respectively, suggesting that dasatinib was well absorbed after p.o. administration and extensively metabolized before being eliminated from the body. The exposures of pharmacologically active metabolites M4, M5, M6, M20, and M24 in patients, along with their cell-based IC(50) for Src and Bcr-Abl kinase inhibition, suggested that these metabolites were not expected to contribute significantly toward in vivo activity.

A phase I study of BMS-582664 (brivanib alaninate), an oral dual inhibitor of VEGFR and FGFR tyrosine kinases, in patients (pts) with advanced/metastatic solid tumors: Safety, pharmacokinetic (PK), and pharmacodynamic (PD) findings

3559

Background: Brivanib is an oral prodrug of BMS-540215, a dual tyrosine kinase inhibitor of VEGFR and FGFR signaling. Part A of this study defined an MTD of 800 mg qd (Abstract # 3051, ASCO 2006). Part B investigated expanded doses / schedules for safety, PK and PD. Methods: In Part B, sequential cohorts were treated with 320 mg qd, 800 mg 5 days on/2 off (800I), 800 mg qd (800C), or 400 mg bid. Available data are reported for pts treated at these doses in Part A + B. PK samples were obtained Days 1, 8 and 26. Tumor DCE- MRI parameters, transfer constant (Ktrans), area under the concentration-time curve - first 60 s post contrast injection (AUC60) were measured baseline X 2, Days 2, 8 and 26. Reproducibility was assessed by within pt %CV (wCV). Exposure-response analysis was performed using logistic regression. Serum ELISAs for soluble VEGFR2 and Collagen IV were measured at baseline, Days 8 and 26. Results: Fourteen, 9 and 18 pts were treated at 320, 800I and 800C, respectively. G3/4 AEs at 320, 800I, and 800C respectively were fatigue (21%, 0%, 22%), ↑ transaminase (8%, 11%, 17%), diarrhea (0%, 11%, 11%), hypertension (0%, 0%, 11%), platelets (8%, 0%, 11%). 800C had the greatest change in Ktrans, AUC60 and serum markers at Day 8 and 26 ( Table ). 800I had some recovery Day 2 to Day 8 and a smaller change at Day 26 than 800C. wCV for Ktrans and AUC60 was 26% and 22% respectively. The probability of DCE-MRI change increased with exposure (AUCtau) to BMS-540215. Conclusions: Brivanib has dose-proportional PK and a tolerable safety profile = 800C. PD changes were greatest at 800C. Some recovery in DCE-MRI effect after 2 day dosing break suggests continuous dosing is preferable for biological activity.

[Table: see text]

No significant financial relationships to disclose.

Human mass balance study of the novel anticancer agent ixabepilone using accelerator mass spectrometry

Ixabepilone (BMS-247550) is a semi-synthetic, microtubule stabilizing epothilone B analogue which is more potent than taxanes and has displayed activity in taxane-resistant patients. The human plasma pharmacokinetics of ixabepilone have been described. However, the excretory pathways and contribution of metabolism to ixabepilone elimination have not been determined. To investigate the elimination pathways of ixabepilone we initiated a mass balance study in cancer patients. Due to autoradiolysis, ixabepilone proved to be very unstable when labeled with conventional [¹⁴C]-levels (100 μCi in a typical human radio-tracer study). This necessitated the use of much lower levels of [¹⁴C]-labeling and an ultra-sensitive detection method, Accelerator Mass Spectrometry (AMS). Eight patients with advanced cancer (3 males, 5 females; median age 54.5 y; performance status 0–2) received an intravenous dose of 70 mg, 80 nCi of [¹⁴C]ixabepilone over 3 h. Plasma, urine and faeces were collected up to 7 days after administration and total radioactivity (TRA) was determined using AMS. Ixabepilone in plasma and urine was quantitated using a validated LC-MS/MS method. Mean recovery of ixabepilone-derived radioactivity was 77.3% of dose. Fecal excretion was 52.2% and urinary excretion was 25.1%. Only a minor part of TRA is accounted for by unchanged ixabepilone in both plasma and urine, which indicates that metabolism is a major elimination mechanism for this drug. Future studies should focus on structural elucidation of ixabepilone metabolites and characterization of their activities.

Predictive biomarker discovery and validation for the targeted chemotherapeutic ixabepilone

3011

Background: Ixabepilone is a microtubule stabilizing agent with significant therapeutic value in breast cancer (BC) patients. To identify predictive biomarkers capable of identifying patients likely to receive optimal benefit from ixabepilone treatment, preclinical and clinical studies were carried out. Several biomarkers discovered using preclinical models were validated in a neoadjuvant BC clinical study ( CA163080 ) and one, estrogen receptor 1 (ER), was shown to double the pathological complete response (pCR) rate in patients treated with ixabepilone. To identify candidate sets of biomarkers that could further increase the pCR rate we have performed post-hoc analyses of the preclinical and clinical data. Methods: Eighteen BC cell lines were classified as sensitive or resistant (S/R) based on the IC50 values for ixabepilone treatment. Gene expression profiling of the BC cell lines was conducted and genes correlated with the S/R classification were identified using a k-Nearest Neighbors algorithm. Patients in clinical study CA163080 underwent a pretreatment core needle biopsy from which RNA was isolated and gene expression profiles generated (data available on 134 patients). Analyses using the preclinical and clinical markers were conducted using various statistical tools. Results: Several markers used in combination with ER were found to be capable of tripling the pCR to ixabepilone in CA163080. In addition to ER other predictive markers were identified that were as predictive as ER, including several genes whose expression is anti-correlated with ER and are part of the ER pathway. Finally, various sub-group analyses were performed and manifested the importance of clinical sample variation that needs to be considered for the analysis. Conclusions: Several single biomarkers identified from preclinical studies were validated in the clinical study CA163080 , demonstrating the utility of this approach. Such markers can be used in combination to better identify patients likely to respond to ixabepilone in future clinical trials. Furthermore, molecular response markers that can be tied to the mechanism of drug resistance can be used for further developing chemotherapy in drug development.

[Table: see text]

The relationship between alcohol and head injury and its effect on the conscious level

The incidence of head injury has risen in recent years and now accounts for almost one-third of acute male surgical admissions to the Western Infirmary, Glasgow. A prospective study has established that in Glasgow alcohol is a major associated factor, 62 per cent of males and 27 per cent of females having detectable levels in the blood (&gt; 5 mg/100 ml); in these patients the mean level was 193 mg/100 ml in men and 165 mg/100ml in women. The alcohol level was significantly higher in patients who had had ‘a fall under the influence’, or had been the victims of assault, than in those involved in traffic or other accidents. This suggests that alcohol may be an important contributory cause of head injuries in this city. Depression of the conscious level occurred at blood alcohol levels around 200 mg/ 100 ml, but a significant number of patients in coma had a serious head injury.

Randomized phase III study of matrix metalloproteinase inhibitor BMS-275291 in combination with paclitaxel and carboplatin in advanced non-small-cell lung cancer: National Cancer Institute of Canada-Clinical Trials Group Study BR.18

PURPOSE

To determine whether BMS-275291, a broad-spectrum matrix metalloproteinase inhibitor (MMPI), added to systemic chemotherapy improved survival in advanced non-small-cell lung cancer (NSCLC). In early phase studies, BMS- 275291 was not associated with dose-limiting joint toxicity seen with other MMPIs.

PATIENTS AND METHODS

Chemotherapy-naive patients with stage IIIB/IV NSCLC, performance status (PS) 0 to 2, and adequate organ function were eligible. All patients received paclitaxel 200 mg/m2 plus carboplatin (area under the curve, 6 mg/mL-min) intravenously every 21 days for up to 8 cycles, and were randomly assigned to receive BMS-275291, 1,200 mg orally daily, or placebo until disease progression. The primary study end point was survival (OS); secondary end points included progression-free survival (PFS), response rates (RR), toxicity, and quality of life.

RESULTS

From 2000 to 2002, 774 patients were randomly assigned. Pretreatment characteristics were well balanced between arms: median age, 61 years; male sex, 73%; stage IV, 79%; PS 0 to 1, 88%. Interim safety analysis revealed no survival advantage and increased toxicity in the experimental arm, and study treatment was stopped. Median OS, PFS and RR in the final analysis in the BMS-275291 arm were 8.6 months, 4.9 months, and 25.8% respectively, and in the control arm 9.2 months, 5.3 months, 33.7%. Toxicity was significantly higher in the BMS-275291 arm, including flu-like symptoms, rash, hypersensitivity reactions (8.6% v 2.4%), and febrile neutropenia (9.7% v 5.5%).

CONCLUSION

BMS-275291 added to chemotherapy increases toxicity and does not improve survival in advanced NSCLC.

A randomized phase II feasibility trial of BMS-275291 in patients with early stage breast cancer

PURPOSE

This pilot trial was performed to evaluate the safety, pharmacokinetics and feasibility of incorporating BMS-275291, a matrix metalloproteinase inhibitor (MMPI), into adjuvant breast cancer therapy.

EXPERIMENTAL DESIGN

Patients with stage I (T1c)-IIIA breast cancer were eligible if planned adjuvant therapy consisted of either tamoxifen alone, doxorubicin + cyclophosphamide every 21 days for four cycles (AC), or AC followed by paclitaxel every 21 days for 4 cycles (AC>T). Patients were stratified by planned adjuvant therapy and randomized (2:1 ratio) to BMS-275291 (1200 mg/day) or matched placebo for 1 year.

RESULTS

Seventy-two patients were recruited from March 2001 to July 2002. Grade >or=2 musculoskeletal toxicity, generally reversible arthralgia, was reported by 36.2% of patients receiving BMS-275291 compared with 16.7% of patients receiving placebo; difference = 19.5% (95% confidence interval: -0.06, 0.44; P = NS). Two patients receiving BMS-275291 developed palpable nodules along tendons. Grade >or=3 rash was reported by 8.5% of patients receiving BMS-275291 compared with 4.2% of patients receiving placebo; difference = 4.3% (95% confidence interval: -0.18, 0.3; P = NS). Overall, 33% of BMS-275291 patients and 21% of placebo patients discontinued treatment due to adverse events. BMS-275291 trough levels tended to decrease over time; 9 of 47 (19%) had >or=50% of trough concentrations > 124 ng/ml (IC(90) for matrix metalloproteinase-9).

CONCLUSIONS

The pattern of arthralgia in BMS-275291-treated patients was consistent with matrix metalloproteinase inhibitor toxicity. Although the differential incidence of arthralgia did not reach statistical significance, the trial was terminated. An adjuvant trial in this patient population is not feasible.

5,6-dimethylxanthenone-4-acetic acid (DMXAA), a novel antivascular agent: phase I clinical and pharmacokinetic study

The purpose of this phase I, dose-escalation study was to determine the toxicity, maximum tolerated dose, pharmacokinetics, and pharmacodynamic end points of 5,6-dimethylxanthenone acetic acid (DMXAA). In all, 46 patients received a total of 247 infusions of DMXAA over 15 dose levels ranging from 6 to 4900 mg x m(-2). The maximum tolerated dose was established at 3700 mg x m(-2); dose-limiting toxicities in the form of urinary incontinence, visual disturbance, and anxiety were observed at the highest dose level (4900 mg x m(-2)). The pharmacokinetics of DMXAA were dose dependent. Peak concentrations and area under the curve level increased from 4.8 microM and 3.2 microM h, respectively, at 6 mg x m(-2) to 1290 microM and 7600 microM h at 3700 mg x m(-2), while clearance declined from 7.4 to 1.7 l h(-1) x m(-2) over the same dose range. The terminal half-life was 8.1+/-4.3 h. More than 99% of the drug was protein bound at doses up to 320 mg x m(-2); at higher doses the percent free drug increased to a maximum of 6.9% at 4900 mg x m(-2). Dose-dependent increases in the serotonin metabolite 5-hydroxyindoleacetic acid were observed at dose levels of 650 mg x m(-2) and above. There was one unconfirmed partial response at 1300 mg x m(-2). In conclusion, DMXAA is a novel vascular targeting agent and is well tolerated.

Endothelin-B receptors in cerebral resistance arterioles and their functional significance after focal cerebral ischemia in cats

In the cerebral circulation, endothelin-A receptor activation mediates marked prolonged vasoconstriction whereas endothelin-B (ETB) receptor activation effects dilation. In contrast to some peripheral vascular beds, ET(B) receptor-induced vasoconstriction has not yet been demonstrated in brain vessels. In this study in chloralose-anesthetized cats, with perivascular microapplications of ET(B) selective agonist (BQ-3020) and antagonist (BQ-788), we investigated whether ET(B) receptor-mediated constriction could be uncovered in cortical arterioles in vivo. In addition, we examined whether normal dilator response to ET(B) receptor activation is preserved in postischemic cerebral arterioles. The first microapplication of the selective ET(B) receptor agonist BQ-3020 (1 micromol/L) onto a pial cortical arteriole elicited marked dilation (caliber increased by 26.3 +/- 15.1% from preinjection baseline). A second application of BQ-3020 (10-minute interval) onto the same vessel failed to evoke any significant vasomotor response. Subsequent (third and fourth) adventitial microapplication of the ET(B) receptor agonist on the same arteriolar site effected a significant constriction of cerebral arterioles (-15.3 +/- 12.7% and -9.7 +/- 6.3% from preinjection baseline, respectively, at 20 and 30 minutes after the first application). The pial arterioles did not display tachyphylaxis to repeated applications of potassium (10 mmol/L). The perivascular application of the ET(B) receptor antagonist BQ-788 (0.001 to 1 micromol/L) had no effect on arteriolar caliber per se but blocked both BQ-3020-induced dilation (inhibitory concentration approximately 5 nmol/L) and vasoconstriction elicited by repeated activation of ET(B) receptors. After middle cerebral artery occlusion, most of the arterioles examined displayed a sustained dilation. The microapplication of BQ-3020 into the perivascular space surrounding postischemic dilated arterioles elicited a constriction of a similar magnitude to that induced by application of CSF (-17 +/- 7% and -17 +/- 7% from preinjection baseline, respectively). The adventitial microapplication of the ET(B) receptor antagonist (BQ-788, 0.1 micromol/L) on postocclusion dilated pial arterioles effected no change in the arteriolar caliber when compared with preinjection baseline. This BQ-788-induced response was significantly different from that induced by perivascular microinjection of CSF (P < 0.001, analysis of variance). These investigations indicate that (1) repeated activation of ET(B) receptors displays tachyphylaxis of the vasodilator response but also uncovers significant constriction of cerebral arterioles in vivo; (2) the ability of BQ-3020 to elicit dilation is lost within 30 minutes of induced focal ischemia; and (3) ET(B)-mediated contractile tone contributes in a small but significant manner in limiting postischemia dilation of cortical pial arterioles.

Endothelin receptor antagonist increases cerebral perfusion and reduces ischaemic damage in feline focal cerebral ischaemia

These investigations characterised the cerebrovascular effects of an endothelin ETA-receptor antagonist PD156707 in normal and ischaemic cat brain. A dose of PD156707 that inhibited the effects of exogenous endothelin-1 was established in nonischaemic cerebral resistance arterioles. Perivascular microapplication of the endothelin-receptor antagonist PD156707 (0.03-3 microM) had a minimal effect on nonischaemic pial resistance arterioles. The perivascular co-application of PD156707 and ET-1 (10 nM) effected a dose-dependent attenuation of the ET-1 vasoconstrictive response (IC50 = 0.1 microM). Intravenous administration of PD156707 (3 mumol/kg bolus + 5 mumol/kg/h infusion) attenuated the vasoconstriction elicited by perivascular ET-1 (10 nM) in normal pial arterioles (ET-1 vasoconstriction: -37 +/- 13% from preinjection baseline; after intravenous PD156707: 6 +/- 10% from preinjection baseline). In the focal ischaemia studies, cerebral perfusion was measured in the suprasylvian and ectosylvian gyri (by laser Doppler flowmetry). Occlusion of the middle cerebral artery reduced cerebral perfusion in the suprasylvian and ectosylvian gyri by approximately 50%. Intravenous administration of PD156707 (3 mumol/kg bolus + 5 mumol/kg/h infusion), initiated 30 min after middle cerebral artery occlusion, effected a progressive increase in cerebral perfusion up to preocclusion baseline levels, whereas cerebral perfusion in vehicle-treated animals did not vary from its postocclusion level. In these animals, the intravenous administration of PD156707 reduced the hemispheric volume of ischaemic damage by 45% (vehicle: 2,376 +/- 1,107 mm3; PD156707: 1,307 +/- 548 mm3; p < 0.05). Our investigations indicate that endothelin receptor antagonism may be a new therapeutic strategy for the amelioration of focal ischaemic damage.

Endothelin-mediated vascular tone following focal cerebral ischaemia in the cat

The actions of Bosentan and PD155080, nonpeptide endothelin receptor antagonists, were examined in feline pial arterioles in situ following middle cerebral artery (MCA) occlusion to gain insight into the cerebrovascular influence of endogenous endothelins in focal cerebral ischaemia. Immediately following permanent MCA occlusion, all pial arterioles overlying the suprsylvian and ectosylvian gyri displayed marked dilatations, which were maintained in a population of vessel but differentiated into sustained constrictions in others. Perivascular subarachnoid microinjections of Bosentan (30 microM), PD155080 (30 microM), and artificial CSF (pH 7.2) were performed between 30 and 210 min following MCA occlusion. The perivascular microapplication of Bosentan (30 microM) and PD155080 (30 microM) around pial vessels overlying the suprasylvian and ectosylvian gyri, which are within the territory of the occluded MCA, elicited in increase in the calibre of postocclusion dilated and constricted pial arterioles. The perivascular microapplication of PD155080 (30 microM) around postocclusion constricted arterioles overlying the ectosylvian and suprasylvian gyri elicited an increase in the calibre of arterioles (69 +/- 49% from preinjection baseline; n = 8). The perivascular microapplication of Bosentan (30 microM) around postocclusion constricted arterioles overlying the ectosylvian and suprasylvian gyri also elicited an increase in the calibre of arterioles (68 +/- 60% from preinjection baseline; n = 13). In contrast, the microapplication of CSF (pH 7.2) elicited small reductions in pial arteriolar calibre of postocclusion constricted arterioles (-8 +/- 13% from preinjection baseline; n = 8). The perivascular microapplication of PD155080 (30 microM) around postocclusion dilated pial arterioles overlying the ectosylvian and suprasylvian gyri elicited an increase in the calibre of arterioles (11 +/- 10% from preinjection baseline; n = 38). The perivascular microapplication of Bosentan (30 microM) around postocclusion dilated arterioles elicited an increase in the calibre of arterioles (16 +/- 15% from preinjection baseline; n = 36). In contrast, the microapplication of CSF (pH 7.2) elicited small reductions in pial arteriolar calibre of postocclusion dilated arterioles (-9 +/- 6% from preinjection baseline; n = 44). Perivascular microapplication of Bosentan or PD155080 had minimal effect on the calibre of pial arterioles on the parasagittal gyrus (anterior cerebral artery territory), although these arterioles had also displayed sustained dilatation following MCA occlusion. These results indicate that contractile factors (whose effects can be reversed with endothelin receptor antagonists) constrict or impair dilatation of cortical resistance arterioles in an acute cerebral ischaemic episode.