Association of PD-L1 Expression on Tumor and Immune Cells with Survival in Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma and Assay Validation.

Programmed cell death ligand-1 (PD-L1), expressed on both tumor cells (TC) and tumor-associated immune cells (IC), has been shown to be a useful biomarker and predictive of response to anti-PD-L1 agents in certain tumor types. In recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC), there is a growing interest in the role of PD-L1 expression on ICs, as well as TCs, for predicting response to immune checkpoint inhibitors. Using pooled data from the phase II HAWK and CONDOR studies, we investigated the association of baseline PD-L1 expression with durvalumab efficacy in patients with R/M HNSCC. To determine an optimal PD-L1 cut-off point for predicting survival, we assessed PD-L1 expression levels at different TC and IC cut-off points in patients treated with durvalumab. Longer survival was associated with higher TC membrane PD-L1 expression and IC staining. When the combined TC/IC algorithm was applied, a cut-off point for PD-L1 expression of ≥50% on TCs or ≥25% on ICs (TC ≥ 50%/IC ≥ 25%) showed a higher objective response rate (17.2% vs. 8.8%), longer median progression-free survival (2.8 vs. 1.9 months), and longer median overall survival (8.4 vs. 5.4 months) in the PD-L1-high versus PD-L1-low/negative patient populations, respectively. A scoring algorithm combining PD-L1 expression on TCs and ICs using the cut-off point TC ≥ 50%/IC ≥ 25% was optimal for identifying patients with HNSCC most likely to benefit from durvalumab treatment. The new algorithm is robust and can be reproducibly scored by trained pathologists. Significance: A novel algorithm for PD-L1 expression using the cut-off point TC ≥ 50%/IC ≥ 25% is robust for identifying patients with HNSCC most likely to benefit from durvalumab treatment and can be reproducibly scored by trained pathologists.

Curative-Intent Treatment with Durvalumab in Early-Stage Cancers.

The introduction of immunotherapy has fundamentally transformed the treatment landscape in cancer, providing long-term survival benefit for patients with advanced disease across multiple tumor types, including non-small cell lung cancer (NSCLC). In the placebo-controlled phase 3 PACIFIC trial, the PD-L1 inhibitor durvalumab demonstrated significant improvements in progression-free survival and overall survival in patients with unresectable, stage III NSCLC who had not progressed after platinum-based chemoradiotherapy (CRT). These findings have led to the widespread acceptance of the 'PACIFIC regimen' (durvalumab after CRT) as the standard of care in this setting. Moreover, the PACIFIC trial is the first study to demonstrate a proven survival advantage with an immunotherapy in a curative-intent setting, thereby providing a strong rationale for further investigation of durvalumab in early-stage cancers. Herein, we describe the extensive clinical development program for durvalumab across multiple tumor types in curative-intent settings, outlining the scientific rationale(s) for its use and highlighting the innovative research (e.g., personalized cancer monitoring) advanced by these trials.

SUPREME-HN: a retrospective biomarker study assessing the prognostic value of PD-L1 expression in patients with recurrent and/or metastatic squamous cell carcinoma of the head and neck.

BACKGROUND: Programmed cell death ligand-1 (PD-L1) expression on tumor cells (TCs) is associated with improved survival in patients with head and neck squamous cell carcinoma (HNSCC) treated with immunotherapy, although its role as a prognostic factor is controversial. This study investigates whether tumoral expression of PD-L1 is a prognostic marker in patients with recurrent and/or metastatic (R/M) HNSCC treated with standard chemotherapy. METHODS: This retrospective, multicenter, noninterventional study assessed PD-L1 expression on archival R/M HNSCC tissue samples using the VENTANA PD-L1 (SP263) Assay. PD-L1 high was defined as PD-L1 staining of ≥ 25% TC, with exploratory scoring at TC ≥ 10% and TC ≥ 50%. The primary objective of this study was to estimate the prognostic value of PD-L1 status in terms of overall survival (OS) in patients with R/M HNSCC. RESULTS: 412 patients (median age, 62.0 years; 79.9% male; 88.2% Caucasian) were included from 19 sites in seven countries. 132 patients (32.0%) had TC ≥ 25% PD-L1 expression; 199 patients (48.3%) and 85 patients (20.6%) had TC ≥ 10% and ≥ 50%, respectively. OS did not differ significantly across PD-L1 expression (at TC ≥ 25% cutoff median OS: 8.2 months vs TC < 25%, 10.1 months, P = 0.55) or the ≥ 10% and ≥ 50% cutoffs (at TC ≥ 10%, median OS: 9.6 months vs TC < 10%, 9.4 months, P = 0.32, and at TC ≥ 50%, median OS 7.9 vs TC < 50%, 10.0 months, P = 0.39, respectively). CONCLUSIONS: PD-L1 expression, assessed using the VENTANA PD-L1 (SP263) Assay, was not prognostic of OS in patients with R/M HNSCC treated with standard of care chemotherapies. Trial registration ClinicalTrials.gov, NCT02543476. Registered September 4, 2015.

Safety and Efficacy of Durvalumab With or Without Tremelimumab in Patients With PD-L1-Low/Negative Recurrent or Metastatic HNSCC: The Phase 2 CONDOR Randomized Clinical Trial.

Importance: Dual blockade of programmed death ligand 1 (PD-L1) and cytotoxic T-lymphocyte associated protein 4 (CTLA-4) may overcome immune checkpoint inhibition. It is unknown whether dual blockade can potentiate antitumor activity without compromising safety in patients with recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC) and low or no PD-L1 tumor cell expression. Objective: To assess safety and objective response rate of durvalumab combined with tremelimumab. Design, Setting, and Participants: The CONDOR study was a phase 2, randomized, open-label study of Durvalumab, Tremelimumab, and Durvalumab in Combination With Tremelimumab in Patients With R/M HNSCC. Eligibility criteria included PD-L1-low/negative disease that had progressed after 1 platinum-containing regimen in the R/M setting. Patients were randomized (N = 267) from April 15, 2015, to March 16, 2016, at 127 sites in North America, Europe, and Asia Pacific. Interventions: Durvalumab (20 mg/kg every 4 weeks) + tremelimumab (1 mg/kg every 4 weeks) for 4 cycles, followed by durvalumab (10 mg/kg every 2 weeks), or durvalumab (10 mg/kg every 2 weeks) monotherapy, or tremelimumab (10 mg/kg every 4 weeks for 7 doses then every 12 weeks for 2 doses) monotherapy. Main Outcomes and Measures: Safety and tolerability and efficacy measured by objective response rate. Results: Among the 267 patients (220 men [82.4%]), median age (range) of patients was 61.0 (23-82) years. Grade 3/4 treatment-related adverse events occurred in 21 patients (15.8%) treated with durvalumab + tremelimumab, 8 (12.3%) treated with durvalumab, and 11 (16.9%) treated with tremelimumab. Grade 3/4 immune-mediated adverse events occurred in 8 patients (6.0%) in the combination arm only. Objective response rate (95% CI) was 7.8% (3.78%-13.79%) in the combination arm (n = 129), 9.2% (3.46%-19.02%) for durvalumab monotherapy (n = 65), and 1.6% (0.04%-8.53%) for tremelimumab monotherapy (n = 63); median overall survival (95% CI) for all patients treated was 7.6 (4.9-10.6), 6.0 (4.0-11.3), and 5.5 (3.9-7.0) months, respectively. Conclusions and Relevance: In patients with R/M HNSCC and low or no PD-L1 tumor cell expression, all 3 regimens exhibited a manageable toxicity profile. Durvalumab and durvalumab + tremelimumab resulted in clinical benefit, with minimal observed difference between the two. A phase 3 study is under way. Trial Registration: clinicaltrials.gov Identifier: NCT02319044.

Durvalumab for recurrent or metastatic head and neck squamous cell carcinoma: Results from a single-arm, phase II study in patients with ≥25% tumour cell PD-L1 expression who have progressed on platinum-based chemotherapy.

BACKGROUND: Patients with recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC) progressing on platinum-based chemotherapy have poor prognoses and limited therapeutic options. Programmed cell death-1 (PD-1) and its ligand 1 (PD-L1) are frequently upregulated in HNSCC. The international, multi-institutional, single-arm, phase II HAWK study (NCT02207530) evaluated durvalumab monotherapy, an anti-PD-L1 monoclonal antibody, in PD-L1-high patients with platinum-refractory R/M HNSCC. PATIENTS AND METHODS: Immunotherapy-naïve patients with confirmed PD-L1-high tumour cell expression (defined as patients with ≥25% of tumour cells expressing PD-L1 [TC ≥ 25%] using the VENTANA PD-L1 [SP263] Assay) received durvalumab 10 mg/kg intravenously every 2 weeks for up to 12 months. The primary end-point was objective response rate; secondary end-points included progression-free survival (PFS) and overall survival (OS). RESULTS: Among evaluable patients (n = 111), objective response rate was 16.2% (95% confidence interval [CI], 9.9-24.4); 29.4% (95% CI, 15.1-47.5) for human papillomavirus (HPV)-positive patients and 10.9% (95% CI, 4.5-21.3) for HPV-negative patients. Median PFS and OS for treated patients (n = 112) was 2.1 months (95% CI, 1.9-3.7) and 7.1 months (95% CI, 4.9-9.9); PFS and OS at 12 months were 14.6% (95% CI, 8.5-22.1) and 33.6% (95% CI, 24.8-42.7). Treatment-related adverse events were 57.1% (any grade) and 8.0% (grade ≥3); none led to death. At data cut-off, 24.1% of patients remained on treatment or in follow-up. CONCLUSION: Durvalumab demonstrated antitumour activity with acceptable safety in PD-L1-high patients with R/M HNSCC, supporting its ongoing evaluation in phase III trials in first- and second-line settings. In an ad hoc analysis, HPV-positive patients had a numerically higher response rate and survival than HPV-negative patients.

Overall Survival with Durvalumab after Chemoradiotherapy in Stage III NSCLC.

BACKGROUND: An earlier analysis in this phase 3 trial showed that durvalumab significantly prolonged progression-free survival, as compared with placebo, among patients with stage III, unresectable non-small-cell lung cancer (NSCLC) who did not have disease progression after concurrent chemoradiotherapy. Here we report the results for the second primary end point of overall survival. METHODS: We randomly assigned patients, in a 2:1 ratio, to receive durvalumab intravenously, at a dose of 10 mg per kilogram of body weight, or matching placebo every 2 weeks for up to 12 months. Randomization occurred 1 to 42 days after the patients had received chemoradiotherapy and was stratified according to age, sex, and smoking history. The primary end points were progression-free survival (as assessed by blinded independent central review) and overall survival. Secondary end points included the time to death or distant metastasis, the time to second progression, and safety. RESULTS: Of the 713 patients who underwent randomization, 709 received the assigned intervention (473 patients received durvalumab and 236 received placebo). As of March 22, 2018, the median follow-up was 25.2 months. The 24-month overall survival rate was 66.3% (95% confidence interval [CI], 61.7 to 70.4) in the durvalumab group, as compared with 55.6% (95% CI, 48.9 to 61.8) in the placebo group (two-sided P=0.005). Durvalumab significantly prolonged overall survival, as compared with placebo (stratified hazard ratio for death, 0.68; 99.73% CI, 0.47 to 0.997; P=0.0025). Updated analyses regarding progression-free survival were similar to those previously reported, with a median duration of 17.2 months in the durvalumab group and 5.6 months in the placebo group (stratified hazard ratio for disease progression or death, 0.51; 95% CI, 0.41 to 0.63). The median time to death or distant metastasis was 28.3 months in the durvalumab group and 16.2 months in the placebo group (stratified hazard ratio, 0.53; 95% CI, 0.41 to 0.68). A total of 30.5% of the patients in the durvalumab group and 26.1% of those in the placebo group had grade 3 or 4 adverse events of any cause; 15.4% and 9.8% of the patients, respectively, discontinued the trial regimen because of adverse events. CONCLUSIONS: Durvalumab therapy resulted in significantly longer overall survival than placebo. No new safety signals were identified. (Funded by AstraZeneca; PACIFIC ClinicalTrials.gov number, NCT02125461 .).

Durvalumab after Chemoradiotherapy in Stage III Non-Small-Cell Lung Cancer.

BACKGROUND: Most patients with locally advanced, unresectable, non-small-cell lung cancer (NSCLC) have disease progression despite definitive chemoradiotherapy (chemotherapy plus concurrent radiation therapy). This phase 3 study compared the anti-programmed death ligand 1 antibody durvalumab as consolidation therapy with placebo in patients with stage III NSCLC who did not have disease progression after two or more cycles of platinum-based chemoradiotherapy. METHODS: We randomly assigned patients, in a 2:1 ratio, to receive durvalumab (at a dose of 10 mg per kilogram of body weight intravenously) or placebo every 2 weeks for up to 12 months. The study drug was administered 1 to 42 days after the patients had received chemoradiotherapy. The coprimary end points were progression-free survival (as assessed by means of blinded independent central review) and overall survival (unplanned for the interim analysis). Secondary end points included 12-month and 18-month progression-free survival rates, the objective response rate, the duration of response, the time to death or distant metastasis, and safety. RESULTS: Of 713 patients who underwent randomization, 709 received consolidation therapy (473 received durvalumab and 236 received placebo). The median progression-free survival from randomization was 16.8 months (95% confidence interval [CI], 13.0 to 18.1) with durvalumab versus 5.6 months (95% CI, 4.6 to 7.8) with placebo (stratified hazard ratio for disease progression or death, 0.52; 95% CI, 0.42 to 0.65; P<0.001); the 12-month progression-free survival rate was 55.9% versus 35.3%, and the 18-month progression-free survival rate was 44.2% versus 27.0%. The response rate was higher with durvalumab than with placebo (28.4% vs. 16.0%; P<0.001), and the median duration of response was longer (72.8% vs. 46.8% of the patients had an ongoing response at 18 months). The median time to death or distant metastasis was longer with durvalumab than with placebo (23.2 months vs. 14.6 months; P<0.001). Grade 3 or 4 adverse events occurred in 29.9% of the patients who received durvalumab and 26.1% of those who received placebo; the most common adverse event of grade 3 or 4 was pneumonia (4.4% and 3.8%, respectively). A total of 15.4% of patients in the durvalumab group and 9.8% of those in the placebo group discontinued the study drug because of adverse events. CONCLUSIONS: Progression-free survival was significantly longer with durvalumab than with placebo. The secondary end points also favored durvalumab, and safety was similar between the groups. (Funded by AstraZeneca; PACIFIC ClinicalTrials.gov number, NCT02125461 .).

NADPH oxidase 1 supports proliferation of colon cancer cells by modulating reactive oxygen species-dependent signal transduction.

Reactive oxygen species (ROS) play a critical role in cell signaling and proliferation. NADPH oxidase 1 (NOX1), a membrane-bound flavin dehydrogenase that generates O2̇̄, is highly expressed in colon cancer. To investigate the role that NOX1 plays in colon cancer growth, we used shRNA to decrease NOX1 expression stably in HT-29 human colon cancer cells. The 80-90% decrease in NOX1 expression achieved by RNAi produced a significant decline in ROS production and a G1/S block that translated into a 2-3-fold increase in tumor cell doubling time without increased apoptosis. The block at the G1/S checkpoint was associated with a significant decrease in cyclin D1 expression and profound inhibition of mitogen-activated protein kinase (MAPK) signaling. Decreased steady-state MAPK phosphorylation occurred concomitant with a significant increase in protein phosphatase activity for two colon cancer cell lines in which NOX1 expression was knocked down by RNAi. Diminished NOX1 expression also contributed to decreased growth, blood vessel density, and VEGF and hypoxia-inducible factor 1α (HIF-1α) expression in HT-29 xenografts initiated from NOX1 knockdown cells. Microarray analysis, supplemented by real-time PCR and Western blotting, revealed that the expression of critical regulators of cell proliferation and angiogenesis, including c-MYC, c-MYB, and VEGF, were down-regulated in association with a decline in hypoxic HIF-1α protein expression downstream of silenced NOX1 in both colon cancer cell lines and xenografts. These studies suggest a role for NOX1 in maintaining the proliferative phenotype of some colon cancers and the potential of NOX1 as a therapeutic target in this disease.

Human monocytes undergo functional re-programming during sepsis mediated by hypoxia-inducible factor-1α.

Sepsis is characterized by a dysregulated inflammatory response to infection. Despite studies in mice, the cellular and molecular basis of human sepsis remains unclear and effective therapies are lacking. Blood monocytes serve as the first line of host defense and are equipped to recognize and respond to infection by triggering an immune-inflammatory response. However, the response of these cells in human sepsis and their contribution to sepsis pathogenesis is poorly understood. To investigate this, we performed a transcriptomic, functional, and mechanistic analysis of blood monocytes from patients during sepsis and after recovery. Our results revealed the functional plasticity of monocytes during human sepsis, wherein they transited from a pro-inflammatory to an immunosuppressive phenotype, while enhancing protective functions like phagocytosis, anti-microbial activity, and tissue remodeling. Mechanistically, hypoxia inducible factor-1α (HIF1α) mediated this functional re-programming of monocytes, revealing a potential mechanism for their therapeutic targeting to regulate human sepsis.

A phase I and pharmacokinetic study of oral perifosine with different loading schedules in patients with refractory neoplasms.

PURPOSE: To determine the maximum tolerated dose (MTD) of perifosine (NSC 639966), an alkylphospholipid modulator of signal transduction, using different oral loading and maintenance regimens in an effort to avoid gastrointestinal toxicity while seeking maximal sustained plasma concentrations. METHODS: Thirty-one patients with advanced neoplasms were treated with monthly cycles of perifosine loading doses of 300, 600, 900, 1,200 and 1,500 mg (dose levels 1 through 5, respectively) on days 1-2 depending on the actual dose of the initial cycle. For subsequent cycles, perifosine loading doses were reduced to 100, 200, 300, 400 and 1,000 mg at the respective corresponding dose levels. Daily perifosine "maintenance" doses of 50, 100, 150, 200 and 250 mg for levels 1 through 5, respectively, commenced on days 2 or 3 and continued for a total of 21 days. No treatment was given for days 22-27. The pharmacokinetics of perifosine with these schedules was characterized. RESULTS: Dose-limiting diarrhea developed at or above dose level 4. The MTD and recommended phase II dose was dose level 3B, with a loading dose of 900 mg on day 1 divided into two doses of 450 mg administered 6 h apart and a maintenance dose of 150 mg on day 2 through 21. On subsequent cycles, the loading dose was reduced to 300 mg. Non-gastrointestinal toxicities included three episodes of gout or gout-like syndromes observed at doses above the MTD. The median peak plasma concentration of perifosine achieved at the MTD was approximately 8.3 µg/mL. Four patients had stable disease ranging from 167 to 735 days. CONCLUSIONS: Perifosine given according to a loading and maintenance schedule can safely sustain concentrations of drug, approaching concentrations achieved in preclinical models with evidence of anti-tumor effect.

HIF factors cooperate with PML-RARα to promote acute promyelocytic leukemia progression and relapse.

Acute promyelocytic leukemia (APL) is epitomized by the chromosomal translocation t(15;17) and the resulting oncogenic fusion protein PML-RARα. Although acting primarily as a transcriptional repressor, PML-RARα can also exert functions of transcriptional co-activation. Here, we find that PML-RARα stimulates transcription driven by HIF factors, which are critical regulators of adaptive responses to hypoxia and stem cell maintenance. Consistently, HIF-related gene signatures are upregulated in leukemic promyelocytes from APL patients compared to normal promyelocytes. Through in vitro and in vivo studies, we find that PML-RARα exploits a number of HIF-1α-regulated pro-leukemogenic functions that include cell migration, bone marrow (BM) neo-angiogenesis and self-renewal of APL blasts. Furthermore, HIF-1α levels increase upon treatment of APL cells with all-trans retinoic acid (ATRA). As a consequence, inhibiting HIF-1α in APL mouse models delays leukemia progression and exquisitely synergizes with ATRA to eliminate leukemia-initiating cells (LICs).

Weekly EZN-2208 (PEGylated SN-38) in combination with bevacizumab in patients with refractory solid tumors.

BACKGROUND: Anti-angiogenic therapies such as bevacizumab upregulate hypoxia-inducible factor-1α (HIF-1α), a possible mechanism of drug resistance. Camptothecin analogues, including SN-38, have been shown to reduce the expression and transcriptional activity of HIF-1α in preclinical models. We hypothesized that co-administration of pegylated SN-38 (EZN-2208) may offset the induction of HIF-1α following bevacizumab treatment, resulting in synergistic antitumor effects. PATIENTS AND METHODS: Patients with refractory solid tumors were enrolled. Objectives were to evaluate the modulation of HIF-1α protein and target genes in tumor biopsies following administration of the combination of EZN-2208 administered weekly × 3 (days 1, 8, 15) and bevacizumab administered every 2 weeks, in 28-day cycles, and to establish the safety and tolerability of the combination. Tumor biopsies and dynamic contrast enhanced MRI (DCE-MRI) were obtained following bevacizumab alone (before EZN-2208) and after administration of both study drugs. RESULTS: Twelve patients were enrolled; ten were evaluable for response. Prolonged stable disease was observed in 2 patients, one with HCC (16 cycles) and another with desmoplastic round cell tumor (7 cycles). Reduction in HIF-1α protein levels in tumor biopsies compared to baseline was observed in 5 of 7 patients. Quantitative analysis of DCE-MRI from 2 patients revealed changes in K(trans) and k(ep). The study closed prematurely as further clinical development of EZN-2208 was suspended by the pharmaceutical sponsor. CONCLUSION: Preliminary proof-of-concept for modulation of HIF-1α protein in tumor biopsies following administration of EZN-2208 was observed. Two of 10 patients had prolonged disease stabilization following treatment with the EZN-2208 and bevacizumab combination.

Pilot trial of EZN-2968, an antisense oligonucleotide inhibitor of hypoxia-inducible factor-1 alpha (HIF-1α), in patients with refractory solid tumors.

PURPOSE: Hypoxia-inducible factor-1 (HIF-1) facilitates the adaptation of normal and tumor tissues to oxygen deprivation. HIF-1 is frequently overexpressed in cancer cells, where it is involved in the upregulation of many genes necessary for survival. EZN-2968 is an antisense oligodeoxynucleotide that specifically targets HIF-1α, one of the subunits of HIF-1. We conducted a trial of EZN-2968 in patients with refractory solid tumors to evaluate antitumor response and to measure modulation of HIF-1α mRNA and protein levels as well as HIF-1 target genes. METHODS: Adult patients with refractory advanced solid tumors were administered EZN-2968 as a 2-h IV infusion at a dose of 18 mg/kg once a week for three consecutive weeks followed by 3-week off; in a 6-week cycle. Tumor biopsies and dynamic contrast enhanced MRI (DCE-MRI) were performed at baseline and after the third dose. RESULTS: Ten patients were enrolled, of whom all were evaluable for response; one patient with a duodenal neuroendocrine tumor had prolonged stabilization of disease (24 weeks). Reduction in HIF-1α mRNA levels compared to baseline was demonstrated in 4 of 6 patients with paired tumor biopsies. Reductions in levels of HIF-1α protein and mRNA levels of some target genes were observed in two patients. Quantitative analysis of DCE-MRI from two patients revealed changes in K (trans) and k ep. The trial was closed prematurely when the sponsor suspended development of this agent. CONCLUSION: This trial provides preliminary proof of concept for modulation of HIF-1α mRNA and protein expression and target genes in tumor biopsies following the administration of EZN-2968.

Autocrine production of IL-11 mediates tumorigenicity in hypoxic cancer cells.

IL-11 and its receptor, IL-11Ra, are expressed in human cancers; however, the functional role of IL-11 in tumor progression is not known. We found that IL11 is a hypoxia-inducible, VHL-regulated gene in human cancer cells and that expression of IL11 mRNA was dependent, at least in part, on HIF-1. A cooperative interaction between HIF-1 and AP-1 mediated transcriptional activation of the IL11 promoter. Additionally, we found that human cancer cells expressed a functional IL-11Ra subunit, which triggered signal transduction either by exogenous recombinant human IL-11 or by autocrine production of IL-11 in cells cultured under hypoxic conditions. Silencing of IL11 dramatically abrogated the ability of hypoxia to increase anchorage-independent growth and significantly reduced tumor growth in xenograft models. Notably, these results were phenocopied by partial knockdown of STAT1 in a human prostate cancer cell line (PC3), suggesting that this pathway may play an important role in mediating the effects of IL-11 under hypoxic conditions. In conclusion, these results identify IL11 as an oxygen- and VHL-regulated gene and provide evidence of a pathway "hijacked" by hypoxic cancer cells that may contribute to tumor progression.

Role of the VEGF/VEGFR axis in cancer biology and therapy.

New vessel formation (angiogenesis) is an essential physiological process for embryologic development, normal growth, and tissue repair. Angiogenesis is tightly regulated at the molecular level; however, this process is dysregulated in several pathological conditions such as cancer. The imbalance between pro- and antiangiogenic signaling molecules within tumors creates an abnormal vascular network that is characterized by dilated, tortuous, and leaky vessels. The pathophysiological consequences of these vascular abnormalities include temporal and spatial heterogeneity in tumor blood flow, oxygenation, and increased tumor interstitial fluid pressure. The resultant microenvironment deeply impacts on tumor progression, and also leads to a reduction in therapy efficacy. The discovery of vascular endothelial growth factor (VEGF) as a major driver of tumor angiogenesis has led to efforts to develop novel therapeutics aimed at inhibiting its activity. Anti-VEGF therapy has become an important option for the management of several human malignancies; however, a significant number of patients do not respond to anti-VEGF therapy when used either as single agent or in combination with chemotherapy. In addition, the benefit of antiangiogenic therapy is relatively short lived and the majority of patients relapse and progress. An increasing amount of reports suggest several potential mechanisms of resistance to antiangiogenic therapy including, but not limited to, tumor hypoxia. This chapter discusses the role of the VEGF axis in tumor biology and highlights the clinical application of anti-VEGF therapies elaborating on pitfalls and strategies to improve clinical outcome.

Overcoming disappointing results with antiangiogenic therapy by targeting hypoxia.

Cancer cells rely on angiogenesis to fulfil their need for oxygen and nutrients; hence, agents targeting angiogenic pathways and mediators have been investigated as potential cancer drugs. Although this strategy has demonstrated delayed tumour progression--leading to progression-free survival and overall survival benefits compared with standard therapy--in some patients, the results are more modest than predicted. A significant number of patients either do not respond to antiangiogenic agents or fairly rapidly develop resistance to them, which raises questions about how resistance develops and how it can be overcome. Furthermore, whether cancers, once they develop resistance, become more invasive or lead to metastatic disease remains unclear. Several mechanisms of resistance have been recently proposed and emerging evidence indicates that, under certain experimental conditions, antiangiogenic agents increase intratumour hypoxia by promoting vessel pruning and inhibiting neoangiogenesis. Indeed, several studies have highlighted the possibility that inhibitors of VEGF (and its receptors) can promote an invasive metastatic switch, in part by creating an increasingly hypoxic tumour microenvironment. As a potential remedy, a number of therapeutic approaches have been investigated that target the hypoxic tumour compartment to improve the clinical outcome of antiangiogenic therapy.

Phase I study of PARP inhibitor ABT-888 in combination with topotecan in adults with refractory solid tumors and lymphomas.

A phase I trial of ABT-888 (veliparib), a PARP inhibitor, in combination with topotecan, a topoisomerase I-targeted agent, was carried out to determine maximum tolerated dose (MTD), safety, pharmacokinetics, and pharmacodynamics of the combination in patients with refractory solid tumors and lymphomas. Varying schedules and doses of intravenous topotecan in combination with ABT-888 (10 mg) administered orally twice a day (BID) were evaluated. Plasma and urine pharmacokinetics were assessed and levels of poly(ADP-ribose) (PAR) and the DNA damage marker γH2AX were measured in tumor and peripheral blood mononuclear cells (PBMC). Twenty-four patients were enrolled. Significant myelosuppression limited the ability to coadminister ABT-888 with standard doses of topotecan, necessitating dose reductions. Preclinical studies using athymic mice carrying human tumor xenografts also informed schedule changes. The MTD was established as topotecan 0.6 mg/m²/d and ABT-888 10 mg BID on days one to five of 21-day cycles. Topotecan did not alter the pharmacokinetics of ABT-888. A more than 75% reduction in PAR levels was observed in 3 paired tumor biopsy samples; a greater than 50% reduction was observed in PBMCs from 19 of 23 patients with measurable levels. Increases in γH2AX response in circulating tumor cells (CTC) and PBMCs were observed in patients receiving ABT-888 with topotecan. We show a mechanistic interaction of a PARP inhibitor, ABT-888, with a topoisomerase I inhibitor, topotecan, in PBMCs, tumor, and CTCs. Results of this trial reveal that PARP inhibition can modulate the capacity to repair topoisomerase I-mediated DNA damage in the clinic.

Multihistology, target-driven pilot trial of oral topotecan as an inhibitor of hypoxia-inducible factor-1α in advanced solid tumors.

PURPOSE: Hypoxia-inducible factor 1 (HIF-1) α is frequently overexpressed in human tumors and is associated with angiogenesis and metastasis. Topotecan, a topoisomerase I inhibitor, has been shown to inhibit HIF-1α expression in preclinical models. We designed a pilot trial to measure HIF-1α inhibition in tumor biopsies from patients with advanced solid tumors overexpressing HIF-1α, after treatment with oral topotecan. EXPERIMENTAL DESIGN: Topotecan was administered orally at 1.6 mg/m(2) once daily for 5 days/week for 2 weeks, in 28-day cycles. Objectives were to determine inhibition of expression of HIF-1α and HIF-1 target genes in tumor; to assess tumor blood flow by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI); and to measure pharmacokinetics. Tumor biopsies were collected at baseline and during the second cycle of treatment. RESULTS: Sixteen patients were enrolled. The dose of topotecan was reduced to 1.2 mg/m(2)/day due to myelosuppression. Seven patients had paired tumor biopsies. In 4 patients, HIF-1α nuclear staining became undetectable after treatment (7.5%-50% staining at baseline). Decreased levels of VEGF and GLUT-1 mRNA were measured in 4 patients; the changes were concordant with reduction in HIF-1α in 3 patients. Decreased tumor blood flow and permeability were observed by DCE-MRI in 7 of 10 patients after 1 cycle. One patient had a partial response accompanied by inhibition of HIF-1α in tumor and reduction in tumor blood flow on DCE-MRI. CONCLUSIONS: This multihistology, target assessment trial of a small molecule inhibitor of HIF-1α showed that topotecan could decrease HIF-1α expression in advanced solid tumors.

Hypoxia: jump-starting inflammation.

Tissue hypoxia affects immunity and inflammation; however, the way in which changes in oxygen levels may modulate dendritic cell (DC) function is still not clear. Bosco et al report the gene expression profiling of hypoxic mature DCs and identify TREM-1 as a novel hypoxia-inducible gene that may amplify inflammatory responses.